WO2005012857A1

WO2005012857A1 - Apparatus for simultaneous or consecutive characterization of multiple solid material samples by photoluminescence

Info

Publication number: WO2005012857A1
Application number: PCT/ES2004/070061
Authority: WO
Inventors: Avelino CORMA CANÓS; Hermenegildo GARCÍA GÓMEZ; José Manuel SERRA ALFARO
Original assignee: Consejo Superior De Investigaciones Científicas; Universidad Politécnica De Valencia
Priority date: 2003-08-01
Filing date: 2004-07-27
Publication date: 2005-02-10
Also published as: ES2223296A1; ES2223296B1

Abstract

The invention relates to an apparatus for characterization using photoluminescence techniques of multiple solid material samples, comprising at least irradiation means (6,7,8,14) for applying at least one controlled radiation to the samples (1), at least one support (2,3,4,15) housing a plurality of samples (1) and detection and registering means (9,10,11,16) of the photoluminescence radiation produced by the samples (1) arranged on the support (2,3,4,15) as a result of the preceding irradiation. The apparatus enables multiple characterization of large libraries of solid materials by means of photoluminescence measures, particularly fluorescence, which do not alter the properties of the solids, of which only small amounts are required, thereby making it possible to increase the number of new materials that can be characterized within a given time.

Description

TITLE

AN APPLIANCE FOR THE SIMULTANEOUS OR CONSECUTIVE CHARACTERIZATION OF MULTIPLE SAMPLES OF SOLID MATERIALS BY PHOTOLUMINISCENCE

TECHNICAL FIELD OF THE INVENTION The present invention belongs to the field of photoluminescence techniques and is particularly applicable to the sector of solid material sample characterization, and especially to the analysis of solid catalysts, in order to determine the presence and distribution of luminescent elements. in different positions of the solid structure.

STATE OF THE PRIOR ART OF THE INVENTION In the development of new materials, characterization techniques based on spectroscopic techniques are of great importance both in the field of fundamental research and in that of applied research. The information provided by spectroscopic techniques to determine the composition and properties of solid materials, may be related to the activity of these solids in many fields such as the catalysis of chemical reactions and their ability to act as semiconductors. The characterization of the surface and of the total of the particle of materials is of great help at the time of the design, development and optimization of new catalysts of industrial interest and of materials with applications in photonics, semiconductors, solar cells and electroluminescence. Photoluminescence is a spectroscopic characterization technique that consists of recording the light that is emitted by a substance when it is previously excited by electromagnetic radiation from the region. visible ultraviolet (200-800 n). This phenomenon is based on the fact that the absorption of a quantum of light energy produces the excitation of the substance from the electronic level of the fundamental state to electronic levels of greater energy, which have an extremely short life time and relax until the first state excited singlet. This excited singlet state has a typical life time on the nanosecond scale and can suffer deactivation in several ways. One form of deactivation consists in the non-emissive internal conversion in which the excited state of the lowest energy singlet reverts to the fundamental state through intermolecular collisions and / or link vibrations dissipating electronic energy such as mechanical energy and heat. Another alternative form called 'intersystem crossing' consists in the transformation of the singlet state into a triplet state of lower relative energy, which due to the violation of the conservation of the spin, has a much longer life time. A third deactivation pathway occurs when bonds are broken and the excited group is transformed into another chemical species. Of particular relevance in the present invention, it is a fourth deactivation mechanism consisting of the emissive deactivation of the excited states, both singlet and triplet, to the fundamental state. These phenomena are known, in general, with the name of 'photoluminescence' or, more specifically, 'fluorescence' when the electronic transition is between singlet excited states, or 'phosphorescence' when the electronic transition is between an excited triplet state and a singlet . The fundamental differences between fluorescence and phosphorescence are two: the fluorescence is generally much more intense than the phosphorescence and in addition the temporal profile of the fluorescence is much faster than that of phosphorescence Thus, when observing phosphorescence, temperatures below room temperature are generally required, working at the temperature of liquid nitrogen (77 K). The decrease of the temperature favors the deactivation by means of an emissive process of relaxation in front of the deactivations that require collisions and vibrations. Photoluminescence as a material characterization technique provides information on the presence of certain functional groups "lumó forums" in the substance, allowing to determine their presence, quantify their number, establish their distribution in different populations and determine the chemical and structural environment of these groups . Photoluminescence has generally been applied to characterize molecular substances in solution, but more recently [Corma et. al, Chem.

Commun. 20 (2001) 2148-2149; Corrent et al. Chem. Mat. 13

(2001) 715-722] has been applied to the characterization of solid samples. Photoluminescence as a characterization technique also has wide advantages over other techniques: these are non-destructive measures that do not alter or modify the material, with high sensitivity and high speed. In recent years, the development of new accelerated catalytic test techniques is leading to a revolution in the field of heterogeneous catalysis, this field being called combinatorial catalysis (Senkan, SM, Nature, 394 350-353; Senkan, S.., Ange andte Chemie Int. Ed. 2001, 40, 312-329), which is providing innovative techniques and methods (US-A-5,959,297, US-A- 6,004,617, WO-A-99/21957) for the rapid and simultaneous test of large catalyst libraries. In view of the interest of these combinatorial catalysis methodologies, it is convenient to find new Accelerated techniques for the physical / chemical characterization of these materials that allow to achieve a greater knowledge of their composition and properties, and consequently, that allow to improve the process of development and optimization of these materials for a given application in the aforementioned fields.

