Title of Invention

"AN IMPROVED PROCESS FOR THE PREPARATION OF SEMICONDUCTOR NANOCLUSTER OR POLYMER COMPOSITE USEFUL FOR THE APPLICATIONS IN NONLINEAR OPTICS"

Abstract The invention relates to a synthetic grass turf assembly for installation on a supporting soil substrate to provide a game playing surface that combines the feel of natural turf with a wear resistance of synthetic turf. The turf assembly includes a pile fabric with a flexible sheet backing and rows of upstanding synthetic ribbons. A unique infill layer consisting of three distinct graded courses of particulate material is disposed interstitially between the upstanding ribbons upon the upper surface of the backing and of a depth less than the length of the ribbons.
Full Text The present invention relates to an improved process for prepartion of semiconductor nanocluster or polymer composite useful for appliccations in nonlinear optics. The invention particularly relates to the synthesis of semiconductor nanocluster or polymer composite using gamma radiation useful for applications in nonlinear optics. More specifically the process of the invention employs γ - ray induced polymerisation of acrylates and nitriles in presence of semiconductor or metal clusters. By the process of the present invention composite of semiconductor nanocluster namely CdS and ZnS and polymer matrix viz. polyacrylonttrile, polymethyl methacrylate and poly methyl acrylate has been obtained in the temperature range 0°C to 50°C.
Semiconductor nanocluster / polymer composites are technologically important due to advances in nonlinear optics. Advances in nonlinear optics hold promise for important applications in optical information processing, telecommunications and
integrated optics, m order to perform various optical functions, me second or third order
nonlinear optical response of a material for an electric field at optical or radio frequency is required. Since, most of the applications critically depend upon the materials used; the primary emphasis is to explore new materials and synthesis routes. The potential advantage of polymeric materials is possibility of easy process developments. Semiconductor nanocluters embedded in transparent polymeric matrices exhibit large third order nonhnearities due to the refractive index boundary provided by the physical presence of interface between the cluster and the matrix and can be very promising candidates in all optical switching devices.
In the prior art, few methods are proposed for the synthesis of semiconductor nanochister/ polymer composites. One of the simplest method to prepare CdS cluster doped polymers, as disclosed by Y.Wang and N.Herron in J. Nonlinear Opt.Phys. 1(4): 638 (1992), which involves metal ion exchange into ionic domains of the nafion polymer film followed by reaction with H2S.
The methods for photoconducting compositions are invented [ U.S. Patent No. 5238607 ] which comprise photoconducting polymer(s) and effective amounts of semiconductor clusters selected from the group consisting of IIB-VIB, IIB-VB, IIIB-VB, IIIB-VIB, IB-VIB and IVB-VIIB. Photoconducting compositions provided by this method (e.g. films) are useful as photoconducting elements (or components thereof) for electrostatic imaging.
Another process, a composition of matter comprising particles of semiconductor material in a specified copolymer matrix is disclosed [ U.S. Patent No. 4738798 ] The copotymer matrix comprising atleast one. alpha, -olefin having the formula RCH=CH2 where R is selected from hydrogen and straight and branched alkyl groups having from 1 to 8 carbon atoms, and atleast one.alpha., β-ethylenically unsaturated carboxylic acid having from 3 to 8 carbon atoms and 1 or 2 carboxylic groups. The method also comprises contacting an ionic copotymer precursor with appropriate anions to form the particles of semiconductor material in copotymer matrix.
Yet another process for the production of third-order nonlinear optical material having a metal oxide contained in a transparent polymer is disclosed [U.S. Patent No.
S993701] where the metal oxide manifests the third-order nonlinear optical effect owing to the so-called band-filling phenomenon. The third-order nonlinear optical material according to this invention is produced by introducing a metal oxide in a transparent polymer e.g. poryacid.
Yamamoto et al., Inorganica Chimica Acta, 104: L1-I.3 (198S) have proposed the preparation of organosols of CdS and CuS and their utilisation in preparing MS-poly(acrylonitrile) composites (M= Cd, Cu). Recently, Zhengping Qiao et aL, J. Mater. Chem. 9:1001 (1999) synmesised PbS / poryacrylonitrile composite using y radiation where a solution containing carbon sutfide, lead acetate, acrylonitrile and isopropanol in anhydrous ethanol was irradiated in me field of a 2.59 x 1015 Bq 60Co γ- ray source.
In the prior art, as disclosed in U.S. Patent No. 5238607, only photoconducting polymers are used and the composites are synmesised far electrostatic imaging processes. The process explains physical dispersion of semiconductor nanoparticles in polymeric matrix.
In the other process, explained in U.S.Patent No.5432635 for the synthesis of nonlinear optical materials comprising of metal and/or semiconductor fine particles in polymers , ceramic or a glass matrix. A fine metal particles dispersion in transparent polymers is carried out by thermal fusing method. In mis process, fine particles of metal can be subjected to degradation during thermal fusing. Semiconductor cluster dispersion is also carried out by physical mixing with metal salt and men treatment with H2S.
In physical dispersion of semiconductor nanocluster with polymers, homogeneity in the composite cannot be achieved and depends on other process parameters. There is also a possibility of solvents getting incorporated in the composites which can act as impurity. In the present process three drawbacks will be eliminated and pure product can be prepared.
The main objective of the invention is to provide a process for the production of semiconductor nanocluster/polymer composites on a large scale for their possible usage in nonlinear optics.
