Spherical Copper Nanoparticles Research Articles

Role of Annealing Temperature on Improving the Hydrogen Storage Capacity of Copper Nano-Particles Decorated Carbon Nano Materials Synthesized from Sugarcane Bagasse

Abstract: This study focuses on improving hydrogen storage capacity of Carbon Nano Materials (CNMs) by investigating the role of annealing temperature for the synthesis of Copper Nano-Particles (CuNPs) decorated CNMs synthesized from sugarcane bagasse (SCB). SCB was pyrolyzed at around 750°C in an inert medium. Pyrolyzed carbon thus obtained was activated by alkali. These activated carbons were then decorated with CuNPs by annealing at different temperatures in CO2 atmosphere. The CNMs thus synthesized were characterized using XRD and Raman spectroscopic analysis to elucidate the structural intervention with particle size and defects respectively, while EDAX and ICP-AES were utilized to quantify the amount of copper deposited. SEM analysis depicts the porous morphology being decorated with spherical copper nanoparticles. Hydrogen Storage capacity was explored using Sievert’s apparatus. Pore volumes of CNMs synthesized at different annealing temperature were determined from adsorption isotherm co-relating it with hydrogen adsorption observation from Sievert’s apparatus for evaluating better hydrogen storage

A theoretical investigation on heat transport feature of Sutterby nanofluid flow above a conical surface

ABSTRACT Theoretical analysis is performed to examine the heat convection in hydromagnetic Sutterby nanofluid flow across a cone in the attendance of Darcy-Forchheimer and modified temperature flux effects. The enhanced heat transmission was investigated using Maxwell and interfacial layer (nanolayer) approaches by considering ethylene glycol (EG) based spherical copper (Cu) nanoparticles. An exact model is developed and verified numerically using the bvp5c MATLAB scheme. Simultaneous outcomes are obtained for Maxwell and nanolayer approaches. Pertinent parameters influence on momentum and energy fields is examined via plots and tables. The nanolayer approach reported higher thermal conductivity than the Maxwell approach. Also, modified heat flux commendably improves the heat diffusion rate of Sutterby nanofluid without affecting the wall resistance.

Electrochemical synthesis of copper-arabinoxylan nanocomposite for applications as antimicrobial agent and CO2 conversion catalyst

This study reports the electrochemical synthesis, antimicrobial and catalytic activity of copper-arabinoxylan nanocomposite. The synthesis was achieved without use of any hazardous reducing and stabilizing agent. The spherical copper nanoparticles (size approx. 40 nm) dispersed in the arabinoxylan matrix as they formed and got stabilized. In the absence of arabinoxylan the particles rapidly converted to copper oxide suggesting a high stability for the composite. Electrolysis was carried out with copper plate as the sacrificial anode, carbon rod as the cathode and sodium nitrate (1.00 % in 1 % arabinoxylan suspension) as an electrolyte. The copper nanoparticles dispersed in arabinoxylan were characterized by surface plasmon resonance spectroscopy, X-ray diffraction, electron microscopy and zeta potential measurements. The synthesized composite exhibited good antimicrobial activity against P. aeruginosa, Staph. aureus and E. coli and a catalytic activity in conversion of CO2 to methanol.

Water Saturated with Pressurized CO2 as a Tool to Create Various 3D Morphologies of Composites Based on Chitosan and Copper Nanoparticles.

Methods for creating various 3D morphologies of composites based on chitosan and copper nanoparticles stabilized by it in carbonic acid solutions formed under high pressure of saturating CO2 were developed. This work includes a comprehensive analysis of the regularities of copper nanoparticles stabilization and reduction with chitosan, studied by IR and UV-vis spectroscopies, XPS, TEM and rheology. Chitosan can partially reduce Cu2+ ions in aqueous solutions to small-sized, spherical copper nanoparticles with a low degree of polydispersity; the process is accompanied by the formation of an elastic polymer hydrogel. The resulting composites demonstrate antimicrobial activity against both fungi and bacteria. Exposing the hydrogels to the mixture of He or H2 gases and CO2 fluid under high pressure makes it possible to increase the porosity of hydrogels significantly, as well as decrease their pore size. Composite capsules show sufficient resistance to various conditions and reusable catalytic activity in the reduction of nitrobenzene to aniline reaction. The relative simplicity of the proposed method and at the same time its profound advantages (such as environmental friendliness, extra purity) indicate an interesting role of this study for various applications of materials based on chitosan and metals.

