Title of Invention	"A METHOD FOR THE SYNTHESIS OF MERCURY CADMIUM TELLURIDE NANOPARTICLES"
Abstract	1. A method for synthesis of nanoparticles of Mercury Cadmium Telluride (MCT), the said method comprising the steps of a) taking a salt of mercury in a SS autoclave. b) adding a cadmium salt or cadmium powder to the said autoclave. c) adding a tellurium powder. d) adding a coordinating solvent to the above mixture. e) adding about 5-10mg or 3-5ml of a strong reducing agent to the resulting mixture. f) closing the said autoclave and keeping it in an oven at temperature of 80°C-200°C for a period of 10-50 hours. g) allowing the said autoclave to cool down naturally inside the oven to room temp. h) filtering the resulting contents of the autoclave. i) washing the residue with double distilled water and then preferrably with absolute ethanol. j) drying the resulting residue in vacuum for 1-3 hours at a temperature of 40-75°C.

Title of Invention

"A METHOD FOR THE SYNTHESIS OF MERCURY CADMIUM TELLURIDE NANOPARTICLES"

Abstract

1. A method for synthesis of nanoparticles of Mercury Cadmium Telluride (MCT), the said method comprising the steps of a) taking a salt of mercury in a SS autoclave. b) adding a cadmium salt or cadmium powder to the said autoclave. c) adding a tellurium powder. d) adding a coordinating solvent to the above mixture. e) adding about 5-10mg or 3-5ml of a strong reducing agent to the resulting mixture. f) closing the said autoclave and keeping it in an oven at temperature of 80°C-200°C for a period of 10-50 hours. g) allowing the said autoclave to cool down naturally inside the oven to room temp. h) filtering the resulting contents of the autoclave. i) washing the residue with double distilled water and then preferrably with absolute ethanol. j) drying the resulting residue in vacuum for 1-3 hours at a temperature of 40-75°C.

