CROSS-REFERENCE TO RELATED PATENT APPLICATIONS
FIELD OF THE INVENTION
This application is a continuation-in-part of International Application No. PCT/BE2008/000052 filed Jul. 7, 2008, which claims the benefit of G.B. Application No. 0713250.9 filed Jul. 9, 2007, G.B. Application No. 0724442.9 filed Dec. 14, 2007, G.B. Application No. 0802265.9 filed Feb. 7, 2008, G.B. Application No. 0802400.2 filed Feb. 11, 2008 and G.B. Application No. 0803185.8 filed Feb. 21, 2008, which documents are all incorporated by reference.
- BACKGROUND OF THE INVENTION
The present invention concerns materials with data-storage capabilities comprising emissive material of confined metal oligo-atomic clusters in molecular sieves, such as zeolites.
In recent years, expertise has been gained in the synthesis of zeolites with desired properties by the choice of the structure directing agent (SDA), control of the synthesis conditions, and post-synthesis treatments [see van Bekkum, H. et al. (editors) Introduction to Zeolite Science and Practice, 2nd edition; Studies in Surface Science and Catalysis, 2001, 137; Corma, A., Chem. Rev., 1997, volume 97, 2373-2419; Davis, M. E., Nature, 2002, volume 417, 813-821; Davis, M. E., et al., Chem. Mater., 1992, volume 4, 756-768; de Moor P-P. E. A. et al., Chem. Eur. J., 1999, volume 5(7), 2083-2088; Galo, J. de A. A., et al., Chew. Rev., 2002, volume 102, 4093-4138]. At the same time, the family of ordered mesoporous materials has been greatly expanded by the use of different surfactants and synthesis conditions [see Corma, A., Chem. Rev., 1997, volume 97, 2373-2419; Davis, M. E., Nature, 2002, volume 417, 813-821; Galo, J. de A. A., et al., Chem. Rev., 2002, volume 102, 4093-4138; Ying, J. Y., et al., Angew. Chem. Int. Ed., 1999, volume 35, 56-77]. The use of the appropriate template enables the control of the pore size, distribution and connectivity during the zeolite synthesis. For example, use of surfactants such as cetyltri-methylammonium bromide or dodecyltrimethylammonium bromide generally results in formation of mesoporous materials.
G. A. Ozin et al. in 1990 in “Inclusion Phenomena and Molecular Recognition”, edited by J. Atwood, Plenum Press, New York, pages 379-393, discloses the synthesis of a range of novel silver sodalites. These solid-state microstructures are viewed as “packaged” silver salts comprised of nanoassemblies of silver cations tetrahedrally organized with various charge balancing anions. Intercavity communication between entrapped silver microaggregates and expanded-metal superlattice ideas are considered briefly. The utilization of the silver sodalites in high resolution imaging/printing and high density write/read/erase data storage applications are also considered.
A Stein et al. in 1990 in J. Photogr. Sci. Technol. Japan, volume 53, pages 322-328, proposes the use of silver-containing sodalites as novel materials for reversible optical data storage. Sodalites can be synthesized with a variety of cation, anion and framework compositions using simple hydrothermal and ion exchange methods. Silver sodalites exhibit unique optical absorption and luminescence properties which can be controlled by tuning the material composition and unit cells sizes. The optical characteristics of these materials can be selectively modified using photons, heat, X-rays, pressure or moisture. A system containing oxalate as internal reducing agent can be reversibly marked with a laser beam for many cycles. The composition, structure, silver distribution and optical features of this material are discussed in detail. A possible mechanism for the reversible changes of silver oxalate-sodalite involves electron transfer between two types of silver clusters occluded in the sodalite framework.
A. Stein et al. in 1993 in Proceedings of the 9th International Zeolite Conference, Montreal 1992, Eds. R. von Ballmoos et al., Butterworth-Heinemann, pages 93-125, discloses that sodalite is an ancient material with great potential for advanced applications. Recent research is reported concerning the assembly of novel nanostructures by encapsulating clusters consisting of the components of insulators, semiconductors and metals inside the framework aluminosilicate sodalite. This nanoporous host acts as a stabilizing dielectric matrix, capable of organizing single size and shape clusters in perfectly periodic arrays. An interesting variety of potential applications for such materials, and the related zeolite analogues, are reported such as nanoporous molecular electronic materials, molecular wires, chemical sensors, zeolite electrodes, nonlinear optical materials and high density data materials.
G. Schulz-Ekloff in 1991 discloses in “Zeolite Chemistry and Catalysis”, editors P. A. Jacobs et al., Elsevier Science Publishers, Amsterdam, pages 65-78, describes the preparation and characterization of zeolite-hosted materials, like metals, semiconductors or dyes. Potential applications are summarized e.g. in optical switching, microwave absorption, optical data storage, microsensor devices or dispersion electrolysis.
JP 61-061894A discloses an optical recording material constituted of a clathrate compound of silver halide and zeolite. The silver halide is basically not limited and may, for example, be at least one of AgCl, AgBr and AgI. Zeolite may, for example, be of the Na mordenite type, the NaX type of the BaY type. The amount of the silver halide used for forming the clathrate compound with zeolite is preferably not more than 30 wt %, since an amount of more than 30 wt % causes the clathrate compound to be formed with difficulty. A photosensitive recording material which is capable of being rewritten can be produced by using the clathrate compound.
EP 1873202A discloses a transparent zeolite-polymer hybrid material, comprising zeolite crystals dispersed in a polymer, wherein: i) the zeolite crystals have parallel channels and/or cavities inside the crystal and a crystal length pf 20 to 7000 nm; ii) the channels and/or cavities of the zeolite crystals contain guest molecules, clusters or ions; iii) the zeolite crystals are surface-coated with a polymerizable silane; iv) polymer A is a transparent organic polymer. EP 1873202A further discloses the use of such transparent zeolite-polymer hybrid materials for developing optical devices such as lenses, eye glasses, special mirrors, filters, polarizer, grids, optical storage, monitors, window panes, float glass, or for coating of organic and inorganic surfaces for anti-reflection properties or light wavelength transformation.
In contrast to bulk metals, which are devoid of a band gap, and hence are good electric conductors, small Au or Ag clusters display interesting emissive properties from discrete energy levels. This phenomenon has been demonstrated, e.g., for silver smaller than 100 atoms in rare gas matrices, in aqueous solutions and on silver oxide films.
The major problem in the study and creation of small Au or Ag clusters is aggregation to large nanoparticles and eventually to bulk metal, with loss of emission. Here, it is demonstrated that the use of porous structures with limited pore, cavity and tunnel sizes, overcomes the aggregation problem enabling emissive entities, which are stable in time.
For oxidized silver, such as silver oxide nanoparticles, it has been shown that reduction to metallic silver is possible by the irradiation with UV to visible light (Peyser, L. A., Vinson, A. E., Bartko, A. P., Dickson, R. M. (2001) Science 291, 103-106). This reduction causes a change in the optical properties of the material, however for such material the final outcome of the reduction reaction is hard to control and finally big non-emissive silver aggregates will have formed.
N. E. Bogdanchikova et al. in 1999 in Applied Surface Science 150, 58-64 showed that silver clusters in molecular sieves exhibit remarkable stability and that the stability of the silver clusters depends on the acid strength, which may be related to the composition, e.g., the SiO2/Al2O3 molar ratio, of the molecular sieves. Silver clusters in mordenites having weak acidic sites are stable for at least 50 months, a sufficiently long period with respect to the application in mind for use in a visible light source. Disappearance of the clusters was linked to oxidation.
The current state of the art has never suggested or demonstrated the room temperature conversion of invisible light, e.g., with energy in the UV region, to a lower energy, e.g., visible light, by oligo atomic metal clusters embedded in molecular sieves. Also the influence of light-irradiation on the optical properties of such materials have never been studied before.
Some technologies of the art concern the photophysical properties of zeolites loaded with silver. For instance, Chen et al. loaded Y zeolites with AgI, instead of silver clusters, and pumped or charged with 254 nm light, however, without observation or description of visible emission [W. Chen et al. Physical Review B 65, 245404 Artn 245404 (2002), U.S. Pat. No. 7,067,072 and U.S. Pat. No. 7,126,136]. Calzaferri et al. in 2003 in Chemical Society Reviews, volume 32, pages 29-37, demonstrated absorption of 254 nm light by silver metal containing zeolites without reporting any emission. Kanan et al. in 2003 in Research on Chemical Intermediates, volume 29, pages 691-704, showed some emission intensity for silver(I)-exchanged zeolite Y, however only when excited at temperatures below 200 K.
- SUMMARY OF THE INVENTION
Encoded microcarriers are a key element in multiplex (bio)assays in which multiple independent reactions are investigated in the same solution, and in high throughput split-and-mix synthesis methods for creating large libraries of compounds from a set of common building blocks. In a typical multiplex assay, each target is attached to a host particle with a specific ‘barcode’. Generally this code is determined by the incorporation of different fluorescent tags in specific concentration ratios (optical encoding), and thus only a limited amount of unique codes is available. While these strategies rely on encoding of microcarriers in advance of the experiment (fixed encoding), a more flexible approach where the encoding occurs during the assay (active encoding) was recently worked out, based on spatial selective photobleaching.
The present invention solves problems of the related art by providing a material in which patterns such as bar codes can be written optically with very high lateral and spatial resolution using 2-photon excitation. Absorption of 2 photons only becomes probable in zones with extremely high illumination power and hence a high power near-infra red laser (we use a 780 nm laser) is required focused on the sample for a given time (in our case a few 10 ms to 1 second) to write fluorescent patterns. Mostly a pulsed laser is used in order to bundle all the intensity into short pulses. With 2-photon excitation a 1 μm resolution was surprisingly obtained in the Z-direction and a resolution of 450 nm in the xy-plane. Thus three layers of data can be written in a depth of 6 μm and these patterns are stable over extended periods of time.
