Search

Abstract A green, efficient synthesis of cadmium oxide decorated reduced graphene oxide nanocomposites (RGO/CdO) was prepared by one-step co-precipitation and hydrothermal method. Crystalline nature of the nanocomposites was characterized by X-ray diffraction analysis. To evaluate the structural morphology and particle size, high resolution transmission electron microscopy were used. X-ray photoelectron spectroscopy, Raman spectroscopy and Fourier transform infrared spectroscopy techniques were employed to establish chemical structure of the nanocomposites and Atomic Force Microscopy was done to measure the thickness. The optical properties were evaluated by UV–visible absorption spectroscopy. Thermo-gravimetric analysis, BET surface area and zeta potential measurements were carried out to study the thermal and surface characteristics. The CdO nano-particles (NPs) decorated on RGO sheets exhibit better electrical conductivity compared to RGO. The antibacterial activity of the nanocomposites has also been monitored in different culture media imparting good potentiality than RGO. Graphical abstract Unlabelled Image Highlights • RGO/CdO nanocomposite was successfully synthesized by adopting green route. • Dextrose acts as reducing and stabilizing agent which is nontoxic, low cost and easily available. • The electrical conductivity of the nanocomposite is higher than RGO. • The antibacterial property of the nanocomposite imparting good potentiality compared to RGO [ABSTRACT FROM AUTHOR]

Abstract The structure and dynamics of the second most abundant biopolymer α − chitin were studied by high resolution solid state 13C cross-polarization magic angle spinning nuclear magnetic resonance (CP-MAS-NMR) spectral analysis, 13C relaxation measurements at eight chemically different carbon sites and chemical shift anisotropy measurement by two-dimensional phase-adjusted spinning sidebands (2DPASS) magic angle spinning (MAS) solid state NMR method.13C spin-lattice relaxation time was measured by high resolution Torchia CP method. Spin-lattice relaxation rate (1 / T 1 ) of side chain carbon nuclei were remarkably high, because those nuclei possess higher degree of motional freedom. Chemical shift anisotropy parameters of eight chemically different carbon nuclei were determined by 2DPASS-MAS-NMR experiment. Large value of chemical shift anisotropy was observed for carbonyl group carbon (C 7) nuclei, because of electrostatic effect, hydrogen bonding and molecular magnetic susceptibility. 13C relaxation mechanism is mainly governed by chemical shift anisotropy interaction, especially at high value of external magnetic field (11.74 T). Thus, the correlation time at different carbon sites were also calculated by using the spin-lattice relaxation times and chemical shift anisotropy values. The correlation time of side chain carbon (C 8) was two orders of magnitude less than the carbonyl group carbon. These types of investigations would enlighten the correlation between the structure and dynamics of long polysaccharide chain compound. Graphical abstract Image 1 Highlights • Internal structure and dynamics of α − chitin at molecular level. • Determination of Chemical shift anisotropy by 13C-2DPASS SSNMR. • Determination of molecular correlation time. [ABSTRACT FROM AUTHOR]

An environmentally friendly method has been applied for the preparation of reduced graphene oxide (RGO). This method was developed by using polyphenols that contained a phytoextract of Mangifera indica L. along with Solanum tuberosum L. as reducing agents since they are non-toxic and naturally available. The phytoextracts used in the production of RGO was set between 60 and 70 °C. Graphene oxide (GO) was prepared by modified Hummer’s method as reported in earlier findings. Structural and morphological studies demonstrate that the part of the oxygen functionalities in GO can be removed by following green reduction. Characterizations of the resulting product have been done by X-ray diffraction, FTIR, UV–vis and Raman spectroscopy. FESEM, TEM, EDX spectrum, TGA, DLS and Zeta potential measurements of the samples have also been carried out to study the morphological, thermal and surface charge characteristics. Electrical conductivity was also measured to check the extent of reduction of GO to RGO. [ABSTRACT FROM AUTHOR]

