Multilayer structure formed by layers of nanoparticles having one-dimensional photonic crystal properties, method of making and using said structure

FIELD: physics.

SUBSTANCE: multilayer mesoporous structure based on nanoparticles has Bragg reflector or one-dimensional photonic crystal properties. The one-dimensional photonic crystal is formed by alternating layers with different refraction indices and controlled size, made from nanoparticles. Each layer has thickness from 1 nm to 200 nm. The method of making said structure involves a) preparing suspensions of nanoparticles, where concentration thereof ranges from 1% to 99% and b) forming a multilayer structure with high continuous porosity and having one-dimensional photonic crystal properties via successive deposition on any substrate of layers nanoparticles of controlled thickness based on the suspensions described in a) so as form alternating refraction index values. Each layer of nanoparticles has thickness from 1 nm to 1 mcm. The number of layers of nanoparticles can vary from 1 to 100.

EFFECT: high reflection coefficient while simultaneously allowing passage of liquid, which enables controlled variation of the colour of the multilayer structure.

25 cl, 7 dwg

The state of the prior art

Materials with a layered structure are widely used as optical elements, because they act as interference filters or Bragg reflectors, capable of selectively reflecting or transmitting electromagnetic radiation in the frequency range, usually enclosed between the ultraviolet and infrared ranges of the spectrum determined by the thickness and refractive index layers. If you use more modern terminology, these materials represent a one-dimensional photonic crystals, because they have a periodic modulation of the refractive index in one of the three spatial directions.

Currently, multilayer systems are commercially available, and for the most part, these are manufactured using methods generally known by the term "thermal vacuum vapor deposition". In all cases, the deposition takes place under vacuum, and the solid particles are condensed directly from the vapor phase. Optical coatings produced by the method of this type, in addition to high mechanical strength possess great resistance to changing environmental conditions. There is another large group methods of formation of multilayers based on Sol-gel processes. This JV is the event allow you to form a multilayer coating, which are very resistant to damage caused by intense laser radiation, thus have a much higher damage thresholds than patterns of other species. However, these multilayer coatings have low mechanical strength, and their properties vary according to the surrounding conditions, both phenomena are related to their metophorically, therefore they are unsuitable as passive optical elements, although they find application in other areas, such as sensors. Usually the pores of the layer grown by the Sol-gel process, are irregular in shape with a very wide distribution of particle sizes and the average size of constituting from 2 nm to 100 nm. Multilayer structure with controlled mesostructure (shape and size), the optical properties of which can be controlled, will open new opportunities for use of these species in different areas. In addition, recently developed materials with relatively controlled metophorically, which are of great interest, although the applications of these materials was not reported. There are a porous silicon multilayer structure obtained by electrochemical dissolution. A recently developed multi-layered structure in which each layer has ordered mesoporosity with tecnocontrol pore size, at the same time as materials are silicon dioxide and titanium dioxide. This work is the subject of a patent application Spain, submitted in 2006 (application No. 200602495). Finally, in the scientific literature there is information relating to the invention presented in this application, which has a close relationship to him. It relates to the manufacture of multilayers of colloidal particles of silicon dioxide and titanium dioxide as a reflective and anti-reflective coatings made I.M. Thomas in 1987, Although the described method similar to the method presented in this application, it is difficult to determine any characteristics of the obtained material, making it difficult to get an idea of the type of structure that was received at that time.

Provided in this application the invention is closely related to these four groups of materials, resulting in lower than they will be described in more detail.

Multilayer materials obtained by the Sol-gel process with alternating thick layers of TiO₂and SiO₂

The manufacturing methods commonly used for the synthesis of micro-components in the solid state, suitable for areas of the plate are small in size. If you want to besiege thin layers on parcels larger, Sol-gel processes [C.J. Brinker and G.W. Scherer, “Sol-gel science: The physics and chemistry of solgel processing”, Academic, New York, 1990] give significant advantages: they are a simple way to besiege a variety of materials (oxides, semiconductors, piezoelectric materials, ferroelectric materials, etc) in the form of thin films on various substrates (polymers, ceramic materials, metals and so on). The variety of materials that can be deposited, allows you to design the Sol-gel structure in the form of devices with photonic gap or photonic crystals.

Bragg reflectors or EB in one dimension are photonic crystals, which have been increasing due to the Sol-gel process. Very high reflectivity obtained in these materials, due to the phenomenon of Bragg reflection. Usually photonic crystals get, alternating layers of materials with high and low indices of refraction, forming a set of dielectric multilayers. Bragg reflectors, synthesized with the Sol-gel process can be obtained by applying the coating by centrifugation [R. Almeida, S. Portal, “Photonic band gap structures by sol-gel processing”, Current Opinion in Solid State and Materials Science 7 (2003), 151; R. Almeida, A.S. Rodrigues, “Photonic bandgap materials and structures by sol-gel processing”, Journal of Non-Crystalline Solids, 326&327 (2003), 405; P.K. Biswas, D. Kundu and D. Ganduli, “Preparation of wavelength-selective reflectors by sol-gel processing”, J. Mater. Sci. Lett., 6 (1987), 1481] or coating by immersion [Chen C.M., Sparks A.W., Luan H.C., D.R. Lim, K. Wada, and L.C. Kimerling, “SiO₂/TiO₂omnidirectional reflector and microcavity resonator via the sol-gel method”, Appl. Phys. Lett., 75 (1999), 3805; Hang Q., Li X., Shen J., Wu G., Wang J., Chen L., “ZrO₂thin films and ZrO₂/SiO₂optical reflection filters deposited by sol-gel method”, Mater. Lett., 45 (2000), 311; S. Rabaste, J. Bellessa, A. Brioude, C. Bovier, J.C. Plenet, R. Brenier, A. Marty, J. Mugnier, J. Dumas, “Sol-gel manufacturing oh thick Board applied to Bragg reflectors and microcavities”, Thin Solid Firms, 416 (2002), 242]. The differences between the values of the refractive indices of the materials used and the number of layers are the most important parameters of the Bragg reflector. With increasing differences in n between the layers and increasing the number of layers becomes greater reflectivity of the photonic bandgap or PBG, prohibited wavelength range from the ultraviolet region to near infrared region, which are reflected by a dielectric mirror. Usually use SiO₂, TiO₂and ZrO₂due to the significant differences between their refractive indices(1,45-1,52; 2,07-2,55; 2,1-2,2 respectively). The problem with the synthesis of this type, is that when the number of layers also increases the risk of development of cracks in the material, which may compromise the structural integrity of the multilayer. To resolve this problem Almeida and others [R. Almeida, A.S. Rodrigues, “Photonic bandgap materials and structures by sol-gel processing”, Journal of Non-Crystalline Solids, 326&327 (003), 405] and Rabaste, etc. [Rabaste, J. Bellessa, A. Brioude, C. Bovier, J.C. Plenet, R. Brenier, A. Marty, J. Mugnier, J. Dumas, “Sol-gel manufacturing of thick Board applied to Bragg reflectors and microcavities”, Thin Solid Films, 416 (2002), 242] used a very short heat-sealing treatment at very high temperatures (1000°C for 90 s and 900°C for 2 s, respectively), which had been set up to 60 layers with thicknesses in the range from 80 nm to 100 nm, with reflectivity above 99% (at normal incidence). Heat sealing treatment is carried out after the synthesis of each of the layers, and when using such high temperatures the crystallization of TiO₂of the first layer cannot be excluded, because the first layers are exposed to high temperatures for longer periods of time due to repeated heat treatments to which they are exposed. The crystal growth should be carefully monitored, since it degrades the optical performance of multilayer by introducing dispersion of Rayleigh and because of the roughness formed at the interface with layers of SiO₂. In addition, the first layers are subjected to compaction in less than the last layers, which are exposed to high temperatures for shorter periods of time; it's an uneven seal also entails a reduction in the optical quality is VA multilayer due to a change in optical thickness [P.K. Biswas, D. Kundu and D. Ganguli, “Preparation of wavelength-selective reflectors by sol-gel processing”, J. Mater. Sci. Lett., 6 (1987), 1481; Rabaste, J. Bellessa, A. Brioude, C. Bovier, J.C. Plenet, R. Brenier, A. Marty, J. Mugnier, J. Dumas, “Sol-gel manufacturing of thick Board applied to Bragg reflectors and microcavities”, Thin Solid Films, 416 (2002), 242].