The present invention relates generally to the enhancement of white light and colored light emission by photoactivation by UV to blue irradiation using confined oligo-atomic clusters, preferably silicon, silver, copper and gold, and more particularly to the use of molecular sieves comprising oligo atomic silver clusters as materials with data-storage and data imaging capabilities, for instance, for encoding labels such as bio-labels or tags or labels, for instance, for security items. Moreover, individual molecular sieve crystals comprising oligo-atomic clusters, e.g., silver clusters, can be used for active encoding of compounds based on photo-induced formation of fluorescent oligo-atomic clusters in a molecular sieve crystal host, which are compatible with an aqueous environment and exhibit extraordinary photostability.
The present invention demonstrates that oligo-atomic metal clusters confined in molecular sieves not only exhibit remarkable stability but also can be used for storing optical data. It has, for instance, been demonstrated that a first time radiation of such molecular sieve unit with UV or visible light will irreversibly enhance the light emission by that unit upon a second UV or visible light excitation or by subjecting it to a current or electrical field. A matrix or carrier containing several such excitable molecular sieve units can be used in a write radiation and read radiation system that allows the storage of optical information and which can be used for bit data storage or as an optical information imager that can be used to visualize stored optical information in an image. Irreversibly enhanced for the present application means that a first time excitation of oligo-atomic metal clusters confined in a molecular sieve by a radiation source (such UV or visible light radiation) will enhance the emission by that molecular sieve unit after a second radiation by UV or visible light in a stable or even irreversible manner such that an observable difference between an unwritten and written zone can be visualized. The written zone will upon activation emit more intensively.
Moreover, the materials of present invention, for instance, zeolites containing oligo silver atom clusters, are cheap and non-toxic. Zeolites, currently used in large quantities in washing powder and silver despite its antimicrobial properties, have no known toxic effect on human tissue. Colloidal silver has, for instance, widely been marketed as a dietary supplement for protective activity against oxidative stress and reactive oxygen species formation.
A particular advantage of the present invention is not only that the printed or coated images can comprise optical information as such which is invisible under ambient conditions but that additional optical information can be added to or written in the image, for instance, by defined UV radiation.
A further particular advantage of the present invention is the extraordinary photostability of the oligo-atomic metal clusters in molecular sieve crystals for multiplex (bio)assay applications over the organic dye-loaded latex spheres used in the photobleaching-based method.
An additional particular advantage of the present invention is the high resolution obtained with 2-photon activation of the oligo-atomic metal clusters in molecular sieve crystals for multiplex (bio)assay applications allowing for the creation of several layers of advanced matrix codes such as the 2D MaxiCodes and QR-codes inside an individual molecular sieve crystal.
An additional particular advantage over the photobleaching approach in respect of multiplex (bio)assay applications is that, since a dark pattern is written in a big fluorescent volume, the activated patterns have a positive contrast and are thus easily recognizable.
In accordance with the purpose of the invention, as embodied and broadly described herein, the invention is broadly drawn to data-storage material comprising an assembly of oligo-atomic clusters of metals confined in molecular sieves, preferably zeolites, for converting invisible radiation emitted by a radiation source at or above room temperature to visible light and for enhancing the emission intensity upon irradiation with UV or visible light.
Aspects of the present invention are realized by a method of storing data in oligo-atomic metal clusters confined in molecular sieves comprising the step of data-wise exposing said oligo-atomic metal clusters confined in molecular sieves to UV or visible light excitation, thereby providing stored data capable of being read as visible light emission upon exposure to UV-light or an electrical field at or above room temperature.
Aspects of the present invention are also realized by a paint, gelling liquid or elastomer comprising molecular sieves with oligo atomic silver clusters confined therein for forming optical data storage membranes or optical data storage films or for coating surfaces with a data-storage capable layer.
Aspects of the present invention are also realized by the use of molecular sieves with oligo atomic silver clusters confined therein as 3D encodable microcarriers in multiplex (bio) assays.
BRIEF DESCRIPTION OF THE DRAWINGS
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.
FIG. 1: Graph of the emission intensity originating from an individual silver-exchanged zeolite crystal versus time upon excitation with 375 nm picoseconds pulsed light with average power of 48 W/cm2 in confocal mode.
FIG. 2: Scheme of the photoactivation of specific patterns in an individual silver-exchanged zeolite crystal in order to generate bar codes.
FIG. 3 displays a Data Storage Medium (DSM) with the data-storage capable porous structures (DSCPS) which are an assembly of oligo atomic metal clusters confined in ordered porous oxides embedded in a matrix.
- a) False color emission image of a single silver-exchanged zeolite A crystal before photo-activation (1) and after consecutive activation of three individual spots (2, 3 and 4) in one crystal by irradiation with a ps 375 nm laser at 10 W/Cm2 for 20 minutes for each spot through a confocal microscope.
- b) Total activation of a single crystal. (1) shows the crystal before activation. After 5 min of irradiation by a 16.7 kW/cm2 pulsed 375 nm beam the intensity increased by a factor 10 (2). Another 20 minutes of activation at the same power yielded a total intensity increase of a factor 20. Note the increased scaling range from (1) to (3). The images in a) and b) were taken by a confocal microscope under irradiation by a 375 nm pulsed excitation source of respectively 10 and 20 W/cm2, with 2 ms integration time per pixel.
- c) True color image taken with a digital camera (Canon PowerShot A710 IS with a 400 nm longpass filter in front of the lens to filter out the excitation light) through the eye piece of the microscope showing the green emission from the same zeolite after complete activation at 16.7 kW/cm2 excitation power.
FIG. 5: Emission spectrum of the electroluminescence of thermally treated silver-exchanged 3A zeolite dispersed in PVK with Ytterbium and ITO electrodes.
: 2-photon activation of silver-exchanged zeolite A.
- a) Fluorescence microscope image of a silver zeolite in which the pattern of a lion was activated by 2-photon excitation.
- b) Template image for writing the lion pattern in the silver zeolites.
- c) black curve: Fluorescence intensity profile along the white dashed line of the written image in panel a. grey curve: Fluorescence intensity profile along the grey dashed line of the template image in panel b.
- d) Fluorescence microscope image of a silver zeolite in which three thin bar patterns of varying sizes are activated by 2-photon excitation.
- e) Fluorescence intensity profile along the x-axis of the area indicated by the dashed rectangle in panel d. The profile is averaged over the height of the dashed rectangle in panel d. The solid line represents a Gaussian multipeak fit to the data. All of the scaling bars represent a distance of 5 μm.
: Writing 3D structures in silver zeolites.
- a) Confocal optical sections throughout an individual silver zeolite crystal in which the letters “K”, “U” and “L” are photoactivated on top of each other as indicated in the upper left scheme by 2-photon excitation.
- b) Confocal optical section through the same crystal as in panel a, after flipping the crystal on its side. The orientation of this section is indicated in the upper left scheme in panel a by the dotted rectangle.
- c) Fluorescence intensity line profile along the area between the dashed lines in panel b. The solid line represents a Gaussian fit to the data to estimate the FWHM. All of the scaling bars represent a distance of 5 μm.
FIG. 8: 3D holographic structure. After photoactivation of a 3D spiral-shaped structure in an individual silver zeolite A crystal, confocal optical sections were imaged every 250 nm along the axial dimension using 488 nm excitation. The image shows a three-dimensional reconstruction of the activated volume.
FIG. 9: Fluorescence intensity-time transient for an activated silver zeolite crystal after photoactivation on the Fluo View 500 system using 1-photon excitation at 375 nm.
DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION
: Fluorescence intensity image of an
- activated silver zeolite crystal imaged at 499 nm. Left side panel shows fluorescence intensity image with the contours of the crystal indicated by the dashed white lines. Right side panel shows the transmission image overlaid.
The present invention will be described with respect to particular embodiments and with reference to certain drawings but the invention is not limited thereto but only by the claims. The drawings described are only schematic and are non-limiting. In the drawings, the size of some of the elements may be exaggerated and not drawn to scale for illustrative purposes. The dimensions and the relative dimensions do not correspond to actual reductions to practice of the invention.
Furthermore, the terms first, second, third and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other sequences than described or illustrated herein.
Moreover, the terms top, bottom, over, under and the like in the description and the claims are used for descriptive purposes and not necessarily for describing relative positions. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other orientations than described or illustrated herein.
It is to be noticed that the term “comprising”, used in the claims, should not be interpreted as being restricted to the means listed thereafter; it doe not exclude other elements or steps. It is thus to be interpreted as specifying the presence of the stated features, integers, steps or components as referred to, but does not preclude the presence or addition of one or more other features, integers, steps or components, or groups thereof. Thus, the scope of the expression “a device comprising means A and B” should not be limited to the devices consisting only of components A and B. It means that with respect to the present invention, the only relevant components of the device are A and B.
The articles “a” and “an” are used herein to refer to one or more than one (i.e., at least one) of the grammatical object of the article. By way of example, “an element” means one element or more than one element.
The term “including” is used to mean “including but not limited to”. “Including” and “including but not limited to” are used interchangeably.
The term “in particular” is used to mean “in particular but not limited thereto” and the term “particularly” is used to mean “particularly but not limited thereto”.
Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment, but may. Furthermore, the particular features, structures or characteristics may be combined in any suitable manner, as would be apparent to one of ordinary skill in the art from this disclosure, in one or more embodiments.
Similarly it should be appreciated that in the description of exemplary embodiments of the invention, various features of the invention are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure and aiding the understanding of one or more of the various inventive aspects. This method of disclosure, however, is not to be interpreted as reflecting an intention that the claimed invention requires more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive aspects lie in less than all features of a single foregoing disclosed embodiment. Thus, the claims following the detailed description are hereby expressly incorporated into this detailed description, with each claim standing on its own as a separate embodiment of this invention.
Furthermore, while some embodiments described herein include some but not other features included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the invention, and form different embodiments, as would be understood by those in the art. For example, in the following claims, any of the claimed embodiments can be used in any combination.
