RO134945A2 - Cu-au bimetallic alloy nanoparticles and process for preparing the same - Google Patents

Abstract

The invention relates to Cu-Au bimetallic alloy nanoparticles and Au nanoparticles, prepared by radiochemical synthesis, having applications in optoelectronics, sensors, renewable energy and catalysts technologies, medical imaging, biocidal or antimicrobial agents and to a process for preparing them. According to the invention, the Cu-Au alloy nanoparticles and Au nanoparticles are prepared by irradiating with γ ionizing radiation an aqueous solution of metal precursors, such as the soluble salt of Cu and Au, respectively, which contains a pair of agents for coating and stabilizing the nanoparticles, consisting of a soluble polymer such as PVA, PVP or SDS and a compound of the form R(OH)x, where R = alkyl or iso-alkyl, substituted phenyl, and x = 1, 2, soluble or partially soluble in water, the latter acting as a free radical scavenger preventing the oxidation of formed nanoparticles, with absorption maxima between 528...550 nm and 532 nm, respectively, with average dimensions between 1...30 nm and 3.5 nm, respectively, and high stability over time. According to the invention, the process for preparing Cu-Au alloy nanoparticles and Au nanoparticles uses systems consisting of salt precursor of Cu and Au ions and Au ions, respectively, a pair of SDS, PVA or PVP coating and stabilizing agents and a compound of the form R(OH)x, soluble or partially soluble in water, consisting in preparing aqueous solutions of Cu and Au ions, and Au ions, respectively, by magnetic stirring at ambient temperature, introducing it in aqueous solution formed of a water soluble polymer, SDS 0.8%, PVP 3.5%, prepared by mixing at 80°C with magnetic stirrer and a compound of the form R(OH)x, in various concentrations, homogenizing it for one hour with magnetic stirrer at room temperature, adjusting the pH to 8…9 by adding NaOH solution, deaerating the solution for 30 min with N2 or Ar, followed by irradiation at a flow rate dose of 0.4 to 1.1 kGy/h at doses ranging between 0...60 kGy.

Description

BIMETALLIC ALLOY NANOPARTICLES HAVING A METHOD OF OBTAINING

The invention relates to Cu-Au bimetallic alloy nanoparticles and Au nanoparticles with controllable properties (size, narrow dimensional dispersion and high stability) with antimicrobial activity, as well as to the process for obtaining them.

Such materials feel used in various applications, such as optoelectronics, sensors, renewable energy technologies and catalysts, medical imaging, biocidal or antimicrobial agents, etc.

It is known that an important aspect in establishing the properties of these nanomaterials is the control of particle size, particle distribution and shape. Consequently, there is a growing interest in the development of methods that allow a controlled synthesis of nanoparticles.

Metal nanoparticles (Np) are characterized by different chemical composition, shape, size and monodispersion. To modify these characteristics, three types of synthetic methods are known: chemical, physical and biological [1],

Metal nanoparticles can be obtained in gas, solid and liquid phase [2], in liquid phase, nanoparticles are chemically synthesized in colloidal solutions containing precursors, reducing agent, coating agent and solvent [3],

Colloids are suspensions of a solid or liquid phase in a second liquid phase. Most methods of obtaining metal colloids are based on the reduction of a metal ion precursor, in solution in the presence of a stabilizing agent. All these synthesis methods have the disadvantage that they involve the use of toxic and / or high biological risk reducing agents for the environment, long synthesis time, staged process, high temperatures [4-6], Another disadvantage of classical syntheses is given the difficulty of obtaining metallic nanoparticles with controllable, reproducible properties (size, narrow dispersion and high stability), as well as obtaining small quantities of nanoparticles, which leads to high costs of the synthesis process [7].

The literature cites numerous examples of making Cu-based nanometric structures with other metals, especially core-shell structures [4,5], obtained by chemical synthesis. The main disadvantage of these synthesis methods is the use of chemical reducing agents (hydrazine, sodium borohydride) known to be toxic [5-6] or the use of high temperatures [4],

Similar disadvantages have the process proposed in the paper [6], in which Au-Cu bimetallic alloy nanospheres were obtained by chemical synthesis and the use of sodium borohydride as reducing agent and PVP as nanoparticle stabilizing agent, the synthesis achieving if at high temperatures.

