Nano aggregates of molecular ultra small clusters of noble metals and a process for the preparation thereof

Patent metadata

Field	Value
Publication number	US-9352394-B2
Application number	US-201414415312-A
Country	US
Kind code	B2
Filing date	Feb 19, 2014
Priority date	Feb 19, 2013
Publication date	May 31, 2016
Grant date	May 31, 2016

Abstract

The present invention discloses size controlled and stabilized nano-aggregates of molecular ultra small clusters of noble metals and a process for the preparation thereof. The present invention discloses single source multicolor noble metal spherical and uniform nano aggregates of 10-22 nm made up of discrete molecular ultra small noble metal (Nb) nanoclusters (MUSNbNC's) of 1-6 atoms. The MUSNbNC's are capped with amine/DCA (dicarboxy acetone) group acting as a steric and kinetic hindrance for core growth suppressing the further autocatalysis and conversion of super critical nucleus or growth by ripening and formation of nanoparticles and thus having intense fluorescence.

First claim

I claim:

1. Capped spherical nano aggregates of size 10-22 urn comprising: molecular ultra small clusters of 1-6 atoms of noble metals selected from the group consisting of Au, Ag, Pt and Pd, wherein the clusters are stabilized by a surfactant and capping groups from a reducing agent and the clusters are the nano aggregates showing UV emission at 300-335 nm, no surface plasmon resonance, and visible 2 nd harmonic emission at 590-650 nm.

2. The capped spherical nano aggregates as claimed in claim 1 , wherein the reducing agent is a mild reducing agent selected from the group consisting of hydrazine hydrate or citric acid in water.

3. The capped spherical nano aggregates as claimed in claim 1 , wherein the surface of the nano aggregates is stabilized and capped by a capping group from amine or dicarboxyacetone (DCA) group of a mild reducing agent and a surfactant comprising an oxyethylene group.

4. The capped spherical nano aggregates as claimed in claim 1 , wherein the capping agent is mercapto undecanoic acid.

5. The capped spherical nano aggregates as claimed in claim 4 , wherein mercapto undecanoic acid capped nano aggregates are stable at pH 3-4 at a temperature ranging between 25-35° C.

6. The capped spherical nano aggregates as claimed in claim 4 , wherein mercapto undecanoic acid capped nano aggregates show 6 times more fluorescence intensity in comparison to amine/dicarboxyacetone capped nano aggregates.

7. The capped spherical nano aggregates as claimed in claim 1 , wherein nano aggregates show green emission when a blue or a green emission filter is used.

8. A process for the preparation of spherical nano aggregates as claimed in claim 1 , wherein the said process comprises the steps of:
a) preparing a oil phase by stirring cyclohexane and non ionic surfactant Triton 100-X (C14H22O(C2H4O)n (n=9-10) in ratio ranging between 52:22 wt, % to 54:24 wt % for 11-12 hrs at room temperature ranging between 25-35° C. with constant stirring and adding 7-11 wt. % n hexanol into it and stirring further for 10-12 hrs at room temperature ranging between 25-35° C.;
b) dividing oil phase as obtained in step (a) into two equal parts;
c) adding aqueous solution of freshly prepared 0.056 M metal salt in one part of oil phase as obtained in step (b) and stirring for 10-12 hrs;
d) adding aqueous solution of freshly prepared 0.32 M mild reducing agent in second part of oil phase as obtained in step (b) and stirring for 10-12 hrs;
e) combining solution as prepared in step (c) into the solution as obtained in step (d) dropwise and further stirring the solution for a period ranging between 10-20 days at, room temperature ranging between 25-35° C. to obtain solution containing nanoaggregates; and
centrifuging solution containing nanoaggregates as obtained in step (e) at 5000-6000 rpm for 10-20 min. at room temperature ranging between 25-35° C. and washing with water and ethyl alcohol 2-3 times to obtain spherical nano aggregates.

9. The process as claimed in claim 8 , wherein mild reducing agent used in step (d) is selected from the group consisting of hydrazine hydrate or citric acid in water.

10. The process as claimed in claim 8 , wherein metal salt used in step (c) is auric Chloride, silver nitrate and platinum chloride.

Assignees

• Council Scient Ind Res

Inventors

• Harle Arti

Classifications

• B22F1/054

  Nanosized particles · CPC title

• B22F1/148

  Agglomerating · CPC title

• B22F1/0096

  Operations & Transport · mapped topic

• B22F1/0018 Primary

  Operations & Transport · mapped topic

• Y10S977/774

  Exhibiting three-dimensional carrier confinement, e.g. quantum dots · CPC title