Porous silicon multilayers obtained by electrochemical dissolution, with alternating layers of different porosity

The possibility of obtaining sets of porous silicon multilayers having different porosity, allows to produce structures with the given profile of the refractive index, which are an interference filter or a Bragg reflector. The refractive index of each layer shall be calculated in accordance with its porosity, which is created by electrochemical etching of silicon wafers in an alcohol solution of hydrofluoric acid. By adjusting the synthesis conditions such as the concentration of acid, electric current density and etching time, in addition to porosity is also possible to control the thickness and thus the optical properties of the [K. Kordás, A.E. Pap, S. Beke, S. Leppävuori, “Optical properties of porous silicon. Part I: Manufacturing and investigation of single layers”, Optical Materials, 25 (2004), 251; “Part II: Manufacturing and investigation of multilayer structures”, Optical Materials, 25 (2004), 257].

Porous silicon films are of interest because of their high specific surface area (200 m²/cm³), which is th can be used for collection and concentration of molecular particles, and significant changes in their optical and electrical properties when they interact with gases and liquids. An additional advantage of porous silicon systems is that their surface can be chemically modified in recognition of the specific and nonspecific elements [M. Arroyo-Hernández, R.J. Martin-Palma, J. Pérez-Rigueiro, J.P. Garcia-Ruiz, J.L. Garcia-Fierro, J.M. Martinez-Duart, “Biofunctionalisation of surfaces of nanostructured porous silicon”, Materials Science and Engineering, C23 (2003), 697; V.S-Y. Lin, K. Motesharei, K.-P.S. Dancil, M.J. Sailor, M.R. Ghadiri, “A porous silicon-based optical interferometric biosensor”, Science, 278 (1997), 840]. The above characteristics make these materials very suitable for chemical [V. Torres-Costa, F. Agulló-Rueda, R.J. Martin-Palma, J.M. Martinez-Duart, “Porous silicon optical devices for sensing applications”, Optical Materials 27 (2005), 1984; T. Gao, J. Gao, and M.J. Sailor, “Tuning the response and stability of mesoporous thin film silicon vapor sensors by surface modification”, Langmuir, 18 (25) (2002), 9953; Snow P.A., Squire E.K., P.S.J. Russell, L.T. Canham, “Vapor sensing using the optical properties of porous silicon Bragg mirrors”, J. Appl. Phys., 86 (1999), 1781] and biochemical sensors [V.S.-Y. Lin, K. Motesharei, K.-P.S. Dancil, M.J. Sailor, M.R. Ghadiri, Science, 278 (1997), 840].

The Sol-gel process, you can get a large number of layers in the Bragg reflectors without the problems of structural integrity inherent in the multilayer film, and the thickness and porosity of each layer can be controlled very precisely. The main problem of these materials is variable stability t is the treatment time. In the case of the application of porous silicon Bragg reflectors in air or water environment on the surface for several hours is formed oxide, resulting to increase their resistance to oxidation, they must be chemically modified.

The multilayers of the layers with ordered mesopores

The multilayer of this type are made of alternating deposition using methods of coating by centrifugation [S.Y. Choi, M. Mamak, G. Von Freymann, N. Chopra, G.A. Ozin, “Mesoporous Bragg stack color tunable sensors”, Nano Letters, 6 (2006), 2456] or coating by immersion [M.C. Fuertes, G. Soler-Illia, H. Miguez, patent application Spain No. 200602495] for the formation of layers with ordered mesopores, which receive, using a template or organic form, in combination with compounds that lead to an increase in the content of the inorganic phase in the solution-predecessor, which precipitated for forming each layer. The porosity of these layers makes it possible to change their optical properties when infiltration of liquids. In turn, the functionalization of the walls of the mesopores gives the opportunity to have this characteristic election in relation to a specific type or group of compounds.

The multilayers of colloidal particles

Please refer to the scientific literature [I.M. Thomas, “Single layer TiO₂and multilayer TiO₂-SiO₂optical coatings prepared from coloidal suspensions”, Applied Optics, 26 (1987), 4688], to the article, which States receive multilayers of alternating colloidal particles of TiO₂with dimensions that make up from 10 nm to 20 nm, and particles of SiO₂with a size of 10 nm. This method was used in the coating by centrifugation. However, in this paper, the microstructure of the material obtained is not described not described, it misopristol not shown, given only the optical characteristic of the reflection coefficient, which can be seen the maximum. Applications proposed in this article, focused on optical coatings with high thermal stability under irradiation of a powerful laser.

The explanation of the invention

Short description

The object of the present invention consists of a mesoporous multilayer structure with the properties of the Bragg reflector or a one-dimensional photonic crystal, hereinafter referred to as a multilayer structure based on nanoparticles according to the invention, which comprises periodically alternating layers with different refractive indices, each with a thickness factor of around 1 nm to 200 nm, and formed from nanoparticles. A multilayer structure based on nanoparticles according to the invention is precipitated on the substrate during the manufacturing process, can be used nanoparticles of several different materials give different refractive index of each layer and, therefore, different characteristics of each multilayer structure.

Another object of the present invention consists of a method of manufacturing a multilayer structure based on nanoparticles with properties of one-dimensional photonic crystal, hereinafter referred to as the method of the invention, which contains the following stages, which are:

a) prepare a suspension of particles of nanometric size, prisoner within 1-100 nm, which is the composition of any material that can be obtained in the form of nanoparticles, where the environment of the suspensions is any fluid in which these particles can become dispergirovannykh, and where their concentration is from 1% to 99%, and

b) form the structure of the invention by successive deposition on any substrate layers of controlled thickness of the nanoparticles on the basis of the suspensions described in (a), in such a way as to create alternating values of refractive index and thickness of each layer of the nanoparticles, which form the multilayer ranged from 1 nm to 1 μm, and where the number of layers of nanoparticles presented in the multilayer, can be in the range from 1 to 100 layers.

Another object of the invention is a multilayer structure on the basis of the nanoparticles according to the invention in a preferred and the expansion of optical elements are preferred for use, for example only, and without limiting the scope of the invention, in the touch devices, photoelectrochemical devices, non-ferrous coatings and reflective coatings.