The principle of the proposed synthesis method is based on the radiolysis of aqueous solutions, the ionizing radiation transferring to the irradiated material a very large amount of energy, a few orders of magnitude higher than the average energy required to break any chemical bond, thus transferring non-selective [8],

The interaction of ionizing radiation energy with the aqueous solution of Cu and Au ions induces ionization and excitation of the solvent and leads to the formation of radiolithic species, especially hydrated electron and H * atoms.

Irradiance

H ₂ O - e; _q .H ₃ O \ H \ H ₂ .OH \ H _: (1)

These species are strong reducing agents with redox potentials Eo (HiO / eaq ') = 2.87 Vnhe and Eo (H ⁺ / H *) = -2.3 Vnhe [9] and can reduce Cu and Au ions in solution to zero-valent Cu and Au particles.

i / 7

Hydroxyl (OH *) radicals, induced by water radiolysis, with a redox potential Eo (OI-F / I-bO) = +2.8 Vnhe [9] can oxidize ions or atoms at high oxidation states. To avoid this, it is necessary to introduce OH * radical scavengers, such as primary or secondary alcohols, into the precursor solutions.

The object of the invention is to eliminate the above-mentioned disadvantages, namely to obtain Cu-Au bimetallic alloy nanoparticles, in a single step, in aqueous solutions, at ambient temperature and pressure, small dimensions, narrow dimensional distribution and high stability in time. Another object of the present invention is to eliminate the above-mentioned disadvantages of physical and chemical methods by a process that ensures reasonable consumption of raw materials, low losses, yield and high selectivity (low level of waste and unprocessed raw materials). ), under the conditions of the use of non-toxic or environmentally harmful reagents.

The technical problem solved by the invention is to obtain small-bimetallic Cu-Au alloy nanoparticles with narrow dimensional distribution, high solution stability and high biocidal activity, in terms of efficient consumption of raw materials, and yield and high selectivity in the transformation of the ionic precursor, using the energy of ionizing radiation (γ) to transform the ionic precursors in aqueous solution.

Cu-Au bimetallic alloy nanoparticles are obtained according to the invention by γ-radiation irradiation of an aqueous solution of metal precursors (soluble copper and Au salt, respectively), which contains a pair of nanoparticle coating and stabilizing agents consisting of a polymer soluble (such as PVA, PVP, SDS) and a compound of the form R-OH _X (where R = alkyl or iso-alkyl, substituted phenyl and x = 1,2) soluble or partially soluble in water, the latter acting as a free radical scavenger preventing the oxidation of nanoparticles formed.

The invention has the following advantages:

- the synthesis of nanoparticles takes place in aqueous solution, which allows precise control of the parameters at any point of the reactor (concentration, temperature, dose), ensuring the reproducibility of the process;

- the synthesis does not require the use of toxic or high biological risk chemical reducing agents, the main reducing agent in the absence of oxygen being the hydrated electron which has a very high reduction potential;

- Np of bimetallic Cu-Au and Au alloy obtained has a uniform dispersion and high stability over time (of the order of months);

- the proposed synthesis process allows to obtain at a low price large quantities of Np of bimetallic Cu-Au or Au alloy with controllable size and structure, with high reproducibility, and can be applied on an industrial scale;

- the process for obtaining Cu-Au and Au bimetallic alloy nanoparticles is simple and fast and is performed at ambient pressure and temperature;

- The average size of the nanoparticles and the dimensional distribution depend critically on a small number of parameters that can be easily controlled, namely the irradiation dose and the concentrations of the stabilizing agent and the Cu and Au ions and the ratio of these concentrations.

The following are 4 embodiments of the invention, in connection with Figures 1-7, which represent:

7¼

FIG. 1 - Technological scheme of the process for obtaining Cu-Au bimetallic alloy nanoparticles and Au nanoparticles

FIG. 2 - UV-Vis spectra of the Cu / Au / SDS / EG colloidal system (Cu / Au molar ratio of 2/1)

FIG. 3 - STEM micrographs made on the colloidal system Cu / Au / SDS / EG

FIG. 4 - Stability over time of the colloidal bimetallic alloy Cu-Au system (Cu / Au molar ratio of 2/1);

FIG. 5 - UV-Vis spectra of the colloidal Cu / Au / SDS / EG system at different concentrations of Cu ²⁺ ;

FIG. 6 - Stability over time of the colloidal system of bimetallic alloy Cu-Au (depending on the concentration of Cu ²⁺ (1 - immediately after irradiation, 2-2 months after irradiation);

