Abstract: Fungal skin infections are caused by different types of fungi among these Malassezia species is the common cause of the dermatitis in human and animals. In the present study, the skin scraping samples were collected from human and dog. The samples were inoculated into Saboraud and potato dextrose broth to achieve the fungal growth. The fungal species were isolated and characterized by colony morphology, potassium hydroxide (KOH) and lacto phenol cotton blue staining. Genomic DNA was isolated and the 28S rRNA was amplified from fungal species using the universal primers and the amplified PCR products were subjected to sequencing. The sequence analysis of 28S rRNA reveals that two sequences were similar to Malassezia globosa and one sequence is similar to Malassezia pachydermatis which causes dermatitis in human and dog, respectively. Further study was carried out to assess the antifungal activity of the silver nanoparticles synthesized through green synthesis using Azadirachta indica leaf extract and characterized by UV-Visible spectrophotometer, Transmission electron microscope (TEM), X-Ray diffraction spectrophotometer (XRD) and Fourier transform infrared spectrophotometer (FTIR). The characterized silver nanoparticles inhibit the growth of Malassezia species by forming zone of clearance. This study suggests that the silver nanoparticles could be an alternative to treat the fungal infections.
Abstract: Polyaromatic hydrocarbons (PAHs) are typically present in environmental samples at very low concentrations. Therefore, extensive sample preparation is necessary to enhance the signal for analytical determination of these compounds by classical methods based on chromatography or spectroscopy. In this study an electrochemical sensor for anthracene based on polyamic acid- graphene oxide (PAA-GO) nanocomposite electrode was prepared for application in the direct analysis of small volumes of samples with minimal pre-treatment steps. Polyamic acid and graphene oxide (GO) are materials with well-defined electrochemistry of their own and both are readily synthesised under ambient laboratory conditions. The sensor was prepared by cyclic voltammetric co-deposition of PAA and GO onto a commercial screen printed carbon electrode (SPCE) in five voltammetric cycles with initial and switch potentials of -1000 mV and +1000 mV, respectively, at a potential scan rate of 50 mV/s. The sensor materials (GO, PAA and PAA-GO) were characterised by Fourier transform infrared spectroscopy (FTIR), high resolution scanning electron microscopy (HRSEM) and cyclic voltammetry (CV), while their corresponding screen printed electrode systems (GO/SPCE, PAA/SPCE and PAA-GO/SPCE) were evaluated as possible chemical sensors for anthracene.
Abstract: First-principle ultrasoft pseudo potential approach of the plane wave based on density functional theory (DFT) has been used for studying the electronic characterization and optical properties of ZnO and Fe, Co doped ZnO. The results show that the doping impurities change the lattice parameters a little, but bring more changes in the electronic structures. The band gaps are broadened by doping, and the Fermi level accesses to the conduction band which will lead the system to show the character of metallic properties. The dielectric function and absorption peaks are identified and the changes compared to pure ZnO are analyzed in detail.
Abstract: Several types of N-alkyl-N,N-dimethyl quaternized chitosan (QC) derivatives with different alkyl chains were prepared as effective adsorbents towards reactive dye KN-R. QC with long dodecanyl chain was insoluble in neutral solution but could self-assembled into spherical nanoparticles. The effects of degree of quaternization and alkyl chain length on the adsorption properties of KN-R onto QC were investigated. The results showed that a higher degree of quaternization of copolymers led to a higher adsorption capacity. At similar degree of quaternization, QC nanoparticles with longer alkyl chains showed better adsorption ability than soluble free QC chain with shorter alkyl chains. Positive charges were accumulated on the surface of nanoparticles, which showed higher charge density than free polymer chain. The adsorption kinetics appeared to followed a well-described by pseudo-second-order model. Meanwhile, all of the obtained quaternized chitosan samples showed a higher adsorption capacity than the commercial adsorbent polyaluminium chloride. This work showed that adsorption ability of the cationic polymer could be improved by self-assembling into nanoparticles and that synthesized quaternized chitosan could be utilized as an efficient adsorbent for dye removal.
Abstract: Ferrites nanopowder of spinel MgxMn1-xFe2O4 (with x=0.0, 0.2, 0.4, 0.6, 0.8 and 1.0) synthesized by the coprecipitation method and pellets of nanopowder sintered at temperature 1250 °C. The X-ray diffraction results confirmed the single phase formation of the samples. The lattice constant and interionic distances decreased with increase in magnesium content that can be originated by strengthening of A–B interaction. The substitution effect of nonmagnetic Mg2+ ions was studied on Curie temperature of sintered pellets. Curie temperature measurements exhibit increasing trend with increase in magnesium content. Enhancement in Curie temperature can be explained on the basis of strengthening of A–B interaction and Neel’s two sub-lattice models.