DESCRIPTION OF THE INVENTION The object of the present invention is to provide an apparatus for the multiple characterization of large libraries of solid materials by means of photoluminescence measurements, which do not alter at all the properties of the solid of which small quantities are necessary, which allows increasing the number of new materials to characterize. Another object of the invention is to provide a high capacity characterization technique for solid materials with application such as catalysts, photonic materials, semiconductors, electroluminescent or solar cells etc., based on photoluminescence measurements. According to the invention, these objects are achieved by an apparatus for the characterization by photoluminescence techniques of multiple samples of solid materials, which comprises at least irradiation means to apply at least one controlled radiation to the samples, at least one support for housing a plurality of medium samples for detecting and recording photoluminescence radiation produced by the samples arranged in the support as a result of their previous irradiation. The irradiation means may be designed to apply a simultaneous or consecutive excitation irradiation of a sample library, at least one light source being among these means, such as a lamp or a laser device, the presence of means for selecting a wavelength or a determined range of wavelengths of the spectrum produced by the light source; and of means to properly focus the excitation radiation, previously conditioned, on one or more solid samples. In a preferred embodiment, the system also comprises means for the simultaneous detection of a given range of wavelengths of the emission radiation of the excited samples; system to separate the emission in the wavelengths that compose it (monochromator); means for focusing the radiation from the samples on the detector device. - means for recording and analyzing the information generated through the detection of the luminescence radiation produced by the plurality of irradiated materials The means for generating the radiation will preferably be composed of a mercury lamp, with a range of lengths of 200-800 nm wave, or by one several lasers of fixed or variable wavelengths in a certain range. These lasers can be continuous or pulsed and will preferably emit UV light, among these may be gaseous lasers such as those of different nitrogen or solid excimers such as Nd-YAG or liquids such as dyes. Preferably, the radiation that reaches the samples should be in the range of 250-350 nm. This may require the use of bandpass filters. Another desirable aspect of incident radiation on the sample or samples is that the rays of the electromagnetic waves have parallel directions, that is, that it is a collimated radiation. For this purpose, the use of a collimator is necessary. Examples of collimating devices are: quartz or pyrex biconvex glass lenses. Optical means can also be useful for focusing the radiation on a given surface, which must include at least one sample of the set of samples arranged in the support. A support for multiple luminescence characterization of solid materials comprises a plurality of locations for the deposit of at least one sample at each location, a support, preferably flat, with a sample holder surface comprising the locations for the samples, each location being defined in a predetermined position, and At least part of the locations may be distributed on the sample holder surface, in parallel, sectorially or spirally or concentrically around an axis. Also, in one embodiment of the support, at least part of the samples is deposited in the locations on the sample holder surface in the form of thin solids film. The material of which the sample holder is constituted must withstand, without deforming or undergoing changes in its structure, at the temperatures that are applied when analyzing the samples deposited therein and transparent to UV-visible radiation, in the range both of excitation radiation as emission in photoluminescence. A useful support for almost all of the temperature ranges that are applied in tests and characterizations of this type, can be manufactured in a heat-resistant material at temperatures between -200 to 600 ° C and transparent to UV-visible radiation. The support and the apparatus of the invention make it possible to make an advantageous system that allows efficient characterization of solid materials, based on simultaneous or successive photoluminescence measurements. Thus, the support can accommodate a plurality of material samples on its surface, these being in the form of bonded films of different thicknesses, powders of varied granulometry or pellets, the surface being suitably shaped to accommodate the plurality of solids. In the case that the materials are in the form of a film, the different materials can be manufactured / deposited continuously, so that the support is covered by a film whose composition varies depending on the position. In another embodiment, the support can also be inside a sealed chamber, in order to keep the samples arranged in contact with a medium, preferably gaseous, fully controlled, as well as being able to perform measurements at pressures higher or lower than atmospheric pressure. . The camera must be totally transparent or have transparent windows to radiation, both excitation and emission, conveniently located. In one embodiment of the apparatus of the invention, the control means comprise thermal regulation means capable of maintaining the samples at a temperature in a range from -200 ° C to 600 ° C, for regulating the pressure and chemical composition of the atmosphere in contact with the samples. Concerning the means of detecting photoluminescence radiation, for the detection of photoluminescence radiation a photomultiplier or fine CCD (charge-coupled device) (US

