Synthesis and Characterization of Zinc Oxide Nanoparticles Using Acacia caesia Bark Extract and Its Photocatalytic and Antimicrobial Activities

This paper presents the green synthesis and characterization of ZnO nanoparticles and their microbial and photocatalytic application. The green synthesis of ZnO nanoparticles was carried out using Zinc nitrate hexahydrate and the bark extract of Acacia caesia (L.) Willd. The nanoparticles were synthesized at an optimum temperature of 65 °C followed by calcination at 400 °C. The samples were characterized using UV-visible spectroscopy, SEM, XRD, FTIR and EDX analysis. UV-visible spectroscopy showed a characteristic peak at 338 nm and the bandgap energy was found to be 3 eV which is specific for ZnO. SEM confirmed the presence of ZnO on its nanoscale. EDX gave the elemental details of Zinc constituting to 37.77% and Oxygen comprising 20.77% of its atomic weight. XRD analysis gave the diffractogram indexed at various angles corresponding to ZnO nanoparticles. It also revealed the average crystalline size to be 32.32 nm and the shape was found to be hexagonal. The functional group present in the nanoparticles was characterized using FTIR, which gave a characteristic peak at 485 cm−1. The synthesized nanoparticles exhibited significant photocatalytic (methyl blue under UV irradiation). The presence of nanoparticles induces changes in its kinetics, whose rate constants and correlation coefficients were analyzed during the photocatalytic degradation of the model pollutant Methyl Blue. Studies on antibacterial (Escherichia coli, Staphylococcus aureus), antifungal (Aspergillus niger, Candida albicans) and anti-inflammatory (COX assay) properties were also carried out. The nanoparticles were synthesized in an eco-friendly and cost-effective method. The study opens new horizons in the field of water treatment, biosensors and nanotechnology.

Collinearity of alpha-helices or beta strands in membrane proteins causes a characteristic peak centred on 4.9 Å resolution in diffraction intensity profiles, inducing higher diffraction anisotropy

Diffraction anisotropy is a phenomenon that impacts more specifically membrane proteins, compared to soluble ones, but the reasons for this discrepancy remained unclear. Often, it is referred to a difference in resolution limits between highest and lowest diffraction limits as a signature for anisotropy. We show in this article that there is no simple correlation between anisotropy and difference in resolution limits, with notably a substantial number of structures displaying various anisotropy with no difference in resolution limits. We further investigated diffraction intensity profiles, and observed a peak centred on 4.9Å resolution more predominant in membrane proteins. Since this peak is in the region corresponding to secondary structures, we investigated the influence of secondary structure ratio. We showed that secondary structure content has little influence on this profile, while secondary structure collinearity in membrane proteins correlate with a stronger peak. Finally, we could further show that the presence of this peak is linked to higher diffraction anisotropy.SynopsisMembrane protein diffraction anisotropy originates from a peak at 4.9 Å resolution in intensity profiles, due to secondary structure collinearity.

Medical applications of porous silicon

Materials based on porous silicon are extremely attractive for biomedical applications due to their simple and flexible production, biocompatibility, biodegradability, controlled morphology, and multiple ways of introducing the drug into the body. This paper presents the results of studies of porous structures with a broad spectrum antibiotic ceftriaxone. It has been shown that the characteristics of the porous structure change upon saturation of the pores with the drug. It was shown that solutions of porous silicon + ceftriaxone have a characteristic peak at a wavelength of 1070 nm with increasing sonication time

Study on the Photochemical Reaction Process of 4-methyl-7-Hydroxycoumarin and Its Mechanism by Multi-Spectroscopic Technologies

The photochemical reaction process of 4-methyl-7-hydroxycoumarin (7H4MC) was studied by UV-Vis spectrometer and fluorescence spectroscopy. The results have shown that the characteristic peak of the UV-Vis spectra at 323 nm of 7H4MC undergoes a significant decrease in absorbance and a slight blue shift when was illuminated; the absorbance of the absorption peak at 279 nm rises, and there is a tendency for new peaks to appear. May be, there are structural changes or new materials generation. The addition of imidazole, VC, 3-indole methanol, GSH and other substances also have different effects on the photochemical reaction of 7H4MC. Among them, only imidazole has a certain inhibitory effect on the process of its photochemical reaction.

LIBS Monitoring and Analysis of Laser-Based Layered Controlled Paint Removal from Aircraft Skin

Reliability and controllability of selective removal of multiple paint layers from the surface of aircraft skin depend on effective online monitoring technology. An analysis was performed on the multi-pulse laser-induced breakdown spectroscopy (LIBS) on the surface of the aluminum alloy substrate, primer, and topcoat. Based on that, an exploration was conducted on the changes of the characteristic peaks corresponding to the characteristic elements that are contained in the topcoat, primer, and substrate with different layers of a laser action, in combination with analysis of microscopic morphology, composition, and depth of laser multi-pulse pits. The results show that the appearance and increase of the characteristic peak intensity of the Ca I at the wavelength of 422.7 nm can be regarded as the basis for the complete removal of the topcoat; the decrease or disappearance of the characteristic peak intensity can be regarded as the basis for the complete removal of the primer. Al I spectrum at the wavelength of 394.5 nm and 396.2 nm can be adopted to characterize the degree of damage to the aluminum alloy substrate. The feasibility and accuracy of the LIBS technology for the laser selective paint removal process and effect monitoring of aircraft skin were verified. Demonstrating that under the premise of not damaging the substrate, laser-based layered controlled paint removal (LLCPR) from aircraft skin can be achieved by monitoring the spectrum and composition change law of specified wavelength position corresponding tothe characteristic elements that are contained in the specific paint layer.

