Temperature Controlled Evolution of Pure Phase Cu9S5 Nanoparticles by Solvothermal Process

Copper sulphides are one of the most explored semiconductor metal sulphides because of their stoichiometric and morphological dependent optical and electrical properties, which makes them tunable for numerous optoelectronic applications. Stoichiometrically, copper sulphides exist in numerous structures which varies from the copper-rich phase (Cu2S) to the copper-deficient phase (CuS). Within these extreme stoichiometric phases lies numerous non-stoichiometric phases with interesting optical properties. Different solvothermal techniques have been explored for the synthesis of copper sulphides; however, the thermal decomposition of single source precursors provides a facile and tunable route to the synthesis of pure phase copper sulphides of different stoichiometries. In this study, copper (II) dithiocarbamate have been explored as a single source precursor compound to study the evolution of pure phase Cu9S5. Below 240°C, mixed phase of CuS and Cu9S5 were obtained, and as the temperature was increased beyond 240°C, keeping other reaction condition unchanged, the precursor yielded pure phase of Cu9S5. This phase selectivity at high temperature was attributed to the increased reducing ability of oleylamine (used as solvent) which enhance the evolution of the copper rich phase at high temperature. Optical and morphological studies of the pure phase Cu9S5, showed properties that varied considerably with the temperature of synthesis

Harnessing the known and unknown impact of nanotechnology on enhancing food security and reducing postharvest losses : constraints and future prospects

Due to the deterioration of natural resources, low agricultural production, significant postharvest losses, no value addition, and a rapid increase in population, the enhancement of food security and safety in underdeveloped countries is becoming extremely tough. Efforts to incorporate the latest technology are now emanating from scientists globally in order to boost supply and subsequently reduce differences between the demand and the supply chain for food production. Nanotechnology is a unique technology that might increase agricultural output by developing nanofertilizers, employing active pesticides and herbicides, regulating soil features, managing wastewater and detecting pathogens. It is also suitable for processing food, as it boosts food production with high market value, improves its nutrient content and sensory properties, increases its safety, and improves its protection from pathogens. Nanotechnology can also be beneficial to farmers by assisting them in decreasing postharvest losses through the extension of the shelf life of food crops using nanoparticles. This review presents current data on the impact of nanotechnology in enhancing food security and reducing postharvest losses alongside the constraints confronting its application. More research is needed to resolve this technology’s health and safety issues

Laser assisted solid state reaction for the synthesis of ZnS and CdS nanoparticles from metal xanthate

Nanoparticles of CdS and ZnS were produced by a nanosecond laser using zinc (II) and cadmium (II) complexes of ethyl xanthate. Laser pulses with a peak wavelength of 355 nm, pulse repetition rate of 10 Hz, and pulse duration of ~ 4 ns were used. The sample exposure times were 10 min and 30 min respectively. The obtained nanoparticles were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), ultraviolet–visible spectroscopy (UV–vis) and photoluminescence (PL) spectroscopy. The morphology and optical property of the synthesized nanoparticles were investigated as a function of the time of exposure. Upon extensive irradiation, the crystallinity of the CdS nanoparticles increased while the crystallinity of the ZnS nanoparticles decreased. The average crystallite size of the CdS nanoparticles estimated from the TEM image was 4.8 nm, while the presence of aggregates with no crystalline edges impeded the size determination of the ZnS nanoparticles. The absorption spectra showed that the nanoparticles exhibit quantum confinement.National Research Foundation (NRF), South Africa and North West University, Potchefstroom, South Africa.http://www.elsevier.com/locate/matlethb201

Green synthesis of zinc oxide nanoparticles using plantain peel extracts and the evaluation of their antibacterial activity

The synthesis of nanoparticles via the green routes is an established technology for producing nano dimensional materials that are useful in different fields where environmental friendly materials are a major requirement. The present study reports a cost effective, eco-friendly and straightforward approach to synthesize zinc oxide nanoparticles (ZnONPs) using plantain peel extract. The optical, structural and morphological characteristics of the ZnONPs were studied using different techniques. X-ray diffraction analysis confirmed a hexagonal wurtzite structure, whose morphology and particle size, according to the transmission electron microscopy (TEM), was spherical and about 20 nm in size. The antimicrobial potency of the ZnONPs was evaluated using agar well diffusion and broth dilution assays against pathogenic strains of Salmonella enterica, Klebsiella pneumoniae, Bacillus cereus MTCC 430 and Staphylococcus aureus 26923, isolated from beef. The biosynthesized ZnONPs demonstrated good antimicrobial activity with a MIC value of 100 µg/mL for all the test isolates. Based on the results obtained, the antimicrobial efficacy of the nanoparticles against the selected bacteria followed the sequence: S. aureus ˃ B. cereus ˃ K. pneumoniae ˃ S. enterica. The results showed that plantain peels, which are the waste of these fruits, could be helpful for the green synthesis of ZnONPs with good antibacterial efficacy

Laser-assisted synthesis, and structural and thermal properties of ZnS nanoparticles stabilised in polyvinylpyrrolidone