Detailed description

The present invention is based on the fact that the inventors have found that on the basis of the new method, in which optically homogeneous layers of nanoparticles periodically alternated, you can get a new mesoporous multilayer structure having pores between 1 nm to 100 nm) with alternating refractive index and a high reflectance at different wavelengths. These properties of the Bragg reflector or a one-dimensional photonic crystal are observed in the ultraviolet, visible and near infrared regions of the spectra of electromagnetic radiation. This one-dimensional photonic crystal formed by layers having different refractive indices and controlled thickness, composed of nanoparticles can be deposited on substrates of various types using a simple and reliable method.

This periodic multilayer communicating with high porosity, which is accessible from the outside, having the properties of one-dimensional photonic crystal is formed by successive deposition of layers of oxide or semiconductor nanoparticles of controlled thickness so as to create a periodic cher is the investigation of the values of the refractive index. This alternation leads to the characterization of photonic crystal multilayer.

Periodic alternation of layers having different refractive indices, resulting in high reflectance, which can be easily detected by the naked eye and can be measured by spectrophotometer. Unlike other dense reflective structures of the mesoporous structure of the reflector is such that through it may be the diffusion of liquids. This leads to the possibility of changes in a controlled fashion color multilayer structure in accordance with the noise of the liquid and, consequently, produce material that can be used in the manufacture of the sensor. Proven properties of the nanoparticles of each of the layers that form the multilayer mean substantial qualitative structural contrast mesoporous multilayers produced in the past.

Thus, an object of the present invention consists of a mesoporous multilayer structure with the properties of the Bragg reflector or a one-dimensional photonic crystal, hereinafter referred to as a multilayer structure based on nanoparticles according to the invention, which comprises periodically alternating layers with different refractive indices, each with a thickness factor of around 1 nm to 200 nm, and formed from NAS the particles. A multilayer structure based on nanoparticles according to the invention is precipitated on a substrate in the manufacturing process, it is possible to use nanoparticles of several different materials give different refractive index of each layer and, therefore, different characteristics of each multilayer structure.

A specific object of the present invention consists of a multilayer structure based on nanoparticles according to the invention, which contains layers with nanoparticles of different materials (example 2, figure 3).

Another specific object of the present invention consists of a multilayer structure based on nanoparticles according to the invention, which contains layers with nanoparticles of the same material (example 3, figure 4).

The nanoparticles present in the multilayer structure on the basis of the nanoparticles according to the invention can be of any material, which can be obtained in the form of nanoparticles, comprising from 1 nm to 100 nm, and which allows to obtain the desired difference in refractive index between the layers. The material of the nanoparticles, for example only, and without limiting the scope of the invention, belongs to the following group: metal oxides, halides of metals, nitrides, carbides, chalcogenides, metals, semiconductors, polymers, or a combination of them. More preferably the, to the oxides selected from the group of inorganic oxides in their amorphous or crystalline phase; and most preferably, these materials selected from the group: SiO₂, TiO₂, SnO₂, ZnO, Nb₂O₅CeO₂, Fe₂O₃, Fe₃O₄V₂O₅, Cr₂O₃, HfO₂, MnO₂, Mn₂O₃, Co₃O₄, NiO, Al₂O₃, In₂O₃, SnO₂.

Specific implementation of this invention consists of a multilayer structure based on nanoparticles, in which the selected nanoparticles represent a material belonging to the following groups: SiO₂/TiO₂and SiO₂/SnO₂. Samples of structures formed of these nanoparticles, as shown in examples 1, 2, 4, 5 and 6.

Another specific object of the present invention consists of a multilayer structure based on nanoparticles according to the invention, which contains layers with nanoparticles of the same or different materials, but with different distributions of nanoparticles in size. The difference or equivalence of the size of the nanoparticles is determined by different porosity and given the different refractive index of each layer.

Specific implementation consists of a multilayer structure based on nanoparticles according to the invention, which contains layers with nanochemicals of the same material, for example, such as TiO₂but with different distributions of particles (example 3, figure 4).

Another object of the present invention consists of a multilayer structure based on nanoparticles according to the invention, which contains one or more violations of the periodicity of the layers. This multilayer structure based on nanoparticles has a spatial periodicity is disturbed by the presence of layers of greater depth or thickness than the layers that create the frequency, so that thus in one-dimensional photonic crystal formed of a defective optical state. In addition, in this multilayer structure based on nanoparticles according to the invention breach or rupture of the periodicity can be continued by incorporating layers of other thicknesses, for example from 1 nm to 200 nm, formed from nanoparticles of a different material and size and, therefore, having a different porosity.

On the other hand, the final properties of various mesoporous multilayer structures of the invention, which may be made, and these final properties should be determined in accordance with following required applications, controlled by the influence of the various parameters in the manufacturing process, which include:

a) the concentration of oxide particles in the initial suspensions, which pozvolyaet controlled by the thickness of each deposited layer, thus a clear example of the impact that changes in the concentration of colloidal suspensions predecessors on the optical properties shown in figure 1;

b) use one and the same material in the form of particles, but with different porosity, for obtaining the multilayer structures described in example 3, the result of which can be seen in figure 4;

(C) an intentional violation of the periodicity of the multilayer structure, which leads to the formation of optical defect States that are associated with particular optical properties;

d) the number of layers introduced into the structure, thus increasing the number of layers allows you to increase the intensity maxima of reflection, which are characteristic of multilayer structures with the properties of the photonic crystal (figure 2); and

e) deposition of layers at different speeds, which allows to obtain the spectra of reflectance in a wide wavelength range.

Another object of the present invention consists of a method of manufacturing a multilayer structure based on nanoparticles with properties of one-dimensional photonic crystal, hereinafter referred to as the method of the invention, which contains the following stages, which are:

a) prepare a suspension of nano-sized particles enclosed within 1-100 nm, which is the composition of any material, to the which can be obtained in the form of nanoparticles, where the environment suspensions is any fluid in which these particles can be dispergirovannykh, and where their concentration is from 1% to 99%; and

b) form the structure of the invention by successive deposition on any substrate layers with controlled thickness nanoparticles suspensions described in (a), in such a way as to create alternating values of refractive index and thickness of each layer of the nanoparticles, which form the multilayer ranged from 2 nm to 1 μm, and where the number of layers of nanoparticles presented in the multilayer can be in the range from 1 to 100 layers.

As mentioned earlier, the nanoparticles according to the method of the invention can be of any material, which can be obtained in the form of nanoparticles, comprising from 1 nm to 100 nm. Preferably, the materials used in the form of nanoparticles (or combination of materials) for deposition of multilayer structures with the properties of the photonic crystal, were the materials which provide the desired difference in refractive indices between the layers. Preferably, the composition can be a composition of any one of metal oxides, metal halides, nitrides, carbides, chalcogenides, metals, semiconductors, polymers, or combinations of them. Preferably, these materials were selected from the GRU is p: SiO ₂, TiO₂, SnO₂, ZnO, Nb₂O₅CeO₂, Fe₂O₃, Fe₃O₄V₂O₅, Cr₂O₃, HfO₂, MnO₂, Mn₂O₃, Co₃O₄, NiO, Al₂O₃, In₂O₃, SnO₂, CdS, CdSe, ZnS, ZnSe, Ag, Au, Ni, Co, Se, Si and Ge. Most preferably, the selected nanoparticles consisted of materials SiO₂, TiO₂and SnO₂. Samples of structures formed of these nanoparticles, as shown in examples 1, 2, 4, 5 and 6.