Accordingly, the present invention provides an improved process for preparation of a semiconductor nanocluster or polymer composites useful for the applications in nonlinear optics, characterized in that γ- ray induced polymerization of acrylates and nitriles in presence of metal clusters , which comprises preparing the solution of metal cation selected from the group consisting of ZnCI2, Zn(NO3)2, Zn(CH3COO)2, Zn(HCOO)2, CdCI2, Cd(NO3)2, Cd(CH3 COO)2, and Cd(HCOO)2 using a solvent as described herein , adding a capping agent selected from the group consisting of thiophene, 3-mercapto propionic acid, thiophenol, pentane dithiol and octane dithiol to the above solution, treating the above reaction mixture with hydrogen sulfide or hydrogen selenide under stirring, and irradiating with γ-rays at a temperature ranging between 0°C to 50°C for a period of 2 to 120 hrs., at a dose rate of 2000 rad/min in presence of a monomer as herein described to obtain the desired nanocomposite followed by washing the nanocomposite with an organic solvent as described herein and dried in oven to obtain the polymer composite in powder form.
In an embodiment of the present invention, the metal cation used is Cd or Zn derived from the salts of these cations selected from the group consisting of ZnCI2, Zn(NO3)2, Zn(CH3 COO)2, Zn(HCOO)2, CdCI2, Cd(NO3)2, Cd(CH3 COO)2, Cd(HCOO)2.
In an embodiment of the present invention, the solvent used for preparing solution of the metal cation used is selected from water and organic solvent selected from the group consisting of toluene, hexane, isopropanol, methanol, acetonitrile and mixture thereof.
In yet another embodiment of the present invention, the capping agent used is aromatic or aliphatic organic molecule, selected from the group consisting of thiophene, 3-mercapto propionic acid, thiophenol, pentane dithiol and octane dithiol, preferably selected from thiophene and 3-mercapto propionic acid.
In yet another embodiment of the present invention, the monomer used is selected from the group consisting of acrylonitrile, methyacrylate, methyl. methacrylate, styrene or mixtures thereof, preferably acrylonitrile, methyacrylate, methyl methacrylate.
In still another embodiment of the present invention, the solvent used for washing the composite is selected from water and organic solvent selected from the group consisting of toluene, hexane, isopropanol, methanol acetonitrile preferably selected from methanol and acetonitrile.
In this process, the semiconductor nanocluster/ polymer composites are synthesised using γ radiation. The polymerisation of the monomer is initiated by high photon flux viz. γ-rays. Semiconductor nanociuster is prepared through the treatment of metal ions with H2S or Na2S. The appropriate capping agent is chosen so as to form electrostatic linkage with the suitable monomer, y - ray induced polymerisation is the well-known process to synthesis polymers and is advantageous in away that it produces pure products.
Accordingly, the present invention provides the materials for all-optical switching applications, usually, in all - optical switching, low optical loss is as important as optical nonlinearity. At present, the only good material for all - optical switching is still glass, in spite of it's very low nonreasonant x(3) , ~ 10"14 esu. About 100m of glass is needed for complete switching. This length can be reduced to less than 1 m by using the material
with nonresonant x(3) ~ 10-12 esu. There are many semiconductors and few polymers with nonresonant %(3) of mat magnitude, but none can be grown in to meter length with the optical loss as low as glass. This method will provide the best compromise for optical nonlinearity and optical loss. This method is most suitable for acrylates and nitrites, which can be made in to sheets of large area, and simultaneously the process exploits the advantages of chemical route enabling the synthesis of monodispened clusters.
The invention provides a composition of semiconductor or metal nanoclusters particularly semiconductor nanoclusters in specific transparent polymeric hosts. As the diameter of semiconductor nanochuters approaches exciton Bohr diameter, ifs electronic properties start to change. This so-called quantum size effect is manifested as the olue shift in the exciton energy or as a blue shift in the optical band gap. For CdS quantum size effect occurs for the exciton diameter below 50-60 A.
As used herein, the term semiconductor refers to materials with the band gap between 0.2-4 eV. Semiconductor materials suitable for the present composites include the group consisting of CdS, ZnS, CdSe and ZnSe.
Typically, these semiconductor clusters are surrounded by dielectrics such as polymer, glass or solvent having low refractive indices than inorganic semiconductors. Because of this boundary established by different refractive indices, the field intensity near, at and inside the cluster surface can be enhanced considerably compared to incident intensity. This local field enhancement effect can have important consequences on the photophysical and nonlinear optical properties of these semiconductor clusters, m the present composites the host comprises of polymers selected from poly(acrylonitrile),
poly(methyacrylate), poly(methymethacrylate), poly(styrene), acrylonitrile /styrene copolymer, polyimide, polycarbonate.
The present composite is prepared by dissolving salt of semiconductor material selected from the cation such as Cd2+ and Zn2+ in an appropriate solvent selected from toluene, hexane, isopropanol, methanol, acetonitrile, water and mixture of. To this mixture the capping agent selected from thiophene, 3-mercapto propionic acid, thiophenol, pentane dithiol and octane dithiol is added. Preferable examples of metal-ion producing compounds of Zn or Cd include ZnCI2, Zn(NO3)2, Zn(CH3 COO)2, Zn(HCOO)2, CdCI2, Cd(NO3)2, Cd(CH3 COO)2,
Cd(HCOO)2. Metal ions of Zn or Cd are reacted with H2S or Na2S or H2Se under
constant stirring to getsmall clusters of semiconductors of the group consisting of
CdA, ZnS. CdSe and ZnSe. The minimum cluster diametersobtained with this method is ~ 15A. This cluster solution is then treated by y radiation at temperature ranging from 0°C to 50°C for the duration of 2 hrs. to 120 hrs. with the dose rate of 2000 rad/min in the preence of specific monomer which isdissolved in the cluster solution. The semiconductor cluster/polymer composites are then washedfor several times eith the solvent selectedfrom acetonitrile, acetone , methanol to remove by product and unpolymerised monomer.
These composites are characterised by optical absorption spectra, XRD and HRTEM to confirm the imbibement of semiconductor nanoclusters in the polymeric host. The powder method was employed to study second order nonlinearity in these