Sustainable Fabrication of Copper Nanoparticles: A Potent and Affordable Candidate for Water Treatment, Water Disinfection, Antioxidant Activity and Theranostic Agent

AbstractThis study reports a simple, green, and large–scale biosynthetic fabrication of spherical copper nanoparticles (Cu NPs), approximate 28 nm, using the aqueous extracts of Diaplazium esulentum (Retz.) Sw. fern. Characterization was carried out for morphology, size, elemental analysis, crystallinity and for identification of functionalities responsible for reduction and stabilization. Extraordinary remediation efficiency was obtained for the developed Cu NPs for the elimination of two industrially important pollutants; Methyl Violet 6B and Methylene Blue (greater than 92 % within 150 mins). A mechanism was postulated for the process using the data on the identification of NPs and also spent NPs apart from degraded products.Furthermore, the Cu NPs revealed excellent antibacterial activity against gram positive bacteria: Staphylococcus aureus, Streptococcus pneumonia and Bacillus subtilis, as well as gram negative bacteria: Pseudomonas aeruginosa, Escherichia coli and potential action against fungal strains; Aspergillus niger and Candida albicans.Additionally, the assay depicted that Cu NPs has fairly decent radical scavenging activity with IC50 value 2.11 mM.Moreover, the Cu NPs were found to exhibit profound anticancerous activity against two human cancer line cells.The present research work has implications for exploitation of DE fern extract for the development of Cu NPs and their numerous applications ranging from pollutants removal to antibacterial, antifungal, antioxidant and anticancerous agents.

Investigating convective heat transfer coefficient of nanofluid Couette flow in a nanochannel by molecular dynamics simulation

ABSTRACT The present study investigates convective heat transfer of nanofluid Couette flow. For this purpose, Ar-Cu nanofluid (argon as base fluid with spherical copper nanoparticles) is simulated using the LAMMPS package. The convective heat transfer coefficient is calculated for nanofluid and base fluid. The results show that the heat transfer coefficient increases with the addition of nanoparticles. This is due to changes in the structure and behaviour of the nanofluid relative to the base fluid. One of the important effects of the presence of nanoparticles is the constitution of solid-like layer adjacent to the nanoparticles, which increases the capability of heat transfer. Also, the velocity and mobility of base fluid are affected by the presence of nanoparticles, and velocity profile deviates from the linear mode. The effects of volume fraction and diameter of nanoparticles on convective heat transfer are also investigated. For a constant diameter of nanoparticles, the convective heat transfer coefficient of nanofluid increases by increasing the volume fraction. Likewise, in a constant volume fraction, the convective heat transfer coefficient decreases with increasing the nanoparticles diameter. This is because of the reduction in adsorption of fluid atoms by copper nanoparticles and decreasing the solid-like layer thickness.

Preparation and study of the physicochemical characteristics of multilayer polymer composites based on poly(ethyleneimine)-stabilized copper nanoparticles and poly(sodium 2-acrylamide-2-methyl-1-propanesulfonate)