6,339,633, US 6,335,757 or EP1168833). Matrices of photomultipliers can also be used. These devices allow the detection, that is to say, the transformation of the photons, of the radiation coming from a surface, into electrical impulses in a resolved way both spatially and temporarily, being therefore possible the simultaneous registration (CCDs and arrays of photomultipliers) or consecutive (photomultiplier) of the intensity for one of the locations where the excited samples are found, over the time during which the photoluminescence occurs Also, the registration of the photoluminescence spectrum of each sample is relevant, that is, the recording of the light intensities for each of the wavelengths that integrate the photoluminescence radiation of a material. For this, it is necessary to have a specific device, such as: - means to decompose the radiation in its different wavelengths and its subsequent detection. An example is the use of an optical prism or a diffraction network, which decomposes the beam emitted spatially in each component that integrates it and then these components are detected simultaneously using a CCD device. The CCD device measures the light intensity at each point (pixel) of the screen. This system performs a separation of the emission wavelengths through their spatial separation. - Means in which a narrow range of wavelengths is selected in a period of time, that is to say, for monochromarx the radiation beam and subsequently detect it, so that by varying the selected wavelength over time, this system performs a separation of the components of the temporarily resolved beam. In this regard, there are integrated CCD-monochromator systems that allow obtaining the spectral information (Intensity vs. Lambda) for very short time intervals (of the order of peak seconds), compared to the total photoluminescence process time, for each pixel of the CCD camera. By using optical fibers that collect, concentrate and focus the light of each location and direct and divide it into several beams of equal intensity, it is possible to develop a system that has several types of detection, so that spectra can be registered simultaneously of photoluminescence and, in another detector, perform measurements of temporal decay of the signal. Also required are: - means to focus the signal from the radiating sample or samples and transmit that radiation properly to other optical or detection devices. These can be lenses or optical fibers. - means to collimate the photoluminescence radiation - means to prevent the radiation produced by a sample from reaching the detector arranged to detect another different sample, that is, means to prevent radiation contamination between samples and the environment. An example of this would be the use of a structure that absorbs or reflects the radiations of a sample that were not in the direction of the target detector for that sample and that could affect the detector of another sample, interfering with the correct measurement of this other sample. - means for filtering wavelengths that are in the range of excitation radiation and must not reach the detector. Modes of realization of the invention and description of the associated method for the execution of the characterization process by photoluminescence. The configuration of the apparatus object of the invention can be varied depending on whether the characterization process is carried out simultaneously or sequentially for all samples and whether they are opaque or transparent samples. If the characterization process is carried out sequentially, that is, that the experiment is carried out in one or several different samples from time to time, means are necessary that allow irradiating and detecting alternately samples that are currently being characterized. For this, at least - mechanical and / or optical means are available that allow the movement of the irradiation system and / or detection system to perform the photoluminescence test on one or several samples. - mechanical means that allow the movement of the support to position one or several specific samples in the area of action of the irradiation and detection systems For the movement of the support (rotating and / or linear) means such as stepper motors may be necessary . Likewise, mechanical and optical means are required for the movement of the radiation beam or beams to ensure the control and accuracy of the position or positions irradiated at all times. If the characterization process is carried out simultaneously for all the samples that the support houses, that is, all the samples are excited at the same time and the photoluminescence radiation is detected and recorded simultaneously for all the samples, it is necessary that the media of irradiation and detection can act on All samples. In this regard there are CCD cameras with sufficient number of pixels to capture an image of the medium where the information of the fluorescent light intensity of each sample is captured in one or several pixels of constant coordinates. From the point of view of the geometric arrangement of the components of the system in the case of opaque samples, the irradiation and detection means must necessarily be located on the same side of the support where the samples are, geometry of the type face face geometry. In this way, it is possible to detect photoluminescence radiation that produces the same sample surface that had been previously excited. In the case of transparent samples, the detection means can be placed on both sides of the support, since the photoluminescence radiation can pass through the samples and the same support material. The control means may also include means for regulating gaseous fluids to control the composition of gaseous fluids in contact with the surface of the support and / or the samples. They may also contain means for the control of the pressure at which the samples are located, for this purpose there will be pressure meters and vacuum pumps and / or gas pressure vessels, allowing measurements to be made under reduced pressure or overpressure. Samples may be heated or cooled simultaneously at temperatures between -200 and 600 ° C. Being able in this way to carry out the measurements at the same time that chemical reactions can be carried out in if you. The apparatus of the present invention may also comprise

* magnetizing means to be able to subject the samples to a magnetic field, either constant or variable; I

* means to subject the samples to an electric field, either constant or variable; I

* irradiation means comprising at least one laser emitting device that preferably comprises adjustment means for modifying the frequency or range of laser emission frequencies; I

