Green synthesis of lanthanum oxide nanoparticles using Moringa oleifera leaves extract and its biological activities

Phytosynthesis is a reliable way to produce metal nanoparticles without affecting the environment. Plant extracts act as reducing agent and favors nanoparticle synthesis. Recently, potential drugs were developed in nanotechnology platforms by the green synthesis approach. In this study, the leaves extract of ‘Moringa Oleifera’ (M. oleifera) used as a reducing agent for the synthesis of Lanthanum oxide nanoparticles (La₂O₃ NPs). The X-ray diffraction (XRD) confirmed the formation of body-centered cubic structure of La₂O₃ NPs. The optical behavior of La₂O₃ NPs was analyzed by UV–Vis spectrum. The bandgap energy of the La₂O₃ NPs was found to be 4.31 eV using Tauc’s plot. The morphology and purity of La₂O₃ NPs was analyzed by using Field Emission Scanning Electron Microscope (FESEM) and Energy Dispersive X-ray (EDX) spectrum. High Resolution Transmission Electron Microscope (HR-TEM) analysis reveals the morphology, lattice spacing, and selected area electron diffraction (SAED) pattern of the La₂O₃ NPs. The XPS analysis of the La₂O₃ NPs reveals the binding energy of La (3d_5/2 and 3d_3/2) and O 1s at 835.5, 852.3, and 536 eV respectively. The total antioxidant activity (TOA) of La₂O₃ NPs was found to be 75.32% at 500 µg/mL with the standard drug of vitamin C. The anti-inflammatory activity of the La₂O₃NPs was found to be 94.15% at 500 µg/mL using the bovine serum albumin denaturation (BSA) technique. The inhibitory activity of La₂O₃ NPs against α-amylase was found to be 79.99% at 500 µg/mL. In summary, the pure, highly stable and good biocompatible, greener approach based M. oleifera assisted La₂O₃ was synthesized for radical scavenging, α-amylase and BSA denaturation inhibition activities which can play a key role in the future biomedical and nano-biotechnological applications.     

Experimental development and deposition of nanocomposite films by a hybrid dc magnetron sputtering and cluster gun technique

A novel hybrid experimental prototype involving dc magnetron sputtering combined with an ingenious nanocluster source has been developed to deposit nanocomposite coatings by incorporating pre-formed clusters into a sputtered coating under high vacuum conditions. An electromagnetic fuel injector was connected with the nanocluster chamber and then optimised along with the sputtering chamber in order to incorporate the clusters in the coating matrix. The injection flux was primarily controlled by: the argon pressure and the amount of nanoclusters, the duration and repetition time of the injection and distance between the nozzle of the injector and the substrates. Several experiments were carried out on various substrates such as carbon tape, Al, Si and M2 steel with different nanoparticles of WO₃, SiC and WS₂. The preliminary characterization, consisting in the phase analysis, SEM micrographs and elemental composition, allowed confirming the presence of the clusters attached to the carbon tape when a free plasma injection was performed. Furthermore, the co-existence of Ti and TiN matrixes containing the SiC, WO₃ and WS₂ nanoparticles was confirmed.     

Optical investigations on indium oxide nano-particles prepared through precipitation method

Visible light emitting indium oxide nanoparticles were synthesized by precipitation method. Sodium hydroxide dissolved in ethanol was used as a precipitating agent to obtain indium hydroxide precipitates. Precipitates, thus formed were calcined at 600 °C for 1 h to obtain indium oxide nanoparticles. The structure of the particles as determined from the X-Ray diffraction pattern was found to be body centered cubic. The phase transformation of the prepared nanoparticles was analyzed using thermogravimetry. Surface morphology of the prepared nanoparticles was analyzed using high resolution-scanning electron microscopy and transmission electron microscopy. The results of the analysis show cube-like aggregates of size around 50 nm. It was found that the nanoparticles have a strong emission at 427 nm and a weak emission at 530 nm. These emissions were due to the presence of singly ionized oxygen vacancies and the nature of the defect was confirmed through Electron paramagnetic resonance analysis.     

Nanofibre-based bilayer biopolymer films: enhancement of antioxidant activity and potential for food packaging application

This study aimed to enhance the antioxidant property of biopolymer film without the incorporation of external agents. The active bilayer film with improved antioxidant activity has been developed by electrospinning zein, a prolamine of corn as nanofibre (average diameter of 286 nm) on solvent cast chitosan film. Zein nanofibres exhibited a slight increase in antioxidant activity as compared to solvent cast zein film. But, zein nanofibre coating on chitosan films significantly improved its antioxidant activity from 12.41% to 44.17%. The developed bilayer films were evaluated for its ability to prevent browning in minimally processed apple slices and compared with those of chitosan and zein films plasticised with polyethylene glycol. Higher surface to volume ratio and better affinity of zein nanofibres in the bilayer film helped enhance its anti-browning ability. Thus, zein nanofibre-coated chitosan bilayer films can be used as an effective anti-browning packaging material for the packing of minimally processed fruits.     