Multilayer films were synthesized from a complex of branched polyethyleneimine (PEI) with copper nanoparticles (PEI-CuNPs) and sodium poly-2-acrylamide-2-methyl-1-propanesulfonate (PAMPSNa), applied layer-by-layer (LbL) on a solid support in an acidic medium. Protonation of the amino groups of PEI in an acidic medium increases the positive charge of the PEI-CuNPs system to +43.5 mV and promotes the formation of an interpolyelectrolyte complex between the positively charged PEI-CuNPs and the highly charged anionic polyelectrolyte PAMPS, the ζ-potential of which was -141 mV. AFM images and SEM micrographs showed a uniform distribution of spherical copper nanoparticles in the homogeneous structure of the multilayer film. The optical characteristics and hydrodynamic dimensions of PEI-CuNPs indicate the formation of PEI-CuNPs nanoparticles with sizes of 60-300 nm, with an average size of up to 100 nm. Copper nanoparticles distributed uniformly in a multilayer PEI-CuNPs/PAMPS film may be of interest for applications in the field of membrane catalysis, biochips, sensor membranes, and controlled drug delivery.

A Non-enzymatic glucose sensor via uniform copper nanosphere fabricated by two-step method

Herein, we explored an effective way to obtain uniform copper nanoparticles by irradiating Cu2O microparticles in ethanol with a 1064 nm laser. The morphology, structure and chemical composition of as-prepared copper nanoparticles were characterized by scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction and X-ray photoelectron spectroscopy. It is interesting that the diameter of obtained spherical copper nanoparticles can be finely tuned by changing the irradiation time. Moreover, we also found that the particle size of copper nanoparticles can be reduced to ~63 nm when the irradiation time is 30 min. Inspired by the fast-developing non-enzymatic glucose sensors, the electrochemical activity of the copper nanoparticles toward glucose in alkaline media was further investigated. Notably, the electrochemical results reveal that the prepared copper nanoparticles possess a good prospect in non-enzymatic glucose sensor.

Effects of copper nanoparticles on elastic and thermal properties of conductive polymer nanocomposites

Metallic nanoparticles are extensively used to enhance the thermal and electrical conductivity of polymer nanocomposites. However, despite many experimental studies on such composite materials, their computational analysis has remained unexplored to a large extent. In this study, we investigate the effects of cylindrical and spherical copper nanoparticles on the mechanical and thermal properties of polyethylene matrix using molecular dynamics and finite element methods. To calculate the density of the interphase zone and consequently, its elastic and thermal properties, LAMMPS package is used considering AIREBO, EAM, and Lennard‐Jones potential functions to model the interactions between nanocomposite components. Afterward, three-dimensional finite element modeling is done to obtain Young's modulus and thermal conductivity of the studied nanocomposites for different geometries, orientations, and volume fractions of nano-fillers. The results reveal that reinforcing polymer with copper nanofillers improves its thermal conductivity and elastic modulus, remarkably. Besides, nanoparticles with cylindrical geometry and [1 1 1] axial crystallographic orientation have a greater effect on the enhancement of properties than other orientations or spherical nanoparticles. Furthermore, the orientation of the nanoparticles inside the matrix in the direction of applied force and heat flux has the greatest impact on improving the properties of polymers compared to the other directions.

Single Step Microwave Assisted Synthesis and Antimicrobial Activity of Silver, Copper and Silver-Copper Nanoparticles

Copper and silver nanoparticles were synthesized and characterized in two minutes at 175°C in a one-step synthesis using a modified polyol (ethylene glycol) method and a microwave heating process. We successfully synthesized spherical Silver (Ag) and Copper nanoparticles (CuNP) with a crystallite size of less than 10 nm, as well as irregular silver-copper nanoparticles (AgCuNP) with a crystallite size of less than 15 nm, as confirmed by X-Ray Diffraction (XRD) and High-Resolution Transmission Electron Microscopy (HRTEM). The successful synthesis of AgCuNP with 1:1 molar ratio and constituted by 51.74% of copper and 48.26% of silver was corroborated using the Energy Dispersive X-ray (EDX) mapping technique. The AgNP and AgCuNP exhibited more stability in suspension, in comparison to CuNP, as observed by continuously monitoring the absorbance with UV-Vis spectroscopy for 12 days. Furthermore, the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of AgNP, CuNP, and AgCuNP were determined, against Gram-negative and Gram-positive bacteria, and yeast. The obtained MIC and MBC values indicate that AgCu nanoparticles exhibited bactericidal properties greater than its constituents. On the contrary, antifungal activity of AgCuNP against yeast was not observed.

