The disclosure of the present patent application relates to copper nanoparticles, and particularly to a method for making carbon coated copper nanoparticles by a single step method.
In recent years, there has been considerable interest in replacing noble metal nanoparticles (such as gold nanoparticles) in electrical, optical, and catalytic applications with nanoparticles made from less expensive materials, such as copper nanoparticles. A problem with this approach is that bare copper nanoparticles will be oxidized in a matter of a few hours when exposed to air at room temperature. A solution to this problem is coating the copper nanoparticles with a layer or shell of carbon. The carbon shell shields the copper nanoparticle core from oxidation. However, current techniques for coating a copper nanoparticle core with a carbon shell use two-step or three-step methods, which are time-consuming, prone to error, and potentially difficult and expensive. Thus, a method for making carbon-coated copper nanoparticles solving the aforementioned problems is desired.
The method for making carbon-coated copper nanoparticles is a simple, one-step for coating copper nanoparticles with a carbon shell to prevent rapid oxidation of the carbon nanoparticle core. The method involves heating or autoclaving thin sheets of copper hydroxide nitrate (Cu2(OH)3NO3) under supercritical conditions (a temperature of 300° C. and a pressure of 120 bar) for two hours. The autoclaving may be performed in the presence of an inert gas, such as argon, which may be used to remove any remaining gases, and the pressure may be released in the presence of the inert gas so that the product may be collected in the presence of air.
These and other features of the present subject matter will become readily apparent upon further review of the following specification and drawings.
Similar reference characters denote corresponding features consistently throughout the attached drawings.
The method for making carbon-coated copper nanoparticles is a simple, one-step for coating copper nanoparticles with a carbon shell to prevent rapid oxidation of the carbon nanoparticle core. The method involves heating or autoclaving thin sheets of copper hydroxide nitrate (Cu2(OH)3NO3) under supercritical conditions (a temperature of 300° C. and a pressure of 120 bar) for two hours. The autoclaving may be performed in the presence of an inert gas, such as argon, which may be used to remove any remaining gases, and the pressure may be released in the presence of the inert gas so that the product may be collected in the presence of air.
The method will be better understood with reference to the following examples.
Copper monooxide (cupric oxide) and copper nitrate hydrate (Cu(NO3)2-xH2O) were supplied from Sigma-Aldrich Company. Copper hydroxyl nitrate (essentially two molecules of copper hydroxide nitrate) was prepared by adding copper (II) oxide (CuO) (0.2 mol; Mol. wt.=79.55 g/mol and purity ≥99.0%) to 200 ml of an aqueous solution of copper nitrate hydrate (1.25M; Mol. Wt. 187.56 g/mol and purity ≥99.999%) with vigorous stirring followed by heating the resultant mixture at 90° C. for 12 h with stirring. The reaction was performed under flow of argon gas. The resultant greenish-blue solid was washed with distilled water and then washed with alcohol many times. After filtration, the greenish-blue precipitate was dried at room temperature under vacuum for two days.
An appropriate amount of copper hydroxide nitrate (Cu2(OH)3NO3) (15.4 g, prepared as described in Example 1, above) was mixed with 150 ml of ethanol. Then, the mixture was placed in a pressurized vessel equipped with a temperature controller unit. The thermal process of the solid was achieved under super critical conditions (temperature=300° C. and pressure=120 bar) for 2 h. After the thermal process, the pressure was released in the presence of an inert gas (Argon), which was used during the autoclave fluxing process to remove any remaining gases. The product was collected in the presence of air.
The powder X-ray diffraction technique (XRD) has used to identify the crystalline structure of the raw material, as shown in
X-ray diffraction (XRD) pattern of the resultant particles from the thermal process of Example 1 showed disappearance of the peaks of copper hydroxide nitrate, as shown in
The obviously broadened diffraction peaks suggest that the resultant nanoparticles should have a very small crystallite size. An average crystallite size of about 50 nm for the Cu nanoparticles was calculated by using the Scherer's relation. Also, three weak peaks were observed and located at 2θ=35.5, 36.5 and 38.7°. These weak peaks can suggest the presence of traces of CuO and Cu2O.
The EDX analysis shown in
The TEM images in
In the Raman spectrum of the sample, the main band was observed at 1228 cm−1, as shown in
Thermal stability of the prepared C-coated Cu powders was investigated by thermogravimetric analyses and compared with the commercial copper nanoparticles. The analysis was conducted under nitrogen atmosphere with a heating rate of 10° C./min, and the results are shown in
To make a more detailed comparison on the thermal stability as a degree of Cu oxidation, the weight changes in TGA were normalized with each weight of powders at 540° C., where all the Cu in each sample was entirely oxidized (see
To determine the content of the carbon layers, the initial mass loss, which is assigned to the decomposition of carbon, can be calculated by comparison with that of the pure copper nanoparticles. Based on the TGA results of the pure copper nanoparticles, the difference between the mass losses of the prepared C-coated Cu and the pure Cu reveals the content of carbon layers in the prepared copper. It was 1.2 wt %.
Thus, the method for making carbon-coated copper nanoparticles described herein provides a simple, efficient, and economical one-step method for preparing carbon-coated copper nanoparticles.
It is to be understood that the method for making carbon-coated copper nanoparticles is not limited to the specific embodiments described above, but encompasses any and all embodiments within the scope of the generic language of the following claims enabled by the embodiments described herein, or otherwise shown in the drawings or described above in terms sufficient to enable one of ordinary skill in the art to make and use the claimed subject matter.
Number | Name | Date | Kind |
---|---|---|---|
20080220244 | Wai | Sep 2008 | A1 |
20100266846 | Kim | Oct 2010 | A1 |
20150202598 | Kallesoe | Jul 2015 | A1 |
20180297121 | Harold et al. | Oct 2018 | A1 |
Number | Date | Country |
---|---|---|
102806356 | Dec 2012 | CN |
107755691 | Mar 2018 | CN |
108906048 | Nov 2018 | CN |
111872407 | Nov 2020 | CN |
113235113 | Aug 2021 | CN |
114559033 | May 2022 | CN |
Entry |
---|
Li, J. et al., “Synthesis and surface plasmon resonance properties of carbon-coated Cu and Co nanoparticles”, Materials Research Bulletin, vol. 46, pp. 743-747, Available online Jan. 26, 2011. |
Sun et al., “A surfactant-free strategy for controllable growth of hierarchical copper oxide nanostructures”, CrystEngComm (2013), vol. 26 (Abstract only). |
Zeng et al., “Synthesis of copper nanoparticles using copper hydroxide”, 19th International onference on Electronic Packaging Technology (2018) (Abstract only). |
Li et al., “Carbon-coate copper nanoparticles: synthesis, characterization and optical properties”, New Journal of Chemistry (2009) (Abstract only). |