Biosynthesized gold nanoparticles supported on magnetic chitosan matrix as catalyst for reduction of 4-nitrophenol

The design and environmentally-safe synthesis of magnetically recoverable solid-supported metal nanoparticles with remarkable stability and catalytic performance has significant industrial importance. In the present study, we have developed an inexpensive bioinspired approach for assembling gold nanoparticles (AuNPs) in magnetic chitosan network under green, mild and scalable condition. AuNPs were well loaded on the surface of the magnetic support due to the presence of hydroxyl (-OH) and amino (-NH2) groups in chitosan molecules that provided the driving force for the complexation reaction with the Au(III) ions. Reduction of the Au(III) to Au(0) is achieved by using Melicope ptelefolia aqueous leaf extract. The synthesized magnetic chitosan supported biosynthesized Au nanocatalyst was characterized using Fourier Transform Infrared (FT-IR), Carbon, Hydrogen and Nitrogen (CHN), Transmission Electron Microscopy (TEM), X-Ray Diffraction (XRD) and Atomic Absorption Spectroscopy (AAS) analyses. FTIR spectrum of magnetic chitosan shows peaks at 1570 cm-1 indicative of N-H bending vibration and at 577 cm-1 which designates the Fe-O bond. CHN analytical data further supported the coating of chitosan onto the magnetite. TEM analysis shows an amorphous layer around the magnetite core which supported the coating of chitosan on the magnetite surface and the average particle size of AuNPs calculated was 7.34 ± 2.19 nm. XRD analysis shows six characteristics peaks for magnetite corresponding to lattice planes (220), (311), (400), (422), (511) and (440) in both the magnetite and magnetic chitosan samples (JCPDS file, PDF No. 65-3107). Meanwhile, XRD analysis of catalyst shows characteristic peaks of AuNPs at 2q (38.21°, 44.38°, 62.2°, 77.32° and 80.76°) are corresponding to (111), (200), (220), (311) and (222) lattice plane (JCPDS file, PDF No.04-0784). AAS analysis shows the loading of AuNPs as 5.4%. The rate constant achieved for the reduction of 4-nitrophenol to 4-aminophenol in the presence of hydrazine hydrate using 10 mg of catalyst is 0.0046 s-1. The magnetic chitosan supported AuNPs is effective as catalyst for the reduction of 4-nitrophenol.

A green in situ synthesis of silver nanoparticles on cotton fabrics using Aloe vera leaf extraction for durable ultraviolet protection and antibacterial activity

This study presented a simple and environmentally friendly method of in situ synthesis of silver nanoparticles (AgNPs) on cotton fabrics for durable ultraviolet (UV) protection and antibacterial activity using Aloe vera leaf extraction (AVE) as a reducing and stabilizing agent. Cotton fabrics were pretreated in water, and then immersed in AgNO3 and AVE, respectively. Cotton fabrics were characterized by small angle X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis, UV protection, antibacterial activity, and laundering durability. Comparing with the smooth surface of the control cotton fabric, SEM and energy dispersive X-ray spectrometry (EDX) results showed that there were a considerable number of Ag2O and AgNPs loading on the surface of the pretreated and Ag loaded cotton fabrics. The XRD pattern indicated, respectively, the existence of Ag2O and AgNPs, the structures of which were similar to JCPDS File No.65-3289 and JCPDS File No. 01-071-4613 on the pretreated and Ag loaded cotton fabrics. The pretreated and Ag loaded cotton fabrics showed excellent UV protection, antibacterial activity, and laundering durability, especially the Ag loaded cotton fabric, of which the UV protection factor value and transmission of UVA were 148 and 1.11%, respectively, after 20 washing cycles, and the clear zone width was more than 4 mm against E. coli or S. aureus. AgNPs facilitated the improvement of the thermal property of the cotton fabrics. Thus this facile in situ reduction of AgNPs with AVE may bring a promising and green strategy to produce functional textiles.

Microstructures of Zirconium Titanate Powders and Ceramics Prepared by Solid-State Mixed Oxide Method

Zirconium titanate (ZrTiO4): ZT powders were prepared by solid-state mixed oxide method. The mixed powder was calcined at various temperatures for 3 h ranging from 1100 to 1400 oC with a heating rate of 5 oC/min. X-ray diffraction analysis of the powders was performed using a diffractometer with Cu Ka. Pyrochlore phase was observed for calcinations below 1300 oC. In general, the strongest reflections apparent in patterns could be matched with a JCPDS file number 74-1504. The optimum calcination temperature for the formation of ZrTiO4 phase was found to be about 1300 oC for 3 h with heating rate of 5 oC/min. The microstructures of calcined powders were examined using scanning electron microscope (SEM). The particle size of powder increased with increasing calcination temperature. The ZT ceramics sintered at 1450, 1500, 1550 and 1600 oC for 4 h with heating rate of 5 oC/min, were checked for phase formation by X-ray diffraction. The density of sintered samples was measured by Archimedes method. The microstructures of sintered samples were examined using scanning electron microscope (SEM). The average grain sizes were checked by linear interception method. It was found that, the samples sintered at 1450 and 1500 oC gave rise to high purity ZT ceramics and the peaks matched well with ZrTiO4 phase in a JCPDS file number 74-1504. Unknown phases were found in ZT ceramics sintered at 1550 and 1600 oC. The value of density was in the range of 4.32 - 4.92 g/cm3 or 84.26 - 96.12 % of the ZT theoretical density. The densification of ZT ceramics decreased with increasing sintering temperature. The ZT ceramics sintered at 1450 and 1500 oC showed the average grain size of 8.55 and 12.55 µm, respectively. At sintering temperature 1550 and 1600 oC, morphology of grains changed to plate like crystals of second phases.

A new magnesium aluminium zirconium oxide, Mg5+x Al2.4−x Zr1.7+0.25x O12 with -0.4≲x≲0.4

The title compound has been synthesized by sintering oxide mixtures between 1975 and 2175 K. It decomposes at or below ca 1875 K. Quenched to room temperature, the phase is trigonal with ao = 3.2496(1), c0 = 25.221(1) Å, V = 230.65(2) Å3, Z = 1, Dm = 3.95(1) g cm−3, refraction indices ∊ D 293 K = 1.805(5), ω D 293 K = 1.855 (5) and birefringence Δ′ = 0.05. The JCPDS File No. for magnesium aluminium zirconium oxide is 34-1495.

A New Computer Algorithm for Qualitative X-Ray Powder Diffraction Analysis

An effective and practical computer algorithm has been developed for rapid and precise phase identification of polycrystalline materials by X-ray diffraction methods using the JCPDS database and/or user created standard files. The entire JCPDS file was reorganized for efficient search. Identifications are facilitated by a number of options: automatic correction of systematic errors using internal standard reflections, selectable window widths for file searching, elemental restrictions (chemical prescreening), handling preferred orientation, match without using intensities, match with 3 reflections, and others. A comprehensive algorithm for calculating a figure-of-merit (FOM) is used so that the “correct” phases can easily be identified with highest FOMs. This method has been tested extensively on a wide variety of analyses and is applicable to either a host or a minicomputer.