Abstract: Quaternized polyvinyl alcohol (QPVA) was synthesized and used as an intermedium to improve dispersion of silica (SiO2) in natural rubber (NR). QPVA/SiO2 nanoclusters reinforced NR nanocomposite was prepared by latex compounding via electrostatic interaction. TEM micrographs demonstrated QPVA/SiO2 nanoclusters were distributed around NR particles, forming shell-core structure. The mechanical properties and thermal ageing resistance of NR-QPVA/SiO2 were significantly improved compared with that of neat NR. The tensile strength of NR-QPVA/SiO2 film was improved by 60%, when the SiO2 content is 3%. SEM pictures indicated SiO2 was homogenous dispersed throughout NR matrix in the presence of QPVA. It also demonstrated that SiO2 could enhance thermal stability of NR, as NR-QPVA/SiO2 had best surface morphology after 72 hours thermal ageing at 100 °C. The thermal decomposition temperature and glass transition temperature of NR-QPVA/SiO2 film increased to a higher temperature due to strong polymer–filler interaction, which also indicated that all the ingredients were compatible and homogenous.
Abstract: The purpose of this study was to develop a novel dental desensitizer with nitrogen-doped TiO2 nanoparticles that show an optical response under visible light and investigate the triggered release of chlorhexidine from these nanoparticles in response to remote visible-light irradiation. Diffusive ultraviolet-visible spectroscopy indicated that N-doped TiO2 nanoparticles solvothermally treated at 130°C for 2 h showed the highest absorbance at 470 nm. X-ray photoelectron spectroscopy confirmed that nitrogen was substantially doped into the TiO2 lattice via the existence of N–Ti–O or N–Ti–N linkages (396.1 eV of N 1s). Chlorhexidine-release and agar-diffusion antibacterial tests revealed that visible-light irradiation statistically accelerated the chlorhexidine release and antibacterial activity. An agar overlay biocompatibility test showed that only the 0.1% chlorhexidine experimental group was biocompatible according to ISO 7405. Therefore, N-doped TiO2 nanoparticles should enable the development of new visible-light-mediated antibacterial desensitizers in the field of dentistry.
Abstract: Regenerated silk fibers were fabricated through dry-wet spinning process using N-methyl morpholine N-oxide and methanol as solvent and coagulant, respectively. Several concentrations of polyhexamethylene biguanide (PHMB) (0.5, 0.75 and 1% (v/v)) and silver nanoparticles (AgNPs) (5, 15, 55, 95 and 135 ppm) were used as antibacterial agents. Antibacterial property of bio-fibers produced by either master batch or dipping process methods was compared to each other against a gram-positive bacterium, Staphylococcus aurous. Master batch process was indicated the dependency of antibacterial effect on the concentration of antibacterial agents as well as particle size. Maximum bactericidal activity in this process was obtained at concentrations of 55 ppm of AgNPs and 1% (v/v) of PHMB. The result from dipping process showed that various concentrations of PHMB can greatly influence on the results; the interaction of 55 ppm AgNPs and 0.75% of PHMB offered good inhibition effect with the least amount of color change on bio-fibers.
Abstract: Bacterial cellulose (BC) is a biopolymer with interesting properties, such as biocompatibility, high tensile strength, high absorption capacity, water retention and high crystallinity. Nanoparticles of titanium dioxide (TiO2) are extremely important in electrical applications, photocatalysis, sensors and biomedical areas. Multifunctional materials, based on bacterial cellulose, with differentiated properties can be designed from the BC/TiO2 nanocomposite by ex situ method of sol-gel immersion. It was manufactured as a nanocomposite consisting of BC/TiO2 hydrogel. Characterizations were carried out by scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) and fourier transform infrared spectroscopy (FTIR). The morphological analysis of nanocomposite revealed the existence of molecular interaction and adhesion between TiO2 nanoparticles and cellulosic nanofibers matrix, where the presence of Ti peaks in EDS spectra was discovered, proving the successful incorporation of nanoparticles. The FTIR showed modification on the functional groups, suggesting interaction between the components. The manufacturing of a BC/TiO2 nanocomposite by method of sol-gel immersion has a great potential for future applications.
Abstract: In this paper, the impact of three parameters including nanoparticles geometry, particles aggregation and borehole inclination on induced formation damage from water based drilling fluids were investigated by means of experimental studies. Accordingly, we designed a dynamic filtration setup capable to rotate and change well inclination. nanobased drilling fluids consisting of spherical, cubical and tubular shapes nanoparticles as fluid loss additives were used. Mud cake quality, core permeability impairment and degree of formation damage at various well inclinations were examined. The cluster structure of aggregated particles were determined using fractal theory and applying dynamic light scattering technique. For this purpose, drilling fluids were circulated at different well inclinations and at a constant differential pressure against a synthetic core. Field emission scanning electronic microscopy images taken from mud cakes confirmed the proposed cluster structures of nanoparticles. The experimental results show that the mud cake quality and degree of damage are functions of produced structure of aggregated particles. Moreover, by increasing the well inclination, the skin factor increases. However, this trend is intensively depended on particle geometry. Real time analysis of pore throat size to particle size ratio during mud circulation shows the tendency of particles to create external/internal filter cake is mainly related to well inclination and particle shape. The results can be used to optimize the size and shape of selected macro/nanoparticles as additives in drilling fluids to reduce formation damage in directional and horizontal wells during drilling operation.