Methods for preparing aqueous suspension of precious metal nanoparticles

Patent metadata

Field	Value
Publication number	US-10184025-B2
Application number	US-201414161773-A
Country	US
Kind code	B2
Filing date	Jan 23, 2014
Priority date	Jan 25, 2013
Publication date	Jan 22, 2019
Grant date	Jan 22, 2019

Abstract

The present disclosure is directed to methods of preparing stable suspensions of precious metal nanoparticles and methods for attaching bio-molecules to the nanoparticles. The formation of nanoparticles can be accomplished by either chemical synthesis or pulsed laser ablation in a liquid. The present disclosure reveals the importance of controlling the conductivity of the dispersion medium during pulsed laser ablation in a liquid to control the particle size of the nanoparticles. The present disclosure also reveals the importance of adjusting and maintaining the conductivity in a range of 25 μS/cm or less during storage of the nanoparticles and just prior to performing bioconjugation reactions. The control of conductivity is an important process for maintaining the nanoparticles as a stable non-aggregated colloidal suspension in a dispersion medium.

First claim

We claim:

1. A colloidal suspension comprising;
precious metal nanoparticles selected from the group consisting of gold, silver, copper, platinum, palladium, rhodium, ruthenium, iridium, osmium, and an alloy including at least one of said precious metals, said nanoparticles having a size distribution including a single peak and a size range of from about 1 to 100 nm, said nanoparticles being at a molar particle concentration of more than 0.01 nM in a suspension liquid, said suspension liquid being free from any nanoparticle dispersants, stabilizing agents, or surfactants that cause steric repulsion between said nanoparticles other than at least one added predetermined electrolyte, said added predetermined electrolyte consisting essentially of at least one anion or cation formed with an element selected from the group consisting of the alkali metal elements from Group 1 of the Periodic Table, the alkaline earth metal elements from Group 2 of the Periodic Table, and the halide elements from Group 17 of the Periodic Table, wherein an electrical conductivity of said suspension liquid is stabilized by the addition of said predetermined electrolyte, and
wherein the amount of the predetermined electrolyte added is selected to cause the colloidal suspension to have an initial electrical conductivity of from greater than 2.0 to 25 μS/cm and wherein an increase of said electrical conductivity of said colloidal suspension over time is less than 1.5 μS/cm per week.

2. The colloidal suspension of claim 1 wherein the initial electrical conductivity of the colloidal suspension is greater than 2.0 μS/cm and less than 15 μS/cm.

3. The colloidal suspension of claim 1 wherein the colloidal suspension is enclosed in a storage container, wherein a material of the storage container in contact with the colloidal suspension is a polymer or a plastic selected from the group consisting of polycarbonate, polyethylene, polyethylene terephthalate, and polyethylene terephthalate glycol-modified.

4. The colloidal suspension of claim 1 wherein the precious metal nanoparticles have a particle diameter in a range of about 10 to 100 nm.

5. The colloidal suspension of claim 1 wherein the electrolyte includes water and at least one salt.

6. The colloidal suspension of claim 1 , wherein the concentration of the precious metal nanoparticles is more than 0.1 nM.

7. The colloidal suspension of claim 1 , wherein the precious metal is gold, silver, copper, or an alloy including at least one of said precious metals.

8. The colloidal suspension of claim 1 made by a Pulsed Laser Ablation in Liquid (PLAL) method in which high repetition rate laser pulses generate Precious Metal Nano-Particles (PMNPs) in a liquid.

9. The colloidal suspension according to claim 1 , wherein the colloidal suspension is stable, meaning the absorbance at 520 nm is +/−15% of the value of the colloidal suspension as initially prepared.

10. A method of bio-conjugation of the colloidal suspension according to claim 1 , said method comprising:
receiving a colloidal suspension of precious metal nanoparticles in a dispersion medium according to claim 1 ;
monitoring an electric conductivity of said colloidal suspension with one or more conductivity monitoring devices and, if required, adjusting the electric conductivity of the dispersion medium to be 25 μS/cm or less; and
performing a bio-conjugation of said nanoparticles with bio-molecules by mixing said colloidal suspension with said bio-molecules so that at least a portion of said bio-molecules attach to said precious metal nanoparticles.

11. The method of claim 10 , wherein said colloidal suspension comprises precious metal nanoparticles at a concentration of more than 0.01 nM; and a dispersion medium comprising water and electrolyte.

12. The method of claim 10 , wherein said colloidal suspension is made by a Pulsed Laser Ablation in Liquid (PLAL) process.

13. A method of making a colloidal suspension according to claim 1 , said method for bio-conjugation, the method comprising the steps of:
providing a target material comprising a precious metal and a liquid containing deionized water and electrolyte as a dispersion medium in an ablation container;
monitoring an electric conductivity of the dispersion medium with one or more conductivity monitoring devices and, if required, adjusting the electric conductivity of the dispersion medium by a conductivity adjustment system to be 25 μS/cm or less;
generating precious metal nanoparticles by delivering laser pulses to the target material there by ablating the target material and forming a colloidal suspension of the precious metal nanoparticles and adjusting the colloidal suspension to contain at least 0.01 nM of the precious metal nanoparticles.

14. The method of claim 10 , wherein said colloidal suspension is made with a chemical synthesis method.

15. The method of claim 10 , further comprising: increasing the conductivity in the colloidal suspension to higher than 25 μS/cm subsequent to said monitoring and adjusting, or during said step of performing bioconjugation.

16. The method of claim 10 , wherein said adjusting is carried out with a conductivity adjustment system.

17. The method of claim 10 , wherein said bio-conjugation includes surface functionalization of said nanoparticles with bio-molecules, including at least one functional group selected from the group consisting of thiol, disulfide, phosphine, amine, azide, methyl, and carboxyl.

18. The method of claim 17 , wherein the biomolecule comprises an organic chain molecule.

19. The method of claim 17 , wherein the bio-molecules have a molecular weight larger than 200 g/mol.

20. The method of claim 17 , wherein the bio-molecules have a molecular weight larger than 8500 g/mol.

21. The method of claim 10 , wherein the precious metal nanoparticles have an average particle diameter in a range of about 10 to 100 nm.

22. The method of claim 10 , wherein said electrical conductivity is determined at least at or near a time when said bio-conjugation is initiated.

23. A method of making a colloidal solution according to claim 1 , said method comprising the steps of:
providing a liquid having an electrical conductivity;
adjusting the electrical conductivity of the liquid to be less than 25 μS/cm providing nanoparticles in a container; and
combining the nanoparticles with the adjusted liquid in the container to form the colloidal solution that has a nanoparticle concentration of at least 0.01 nM.

24. A method of making a colloidal suspension according to claim 1 , said method comprising the steps of:
providing precious metal nanoparticles;
combining the precious metal nanoparticles with a liquid to form a colloidal suspension;
purifying the colloidal suspension to decrease a total ion concentration in the colloidal solution to be 25 μS/cm or less;
monitoring an electrical conductivity of the colloidal suspension; and

adjusting, if required, the electrical conductivity of the colloidal suspension to be less than 25 μS/cm.

25. The method of claim 12 , wherein said colloidal suspension is made with the PLAL method according to claim 13 .

Assignees

• Imra America Inc

Inventors

• Ichikawa Yuki
• Marcinkevicus Andrius
• Ito Masayuki
• Qian Wei

Classifications

• B01J13/0043 Primary

  containing elemental metal (for medical or diagnostical purposes A61K, G01N) · CPC title

• C08G65/328 Primary

  containing other elements · CPC title

• B82Y30/00

  Nanotechnology for materials or surface science, e.g. nanocomposites · CPC title