FIG. 7 - UV-Vis spectra of the colloidal Cu / Au / PVP / Aip system (Cu / Au molar ratio of 2/1)

Example 1

For the purpose of radiochemical synthesis according to the invention, the following sequence of operations is used (Fig. 1):

- preparation of precursor solutions (solution A and solution B) in an aqueous solution of stabilizing agent of a certain concentration (SDS, PVP, PVA), which involves dosing the precursors; the dissolution of the soluble polymer is carried out at 80 ° C with a magnetic stirrer until the solution becomes clear; the dissolution of the precursors is performed with a magnetic stirrer at ambient temperature;

- preparation of the reaction mixture consisting of mixing solutions A and B with a compound R (OH) x, which involves the dosing of the components in correlation with the amount of precursors; the dissolution of the compound R (OH) _X is done at ambient temperature, after cooling the polymer solution, with a magnetic stirrer; pH control and correction takes place (8-9) and deaeration of the system (removal of oxygen by bubbling N2 or Ar for 30 minutes); mixing is performed at room temperature with a magnetic stirrer for 1 hour;

- exposure to irradiation (Flow rate: 0.7 kGy / h) of the reaction mixture in a hermetically sealed glass container wrapped in aluminum foil; involves the determination and control of the irradiation dose (calibration of the exposure dose can be done periodically with a Fricke-type dosimeter, RTL, ECB, alanine, etc.);

- dimensional characterization and biocidal activity of the product obtained. It is performed by specific, known measurements, such as UV-vis spectroscopy, STEM, DLS, as well as by antimicrobial activity tests.

Example 2

Using the procedure described in Example 1, prepare:

- 100 ml of solution (A) by dissolving an amount of copper salt corresponding to a concentration of 2 · 10 ' ³ mol / l Cu ²⁺ in a solution of 0,8% SDS in deionized water;

- 100 ml of solution (B) by dissolving an amount of Au ³⁺ salt (chloroauric acid HțAuCU]) corresponding to a concentration of 1 -IO ' ³ mol / 1 Au ³⁺ in a solution of 0,8% SDS in water deionized;

RO 134945 A2 ^>

- the reaction mixture was obtained using 15 ml of solution A, 15 ml of solution B and 4 ml of ethylene glycol (EG); The pH was adjusted to 8.5 by adding NaOH solution (1%); deaeration was performed with Ar for 30 minutes at a flow rate of 50 ml / minute;

- exposure to irradiation was made at a total dose of 30 kGy.

After irradiation, colloidal systems of chrome-colored bimetallic Cu-Au nanoparticles were obtained. UV-Vis spectra showed maximum SPR absorption characteristic at approx. 530 nm (Fig. 2).

STEM analysis showed the formation of spherical nanaparticles (Fig. 3) with average dimensions below 20 nm, and the interplanetary distances determined at 2.20 Â, correspond to bimetallic alloys of CmAu type.

The stability of the bimetallic alloy nanoparticle system was tested by measuring the absorbance of the solutions over a period of 4 months (Fig. 4), the UV-Vis spectra remaining virtually unchanged during this period.

The obtained solutions showed antimicrobial activity in the test against Pseudomonas aeruginosa and Staphylococcus Aureus, with zones of inhibition between 4 and 15 mm, depending on the degree of dilution of the initial solution of Cu-Au alloy nanoparticles (Table 1) ·

Table 1 - Antimicrobial efficiency of the colloidal system of Cu-Au nanoparticles

System Solution concentration (%) Inhibition areas (mm) P. aeruginosa S. aureus Cu / Au (2: 1) / SDS / EG 100 14 15 50 8 7 25 4 4 12.5 - -

Example 3

Using the procedure described in Examples 1 and 2, prepare:

- 100 ml solution (A) with a concentration of 2 · 10 ' ³ mol / l Cu ²⁺ in a solution of 0,8% SDS in deionized water;

- 100 ml solution (B) with a concentration of 2 -IO ' ³ mol / l Au ³⁺ (chloroauric acid HțAuCU]) in a solution of 0,8% SDS in deionized water;

- the reaction mixture was obtained, using different volume ratios between solution A and solution B, to obtain different concentrations of Cu ions in the solution. 4 ml of ethylene glycol (EG) are added to this solution; The pH was adjusted to 8.5 by adding NaOH solution (1%); deaeration was performed with Ar for 30 minutes at a flow rate of 50 ml / minute;

- exposure to irradiation was made at a total dose of 50 kGy.