Full Text	FIELD OF INVENTION: The invention relates method for synthesis of nanoparticles of Mercury Cadmium Telluride Nanoparticles PRIOR ART: Mercury Cadmium Telluride is a compound semiconductor, which finds Applications in Defence, Space, Medical, and Scientific fields, for example, Thermal Imaging, Night Vision, Missile Guidance, Heat-Seeking Guidance, Temperature Monitoring, Laser Monitoring, Laser Warning Receiver, Industrial Process Control, CO2 Laser Detection, FTIR Spectroscopy Mercury Cadmium Telluride Nanocrystallites can be useful in IR photovoltaics, Hybrid Photovoltaic materials, as Light Emitting Diodes, as Photonic Crystal, in Single electron transistor, in Biosensors. Particularly Nanocrystalline HgTe finds applications in telecommunication low loss optical fiber windows, Infrared optical amplifiers and Biosensors. Nanocrystallites having small diameters can have properties intermediate between molecular and bulk forms of matter. Nanocrystallites based on semiconductor materials having small diameters can exhibit confinement of both the electron and hole in all three dimensions, which leads to an increase in the effective bandgap of the material with the decrease in the crystallite size. Consequently, both the optical absorption and emission of light in nanocrystallites shift to higher energy side as the crystallite size decreases. Various synthetic approaches have been developed in preparing nano-sized II-VI and IV-VI semiconductors. Much of this effort has been aimed at achieving a very narrow particle size distribution. The basic idea is to use the spatial or chemical confinement provided by matrices or organic capping molecules to terminate the growth of Nanocrystallites at any desired stage. Since various groups of compound semiconductor nanocrystallites are of interest for use in optical displays, single electron transistors, Biosensors as well as biological applications, it would be desirable to provide a process for mass producing these semiconductor nanocrystallites wherein the particle size, growth rate, and particle size distribution can be reproducibly controlled. In addition to these techniques the conventional wet chemistry synthesis performed without matrix assistance tends to result in the production of micron size particles. Various host matrices, such as glass, zeolites, sol-gels, and micelles, have been used to synthesize nanoparticles. However, a number of problems have been found to be associated with these methods. For instance, the particles synthesized in glasses and sol-gels exhibit large polydispersity, since they are not ordered structures. Another disadvantage with these methods is the inability to easily isolate the nanoparticles from the matrix material. In the case of micelles, even though it is possible to isolate the particles, the low precursor concentrations required will make mass production of nanoparticles expensive or impractical. Semiconductor nanocrystallites may be formed by dissolving corresponding precursors in a solvent and then applying heat to the resulting solution. For example Group II-VI semiconductor nanocrystallites may be formed by dissolving a dialkyl of the group II metal and a Group VI powder in a trialkyl phosphine solvent at ambient temperature, and then injecting the mixture into a heated (340 to 360°C) bath of tri-octyl phosphine oxide (TOPO). While the above process is capable of producing Group II-VI semiconductor nanocrystalls, the results can be somewhat erratic in terms of average particle size and size distribution. This problem of not being reproducible is likely due to the impurities in the technical grated (90% pure) TOPO that adversely influence the reaction. Alivisatos et al. describes a process for forming Group II-VI semiconductor nanocrystalls wherein size control is achieved through use of a crystallite growth terminator, which controls the size of the growing crystals. Crystallite growth terminators are said to include a nitrogen containing or a phosphorus-containing polar organic solvent having an unshared pair of electrons. They further stated that this growth terminator can complex with the metal and bind to it, thereby presenting a surface, which will prevent further crystal growth The techniques for the generation of Semiconductor nanocrystallites can be divided into three broad categories: Vacuum, gas-phase, and condensed-phase synthesis. Vacuum synthesis techniques include sputtering, laser ablation, and liquid-metal ion sources. Gas-phase synthesis includes inert gas condensation, oven sources (for direct evaporation into a gas to produce an aerosol or smoke of clusters), laser induced vaporization, laser pyrolysis, flame hydrolysis, and combustion synthesis. Condensed-phase synthesis includes reduction of metal ions in acidic aqueous solution, liquid phase precipitation of semiconductor clusters, and decomposition-precipitation of ionic materials for ceramic clusters. Other methods include high-energy milling, mix-alloy processing, chemical vapor deposition (CVD), and sol-gel techniques. All of these techniques have one or more of the following problems or shortcomings: (1) Most of these techniques suffer from extremely low production rates. It is not usual to find production rate of several grams a day. Vacuum sputtering, for instance, only produces small amounts of particles at a time. Laser ablation and laser-assisted chemical vapor deposition techniques are well known to be excessively slow processes. The high-energy ball milling method, known to be a "quantity" process, is capable of producing only several kilograms of nano-scaled powders in approximately 100 hours. These low production rates, resulting in high product costs, have severely limited the utility value of nano-phase materials. There is therefore, a clear need for a faster, more cost-effective method for preparing nanometer-sized powdered materials. (2) Condensed-phase synthesis such as direct reaction of metallic element with a reactant to produce compound semiconductor nanocrystallites requires pre-production of metallic element of high purity in finely powdered form. This reaction tends to produce a compound powder product, which is constituted of broad particle size distribution. Further more, this particular reaction does not yield a product powder finer than lOOnm except with great difficulty. Due to the limited availability of pure metallic element in finely powdered from, the use of an impure metallic powder necessarily leads to an impure compound semiconductor product. In our case it is not possible to prepare mercury in the powder from, which prevents the use of this method. (3) Most of the processes require heavy and/or expensive equipment (e.g., a high power laser source and high vacuum equipment), resulting in high production costs. In the precipitation of ultra fine particles from the vapor phase, when using thermal plasmas or laser beams as energy sources, the particle sizes and size distribution cannot be precisely controlled. Also, the reaction conditions usually lead to a broad particle size distribution as well as the appearance of individual particles having diameters that are multiples of the average particle size. (4) The conventional mechanical attrition and grinding processes have the disadvantages that powders only be produced up to certain fineness and with relatively broad particle-size distribution. As a matter of fact, with the currently familiar large-scale process for manufacturing powders it is rarely possible, or only possible with considerable difficulty, to produce powders having average particle sizes of less than 500 nm. Particularly Mercury Cadmium Telluride and Mercury related compounds have been prepared by wet chemical methods (Journal Ref. 12, 13, 16). Which have the limitations of handling toxic chemicals and the production cost due to the unavailability of technique required to prepare the large amount of the material. OBJECTIVES OF THE INVENTION Method of making nanoparticles involves solvothermal method In one aspect, the invention features a method of manufacturing Mercury Cadmium Telluride nanoparticles (Hg1-xCdxTe). The method includes an M-containing salt is a non-organometalic compound e.g. free from metal-carbon bonds. M containing salt can be a metal halide, metal carboxylate, metal carbonate and metal hydroxide. The metal containing salt is less expensive and safer to use than organometallic compounds, such as metal alkyls. For example the M-containing salts are stable in air, whereas metal alkyls generally unstable in air. M-containing salts such as halide, carboxylate, hydroxide or carbonate salts are stable in air and allow the preparation of the nanoparticles to be manufactured under less rigorous conditions than corresponding metal alkyls. For example M-containing salts, where M is Cadmium, the salts include Cadmium acetylacetonate, cadmium iodide, cadmium bromide, cadmium hydroxide, cadmium carbonate, cadmium acetate, cadmium chloride, cadmium oxide, Cadmium powder. In another aspect, the invention features a method of manufacturing nanoparticles includes M-containing salts, where M is Mercury, the salts include Mercury acetylacetonate, mercury iodide, mercury bromide, mercury hydroxide, mercury carbonate, mercury acetate, mercury oxide, mercury chloride etc. In another aspect the invention features the preparation of nanoparticles for all compositions of x=0 to x=l in Hg1-xCdxTe. In yet another aspect, the invention features a coordinating solvent is a compound having donor lone pair that, for example, has a lone electron pair available to coordinate to a surface of the growing nanoparticle. Solvent coordination can stabilize the growing nanoparticles. Typical coordinating solvents include solvents such as pyridine, amine, ethyleneglycol, diethylamine, ethylenidiamine and the mixture thereof. In yet another aspect, the invention features a reducing agent any compound which is capable of reducing the M of the M-containing salt. The M-containing salt reducing agents to produce the metal precursor for the formation of nanoparticles includes the reducing agents for example Hydrazine, Lithium Aluminium Hydride, Sodium Borohydride, ferrous chloride and other reducing agents. In yet another aspect, the invention features includes the preparation of core/shell structure of nanoparticles, for example CdTe/HgTe/CdTe. In yet another aspect, the invention features include the preparation of doped nanoparticles (both p-type and n-type) the dopants includes CI, Br, I, B, As, Sb. In yet another aspect the method features, the preparation of other semiconductor nanoparticles with different compositions (x=0 to x=l) this includes the preparation of nanoparticles of Hgi_xMxN (for x=0 to x= 1) for example, M can be Cd, Zn, AI, Mn, Pb, Mg, Ga, In, Sb, As, Tl and N can be S, Se, Te and the mixtures thereof. In yet another aspect the invention features monitoring the size and the size distribution of a population including of the nanoparticles changes the reaction temperature in response to a spreading of the size distribution. In yet another aspect the invention features monitoring the size and size distribution of a population including the nanoparticles synthesized with different compositions. DESCRIPTION OF THE FIGURES Fig. (1) X-ray diffraction pattern of Sample A Fig. (2) ED AX spectra of Sample A Fig. (3) X-ray diffraction pattern of Sample B Fig. (4) EDAX spectra of Sample B Fig. (5) X-ray diffraction pattern of Sample C Fig. (6) X-ray diffraction pattern of Sample D Fig. (7) Transmission Electron Micrograph of Sample B Fig.