composites. The free standing films of these composites can be easily prepared. These composites have found to show interesting size dependent nonlinear optical properties.
The process of the present invention is described herein below by following examples, which are illustartive only and should not be construed to limit the scope of the invention, in any manner.
EXAMPLE 1
This example illustrates the preparation of ZnS nanocluster/polyacrylonitrile composite.
Solution of ZnS nanocrystals capped with 3-mercapto propionic acid was prepared in the mixture of memanol and acetonitrile. In brief, solution of ImM Zn acetate and 1 mM 3-mercapto propionic acid was prepared in the mixture of water and acetonitrile with a volume ratio of 1:1 where 3-mercapto propionic acid served as a capping agent. The mixture was subsequently treated with H2S gas under constant stirring. The ZnS particle solution thus prepared was then y irradiated at room temperature for 30 hrs. with the dose rate of 2000 rad/min in the presence of acrylonitrile monomer to obtain ZnS nanochuter/ poryacrylonitrile (PAN) composites. In other words, polymerisation of acrylonitrle was initiated by y radiation. The colourless ZnS nanocrystal/PAN composite powder was washed with distilled acetonitrile to remove unreacted monomer followed by centrifugation. This washing procedure was repeated several times and recovered powder was then dried in oven. The details regarding particle size and order of nonlinearity observed is mentioned in Table L
TABLE I (Table Removed)
EXAMPLE!
This example illustrates the preparation of CdS nanochister/poly (methyl acrylate) composite.
Solution of CdS nanocrystals capped with thiophene was prepared in the mixture of water and acetonitrile. In brief, solution of 1mM cadmium acetate was prepared in 10 ml water and solution of 1 mM tiuophene was prepared in acetonitriile. The two solutions were mixed under stirring. Thiophene served as a capping agent The mixture was subsequently treated with H2S gas. The CdS particle solution thus prepared was then y irradiated at room temperature for 24 hn. with the dose rate of 2000 rad/min in the presence of methyl acrylate monomer to obtain CdS nanochister/ poly (methyl acrylate) (PMA) composites. The transparent colourless gel thus obtained was washed with distilled acetonitrile to remove unreacted monomer followed by centrifugation. This washing procedure was repeated several times and recovered gel was men dried in an oven. The details regarding particle size and order of nonlinearity observed is mentioned in Table I.