After irradiation, stable colloidal systems of Cu-Au bimetallic alloy nanoparticles were obtained, from cherry to light pink, depending on the initial concentration of Cu ²⁺ ions (the solution lightens in color with increasing concentration). The optical properties of this material are illustrated in Figs. 5 using UV-vis spectra showing that the maximum SPR (Surface Plasmon Resonance) is between 532 nm (0% Cu; a stable colloidal system of Gold nanoparticles is formed) and 550 nm (at 90% Cu) (Table 1). DLS measurements showed average nanoparticle sizes between 1.1-3.5 nm (Table 2) y

Table 2 - Characteristics of Cu-Au bimetallic alloy nanoparticles obtained according to Examples 1 and 2

Cu ²⁺ concentration (%) Maximum SPR (nm) Average diameter of DLS (nm) 0 532 3.5 ± 0.001 50 532 2.9 ± 0.017 77 536 2.1 ± 0.015 87 540 2.3 ± 0.947 90 550 l.l ± 0.032

The stability of the bimetallic alloy nanoparticle system was tested by measuring the absorbance of the solutions over a period of approx. 2 months (Fig. 6), the UV-Vis spectra remaining practically unchanged during this period.

Example 4

Using the procedure described in examples 1 and 2 prepare:

- 100 ml of solution (A) by dissolving an amount of copper salt corresponding to a concentration of 2 · 10 ' ³ mol / l Cu ²⁺ in a solution of 3.5% polyvinylpyrrolidone (PVP) in deionised water;

- 100 ml of solution (B) by dissolving an amount of Au ³⁺ salt (chloroauric acid H [AuCLi]) corresponding to a concentration of 1 -IO ' ³ mol / 1 Au ³⁺ in a solution of 3.5% polyvinylpyrrolidone (PVP ) in deionized water;

- the reaction mixture was obtained using 15 ml of solution A, 15 ml of solution B and 4 ml of isopropyl alcohol; The pH was adjusted to 8.5 by adding NaOH solution (1%); deaeration was performed with Ar for 30 minutes at a flow rate of 50 ml / minute;

- exposure to irradiation was made at a total dose of 30 kGy.

After irradiation, colloidal systems of cherry-colored bimetallic Cu-Au nanoparticles were obtained. UV-Vis spectra showed a maximum SPR absorption characteristic at approx. 530 nm (Fig. 7).

The stability of the Cu-Au / PVP / Aip bimetallic alloy nanoparticle system was tested by measuring the absorbance of the solutions over a period of 4 months (Fig. 4), the UVVis spectra remaining practically unchanged during this period.

The obtained solutions showed antimicrobial activity in the test against Pseudomonas aeruginosa and Staphylococcus Aureus, with zones of inhibition between 5 and 13 mm, depending on the degree of dilution of the initial solution of Cu-Au alloy nanoparticles (Table 3) ·

Table 3 - Antimicrobial efficiency of the colloidal system of Cu-Au nanoparticles

Molar ratio Solution concentration (%) Inhibition areas (mm) P. aeruginosa S. aureus Au / Cu (l: 2) / PVP / Aip 100 12 13 50 5 7 25 - - 12.5 - -

BIBLIOGRAPHY

[1] Yashiro K. Microbial Synthesis of Noble Metal Nanoparticles Using Metal Reducing Bacteria. Journal of the Society of Powder Technology. 43 (7), 515-521 (2006)

[2] Madou MJ. Fundamentals ofMicrofabrication and Nanotechnology: From MEMS to BioMEMS and Bio-Nems: manufacturing techniques and applications. Boca Raton, FL: CRC Presslnc (2011)

[3] Abedini A, Daud A.R., Hamid M.A.A., Othman N. K., Saion E. A review on radiationiduced nucleation and growth of colloidal metallic nanoparticles. Nanoscale Research Letters, 8, 474-484 (2013)

[4] Lauterbach JA, Hattrick-Simpers JR, Wen C. One-step synthesis of monodisperse transition metal core-shell nanoparticles with solid solution shells. US patent 9205410B2 (2013)

[5] Preparation method of nuclear shell structured nano-gold copper powder. China patent 1299865C (2005)