Graphene has intriguing electrical, mechanical, thermal and biological properties that are being investigated for use in composites, modern electronics, membranes, and in the industry. Also, graphene has huge biological applications. Hydroxypropyl methylcellulose (HPMC) is a widely used bio-polymer effective for various biomedical applications. As a filler in this polymer matrix, graphene oxide (GO), reduced graphene oxide (RGO) and silver (Ag) nanoparticles (NPs) can be used to improve various properties of the matrix. They are also beneficial for bio-applications like drug delivery, the production of reactive oxygen species (ROS) and the antimicrobial properties of nanocomposite films. Here we synthesize a series of polymer nanocomposites taking GO, RGO and Ag NPs as a filler by the solution mixing method and explore the comparative biological application of such composites. We choose Ag NPs as it has the superior potential for multiple drug resistance. X-ray diffraction, Fourier-transform infrared and scanning electron microscope studies are used to describe how nanocomposites are formed. Energy-dispersive X-ray and dynamic mechanical analyzer analyses were also done to check elemental percentage in nanocomposite films and mechanical properties, respectively. To check several fruitful applications, antimicrobial properties, ROS generation and in-vitro drug release study of nanocomposite films with the loading of Ketorolac Tromethamine were also performed. [ABSTRACT FROM AUTHOR]

An environment-friendly approach for the synthesis of reduced graphene oxide/nickel oxide nanocomposites (RGO/NiO NCs) was done in a microwave via in-situ co-precipitation and hydrothermal mode. A non-toxic aqueous phytoextract was used as a reducing cum stabilizing agent. X-ray diffraction, Raman spectra, Fourier transform infrared spectroscopy analysis confirmed the chemical structure of the NCs. The morphological studies were investigated by scanning electron microscopy, high resolution transmission electron microscopy and energy disperse X-ray. The optical study was verified by UV–visible absorption spectroscopy. The photo-degradation activity was performed at visible light by exposing the methylene blue (MB) dye solution along with the NCs. Experimental result reveals the improved photo-catalytic activity of the NCs towards the photo-degradation of MB (93%) compare to pure NiO NPs (65%) and RGO (negligible). In the nanocomposites, the electronic charge transfer takes place superficially from NiO nanoparticles (NPs) to RGO, effectively delays the electron-hole pair (e − -h + ) recombination effect and increases the decomposition rate of the dye solution to some greater extent. The antibacterial activity of the NCs shows impressive potentiality in different culture media contrast with its constituent. • ➢ One step in-situ RGO/NiO nanocomposites has been synthesized adopting green route. • Psidium guajava L (guava) leaf extract is used as green reducing agent which is low cost and eco-friendly. • The nanocomposites shows better photocatalytic activity compared to NiO NPs and RGO. • Antibacterial activity of the nanocomposites is enhanced with respect to RGO and NiO NPs. [ABSTRACT FROM AUTHOR]

Passivated emitter rear contact (PERC) solar cell involves upgraded adaptation of technology over the existing silicon wafer-based aluminium back surface field (Al-BSF) solar cell. The lower efficiency of Al-BSF is caused by a few drawbacks e.g. higher rear surface recombination and weaker electric field at the rear surface. These technical shortcomings can be mitigated by incorporating field-effect passivation (FEP) layer viz. aluminium oxide (Al2O3) at the rear surface with a capping layer of SiNX on it. Conventionally two new processing steps utilizing two expensive equipments, green laser (532 nm) for laser ablation of the FEP and SiNX capping layer stack at the rear surface and single side etcher for rear side polishing of wafer are used for manufacturing of PERC cells. In this paper, we have shown that instead of these two new expensive processing equipments we can use the IR laser (1024 nm) and RIE etcher, which are commonly available for Al-BSF manufacturing line, for the fabrication of PERC solar cells. Using p-type wafers of rather modest quality (minority carrier lifetime of ≥10 µs) we have demonstrated improvement of the efficiency from 18.71 to 19.62% and enhancements in VOC and JSC from 628 to 646 mV and 38.59 mA/cm2 to 39.82 mA/cm2, respectively. A thorough root-cause analysis has been carried out to optimize the two new approaches within the existing Al-BSF line for the fabrication of PERC solar cell. [ABSTRACT FROM AUTHOR]

In this work, we report the development of a cross-linked bio-composite consisting of graphene oxide, potato starch, cross-linker glutaraldehyde and its application to adsorption of the industrial dye, methylene blue, from aqueous solution. The inexpensiveness, non-hazardous nature and easy bio-degradability are the major reasons for the selection of starch material as one of the components of the bio-composite. The bio-composite has been characterized by FTIR, SEM, XRD, particle size and zeta potential analysis. The FTIR analysis reveals the nature of the binding sites and surface morphology of the bio-composite can be understood through SEM. The auto-phase separability of the adsorbent i.e., the precipitation of the adsorbent without any mechanical means is another factor which makes this particular material very attractive as an adsorbent. Parameters like adsorbent dosage, pH, temperature, rotation speed and salt concentration have been varied to find out the suitable dye adsorption conditions. Furthermore, the time dependence of adsorption process has been analyzed using pseudo-first and pseudo-second order kinetics. The adsorption isotherms have been constructed to suggest convincing mechanistic pathway for this adsorption process. Finally, desorption studies have been successfully performed in 3 cycles, establishing the reusability of the material, which should allow the adsorbent to be economically promising for practical application in wastewater treatment. [ABSTRACT FROM AUTHOR]