We Claim:
1. An improved process for preparation of a semiconductor nanocluster or
polymer composites useful for the applications in nonlinear optics,
characterized in that y- ray induced polymerization of acrylates and nitriles in
presence of metal clusters , which comprises preparing the solution of metal
cation selected from the group consisting of ZnCI2, Zn(NO3)2, Zn(CH3COO)2,
Zn(HCOO)2, CdCI2, Cd(NO3)2, Cd(CH3 COO)2, and Cd(HCOO)2 using a
solvent as described herein , adding a capping agent selected from the group
consisting of thiophene, 3-mercapto propionic acid, thiophenol, pentane dithiol
and octane dithiol to the above solution, treating the above reaction mixture
with hydrogen sulfide or hydrogen selenide under stirring, and irradiating with
Y-rays at a temperature ranging between 0°C to 50°C for a period of 2 to 120
hrs., at a dose rate of 2000 rad/min in presence of a monomer as herein
described to obtain the desired nanocomposite followed by washing the
nanocomposite with an organic solvent as described herein and dried in oven
to obtain the polymer composite in powder form.
2. An improved process as claimed in claims 1 , wherein the solvent used for
preparing solution of the metal cation is selected from water and organic
solvent selected from the group consisting of toluene, hexane, isopropanol,
methanol, acetonitrile and mixture thereof.
3. An improved process as claimed in claims 1-2, wherein the capping agent
used is preferably selected from thiophene and 3-mercapto propionic acid.
4. An improved process as claimed in claims 1 - 3, wherein the monomer used
is selected from the group consisting of acrylonitrile, methyacrylate, methyl
methacrylate, styrene and mixtures thereof, preferably selected from
acrylonitrile, methyacrylate and methyl methacrylate.
5. An improved process as claimed in claims 1-5, wherein the organic solvent
used for washing the composite is selected from the group consisting of
toluene, hexane, isopropanol, methanol and acetonitrife preferably selected
from methanol and acetonitrile.
6. An improved process for the preparation of a semiconductor nanocluster or
polymer composite useful for the applications in nonlinear optics substantially
as herein described with reference to the examples.



Documents:

1210-del-2000-abstract.pdf

1210-del-2000-claims.pdf

1210-del-2000-correspondence-others.pdf

1210-del-2000-correspondence-po.pdf

1210-del-2000-description (complete).pdf

1210-del-2000-form-1.pdf

1210-del-2000-form-19.pdf

1210-del-2000-form-2.pdf

1210-del-2000-form-3.pdf

1210-del-2000-gpa.pdf

1210-del-2000-petition-137.pdf


Patent Number 212645
Indian Patent Application Number 1210/DEL/2000
PG Journal Number 50/2007
Publication Date 14-Dec-2007
Grant Date 10-Dec-2007
Date of Filing 26-Dec-2000
Name of Patentee COUNCIL OF SCIENTIFIC & INDUSTRIAL RESEARCH
Applicant Address RAFI MARG, NEW DELHI-110 001, INDIA,
Inventors:
# Inventor's Name Inventor's Address
1 SUSHAMA PETHKAR, NATIONAL CHEMICAL LABORATORY, PASHAN, PUNE-411 008, MAHARASHTRA, INDIA.
2 ANJALI ANAND ATHAWALE GANESHKHIND ROAD, PUNE 411 007, MAHARASHTRA INDIA.
3 NA NATIONAL CHEMICAL LABORATORY, PASHAN, PUNE 411 008, MAHARASHTRA, INDIA
4 KUNJUKRISHNA PILLAI VIJAYAMOHANA NATIONAL CHEMICAL LABORATORY, PASHAN, PUNE 411 008, MAHARASHTRA, INDIA.
PCT International Classification Number H01B1/06
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA