Search Results

101 - 110 of 136 items :

  • Materials Sciences x
Clear All
Ultrasound assisted green synthesis of cerium oxide nanoparticles using Prosopis juliflora leaf extract and their structural, optical and antibacterial properties

Abstract

Cerium oxide nanoparticles (CONPs) were prepared using ultrasound assisted leaf extract of Prosopis juliflora acting as a reducing as well as stabilizing agent. The synthesized CONPs were characterized by ultraviolet-visible absorption spectroscopy (UV-Vis), particle size analyzer (PSA), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and high-resolution transmission electron microscopy (HRTEM). From the UV-Vis analysis, the optical band gap of the prepared CONPs (Eg = 3.62 eV) was slightly increased as compared to the bulk ceria (Eg = 3.19 eV). The phytochemicals in the extract reduced the particle size to 3.7 nm ± 0.3 nm, as it is evident from the PSA. FT-IR results confirmed the Ce-O stretching bands by showing the peaks at 452 cm-1. The Raman spectrumshowed a characteristic peak shift for CONPs at 461.2 cm-1. XRD analysis revealed the cubic fluorite structure of the synthesizednanoparticles with the lattice constant, a of 5.415 Å and unit cell volume, V of 158.813 Å3. XPS signals were used to determine the concentration of Ce3+ and Ce4+ in the prepared CONPs and it was found that major amount of cerium exist in the Ce4+ state. HRTEM images showed spherical shaped particles with an average size of 15 nm. Furthermore, the antibacterial activity of the prepared CONPs was evaluated and their efficacies were compared with the conventional antibiotics using disc diffusion assay against a set of Gram positive (G+) bacteria (Staphylococcus aureus, Streptococcus pneumonia) and Gram negative (G-) bacteria (Pseudomonas aeruginosa, Proteus vulgaris). The results suggested that CONPs showed antibacterial activity with significant variations due to the differences in the membrane structure and cell wall composition among the two groups tested.

Open access
Influence of L-threonine on the growth, structural, optical, mechanical and nonlinear optical properties of tartaric acid single crystal

Abstract

Single crystals of pure and L-threonine added tartaric acid (LT/TA), organic nonlinear optical (NLO) materials were grown from their respective aqueous solution by slow evaporation method. The crystalline nature of the grown crystals was confirmed by powder X-ray diffraction analysis (XRD). UV-Vis-NIR absorption and transmission spectra revealed that the lower cut-off wavelength was around 281 nm and the crystals exhibited high transmission over visible and near IR region. The presence of the functional groups such as O–H, C–H, C–O, C=O in the grown crystals was confirmed by FT-IR analysis. CHN analysis was carried out to confirm the presence of L-threonine in the grown crystals. Microhardness study on the crystals revealed that the hardness number Hv increased with the applied load. The growth pattern of the crystals were analyzed through etching analysis from which the etch patterns in the shape of ‘step-triangle’ were observed. The second harmonic generation (SHG) properties of pure and L-threonine doped tartaric acid crystals were confirmed by Kurtz-Perry powder technique.

Open access
Luminescent homo- and hetero-metallic hybrid molecular materials constructed by covalent grafting

Abstract

In this paper, 3-(triethoxysilyl)-propyl isocyanate (abbreviated as TESPIC) was modified by ethylparaben (EPB) to produce corresponding organic-inorganic monomers (EPB-TESPIC) with two components equipped with covalent bonds, which not only can coordinate to RE ions (Tb3+ and Eu3+) but also act as a sol-gel precursor. Luminescent hybrid materials consisting of terbium-europium complex, covalently bonded to silica-based network, have been obtained in situ via a sol-gel approach. Proton nuclear magnetic resonance spectroscopy (1HNMR) and Fourier transform infrared spectroscopy (FT-IR) were applied to characterize the structure of EPB-TESPIC. UV-visible, phosphorescence, and luminescence spectra were obtained to characterize the photophysical properties of the obtained hybrid material. Through co-hydrolysis and polycondensation, Tb3+ and Eu3+ can be introduced into the same organic-inorganic hybrid monomer, forming Si-O backbones. The experimental results show that the strong luminescence of rare-earth ions substantiates the optimum energy match and effective intramolecular energy transfer between the triplet state energy of coordination complex and the emissive energy level of the rare-earth ions. The hybrid material systems are expected to have potential applications in photophysical sensors.

Open access
Synthesis and characterization of fluorescent polyphenols anchored Schiff bases via oxidative polycondensation

Abstract

A series of polyimines, bearing phenolic groups were successfully synthesized in aqueous alkaline solution via chemical oxidative polycondensation. Polymeric Schiff bases were synthesized by condensation of 2,4-dihydroxybenzaldehyde and 3-hydroxy-4-metoxybenzaldehyde with 2-aminophenol and 3-aminophenol. The molecular structures of the synthesized Schiff bases and their corresponding polymers were studied by FT-IR, UV-Vis, 1H-NMR and 13C-NMR spectroscopic methods. Thermal stability of the imine polymers was evidenced by their initial degradation temperatures found in the range of 170 °C to 271 °C without any sign of melting. The results of UV-Vis and cyclic voltammetry (CV) measurements were coherent with the optical Eg and the electrochemical E′g band gaps of the polyimines which were lower than those of their corresponding Schiff bases. Fluorescence spectral analysis of P4 (Schiff base polymer P4 derived from 3-aminophenol and 3-hydroxy-4-methoxybenzaldehyde) revealed a bicolor emission with blue and green light. Electrical conductivity of the synthesized imine polymers was measured by four-point probe technique. P4 showed the highest electrical conductivity as a result of iodine vapor contact time. Morphology characterization of the synthesized polyimines was carried out using a scanning electron microscope SEM at different magnifications. The study revealed that P4 is a promising candidate for both blue and green light emitters which could be used in the production of photovoltaic materials and solar cells.

Open access
Facile microwave-assisted synthesis of Al:Mn co-doped PbI2 nanosheets: structural, vibrational, morphological, dielectric and radiation activity studies

Abstract

Herein, we report a successful development of nano-scale pure and Al and Mn co-doped PbI2 using facile microwaveassisted route. Structural study was done through X-ray diffraction analysis of grain size, dislocation density and lattice strain. The crystallite size was found to vary from 28 nm to 40 nm due to Al:Mn co-doping in PbI2. The presence of various vibrational modes was confirmed by FT-IR spectroscopy and red shifting was observed in peak positions compared to the bulk. Surface morphology, examined using a scanning electron microscope, confirmed the formation of single crystal nanosheets of a thickness in the range of 10 nm to 30 nm. The single crystal nanosheets were found to be transformed to large area nanosheets due to the doping. Enhancement in dielectric constant from ~7.5 to 11 was observed with increasing Al doping concentration. Linear attenuation coefficient was calculated and showed the enhancement of blocking gamma rays with increasing doping concentration. Its value was found to increase from 7.5 to 12.8 with the doping. The results suggest that the synthesized nanostructures can be used for detection and absorption of gamma rays emitted by 137Cs and 241Am sources.

Open access
Synthesis, characterization and fabrication of copper nanoparticles in N-isopropylacrylamide based co-polymer microgels for degradation of p-nitrophenol

Abstract

Poly(N-isopropylacrylamide-co-acrylic acid) [P(NIPAM-co-AAc)] microgels were synthesized by precipitation polymerization. Copper nanoparticles were successfully fabricated inside the microgels by in-situ reduction of copper ions in an aqueous medium. The microgels were characterized by Fourier Transform Infrared Spectroscopy (FT-IR) and Dynamic Light Scattering (DLS). Hydrodynamic radius of P(NIPAM-co-AAc) microgel particles increased with an increase in pH in aqueous medium at 25 °C. Copper-poly(N-isopropylacrylamide-co-acrylic acid) [Cu-P(NIPAM-co-AAc)] hybrid microgels were used as a catalyst for the reduction of 4-nitrophenol (4-NP). Effect of temperature, concentration of sodium borohydride (NaBH4) and catalyst dosage on the value of apparent rate constant (kapp) for catalytic reduction of 4-NP in the presence of Cu-P(NIPAM-co-AAc) hybrid microgels were investigated by UV-Vis spectrophotometry. It was found that the value of kapp for catalytic reduction of 4-NP in the presence of Cu-P(NIPAM-co-AAc) hybrid microgel catalyst increased with an increase in catalyst dosage, temperature and concentration of NaBH4 in aqueous medium. The results were discussed in terms of diffusion of reactants towards catalyst surface and swelling-deswelling of hybrid microgels.