Graphene and its related materials are important areas of research in recent years owing to their unique properties. The wide-range industrial application of graphene-related compounds has led to the development of novel and simple methods for the synthesis of graphene. In this paper, an environmentally friendly green synthesis for the partial reduction of graphene oxide (GO) to reduced GO (RGO) in a cost-effective single-step mechanism was reported. The method completely avoids the use of toxic and environmentally harmful reducing agents commonly used in the chemical reduction of GO to obtain RGO. The reduction of GO was carried out using aqueous leaf extracts of Paederia foetide L. The prepared GO and green RGO were characterized by ultraviolet-visible, Raman and Fourier transform infra-red spectroscopic analysis which showed a clear indication of the partial removal of oxygen-containing groups from the GO and the formation of RGO. The morphology of the green RGO was characterized by transmission electron and scanning electron microscopy. Dynamic light scattering was used for zeta potential measurement and correlated with the morphology of the sheets. Electrical conductivity was also measured to check the extent of reduction of GO to RGO. [ABSTRACT FROM AUTHOR]

Highlights: [•] Formation of GO is confirmed by XRD, FTIR and Raman spectral analysis. [•] HPMC/GO nanocomposites are developed. [•] XRD and SEM establish the formation of exfoliated HPMC/GO nanocomposites. [•] Enhancements in mechanical and thermal properties of nanocomposites are observed. [•] Moisture absorption and WVTR of HPMC film are declined with GO loading. [ABSTRACT FROM AUTHOR]

A nanocomposite of activated carbon (AC) and graphene oxide (GO) has been used as adsorbent of methylene blue (MB) dye from solution. FTIR spectroscopy, XRD, SEM imaging, size and zeta potential analysis of the nanocomposite material indicate retention of the essential features of both the components responsible for adsorption. Parameters like pH, temperature, adsorbent and salt concentrations, etc. were varied to optimize the adsorption. A very significant increase in adsorption by this nanocomposite, compared to those arising from the individual components, could be observed, resulting in an adsorption capacity of up to 1000 mg/gm. Fit of the data to kinetic equations gave rate constants for the process. Good fits to both Langmuir and Freundlisch isotherms indicated that the contribution of electrostatic attraction between the charged groups present in the composite and dye molecules, as well as the adsorption through AC surface pores both play significant roles. The synergy of these two different mechanisms yields the extraordinarily large adsorption capacity. This factor, together with the cheapness of the material, and its selectivity towards cationic dyes suggest its practical importance for water decontamination. Image 1 • Composite used as adsorbent involving graphene oxide (GO) and activated charcoal (AC). • Adsorption takes place through both the surface pores of AC and by electrostatic attraction from functional groups of GO. • Synergistic effects cause an increase in the adsorption capacity to 1000 mg/gm as compared to 180 mg/gm for AC. • Can adsorb cationic pollutants from a mixture of different components (neutral, anionic) and acts as a selective adsorbent. [ABSTRACT FROM AUTHOR]

Passivation of n-type and p-type monocrystalline CZ Si wafers (both polished and textured) with silicon oxide layers prepared by thermal (TO), chemical (CO) and plasma (PO) techniques have been extensively investigated from the measurement of minority carrier lifetime (τ) by transient electrical photoresponse method, density of interface states (N SS) measurement by capacitance – voltage study and silicon oxidation states by X-ray photoelectron spectroscopy (XPS) study of the SiO 2 /Si interface. It has been observed that N SS and τ have an inverse relation but the dependence is not linear. The method (TO, CO or PO) of oxide layer development has been found to play a crucial role to control the passivation of the c-Si wafer surface. It has been observed that the thermally grown oxide layer (TO) is superior among three oxide layers for all the different c-Si surfaces. Very low density of interface states (<5 × 1011) were found in both p-type and n-type polished wafer passivated with TO layer. Highest lifetimes of 170 μs for n-type polished wafer and 102.74 μs for p-type polished wafer were obtained with TO. The amount of sub oxide formed at the interface of both n- and p-type of wafers during different oxidation process, may have some correlation with N ss which in turn determines the passivation quality of the wafers. Improvement of implied V oc for both polished and textured wafers (n-type and p-type) was found using thermally grown oxide with respect to others. [ABSTRACT FROM AUTHOR]