(8) Histogram for TEM Micrograph of Sample B Fig.(9) TEM Selected area diffraction pattern recorded for Sample B Fig. (10) Transmission Electron Micrograph of Sample C Fig (11) Histogram for TEM micrograph of Sample C Fig. (12) TEM Selected area diffraction pattern recorded for Sample C Fig. (13) Transmission Electron Micrograph of Sample D Fig. (14) Histogram for TEM Micrograph of Sample D Fig. (15) TEM selected area diffraction pattern recorded for Sample D DESCRIPTION OF THE INVENTION: The present invention relates to - A method for synthesis of nanoparticles of Mercury Cadmium Telluride (MCT) The said method comprising the steps of a) taking a salt of mercury in a SS autoclave. b) adding a cadmium salt or cadmium powder to the said autoclave. c) adding a tellurium powder. d) adding a coordinating solvent to the above mixture. e) adding about 5-10mg or 3-5ml of a strong reducing agent to the resulting mixture. f) closing the said autoclave and keeping it in an oven at temperature of 80°C-200°C for a period of 10-50 hours. g) allowing the said autoclave to cool down naturally inside the oven to room temp. h) filtering the resulting contents of the autoclave. i) washing the residue with double distilled water and then preferrably with absolute ethanol. j) drying the resulting residue in vacuum for 1-3 hours at a temperature of 40-75°C. - The said method wherein the said mercury salt is Mercury Chlorate, more preferably Mercury Oxide most preferably Mercury Chloride. - The said method wherein as claimed above wherein the said Cd source is Cadmium Iodide or Cadmium Bromide or Cadmium Hydroxide more preferably Cadmium Oxide or Cadmium Carbonate most preferably Cadmium Acetate or Cadmium Chloride or Cadmium powder. - The said method wherein as claimed above wherein the said Te source is Te powder - The said method wherein as claimed above wherein the said autoclave has a Teflon coating on the inside. - The said method wherein as claimed above wherein the autoclave has a platinum liner on the inside. - The said method wherein as claimed above wherein the said coordinating solvent is a compound having one or more oxygen or Nitrogen coordinating atoms. - The said method wherein as claimed above wherein the said coordinating solvent is preferrably an N-chelating agent containing N with lone pair of electrons, or coordinating solvent containing Oxygen with lone pair of electrons. - The said method wherein as claimed above wherein the said coordinating solvent is a mixture of the solvents as claimed above. - The said method wherein the said solvent is preferrably pyridine, ethyleneglycol more preferably dietylamine or ethylenediamine most preferably amine. - The said method wherein the said reducing agent is preferrably Lithium Aluminum Hydride, Sodium Borohydride, Hydrazine most preferrably Iron Chloride. - The said method wherein the autoclave is heated preferrably between 140-180°C, more preferrably between 170-180°C. - The said method wherein period of heating the autoclave is preferrably between 16-24 hours. - The said method wherein the method claimed above can be applicable for all the composition from x= 0 to x=l in Hgi_xCdxTe. - The said method wherein MCT nanoparticles obtained from the method such that said particles can be produced in grams by each iteration of the said method. - The said method wherein MCT nanoparticles obtained from the method as claimed above such that the said nanoparticles have core/shell structure. - The said method wherein MCT nanoparticles obtained from the method claimed above such that the shapes of the said nanoparticles are spherical or rod type or disc type or irregular shape. - The said method wherein MCT nanoparticles obtained from the method as claimed above such that the said nanoparticles do not need a coating for preventing agglomeration. - The said method wherein MCT nanoparticles obtained from the method as claimed such that the said nanoparticles can be doped (both p and n-type) by the said method - The said method wherein, the dopants can be CI, Br, I, B, As, Sb. Advantages of the proposed method ; Relatively Solvothermal method is a simple and cost effective technique for the synthesis of binary and ternary semiconductor Nanocrystallites. In the Solvothermal synthesis the reaction takes place inside a pressure vessel namely Teflon-Stainless-Steel autoclave, in which the reactants along with the solvents will be heated well above the boiling points of the solvents, so that the autogenous pressure far exceeds the ambient pressure. This automatically raises the effective boiling point of the solvent. Such a method is extensively used in the preparation of inorganic solids, and in particular of zeolite materials. In case water is used as solvent it is called a hydrothermal synthesis, if any organic solvent is used then it is called as Solvothermal synthesis. Solvothermal synthesis is relatively low temperature and time effective technique. In the Solvothermal synthesis we can control growth rate, particle size and particle size distribution and most importantly Solvothermal method can be used for large scale production with greater control over the particle size, which is one of the advantages of this method compared to the other semiconductor nanocrystals producing methods. The main advantages of the Solvothermal method are (a) Kinetics of reaction is greatly increased with a small increase in temperature, (b) New metastable products can be formed, (c) single crystals can be obtained, (d) High purity products can be obtained from impure feedstocks, (e) No precipitants are needed in many cases and thus process is cost effective, (f) pollution is minimized because of the closed system conditions. We can use reducing agents in very minute quantity, which will reduce the metal containing salts into their corresponding ions, which further take part in the reaction for the formation of final product. It is not required to use heavy and/or expensive equipment like a high power laser source and high vacuum equipment, therefore, reduces the production cost dramatically. In case of the synthesis of alloy compound semiconductors it is difficult to get the controlled composition, but by using Solvothermal method we can synthesize the controlled alloy compositions. It is also possible to synthesize nanocrystals with core/shell structure. Solvents like water, Ethylenediamine, Pyridine, Diethylamine, Ethyleneglycol and other coordinating organic solvents can be used. Ethylenediamine has been widely used in the synthesis of semiconductor and other nanocrystals preparation by the Solvothermal method. Solvothermal method can be used for the synthesis of doped semiconductor nanocrystals by just adding the dopant element in the Solvothermal process, which could be a simple way of preparing the doped semiconductor nanocrystals. The materials, which are difficult to dope, can be doped by using Solvothermal process. The said nanoparticles can also be prepared by the following methods (I) Microwave Hydrothermal or Microwave Solvothermal. (II) Electrochemical Hydrothermal method or Electrochemical Solvothermal method. (III) The said nanoparticles can also be prepared by Sonochemical Hydrothermal or Sonochemical Solvothermal method. (IV) The said nanoparticles can also be prepared by Ultrasonic-Hydrothermal or Ultrasonic-Solvothermal method. Experimental details with examples: M-containing salts have been used as the source materials for both the Metals for Example Cd and Hg. Reducing agent is also used. Ethylenediamine had been used as a solvent. The autoclave was filled with 80% of the solvent and kept in oven at 180°C for 24 hours, then cooled to room temperature. The reaction product was washed with absolute ethanol, double distilled water to remove the organic and inorganic impurities. The product was dried in Vacuum for 2 hours. The product was characterized by X-ray diffraction, Energy dispersive x-ray analysis and Transmission electron microscopy. X-ray diffraction studies confirmed the formation of MCT nanoparticles. The average particle size calculated from Debye-Scherrer formula and found to be varied from 7-12 nm, which depends on the original composition of the Hg1-xCdxTe. Different composition of MCT has been prepared by changing the amounts of precursors in the Solvothermal process. X-ray diffraction studies also revealed the formation of CdTe nanoparticles instead of MCT when the reaction takes place in absence of reducing agents. X-ray diffraction patterns clearly showed the presence of CdTe peaks and Metal-Salts taken as precursors in the Solvothermal process. This clearly tells us that the presence of reducing agents is necessary for the formation of MCT nanoparticles. The role of reducing agent in the process is to reduce the metal salts to its metal ions. In absence of reducing agents it is not possible to generate the metal ions in the process, so the desired product is not been achievable. The nanoparticles synthesized in presence of reducing agents shows the formation of MCT nanoparticles and no metal salts. Energy dispersive x-ray analysis studies revealed the composition of the nanoparticles. Energy dispersive x-ray analysis also revealed the information that the nanoparticles prepared in absence of reducing agent contains the salts of the Metals taken as precursors in the Solvothermal process. Whereas the nanoparticles synthesized in presence