Open access
Synthesis of V2O3/C composites with different morphologies by a facile route and phase transition properties of the compounds

Abstract

V2O3 and amorphous carbon composites (V2O3/C composites) with different morphologies (e.g. nanospheres, nanorods and nanosheets) were, for the first time, successfully synthesized by a facile hydrothermal route and subsequent calcination. The as-obtained samples were characterized by X-ray powder diffraction (XRD), energy dispersive spectrometery (EDS), elemental analysis (EA), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The morphology of V2O3/C composites could be easily controlled by varying the reaction time, and, as a result, V2O3/C composites with nanospheres, nanorods and nanosheets were selectively synthesized. Furthermore, the phase transition property of V2O3/C composites was measured by differential scanning calorimetry (DSC), suggesting that V2O3/C composites exhibit the phase transition similar to V2O3, which could expand the potential applications of materials related to V2O3 in the future.

Open access
Optical and structural properties of nanostructured copper oxide thin films as solar selective coating prepared by spray pyrolysis method

Abstract

Copper (II) oxide thin films were prepared by spray pyrolysis method on soda-lime glass substrates using copper acetate precursor solution. Influence of substrate temperature on structural and optical properties was investigated. Structural analysis of these layers were carried out by X-ray diffraction (XRD). Single phase nature and high crystallinity of CuO nanostructures were observed on XRD patterns. The general appearance of the films was uniform and black in color. FT-IR transmittance spectra confirmed the results from the XRD study. Selective solar absorber coatings of copper oxide (CuO) on stainless steel substrates was prepared by spray pyrolysis method. Effect of deposition temperature on optical properties of thin films was investigated. Optical parameters, absorbance (α) and emittance (α) were evaluated from reflectance data. It can be deduced that the porous structure, such as a light traps, can greatly enhance absorbance, while the composition, thickness and roughness of thin films can greatly influence the emissivity. Single phase nature and high crystallinity of CuO nanostructures were observed by XRD patterns. Solar absorbance of thin films were in the range of 85 % to 92 %.

Open access
In vitro evaluation of bioactivity of SiO2-CaO-P2O5-Na2O-CaF2-ZnO glass-ceramics

Abstract

Zinc is an essential trace element that stimulates bone formation but it is also known as an inhibitor of apatite crystal growth. In this work addition of ZnO to SiO2-CaO-P2O5-Na2O-CaF2 glass-ceramic system was made by conventional melt-quenching technique. DSC curves showed that the addition of ZnO moved the endothermic and exothermic peaks to lower temperatures. X-ray diffraction analysis did not reveal any additional phase caused by ZnO addition and showed the presence of wollastonite and hydroxyapatite crystalline phases only in all the glass-ceramic samples. As bio-implant apatite forming ability is an essential condition, the surface reactivity of the prepared glass-ceramic specimens was studied in vitro in Kokubo’s simulated body fluid (SBF) [1] with ion concentration nearly equal to human blood plasma for 30 days at 37 °C under static condition. Atomic absorption spectroscopy (AAS) was used to study the changes in element concentrations in soaking solutions and XRD, FT-IR and SEM were used to elucidate surface properties of prepared glass-ceramics, which confirmed the formation of HCAp on the surface of all glass-ceramics. It was found that the addition of ZnO had a positive effect on bioactivity of glass-ceramics and made it a potential candidate for restoration of damaged bones.

Open access
Structural and optical properties of VO2+ doped methacrylic acid ethylacrylate (MAA:EA) copolymer films

Abstract

Pure and VO2+ doped methacrylic acid ethylacrylate (MAA:EA) copolymer films were prepared by using a solution casting method. Various techniques including X-ray diffraction, Fourier transform infrared spectroscopy, ultraviolet-visible spectroscopy, scanning electron microscopy and electron paramagnetic resonance were employed for characterization of the samples. XRD patterns showed some degree of crystallinity of the doped polymer films due to interaction of the MAA:EA copolymer with VO2+. FT-IR spectral studies of pure and VO2+ doped MAA:EA copolymer films displayed significant structural changes within the doped copolymer film indicating the complexation. The optical absorbance of the pure and VO2+ doped films were measured in the 200 nm to 800 nm wavelength range. The values of the absorption edge and indirect band gaps were calculated. The optical band gap decreased with the increase of mol% of VO2+. From the EPR spectra, the spin- Hamiltonian parameters (g and A) were evaluated. The values of the spin-Hamiltonian parameters confirmed that the vanadyl ions were present in MAA:EA copolymer films as VO2+ molecular ions in an octahedral site with a tetragonal compression (C4v). The morphology of the copolymer samples was examined by scanning electron microscopy. The enhanced crystalline nature of the doped copolymer was identified from SEM analysis.

Open access