Thermal Properties of the Binary‐Filler Hybrid Composites with Graphene and Copper Nanoparticles

AbstractThe thermal properties of epoxy‐based binary composites comprised of graphene and copper nanoparticles are reported. It is found that the “synergistic” filler effect, revealed as a strong enhancement of the thermal conductivity of composites with the size‐dissimilar fillers, has a well‐defined filler loading threshold. The thermal conductivity of composites with a moderate graphene concentration of fg = 15 wt% exhibits an abrupt increase as the loading of copper nanoparticles approaches fCu ≈ 40 wt%, followed by saturation. The effect is attributed to intercalation of spherical copper nanoparticles between the large graphene flakes, resulting in formation of the highly thermally conductive percolation network. In contrast, in composites with a high graphene concentration, fg = 40 wt%, the thermal conductivity increases linearly with addition of copper nanoparticles. A thermal conductivity of 13.5 ± 1.6 Wm−1K−1 is achieved in composites with binary fillers of fg = 40 wt% and fCu = 35 wt%. It has also been demonstrated that the thermal percolation can occur prior to electrical percolation even in composites with electrically conductive fillers. The obtained results shed light on the interaction between graphene fillers and copper nanoparticles in the composites and demonstrate potential of such hybrid epoxy composites for practical applications in thermal interface materials and adhesives.

Synthesis, Characterization, and In Situ Antifungal and Cytotoxicity Evaluation of Ascorbic Acid-Capped Copper Nanoparticles

The design route, synthesis, and characterization of spherical copper nanoparticles with antifungal potential are reported in the present work. Copper nanoparticles were synthesized by a novel, inexpensive, and eco-friendly chemical reduction method using ascorbic acid as a reductant and stabilizer under reflux conditions. The characterization results showed the formation of homogeneous, dispersed, and stable spherical ascorbic acid-capped copper nanoparticles (CuNPs) with a diameter of 250 nm. The CuNPs exhibited sustained antifungal activity againstCandida albicans(C. albicans) after 24 h and even 48 h of incubation. Using enhanced dark-field microscopy, we presented the in situ interaction between CuNPs andC. albicans. Here, part of the interaction of CuNPs among theC. albicans, studied without the use of any chemical and/or physical fixing method, is discussed. The results indicate that part of the antifungal mechanism involves a promoted adhesion of CuNPs onto the cell wall and a massive accumulation of CuNPs into the fungal cells, concluding in cellular leakage. The cytotoxicity (viability) evaluations indicated that our CuNPs were more biocompatible after comparison to the Cu precursor and triclosan (a commercial antifungal drug). The synthesized CuNPs will open up a new road for their possible use as a potent antimicrobial agent for clinical and industrial applications.

About the relevance of particle shape and graphene oxide on the behavior of direct absorption solar collectors using metal based nanofluids under different radiation intensities

Nanofluids based on spherical gold, silver, and copper nanoparticles, nonspherical silver nanoparticles, layered graphene oxides (GO), and GO/silver hybrid structures, were synthesized to analyze their effect on the thermal behavior of direct absorption solar collectors. The thermal conductivities at room temperature of all the nanofluids were similar, with values 4% higher than pure water, meaning up to three orders of magnitude differences compared to the values expected from the Maxwell model. Photothermal conversion experiments under simulated solar radiation with 1 Sun (=1 kW/m2) of intensity showed that all the spherical metal nanofluids presented up to 5 K higher temperatures and 35% increase of the efficiencies than pure water after 3000 s of irradiation. A much larger effect was seen with nonspherical silver and GO/silver hybrid particles, as these nanofluids presented around 20% higher efficiencies than pure spherical silver nanofluids. The large effect of silver morphology and the addition of GO led to further tests of these nanofluids under natural solar radiation using a parabolic dish mirror with a concentration ratio of 60. Under this high radiation, nanofluids showed up to 50 K higher temperatures and 100% increase in the efficiencies than pure water. Indeed, a boiling process after just 200 s was seen in nanofluids, while in pure water this phase change did not occur. Non-spherical silver nanofluids and GO/silver hybrid structures produced steam faster than spherical silver nanofluids. Our results confirm the relevance of the nanoparticles on the thermal conversion of nanofluids, with nonspherical silver nanofluids and GO/silver hybrid nanofluids presenting the best behaviors under low and high solar radiation.