* polarized light generating means. The reading signal of the response to irradiation of the different materials can be corrected with targets to avoid the influence of the sample holder material. A remarkable embodiment of the present invention is the possibility of carrying out the radiation process when the support with the different solid materials is in the presence of a certain atmosphere (gases, vapors), which can be static or renewed thanks to a flow of said gases or vapors, and of constant or variable composition. In this way, it is also possible to track in situ the interaction of the solid with the different molecules, and even if there is a chemical reaction, indirectly determine the catalytic activity of each of the plurality of materials. For this purpose, the system has the necessary means to be able to control and regulate the temperature of the materials, as well as means to regulate the pressure (vacuum or overpressure) in the chamber where the support with the materials is located. In this way, the use of probe molecules is possible, which allows the study of the interaction of the different solids with them. Likewise, the means to regulate the temperature, pressure and type of atmosphere in which the materials are found, can be used for different physical / chemical treatments of the set of materials prior to photoluminescence characterization. The light emitted in photoluminescence, which corresponds to the transition between excited states and the fundamental state, contains different wavelengths, typically between 200 and 1500 nanometers, the photoluminescence spectrum being called the determination of the relative intensity of emission versus the length of wave. To obtain the electronic excitation and therefore the appearance of the photoluminescence, the illumination of the sample with a radiation of suitable wavelength is required, usually in the range of the visible ultraviolet. The general way to determine the optimum excitation length is to observe the band maximums in the visible ultraviolet absorption spectrum. Related to the selection of the optimum excitation length there is a variant of the photoluminescence in which the detector is set at an emission wavelength while scanning all excitation wavelengths. The excitation wavelength always has to be shorter than the emission wavelength. The record that is obtained is known as the excitation spectrum and provides information on the emission intensity for each excitation wavelength. On the other hand, there are variants (fluorescence maps) in which emission spectra recorded for all excitation lengths are arranged in a parallel axis, the emission intensity corresponding to the Z axis, and in the perpendicular axis the excitation spectra. These photoluminescence maps contain the maximum possible information regarding emission and excitation. The determination of the optimal wavelength for the excitation of a solid sample is performed in another device, not object of the present invention. To perform the multiple test on the device object of the present invention, the wavelength that best suits the set of different materials to be characterized is selected. With respect to the temporal profile of the emission there is a photoluminescence technique called single photon counting in which the excitation occurs by means of a light pulse coming from a flash lamp or a laser, being the Pulse duration much shorter than the lifetime of the excited state. Typical pulse durations are in the PS area (10 ^{~ 12} seconds). This excitation of the sample causes the emission and what is recorded is how the intensity of light from the photoluminescence decreases compared to the time elapsed since the pulse. In the single photon counting technique, the photoluminescence time profile is constructed by detecting the time of arrival at the detector of the first emission photon and repeating the pulse (excitation / registration of the first emission photon that reaches the detector) a number of Statistically significant times, and that can generally be around 10,000 accounts. The adjustment of the temporal profile of the photoluminescence to kinetic equations allows to establish the distribution of the different families that contribute to the emission (light groups). Photoluminescence as a technique of structural characterization generally provides two types of information. The first of these is the presence or absence of certain luminous groups that are responsible for the appearance of photoluminescence. Through this first information it is possible to monitor the appearance / disappearance of these groups during the synthesis of a material or subsequent treatment, its temporal evolution and the arrival to a stationary state. For example, during the formation of a material, the recording of the photoluminescence from the sample by measuring the overall intensity of photoluminescence (emission area) allows the determination of how these luminous groups are formed. On the other hand, by determining the temporal profile of the photoluminescence and its adjustment to kinetic equations that contain a series of exponential terms corresponding to first-order kinetics it is possible to know how many populations of the same luminous group exist in the sample, which is the relative proportion of each of them and by determining the half-life time to discuss the chemical environment in which the light group is located in the material. As an example, which illustrates the possibilities of photoluminescence in the characterization of solids with application as catalysts, the case of the Ti / MCM-41 material is discussed below. In this case, when the solid is excited, an emission is observed whose spectrum has a maximum of 490 manometers and which is due exclusively to the emission from tetrapodally coordinated titanium atoms to the silicate walls. When this sample is manipulated so that the population of these titanium atoms tetrahedrally coordinated with the silicate network decreases, the intensity of the emission decreases proportionally, eventually being able to disappear and observing a comparative photoluminescence of several orders of magnitude weaker at longer emission wavelengths (around 600 nm). Therefore, it can be said that the presence of tetrapodal titanium is responsible for the emission at 490 nm. And if on the contrary, through a treatment you get restore the tetrapodal coordination of titanium atoms from the titanoles groups, the intensity of the photoluminescence at 490 nm is recovered. One way to achieve tetrapodal titanium regeneration is by silylation of the titanium groups. On the other hand, the analysis of the photoluminescence intensity decay demonstrates the existence of two important populations of ≡Ti-O- groups present in the structure. The present invention allows a high capacity characterization technique to be developed for simultaneous or consecutive analysis of large libraries of solid materials, based on solid photoluminescence measurements, so that by analyzing the photoluminescence information of each of the Samples and through due data processing, it is possible to determine the evolution in the formation and distribution of populations of photolumoforic groups, as well as the structural information concerning the chemical environment of the different populations of said groups. The present invention can be applied to a series of solids that contain in their structure chemical elements of the transition metal groups of the first and second period, heavy transition metals and rare earth metals (lanthanides and actinides), elements of the group of the terrestrial and carbon group. The present invention is of special interest for those elements in which it has been described that the emission of photoluminescence is of a high intensity, among which are tetrahedral titanium, vanadium and fundamentally the vanadyl, chromium, manganese, iron, cobalt group , copper, nickel, molybdenum (especially the group Mo = 0), ruthenium, palladium, cadmium, indium, tin, tungsten, rhenium, osmium, cerium, europium, gadolinium, terbium, dysprosium, holmium, erbium, uranium, neptunium and plutonium. Many of these groups present an emission when they are occupying network positions, whether they have a formal double bond with oxygen or if there are only simple bonds, while in many cases the union of the metal with hydroxyl groups or with coordination water inhibits the photoluminescence due to the relaxation mechanism consisting in the coupling of the electronic de-excitation with the increase of the vibration of the OH groups. On the other hand, it has been described that the emission wavelengths depend on the chemical composition of the rest of the network and, therefore, indirect information about the rest of the material can be obtained from the study of the emission spectrum. Thus, for example, the maximum emission of the vanadyl group can vary from 400 nm to 650 nm, depending on the nature of the support to which it is covalently anchored (H. García et. Al. App. Catal. A 2002), having established a linear relationship between the isoelectric point of the material and the wavelength of the maximum emission. The system described above may also be equipped with a computer system that allows the complete automation of the excitation, acquisition, management and storage system of the photoluminescence signals, support positioning, measurement data processing and operation conditions.