of reducing agent showed the formation of MCT nanoparticles. The MCT nanoparticles thus prepared can be used for the thin film preparation by different methods like Spray deposition and Spin coating. The reduction in the melting point of the nanoparticles compared to the bulk material will allow us to prepare the thin film at lower temperatures at about 160-200°C by spray deposition technique. We can deposit the films on different substrates like glass, quartz and silicon wafers. In our lab we were able to synthesize the nanorods of binary II-VI semiconductor nanoparticles by modifying the spray process (Ref. 19), for example nanorods of CdSe, CdTe and HgTe. We can apply the same process for the synthesis of nanorods of MCT also. In our lab we also able to produce Nanofibers of doped II-VI semiconductor materials like CdSe, CdTe and HgTe. We may get the nanofibers of doped MCT thin films once we are able to prepare doped nanoparticles by Solvothermal method. Transmission electron microscopy (TEM) can provide information about the size, shape, and distribution of the nanoparticles size. Powder X-ray diffraction (XRD) patterns can provided the most complete information regarding the type and quality of the crystal structure of the nanocrystallites. Estimation of size is also possible, for example the particle size can be calculated directly by transmission electron microscopy images or estimated from X-ray diffraction data using, for example the Debye-Scherrer equation. Details of the instruments used for characterization (a) Transmission electron microscopy Nanoparticle size, morphology and structure were measured by TEM on Philips CM 12 electron microscopy with accelerating voltage available from 20 kV to 120kV and point to point resolving power of 0.4 nm. In the present study the microscopy was operated at an accelerating voltage of 100 kV to minimize beam damage to the sample. Nanoparticles were deposited from dilute solution onto a amorphous carbon supported 200 mesh copper grids. One drop of nanoparticle solution in either toluene or chloroform was deposited on to the grid and allowed to evaporate. The sample was then washed with methanol to remove the excess organic compounds and placed in dessicator over night. Average sizes and morphologies were measured at 1, 40,000 times magnification. Average particle size and size distributions were determined by counting at least 500 nanoparticles for sample for statistical purposes. (b) Powder X-ray diffraction Powder X-ray diffraction was performed on a RIGAKU Giegerflex-D/max- RB-RU 200 X-ray diffractometer using Cu K alpha radiation (wavelength 1.5418 A0) from a rotating anode; capable of generating a maximum power of 12 KW is used as a source of radiation. In the present studies the diffractometer was operated at 4 KW. The crystallite size was calculated by using Debye-Scherrer equation. (c) Energy dispersive X-ray analysis (EDAX) For the Composition analysis of the MCT nanoparticles mined by Energy Dispersive X-ray Analysis (EDAX) ISIS 200 was used at the operation voltage of 20KV and current 10"9 ampere. Results Four different types MCT nanoparticles have been prepared. Sample A has Hg and Cd in the ration 40:60 and no reducing agent is used in the process. Sample B has Hg and Cd in the same ratio as in Sample A, but the reducing agent is added. Sample C and D have Hg and Cd in the ratios 50:50 and 70:30, respectively and in both the samples reducing agent is used. Fig.l shows the X-ray diffraction pattern of sample A, where we use Mercury compound along with Cd and Te. Diffraction peaks corresponding to CdTe and Mercury Chloride are observed. The ED AX analysis (Fig.2) for Sample A also shows the presence of Mercury in the unreacted form and a large amount of Chlorine can also be seen. This means that the mercury salt is not reduced, if it is so, there would not be any presence of Chlorine. Thus it can be concluded that a suitable reducing agent needed for the creation of MCT nanoparticles during Solvothermal method. The role of this reducing agent is to reduce the metal compounds to yield metal ions, which then combine with Te. Therefore, if we use Mercury salt along with Cd and Te only (Sample A), the process yields CdTe nanoparticles. The role of reducing agent can be clearly seen from Fig.3, which shows the X-ray diffraction pattern of the sample B. Fig.5 and Fig.6 shows the X-ray diffraction pattern of the samples C and sample D. All the peaks corresponding to cubic MCT are observed, with (111) peak dominant. The average crystallite size calculated from X-ray diffraction pattern using Debye-Scherrer formula is found to be 7-12 nm. A small peak corresponding to Te02 can also be seen in Sample C (Fig.5). This may be due to the presence of some unreacted Te, which converts to Te02. Fig (4) shows the ED AX spectra of the sample B, which clearly show little or no chlorine presence. This means that when we use reducing agent the mercury in the mercury chloride will get reduce and generates mercury ions, which then takes place in the formation of MCT nanoparticles. Both X-ray diffraction and EDAX data confirms the role of the reducing agent in MCT nanoparticles preparation. With increasing Hg amount, the EDAX spectra show the corresponding increase in Hg peak. Fig.7, 10 and 13 shows the TEM micrographs of the MCT nanoparticles of Sample B, Sample C and Sample D respectively. The shape of the particles is not exactly spherical, but random. This is as expected, because in the Solvothermal method the shape and size of the nanoparticles depends on the solvent used, reaction temperature and time. Solvent and reaction temperature play a crucial role in controlling the nucleation and growth of crystallites. Ethylenediamine has the ability to create the random shaped particle due to its high coordinating nature towards the metal Cation. Different shapes of II-VI nanoparticles (e.g., Nanorods) with different solvents have been reported. The average particle size varied from ~10-15 nm. The histograms plotted (Fig. 8, 11, and 14) for particle size and size distribution of each of the samples B, C and D (from TEM micrographs of the samples) also show the average particle size from 10-15 nm for the sample B, C and D. Fig. 9, 12 and 15 shows the Selected Area Diffraction patterns recorded on the TEM images of Sample B, C and D respectively. The lattice parameter (a) calculated from the diffraction patterns is found to be ~0.6464 nm, which is close to the standard MCT value. In our experiments we observed the nanoparticles with narrow size distribution can be obtained by dispersing the nanoparticles in 1-Butanol. The particle size distribution can be refined by size selective precipitation with a proper solvent for the nanoparticles, such as methanol/butanol as described in U.S. patent no. 6,320901. For example nanopartilces can be dispersed in solution of 10% butanol in hexane. Methanol can be added drop-wise to this stirring solution until opalescence persists. Separation of supernatant and flocculate by centrifugation produces a precipitate enriched with the largest particles in the sample. Size selective precipitate can be carried out in a variety of solvent pairs, including pyridine/hexane and chloroform/methanol. We claim 1. A method for synthesis of nanoparticles of Mercury Cadmium Telluride (MCT), the said method comprising the steps of a) taking a salt of mercury in a SS autoclave. b) adding a cadmium salt or cadmium powder to the said autoclave. c) adding a tellurium powder. d) adding a coordinating solvent to the above mixture. e) adding about 5-10mg or 3-5ml of a strong reducing agent to the resulting mixture. f) closing the said autoclave and keeping it in an oven at temperature of 80°C-200°C for a period of 10-50 hours. g) allowing the said autoclave to cool down naturally inside the oven to room temp. h) filtering the resulting contents of the autoclave. i) washing the residue with double distilled water and then preferrably with absolute ethanol. j) drying the resulting residue in vacuum for 1-3 hours at a temperature of 40-75°C. 2. A method as claimed in claim 1(a) wherein the said mercury salt is Mercury Chlorate, preferably Mercury Oxide more preferably Mercury Chloride. 3. A method as claimed in claim 1(b) wherein the said Cd source is Cadmium Iodide or Cadmium Bromide or Cadmium Hydroxide more preferably Cadmium Oxide or Cadmium Carbonate most preferably Cadmium Acetate or Cadmium Chloride or Cadmium powder. 4. A method as claimed in claim 1(d) wherein the said coordinating solvent is a compound having one or more oxygen or Nitrogen coordinating atoms. 5. A method as claimed in claim 1 wherein the said coordinating solvent is a mixture of the solvents claimed in claim 4. 6. A method as claimed in claim 4 wherein the said solvent is preferrably pyridine, ethyleneglycol more preferably dietylamine or ethylenediamine most preferably amine. 7. A method as claimed in claim 1(e) wherein the said reducing agent is preferrably Lithium Aluminum Hydride, Sodium Borohydride, Hydrazine most preferrably Iron Chloride. 8. A method as claimed in claim 1(f) wherein the autoclave is heated preferrably between 140-180°C, more preferrably between 170-180°C. 9. A method as claimed in claim 1(f) wherein the said period of heating the autoclave is preferrably between 16-24 hours. 10.A method as claimed in claim 1 wherein the said MCT nanoparticles of any composition from x= 0 to x=l in Hg1-xCdxTe can be made by this method. 11. MCT nanoparticles obtained from the method of claim 1 such that said particles are produced in grams by each iteration of the said method. 12. MCT nanoparticles obtained from the method claimed in claim 1 such that the said nanoparticles have core/shell structure. 13. MCT nanoparticles obtained from the method claimed in claim 1 such that the shapes of the said nanoparticles are spherical or rod type or disc type or irregular. 14. MCT nanoparticles obtained from the method claimed in claim 1 such that the said nanoparticles do not need a coating for preventing agglomeration. 15. MCT nanoparticles obtained from the method claimed in claim 1 such that the said nanoparticles can be doped (both p and n-type) by the said method 16. A method for synthesis of nanoparticles of mercury cadmium telluride substantially as herein described with reference to the accompanying examples and figures. 17. MCT nanoparticles substantially as herein described with reference to the accompanying examples and figures.