[6] Preparation method for gold-copper bimetal nanospheres. China patent 102728847A (2011)

[7] A. A Alkhedhairy, J. Mussarat. Methods for producing silver nanoparticles. US 2011 / 0274736,10 Nov. 2011

[8] Be M.B. Chemical dosimetry of ionizing radiation. Ed. Academiei, Bucharest (1973)

[9] Rojas J., Castano C. Production of palladium nanoparticles supported on multrwalled carbon nanotubes by gamma irradiation. Radiated. Phys. Chem. 81, 16—21 (2012)

Claims (4)

1. Narrow-dimensional bimetallic Cu-Au alloy nanoparticles, characterized in that they are obtained by exposure to irradiation of systems consisting of the salt-precursor of Cu and Au ions and a pair of coating and stabilizing agents on water-soluble polymer base (SDS, PVA, PVP) and a compound of the form R (OH) x (where R = alkyl or iso-alkyl, substituted phenyl and x = 1, 2) soluble or partially soluble in water, the latter acting as a free radical scavenger preventing the oxidation of formed nanoparticles, with absorption maxima between 528-550 nm, with average dimensions between 1-30 nm, with high stability over time, with narrow dispersion and high antimicrobial activity {Staphylococcus Sp., Pseudomonas sp.}, 2. Narrow-dimensional Au nanoparticles, characterized in that they are obtained by exposure to irradiation of a system consisting of salt-precursor of Au ions and a pair of water-soluble polymer-based coating and stabilizing agents ( SDS, PVP, PVA) and a compound of the form R (OH) _X (where R = alkyl or iso-alkyl, substituted phenyl and x = 1, 2) soluble or partially soluble in water, the latter acting as a catcher of free radicals preventing the oxidation of formed nanoparticles, with a maximum absorption at 532 nm nm, with average dimensions of 3.5 nm, with high stability over time, with narrow dispersion Process for the radiochemical synthesis of Cu-Au bimetallic alloy nanoparticles according to Claim 1, characterized in that systems consisting of Cu and Au ion precursor salt and a pair of coating and stabilizing agents are used. based on water-soluble polymer (SDS, PVA, PVP) and a compound of the form R (OH) x (where R = alkyl or iso-alkyl, substituted phenyl and x = 1, 2) soluble or partially soluble in water , the latter acting as a free radical scavenger preventing the oxidation of the nanoparticles formed and consists in obtaining aqueous solutions of Cu and Au ions (concentrations between IO ' ^{4 5} and IO' ³ mol / L) by magnetic stirring at ambient temperature , its introduction into an aqueous solution consisting of a water-soluble polymer (SDS 0.8%, PVP 3.5%) obtained by mixing at 80 ° C with a magnetic stirrer and a compound of the form R (OH) x ( where R = alkyl or iso-alkyl, substituted phenyl and x = 1, 2) soluble or partially soluble in water , in different concentrations, homogenization of the resulting solution with magnetic stirrer at room temperature, for 1 hour, adjusting the pH to 8-9 by adding NaOH solution, deaeration of the solution with N2 or Ar to remove O2, for 30 minutes, followed irradiation at a flow rate of 0.4-1.1 kGy / h, at full doses of 0-60 kGy. Process for obtaining Au nanoparticles by radiochemical synthesis according to Claim 2, characterized in that systems consisting of Au ion precursor salt and a pair of water-soluble polymer-based coating and stabilizing agents are used (SDS, PVA, PVP) and a compound of the form R (OH) x (where R = alkyl or iso-alkyl, substituted phenyl and x = 1,2) soluble or partially soluble in water, the latter acting as free radical scavenger preventing the oxidation of nanoparticles formed and consists in obtaining aqueous solutions of Au ions by magnetic stirring at ambient temperature, introducing it into an aqueous solution consisting of a water-soluble polymer (SDS 0.8%, PVP 3, 5%) obtained by mixing at 80 ° C with a magnetic stirrer and a compound of the form R (OH) x (where R = alkyl or iso-alkyl, substituted phenyl and x = 1, 2) soluble or partially soluble in water, in different concentrations, homogenization of the resulting solution with tempered magnetic stirrer room for 1 hour, adjusting the pH to 8-9 by adding NaOH solution, deaerating the solution with N2 or Ar to remove O2 for 30 minutes, followed by irradiation at a flow rate of 0,4- 1.1 kGy / h, at full doses between 0-60 kGy.