# US 10,500,643 B2 · Direct formation of gold nanoparticles using ultrasound

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- Number: US 10,500,643 B2
- Document ID: US10500643B2
- Status: Granted
- Kind: B2
- Application number: 15/484,856
- Filed: 2017-04-11
- Published: 2017-10-12
- Granted: 2019-12-10
- Earliest claimed: 2016-04-12
- Assignees: National Technology & Engineering Solutions of Sandia, LLC
- Applicants: National Technology & Engineering Solutions of Sandia, LLC
- Inventors: Dale L. Huber; John Daniel Watt; Jonathan Chavez; Lauren Marie Ammerman
- Web page: https://patentgrep.com/patent/US10500643B2

## CPC

- B22F 9/04: starting from solid material, e.g. by crushing, grinding or milling ({C22C1/1084 takes precedence}; crushing, grinding or milling, in general, see the relevant subclasses, e.g. B02C)
- B22F 1/054: Nanosized particles
- B22F 1/0551: {Flake form nanoparticles}
- B22F 1/07: Metallic powder characterised by particles having a nanoscale microstructure (nanosized particles B22F1/054)
- B22F 2301/255: Silver or gold
- B22F 2999/00: Aspects linked to processes or compositions used in powder metallurgy
- B22F: WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER (making alloys by powder metallurgy C22C); APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER

## Abstract

The invention provides a green chemistry, aqueous method to synthesize gold nanoparticles directly from bulk gold sources. The method involves the ultrasonication of bulk gold in water in the presence of an alkythiol species and a quaternary ammonium surfactant. An organic bilayer forms on the surface of the gold which renders it susceptible to material ejection from the violent collapse of cavitation bubbles. This ejected material is stabilized in solution by the formation of an organic bilayer and can be easily separated. It can then be subjected to an aqueous digestive ripening step to give a gold nanoparticle ensemble with a well-defined plasmon resonance. This method is applicable to a number of different sources of bulk gold. The method can be applied to an environmentally important problem; the recovery of gold from electronic waste streams. For example, gold nanoparticles can be extracted directly from the surface of SIM cards, with no prior manipulation of the cards necessary.

## Claims

### Claim 1

A method of forming gold nanoparticles, comprising
providing a solid bulk gold in an aqueous solution comprising an alkylthiol and a surfactant that form an organic bilayer on a surface of the solid bulk gold; and
ultrasonicating the aqueous solution to form gold nanoparticles by implosive collapse of cavitation bubbles on the surface of the solid bulk gold.

### Claim 2 (depends on 1)

The method of claim 1, wherein the alkylthiol comprises dodecanethiol.

### Claim 3 (depends on 1)

The method of claim 1, wherein the surfactant comprises a quaternary ammonium salt.

### Claim 4 (depends on 3)

The method of claim 3, wherein the quaternary ammonium salt comprises didodecyldimethylammonium bromide.

### Claim 5 (depends on 3)

The method of claim 3, wherein the quaternary ammonium salt comprises cetyltrimethylammonium bromide or cetyltrimethylammonium chloride.

### Claim 6 (depends on 1)

The method of claim 1, wherein the ultrasonicating uses an ultrasound frequency between 20 kHz and 10 MHz.

### Claim 7 (depends on 1)

The method of claim 1, wherein the gold nanoparticles are less than 100 nm in size.

### Claim 8 (depends on 1)

The method of claim 1, further comprising digestive ripening of the gold nanoparticles.

### Claim 9 (depends on 8)

The method of claim 8, wherein the digestive ripening comprises refluxing in water in the presence of a ripening agent.

### Claim 10 (depends on 9)

The method of claim 9, wherein the ripening agent comprises poly(ethylene glycol) methyl ether thiol.

### Claim 11 (depends on 1)

The method of claim 1, wherein the solid bulk gold comprises a metallic gold powder.

### Claim 12 (depends on 11)

The method of claim 11, wherein the size of the metallic gold powder is less than 20 μm.

### Claim 13 (depends on 1)

The method of claim 1, wherein the solid bulk gold comprises a gold contact.

### Claim 14 (depends on 13)

The method of claim 13, wherein the gold contact comprises an electronic waste.

### Claim 15 (depends on 14)

The method of claim 14, wherein the electronic waste comprises a cellular subscriber identity module card.