(temperature, flows, pressure), analysis of the fluorescence spectra and comparison with a database, adjustment to kinetic models of the temporal profiles of the photoluminescence signal and representation of results. EMBODIMENTS OF THE INVENTION Next, practical aspects of the invention will be described based on drawings, in which Figure 1 is a diagram showing excitation, fluorescence and phosphorescence spectra; Figure 2 shows a photoluminescence spectrum recorded in a sample of Ti / MCM-41. Figure 3 is a map of emission spectra of a Ti / MCM-41 sample; Figure 4 shows dexacitation kinetics of titanosylseaquioxane and a sample of Ti / MCM-41; Figure 5 schematically shows an apparatus according to the present invention that allows luminescence characterization of solid transparent samples sequentially. Figure 6 schematically shows an apparatus according to the present invention that allows luminescence characterization of transparent solid samples simultaneously. Figure 7 schematically shows details of the apparatus according to the embodiment shown in Figure 6. Figure 8 schematically shows another embodiment of the apparatus according to the present invention that allows luminescence characterization of solid opaque samples sequentially. Figure 10 shows the position of the series of titanosilicate samples subjected to high-capacity photoluminescence analysis. Figure 11 shows the percentage of tetrapodal titanium determined based on the intensity of a reference sample (located in position D4) Figure 12 shows population distribution based on half-life of tetrapodal titanium Figure 1 shows excitation (a), fluorescence (b) and phosphorescence (c) spectra. The absorption spectrum (a) has the vibrational structure corresponding to the upper excited state (Si). The fluorescence (b) shows a fine structure characteristic of the fundamental state (So). The emission is always displaced at lower frequencies and corresponds to the mirror image of the absorption spectrum. The cut-off point between the two spectra corresponds to the transition between the lowest vibrational levels of each state and is known as the 0-0 transition. Phosphorescence corresponds to the emission from the triplet state (of lower energy than Si) to the fundamental state The light emitted in photoluminescence, which corresponds to the transition between excited states and the fundamental state, contains different wavelengths, typically between 200 and 1500 nanometers, called the photoluminescence spectrum to determine the relative intensity of emission versus wavelength. Figure 2 shows a typical example of a recorded photoluminescence spectrum of a titanium / MCM-41 sample, specifically an emission spectrum (MS) when the λ _ex = 250 nm of the Ti / MCM-41 samples under vacuum and previously dehydrated for samples Ti / MCM-41 calcined (a), Ti / MCM-41 silylated (b). Spectrum (c) corresponds to the emission into the air of the silylated Ti / MCM-41 without prior vacuum or dehydration. The excitation spectrum recorded at λ _em = 390 nm (EX) corresponds to the silylated Ti / MCM-41 sample. To obtain the electronic excitation and therefore the appearance of the photoluminescence, the illumination of the sample is required with a radiation of suitable wavelength, usually in the ultraviolet range visible. The general way to determine the optimum excitation length is to observe the band maximums in the visible ultraviolet absorption spectrum. Related to the selection of the optimum excitation length there is a variant of the photoluminescence in which the detector is set at an emission wavelength while scanning all excitation wavelengths. The excitation wavelength always has to be shorter than the emission wavelength. The record that is obtained is known as the excitation spectrum and provides information on what is the emission intensity for each excitation wavelength. On the other hand, there are variants (fluorescence maps) in which emission spectra recorded for all excitation lengths are arranged in a parallel axis, the emission intensity corresponding to the Z axis, and in the perpendicular axis the excitation spectra. Figure 3 shows a typical example of a photoluminescence map, corresponding to a registered Ti / MCM-41 sample, after dehydration and sealed in a quartz cell, as a function of the excitation wavelength. These photoluminescence maps contain the maximum possible information regarding emission and excitation. With respect to the temporal profile of the emission there is a photoluminescence technique called single photon counting in which the excitation occurs by means of a light pulse coming from a flash lamp or a laser, being the Pulse duration much shorter than the lifetime of the excited state. Typical pulse durations are in the PS area ( ^10-12 seconds). This excitation of the sample causes the emission and what is recorded is how the intensity of light from the photoluminescence decreases to the time elapsed since the pulse. In the single photon counting technique, the photoluminescence time profile is constructed by detecting the time of arrival at the detector of the first emission photon and repeating the pulse (excitation / registration of the first emission photon that reaches the detector) a number of Statistically significant times, and that can generally be around 10,000 ^' accounts. Figure 4 shows the dexcitation kinetics of titanosylsquioxane 1 in CH ₂ C1 ₂ and in N ₂ (a) and a sample of Ti / MCM-41 (b) recorded at 490nm. The adjustment of the temporal profile of the photoluminescence to kinetic equations allows to establish the distribution of the different families that contribute to the emission (light groups). In the embodiments shown in Figures 5 to 8 there are numerical references whose meanings are as follows: 1- samples of solids 2- sample holder 3- cover of sample holder support and samples 4- medium on which fix the sample holder 5- empty chamber in contact with the solid samples 6- means to condition (filter, collimate, etc.) and focus the excitation radiation on a given sample 7- radiation generation means 8- control medium of the excitation source 9- means for focusing and conditioning the photoluminescence radiation from the excited sample