In dispersions or suspensions precursor to obtain thin layers of nanoparticles, which form a multi-layer structure using any dispersing agent as a liquid environment. In addition, preferably, this liquid medium was evaporated. It is preferable to choose this liquid medium from the group consisting of water, alcohols, aliphatic, alicyclic or aromatic hydrocarbons. It is more preferable to use water, ethanol, ethylene glycol and methanol, pure or mixed in any proportions, at a concentration by weight of compounds in the environment, which constitutes from 1% to 99%.

Suspension of precursor nanoparticles of various layers used in the method of the invention may be from the same or different materials and each layer that forms a part of the multilayer, depending on the use the of the nanoparticles of the same or different sizes may have different porosity, so it causes a different refractive index in each layer. If you receive this option, described in example 3.

The deposition of layers of (b) can be performed using different methods for each of these layers and can be performed by any method which allows to obtain layers of uniform thickness comprising from 2 nm to 1 μm, belonging, for example only, and without limiting the scope of the invention, to the following group: coating by centrifugation, coating by immersion and the method of Langmuir-Blodgett films. It is more preferable to use a method of coating by centrifugation, because it is usually used in obtaining thin layers of various materials and in the manufacture of planar devices.

On the other hand in connection with the task of creating controlled optical defect in a multilayer structure on the basis of the nanoparticles according to the invention, the defect or violation of the periodicity of the multilayer structure can intentionally be made at the stage b) deposition of layers by the method of the invention, for example, by placing a layer of greater thickness.

In the case of specific accomplishments that are performed in the present invention, was used crystals, such as substrate, which was cleaned and processed using known is the shaft means, which likewise can easily be executed by an expert in the area when the presence information of the present invention.

When a multilayer structure is treated after the General process outlined in the previous sections, get the multilayer properties of the Bragg reflector or a one-dimensional photonic crystal in a wide range of wavelengths (examples 1, 2, 3 and 4). In each case, the resulting reflectance largely will depend on the thickness of layers formed by nanoparticles of materials with different refractive indices. Specified thickness can be controlled by some parameters of the deposition process, such as the rotational speed of the substrate, using a method of coating by centrifugation, or by properties of the prepared dispersions of nanoparticles.

Violations of the periodicity of the multilayer structure (for example, to create optical defects in the volume) is obtained using suspensions of nanoparticles, prepared as described in (a). It is preferable to select from this group material, which allows to obtain the desired refractive index in the optical defect or impurity introduced in a multilayer structure. The sample obtained multilayer structure based on nanoparticles, in which the optical defect reprimes introduced in a controlled way, shown in example 5.

On the other hand, a multilayer structure based on nanoparticles according to the invention can be used as a starting material to improve the properties of the structure through changes or additions; such changes can be carried out by a specialist in the art on the basis of existing information about the current state of technology.

As described in example 6, the spectra of the reflectance of a multilayer structure of the invention can be modified by infiltration of the solvent with another indicator application through the structure, so therefore this structure can be used as an optical sensor for certain liquids.

Another object of the invention is the use of mesoporous multilayer structure based on nanoparticles according to the invention in the manufacture of preferably optical elements to be used preferably, for example only, and without limiting the scope of the invention, in the touch and photoelectrochemical devices, non-ferrous coatings and reflective coatings.

Another specific object of the invention is the use of mesoporous multilayer structure based on nanoparticles according to the invention, in which the optical element is a touch device is istwo for compounds in the liquid or gaseous phase or dispersed in the form of nanoparticles, it uses high soamsawali porosity multilayer structure based on nanoparticles and the dependence of its color from the refractive index of infiltrating connection. Various samples that illustrate this property, shown in this application in example 6.

Another specific object of the invention is the use of mesoporous multilayer structure based on nanoparticles according to the invention, in which the optical element is a colored coating for decorative or technological applications, such as reflective coatings in the interest of the wavelength range.

Another specific object of the invention is the use of mesoporous multilayer structure based on nanoparticles according to the invention, in which the optical element is a reflective coating in the interest of the wavelength range in photovoltaic and photocatalytic devices, and the implementation of the mirrors with high reflectance and yet porous can be used to improve their effectiveness.

These previously described coating can be used as a colored coating materials, for example ceramic materials.

Brief description of drawings

Figure 1. Spectra of the coefficient of specular reflections is ment for various one-dimensional photonic crystals, formed by layers with controlled thickness of nanoparticles SiO₂and TiO₂. In all cases, the multi-layer structure consisted of a set of 6 alternating layers of these materials obtained from dispersions of silicon dioxide with concentrations that ranged from 1 to 6 wt.%, and titanium oxide with a concentration of 5 wt.% in all the cases. Liquid medium of the slurry was a mixture of solvents with a ratio of 79% methanol and 21% water. The rotational speed of the substrate was fixed at ω=100 rpm/sec change the thickness of the deposited layers of silicon dioxide, controlled using the compositions of the suspensions, causes, as seen in the figure, the position of the photonic bandgap at different wavelengths.

Figure 2. Changing the optical characteristics of the multilayer structure with the properties of the photonic crystal. The change was obtained by sequential formation of 8 alternating layers of SiO₂and TiO₂while the number of layers is equal to (N). As you can see, increasing the number of layers in the system the maximum reflection narrows and grows in intensity. Used suspension contained silicon dioxide and titanium oxide in an amount of 5 wt.% in a mixture with methanol (79%) and water (21%). The speed used during the deposition process was about 100/S. in Addition, the images shown are p the pepper section of one-dimensional photonic crystal, obtained by scanning electron microscopy.

Figure 3. The coefficient (a) specular reflection and image (b)obtained by scanning electron microscopy, photonic crystal of the invention. A photonic crystal is a 6-layer one-dimensional crystal formed by layers of controlled thickness of nanoparticles of silicon dioxide and titanium oxide. Concentrations used suspensions amounted to 2% of silicon oxide and 5% titanium oxide at a content of methanol 79% and water 21%. The rotational speed of the substrate was about 100/sec using images obtained by scanning electron microscopy, it is possible to compare different thicknesses of deposited layers of silicon dioxide from the one shown in the previous figure.

Figure 4. Spectrum (a) reflection coefficient and obtained by scanning electron microscopy image (b) cross-section of the photonic crystal of the invention. A photonic crystal is a one-dimensional crystal, obtained by the sequential formation of layers of the same material with different porosity. This multilayer structure was obtained by alternation of 9 layers of titanium oxide contained in the amount of 8.5 wt.% (in the water), had a different distribution of particle sizes. The rotational speed of the substrate during the process wasp is Denia was about 125/S. The maximum reflection is narrower due to the smaller difference in refractive index between the layers, and, in addition, large reflection coefficients can be obtained in a wide wavelength range.

Figure 5. Spectrum (a) reflection coefficient and obtained by scanning electron microscopy image (b) cross-section of one-dimensional photonic crystal. The crystal was obtained by the sequential formation of layers of nanoparticles of titanium oxide and tin oxide. This multilayer structure was obtained using 7 alternating layers of both materials. In the case of TiO₂used suspension with a concentration of 5 wt.% with a mixture of 79% methanol and 21 vol.% water, and in the case of suspensions SnO₂used a concentration of 4.5% in water. The applied rotation speed was 100 rpm/s Similar morphology of the particles makes them difficult to distinguish, therefore, was applied to the analysis of the composition, it is possible to observe different contrast due to different deposited materials in each layer.

Figure 6. Spectrum (a) reflection coefficient and obtained by scanning electron microscopy image (b) for the photonic crystal multilayer structure in which the silicon dioxide embedded defect. Spectra of the reflection coefficients illustrate the optical characteristics of the multilayer of 6 words is in SiO ₂-TiO₂obtained from suspensions of silicon dioxide with a content of 3 wt.% and a titanium content of 5 wt.% when the methanol content 79% and water 21 vol.%, in addition, the defects of silicon oxide obtained in various thicknesses. With increasing thickness of the defect in a photonic forbidden band also increases the number of States of the defect. On the received scanning electron microscopy images show the cross-section of a multilayer structure in addition to the defect in the volume of the photonic crystal.

Figure 7. The change in optical characteristics of multilayer structures based on nanoparticles with properties of the photonic crystal with the infiltration of solvents having different refractive indices. This study was performed using a photonic crystal multilayer structure formed by the sequential formation of 8 alternating layers of SiO₂-TiO₂at a concentration of 5 wt.%, and photonic crystal, in which the amount of silicon dioxide was introduced defect in the formation used suspensions with concentrations of 3 and 5 wt.%, the defect has been threefold repetition of the deposition process. Used suspension contained a mixture of solvents with the content of 79% methanol and 21 vol.% water. In both cases, infiltrating the solvents were water, ethylene glycol and chlorobenzene. In more the spectra of the reflection coefficient shows the change in energy (eV) obtained on the basis of the refractive index of the solvent used in each case.

Examples of carrying out the invention

Example 1. A method of obtaining a multilayer structure with the properties of the photonic crystal, with a maximum reflectivity at 685±5 nm, when using colloidal nanoparticles of silica and titanium oxide.

In this example, a multilayer structure with high reflectivities were grown, alternating materials in the form of nanoparticles, which allowed us to obtain a large difference in refractive index between the layers. More specifically, the used amorphous silicon dioxide (34 wt.% in a colloidal suspension of Ludox, Aldrich) with a particle size in the range of 25-40 nm and crystalline titanium oxide (anatase phase). The latter was obtained in the form of nanoparticles in a colloidal suspension, synthesized after hydrolysis, condensation and peptization in the main environment and under hydrothermal conditions (120°C for 3 h). Used reagents were tetraisopropoxide (20 ml) of titanium (IV), water Milli-Q (36 ml) and 0.6 M hydroxide of Tetramethylammonium (3,9 ml). The resulting suspension was centrifuged as many times as it was necessary, at 14000 rpm for 10 min to eliminate the presence in the sample of possible fractions of units. Thus obtained suspension of nanocrystals OK the IDA titanium with a concentration of 24 wt.% had a particle size in the range of 5-15 nm. After obtaining colloidal suspensions of both oxides of the original dispersion, silicon dioxide and titanium dioxide, diluted with methanol and distilled water (if necessary) to achieve the oxide content of 5 wt.%. The final methanol content in both cases was 79%. Thus prepared suspension thoroughly homogenized and kept to use in the process of coating deposition by centrifugation.

Glass substrate with a size of 2.5 cm × 2.5 cm was prepared prior to the deposition process, purified and processed as follows: first, they were washed with distilled water, acetone and treated with ultrasound in carbon tetrachloride for 30 min; then they were washed with isopropyl alcohol, distilled water and again was treated with ultrasound in a mixture of sulfuric acid and hydrogen peroxide in a volume ratio of 4:1 for 1 h; and, finally, washed several times with distilled water. After all this processing of the substrate to be used, were thoroughly cleaned with ethanol and dried using a stream of nitrogen gas.

To obtain a multilayer structure on a glass substrate was prepared using a dispersion with a concentration of oxides 5 wt.% when the methanol content of 79%, and the rest was water. The substrate was placed in the holder, the image is and installation for coating by centrifugation, applied rotational speed of 100 rpm and was added to a suspension of silicon dioxide in a volume of 250 ml, supporting the rotation for 1 min after this addition. The same amount of nanoparticles of titanium oxide was distributed over the deposited layer of silicon dioxide, completely covering the surface of the substrate, and applies a rotational speed of 100 rpm for 1 minute of This process was repeated to obtain a total of 8 layers with alternating SiO₂and TiO₂when this was received photonic crystal with the desired multilayer structure.

Figure 2 presents the result in the form of optical characteristics, morphology and layer thickness in a photonic crystal multilayer structure obtained in this way. On figa) shows the dependence of the spectra of the reflection coefficients measured in the same zone of the photonic crystal, from the increasing number of layers. On fig.2b) shows the image of the cross section of the layered structure obtained by scanning electron microscopy (SEM).

Example 2. A method of obtaining a multilayer structure with the properties of the photonic crystal, with a maximum reflectivity at 445±5 nm, when using colloidal particles of silica and titanium oxide.

This example used the same colloidal suspension, as in the previous case. The use of R is slichnih concentrations of nitric oxide in the suspension and/or deposition of layers at different speeds allowed us to obtain spectra of reflectance in a wide wavelength range. In this case, it was possible to control the position of the Bragg peak, changing the concentration of the suspensions used for the deposition (more specifically, a dispersion of silicon dioxide), keeping other parameters constant. For this purpose were prepared suspension of silicon dioxide with a concentration of 2 wt.% and the mixture of solvents containing methanol 79% and water content of 21%. Used suspension of titanium oxide was identical to the suspension of example 1. Used glass substrates were prepared as already described. Obtained in this case, the results shown in figure 3 for multilayer grown by sequential formation of 6 alternating layers of SiO₂-TiO₂, you can see the different position of maximum reflectance (figa) compared with the previous example, and a smaller thickness of the layer of silicon dioxide shown their cross-sections, obtained by scanning electron microscopy (fig.3b). Thus, it was shown that changing the concentration of the suspensions used in the method of coating by centrifugation, the thickness of the layers is changed and accordingly the parameter grid of the photonic crystal, that in each case leads to a different optical characteristic.

Example 3. The method of obtaining a lot of launoy structure with the properties of the photonic crystal using the same material in the form of particles with different distributions of particle sizes.

This example used the colloidal suspensions of the same material, titanium oxide obtained by the process of synthesis at different temperatures. It was shown that the different distribution of particle sizes obtained by both processes of synthesis, lead to variations in the porosity of the material and, consequently, to different refractive indices; that is, using colloidal suspensions of the same material, you can get a one-dimensional photonic crystals with coefficients of reflection in a wide wavelength range. The method of synthesis used to obtain these suspensions, the same as described in example 1. One of the colloidal suspensions were obtained after hydrothermal synthesis at 120°C, is described in detail in this example, while another, with a different distribution of particle size was obtained using the same quantities of reagents, but after hydrothermal synthesis at 120°C., further heating is carried out at a higher temperature, more specifically at 190°C for 4.5 hours After this treatment at a higher temperature, the resulting suspension was centrifuged at 3000 rpm for 10 minutes In both cases, the titanium oxide was in the anatase crystalline phase. The resulting suspension with concentration of oxide 24 wt.% (120°C) and 16% (190°C) was diluted distiller the tub with water to a concentration of 8.5 wt.% in both instances.

A multilayer structure was obtained by alternation of suspensions prepared from nanoparticles of TiO₂obtained after synthesis at 190°C and 120°C respectively. In this particular case, the nanoparticles synthesized at 190°C and higher temperatures, and found that each suspension had a different distribution of particle sizes, and not just different mean value, which is crucial for obtaining the properties of the structure of the invention. A suspension of 250 ml was distributed on the processed substrates thus, as was described previously, and the rotation speed of 125 rpm was maintained for 1 min Results obtained after the sequential formation of 9 layers presented in figure 4. On figa) detailed characterisation in terms of the coefficient of specular reflection multilayer structure consisting of the same material shown in addition to the images obtained by scanning electron microscopy (fig.4b), where you can see the different morphology of the precipitated nanoparticles.

Example 4. A method of obtaining a multilayer structure with the properties of photonic crystals using colloidal nanoparticles of titanium oxide and tin oxide.

This example describes a method for multi-layered structures of materials, the difference in refractive indices is which is not so high, as in the case of silicon dioxide and titanium oxide. More specifically, in this example, colloidal particles of TiO₂-SiO₂used as a precursor patterns. A suspension of nanoparticles of titanium oxide were prepared from the suspension obtained at 120°C., diluting with methanol to achieve a concentration of 5 wt.%. On the other hand, colloidal particles of tin oxide was obtained using the method of forced hydrolysis at high temperatures, which promote the hydrolysis and condensation of aquacomplexes formed in solution. The synthesis was carried out by preparing a 0.5 l of a solution of 0.003 M (537 mg) chlorephenarimine tin (IV) in 0.3 M HCl. The aging of the solution in the heater for 2 h at 100°C led to an increase in the number of nanoparticles SnO₂and they were subjected to centrifugation and three-time washing with distilled water and re-dispersed in distilled water with a volume of 2 ml

A multilayer structure was obtained by alternation of colloidal oxides, titanium oxide and tin oxide, dispensing volume 250 ml glass substrate and applying a rotational speed of 100 rpm for 1 min To figa) shows the spectrum of the reflection coefficient obtained for the multilayer structure of 7 alternating layers of TiO₂-SiO₂together with the corresponding image (fig.5b)obtained by the method of skaniruesh the th electron microscopy. In this case, the similar morphology and size of the various nanoparticles did not allow to distinguish between the different thicknesses of each layer. It can be seen on the images re-dispersed electrons under electron microscope, more sensitive to the presence of materials with different electron density, such as TiO₂and SiO₂. This can clearly be seen on figs where different contrast in the pictures shows the alternation of materials and their respective thickness.

Example 5. A method of obtaining a multilayer structure having the properties of the photonic crystal, using colloidal nanoparticles of silica and titanium oxide, with a defect in the bulk of silicon dioxide.

In this example, it is shown that the violation of the periodicity of the photonic crystal multilayer structure of the invention can be obtained by introducing a layer with a greater thickness, which leads to defect States in photonic forbidden band; that is, in the forbidden zone appear wavelengths that can be skipped. In particular, this example describes a method for defect in the bulk of silicon dioxide, in the multilayer structure of the materials used in examples 1 and 2. In this case used a suspension of silicon dioxide and titanium oxide with a concentration of 3 and 5 wt.% accordingly, when the content is of canola 79%vol.

To obtain a multilayer structure, the applicant acted in a similar manner as described in previous sections relating to the multilayers of silicon dioxide and titanium dioxide, the frequency of rotation was fixed at 100 rpm/s was First grown multilayer formed by 6 layers of SiO₂-TiO₂; then on the last layer of TiO₂grown layer of silicon dioxide of greater thickness, which received a five-fold repetition of the deposition of this material. In conclusion, on the defect has grown a new multilayer, now titanium oxide and silicon dioxide, the same dispersion, to obtain a new 6-layer structure. In this way received a defect of silicon oxide within the multilayer structure, which can be seen in Fig.6. Range of the reflection coefficient measured for the multilayer structure formed by the sequential formation of 6 layers of SiO₂-TiO₂in the detail shown in figa), and also for different thickness defect of silicon dioxide within the multilayer obtained by repeating the deposition process of the same suspension three and five times. With increasing thickness of the defect in the bulk of silicon dioxide can be observed the increase of defect States in photonic forbidden band. In addition, fig.6b) shows obtained by scanning electron microscopy is zobrazenie cross-section of the multilayer and the defect in the bulk of silicon dioxide, inside the photonic crystal, obtained a five-fold repetition of the deposition process suspension with a silicon dioxide content of 3 wt.%.

Example 6. The change in optical characteristics of multilayer structures based on nanoparticles with properties of the photonic crystal with the infiltration of solvents with different refractive indices.

This example shows that the spectrum of the reflectivity of multilayer structures formed colloidal nanoparticles of silica and titanium oxide, may change after infiltration into the structure of solvents with different refractive indices. In particular, in this case there was a shift to larger wavelengths and a decrease in the intensity of maximum reflection, which become more pronounced at a higher refractive index of the used solvent. Various studies infiltration of solvent were performed after stabilization of the layered structure based on nanoparticles by heating at 450°C for 5 hours

Study of the change of optical characteristics was performed for multilayer structures obtained by precipitation of 8 alternating layers of silicon dioxide and titanium oxide described in example 1, and for multilayer structures with a defect in the bulk of silicon dioxide, obtained by the method described in example 5, was what showed the presence of two porosity, accessible from the outer side of the multilayer structures based on nanoparticles.

In the case of the layered structure 8 formed of alternating layers of silicon dioxide and titanium oxide, which was obtained from colloidal suspensions c content of 5 wt.% nanoparticles SiO₂and TiO₂, dispersive medium was a mixture of methanol (79%) and water (the remainder). The rotational speed of the substrate on which the besieged layers was 100 rpm/s study of the infiltration of solvents was performed, nakapila few drops them to the surface of the one-dimensional crystal, using a Pasteur pipette. The used solvents were water, ethylene glycol and chlorobenzene. When observing this process under an optical microscope, it was found the existence of infiltration in the multilayer, which was confirmed by the analysis of changing its optical characteristics. The characteristic of the reflection coefficient obtained for each filtered solvent shown in figa). On fig.7b shows the change in the position of maximum reflectance values (eV) of energy in accordance with the index (n_i) the refractive index of the solvent.

On figs) and (d) shows the results of a similar experiment carried out using a one-dimensional crystal with a defect in the bulk of silicon dioxide in the form of nanoparticles. As the op who was described in example 5, first was formed by a multilayer structure of 6 layers, alternating the deposition of nanoparticles of silicon dioxide, suspended in an amount of 3 wt.%, and nanoparticles of titanium oxide in an amount of 5 wt.%. Wednesday slurry was a mixture of methanol (79%) and water (the remainder). The rotational speed of the substrate on which besieged the layers was about 100/sec Then the last layer deposited TiO₂grown layer of silicon dioxide of greater thickness, which was achieved by three-fold repetition of the deposition of this material. In conclusion, using the same suspension, grew a new multi-layered structure of 6 layers of titanium oxide and silicon oxide. In this case, the infiltration of various solvents has led to the displacement of the minimum of the reflection associated with the state of the optical defect, which is a function of the refractive index of the solvent used.

Material and methods

Preparation of substrates

The substrate used in these cases, represent a plate of optical glass slides that were made in the form of squares with dimensions of 2.5 cm × 2.5 cm, washed with distilled water, acetone and treated with ultrasound in carbon tetrachloride for 30 minutes and Then washed with isopropyl alcohol, distilled water and again was treated Ultrazvuk mixture of sulfuric acid and hydrogen peroxide in a volume ratio of 4:1 for 1 h In conclusion, several times washed with distilled water. After all this processing used substrates were thoroughly cleaned with ethanol and dried using a stream of nitrogen gas.

The synthesis of nanoparticles

Colloidal nanoparticles of titanium oxide synthesized using the Sol-gel process, followed the process peptization in the main environment and under hydrothermal conditions. Used the titanium precursor was tetraisopropoxide (97%, Aldrich) titanium (IV). Given the high reactivity of these alkoxide predecessors to water manipulation was carried out in an inert atmosphere. Once in these conditions, the precursor to the desired number was obtained and properly hermetically sealed, the rest of the experimental process was performed in an uncontrolled atmosphere. Thus, 20 ml of tetraisopropoxide titanium (0,0652 mol) was poured in 36 ml of water Milli-Q (2.02 mol) was subjected to magnetic stirring in a beaker, placed on a plate for mixing. Stirring is maintained for 1 h, and then the resulting suspension was filtered using filters from Millipore, code RTTP, with a pore size of 1.2 μm. Solids collected during filtration, washed three times with distilled water, in portions of 10 ml TBE the Fe particles, obtained after the washing process, collected and placed in a Teflon chemical glass hydrothermal synthesis, which was added to the hydroxide of Tetramethylammonium (~2.8 M, Fluka), more specifically to 0.6 M Tetramethylammonium (0,0024 mol) volume of 3.9 ml of the Mixture was thoroughly homogenized, gently stirring with a glass rod for stirring, and then was subjected to hydrothermal synthesis in the heater at 120°C for 3 hours after this time got a transparent colloidal suspension of titanium oxide pale blue color in the anatase crystalline phase, which was centrifuged at 14000 rpm for 10 min to eliminate the presence sample of possible fractions of units. If necessary, this process should be repeated many times to establish the fact of the absence of aggregates. The concentration by weight of oxide in the suspension was calculated by drying results in the heater at 60-100°C for 2-3 h, and in such case it was about 24-25 wt.%.

Synthesis of nanoparticles of TiO₂with a different size distribution compared with the previous (and, consequently, with different porosities and different refractive index) was carried out using the same Sol-gel process, followed by peptization process in the main environment and under hydrothermal conditions, to which was added the growth process of the particles in hydrotermal the s conditions at a higher temperature, more specifically, at 190°C for 4.5 h of the Experimental process identical to the process described earlier, used the same reagents and the same concentration. Received whitish suspension of titanium oxide (anatase) was centrifuged at 3000 rpm for 10 min to eliminate aggregated fractions. The concentration by weight of oxide, calculated according to the results of the drying heater at 60-100°C for 2-3 h, was 14-17 wt.%.

Colloidal particles of tin oxide was obtained by way of forced hydrolysis at high temperatures. Aquacomplex formed in solution, hydrolyzed and condensed over time, it is very slow reaction at ambient temperature can be accelerated by increasing temperature. Properties of the obtained precipitated in the sediment particles depend on such factors as concentration of reactants, pH, aging time and the properties of ions present in the solution. Used by the predecessor tin was pytevodniy chloride (98%, Riedelde Haën) tin (IV), dissolved in acidic solution, in particular in HCl (37%, Fluka). Prepare a solution of tin chloride in the amount of 0.5 l of 0.3 M diluted HCl. The final concentration of tin in solution was 0,003 M, which was dissolved 537 mg (0,0015 mol) of the compound. The prepared solution was poured into a glass tank, zakrya the text of the tube, for further aging it in the heater at 100°C for 2 hours after this time the resulting suspension was cooled in a water bath and centrifuged at 8000 rpm for 10 minutes, removing the settled layer of a solution. The obtained solid particles re-dispersible in distilled water using an ultrasonic bath. This process was repeated three times. After the last centrifugation, the particles re-dispersible in distilled water with a volume of about 2 ml Concentration by weight of oxide in the suspension was calculated by drying results in the heater at 60-100°C for 2-3 h, and it was 4-5 wt.%.

Required variance for the deposition process in the coating by centrifugation was obtained by diluting the thus obtained nanoparticles in different solvents.

Preparation of colloidal suspensions

The materials used in the form of particles to obtain a multilayer structure with the properties of the photonic crystal are those that allow you to get the difference in refractive index between the layers. As described earlier in this invention are colloidal particles of three types: oxides of titanium, silicon and tin.

Suspension-predecessors used to obtain layers of controlled thickness with various indicators Prelom the tion, obtained by diluting solvents, based on the suspensions obtained after the synthesis process, described in detail in previous sections. More specifically, the suspension of nanoparticles of titanium oxide and tin oxide were obtained by dilution with distilled water and/or methanol (purity for high-performance liquid chromatography from Multisolvent) in different proportions. In both cases, during the coating process by centrifugation final concentration used oxide was 1-10 wt.%. Colloidal particles of amorphous silicon dioxide are available for purchase (colloidal silica LUDOX TMA from Aldrich) aqueous suspension with a concentration of 34 wt.%. These dispersions also dilute the previously mentioned mixture of solvents to achieve a concentration of silicon dioxide, a component of 1-6 wt.%.

Obtaining a multilayer structure based on colloidal suspensions

One-dimensional photonic crystal was obtained by repetition of the deposition of layers of nanoparticles, alternating materials with different refractive indices. Important factors to control the thickness of the layers and, consequently, the spectra of the reflection coefficient obtained in each case are, among other things, the concentration of the used suspension and engine speed during the coating process covered the I by centrifugation. This method can be obtained multilayer structure with the properties of the Bragg reflector in a wide wavelength range.

To obtain a multilayer structure used previously processed glass substrate, cleaned with ethanol and dried using a stream of nitrogen gas. These substrates were placed in the sample holder installation (Novocontrol GMBH) for coating by centrifugation, which operated at atmospheric pressure, acting then as follows: suspended dispersion precursor of 250 ml is prepared in a solvent mixture, carefully covered the entire surface of the substrate and the applied frequency of rotation, comprising about 80-130/s, for 1 minute

Obtaining a multilayer structure of SiO₂-TiO₂started with the deposition of silicon dioxide on a substrate using suspensions with concentrations of SiO₂from 1 to 6 wt.% in solvent mixture (21% vol. water and 79% methanol). Distributed volume of the suspension and used the frequency of rotation, comprising about 80-130/C for 1 min. Then similarly did with the suspension of titanium oxide with a concentration of 5 wt.%, prepared by dilution with methanol slurry obtained by the hydrothermal synthesis at 120°C. the Desired multi-layer structure was obtained by alternation of suspensions of silicon dioxide and titanium oxide, recip is I higher reflection coefficients when the number of deposited layers. The use of different concentrations of the dispersions of silicon dioxide and/or deposition of layers at different speeds allows to obtain spectra of reflectance in a wide wavelength range.

