Incorporation of thermally induced shaped and phases of manganese oxide nanoparticles into zein/PVA fiber blends.

Incorporation of nanomaterials into polymers and their blend provide additional advantages to their use and structural support. Metals such as Ag, Cu, Ti, and Fe are often reported in their metallic or their oxide forms for applications in microbiological, water treatment, and biomedical fields. The integration of metal oxide nanoparticles into polymer fiber blends overcomes the mechanical instability and compatibility challenges of nanomaterials. Manganese-based oxides provide good stability and optical properties in their nanoscale useful in polymeric composite or fiber materials enhancement. MnO2 and Mn2O3 nanoparticles were synthesized at different calcination temperatures using the co-precipitation method and characterized a microscopic technique TEM, and TGA. TEM images and the XRD patterns confirmed that the manganese oxide nanoparticle were spheres and rod-shaped with corresponding cryptomelane and orthorhombic crystalline phases. Mn2O3 nanoparticles were successfully integrated into zein/PVA (80/20) fiber blends. SEM images confirmed that the inclusion of the nanoparticles into zein/PVA solutions increased the conductivity of the solutions which led to an improved morphology and increased surface area to volume ratio. XRD patterns and TGA showed that the incorporated nanoparticles were below the detection limit, therefore there was no significant change observed. Therefore, all characterization techniques illustrated that the effect of concentration significantly enhanced the morphology of the fiber blends.

Porphyrins developed for photoinactivation of microbes in wastewater.

Photodynamic antimicrobial chemotherapy (PACT) is extensively studied as a strategic method to inactivate pathogenic microbes in wastewater for addressing the limitations associated with chlorination, ozonation, and ultraviolet irradiation as disinfection methods, which generally promote the development of resistant genes and harmful by-products such as trihalomethanes. PACT is dependent on photons, oxygen, and a photosensitizer to induce cytotoxic effects on various microbes by generating reactive oxygen species. Photosensitizers such as porphyrins have demonstrated significant microbial inactivation through PACT, hence now explored for wastewater phototreatment. This review aims to evaluate the efficacy of porphyrins and porphyrin-conjugates as photosensitizers for wastewater photoinactivation. Concerns relating to the application of photosensitizers in water treatment are also evaluated. This includes recovery and reuse of the photosensitizer when immobilized on solid supports.

Probing the stoichiometry dependent catalytic activity of nickel selenide counter electrodes in the redox reaction of iodide/triiodide electrolyte in dye sensitized solar cells.

Nickel selenide (Ni x Se y ) systems have received much attention in recent years as potential low cost counter electrodes (CEs) in dye sensitized solar cells (DSSCs). Their electrocatalytic activities are comparable to that of the conventional platinum CE. Despite their achievements, the effect of stoichiometry on their catalytic performance as CEs in DSSCs still remains unclear, hence the motivation for this work. Different stoichiometries of Ni x Se y were synthesized via a colloidal method in oleylamine or oleylamine/oleic acid mixture at the appropriate synthetic temperature and Ni to Se precursor ratio. X-ray diffraction revealed that different stoichiometries of nickel selenide were formed namely, NiSe2, Ni3Se4, Ni0.85Se, NiSe and Ni3Se2. Scanning electron microscopy showed that all the stoichiometries had predominantly spherical-like morphologies. Cyclic voltammetry, electrochemical impedance spectroscopy analysis and the photovoltaic performances of the DSSCs fabricated using the different Ni x Se y CEs revealed that selenium rich stoichiometries performed better than the nickel rich ones. Consequently, the catalytic activity towards the redox reaction of the triiodide/iodide electrolyte and hence the power conversion efficiency (PCE) followed the order of NiSe2 > Ni3Se4 > Ni0.85Se > NiSe > Ni3Se2 with PCE values of 3.31%, 3.25%, 3.17%, 2.35% and 1.52% respectively under ambient conditions.

Elucidating the effect of precursor decomposition time on the structural and optical properties of copper(i) nitride nanocubes.

To study the effect of time on the colloidal synthesis of Cu3N nanoparticles, copper(ii) nitrate was thermally decomposed at 260 °C for up to 60 min in octadecylamine as a stabilizing ligand. Thermolysis of the nitrate followed four steps which included; nucleation, growth, ripening and decomposition. At 5 min, partially developed nanocubes were found in a dense population of Cu3N nuclei. Well-defined Cu3N nanocubes were obtained at 15 min with no presence of the nuclei. TEM images showed disintegration of the cubes at 20 min and as time progressed, all the Cu3N decomposed to Cu by 60 min. The formation of the Cu3N nanocubes was confirmed by XRD and XPS. FTIR suggested the formation of a nitrile (RCN) as a result of the thermal decomposition in octadecylamine (ODA) and this was confirmed using NMR and hence, a reaction mechanism was then proposed. The optical properties of the as-synthesized Cu3N were studied using UV-vis and photoluminescence spectroscopies. The absorption spectra for particles synthesized from 5 min to 15 min showed a singular exciton peak while from 20 min to 60 min two peaks were observed. The two peaks may both be associated with the two direct transitions observed in Cu3N or the more red-shifted peak could be a result of localized surface plasmon resonance due to the Cu nanoparticles. Nevertheless, similar to other studies, it is clear that the optical properties of Cu3N are complex.

Chemically purified cellulose and its nanocrystals from sugarcane baggase: isolation and characterization.

Agro-wastes such as sugar cane bagasse can be explored for use in different aspects. Its applicability as a source of cellulose has attracted much interests especially in biomedical field among various applications. In the current work chemically purified cellulose (CPC) and cellulose nanocrystals (CNCs) were effectively extracted from sugarcane bagasse (SCB). The cellulose was obtained by chemical treatment of SCB using HNO3, NaOH and a bleaching agent. Nanocrystals were further prepared from the extracted cellulose using H2SO4 hydrolysis followed by washing with deionized water and acetone. The obtained materials were characterized for surface morphological using Fourier transform infrared (FTIR) spectroscopy, Transmission Electron Microscopy (TEM) and X-ray diffraction (XRD) analysis. The thermal properties were evaluated using TGA/DTG. The FTIR showed the disappearance of the peaks responsible for the hemicelluloses and lignin. These results were confirmed by TGA which proved gradual elimination of non-cellulosic constituents. X-ray Diffractometer depicted an increase in crystallinity occasioned by sequential treatments to get the cellulose nanocrystals. Cellulose nanocrystals had a spherical shape with a diameter of 38nm as compared to the chemically purified cellulose which had a diameter of 76nm. The CNCs prepared with this method were seen to be less agglomerated and more crystalline thus possess a higher potential as bionanocomposite either for biomedical applications or for wastewater treatment among other industrial application. This approach also provides an opportunity for the sugar companies to effectively manage their waste product.

Fabrication of a Schottky Device Using CuSe Nanoparticles: Colloidal versus Microwave Digestive Synthesis.

Herein we report on a nearly ideal Schottky diode device fabricated from Cu(2-x)Se nanoparticles synthesized using the microwave digestive method. The thermionic theory using data extracted from the experimental I-V curve resulted in the ideality factor of 4.35 and the barrier height of 0.895 eV whilst the Cheung's method resulted in the ideality factor, barrier height and series resistance of 1.04, 0.00259 eV and 0.870 Ω respectively. The Cheung's method is thought to be the most accurate as it takes into account the series resistance. The obtained values therefore are indicative of good diode behaviour of the device and this is a highly sought after goal in all electronic materials development.

A facile route for the synthesis of poly(N-vinylcarbazole)/manganese sulphide quantum dots nanocomposites with enhanced optical properties.

This communication describes a facile route for the synthesis of manganese sulphide (MnS) quantum dots (QDs) contained in poly(N-vinyl carbazole) (PNVC) nanocomposites. MnS QDs were synthesized using the single-source precursor method by thermolysing tetramethylthiuram disulfide manganese complex in hexadecylamine (HDA). Two different methods were used for the synthesis of MnS QD incorporated PNVC nanocomposites. The first method entailed the stirring of a mixture of MnS QDs and PNVC in chloroform (CHCl3) at room temperature and the second method was the refluxing of MnS QDs and PNVC solution in CHCl3 at an elevated temperature. A field emission electron microscope (FESEM) study revealed that the dispersion of MnS QDs in a PNVC matrix was improved in the case of nanocomposites prepared by the second method. The optical properties of pure PNVC were significantly altered for the case of nanocomposite prepared by the second route.