10- optical fiber to transmit conditioned photoluminescence radiation to the detection device

11- detection device 12- means for recording the photoluminescence radiation conditioned to the device for detecting and storing information 13- means for the movement of the sample holder holder 14- irradiation means, which allow irradiating the entire surface of the support on which they are distributed the samples 15- set comprising: sample holder, samples, protective cap and the means to prevent the radiation produced by a sample from reaching the detector or detection zone arranged to detect another different sample 16- integrated set of the media detection that includes: means for conditioning photoluminescence radiation and means for its spatially resolved detection. 17- means to prevent the radiation produced by a sample from reaching the detector or detection zone arranged to detect another sample other than 18- bifurca fiber, which allows irradiation and capture of fluorescence emission from the same point

Figure 5 represents an embodiment of the present invention, showing an apparatus for sequential photoluminescence characterization of transparent solid materials 1 arranged on a flat support 2. The sample holder 2 is positioned between a medium 4 on which it is fixed and a cover 3. The medium 4 is connected to drive means 13, such as a motorized Cartesian coordinate table (XY), by means of which the samples 1 can be moved sequentially so that the samples are arranged under conditioning means 6 of radiation conditioning radiation generated by the irradiation means 7 to apply a controlled radiation to the samples 1. The irradiation means 7 are arranged above the face of the sample holder 2 which is closed by the cover 3, and controlled by the control means 8. The The apparatus also comprises detection and recording means 9, 10, 11, 12 of the luminescence radiation produced by the samples 1 arranged in the support 2 as a result of its previous excitation by means of the irradiation means 7. It can be seen that, in the embodiment shown in FIG. 5, the detection and recording means are composed of means 9 for focusing and conditioning the photoluminescence radiation from the excited sample, optical fiber 10 that transmits the photoluminescence conditioned by means 9 to a detection device 11 of the conditioned photoluminescence and recording means 12 that detects and stores the data of the detected photoluminescence. If the radiation medium 7 is pulsed, information on the time profile of the emission (de-excitation) of the sample can be obtained. By design of the apparatus shown in Figure 5, it is possible to irradiate a material, detect and record the luminescence radiation of this first material disposed on the support in a first position, after which the support is moved until a second material it is located under the beam of the excitation radiation, and the process is repeated again until the characterization for all the samples arranged is completed. In the embodiment of the apparatus shown in Figures 6 and 7, suitable for simultaneous photoluminescence characterization of transparent solid materials arranged on a flat support, the apparatus comprises irradiation means 14 for applying radiation controlled to the entire surface of the support housing the samples, a sample holder assembly 15 comprising the sample holder in which the samples are arranged, the protective cover, screen means 17 to prevent the radiation produced by a sample from reaching the detector or detection zone arranged to detect another different sample, and a detector assembly comprising the conditioning means of the photoluminescence radiation emitted by each of the samples, as well as the detection means, is arranged below the samples and connected to the recording means 12. This embodiment allows the simultaneous detection and recording of the luminescence radiation produced by all samples arranged on the support 15 as a result of their previous excitation by means of the irradiation means 14. These means 14 include at least one system monochromator that allows rapid scanning, compared to the time that the luminescence process, of the different wavelengths that make up the emission, as well as a CCD device. The apparatus of this embodiment allows, therefore, to irradiate a set of materials 1 simultaneously as well as to detect and record the luminescence radiation of the set of materials arranged on the support, so that simultaneous acquisition of experimental data is possible of the emission intensities at different wavelengths, over the time the luminescence lasts for each of the samples. Figure 8 illustrates another embodiment of the present invention consisting of an apparatus for sequential photoluminescence characterization of samples 1 of solid opaque materials arranged on a flat support 2, whose apparatus has a front face geometry type _r geometry and comprises means of irradiation 6.7 to apply at least one controlled radiation to the samples 1, detection and recording means 9, 10, 11 of the luminescence radiation produced by the samples arranged 1 on the support 2 as a result of their previous excitation by means of the irradiation means 6, 7, and actuation means 13, such as a motorized Cartesian coordinate table (XY), for conferring a controlled sequential movement to the support 2. This apparatus allows irradiating a material 1, detecting and recording the luminescence radiation of this first material di arranged on the support 2 in a first position, after which the support 2 is moved until a second material 1 is located under the beam of the excitation radiation, and the process is repeated again until the characterization for all is completed the samples arranged. Figure 9 illustrates another embodiment of the present invention consisting of an apparatus for sequential photoluminescence characterization of samples 1 of solid opaque materials arranged on a flat support 2. Also, Figure 10 shows a representation of the sample holder used in this This embodiment consists of 32 wells where quantities between 10 and 50 milligrams of solid titanosilicate samples with different titanium content and with different density of titanoles groups are placed. The analysis of the tetrahedral titanium content of the samples would be carried out automatically by excitation through a bifurcated glass fiber (18) with a nitrogen laser operating at 237 nm and with a power of one millijul per pulse. The width of the laser pulse is in the range of 0.5 to 1 nanosecond. Using the fiber optic and using the system shown in Figure 9, each of the samples arranged in succession would be excited successively. the sample holder 2. For each sample the excitation produces the fluorescence emission of the titanium atom, where the wavelength of the maximum emission and its intensity are a function of the content of tetrapodal titanium atoms (μ _e = 390 nm) or tripodal titanoles that have a much weaker emission (μ _6m = 500nm). In the example of this embodiment, by means of the bifurcated fiber, the fluorescence from each sample is captured and directed towards a diffraction network of a bandwidth of 100 nm centered at 400 nm, coupled with a CCD camera that simultaneously captures all the wavelengths between 350 and 450 nm result from the diffraction network. In addition to spectral resolution, the CCD camera has a temporal resolution capability and by means of proper programming it is able to capture the spectra with a delay with respect to the laser pulse of 5, 10, 15, 25 nanoseconds after the laser pulse. Through this series of spectra it is possible to determine the temporal profile of the emission of the sample and of the kinetic analysis of the sample, to deduce the distribution of populations of tetrapodal titanium atoms. The time in which the emission is recorded for each sample is much less than one second, the analysis time per sample being limited by the mechanical movement of the sample holder. The means used for the movement is a Cartesian coordinate table, which allows movements with an accuracy of 5 μm and positioning speeds of one cm per second. The movement of the support is performed in the plane perpendicular to the laser beam. Typically, an analysis time of 10 seconds per sample is used for each sample, so the frequency is 6 samples per minute. Through proper programming it is possible to record the emission spectra for each of the samples Delay times different from the previous ones, so that the set of two or more series of measures gives rise by intercalation to a temporary decay profile of the emission that has four times N points, where N is the number of times in which fires a laser pulse on each sample. An example of the spectra that are obtained is shown in Figure 2. The analysis of the data obtained is performed on a computer other than the one that controls data acquisition, laser firing, experiment synchronization, sample movement, etc. This analysis allows to determine the relative amount of tetrapodal titanium by means of the emission intensity at 390 nm measured at 5 nanoseconds after the pulse for each of the samples. Figure 11 shows a representation of the results obtained for each sample of the tetrapodal titanium content with respect to a reference sample according to the position occupied by each sample in support. The homogeneity of the tetrapodal titanium in each sample and the number of different families of tetrapodal titanium is deduced from the kinetic analysis by an adjustment to a summation of first order equations. Thus, different populations are identified by the average life time (μ) they possess and the abundance of this population is obtained from the coefficient that accompanies the exponential term, see the following equation:

Figure 12 shows the population distribution based on the half-life of tetrapodal titanium. The catalytic activity of these materials for the epoxidation of definas is directly related to the types of titanium present in its structure. In fact, the best activity and catalytic selectivity in this reaction are obtained with high tetrapodal titanium contents (μ _em = 390 nm), with this type of titanium species being mainly constituted by a population whose half-life is less than 5 nanoseconds. In another example of the present invention, samples between 10 and 50 milligrams of vanadium are placed on the supported inorganic oxides. According to the previous example where the results for titanosilicate samples are described, another example of the present invention is the study of high capacity (high-throughput) for the supported vanadium samples. Taking into account the different absorption of these samples with respect to those of titanium, in the case of vanadium samples an Nd-YAG laser with frequency triplicator operating at 355 nm is used. By means of a bifurcated fiber, the laser pulse is directed to the sample, collecting the emission, which after being analyzed by a diffraction network is recorded by a CCD camera. The diffraction network is centered at 550 nm, the emission being recorded for a window between 500 and 600 nm. In these materials containing vanadium, the maximum emission depends on the isoelectric point of the support, this varying between 610 nm for very basic supports, such as magnesium oxide (Isoelectric point -12), and 520 nm for acidic supports such as oxide silicon (Isoelectric point ~ 1.8). As in the case of titanium, the temporary emission profile contains information on the distribution of populations among several families. This information can be achieved by adjusting the decay of the intensity for the maximum emission wavelength and adjusting it to a series of first order terms. The information obtained by this fluorescence characterization technique is related to vanadium with its catalytic activity in various oxidation reactions. When the maximum emission wavelength is close to the 500 nm region, the catalytic activity for oxygen insertion reactions in hydrocarbons is maximum. In contrast, when the maximum emission wavelength is close to 600 nm, vanadium samples have a high catalytic activity for oxidative dehydrogenation of hydrocarbons.

Claims

1. An apparatus for the characterization by photoluminescence techniques of multiple samples of solid materials, characterized in that it comprises at least irradiation means (6,7,8,14) to apply at least one controlled radiation to the samples (1), to the minus a support (2,3,4,15) that houses a plurality of samples (1) detection and recording means (9,10,11,16) of the photoluminescence radiation produced by the samples (1) arranged in the support (2,3,4,15) as a result of its previous irradiation.

2. An apparatus according to claim 1, characterized in that it further comprises control means for controlling at least one parameter of the apparatus selected from temperature, pressure and chemical composition of the atmosphere in contact with the samples (1).

3. An apparatus according to one of claims 1 and 2, characterized in that the irradiation means (6,7,8,14) generate radiation with wavelengths in the ultraviolet-visible range.

4. An apparatus according to one of claims 1 to 3, characterized in that it also includes drive means (13) for conferring a controlled movement to at least one support (4.16).

An apparatus according to one of claims 1 to 3, characterized in that it also includes actuation means (13) for conferring a controlled movement to the irradiation means (6,7,8,14) and detection means and registration (9,10,11,16).

An apparatus according to claim 2, characterized in that the control means comprise thermal regulation means capable of keeping the samples at a temperature in a range from -200 ° C to 600 ° C.

An apparatus according to one of claims 2 and 6, characterized in that the control means comprise means for regulating gaseous fluids to regulate the composition of gaseous fluids in contact with the sample holder surface of the support and / or the samples .

8. An apparatus according to any one of claims 1 to 7, characterized in that it comprises magnetizing means and / or generators of electric fields to be able to subject the samples to a magnetic and / or electric field.

An apparatus according to claim 1, characterized in that the irradiation means (6,7,8,14) comprise at least one laser emitting device.

10. An apparatus according to claim 9 characterized in that the laser emitting device comprises adjustment means for varying the frequency or range of laser emission frequencies.

11. An apparatus according to claim 1, characterized in that the irradiation means (6,7,8,14) are monochromatic light generating means.

12. An apparatus according to claim 1, characterized in that the irradiation means (6,7,8,14) are means polarized light generators.

13. An apparatus according to claim 1, characterized in that the detection and recording means (9,10,11,16) comprise at least one optical system for decomposing light in different wavelengths.

14. An apparatus according to claim 1, characterized in that the detection and recording means (9,10,11,16) comprise at least one filter for selecting a certain wavelength range of the photoluminescence radiation.

15. An apparatus according to claim 1, characterized in that the detection and recording means (9,10,11,16) comprise at least one CCD detection device.

16. An apparatus according to claim 1, characterized in that the detection and recording means (9,10,11,16) comprise at least one photomultiplier.

17. An apparatus according to claim 1, characterized in that the detection and recording means (9,10,11,16) comprise at least one integrated array of photomultipliers.

18. An apparatus according to claim 1, characterized in that the irradiation means (6,7,8,14) are capable of producing precise pulses of radiation with a determined duration in the range of feruto-, peak- and nanoseconds and with a repeatable frequency controllable from 0.1 to 2000 Hz.

19. An apparatus according to claim 1 or 2, characterized in that the irradiation means (6,7,8,14) allow several samples to be irradiated simultaneously.

20. An apparatus according to claim 1, characterized in that the detection and recording means (9,10,11,16) allow to simultaneously detect the emission of photoluminescence from several samples.

21. An apparatus according to claim 1, characterized in that the sample holder (2,4) comprises a plurality of locations for the direct deposit of at least one sample (1) in each location, a flat support (4) with a sample holder surface (2) comprising the locations for the samples, each location being defined in a predetermined position, and reversible coupling means of the support to drive means (13) to confer a controlled movement to the support (4).

22. An apparatus according to claim 21, characterized in that at least part of the locations are sectorally distributed on the sample holder surface (2).

23. An apparatus according to any one of claims 20 to 22, characterized in that at least part of the locations is defined by depressions in the sample holder surface (4).

24. An apparatus according to any one of claims 20 to 23, characterized in that at least part of the locations is defined between partitions (17) protruding from the sample holder surface (2).

25. An apparatus according to any one of claims 20 to 24, characterized in that at least part of the samples (1) is deposited in the locations on the sample holder surface (2) in the form of a thin film of solids.

26. An apparatus according to any one of claims 21 to 25, characterized in that the support (4) consists at least partially of a material transparent to certain electromagnetic waves.

27. An apparatus according to any one of claims 21 to 26, characterized in that the support (4) consists at least partially of a reflective material.

28. An apparatus according to any one of claims 21 to 27, characterized in that the support (4) is a flat circular support.

29. An apparatus according to any one of claims 21 to 28, characterized in that it is made of a heat-resistant material at temperatures between -200 to 600 ° C.

30. An apparatus according to claim 1, characterized in that the irradiation means (6,7,8,14) irradiate the samples (1) with a radiation in the range of 250-350 nm.

31. An apparatus according to claim 1, characterized in that the detection and recording means (9,10,11,16) detect radiations emitted by the irradiated samples, in the range of 200 to 1500 nm.

32. An apparatus according to claim 1, characterized in that the irradiation means (6,7,8,14) and the detection and recording means (9, 10, 11, 16) have at least one bifurcated optical fiber.

33. An apparatus according to any one of claims 1 to 7, characterized in that the solid materials arranged in the sample holder are in intimate contact with organic or inorganic molecules, which possess luminescent properties on their own or as a result of their interaction With the solid material.