Zinc sulphide (ZnS) nanoparticles have been synthesised by a green approach involving laser irradiationof an aqueous solution of zinc acetate (Znac2) and sodium sulphide (Na2S·9H2O) or thioacetamide (TAA)in polyvinylpyrrolidone (PVP). The structural and morphological properties of the prepared sampleswere analysed using a transmission electron microscope, TEM, a high resolution transmission electronmicroscope, HRTEM, X-ray diffraction, and Raman spectroscopy. The thermal properties were studiedusing a simultaneous thermal analyser (SDTA). Better dispersed and larger particles were obtained byusing sodium sulphide (Na2S) instead of TAA as the sulphur source. X-ray diffraction (XRD) analyses andRaman measurement show that the particles have a cubic structure, which is usually a low temperaturephase of ZnS. There were phonon softening and line broadening of the peaks which are attributed to thephonon confinement effect. The average crystallite size of the ZnS nanoparticles estimated from the XRDshowed a reduction in size from 13.62 to 10.42 nm for samples obtained from Na2S, and 9.13 to 8.16 nmfor samples obtained from TAA, with an increase in the time of irradiation. The thermal stability of PVPwas increased due to the incorporation of the ZnS nanoparticles in the matrices. The absorption spectrashowed that the nanoparticles exhibit quantum confinement effects.National Research Foundation(NRF), South Africa: Grant No. 77591; University of Pretoria’sResearch Development Programme (RDP), South Africa: GrantNo. A0W679 and North-West University, Potchefstroom, SouthAfrica.http://www.elsevier.com/locate/apsuschb201

Nanosecond laser irradiation synthesis of CdS nanoparticles in a PVA system

We herein report a modified, in situ photolytic process for the nucleation and growth of cadmium sulphide nanoparticles in the presence of an optically transparent and semicrystalline polyvinyl alcohol (PVA) polymer matrix. The laser causes a localized decomposition of the precursor species in the immediate vicinity of the polymer leading to highly confined nanocrystals. The as-synthesized PVA-CdS nanocomposite were characterized using UV–vis absorption and photoluminescence spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution TEM (HRTEM) and powdered X-ray diffraction (XRD). Strong blue shift in the band gap was observed in UV visible absorption spectrum indicating the size confinement. The influence of deposition temperature (25–200 ◦C) on the optical properties, microstructure, and thermal stability was also investigated. Thermal decomposition behaviors of these composites exhibit decreased thermal stability as indicated by the shift in the decomposition temperature of the pure PVA. XRD patterns revealed a reduction in the crystallinity of the polymer due to the entrapped particles. The nanocomposites showed the existence of both cubic and hexagonal phases.National Research Foundation (NRF), South Africa, and North West University, Potchefstroom.http://www.elsevier.com/locate/apsuschb201

Green synthesis of copper oxide nanoparticles using extracts of Solanum macrocarpon fruit and their redox responses on SPAu electrode

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Synthesis, Characterization and Thermal Studies of Zn(II), Cd(II) and Hg(II) Complexes of N-Methyl-N-Phenyldithiocarbamate: The Single Crystal Structure of [(C6H5)(CH3)NCS2]4Hg2

Zn(II), Cd(II) and Hg(II) complexes of N-methyl-N-phenyl dithiocarbamate have been synthesized and characterized by elemental analysis and spectral studies (IR, 1H and 13C-NMR). The single crystal X-ray structure of the mercury complex revealed that the complex contains a Hg centre with a distorted tetrahedral coordination sphere in which the dinuclear Hg complex resides on a crystallographic inversion centre and each Hg atom is coordinated to four S atoms from the dithiocarbamate moiety. One dithiocarbamate ligand acts as chelating ligand while the other acts as chelating bridging ligand between two Hg atoms, resulting in a dinuclear eight-member ring. The course of the thermal degradation of the complexes has been investigated using thermogravimetric and differential thermal analyses techniques. Thermogravimetric analysis of the complexes show a single weight loss to give MS (M = Zn, Cd, Hg) indicating that they might be useful as single source precursors for the synthesis of MS nanoparticles and thin films

Copper dithiocarbamates:Coordination chemistry and applications in materials science, biosciences and beyond

Copper dithiocarbamate complexes have been known for ca. 120 years and find relevance in biology and medicine, especially as anticancer agents and applications in materials science as a single-source precursor (SSPs) to nanoscale copper sulfides. Dithiocarbamates support Cu(I), Cu(II) and Cu(III) and show a rich and diverse coordination chemistry. Homoleptic [Cu(S2CNR2)2] are most common, being known for hundreds of substituents. All contain a Cu(II) centre, being either monomeric (distorted square planar) or dimeric (distorted trigonal bipyramidal) in the solid state, the latter being held together by intermolecular C···S interactions. Their d9 electronic configuration renders them paramagnetic and thus readily detected by electron paramagnetic resonance (EPR) spectroscopy. Reaction with a range of oxidants affords d8 Cu(III) complexes, [Cu(S2CNR2)2][X], in which copper remains in a square-planar geometry, but Cu–S bonds shorten by ca. 0.1 Å. These show a wide range of different structural motifs in the solid-state, varying with changes in anion and dithiocarbamate substituents. Cu(I) complexes, [Cu(S2CNR2)2]−, are (briefly) accessible in an electrochemical cell, and the only stable example is recently reported [Cu(S2CNH2)2][NH4]·H2O. Others readily lose a dithiocarbamate and the d10 centres can either be trapped with other coordinating ligands, especially phosphines, or form clusters with tetrahedral [Cu(μ3-S2CNR2)]4 being most common. Over the past decade, a wide range of Cu(I) dithiocarbamate clusters have been prepared and structurally characterised with nuclearities of 3–28, especially exciting being those with interstitial hydride and/or acetylide co-ligands. A range of mixed-valence Cu(I)–Cu(II) and Cu(II)–Cu(III) complexes are known, many of which show novel physical properties, and one Cu(I)–Cu(II)–Cu(III) species has been reported. Copper dithiocarbamates have been widely used as SSPs to nanoscale copper sulfides, allowing control over the phase, particle size and morphology of nanomaterials, and thus giving access to materials with tuneable physical properties. The identification of copper in a range of neurological diseases and the use of disulfiram as a drug for over 50 years makes understanding of the biological formation and action of [Cu(S2CNEt2)2] especially important. Furthermore, the finding that it and related Cu(II) dithiocarbamates are active anticancer agents has pushed them to the fore in studies of metal-based biomedicines