In the case of multilayers formed of TiO₂-SiO₂the variance in these volumes are suspended at a concentration of titanium oxide 5 wt.%, diluting with methanol after synthesis at 120°C and at a concentration of tin oxide 4.5 wt.%, diluting with distilled water.

In the case of obtaining a multilayer structure of titanium oxide has been similarly described above for SiO₂-TiO₂. The required volumes of suspensions of TiO₂having a concentration of 8.5 wt.%, obtained by hydrothermal synthesis at 120°C. and 190°C. after dilution with water, was distributed on the substrate. Alternating suspension of titanium oxide with different distribution of particle sizes, obtained differences in refractive indices and, therefore, one-dimensional photonic crystal.

Characterization of the obtained multilayer structure (field emission scanning electron microscopy, optical mirror reflection coefficient)

For multilayer structures obtained as described above was determined by structural characteristics, using the method of scanning electron microscopy, and optical performance is key in the reflection in the visible or near infrared range of the spectrum of electromagnetic radiation, it was observed a significant part of the properties of photonic crystals. Spectra of the reflection coefficient was measured using the equipment infrared Fourier-transform spectroscopy from Bruker attached to the microscope, which used an objective lens with 4x magnification, with a numerical aperture of 0.1 (the angle of the light cone ±5,7°). Image by scanning electron microscopy of various cross-sections of the samples were obtained using a field emission microscope Hitachi.

1. Mesoporous multilayer structure with the properties of the Bragg reflector or a one-dimensional photonic crystal, characterized in that it contains a periodically alternating layers composed of nanoparticles with different indices of refraction, each layer constituting from 1 nm to 200 nm.

2. Multilayer structure based on nanoparticles according to claim 1, characterized in that it contains layers with nanoparticles of various materials.

3. Multilayer structure based on nanoparticles according to claim 1, characterized in that it contains layers with nanoparticles of the same material.

4. Multilayer structure based on nanoparticles according to claim 1, characterized in that the nanoparticles can be of any material, which can be obtained in the form of nanoparticles with a size comprising from 1 nm to 100 nm, and which allows to obtain the desired discern what in the refractive index between the layers.

5. Multilayer structure based on nanoparticles according to claim 4, characterized in that the material of the nanoparticles belongs to the following group: metal oxides, halides of metals, nitrides, carbides, chalcogenides, metals, semiconductors, polymers, or a combination of them.

6. Multilayer structure based on nanoparticles according to claim 5, wherein the oxides are selected from the group of inorganic oxides in their amorphous or crystalline phase.

7. Multilayer structure based on nanoparticles according to claim 5, characterized in that the material of the nanoparticles are selected from the following group: SiO₂, TiO₂, SnO₂, ZnO, Nb₂O₅CeO₂, Fe₂O₃, Fe₃O₄V₂O₅, Cr₂O₃, HfO₂, MnO₂, Mn₂O₃, Co₃O₄, NiO, Al₂O₃, In₂O₃, SnO₂, CdS, CdSe, ZnS, ZnSe, Ag, Au, Ni, Co, Se, Si and Ge.

8. Multilayer structure based on nanoparticles according to claim 5, characterized in that the material of the nanoparticles are selected from the following group: SiO₂/TiO₂and SiO₂/SnO₂.

9. Multilayer structure based on nanoparticles according to any one of claims 1 to 3, characterized in that it contains layers with nanoparticles of the same or different materials, but with different distributions of nanoparticles by size.

10. Multilayer structure based on nanoparticles according to claim 9, characterized in that it contains the layers with nanoparticles of a material TiO ₂and has a different distribution of particle sizes.

11. Multilayer structure based on nanoparticles according to any one of claims 1 to 3, characterized in that it contains one or more violations of the periodicity of the layers.

12. Multilayer structure based on nanoparticles according to claim 11, characterized in that the violation of the frequency due to the presence of another layer of depth or thickness as compared with the layers that define the specified interval.

13. Multilayer structure based on nanoparticles according to item 12, characterized in that the disturbance or interruption frequency accompanies the use of nanoparticles of various materials.

14. A method of obtaining a multilayer structure based on nanoparticles according to any one of claims 1 to 13, characterized in that it comprises the following stages, which are:
a) prepare a suspension of nanoparticles, the composition of which is the composition of any material that can be obtained in the form of nanoparticles, where the environment of the suspensions is any fluid in which these particles can be dispergirovannykh, and where their concentration is from 1% to 99%; and
b) forming a multilayer structure with two high porosity and properties of one-dimensional photonic crystal by successive deposition on any substrate layers of controlled thickness of the nanoparticles on the basis of the suspensions described in (a), thus, to generate the alternating values of the refractive index and the thickness of each layer of the nanoparticles, which form the multilayer ranged from 1 nm to 1 μm, and where the number of layers of nanoparticles presented in the multilayer may vary from 1 to 100 layers.

15. The method according to 14, characterized in that the suspension of precursor nanoparticles and can be of any material in the form of nanoparticles with a size comprising from 1 nm to 100 nm, and which allows to obtain the desired difference in refractive index between the layers.

16. The method according to item 15, wherein the nanoparticles suspension predecessors different layers and can be from the same or different materials, and each layer in the multilayer, part of which it forms, may have different porosity due to the use of the same or different sizes of the nanoparticles, so that it thus causes a different refractive index in each layer.

17. The method according to item 15, characterized in that the deposition of layers of (b) is carried out, using a method which allows to obtain a layer of uniform thickness comprising from 2 nm to 1 μm.

18. The method according to item 15, characterized in that the deposition of layers of (b) carry out, supporting periodicity throughout the structure or creating bre is of the specified characteristic or defect.

19. The method according to p, characterized in that the disturbance frequency or defect patterns create the presence of a layer of a different thickness compared to the thickness of the remaining layers.

20. The method according to 14, characterized in that the deposition method belongs to the following group: coating by centrifugation, coating by dipping, and the method of Langmuir-Blodgett films.

21. The method according to 14, characterized in that the deposition method is a coating by centrifugation.

22. The use of multilayer structures based on nanoparticles according to any one of claims 1 to 13 in the manufacture of optical elements.

23. The application of item 22, wherein the optical element is a sensor device for compounds in the liquid and gaseous phase or dispersed in the form of nanoparticles, using high soamsawali porosity multilayer structure of the nanoparticles and the dependence of its color from the refractive index of infiltrating connection.

24. The application of item 22, wherein the optical element is a colored coating for decorative or technological application, as in the case of reflective surfaces in the interest of the wavelength range.

25. The application of item 22, wherein the optical element is a accounted for the total coverage of interest the range of wavelengths in photovoltaic and photocatalytic devices, when this realization mirrors with high reflectance and yet porous can be used to improve their effectiveness.