Full Text

FIELD OF INVENTION:
The invention relates method for synthesis of nanoparticles of Mercury Cadmium Telluride Nanoparticles
PRIOR ART:
Mercury Cadmium Telluride is a compound semiconductor, which finds Applications in Defence, Space, Medical, and Scientific fields, for example, Thermal Imaging, Night Vision, Missile Guidance, Heat-Seeking Guidance, Temperature Monitoring, Laser Monitoring, Laser Warning Receiver, Industrial Process Control, CO2 Laser Detection, FTIR Spectroscopy
Mercury Cadmium Telluride Nanocrystallites can be useful in IR photovoltaics, Hybrid Photovoltaic materials, as Light Emitting Diodes, as Photonic Crystal, in Single electron transistor, in Biosensors. Particularly Nanocrystalline HgTe finds applications in telecommunication low loss optical fiber windows, Infrared optical amplifiers and Biosensors.
Nanocrystallites having small diameters can have properties intermediate between molecular and bulk forms of matter. Nanocrystallites based on semiconductor materials having small

diameters can exhibit confinement of both the electron and hole in all three dimensions, which leads to an increase in the effective bandgap of the material with the decrease in the crystallite size. Consequently, both the optical absorption and emission of light in nanocrystallites shift to higher energy side as the crystallite size decreases.
Various synthetic approaches have been developed in preparing nano-sized II-VI and IV-VI semiconductors. Much of this effort has been aimed at achieving a very narrow particle size distribution. The basic idea is to use the spatial or chemical confinement provided by matrices or organic capping molecules to terminate the growth of Nanocrystallites at any desired stage.
Since various groups of compound semiconductor nanocrystallites are of interest for use in optical displays, single electron transistors, Biosensors as well as biological applications, it would be desirable to provide a process for mass producing these semiconductor nanocrystallites wherein the particle size, growth rate, and particle size distribution can be reproducibly controlled.

In addition to these techniques the conventional wet chemistry synthesis performed without matrix assistance tends to result in the production of micron size particles. Various host matrices, such as glass, zeolites, sol-gels, and micelles, have been used to synthesize nanoparticles. However, a number of problems have been found to be associated with these methods. For instance, the particles synthesized in glasses and sol-gels exhibit large polydispersity, since they are not ordered structures. Another disadvantage with these methods is the inability to easily isolate the nanoparticles from the matrix material. In the case of micelles, even though it is possible to isolate the particles, the low precursor concentrations required will make mass production of nanoparticles expensive or impractical.
Semiconductor nanocrystallites may be formed by dissolving corresponding precursors in a solvent and then applying heat to the resulting solution. For example Group II-VI semiconductor nanocrystallites may be formed by dissolving a dialkyl of the group II metal and a Group VI powder in a trialkyl phosphine solvent at ambient temperature, and then injecting the mixture into a heated (340 to 360°C) bath of tri-octyl phosphine oxide (TOPO). While the above

process is capable of producing Group II-VI semiconductor nanocrystalls, the results can be somewhat erratic in terms of average particle size and size distribution. This problem of not being reproducible is likely due to the impurities in the technical grated (90% pure) TOPO that adversely influence the reaction.
Alivisatos et al. describes a process for forming Group II-VI semiconductor nanocrystalls wherein size control is achieved through use of a crystallite growth terminator, which controls the size of the growing crystals. Crystallite growth terminators are said to include a nitrogen containing or a phosphorus-containing polar organic solvent having an unshared pair of electrons. They further stated that this growth terminator can complex with the metal and bind to it, thereby presenting a surface, which will prevent further crystal growth
The techniques for the generation of Semiconductor nanocrystallites can be divided into three broad categories: Vacuum, gas-phase, and condensed-phase synthesis. Vacuum synthesis techniques include sputtering, laser ablation, and liquid-metal ion sources. Gas-phase synthesis includes inert gas condensation, oven sources (for direct evaporation into a gas to produce an aerosol or smoke of clusters), laser

induced vaporization, laser pyrolysis, flame hydrolysis, and combustion synthesis. Condensed-phase synthesis includes reduction of metal ions in acidic aqueous solution, liquid phase precipitation of semiconductor clusters, and decomposition-precipitation of ionic materials for ceramic clusters. Other methods include high-energy milling, mix-alloy processing, chemical vapor deposition (CVD), and sol-gel techniques.
All of these techniques have one or more of the following problems or shortcomings:
(1) Most of these techniques suffer from extremely low production rates. It is not usual to find production rate of several grams a day. Vacuum sputtering, for instance, only produces small amounts of particles at a time. Laser ablation and laser-assisted chemical vapor deposition techniques are well known to be excessively slow processes. The high-energy ball milling method, known to be a "quantity" process, is capable of producing only several kilograms of nano-scaled powders in approximately 100 hours. These low production rates, resulting in high product costs, have severely limited the utility value of nano-phase materials. There is therefore, a clear need for a faster, more cost-effective method for preparing nanometer-sized powdered materials.

(2) Condensed-phase synthesis such as direct reaction of metallic
element with a reactant to produce compound semiconductor
nanocrystallites requires pre-production of metallic element of high
purity in finely powdered form. This reaction tends to produce a
compound powder product, which is constituted of broad particle size
distribution. Further more, this particular reaction does not yield a
product powder finer than lOOnm except with great difficulty. Due to
the limited availability of pure metallic element in finely powdered
from, the use of an impure metallic powder necessarily leads to an
impure compound semiconductor product. In our case it is not possible
to prepare mercury in the powder from, which prevents the use of this
method.
(3) Most of the processes require heavy and/or expensive equipment
(e.g., a high power laser source and high vacuum equipment), resulting
in high production costs. In the precipitation of ultra fine particles from
the vapor phase, when using thermal plasmas or laser beams as energy
sources, the particle sizes and size distribution cannot be precisely
controlled. Also, the reaction conditions usually lead to a broad particle

size distribution as well as the appearance of individual particles having diameters that are multiples of the average particle size. (4) The conventional mechanical attrition and grinding processes have the disadvantages that powders only be produced up to certain fineness and with relatively broad particle-size distribution. As a matter of fact, with the currently familiar large-scale process for manufacturing powders it is rarely possible, or only possible with considerable difficulty, to produce powders having average particle sizes of less than 500 nm.
Particularly Mercury Cadmium Telluride and Mercury related compounds have been prepared by wet chemical methods (Journal Ref. 12, 13, 16). Which have the limitations of handling toxic chemicals and the production cost due to the unavailability of technique required to prepare the large amount of the material.
OBJECTIVES OF THE INVENTION
Method of making nanoparticles involves solvothermal method
In one aspect, the invention features a method of manufacturing Mercury Cadmium Telluride nanoparticles (Hg1-xCdxTe). The method

includes an M-containing salt is a non-organometalic compound e.g. free from metal-carbon bonds. M containing salt can be a metal halide, metal carboxylate, metal carbonate and metal hydroxide. The metal containing salt is less expensive and safer to use than organometallic compounds, such as metal alkyls. For example the M-containing salts are stable in air, whereas metal alkyls generally unstable in air. M-containing salts such as halide, carboxylate, hydroxide or carbonate salts are stable in air and allow the preparation of the nanoparticles to be manufactured under less rigorous conditions than corresponding metal alkyls.
For example M-containing salts, where M is Cadmium, the salts include Cadmium acetylacetonate, cadmium iodide, cadmium bromide, cadmium hydroxide, cadmium carbonate, cadmium acetate, cadmium chloride, cadmium oxide, Cadmium powder.
In another aspect, the invention features a method of manufacturing nanoparticles includes M-containing salts, where M is Mercury, the salts include Mercury acetylacetonate, mercury iodide, mercury bromide, mercury hydroxide, mercury carbonate, mercury acetate, mercury oxide, mercury chloride etc.