New approach for more uniform size of Cu and Cu-CuO (core-shell) nanoparticles by double-salt reduction

We introduced a method for polyol synthesis of Cu-NPs in ethylene glycol (EG). This simple method takes place across the slow reduction of copper ions from copper nitrate and copper sulfate in ethylene glycol in the presence of a polymer surfactant (Polyvinylpyrrolidone: PVP), which was added to preclude agglomeration and provide dispersion stability to the final colloidal nanoparticles. Additionally, a double-salt reduction method enabled high-quality uniform nanoparticles to be obtained. The uniform size of the spherical copper nanoparticles could be controlled within the range of 10–55 nm by varying the synthesis parameters. Additional reducing agents were used to decrease reaction time, but these implantations had effects on the size and shape of the nanoparticles. Copper NPs mostly have a single crystal morphology. We also present an easy way to produce Cu-CuO NPs which can be used in different applications.

Nanoporous montmorillonite clay stabilized copper nanoparticles: Efficient and reusable catalyst for oxidation of alcohols

Stable and spherical copper nanoparticles of size less than 10 nm were generated into nanopores of activated montmorillonite clay and evaluated their catalytic activity for liquid phase alcohol oxidation to corresponding carbonyl compounds. Synthesis of copper nanoparticles was accomplished by incipient wetness impregnation of Cu(CH3COO)2 into the nanopores of the acid activated montmorillonite followed by reduction with NaBH4. The activation of montmorillonite was carried out by treating with mineral acid such as H2SO4 under controlled conditions at 80 °C to generate nanopores and high surface area. Powder-XRD, SEM-EDX, HRTEM, N2 adsorption, XPS etc. analysis were carried out to characterize the stabilized copper nanoparticles as well as the support. The synthesized copper nanoparticles may serve as a new alternative to ligand and additive free green catalyst for broad range of oxidation of alcohols with molecular O2 to corresponding carbonyl compounds with excellent yields (up to 97%) and selectivity (100%) under mild reaction conditions. The metal nanocatalysts exhibit good reusability, simple workup procedure and straightforward approach to carbonyl compound formation.

Non-Dependency of In Vitro Fungicidal Efficiency of Copper Nanoparticles against Fusarium oxysporum upon Particle Size

Although many papers have consented that the smaller the size of nanoparticles, the higher their efficiency, this paper sheds light on one potential exception of this rule. The paper shows that the in vitro antifungal efficiency of copper nanoparticles against the fusarium wilt pathogen, Fusarium oxysporum, isolated from the infected date palm, Phoenix dactylifera L., is not size-dependent; instead, as it was found that larger copper nanoparticles have better in vitro antifungal efficiency against the fungal pathogen than smaller ones. Copper nanoparticles were synthesized via chemical reduction method at two different pH values, 6.5 and 10.5. Dynamic light scattering was used to measure their particle sizes, which were 345.1 nm and 278.1 nm, respectively. Transmission Electron Microscopy was used to figure out the shapes of nanoparticles, which were polygonal and spherical, respectively. Poison food essay was used to test their in vitro inhibition efficiencies against the fusarium wilt pathogen, F. oxysporum, isolated from the infected date palm, Phoenix dactylifera L., which were 46% and 19%, respectively; at the same concentration. Ultimately, the paper has proposed and discussed a potential reason beyond these unexpected findings, which relies upon the larger surface area to volume ratio of the polygonal copper nanoparticles compared to the spherical copper nanoparticles. The paper concluded that, despite their larger size, polygonal copper nanoparticles have better in vitro antifungal efficiency than spherical copper nanoparticles against F. oxysporum isolated from the infected date palm, Phoenix dactylifera L. at the same concentration.

Thermophysical properties of water based Cu nanofluid used in special type of coil heat exchanger

The study shows the results of the investigation into thermophysical properties of water based copper nanofluid designed for a special type of coil heat exchanger requiring a specific working liquid. The nanofluid considered, characterized by low particle concentrations, was proposed as this liquid. The exact determination of its properties was the basis for further experimental and numerical examination of the exchanger. One of the exchanger’s heating coils was filled with a refrigerant. In order to prevent a possible refrigerant leakage a special buffer layer filled with the water based Cu nanofluid was mounted in the coil. The thermophysical properties of the nanofluid might lead to heat transfer enhancement in the buffer layer and thus improve the thermal characteristics of the exchanger. The density, viscosity and thermal conductivity of the Cu/water nanofluid were measured experimentally. Spherical copper nanoparticles of about 40nm in diameter were suspended in distilled water to produce test nanofluids. Three nanoparticle volume concentrations: 0.011%, 0.055% and 0.101% were examined. The dependencies associated with density, dynamic viscosity and thermal conductivity on temperature and particle volume concentration were determined. The experimental results obtained were compared with those which were calculated based on theoretical models. It was found that there was no compatibility of the measurements results with theoretical data in the case of viscosity and thermal conductivity. An attempt to explain this discrepancy was made.

A theoretical investigation of the optical properties of metal nanoparticles in water for photo thermal conversion enhancement

Nanofluids are used in photo thermal absorbers such as direct absorption solar collectors (DASC) to improve the absorption and heat transfer. A range of experimental studies have investigated the photo thermal conversion in nanofluids based on metal nanoparticles. The photo thermal conversion efficiency depends mainly on the ability of the metal nanoparticle based nanofluid to absorb light which in turn is governed by the particle localized surface plasmon resonance (LSPR). In this article we investigate the optical properties of metal nanoparticles in water, and based on this we judge their suitability for use in water based nanofluids. We simulate the optical properties and provide an overview of the absorption, scattering and extinction properties of solid and spherical aluminum, silver, copper and gold nanoparticles suspended in water. We study nanoparticle diameters between 20 and 140nm for the wavelength range 300–1350nm (200–1250nm for aluminum). We compare our simulation results with the available experimental results presented in the literature, and find good agreement.

Parametric Investigations on the Influence of 532 nm Nd:YAG Laser in Synthesizing Spherical Copper and Aluminum Nanoparticles Using Pulsed Laser Ablation Technique for Surface Plasmonic Applications

Parametric Investigations on the Influence of 532 nm Nd:YAG Laser in Synthesizing Spherical Copper and Aluminum Nanoparticles Using Pulsed Laser Ablation Technique for Surface Plasmonic Applications

Chemical Synthesis of Copper Nanospheres and Nanocubes and Their Antibacterial Activity Against Escherichia coli and Enterococcus sp.

The interest in synthesising inorganic nanomaterials for biological applications has increased in recent years, especially for antibacterial purposes. In the present study, spherical and cube-shaped copper nanoparticles were synthesised by a chemical reduction method and their efficacy as antimicrobial agents against both Gram-negative (Escherichia coli) and Gram-positive (Enterococcus sp.) organisms investigated. The nanoparticles were characterised using ultraviolet/visible spectroscopy, scanning electron microscopy, energy-dispersive spectroscopy and X-ray diffraction. Copper nanocubes were found to be more antimicrobial when compared with copper nanospheres, and it is postulated that whilst both sets of nanoparticles have similar total surface areas, the different shapes have different active facets and surface energies, which may lead to differing bactericidal behaviour.