RU2509062C2 - Method of forming silver nanoparticles in glass - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: method involves depositing a silver film on the surface of silicate glass doped with cerium, holding the obtained structure at temperature of 400-600°C for 2-10 hours, irradiating the structure with UV radiation and then holding at temperature of 400-600°C for 2-10 hours.

EFFECT: method enables to obtain glass composites with high concentration of silver nanoparticles in the surface region of the glass and solves the task of making planar waveguides in glass composites.

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Description

The invention relates to a technology for creating optical materials and can be used in integrated optics and biosensor technologies. Composite materials with metal nanoparticles (Au, Ag, Cu, Pt, Pd) are widely used in the creation of biosensors based on plasma (nanoparticles) nanostructures and metamaterials (see DA Stuart, AJ Haes, CR Yonzon, EM Hicks and RP Van Duyne. - Biological applications of localized surface plasmonic phenomena // Nanobiotechnology (2005), 152 (1); 13), for amplification of fluorescence signals (see E. Fort, S. Gresillon. - Surface enhanced fluorescence // J. Phys. D: Appl. Phys. 41 (2008) 013001, 31pp) as non-linear optical media for high-speed optical switches (see R. Chakraborty. - Metal nanoclasters in glasses as non-linear photonic materials // J. Mater. Sci., 1998 , Vol.33, P.2235-2249), photo media (see AV Dotsenko, LB Glebov, VA Tsekhomsky. - Physics and Chemistry of Photochromic Glasses, CRC Press LLC, 1998, 190 p.), metamaterials (see NA Litchinitser, IR Gabitov, AI Maimistov, VM Shalaev. - Negative refractive index metamaterials in optics. Progress in Optics (ed. By E. Wolf), 2008, Vol.51, P.3-60), as well as for the manufacture of integrated optical devices based on surface electromagnetic waves (plasmons) (see AV Zayats, II Smolyaninov, AA Maradudin. - Nano-optics of surface plasmon polaritons // Physics Reports. 2005, V.408, P.131-314).

A known method of forming silver nanoparticles in glass (see ed. Certificate SU 919286, IPC C03C 17/06, C03C 17/22, published 08/20/2004), comprising applying layers of silver and metal halides to the glass surface with heat treatment of each layer, which, in order to increase productivity and reduce silver consumption, a layer of metal halides is applied from the powder before applying the silver layer, and the latter by anodic dissolution.

As a result, metallic nanoparticles with a large variation in size and shape are formed in glasses with photochromic properties obtained in a known manner, which leads to the absence of a pronounced absorption band associated with the plasma resonance effect. This fact excludes the possibility of using such glasses in integrated optics and biosensor technologies.

A known method of forming metal nanoclusters in glass (see application PCT WO 0140132, IPC С03С 11/00, claimed 07.06.2001), including the preliminary manufacture of colloidal metal nanoparticles, applying them to the glass surface and subsequent exposure at a temperature of 550-720 ° C for at least 30 minutes.

The disadvantage of this method is the complexity of its implementation due to the large number of operations. The absorption band associated with the localized plasma resonance of metal nanoparticles obtained by the known method has insufficient intensity.

A known method of forming silver nanoparticles in glass (see patent RU 2394001, IPC С03С 17/06, В82В 3/00, published July 10, 2010), which consists in the fact that glass containing silver or copper ions, or silver or copper halide nanoparticles , irradiated with an electron beam with energies of 2-50 keV and doses of 2-20 mK / cm ² , and then kept at a temperature of 400-600 ° C for 2-10 hours. As a result of electron irradiation, silver or copper ions are reduced to an atomic state. When held at a temperature of 400-600 ° C for 2-10 hours (annealing), as a result of atom diffusion, they form metal nanoparticles in a thin surface layer of glass.

The disadvantage of this method is the need to use high-current electron microscopes with a large diameter of the electron beam, which is an energy-consuming method, not suitable for the industrial implementation of this method.

A known method of forming silver nanoparticles in glass (see AV Dotsenko, LB Glebov, VA Tsekhomsky Physics and Chemistry of Photochromic Glasses. CRC Press LLC, 1998, 190 p.), Coinciding with the claimed technical solution for the largest number of essential features and selected as prototype. The prototype method consists in the fact that glass containing silver ions, or silver nanoclusters nanoclusters are irradiated with ultraviolet radiation, and then subjected to exposure (annealing) of 400-600 ° C for 2-10 hours. Ultraviolet irradiation leads to the transition of silver ions into an atomic state. As a result of diffusion, they form metallic nanoclusters.

The disadvantage of this method is the large depth of penetration of ultraviolet radiation into glass containing silver ions, which prevents the creation of thin (less than 1 μm) composite layers. The disadvantage is that the relatively large radiation wavelength (λ = 100-350 nm) prevents the creation of composite layers of a given geometry with a spatial resolution of less than 100 nm.

The present invention was the development of such a method of forming silver nanoparticles in glass, which would allow to obtain glass composites with a high concentration of silver nanoparticles in the surface region of the glass, i.e. the task of the controlled manufacture of planar waveguides in glass composites.

The problem is solved in that the method of forming metal nanoparticles in glass involves applying a silver film to the surface of silicate glass doped with cerium, holding the resulting structure at 400-600 ° C for 2-10 hours, irradiating the structure with ultraviolet (UV) radiation and subsequent exposure at a temperature of 400-600 ° C for 2-10 hours.

The structure can be irradiated with ultraviolet radiation with a wavelength of A = 100-350 nm and a dose of Q = 20-30 J / cm ² .

A silver film with a thickness of 50-150 nm can be applied to the surface of silicate glass, but the film thickness is not critical.

Silver film on the surface of silicate glass can be applied by ion spraying

New in the present method is the preliminary deposition of a silver film on the surface of silicate glass doped with cerium, and the exposure of the resulting structure at a temperature of 400-600 ° C for 2-10 hours.

During the first heat treatment, thermal diffusion of the silver film into the surface layer of glass occurs, with the formation of a composite layer with silver ions Ag ⁺ The thickness of the silver film, the temperature and the annealing time are determined by two parameters; diffusion coefficient of silver in glass and the level of silver ion concentration required for the formation of nanoparticles in the surface region of the glass. With a film with a thickness of less than 50 nm, the concentration of the formed nanoparticles will be low; on the contrary, with films with a thickness of more than 150 nm, more time will be required to ensure thermal diffusion of the film into the glass volume. If the processing temperature is increased above 600 ° C and the annealing time is more than 10 hours, then the width of the profile of the layer with silver ions will increase and, consequently, their concentration in the near-surface region will decrease. When the processing temperature is less than 400 ° C and the exposure time is less than 2 hours, the silver film will not diffuse into the volume of the glass.

After the first exposure, the resulting structure is irradiated with ultraviolet radiation, for example, with a dose of Q = 20-30 J / cm ² and again annealed at a temperature of 400-600 ° C for 2-10 hours. Irradiation with ultraviolet radiation is due to the need to ensure photoionization of Ce ³⁺ for further reduction of silver ions to Ag ⁰ . The annealing time depends on the number of silver ions embedded in the glass. If the processing temperature is increased above 600 ° C and the exposure time is more than 10 hours, the nonlinear optical properties of the resulting glass composite will degrade. When the processing temperature is less than 400 ° C and the exposure time is less than 2 hours, silver nanoparticles will not be formed in sufficient concentration. Thus, ultraviolet irradiation leads to the transition of silver ions into an atomic state, and upon subsequent annealing, they, as a result of diffusion, form metal nanoparticles in a thin surface layer of glass.

The present method is illustrated by the drawing, which shows the absorption spectrum of the sample before irradiation with ultraviolet light (curve 1), after irradiation (curve 2) and after annealing (curve 3).

Example 1

On a silicate glass plate of the following composition, mol.%: SiO ₂ (69.6), Na ₂ O (14.3), ZnO (6.8), F (0.54), KBr (4.0), Sb ₂ O ₃ (0.1), CeO ₂ (0.02), a silver film 100 nm thick was deposited by ion sputtering. The sample is initially colorless and clear glass. After applying the film, the sample was heat treated at a temperature of 500 ° C for 4 hours. As a result, silver thermally diffused into the surface region of the glass, forming a surface layer saturated with silver. The glass was exposed to UV radiation with a dose of Q = 25 J / cm ² and a wavelength of λ = 280 nm, which led to photoionization of Ce ³⁺ (to ensure photoionization of Ce ^3+, it is necessary that the wavelength of the exciting radiation lie in the region of the Ce ³ absorption band ⁺ -λ _max = 310 nm or less). The electron liberated as a result of photoionization by antimony was captured by a silver ion with the formation of a neutral silver atom Ag ⁰ (namely, the centers (Sb ⁵⁺ ) ^- arising from UV irradiation at room temperature play the main role in the formation of atomic silver and Ag _n nanoclusters, since the charged center (Sb ⁵⁺ ) ^- stored to high temperatures). Subsequent exposure at 500 ° С for 2 hours as a result of diffusion of Ag ⁺ atoms, silver nanoparticles - Ag ⁰ _{n - appeared} . The formation of silver nanoparticles in a thin surface layer of glass, along with the coloring of the glass, led to an increase in light absorption and the appearance of nonlinear optical effects, which is associated with plasma resonance in silver nanoparticles.