In another aspect the invention features the preparation of nanoparticles for all compositions of x=0 to x=l in Hg1-xCdxTe.
In yet another aspect, the invention features a coordinating solvent is a compound having donor lone pair that, for example, has a lone electron pair available to coordinate to a surface of the growing nanoparticle. Solvent coordination can stabilize the growing nanoparticles. Typical coordinating solvents include solvents such as pyridine, amine, ethyleneglycol, diethylamine, ethylenidiamine and the mixture thereof.
In yet another aspect, the invention features a reducing agent any compound which is capable of reducing the M of the M-containing salt. The M-containing salt reducing agents to produce the metal precursor for the formation of nanoparticles includes the reducing agents for example Hydrazine, Lithium Aluminium Hydride, Sodium Borohydride, ferrous chloride and other reducing agents.
In yet another aspect, the invention features includes the preparation of core/shell structure of nanoparticles, for example CdTe/HgTe/CdTe.

In yet another aspect, the invention features include the preparation of doped nanoparticles (both p-type and n-type) the dopants includes CI, Br, I, B, As, Sb.
In yet another aspect the method features, the preparation of other semiconductor nanoparticles with different compositions (x=0 to x=l) this includes the preparation of nanoparticles of Hgi_xMxN (for x=0 to x= 1) for example, M can be Cd, Zn, AI, Mn, Pb, Mg, Ga, In, Sb, As, Tl and N can be S, Se, Te and the mixtures thereof.
In yet another aspect the invention features monitoring the size
and the size distribution of a population including of the nanoparticles
changes the reaction temperature in response to a spreading of the size
distribution.
In yet another aspect the invention features monitoring the size and size distribution of a population including the nanoparticles synthesized with different compositions.
DESCRIPTION OF THE FIGURES
Fig. (1) X-ray diffraction pattern of Sample A
Fig. (2) ED AX spectra of Sample A
Fig. (3) X-ray diffraction pattern of Sample B

Fig. (4) EDAX spectra of Sample B
Fig. (5) X-ray diffraction pattern of Sample C
Fig. (6) X-ray diffraction pattern of Sample D
Fig. (7) Transmission Electron Micrograph of Sample B
Fig.(8) Histogram for TEM Micrograph of Sample B
Fig.(9) TEM Selected area diffraction pattern recorded for Sample B
Fig. (10) Transmission Electron Micrograph of Sample C
Fig (11) Histogram for TEM micrograph of Sample C
Fig. (12) TEM Selected area diffraction pattern recorded for Sample C
Fig. (13) Transmission Electron Micrograph of Sample D
Fig. (14) Histogram for TEM Micrograph of Sample D
Fig. (15) TEM selected area diffraction pattern recorded for Sample D
DESCRIPTION OF THE INVENTION:
The present invention relates to -
A method for synthesis of nanoparticles of Mercury Cadmium Telluride (MCT) The said method comprising the steps of
a) taking a salt of mercury in a SS autoclave.

b) adding a cadmium salt or cadmium powder to the said autoclave.
c) adding a tellurium powder.
d) adding a coordinating solvent to the above mixture.
e) adding about 5-10mg or 3-5ml of a strong reducing agent to the resulting mixture.
f) closing the said autoclave and keeping it in an oven at temperature of 80°C-200°C for a period of 10-50 hours.
g) allowing the said autoclave to cool down naturally inside the oven to room temp.
h) filtering the resulting contents of the autoclave.
i) washing the residue with double distilled water and then
preferrably with absolute ethanol. j) drying the resulting residue in vacuum for 1-3 hours at a
temperature of 40-75°C. - The said method wherein the said mercury salt is Mercury
Chlorate, more preferably Mercury Oxide most preferably
Mercury Chloride. - The said method wherein as claimed above wherein the said Cd
source is Cadmium Iodide or Cadmium Bromide or Cadmium
Hydroxide more preferably Cadmium Oxide or Cadmium

Carbonate most preferably Cadmium Acetate or Cadmium Chloride or Cadmium powder.
- The said method wherein as claimed above wherein the said Te
source is Te powder
- The said method wherein as claimed above wherein the said autoclave has a Teflon coating on the inside.
- The said method wherein as claimed above wherein the autoclave
has a platinum liner on the inside.
- The said method wherein as claimed above wherein the said coordinating solvent is a compound having one or more oxygen or Nitrogen coordinating atoms.
- The said method wherein as claimed above wherein the said coordinating solvent is preferrably an N-chelating agent containing N with lone pair of electrons, or coordinating solvent containing Oxygen with lone pair of electrons.

- The said method wherein as claimed above wherein the said coordinating solvent is a mixture of the solvents as claimed above.
- The said method wherein the said solvent is preferrably pyridine, ethyleneglycol more preferably dietylamine or ethylenediamine most preferably amine.

- The said method wherein the said reducing agent is preferrably Lithium Aluminum Hydride, Sodium Borohydride, Hydrazine most preferrably Iron Chloride.
- The said method wherein the autoclave is heated preferrably between 140-180°C, more preferrably between 170-180°C.
- The said method wherein period of heating the autoclave is preferrably between 16-24 hours.
- The said method wherein the method claimed above can be applicable for all the composition from x= 0 to x=l in Hgi_xCdxTe.
- The said method wherein MCT nanoparticles obtained from the method such that said particles can be produced in grams by each iteration of the said method.
- The said method wherein MCT nanoparticles obtained from the method as claimed above such that the said nanoparticles have core/shell structure.
- The said method wherein MCT nanoparticles obtained from the method claimed above such that the shapes of the said nanoparticles are spherical or rod type or disc type or irregular shape.