Deep-Level Traps Responsible for Persistent Photocurrent in Pulsed-Laser-Deposited β-Ga2O3 Thin Films

Gallium oxide (β-Ga2O3) is emerging as a promising wide-bandgap semiconductor for optoelectronic and high-power electronic devices. In this study, deep-level defects were investigated in pulsed-laser-deposited epitaxial films of β-Ga2O3. A deep ultraviolet photodetector (DUV) fabricated on β-Ga2O3 film showed a slow decay time of 1.58 s after switching off 250 nm wavelength illumination. Generally, β-Ga2O3 possesses various intentional and unintentional trap levels. Herein, these traps were investigated using the fractional emptying thermally stimulated current (TSC) method in the temperature range of 85 to 473 K. Broad peaks in the net TSC curve were observed and further resolved to identify the characteristic peak temperature of individual traps using the fractional emptying method. Several deep-level traps having activation energies in the range of 0.16 to 1.03 eV were identified. Among them, the trap with activation energy of 1.03 eV was found to be the most dominant trap level and it was possibly responsible for the persistent photocurrent in PLD-grown β-Ga2O3 thin films. The findings of this current work could pave the way for fabrication of high-performance DUV photodetectors.

Baseline Study of Rock Samples Collected From Paleolithic Archaeological Site of Attirampakkam, Tamil Nadu

In the present work, rock samples have been collected from Paleolithic archaeological site Attirampakkam, Tamil Nadu, India to assess the presence of mineralogical composition of samples using Fourier Transform infrared-spectroscopic (FT-IR) technique and these identified minerals are confirmed by using X-Ray Diffraction (XRD) technique. From FT-IR spectra the presence of minerals such as quartz, orthoclase, microcline, kaolinite, montmorillonite, dolomite, aragonite, and palygroskite minerals are identified in rock samples. In this samples quartz is the majorly presented mineral and crystallinity index of quartz (SiO2) is estimated for all the samples by comparing the ratio of intensity of the characteristic peak at 778 and 695 cm− 1 with the corresponding ratio for a standard sample. In rock samples, calculated crystallinity index of quartz is greater than 1 and shows that the disordered in nature. Additionally some more minerals such as hematite and rutile are identified in rock samples by X-ray diffraction technique. This extensive study shows that the archeological rock samples are wide variation in mineral composition.

Bioremoval of PVP coated silver nanoparticles using Aspergillus niger: the role of exopolysaccharides

The present work aims to study the removal of Polyvinylpyrrolidone coated silver nanoparticles (PVP-Ag-NPs) using Aspergillus niger and depict the role of exopolysaccharides in the removal process. Our results show that the majority of PVP-Ag-NPs were attached to fungal pellets. About 74% and 88% PVP-Ag-NPs were removed when incubated with A. niger pellets and exopolysaccharide-induced A. niger pellets, respectively. Ionized Ag decreased by 553 and 1290 fold under the same conditions as compared to stock PVP-Ag-NP. PVP-Ag-PVP resulted in an increase in reactive oxygen species (ROS) in 24h. The UV-Visible spectrum shows the disappearance of Ag characteristic peak and the broadness of the spectrum suggested an increase in size. Dynamic Light Scattering results showed an increase in PVP-Ag-NPs size from 28.4 nm to 115.9 nm for A. niger pellets and 160.3 nm after removal by stress-induced A. niger pellets and further increased to 650.1 nm for in vitro EPS removal. Our findings show that EPS can be used for nanoparticle removal, by increasing the net size of nanoparticles in aqueous media, this will, in turn, facilitate its filtration through conventional filtration techniques commonly used at wastewater treatment plants.

Simulation Research on Explosives Detection System Based on D-D Sealed Neutron Generator

A prompt gamma neutron activation analysis (PGNAA) system based on a deuterium-deuterium (D-D) sealed neutron generator was designed using the MOCA code for explosive detection. The system is mainly composed of four parts: D-D sealed neutron generator, moderator, shielding, and Lutetium Yttrium OxyorthoSilicate (LYSO) scintillation detectors. Polyethylene (PE) was selected as the moderator and the optimal thickness was 7cm. Lead, PE, and boron-containing polyethylene were used as shielding materials. In the optimized model, the LYSO detector is used to measure eighteen materials, such as wood, melamine, glucose, and nylon, and so on. Firstly, the nitrogen characteristic peak of 10.8 MeV was analyzed to determine whether the material contained nitrogen. Then, the ratio of characteristic peak counts of C/O and O/N were calculated to distinguish explosives from nitrogen containing materials. Finally, dinitrobenzene, nitroglycerin, TNT, and ammonium nitrate can be separated from nitrogenous substances by a discriminant algorithm. The final device can be used to detect the chemical composition of the threat substances, and the maximum dose rate of the system meets the limits of international protection standards.

Facile synthesis of a high purity α-MnO2 nanorod for rapid degradation of Rhodamine B

Manganese dioxide (α-MnO2) nanorods with diameters of about 5-15 nm and lengths of 100-150 nm were synthesized by a simple co-precipitation method. XRD, TEM, HRTEM, SAED and XPS were used to analyze the crystallographic information, microstructure and chemical bonding of the as-prepared sample. The α-MnO2 nanorod exhibited a high efficiency and rapid removal rate of rhodamine B (RhB), which reached about 97.5% within 10 min when pH=4 (and pH=6.6) and 97.7% within 50 min when pH = 9 in the presence of H2O2. The results also indicated that a lower pH value is conducive to the movement of the characteristic peak and the attenuation of the intensity of the characteristic peak of RhB dye. Then a possible catalytic mechanism was revealed. Moreover, the α-MnO2 nanorod exhibits an excellent recyclability and catalytic stability. This research indicates that α-MnO2 nanorods have a potential application in practical dye pollutant treatment.