The thickness of the composite layer with silver nanoparticles depends on the heat treatment time and the burning temperature. In this example, the diffusion depth was ~ 15 μm.

Example 2

On a silicate glass plate of the following composition, mol.%: SiO ₂ (69.6), Na ₂ O (14.3), ZnO (6.8), F (0.54), KBr (4/0), Sb ₂ O ₃ (0.1), CeO ₂ (0.02), a silver film 100 nm thick was deposited by ion sputtering. After applying the film, the sample was heat treated at a temperature of 400 ° C for 2 hours. As a result, silver thermally diffused into the surface region of the glass, forming a surface layer saturated with silver, but a thin layer of silver film remained on the glass surface. The glass was exposed to UV radiation with a dose of Q = 20 J / cm ² and a wavelength of λ = 100 nm. Subsequent heat treatment was carried out at a temperature of 600 ° C for 2 hours. The formation of silver nanoparticles in a thin surface layer of glass along with the coloring of the glass led to a slight increase in light absorption and the appearance of weak nonlinear optical effects. Therefore, due to the low temperature and time of the first annealing, a smaller amount of silver fell into the surface layer and, therefore, a smaller amount of silver nanoparticles was formed. Nonlinear effects were weakly manifested, which gives grounds to establish such annealing parameters as extreme below. The diffusion depth of silver was ~ 5 μm.

Example 3

On a silicate glass plate of the following composition, mol.%: SiO ₂ (69.6), Na ₂ O (14.3), ZnO (6.8), F (0.54), KBr (4.0), Sb ₂ O ₃ (0.1), CeO ₂ (0.02), a silver film 100 nm thick was deposited by ion sputtering. After applying the film, the sample was heat treated at a temperature of 600 ° C for 10 hours. As a result, silver thermally diffused into the surface region of the glass, forming a surface layer saturated with silver. Exposed to the glass with UV radiation with a dose of Q = 30 J / cm ² and a wavelength of λ = 300 nm. Subsequent heat treatment was carried out at a temperature of 600 ° C for 10 hours. The formation of silver nanoparticles in the surface layer of glass along with the coloring of the glass led to an increase in light absorption and the appearance of nonlinear optical effects. The diffusion depth of silver was ~ 90 μm. Composite layers with such wide profiles are weakly sensitive to changes in the dielectric constant on the glass surface. Since the thickness of the profile is determined by the time and temperature of both anneals, the above parameters can be set as extreme ones from above.

From the above examples it follows that the proposed technical solution allows the manufacture of composite layers with silver nanoparticles in thin near-surface layers of glasses. The use of ultraviolet radiation makes it possible to significantly simplify the process, vary the thickness of the composite layer, the concentration of metal nanoparticles in it, and also allows you to process large areas of glass, which is an important factor in the industrial implementation of this technology.

The present method allows the synthesis of metallic nanoparticles. firstly, in a thin surface layer of glass, and secondly, with a higher concentration, in comparison with the prototype method. A higher concentration of silver nanoparticles increases the optical nonlinearity of the resulting glasses. The method can be widely used in biosensor technologies for creating biosensors on localized plasmons and for amplifying fluorescence signals, as well as in integrated optics for the manufacture of plasma waveguides and optical switches.

Claims (6)

1. The method of forming silver nanoparticles in glass, including applying a silver film to the surface of silicate glass doped with cerium, maintaining the resulting structure at a temperature of 400-600 ° C for 2-10 hours, irradiating the structure with ultraviolet radiation and subsequent exposure at a temperature of 400-600 ° C for 2-10 hours 2. The method according to claim 1, characterized in that the structure is irradiated with ultraviolet radiation at a dose of Q = 20-30 J / cm ² . 3. The method according to claim 1, characterized in that the structure is irradiated with ultraviolet radiation with a wavelength of λ = 100-350 nm. 4. The method according to claim 1, characterized in that a silver film 50-150 nm thick is applied to the surface of the silicate glass. 5. The method according to claim 1, characterized in that the silver film on the surface of silicate glass is applied by ion spraying. 6. The method according to claim 1, characterized in that the silver film on the surface of silicate glass is applied by chemical deposition.

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