- The said method wherein MCT nanoparticles obtained from the method as claimed above such that the said nanoparticles do not need a coating for preventing agglomeration.
- The said method wherein MCT nanoparticles obtained from the method as claimed such that the said nanoparticles can be doped (both p and n-type) by the said method
- The said method wherein, the dopants can be CI, Br, I, B, As, Sb.
Advantages of the proposed method ;
Relatively Solvothermal method is a simple and cost effective technique for the synthesis of binary and ternary semiconductor Nanocrystallites. In the Solvothermal synthesis the reaction takes place inside a pressure vessel namely Teflon-Stainless-Steel autoclave, in which the reactants along with the solvents will be heated well above the boiling points of the solvents, so that the autogenous pressure far exceeds the ambient pressure. This automatically raises the effective boiling point of the solvent. Such a method is extensively used in the preparation of inorganic solids, and in particular of zeolite materials. In case water is used as solvent it is called a hydrothermal synthesis, if any

organic solvent is used then it is called as Solvothermal synthesis. Solvothermal synthesis is relatively low temperature and time effective technique.
In the Solvothermal synthesis we can control growth rate, particle size and particle size distribution and most importantly Solvothermal method can be used for large scale production with greater control over the particle size, which is one of the advantages of this method compared to the other semiconductor nanocrystals producing methods.
The main advantages of the Solvothermal method are (a) Kinetics of reaction is greatly increased with a small increase in temperature, (b) New metastable products can be formed, (c) single crystals can be obtained, (d) High purity products can be obtained from impure feedstocks, (e) No precipitants are needed in many cases and thus process is cost effective, (f) pollution is minimized because of the closed system conditions.
We can use reducing agents in very minute quantity, which will reduce the metal containing salts into their corresponding ions, which further take part in the reaction for the formation of final product.
It is not required to use heavy and/or expensive equipment like a high power laser source and high vacuum equipment, therefore, reduces

the production cost dramatically. In case of the synthesis of alloy compound semiconductors it is difficult to get the controlled composition, but by using Solvothermal method we can synthesize the controlled alloy compositions. It is also possible to synthesize nanocrystals with core/shell structure. Solvents like water, Ethylenediamine, Pyridine, Diethylamine, Ethyleneglycol and other coordinating organic solvents can be used. Ethylenediamine has been widely used in the synthesis of semiconductor and other nanocrystals preparation by the Solvothermal method. Solvothermal method can be used for the synthesis of doped semiconductor nanocrystals by just adding the dopant element in the Solvothermal process, which could be a simple way of preparing the doped semiconductor nanocrystals. The materials, which are difficult to dope, can be doped by using Solvothermal process.
The said nanoparticles can also be prepared by the following methods
(I) Microwave Hydrothermal or Microwave Solvothermal.
(II) Electrochemical Hydrothermal method or Electrochemical Solvothermal method.

(III) The said nanoparticles can also be prepared by Sonochemical Hydrothermal or Sonochemical Solvothermal method.
(IV) The said nanoparticles can also be prepared by Ultrasonic-Hydrothermal or Ultrasonic-Solvothermal method.
Experimental details with examples:
M-containing salts have been used as the source materials for both the Metals for Example Cd and Hg. Reducing agent is also used. Ethylenediamine had been used as a solvent. The autoclave was filled with 80% of the solvent and kept in oven at 180°C for 24 hours, then cooled to room temperature. The reaction product was washed with absolute ethanol, double distilled water to remove the organic and inorganic impurities. The product was dried in Vacuum for 2 hours. The product was characterized by X-ray diffraction, Energy dispersive x-ray analysis and Transmission electron microscopy.
X-ray diffraction studies confirmed the formation of MCT nanoparticles. The average particle size calculated from Debye-Scherrer formula and found to be varied from 7-12 nm, which depends on the original composition of the Hg1-xCdxTe. Different composition of MCT

has been prepared by changing the amounts of precursors in the Solvothermal process. X-ray diffraction studies also revealed the formation of CdTe nanoparticles instead of MCT when the reaction takes place in absence of reducing agents. X-ray diffraction patterns clearly showed the presence of CdTe peaks and Metal-Salts taken as precursors in the Solvothermal process. This clearly tells us that the presence of reducing agents is necessary for the formation of MCT nanoparticles. The role of reducing agent in the process is to reduce the metal salts to its metal ions. In absence of reducing agents it is not possible to generate the metal ions in the process, so the desired product is not been achievable. The nanoparticles synthesized in presence of reducing agents shows the formation of MCT nanoparticles and no metal salts.
Energy dispersive x-ray analysis studies revealed the composition of the nanoparticles. Energy dispersive x-ray analysis also revealed the information that the nanoparticles prepared in absence of reducing agent contains the salts of the Metals taken as precursors in the Solvothermal process. Whereas the nanoparticles synthesized in presence of reducing agent showed the formation of MCT nanoparticles.

The MCT nanoparticles thus prepared can be used for the thin film preparation by different methods like Spray deposition and Spin coating. The reduction in the melting point of the nanoparticles compared to the bulk material will allow us to prepare the thin film at lower temperatures at about 160-200°C by spray deposition technique. We can deposit the films on different substrates like glass, quartz and silicon wafers. In our lab we were able to synthesize the nanorods of binary II-VI semiconductor nanoparticles by modifying the spray process (Ref. 19), for example nanorods of CdSe, CdTe and HgTe. We can apply the same process for the synthesis of nanorods of MCT also. In our lab we also able to produce Nanofibers of doped II-VI semiconductor materials like CdSe, CdTe and HgTe. We may get the nanofibers of doped MCT thin films once we are able to prepare doped nanoparticles by Solvothermal method.
Transmission electron microscopy (TEM) can provide information about the size, shape, and distribution of the nanoparticles size. Powder X-ray diffraction (XRD) patterns can provided the most complete information regarding the type and quality of the crystal structure of the nanocrystallites. Estimation of size is also possible, for

example the particle size can be calculated directly by transmission electron microscopy images or estimated from X-ray diffraction data using, for example the Debye-Scherrer equation. Details of the instruments used for characterization (a) Transmission electron microscopy
Nanoparticle size, morphology and structure were measured by TEM on Philips CM 12 electron microscopy with accelerating voltage available from 20 kV to 120kV and point to point resolving power of 0.4 nm. In the present study the microscopy was operated at an accelerating voltage of 100 kV to minimize beam damage to the sample.
Nanoparticles were deposited from dilute solution onto a amorphous carbon supported 200 mesh copper grids. One drop of nanoparticle solution in either toluene or chloroform was deposited on to the grid and allowed to evaporate. The sample was then washed with methanol to remove the excess organic compounds and placed in dessicator over night.
Average sizes and morphologies were measured at 1, 40,000 times magnification. Average particle size and size distributions were determined by counting at least 500 nanoparticles for sample for statistical purposes.

(b) Powder X-ray diffraction
Powder X-ray diffraction was performed on a RIGAKU Giegerflex-D/max- RB-RU 200 X-ray diffractometer using Cu K alpha radiation (wavelength 1.5418 A0) from a rotating anode; capable of generating a maximum power of 12 KW is used as a source of radiation. In the present studies the diffractometer was operated at 4 KW.
The crystallite size was calculated by using Debye-Scherrer equation.
(c) Energy dispersive X-ray analysis (EDAX)
For the Composition analysis of the MCT nanoparticles mined by Energy Dispersive X-ray Analysis (EDAX) ISIS 200 was used at the operation voltage of 20KV and current 10"9 ampere. Results
Four different types MCT nanoparticles have been prepared. Sample A has Hg and Cd in the ration 40:60 and no reducing agent is used in the process. Sample B has Hg and Cd in the same ratio as in Sample A, but the reducing agent is added. Sample C and D have Hg and Cd in the ratios 50:50 and 70:30, respectively and in both the samples reducing agent is used.