In the description provided herein, numerous specific details are set forth. However, it is understood that embodiments of the invention may be practiced without these specific details. In other instances, well-known methods, structures and techniques have not been shown in detail in order not to obscure an understanding of this description.
Several documents are cited throughout the text of this specification. Each of the documents herein (including any manufacturer's specifications, instructions etc.) is hereby incorporated by reference; however, there is no admission that any document cited is indeed prior art of the present invention.
The following terms are provided solely to aid in the understanding of the invention.
The term “data storage”, as used in disclosing the present invention, means the possibility of creating certain patterns inside or on a material by locally changing the optical properties of this material with the possibility of reading the patterns using an electromagnetic probe beam or other reading means.
The term “molecular sieve”, as used in disclosing the present invention, means a solid with pores of the size of molecules.
The term “zeolite”, as used in disclosing the present invention, means any member of a group, of structured aluminosilicate minerals comprising cations such as sodium and calcium or, less commonly, barium, beryllium, lithium, potassium, magnesium and strontium; characterized by the ratio (Al+Si):O=approximately 1:2, an open tetrahedral framework structure capable of ion exchange, and loosely held water molecules, that allow reversible dehydration. The term “zeolite” also includes “zeolite-related materials” or “zeotypes” which are prepared by replacing Si4+ or Al3+ with other elements as in the case of aluminophosphates (e.g., MeAPO, SAPO, ElAPO, MeAPSO, and ElAPSO), gallophosphates, zincophophates, titanosilicates, etc. The zeolite can be a crystalline porous material with a frame work as described in Pure Appl. Chem., volume 73, No. 2, pp. 381-394, (2001) or provided in the Zeolite Framework Types database of the IZA structure commission where under the following structure types, as defined by the International Zeolite Association such as ABW type, ACO type, AEI type, AEL type, AEN type, AET type, AFG AFI type, AFN type, AFO type, AFR type, AFS type, AFT type, AFX type, AFY type, AHT type, ANA type, APC type, APD type, AST type, ASV type, ATN type, ATO type, ATS type, ATT type, ATV type, AWO type, AWW type, BCT type, BEA type, BEC type, BIK type, BOG type, BPH type, BRE type, CAN type, CAS type, CDO type, CFI type, CGF type, CGS type, CHA type, CHI type, CLO type, CON type, CZP type, DAC type, DDR type, DFO type, DFT type, DOH type, DON type, EAB type, EDI type, EMT type, EON type, EPI type, ERI type, ESV type, ETR type, EUO type, EZT type, FAR type, FAU type, FER type, FRA type, GIS type, GIU type, GME type, GON type, GOO type, HEU type, IFR type, IHW type, IMF type, ISV type, ITE type, ITH type, ITW type, IWR type, IWV type, IWW type, JBW type, KFI type, LAU type, LEV type, LIO type, LIT type, LOS type, LOV type, LTA type, LTL type, LTN type, MAR type, MAZ type, MEI type, MEL type, MEP type, MER type, MFI type, MFS type, MON type, MOR type, MOZ type, MSE type, MSO type, MTF type, MTN type, MTT type, MTW type, MWW type, NAB type, NAT type, NES type, NON type, NPO type, NSI type, OBW type, OFF type, OSI type, OSO type, OWE type, PAR type, PAU type, PHI type, PON type, RHO type, RON type, RRO type, RSN type, RTE type, RTH type, RUT type, RWR type, RWY type, SAO type, SAS type, SAT type, SAV type, SBE type, SBN type, SBS type, SBT type, SFE type, SFF type, SFG type, SFH type, SFN type, SFO type, SGT type, SIV type, SOD type, SOS type, SSF type, SSY type, STF type, STI type, STO type, STT type, SZR type, TER type, THO type, TOL type, TON type, TSC type, TUN type, UEI type, UFI type, UOZ type, USI type, UTL type, VET type, VFI type, VNI type, VSV type, WEI type, WEN type, YUG type and ZON type. The term “zeolite” also includes “zeolite-related materials” or “zeotypes” which are prepared by replacing Si4+ or Al3+ with other elements as in the case of aluminophosphates (e.g., MeAPO, AlPO, SAPO, ElAPO, MeAPSO, and ElAPSO), gallophosphates, zincophophates, titanosilicates, etc.
The term “macroporous material”, as used in disclosing the present invention, means a material having pore diameters of greater than 50 nm as laid down by IUPAC [see J. Rouquerol et al., Pure & Appl. Chem., volume 66 (1994) 1739-1758].
The term “mesoporous material”, as used in disclosing the present invention, means a material having pore diameters between 2 nm (20 Å) and 50 nm (500 Å) as laid down by IUPAC [see J. Rouquerol et al., Pure & Appl. Chem., volume 66 (1994) 1739-1758].
The term “microporous material”, as used in disclosing the present invention, means a material having pore diameters less than 2 nm [20 Angstrom (Å)] as laid down by IUPAC [see J. Rouquerol et al., Pure & Appl. Chem., volume 66 (1994) 1739-1758]. The term “microporous materials” includes amorphous microporous solids. Alternative amorphous microporous solids, which can be used in the present invention include amorphous microporous mixed oxides having, in dried form, a narrow pore size distribution (half width <±10% of the pore diameter) of micropores with diameters in the range of <2 nm and the preparation of said amorphous microporous mixed oxides have been well described in U.S. Pat. No. 6,121,187 and others have been well documented in WO 2001-44308A, U.S. Pat. No. 6,753,287, U.S. Pat. No. 6,855,304, U.S. Pat. No. 6,977,237, WO 2005-097679A, U.S. Pat. No. 7,055,756 and U.S. Pat. No. 7,132,093.
The term “microporous carrier” as used herein refers to a solid with pores the size of molecules. It includes but is not limited to microporous materials, ALPOs and (synthetic) zeolites, pillared or non-pillared clays, carbon molecular sieves, microporous titanosilicates such as ETS-10, and microporous oxides. Microporous carriers can have multimodal pore size distribution, also referred to as ordered ultramicropores (typically less than 0.7 nm) and supermicropores (typically in the range of about 0.7-2 nm). Particular types of microporous carriers envisaged within the present invention are the molecular sieve zeolites. Zeolites are the aluminosilicate members of the family of microporous carriers. The microporous carrier can be of an ordered crystalline structure or an amorphous material.
The term “room temperature” as used in this application means a temperature in the range of 12 to 30° C., preferably in the range of 16 to 28° C., more preferably in the range of 17 to 25° C. and most preferably is roughly 20 to 23° C.
The term “luminescence” or “emissive”, as used in disclosing the present invention, includes the following types: chemoluminescence, crystalloluminescence, electroluminescence, photoluminescence, phosphorescence, fluorescence, and thermo-luminescence.
The term “oligo-atomic metal cluster”, as used in disclosing the present invention, includes clusters ranging from 1 to 100 atoms of the following metals (sub-nanometer size), Si, Cu, Ag, Au, Ni, Pd, Pt, Rh, Co and Ir or alloys thereof such as Ag/Cu, Au/Ni etc. The clusters can be neutral, positive or negatively charged. If the clusters are positively charged, the negatively charged zeolite framework provides for charge compensation and hence no charge-compensating anions are required. The oligo atomic metal clusters can be small oligo atomic silver- (and/or gold) clusters containing 1 to 100 atoms.
2-photon excitation means that light of half the energy (or double the wavelength) is used to excite the sample.
The term “matrix”, as used in disclosing the present invention, means a solid medium upon which or in which the oligo-atomic metal clusters in a molecular sieve are situated, which is preferably transparent or semitransparent, and embraces any organic, inorganic or hybrid binding medium, with molecular sieves, polysiloxanes, polymers including polymer fibres, copolymers or elastomers being preferred.
A comprehensive list of the abbreviations utilized by organic chemists of ordinary skill in the art appears in the first issue of each volume of the Journal of Organic Chemistry; this list is typically presented in a table entitled Standard List of Abbreviations.
For purposes of this invention, the chemical elements are identified in accordance with the Periodic Table of the Elements, CAS version, Handbook of Chemistry and Physics, 67th Ed., 1986-87, inside cover. Contemplated equivalents of the zeolitic structures, subunits and other compositions described above include such materials which otherwise correspond thereto, and which have the same general properties thereof (e.g., biocompatible), wherein one or more simple variations of substituents are made which do not adversely affect the efficacy of such molecule to achieve its intended purpose. In general, the compounds of the present invention may be prepared by the methods illustrated in the general reaction schemes as, for example, described below, or by modifications thereof, using readily available starting materials, reagents and conventional synthesis procedures. In these reactions, it is also possible to make use of variants, which are in themselves known, but are not mentioned here:
- Method of Storing Data in Oligo-Atomic Metal Clusters Confined in Molecular Sieves
a) “the molecular sieve in which the oligo-atomic clusters are confined is selected from among microporous materials, selected from among zeolites, porous oxides, silicoaluminophosphates and aluminosilicates”.
b) “zeolite selected from among the family of small pore sized zeolites such as zeolite A and ZKF, and combinations thereof”.
c) “large pore zeolites such as ZSM-5, MCM-22, ferrierite, faujastites X and Y and microporous molecular sieves”.
d) “The matrix can also be a molecular sieve selected from among molecular sieves MCM-41, MCM-48, HSM, SBA-15, and combinations thereof”.
e) “Methods are available in the art for preparation of microporous zeolites.”
f) “As used herein, microporous zeolites preferably have a pore size of about 3 angstroms to about 14 angstroms”.
Aspects of the present invention are realized by a method of storing data in oligo-atomic metal clusters confined in molecular sieves comprising the step of data-wise exposing said oligo-atomic metal clusters confined in molecular sieves to UV or visible light excitation, thereby providing stored data capable of being read as visible light emission upon exposure to UV-light or an electrical field at or above room temperature.
Aspects of the present invention are also realized by a method of writing optical data in a pattern on the data storage medium of any of the previous claims comprising exposing locoregional portions of the material, with at least one assembly of small Au and/or Ag clusters confined in a molecular sieve particle, to radiation at a radiation power sufficient to cause such assembly which absorbs the radiation to emit light photons and of visualizing such stored optical data by reradiating them or by a larger portion of the materials with lower radiation power sufficient to only read the assemblies of small Au and/or Ag clusters confined in a molecular sieve which store the optical data.
According to a preferred embodiment of the method of storing data in oligo-atomic metal clusters confined in molecular sieves, according to the present invention, the data-wise exposure of said oligo-atomic metal clusters confined in molecular sieves is sufficiently intense or long to realize an enhanced excitation effect upon a next read at lower irradiation or illumination by UV or visible light radiation.
According to another preferred embodiment of the method of storing data in oligo-atomic metal clusters confined in molecular sieves, according to the present invention, the data-wise exposure of said oligo-atomic metal clusters confined in molecular sieves is sufficiently intense or long read illumination by radiation from a laser beam, a medium wavelength UV (UVC) radiation source, a Far UV (FUV), a vacuum UV (VUV) ray radiation source, an Extreme UV (EUV) or a deep UV (XUV) ray radiation source to provide an enhanced excitation effect upon a following illumination by an UV or visible light.
According to another preferred embodiment of the method of storing data in oligo-atomic metal clusters confined in molecular sieves, according to the present invention, the data-wise exposure to UV or visible light excitation is performed with a laser or a light-emitting diode.
According to a preferred embodiment of the method of storing data in oligo-atomic metal clusters confined in molecular sieves, according to the present invention, the data-wise exposure to UV or visible light excitation is 2-photon photoactivation.
- Data-Storage Capable Porous Structures
According to another preferred embodiment of the method of storing data in oligo-atomic metal clusters confined in molecular sieves, according to the present invention, the oligo-atomic metal clusters are confined in a single molecular sieve crystal, preferably a microporous crystal and particularly preferably a zeolite crystal.
The oligo-atomic metal clusters in the illumination system of present invention are preferably of noble metals from the group consisting of gold, silver, platinum, palladium, silicon and rhodium and particularly preferably of gold and/or silver. The size of the oligo-atomic metal cluster is preferably 1-100 atoms, the maximum cluster size providing luminescence being dependent upon the metal, e.g., 20-30 atoms in the case of gold and 20 atoms in the case of silver. In the case of gold clusters, clusters of 1 to 30 atoms are preferred and in the case of silver clusters, clusters of 1 to 20 atoms are preferred.
The molecular sieves in this invention are preferably microporous or mesoporous materials; particularly preferably zeolites, porous oxides, silicoalumino-phosphates, gallophosphates, zinco-phosphates, titanosilicates and aluminosilicates, or mixtures thereof; and especially preferably one or more selected from the group consisting of mordenite, ZSM-5, MCM-22, A-zeolite, L-zeolite, faujasites X and Y, ferrierite, chabazite type of zeolites, and mixtures of the foregoing zeolites. Preferred zeolites are selected from the group consisting of K-A (3A), Na-A (4A), Ca-A (5A), 13× and ZKF zeolites.
The pore size of molecular sieves can further be influenced by the nature of the templating molecules in the synthesis. The addition of swelling agents to the synthesis mixture can further affect the pore size of the resulting molecular sieve. Zeolites with different pore size have been well characterized and described by Martin David Foster in “Computational Studies of the Topologies and Properties of Zeolites”, The Royal Institution of Great Britain, Department of Chemistry, University College London, a thesis submitted for the degree of Doctor of Philosophy, London, January 2003.
In a particular embodiment of the present invention the data-storage material for storing optical data comprising oligo-atomic metal clusters confined in molecular sieves, the emission upon UV or visible light excitation is irreversibly enhanced by illumination with UV or visible light.
In one embodiment in the present invention, Au or Ag clusters are protected from oxidation due to encapsulation in the molecular sieves. Additionally, if required, an external coating of the material crystals or capping of the pore entrances can be used to further protect the occluded metal clusters.
In a particular embodiment of present invention the pores of the molecular sieves containing the small clusters of, e.g., Au and/or Ag are coated with a matrix, or are closed by stopper molecules.
To transfer the UV or visible radiation into more red-shifted light, the light system of present invention does not require the presence of charge compensating anions, such as oxalate, hydroxide, azide, carbonate, bicarbonate, sulfate, sulfite, chlorate, perchlorate, acetate and formate to be in charge association with the noble metals, such as the small metal clusters.
- Optical Data Information Carrier and Optical Data Display
FIG. 1 shows a graph of the emission intensity originating from an individual silver-exchanged zeolite crystal versus time upon excitation with 375 nm picoseconds pulsed light with average power of 48 W/cm2 in confocal mode. This same excitation sources causes the photoactivation of the emission.
An optical data information carrier and optical data display can be made of a system that comprises oligo-atomic metal clusters, e.g., of small Au, Ag and/or alloys thereof, confined in molecular sieves, which are comprised, e.g., embedded or integrated, in a matrix, e.g., a membrane or film. Such matrices may further comprise a particle binder.
Moreover such an optical data information carrier or optical data display system can comprise a laminate structure wherein there is a layer of oligo-atomic metal clusters confined in molecular sieves incorporated in a matrix, preferably a polymer matrix. Such a polymer matrix can form a protective structure that incorporates the oligo-atomic metal clusters confined in molecular sieves and protects them from deterioration by external factors and improves stability.
The above described film can be used to directly incorporate the metal clusters confined in molecular sieves in said film or can be used to shield or cover another layer of film which incorporates the metal clusters confined in molecular sieves to protect such second film from environmental factors.
Aspects of the present invention are realized by a data-storage medium for storing optical data, characterized in that the optical data-storage medium comprises as data storage material oligo-atomic metal clusters confined in molecular sieves which are embedded in a solid or flexible support, whereby the metal clusters if subjected at room temperature or above to invisible radiation or an electrical field in response emit visible light.
According to another preferred embodiment of the method of storing data in oligo-atomic metal clusters confined in molecular sieves, according to the present invention, the oligo-atomic metal clusters confined in a molecular sieve is embedded in a rigid or flexible material, said oligo-atomic metal clusters in a molecular sieve preferably forming a mono-particulate layer of molecular sieve particles in said rigid or flexible material; or the oligo-atomic metal clusters in a molecular sieve preferably being structured in multi-particulate layers of molecular sieve particles in said rigid or flexible material.
According to another preferred embodiment of the method of storing data in oligo-atomic metal clusters confined in molecular sieves, according to the present invention, the method further comprises the step of embedding the data-wise exposed oligo-atomic metal clusters in a molecular sieve in a rigid or flexible material.
- Elastomeric Polymers Suitable for Use in the Optical Data Information Carrier and Optical Data Display
FIG. 3 displays a Data Storage Medium (DSM) with the data-storage capable porous structures or DSCPS which are an assembly of oligo atomic metal clusters confined in ordered porous oxides, preferably microporous silica oxides embedded in a matrix, preferably a polymer, copolymer or elastomer matrix, which preferably is transparent or semitransparent.
Typical but not exclusive examples of such elastomeric polymers are polydimethylsiloxane (silicone rubber), polyisobutene (butyl rubber), polybutadiene, polychloroprene, polyisoprene, styrene-butadiene rubber, acrylonitrile-butadiene rubber (NBR), ethene-propene-diene-rubber (EPDM) and acrylonitrile-butadiene-styrene (ABS) (Murder, 1991). Such films or membranes of the molecular sieves comprising oligo atomic silver clusters; ordered mesoporous and/or microporous oxides comprising oligo atomic silver clusters or porous materials with nanometer dimension (0.3-10 nm) windows, channels and cavity architectures comprising oligo atomic silver clusters can be coated on a substrate.
The most important elastomers are polyisoprene [natural or synthetic rubber (IR)], polychloroprene [chloroprene rubber (CR)], butyl rubber (BR), styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber (NBR), ethene-propene-diene-rubber (EPDM), acrylonitrile-butadiene-styrene (ABS), chlorosulfonated polyethylene (CSM), I polyacrylate (polyacrylic rubber), polyurethane elastomers, polydimethylsiloxane (PDMS, sometimes more generally referred to as silicone rubber), fluorosilicones and polysulfides.
- Polymers Suitable for Use in the Optical Data Information Carrier and Optical Data Display
Following the ASTM (American Society for Testing and Materials) standards, ‘elastomers’ are defined as “macromolecular materials that return to approximately the initial dimensions and shape after substantial deformation by a weak stress and release of the stress”. Elastomers are sometimes also referred to as ‘rubbery materials’. A ‘rubber’ is defined as “a material that is capable of recovering from large deformations quickly and forcibly, and can be, or already is, modified to a state in which it is essentially insoluble (but can swell) in boiling solvent, such as benzene, toluene, methyl ethyl ketone, and ethanol/toluene azeotrope”.
The data storage or data imaging of present invention may need particular characteristics according to its environment or use a variety of alternatives polymers that provide design freedom which preparation protocols are available in the art to design complex shapes, to consolidate parts into fewer components, simplify production, to produce transparent and precolored components, to reduce part weight, to reduce noise when the data storage or data imaging means or element is moving, to have a reliable performance at elevated temperature, to have chemical resistance in harsh climates, to have the desired stiffness, strength and toughness, to have hydrolytic stability over time, to have electrical properties to have a desired physical appearance.
Such polymer layers comprise a polymerization product of an acryl-based vinyl monomer, an aromatic vinyl monomer, acrylonitrile-based vinyl monomer, chloride-based vinyl monomer, vinylstearate or vinylpropionate. Examples of the acryl-based vinyl monomer include one or more mixtures selected from the group consisting of triethylopropane triacrylate, tri(propylene glycol)diacrylate, penthaerithritol triacrylate, trimethylol-propane ethoxylate triacrylate, methyl methacrylate, tri(prop-ylene glycol)glycerolate diacrylate and vinylacrylate. Examples of the aromatic vinyl monomer include styrene and divinyl benzene. Examples of the chloride-based vinyl monomer include vinylidene chloride and vinylbenzyl chloride. The oligomer is one or more mixtures selected from the group consisting of urethane acrylate oligomer, acrylate oligomer, ether acrylate oligomer and epoxy acrylate oligomer. The polymerization of such a film can be initiated by a polymerization initiator Examples of the polymerization initiator include photo initiators selected from the group consisting of 1-hydroxy-cyclohexyl-phenyl-ketone (Irgacur® 907), 2-methyl-1[4-(methyl-thio)phenyl]-2-morpholino-propane-1-one (Irgacur® 184C), 1-hydroxy-2-methyl-1-phenyl-propane-1-one (Darocu® 1173), a mixed initiator (Irgacur® 500) of Irgacur® 184C and benzophenone, a mixed initiator (Irgacure 1000) of Irgacure 184C and Irgacur® 1173, 2-hydroxy-1-[4-(2-hydroxyethoxy)phenyl]-2-methyl-1-propan-one (Irgacure® 2959), methylbenzoylformate (Darocure MBF), α,α-dimethoxy-α-phenyl-acetophenone (Irgacur® 651), 2-benzyl-2-(dimethylamino)-1-[4-(4-morpholinyl)phenyl]-1-butanone (Irgacur® 369), a mixed initiator (Irgacur® 1300) of Irgacur® 369 and Irgacur® 651, diphenyl-(2,4,6-trimethylbenzoyl)-phosphine oxide (Darocur TPO), a mixed initiator (Darocur® 4265) of Darocur® TPO and Darocur® 1173, phosphine oxide, phenyl bis(2,4,6-trimethyl benzoyl) (Irgacure® 819), a mixed initiator (Irgacure 2005) of Irgacure 819 and Darocur® 1173, a mixed initiator (Irgacure® 2010) of Irgacure® 819 and Darocur® 1173, and a mixed initiator (Irgacure® 2020) of Irgacure® 819 and Darocur® 1173, bis(s-5-2,4-cyclopentadien-1-yl)bis[2,6-difluoro-3-(1H-pyrrol-1-yl)phenyl] titanium (Irgacure® 784), and a mixed initiator (HSP 188) containing benzophenene. Also, examples of the polymerization initiator include thermal initiators selected from the group consisting of benzoyl peroxide (BP), acetyl peroxide (AP), diauryl peroxide (DP), di-tert-butyl peroxide (t-BTP), cumyl hydroperoxide (CHP), hydrogen peroxide (HP), potassium peroxide (PP), 2,2′-azobis-isobutyronitrile (AIBN), azocompound, and silver alkyls. Further, the polymerization initiator may be initiators utilizing an oxidation-reduction reaction selected from the group consisting of persulfate (K2S2O8) and a redox initiator. Coating of the polymers on another layer or on a substrate is performed by spin coating, bar coating, printing, spreading or dipping. Such coating or printing can be done with the polymers that are mixed with the oligo-atomic metal clusters confined in molecular sieves. In the step of forming the encapsulation film, in order to cause a polymerization reaction of the organic solution, light may be irradiated or heat may be applied thereto. When forming film, a fluid comprising the oligo-atomic metal clusters confined in molecular sieves, a vinyl monomer, a polymerization initiator and an oligomer, can be polymerized, thereby enhancing adhesion and hardness of the encapsulation film and denseness of an encapsulation film surface.
Polymers that are suitable for incorporation of the data-storage capable porous structures of present invention are for instance Spire™ family of ultra polymers such as 1) KetaSpire® polyetheretherketone (PEEK) which is easy-to-mold ultra polymer offering outstanding chemical resistance and mechanical performance up to 300° C. (570° F.) or AvaSpire® modified PEEK, a PEEK-based formulations or 2) PrimoSpire® self-reinforced polyphenylene (SRP) known to be designable in a very stiff, strong unreinforced polymer with a remarkable combination of surface hardness, chemical resistance and inherent flame-retardant properties or 3) EpiSpire™, an high-temperature sulfone (HTS) known to be a transparent amorphous polymer with excellent creep resistance at temperatures up to 265° C. (510° F.) or 4) Torlon® polyamide-imide (PAI) with higher strength and stiffness that most thermoplastic up to 275° C. (525° F.) combined with superior resistance to chemicals, creep and wear. Other polymers that are suitable for incorporation of the data-storage capable porous structures of present invention are the family of amorphous sulfone polymers such as 1) Udel® PSU known to be designable into tough, transparent plastic with exceptional chemical resistance, good hydrolytic stability and an HDT of 345° F. (174° C.) or the 2) Mindel® modified polysulfone with superior electrical propertiesor 3) the Radel® R (PPSU) known to deliver a super-tough transparent plastic with an HDT of 405° F. (207° C.), excellent chemical resistance and the unique ability to be steam sterilized without significant loss of properties or 4) the Radel® A (PES) know to deliver a transparent plastic with a high HDT of 400° F. (204° C.) and good chemical resistance or the Acudel® modified PPSU. Other polymers that are suitable for incorporation of the data-storage capable porous structures of present invention are for instance the semi-crystalline aromatic polyamides such as for instance the Amodel® polyphthalamide (PPA) known to deliver a high-temperature nylon with exceptional mechanical properties, an HDT of 535° F. (280° C.), excellent chemical resistance and low moisture uptake or the Ixef® polyarylamide (PA MXD6) known to deliver aesthetic, structural specialty nylon that combines outstanding stiffness with exceptional surface appearance, plus low and slow water uptake, and great flow properties. Other polymers that are suitable for incorporation of the data-storage capable porous structures of present invention are for instance semi-crystalline polymers such as the Primef® polyphenylene sulfide (PPS) which delivers a high-flow, structural plastic with good temperature and chemical resistance as well as inherent flame retardant properties or the Xydar® liquid crystal polymer (LCP) known to deliver high-flow, high-temperature plastic with an HDT of 570° F. (300° C.), and extremely high chemical resistance. These are available with design and processing guides form Solvay Advanced Polymers.
- Inorganic/Organic Polysiloxane Hybrid Polymers for Use in the Optical Data Information Carrier and Optical Data Display
Polystyrene is a thermoplastic polymer that is particularly resistant to irradiation.
- Process for Manufacturing Data-Storage Capable Porous Structures
Inorganic/organic polysiloxane hybrid polymers are known in the art and described in High Performance Ceramic Films and Coatings (Elsevier Science Publishers B.V., 1991), which is herein incorporated by reference. One family of these hybrid polymers which has particular utility is commercially available from Fraunhofer-Gesellschaft (Munich, Germany) and designated by German trademark ORMOCERS®. Inorganic-organic polysiloxane hybrid polymers are also disclosed in DE 43 03 570, which is herein incorporated by reference. Also hybrid polysiloxane polymer which acts as a matrix or binder for zeolite additives to form a zeolite-polymer composite can be used (U.S. Pat. No. 6,248,682). Virtually any molecular sieve materials such as zeolite material or mixtures of zeolites may be utilized for the composite materials.
Aspects of the present invention are realized by a manufacturing method of an optical data storage or optical data display device with ensured reliability and processing stability by forming a structure in a simple manner that incorporates the oligo-atomic metal clusters confined in molecular sieves in a polymer matrix.
Aspects of the present invention are also realized by a paint, gelling liquid or elastomer comprising molecular sieves with oligo atomic silver clusters confined therein for forming optical data storage membranes or optical data storage films or for coating surfaces with a data-storage capable layer.
Aspects of the present invention are also realized by a printing liquid or ink comprising molecular sieves with oligo atomic silver clusters confined therein for depositing, spraying or printing or painting an optical data storage layer or coating on a substrate.
Paints or fluids comprising the data-storage capable porous structures of the present invention can be used for coating surfaces with the data-storage capable porous structures.
Media (e.g., paints, gelling liquids, elastomers) are available and methods of manufacturing to achieve such membranes or films, for instance, a filled elastomeric polymer, which comprises the oligo-atomic metal clusters confined in molecular sieves or in ordered porous oxides (microporous or mesoporous or mixed mesoporous/microporous) or porous materials with nanometer dimension (0.3-10 nm) windows, channels and cavity architectures, are known.
Particularly suitable are the resin(s), water-insoluble fatty acid esters of polyvalent alcohols, or ethinols as solvent.
The data storage molecular sieves of present invention can be incorporated and dispersed over a polymer matrix by state of the art technology. ZSM-5 crystals have for instance been incorporated into conventional polymer films and selective separations have been achieved [see Duval, J.-M., Kemperman, A. J. B., Folkers, B., Mulder, M. H. V., and Desgraddchamps, G., J. Appl. Polym. Sci., volume 54 (1994) 409-418]. U.S. Pat. No. 4,973,606 teaches insertion of zeolites into polymers, such as thermoplastic elastomers or duromers, for producing membranes with controllable selectivity for material separation. U.S. Pat. No. 5,069,794 teaches application of zeolite coatings to different substrates to act as thin membranes.
Incorporating molecular sieve zeolites into silica films has also been previously reported by Bein, et al. [see Bein, T., Brown, K., Enzel, P., and Brinker, C. J., Mat. Res. Soc. Symp. Proc., volume 121 (1988) 761-766]. Such an approach utilizes tetraethylorthosilicate (TEOS) as the sole source of silica delivering nitrogen impermeable films.
The data carrying porous structures, in particular the confined metal clusters in microporous materials that are in molecular sieves, may be incorporated in paints or printing inks (e.g., printable matrix printing ink or printable paints, varnishes (e.g., overprinting varnishes) and paints for depositing, spraying, printing or painting such as a layer or coating on a substrate such as foil, paper and board and aluminium-vaporised paper. Printing inks or paints of the art which are suitable for comprising the emitting materials or data carrying porous structures of present invention are, for instance, hard resins, colophony-modified phenol resins, maleate resins, hydrogenated mineral oil cuts, synthetic aromatic oils, alkyd resins in particular hydrocarbon resins and/or a colophony resin ester and dialkyl ether such as di-n-dodecyl ether, di-n-undecyl ether, allyl-n-octyl ether, n-hexyl-n-undecyl ether as a vehicle.
- Solvent-Free Processes for Manufacturing Membranes or Films Incorporating Data-Storage Capable Porous Structures
Suitable printing inks in the art are described in U.S. Pat. No. 4,028,291, U.S. Pat. No. 4,169,821, U.S. Pat. No. 4,196,033, U.S. Pat. No. 4,253,397, U.S. Pat. No. 4,262,936, U.S. Pat. No. 4,357,164, U.S. Pat. No. 5,075,699, U.S. Pat. No. 5,286,287, U.S. Pat. No. 5,431,721, U.S. Pat. No. 5,886,066, U.S. Pat. No. 5,891,943, U.S. Pat. No. 6,613,813 and U.S. Pat. No. 5,965,633. The data storage media of present invention may be painted, printed or coated on a substrate in an optical information carrying tag, marker or image.
A matrix comprising oligo-atomic metal clusters confined in molecular sieves of present invention can be coated by depositing a second film on such optical information storage layers. This can be done by plasma deposition. Plasma polymerization is a technique used for depositing polymer-like organic materials, usually in the form of thin films, onto surfaces in contact with or near a plasma discharge. Unlike conventional polymers, plasma polymers do not consist of long chains of monomeric repeat units with sparse “cross-links” connecting the chains. Instead, they are highly branched, three-dimensional interlinked monomer-derived networks which result from fragmentation and dissociation in the plasma in which the film-forming reactant species are generated. Plasma polymerized films are formed from organic monomers and are in general, pinhole-free, dense and amorphous. When compared with conventional polymer films made from the same monomer(s), plasma polymers exhibit better adhesion, and improved chemical and mechanical resistance. Furthermore, the properties of the deposited films can be changed by varying the deposition parameters. Plasma polymerized films are generally formed in an apparatus that typically consists of three parts: (1) a vacuum system, (2) an electrical excitation system for generating a plasma, and (3) a monomer gas delivery system. As monomer molecules flow through the vacuum chamber, the plasma discharge energizes and disassociates the monomer molecules into neutral particles and reactant fragments in the form of electrons, ions and free radicals. As these reactant fragments recombine on a substrate, a highly branched and cross-linked three-dimensional network is formed.
- Sol-Gel Processes for Manufacturing Membranes or Films Incorporating Data-Storage Capable Porous Structures
Other aspects of the present invention concern the incorporation of oligo-atomic metal clusters confined in molecular sieves into a matrix of polymeric fibers or other synthetic or artificial fibers which can be ordered for instance by weaving, knitting, crocheting, knotting, or pressing fibers together in a flexible material comprised of a network of such fibers. Such flexible material can be further processed into a fabric. Examples of synthetic fibers are the fibers of the group Nylon, Modacrylic, Olefin, Acrylic, Polyester, PLA, Vinyon, Saran, Spandex, Vinalon, Aramids (known as Nomex, Kevlar and Twaron], Modal, PBI (Polybenzimidazole fibre), Sulfar, Lyocell, Dyneema/Spectra, M-5 (PIPD fibre), Orlon, Zylon (PBO fibre), Vectra LCP polymer, Acrylonitrile.
- Process for Manufacturing Membranes or Films Incorporating Data-Storage Capable Porous Structures from Solvent
Another approach of incorporating the data storage molecular sieves of the present invention is to tailor the properties of sol-gel derived materials, which involves organic compound additions to gels for modifying the characteristics of inorganic sol-gel materials. In this approach, the inorganic part of the matrix-forming material provides rigidity and thermal stability, while the organic components in general contribute elasticity and flexibility, although at the expense of some thermal stability. Recent studies by Mackenzie et al, and others have documented such approaches [see Hu, Y. and Mackenzie, J. D., J. Mater. Sci., volume 27 (1992) 4415-4420; Mackenzie, J. D., Chung, Y. J., and Hu, Y., J. Non-Cryst. Sol., volumes 147&148 (1992) 271-279; Hu, Y., Chung, Y. J., and Mackenzie, J. D., J. Mater. Sci., volume 28 (1993) 6549-6554; Iwamoto, T. and Mackenzie, J. D., J. Mater. Sci., volume 30 (1995) 2566-2570; Nazeri, A., Bescher, E., and Mackenzie, J. D., Ceram. Eng. Sci. Proc., volume 14 (1993) 1-19; Rose, K., Wolter, H., and Glaubitt, W., Mat. Res. Soc. Symp. Proc., volume 271 (1992) 731-736; Schottner, G., Rose, K., and Schubert, U., Intell. Mater. & Sys. (1995) 251-262; Rose, K., Organosilicon Chem. II, Auner, N. and Weis, J., eds. (1996) 649-653]. With these methods, co-polymers are typically formed from alkoxysilanes, usually with TEOS or tetramethylorthosilane (TMOS) as the primary silica source. In these methods, hydrolysis reactions, usually in acid media, precipitate silica moieties, which are then crosslinked by condensation reactions between other silane molecules or silica moieties, which have external-OH groups at their surfaces.
In the preparation of data storage membranes, the data-storage capable porous structures may first be dispersed in an appropriate solvent. An appropriate solvent is a solvent of low ionic strength, for instance an ionic strength of a value in the range of 1 mmol/L to 0.05 mol/L, and should be able to dissolve the elastomer as well, or at least, should be partially miscible with the solvent in which the membrane-forming polymer is dissolved. To improve the dispersion, ultrasonic wave treatment, high speed mixing, modification reactions, can be applied.
The content of data-storage capable porous structures and polymer, in the dispersion, may range from 1 wt % to 80 wt %, preferably 20 wt % to 60 wt %. The dispersion is stirred for a certain time to allow (polymer/filler) interactions to establish, to improve dispersion and possibly to let a chemical reaction take place. When appropriate, the dispersion can be heated or sonicated.
A particular method of coating is solution-depositing of the molecular sieves comprising oligo atomic silver clusters comprises spray-coating, dip-casting, drop-casting, evaporating, blade-casting, or spin-coating the molecular sieves comprising oligo atomic silver clusters; ordered mesoporous and/or microporous oxides comprising oligo atomic silver clusters or porous materials with nanometer dimension (0.3-10 nm) windows, channels and cavity architectures with an assembly of oligo atomic metal clusters confined in such structures (hereinafter the data-storage capable porous structures or DSCPS) onto a substrate (FIG. 3)
The (polymer/data-storage capable porous structures or paint/data-storage capable porous structures) dispersion can be cast on a non-porous support from which it is released afterwards to form a self-supporting film. One way to realize this is by soaking it previously with a solvent, which has a low affinity for the dispersion. Also, the support can be treated with adhesion promoters.
The (polymer/data-storage capable porous structures or paint/data-storage capable porous structures) dispersion can be cast or printed on a fibrous structure such as a textile, paper or board.
After casting, printing or coating, the solvent is evaporated and, if necessary, a heat treatment can be applied to finish the cross-linking reactions. The heat treatment can possibly occur under vacuum conditions to remove the remaining solvent. The resulting supported membranes may be a filled elastomer with the thickness of this selective layer in a range from 0.01 μm to 500 μm, preferably from 0.1 to 250 μm and yet more preferably from 10 to 150 μm.
A particular example of manufacturing a data storage carrier based on the data-storage capable porous structures of present invention and a polymer is for instance the use of polydimethylsiloxane (PDMS), RTV-615 A and B (density 1.02 g/ml) and the adhesion promoter (SS 4155) which are obtainable from General Electric Corp. (USA). Component A is a pre-polymer with vinyl groups. Component B has hydride groups and acts as cross-linker and EPDM (Keltan® 578 from DSM) and data-storage capable porous structures of present invention, which are well dried before use.
- Means of Data-Storage Detection
Such can be produced by preparing dispersing a powder of the data-storage capable porous structures of present invention (for instance a zeolite comprising oligo atomic silver clusters) in hexane; adding the cross-linker (RTV 615 B) to the dispersion of data-storage capable porous structures of present invention and stirring this mixture at 40° C. for two hours to allow sufficient time to establish strong interactions between both phases. Adding the pre-polymer (RTV 615 A) and stirring the mixture for another hour at 60° C. to induce pre-polymerization. Pouring the (PDMS/ZSM-5 CBV 3002) in a petri-dish and allowing the solvent to evaporate for several hours and the resulting film was cured at 100° C. The content of the solid components (i.e., PDMS and filler) in the casting solution was 18.5 wt %. The RTV 615 A/B ratio for optimal polymer curing was 7 to compensate for the loss of hydride groups due to their reaction with the surface silanol groups on the zeolite (normally it is in a 10/1 ratio, as proposed by the manufacturer to be the ratio for optimal curing).
Aspects of the present invention are also realized by a method of writing optical data in a pattern on the data storage medium of any of the previous claims comprising exposing locoregional portions of the material, with at least one assembly of small Au and/or Ag clusters confined a molecular sieve particle, to radiation at a radiation power sufficient to cause such assembly which absorbs the radiation to emit light photons and of visualizing such stored optical data by reradiating them or by a larger portion of the materials with lower radiation power sufficient to only read the assemblies of small Au and/or Ag clusters confined a molecular sieve which store the optical data.
FIG. 2 shows a Scheme of the photoactivation of specific patterns in an individual silver-exchanged zeolite crystal in order to generate bar codes.
FIG. 4 demonstrates a) False color emission image of a single silver-exchanged zeolite A crystal before photoactivation (1) and after consecutive activation of three individual spots (2, 3 and 4) in one crystal by irradiation with a ps 375 nm laser at 10 W/cm2 during 20 minutes for each spot through a confocal microscope. b) Total activation of a single crystal. (1) shows the crystal before activation. After 5 min of irradiation by a 16.7 kW/cm2 pulsed 375 nm beam the intensity increased by a factor 10 (2). Another 20 minutes of activation at the same power yielded a total intensity increase of a factor 20. Note the increased scaling range from (1) to (3). The images in a) and b) were taken by a confocal microscope under irradiation by a 375 nm pulsed excitation source of respectively 10 and 20 W/cm2, with 2 ms integration time per pixel. c) True color image taken with a digital camera (Canon PowerShot A710 IS with a 400 nm longpass filter in front of the lens to filter out the excitation light) through the eye piece of the microscope showing the green emission from the same zeolite after complete activation at 16.7 kW/cm2 excitation power.
Security images generally comprise an image which is invisible or otherwise undetectable under ambient conditions or which comprise optical information which is invisible or otherwise undetectable under ambient conditions, and which can be rendered visible or detectable by application of a suitable stimulus; or alternatively, the image may change from one color under ambient conditions to another color upon application of a stimulus. A stimulus suitable for the materials of present invention is for instance voltage, electromagnetic radiation, UV radiation or radiation with light at a wavelength below 400 nm to induce a wavelength switch to the lower wavelengths.
- Uses of Molecular Sieves with Oligo Atomic Silver Clusters Confined Therein as 3D Encodable Microcarriers
Articles, which include security images, are useful in many areas of industry, for example in packaging, identification cards, biolabels and labels. Such articles may comprise a further printed image, in addition to the security image. It is useful to provide packaging which includes a security image invisible to a user under ambient conditions, but which can be rendered visible upon application of a stimulus; for example, if a customs and excise official wishes to check whether imported goods are genuine or counterfeit or simply want a radiation means or radiation element to automatically trace a particular items with the data storage image among other items that are not for seen of the optical information image. If the packaging includes the security image, rendered visible or otherwise detectable by a suitable stimulus, the customs and excise official can determine that the packaging, and hence the goods, are not counterfeit. Likewise, it is advantageous to provide an identification card in which a security image is invisible or a defined color under ambient conditions, but which can be rendered visible or detectable, or change color upon application of a stimulus in order to prove the identity of a user of the identity card, in order to determine that the identity card is genuine. For instance in the manufacture of bank notes, it is desirable to include as many security features as possible, which may include multiple security images using a variety of compounds capable of changing color upon application of a stimulus or stimuli (including movement of the bank note to change viewing angle), or turning colored from colorless, or vice versa. The advantage of present invention is that the microporous materials can be integrated in fibres which can be integrated in the fibre mixing process during production of such security documents or banknotes.
The extraordinary photostability of the formed clusters and the enhanced 3D-resolution due to 2-photon excitation allows the creation of several layers of advanced matrix codes such as the 2D MaxiCodes and QR-codes inside an individual molecular sieve crystal, such as a zeolite crystal. Moreover, they are compatible with water. This makes them suitable for use in applications such as multiplex (bio)assays, high-throughput screening methods, in safety and quality labels to prevent counterfeiting. Furthermore, encoded silver zeolites can, for example be mixed in drug powders to serve as a built-in certificate of authenticity.
According to a preferred embodiment of the method, according to the present invention, the method according further comprises the step of attaching said data-wise exposed oligo-atomic metal clusters confined in a molecular sieve to a support as an identifying tag.
According to another preferred embodiment of the method, according to the present invention, the method further comprises the step of adding said data-wise exposed oligo-atomic metal clusters confined in a molecular sieve to a liquid medium as an identifying tag.
According to another preferred embodiment of the method, according to the present invention, the method further comprises the step of adding said data-wise exposed oligo-atomic metal clusters confined in a molecular sieve to a plurality of particles as an identifying tag.
- INDUSTRIAL APPLICATION
According to another preferred embodiment of the method, according to the present invention, the oligo-atomic metal clusters confined in a single molecular sieve crystal is attached to a molecule.
Preparation and Methods
The present invention concerns the field of data storage materials for use as, e.g., bio-labels, and for related applications, comprising, e.g., white light and colored luminescent materials with emission of visible white or colored light at or above room temperature in which the luminescent intensity can be increased by the irradiation of light. The optical data storage compositions with the data carrying porous structures of present invention can be attached or integrated on articles to provide such articles with for instance a security image or a bio-label.
Various methods for the production of metal ion exchanged molecular sieves are available in the art. A method similar to that described by Jacobs et al. (Jacobs, P. A. & Uytterhoeven, J. B., 1979, Journal of the Chemical Society-Faraday Transactions 175, 56-64) was used for incorporating silver ions in molecular sieves and creating silver clusters. However many parameters like loading percentage of the zeolites, exchange time, length of temperature treatment, initial, gradient and final temperature of the temperature treatment, presence of gasses during the temperature treatment (e.g. in vacuum, in presence of oxygen, in presence of oxygen and nitrogen, in presence of hydrogen, in presence of CO and/or CO2 gas) and the presence of moisture in the air influences the finally formed types of clusters, oxidation state of the clusters and distribution and polydispersity of the types of clusters formed.
- Example 2
A typical procedure goes as follows: Zeolite 3A (Union Carbide; 500 mg) was suspended in 100 mL MQ-water containing 13±1 weight percent of silver nitrate (8±1% Ag). After stirring in the dark for 2 hours the ion exchange (±17% of the zeolite's cation exchange capacity) was stopped. The material was poured on a Büchner filter and extensively washed with MQ-water. This washing stepped proved a quantitative silver exchange since no precipitation with chlorides was observed in the washing water. The recovered white powder on top of the filter was heated gently until 450° C. for 1 day with 5 minute stops at 50° C., 70° C., 90° C. and 110° C. to avoid damaging of the zeolite structure. After this heat treatment a white to sometimes slightly yellowish powder was obtained. The powder was stored in the dark under dry atmosphere.
- Example 3
Photoactivation of Individual Spots within an Individual Silver-Exchanged Zeolite Crystal
Writing Patterns Inside the Zeolite Crystals
It was demonstrated that metal ion clusters especially silver in confined molecular sieves have a distinct and tunable emission throughout the VIS and NIR part of the electromagnetic spectrum while they are all excitable in the UV region. Thanks to the host matrix the confined metal clusters are prevented from aggregation with each other to form bigger non-emissive nanoparticles. Also they can be shielded from the outside environment (e.g., oxygen) if required by adding a silicon coating around the molecular sieves.
By irradiation with picoseconds pulsed 375 nm laser light of selected spots inside a silver-exchanged zeolite crystal, synthesized as described in example 1, using a confocal microscope setup, highly emissive silver clusters are formed inside a diffraction limited area, induced by the applied excitation source, giving rise to a strongly enhanced fluorescence (up to 200 times) from these selected spots. Typical irradiation powers for activation are 10 to 10,000 W/cm2 for photoactivation, whereas irradiation times vary from a 10 seconds for 10,000 W/cm2 to 1200 seconds for irradiation at 10 W/cm2.
- Example 4
Tunable Color of Excitation and Emission of the Visible Emission Source
By scanning the sample using a lower power (0.1 to 10 W/cm2), the photoactivated areas are easily recognized by their bright emission without further photoactivation during the scanning process.
- Example 5
Bright Emissive Markers
The molecular sieves containing the oligo atomic clusters can be excited by UV light resulting in emission in the visible range as described in Example 3. However by changing or tuning the excitation wavelength or by using multiple excitation wavelengths coming from one or multiple sources and by tuning the different ratios of excitation power between the different wavelengths, it is possible to tune the color of the visible emission. In this way one could have one emissive device which output color can be tuned by the end user. This effect can be achieved by using different oligo atomic clusters in the molecular sieves that have a different emissive response on different UV wavelengths. An example of this was synthesized where irradiation of the materials with 360 nm light resulted in blue emission while exciting at 254 nm resulted in yellow emission. If one excites with the two wavelengths, 254 nm and 360 nm at same time and by changing the ratios of excitation power, one creates a whole range of emission colors between blue and yellow and all the possible sum colors.
- Example 6
1. How to Write in the Material:
Since the oligo atomic clusters containing molecular sieves are a bright emissive material, consisting of generally micrometer or submicrometer sized crystals, one can use these small crystals as bright emissive markers. Especially when they are smaller than 100 nm they can be used as alternatives for fluorescent beads or quantum dots.
A high-intensity 375 nm ps pulsed laser beam is focused through a confocal microscope on the material (the setup is explained in more detail below). Lower laser intensity can be compensated by a much longer irradiation time. For instance at 0.01 kW/cm2, an irradiation time of 1200 seconds is necessary, whereas 10 seconds is sufficient when using 10 kW/cm2.
2. How to Read Data from the Material:
- Example 7
Excitation by an Electrical Field and Emission of the Visible Emission Source
The same microscope with the same laser source is used to map the emission of the crystal. However, much lower excitation power is applied. Typically, the sample is scanned using an excitation power of 0.1 till 10 W/cm2. Read out times of only 0.1-10 ms are necessary.
- Example 8
Preparation of a Heated-Treated Agx, K-A Zeolite
A 3A zeolite was exchanged with silver (10% weight) and then thermally treated (24 hours at 450° C.) resulting in a partial reduction and formation of small silver clusters in the host matrix. 0.4 mg of these silver loaded zeolites were added to 1 ml of a 20 mg/ml PVK (poly-N-vinylcarbazole) in chlorobenzene solution. From this solution a film was spincoated on an ITO covered glass substrate. Ytterbium was then evaporated through a patterning mask on the spincoated film as a second electrode. After applying an electric field over this device, in which ITO functioned as anode and ytterbium as cathode, red electroluminescence was observed. The emission spectrum of this electroluminescence is shown in FIG. 5. The synthesis of the oligo metal clusters with the desired emissive properties can be tuned by changing the synthesis parameters.
- Example 9
2-Photon Photoactivation Process in the Silver Zeolite Prepared in Example 8
Large LTA-type crystals were obtained by employing the following reactants: sodium hydroxide pellets (99.9%, Riedel de Haën), Al powder (Fluka), triethanolamine (Aldrich), fumed silica (Degussa) and distilled water. In a typical preparation A sodium aluminate solution was prepared by dissolution of aluminum powder (Fluka) in sodium hydroxide solution. A mixture of triethanolamine and water was mixed with sodium aluminate solution and stirred for 5 minutes at room temperature. The silica source (fumed silica, Degussa) was then added to the mixture stirred at room temperature for 1 h. The synthesis was performed at 95° C. for 10 days. The solid was recovered by suction filtration and dried at 80° C. overnight. The zeolite crystals obtained were first exchanged with K+ ions by stirring an aqueous suspension of the zeolites in the presence of an excess of KNO3 for 1 day. After filtration and washing, the zeolites were suspended in 100 mL MQ-water containing 13±1 weight percent of silver nitrate (8±1% wtAg/wtzeolite). After stirring in the dark for 2 hours the ion exchange (±17% of the zeolite's cation exchange capacity) was stopped. The material was poured on a Büchner filter and extensively washed with MQ-water. This washing step provided proof of a quantitative silver exchange since no precipitation with chlorides was observed in the washing water. The recovered white powder was dried at 110° C. for 1 day giving a white powder. The white powder was stored in the dark in a dry atmosphere.
Emissive patterns were written in individual silver zeolite crystals by excitation with a femtosecond pulsed (80 MHz) 780 nm laser (Mai Tai, SpectraPhysics). The excitation light, circularly polarized by use of a Berek polarization compensator (New Focus), was directed using a dichroic beam splitter into the oil-immersion objective (Olympus, 1.3 N.A., 100×) of an inverted fluorescence microscope (Olympus IX70) equipped with a piezo-controlled scanning stage (Physics Instruments). The excitation power was adjusted with a neutral density wheel at the entrance port of the microscope. Typical excitation powers for writing the patterns were of the order of 400 kW/cm2. Typical irradiation times of 250 ms per pixel were sufficient for writing patterns with a good contrast ratio. A home built-software was used to direct the piezo stage scanner for writing the patterns.
The image in FIG. 6 a was imaged using the same setup as described above. The fluorescence was collected by the same objective, guided through a pinhole of 100 μm diameter, filtered and focused onto an avalanche photo-diode (SPCMAQ-15, EG & G Electro Optics). The scanning images were obtained using a reduced excitation power of about 50 kW/cm2 to avoid further photoactivation during the scanning process and for each pixel the intensity was integrated over 2 ms.
FIGS. 6 d, 7 and 8 were obtained by transferring the sample to a FluoView 500 confocal fluorescence microscope (Olympus). The fluorescence signal generated by a 488 nm Ar+ continuous wave laser (Spectra Physics) was detected using a photo-multiplier tube (PMT) after passing a dichroic mirror (488 nm) and a 505 nm long pass filter. The pinhole was set to 100 μm to ensure a good axial resolution.
FIG. 6 a shows the image of the flag of the Flemish community written into an individual silver-exchanged zeolite A particle with dimensions of approximately 20×20×20 μm3 using a femtosecond pulsed 780 nm laser focused on the sample through a confocal fluorescence microscope. The image is written on a plane buried 2.5 μm inside the zeolite.
FIG. 6 b shows the template image of 80 by 80 pixels, which was fed into the home-built software used to steer the sample over the focussed laser. The intensity of every pixel was translated by the software to the laser exposure time (0 ms for a black pixel to 255 ms laser exposure for a completely white pixel). After photoactivation, the written pattern was imaged using the same setup, but with reduced excitation power (less than 100 kW/cm2) to avoid further activation. Even the fine details of the image, such as the tongue of the lion, are well resolved, yielding a realistic replication of the original template on a scale of ±17×17 μm2.
By controlling the photoactivation time, different intensity levels can be obtained within one image, allowing grey scale images to be stored inside the zeolite particles. This is illustrated in FIG. 1 c, where an intensity profile along the white dashed line of FIG. 1 a is shown (black curve), together with the corresponding profile of the template image (grey curve). The tongue of the lion, which is grey in the template image, indeed has about half the fluorescence intensity of the other activated regions. The possibility of distinguishing different intensity levels provides an additional parameter that greatly increases the amount of unique accessible codes within one individual crystal.
The written pattern in FIG. 1 a almost spans the entire xy-plane of the crystal and yet all the white parts of the image are activated to a similar extent. This implies on the one hand that the silver is well dispersed throughout the whole crystal and on the other hand that the 2-photon excitation approach is not very sensitive towards small particles adsorbed on the outer surface and heterogeneities and crystal imperfections which are mostly present in large zeolite crystals. With 1-photon activation, writing such a large pattern would be considerably hampered by the many scattering sites on the outer surface, resulting in zones with high background activation.
To estimate the writing resolution, three thin bar patterns with varying inter-bar spacings were written in the zeolites (FIG. 6 d). As the bars of the template image have an infinitely small width, the width of the resulting activated area directly reflects the spatial resolution. FIG. 6 e shows the integrated intensity profile along the x-dimension of the area between the dashed lines in FIG. 6 d. The profile reveals that bars separated by as little as 500 nm are still resolvable and that the full width at half maximum (FWHMimage,xy) of one bar is below 500 nm. The Gaussian profile obtained is, however, in fact the convolution of the written area and the Gaussian-shaped point-spread-function (psf) for imaging. Upon deconvolution a writing resolution of 444 nm was obtained.
The 2-photon excitation approach particularly confines the region of cluster formation in the axial dimension, allowing for the writing of three-dimensional images. FIG. 2 a shows the fluorescence images at different focal planes inside a single zeolite crystal in which the letters “K”, “U” and “L”, the abbreviation of our university, are written on top of each other over a distance of scarcely 6 μm using 2-photon excitation (780 nm).
Determining the axial resolution from this stack of images along the z-axis is difficult since confocal microscopy has a limited resolution for imaging along this dimension. One can thus not know whether the obtained resolution is determined by the writing or the reading resolution. To circumvent this problem the crystal was mechanically flipped over on its side such that the xz plane of writing now lies horizontal such that it can be imaged with the higher radial resolution. FIG. 7 b shows a slice of the flipped crystal through the legs of the photoactivated letters “K”, “U” and “L”, where it can be seen that the activated regions are well resolved along the z-direction. Fitting the line profile as indicated by the dashed lines yields a FWHM of 1 μm (FIG. 7 c). This is well above the reading resolution of 213 nm and thus it reflects the true writing resolution. To the best of our knowledge such an axial resolution for encoding microcarriers is unprecedented by optical light based techniques. Over a distance of merely 6 μm at least three resolved layers of information can now be stored.
When photoactivation is performed using single-photon excitation at 375 nm, the resolution is limited to about 636 nm in the xy-plane and 4.3 μm along the axial dimension in the case of a smooth crystal without too many scattering sites. However, for practical applications the surface of the zeolites will often be functionalized to bind targets such as biological cells that can cause some scattering of the activation light. In the case of 1-photon activation this would lead to strong scattering and as a result worse resolution. As scattering is less of an issue in 2-photon photoactivation, this technique provides a major improvement of the axial resolution by at least a factor 4, while the radial resolution is enhanced by more than 30%. Moreover 2-photon photoactivation allows a more reproducible and homogeneous photoactivation in the different zones of the crystal.
- Example 10
2-Photon Photoactivation Process in Silver Zeolites in an Aqueous Environment
With the strongly improved three-dimensional resolution for encoding data in microparticles, the creation of 3D micro-structures comes within reach. A first attempt in this direction is illustrated in FIG. 8, where a 3D-spiral structure is activated over a depth of 7.5 μm inside a single zeolite crystal.
For applying the encodable silver zeolites in multiplex bio-assays, the photoactivation process must be compatible with aqueous environments. Therefore a photoactivation experiment was performed on a crystal after adding a few drops of water onto the glass coverslip. Photoactivation was carried out on the FluoView 500 system using 1-photon excitation at 375 nm. The fluorescence intensity time transient is shown in FIG. 9. Significant activation clearly took place in the presence of bulk amount of water, the water appearing not to influence the photoactivation process. The activated area was imaged at 488 nm excitation. The left side of FIG. 10 shows the fluorescence intensity image with the contours of the crystals indicated by the dashed white lines, and the right side of FIG. 10 shows the transmission image overlaid.
The processes of in situ encoding and decoding in the silver zeolites are therefore compatible with an aqueous environment, and the encoded patterns are stable over extended periods of time, thanks to the steric confinement of the generated silver clusters inside the zeolite cages and to the extraordinary photostability of silver clusters in general.
This makes this material a potential alternative for use in multiplex bio-assays. It was previously shown that after coating encodable microparticles with a polyelectrolyte layer, cells can be grown on the surface of those particles. For different cell types a specific code can be written into the attached particle in order to be able to identify the cell afterwards in the multiplex experiment. A similar scheme is also feasible with zeolite microcarriers. Moreover there is plenty of knowledge on introducing functional groups at the outer surface of zeolites by simple silanization chemistry or vapor deposition methods. Interactions between functionalized zeolites and living systems have previously been demonstrated by Z. Popovic in 2007 in Angew. Chem. Int. Ed., volume 46, pages 6188-6191.
All of this makes silver zeolites a versatile tool in many kinds of (biological) high-throughput screening assays, multiplex assays or as safety labels against counterfeiting. Moreover our proposed method even has the potential for sub-diffraction limited pattern writing. Indeed the combination of the non-linearity between irradiation intensity and rate of cluster formation on the one hand and the two-photon excitation approach on the other hand strongly confines the actual region of cluster formation. If scattering effects and effects from refractive index mismatches between the different interfaces (glass-air-crystal) can be eliminated, the writing of sub-diffraction limited patterns without the need of complicated experimental setups, such as 4PI microscopes, comes within reach.