A facile method for synthesis of polyaniline nanospheres and effect of doping on their electrical conductivity

The synthesis of polyaniline (PANI) nanospheres by a simple template-free method has been described. The polymerization of aniline in aqueous medium was accomplished using ammonium persulfate without any protonic acid. The UV-vis spectrum of PANI nanospheres displayed the characteristic absorption peak of π-π* transition of the benzenoid ring at 355 nm. The oxidation state of PANI nanospheres was identified with FT-IR spectroscopy by comparing the two bands at 1582 (ring stretching in quinoid unit) and 1498 cm(-1) (ring stretching in bezenoid unit). The X-ray diffraction patterns demonstrated the low crystalline nature of PANI nanospheres. The morphology of PANI nanospheres was spherical and the mean diameter of nanospheres was found in the range of 3-12 nm. The thermal behavior of PANI nanospheres was studied by thermogravimetric analysis. The effect of doping of HCl and H(2)SO(4) on PANI nanospheres was studied by measuring the current as a function of time of exposure. The high electrical conductivity of 6×10(-2) S cm(-1) was obtained for PANI nanospheres at their optimum doping state by 100 ppm HCl.     

Metalloporphyrins encapsulated mesoporous molecular sieves as efficient heterogeneous catalysts for oxidation of cyclohexene with iodosylbenzene

The cationic Fe, Mn or VO porphyrins were encapsulated in Si, Al, Ti and V-MCM-41. The catalytic activity was investigated for the oxidation of cyclohexene with iodosylbenzene (PhIO) as oxidant. Manganese porphyrin supported catalysts produces epoxide as major products whereas iron and vanadyl porphyrins gave allylic oxidation products as major constituents. The results obtained clearly shows that the selectivity of various products depends not only on the nature of the support materials but also on the combined effects of metalloporphyrins and the supports. The recyclability of the heterogeneous catalysts was also investigated. The decrease in catalytic activity and leaching of active centers were observed when porphyrins were supported on Si-MCM-41.     

Optimization techniques for machining operations: a retrospective research based on various mathematical models

Simulated annealing, genetic algorithm, and particle swarm optimization techniques have been used for exploring optimal machining parameters for single pass turning operation, multi-pass turning operation, and surface grinding operation. The behavior of optimization techniques are studied based on various mathematical models. The objective functions of the various mathematical models are distinctly different from each other. The most affecting machining parameters are considered as cutting speed, feed, and depth of cut. Physical constraints are speed, feed, depth of cut, power limitation, surface roughness, temperature, and cutting force.     

Formation of nanostructured composites with environmentally-dependent electrical properties based on poly(vinylidene fluoride)-polyaniline core-shell latex system

Submicron poly(vinylidene fluoride) (PVDF)/polyaniline (PANI) core-shell latex particles are synthesized and examined as an active component in a simple conductometric chemical sensor. The structure and physical properties of these particles and nanostructured composite PVDF-PANI polymer films built of them are characterized with transmission electron, atomic force, and helium ion microscopy techniques, differential scanning calorimetry, and conductivity measurements. The nanostructured composite films with conductivity of about 4 × 10⁻⁴ S/cm suitable for sensor applications are prepared by casting from the core-shell particles dispersions on glass substrates patterned with silver electrodes followed by annealing at 180 °C, i.e. above T_m of the PVDF component. Sensor properties of these films are tested by measuring current-voltage (I-V) characteristics in response to varying concentration of NH₃ or HCl vapors. The developed thin film sensor heterostructures with electrically conductive percolation network of PANI as an active component and employing the conductometric detection scheme show high sensitivity to both analytes. However, the polymer material is especially efficient for application to NH₃ sensing with the detection limit as low as 100 ppb, and good reproducible recovery behavior upon repeated exposure to NH₃ at ambient conditions.     

Deposition of silver nanoparticles on dendrimer functionalized multiwalled carbon nanotubes: synthesis, characterization and antimicrobial activity

The nanohybrids composed of silver nanoparticles and aromatic polyamide functionalized multiwalled carbon nanotubes (MWCNTs) is successfully synthesized and tested for their antibacterial activity against different pathogens. Prior to deposition of silver nanoparticles, acid treated MWCNTs (MWCNTs-COOH) were successively reacted with p-phenylenediamine and methylmethacrylate to form series of NH2-terminated aromatic polyamide dendrimers on the surface of MWCNTs through Michael addition and amidation. Existence of high abundance of amine groups on the surface of functionalized MWCNTs (f-MWCNTs) provided sites for formation of silver nanoparticles by the reduction of aqueous solution of AgNO3. The silver nanoparticles formed in the resulted f-MWCNTs-Ag nanohybrids were determined to be face centered cubic (fcc) symmetry. The structure and nature of f-MWCNTs and f-MWCNTs-Ag nanohybrids were characterized by UV-vis spectroscopy, Fourier transform infrared spectroscopy (FTIR), powder X-ray diffraction analysis (XRD), Raman spectroscopy and thermogravimetric analysis (TGA). The dispersion state of f-MWCNTs and immobilization of silver nanoparticles on the surface of f-MWCNTs were investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Elemental composition of f-MWCNTs-Ag nanohybrids was determined by energy dispersive X-ray spectroscopy (EDS). The antimicrobial activity of f-MWCNTs-Ag nanohybrids were estimated against E. coli, P. aeruginosa and S. aureu and compared with MWCNTs-COOH and f-MWCNTs. The results indicate that functionalization of MWCNTs with aromatic polyamide dendrimers and successive deposition of Ag nanoparticles could play an important role in the enhancement of antimicrobial activity.