Fig.l shows the X-ray diffraction pattern of sample A, where we use Mercury compound along with Cd and Te. Diffraction peaks corresponding to CdTe and Mercury Chloride are observed. The ED AX analysis (Fig.2) for Sample A also shows the presence of Mercury in the unreacted form and a large amount of Chlorine can also be seen. This means that the mercury salt is not reduced, if it is so, there would not be any presence of Chlorine. Thus it can be concluded that a suitable reducing agent needed for the creation of MCT nanoparticles during Solvothermal method. The role of this reducing agent is to reduce the metal compounds to yield metal ions, which then combine with Te. Therefore, if we use Mercury salt along with Cd and Te only (Sample A), the process yields CdTe nanoparticles.
The role of reducing agent can be clearly seen from Fig.3, which shows the X-ray diffraction pattern of the sample B. Fig.5 and Fig.6 shows the X-ray diffraction pattern of the samples C and sample D. All the peaks corresponding to cubic MCT are observed, with (111) peak dominant. The average crystallite size calculated from X-ray diffraction pattern using Debye-Scherrer formula is found to be 7-12 nm. A small peak corresponding to Te02 can also be seen in Sample C (Fig.5). This may be due to the presence of some unreacted Te, which converts to Te02.

Fig (4) shows the ED AX spectra of the sample B, which clearly show little or no chlorine presence. This means that when we use reducing agent the mercury in the mercury chloride will get reduce and generates mercury ions, which then takes place in the formation of MCT nanoparticles. Both X-ray diffraction and EDAX data confirms the role of the reducing agent in MCT nanoparticles preparation. With increasing Hg amount, the EDAX spectra show the corresponding increase in Hg peak.
Fig.7, 10 and 13 shows the TEM micrographs of the MCT nanoparticles of Sample B, Sample C and Sample D respectively. The shape of the particles is not exactly spherical, but random. This is as expected, because in the Solvothermal method the shape and size of the nanoparticles depends on the solvent used, reaction temperature and time. Solvent and reaction temperature play a crucial role in controlling the nucleation and growth of crystallites. Ethylenediamine has the ability to create the random shaped particle due to its high coordinating nature towards the metal Cation. Different shapes of II-VI nanoparticles (e.g., Nanorods) with different solvents have been reported. The average particle size varied from ~10-15 nm. The histograms plotted (Fig. 8, 11, and 14) for particle size and size

distribution of each of the samples B, C and D (from TEM micrographs of the samples) also show the average particle size from 10-15 nm for the sample B, C and D. Fig. 9, 12 and 15 shows the Selected Area Diffraction patterns recorded on the TEM images of Sample B, C and D respectively. The lattice parameter (a) calculated from the diffraction patterns is found to be ~0.6464 nm, which is close to the standard MCT value. In our experiments we observed the nanoparticles with narrow size distribution can be obtained by dispersing the nanoparticles in 1-Butanol.
The particle size distribution can be refined by size selective precipitation with a proper solvent for the nanoparticles, such as methanol/butanol as described in U.S. patent no. 6,320901. For example nanopartilces can be dispersed in solution of 10% butanol in hexane. Methanol can be added drop-wise to this stirring solution until opalescence persists. Separation of supernatant and flocculate by centrifugation produces a precipitate enriched with the largest particles in the sample. Size selective precipitate can be carried out in a variety of solvent pairs, including pyridine/hexane and chloroform/methanol.

We claim
1. A method for synthesis of nanoparticles of Mercury Cadmium Telluride (MCT), the said method comprising the steps of
a) taking a salt of mercury in a SS autoclave.
b) adding a cadmium salt or cadmium powder to the said autoclave.
c) adding a tellurium powder.
d) adding a coordinating solvent to the above mixture.
e) adding about 5-10mg or 3-5ml of a strong reducing agent to the resulting mixture.
f) closing the said autoclave and keeping it in an oven at temperature of 80°C-200°C for a period of 10-50 hours.
g) allowing the said autoclave to cool down naturally inside the oven to room temp.
h) filtering the resulting contents of the autoclave.
i) washing the residue with double distilled water and then
preferrably with absolute ethanol. j) drying the resulting residue in vacuum for 1-3 hours at a
temperature of 40-75°C.

2. A method as claimed in claim 1(a) wherein the said mercury salt is Mercury Chlorate, preferably Mercury Oxide more preferably Mercury Chloride.
3. A method as claimed in claim 1(b) wherein the said Cd source is Cadmium Iodide or Cadmium Bromide or Cadmium Hydroxide more preferably Cadmium Oxide or Cadmium Carbonate most preferably Cadmium Acetate or Cadmium Chloride or Cadmium powder.
4. A method as claimed in claim 1(d) wherein the said coordinating solvent is a compound having one or more oxygen or Nitrogen coordinating atoms.
5. A method as claimed in claim 1 wherein the said coordinating solvent is a mixture of the solvents claimed in claim 4.
6. A method as claimed in claim 4 wherein the said solvent is preferrably pyridine, ethyleneglycol more preferably dietylamine or ethylenediamine most preferably amine.
7. A method as claimed in claim 1(e) wherein the said reducing agent is preferrably Lithium Aluminum Hydride, Sodium Borohydride, Hydrazine most preferrably Iron Chloride.

8. A method as claimed in claim 1(f) wherein the autoclave is heated preferrably between 140-180°C, more preferrably between 170-180°C.
9. A method as claimed in claim 1(f) wherein the said period of heating the autoclave is preferrably between 16-24 hours.
10.A method as claimed in claim 1 wherein the said MCT nanoparticles of any composition from x= 0 to x=l in Hg1-xCdxTe can be made by this method.
11. MCT nanoparticles obtained from the method of claim 1 such that said particles are produced in grams by each iteration of the said method.
12. MCT nanoparticles obtained from the method claimed in claim 1 such that the said nanoparticles have core/shell structure.
13. MCT nanoparticles obtained from the method claimed in claim 1 such that the shapes of the said nanoparticles are spherical or rod type or disc type or irregular.
14. MCT nanoparticles obtained from the method claimed in claim 1 such that the said nanoparticles do not need a coating for preventing agglomeration.

15. MCT nanoparticles obtained from the method claimed in claim 1
such that the said nanoparticles can be doped (both p and n-type)
by the said method
16. A method for synthesis of nanoparticles of mercury cadmium telluride substantially as herein described with reference to the accompanying examples and figures.
17. MCT nanoparticles substantially as herein described with reference to the accompanying examples and figures.

Documents:

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Patent Number

270890

Indian Patent Application Number

861/DEL/2005

PG Journal Number

05/2016

Publication Date

29-Jan-2016

Grant Date

26-Jan-2016

Date of Filing

04-Apr-2005

Name of Patentee

INDIAN INSTITUTE OF TECHNOLOGY NEW DELHI

Applicant Address

HAUZ KHAS, NEW DELHI-110016 INDIA.

Inventors:

#	Inventor's Name	Inventor's Address
1	DUTTA VIRESH	CENTRE FOR ENERGY STUDIES INDIAN INSTITUTE OF TECHNOLOGY HAUZ KHAS, NEW DELHI-110016, INDIA.
2	ARNEPALLI RANGA RAO	CENTRE FOR ENERGY STUDIES INDIAN INSTITUTE OF TECHNOLOGY HAUZ KHAS, NEW DELHI-110016, INDIA.

PCT International Classification Number

H01L 31/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA