Parametric study of cost-effective synthesis of crystalline copper nanoparticles and their crystallographic characterization

Pure and high-crystalline copper nanoparticles were synthesized at room temperature by reduction of copper nitrate with hydrazine hydrate in cetyltrimethyl ammonium bromide (CTAB) solution without using any extra gases. A parametric study has been carried out in terms of hydrazine concentration, solution pH, and stirring. Pure copper nanoparticles without oxidation were obtained at 0.1–0.2 M N₂H₄ and pH = 10. The growth mechanism of various shaped copper nanoparticles is discussed based on structural analysis by transmission electron microscopy and selected area electron diffraction.     

Synthesis of copper nanoparticles from refractory sulfides using a semi-industrial mechanochemical approach

The large-scale mechanochemical reduction of binary sulfides chalcocite (Cu₂S) and covellite (CuS) by elemental iron was investigated in this work. The reduction of Cu₂S was almost complete after 360 min of milling, whereas in the case of CuS, a significant amount of non-reacted elemental iron could still be identified after 480 min. Upon application of more effective laboratory-scale planetary ball milling, it was possible to reach almost complete reduction of CuS. Longer milling leads to the formation of ternary sulfides and oxidation product, namely cuprospinel CuFe₂O₄. The rate constant calculated from the magnetometry measurements using a diffusion model for Cu₂S and CuS reduction by iron in a large-scale mill is 0.056 min^−0.5 and 0.037 min^−0.5, respectively, whereas for the CuS reduction in a laboratory-scale mill, it is 0.1477 min⁻¹. The nanocrystalline character of the samples was confirmed by TEM and XRD, as the produced Cu exhibited sizes up to 16 nm in all cases. The process can be easily scaled up and thus copper can be obtained much easier from refractory minerals than in traditional metallurgical approaches.     

Selective synthesis of copper nanoplates and nanowires via a surfactant-assisted hydrothermal process

A facile solution-phase process has been demonstrated for the selective preparation of single-crystalline Cu nanoplates and nanowires by reducing Cu⁺ with ascorbic acid (VC) in the presence of cetyltrimethylammonium bromide (CTAB) or cetyltrimethylammonium chloride (CTAC). To study the formation process of nanoplates and nanowires, samples obtained at various stages of the growth process were studied by TEM and XRD. The possible mechanism was discussed to elucidate the formation of different morphologies of Cu nanostructures. UV–vis spectra of the Cu nanoplates and nanowires were recorded to investigate their optical properties, which indicated that the as-prepared Cu nanostructures exhibited morphology-dependent optical property.     

Simple new synthesis of copper nanoparticles in water/acetonitrile mixed solvent and their characterization

Copper nanoparticles were successfully synthesized by the borohydride reduction of copper nitrate salt in water/CH₃CN mixed solvent under inert argon-purged conditions. Cu nanoparticles were synthesized in large-scale production for the first time by introducing CH₃CN into water and preventing oxidation during the preparation of nanoparticles. Nanoparticles were characterized by using UV-visible absorption spectroscopy, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) techniques. High resolution TEM pictures showed the formation of homogeneous cubic-structured copper nanoparticles with sizes less than 100 nm. This new kind of synthesis method shows the excellent stability compared with that of citrate-protected copper nanoparticles, which may provide an efficient way to improve the fine tuning of the structure and size of copper nanoparticles.     

Consolidation thermodynamics of the nanoparticles in a solid-mobile phase two-phase system

Thermodynamic functions have been derived that describe the processes of the nanoparticle consolidation in a solid-mobile phase two-phase dispersed system and the deconsolidation of a polycrystalline body that is accompanied by the spontaneous formation of a nanodispersed system. An expression for the shrinkage pressure has been deduced, which allows one to calculate stresses occurring in the bulk of heterophase composite materials in the course of the nanoparticle consolidation.     

Inkjet printing using copper nanoparticles synthesized by electrolysis

A modified electrolysis method was employed to synthesize copper nanoparticles for mass production. Processing parameters including electrolyte temperature, pH and reduction agents were controlled in order to synthesize the particles continuously and directly from copper plates. As a result, well-dispersed copper nanoparticles with an average diameter of 15 nm were obtained and the oxidation of these particles was prevented by controlling the parameters. Using an amphiphilic surfactant, a water-based copper nano-colloid was prepared and printed onto a polyimide substrate using a conventional ink-jet printer. Copper patterns sintered at 230 °C showed a resistivity of 5.4 μΩ-cm (bulk resistivity; 1.67 μΩ-cm).     

Phospholipid-assisted synthesis of size-controlled gold nanoparticles

Morphology and size control of gold nanoparticles (AuNPs) by phospholipids (PLs) has been reported. It was found that gold entities could form nanostructures with different sizes controlled by PLs in an aqueous solution. During the preparation of 1.5 nm gold seeds, AuNPs were obtained from the reduction of gold complex by sodium borohydride and capped by citrate for stabilization. With the different ratios between seed solution and growth solution, which was composed by gold complex and PLs, gold seeds grew into larger nanoparticles step by step until enough large size up to 30 nm. The main discovery of this work is that common biomolecules, such as PLs can be used to control nanoparticle size. This conclusion has been confirmed by transmission electron micrographs, particle size analysis, and UV-vis spectra.     

Controllable hydrothermal synthesis of Cu2S nanowires on the copper substrate

In this paper, a simple solution-based method has been applied to fabricate metal chalcogenide nanostructures. Abundant Cu₂S nanowires on Cu substrates are successfully prepared through the in-situ hydrothermal reaction between sulfur powder and Cu foil. It is observed that the addition of hydrazine and cetyltrimethylammonium bromide plays an important role in the growth of Cu₂S nanowires. A rolling-up mechanism of metal chalcogenide film is used to illustrate the growth of these nanostructures. UV-vis spectrum of Cu₂S nanowires reveals obvious absorption below the wavelength of 900 nm. The calculated band gap of Cu₂S nanowires (1.5 eV) shows obvious blue shift because of the quantum size effect.     

Controllable synthesis of submicrometer-sized copper crystallites with different morphologies

Pure submicrometer-sized copper crystallites with hexagonal, star-shaped and snowflake-shaped structures have been successfully synthesized via solvothermal treatment of CuSO₄ ? 5H₂O in ethylenediamine (EDA) at 190 °C for 12-18 h. X-ray powder diffraction (XRD) and transmission electron microscopy (TEM) were employed to characterize the crystalline structure, size and morphology of the as-synthesized copper crystallites. It is found that reaction temperature, reaction time and reaction solvents all play important roles in the composition and morphology of the products. The possible reaction mechanism was discussed by Fourier transform infrared spectroscopy (FT-IR). Here, ethylenediamine can be used as a reducing agent as well as a coordination ligand.     

Low-temperature synthesis of copper sulfide nano-crystals of novel morphologies by hydrothermal process

Different morphological images of copper sulfide nano-crystals, e.g., butterfly-like, twin-hexagonal star-like, triangle polyhedral-like and nut-like, have been successfully synthesized by different hydrothermal processes without surfactant assistance. The reactions were carried through Cu(ac)₂ complexed by citric acid with thiourea for 24 h at an appropriate temperature. The experimental results revealed that temperature, molar ratio, concentration of the precursor and solvent had effects on the morphology and composition of copper sulfide nano-crystals.     

Colloidal synthesis of Cu2SnSe3 nanocrystals

While Cu₂SnSe₃ material has various potential applications including acousto-optics and photovoltaics, preparation methods of this material only in a bulk form or a thin film have been reported so far. In this work, for the first time, we demonstrate that highly crystalline Cu₂SnSe₃ nanoparticles can be prepared via colloidal synthesis. The Cu₂SnSe₃ nanocrystals have a cubic crystal structure with a lattice parameter of 5.68 Å, an average diameter of 18 nm, and an atomic ratio of approximately 2:1:3. The nanocrystals can be stably suspended in solution for several months. The suspended nanocrystalline form of Cu₂SnSe₃ could potentially be useful for printable acousto-optic and photovoltaic applications.     

Solvothermal synthesis of copper sulfide semiconductor micro/nanostructures

Covellite copper sulfide (CuS) micro/nanometer crystals in the shape of hierarchical doughnut-shaped, superstructured spheric-shaped and flowerlike architectures congregated from those nanoplates with the thickness of 20-100 nm have been prepared by a solvothermal method. The as-obtained CuS products were characterized by means of scanning electron microscopy (SEM), X-ray diffractometry (XRD) and energy-dispersive X-ray spectroscopy (EDS). A systematic investigation has been carried out to understand the factors influencing the evolution of CuS particle morphology which found to be predominant by solvent, surfactant, sulfur resource and copper salt. The possible formation mechanism for the nanostructure formation was also discussed. These CuS products show potential applications in solar cell, photothermal conversion and chemical sensor.     

Hydrothermal synthesis of HgTe rod-shaped nanocrystals

HgTe nanorods composed of crystalline particles with the diameter of 100-300 nm and length of up to 2-3 μm have been prepared by a hydrothermal method, and characterized by means of X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transition electron microscopy (TEM) and energy-dispersive X-ray analysis (EDX). It was found that ammonia played a key role in the formation of HgTe nanorods.     

Synthesis and growth features of copper hydroxide iodide nanoneedles

Single-crystalline Cu₂(OH)₃I nanoneedles were synthesized by the reaction between Cu(CH₃COO)₂ and KI in aqueous solutions with or without poly(ethylene glycol) (PEG) in situ, and techniques of XRD, EDX, SEM and TEM were used to characterize their crystal structure, chemical composition and growth feature. The as-prepared nanoneedles had a high purity in composition and belonged to the botallackite-type Cu₂(OH)₃I. Nanoneedles, together with botallackite-type Cu₂(OH)₃I flakes, were produced in the absence of PEG, and their growth features were consistent with the theoretical predictions; however, the addition of PEG to the solution led to the exclusive formation of nanoneedles, in which the adsorption of PEG on the related crystal surfaces controlled a crystal growth different from theoretical expectations.     

Microwave-hydrothermal synthesis of perovskite bismuth ferrite nanoparticles

Hydrothermal microwave method (HTMW) was used to synthesize crystalline bismuth ferrite (BiFeO₃) nanoparticles (BFO) in the temperature of 180 °C with times ranging from 5 min to 1 h. BFO nanoparticles were characterized by means of X-ray analyses, FT-IR, Raman spectroscopy, TG-DTA and FE-SEM. X-ray diffraction results indicated that longer soaking time was benefit to refraining the formation of any impurity phases and growing BFO crystallites into almost single-phase perovskites. Typical FT-IR spectra for BFO nanoparticles presented well defined bands, indicating a substantial short-range order in the system. TG-DTA analyses confirmed the presence of lattice OH⁻ groups, commonly found in materials obtained by HTMW process. Compared with the conventional solid-state reaction process, submicron BFO crystallites with better homogeneity could be produced at the temperature as low as 180 °C. These results show that the HTMW synthesis route is rapid, cost effective, and could be used as an alternative to obtain BFO nanoparticles in the temperature of 180 °C for 1 h.     

Hot-wire synthesis of Si nanoparticles

The viability of producing silicon nanoparticles using the HWCVD process is investigated. A system is assembled and particles are produced from silane at pressures between 0.2 and 48 mbar, with hydrogen dilutions of 0-80%, at a total flow rate of 50 sccm and with a tungsten filament maintained at 1650 °C. The as-prepared powder varies in colour from yellowish to dark brown and is deposited on all surfaces inside the reaction chamber. The material is a highly porous agglomeration of nanoparticles of primary size in the order of 40 nm, with a narrow size distribution. The nanoparticles produced are mostly amorphous, hydrogenated and have a partially oxidised surface.     

Enhancement of photoconduction in a conjugated polymer through doping with copper nanoparticles

We investigated the effect of doping with copper nanoparticles (Cu NPs) on photoconductivity of poly(3-hexylthiophene) P3HT films. ∼20 nm Cu NPs were fabricated in a simple one step reduction process in hydrophobic environment. Structure, morphology and optical properties of the Cu nanoclusters were characterized. Films of P3HT containing Cu NPs were fabricated and their optical and electrical properties investigated. The results indicate that the change of the efficiency of the light absorption brought about by the effect of plasmonic resonances is minor, but there is a substantial influence of the metal nanoparticles on the efficiency of the photogeneration of charges in P3HT.     

Biomimetic synthesis of platinum nanoparticles utilizing a terrestrial weed Antigonon leptopus

In this work, we report for the first time a new bio-inspired method for platinum nanoparticle (PtNP) synthesis utilizing a highly invasive terrestrial weed coral vine (Antigonon leptopus) as the main bioagent. Extracts of all three basic components of the plant – leaves, stem and root – were explored and were found to be suitable in effecting the PtNP synthesis. The electron micrographs of the synthesized PtNPs revealed the presence of particles of monodispersed spherical and polydispersed shapes in sizes ranging from 5 to 190?nm. The presence of Pt atoms was confirmed from the energy dispersive X-ray (EDAX) and X-ray diffraction (XRD) studies. The FTIR spectral study indicated that the polysaccharides and proteins in the plant extract could have been responsible for the reduction of Pt ions to PtNPs and the latter’s stabilization.     

Sonochemical synthesis of gold nanoparticles on chitosan

Au nanoparticles deposited on chitosan were readily prepared from aqueous solution of NaAuCl₄ containing chitosan powder by the reaction with sonochemically formed reducing species. The average size of the formed Au particles was measured to be 22 nm with a relatively narrow size distribution, although there was no specific stabilizer for Au nanoparticles.