Current Nanomaterials - Volume 1, Issue 3, 2016

Background: Few layer graphene oxide was prepared by microwave irradiation which is convenient and less energy-consuming method. The enzyme immobilized graphene can be used for various applications including in the field of industrial, biomedical, waste-water treatment etc. Objective: The aim of the present study is to prepare graphene using fast and energy saving method and immobilization of Urease enzyme onto functionalized graphene sheet for various applications. Method: Few layer graphene oxides were prepared by microwave irradiation of graphite oxide. The graphene oxide was functionalized by L-cysteine and further used for the Urease enzyme immobilization. The morphology of as prepared graphene samples were investigated with the help of scanning and transmission electron microscope. Fourier-transform infrared spectroscopy was used to study the functionalities present on the graphene surface and also to confirm the attachment of urease enzyme on graphene sheet. Results: The TEM investigation revealed the transparent and smooth surface of graphene sheet. The enzyme molecules are presented nearly spherical in shapes onto the surfaces of the graphene sheet. The FTIR result confirms the presence of the amide functional groups in the enzyme immobilized functionalized graphene sample. The percentage immobilization was quite high i.e., 85% and the enzyme’s activity was also promising for the reusability. Conclusion: Microwave irradiation process results into a large volume expansion of the graphene powder. Functionalized graphene was used for the Urease enzyme immobilization. Percentage immobilization was significantly high showing ~85% with enhanced stability and reusability up to ten times with significant activity.

Background: Due to the single atomic layer, flexible material, easily tuned of band gap, easily reduced to reduced graphene oxide, graphene oxide (GO) have a lot of application for Electronics, Biosensors, Biomedical application. Objective: The goal of the present work is to study the electrochemical properties of graphene oxide flakes. Method: In the present work, we synthesis of graphene oxide using modified hummer techniques. The morphological and structural characterization of as-prepared GO was investigated with the help of XRD, SEM, FTIR, UV, CV. Results: The XRD patterns of As-prepared graphene oxide (GO) flakes shows a peak at 11.2°, and the calculated value of lattice parameter comes out to be 15.56 A°. The peaks in the Raman spectrum are observed at 1599 cm-1 and 1349 cm-1, which confirms the lattice distortion in the graphene oxide (GO). The peaks in the FTIR spectrum of graphene oxide (GO) observed at, 3636 cm-1, 1753 cm-1, 1649 cm-1, 1456 cm-1, and 1177 cm-1 are attributed to O-H, C=O, C=C, C-OH, C-O bonds, respectively. The electrochemical studies of graphene oxide (GO) modified ITO electrode shows an improvement in the electrochemical parameters. Conclusion: We have prepared the graphene oxide by modified Hummers method. According to the electrochemical studies, graphene oxide (GO) modified ITO electrode is an excellent medium for the fast electron transfer between an electrode surface and electrolyte. On the basis of these studies, it is suggested that graphene oxide may be a best material for the fabrication of biosensors.

Background: Perovskite sensitized solar cells have attracted photovoltaic researchers due to their outstanding photovoltaic performance and low cost synthesis. The fabrication of perovskite sensitized solar cells (PSSCs) involves the use of methyl ammonium Lead halides family. Objective: The aim of the present work is fabrication of low cost and efficient Perovskite sensitized solar cell. Method: First of all methyl ammonium iodide (CH3NH3I) was prepared by mixing 10ml of methylamine and 10ml of HI acid in a round bottle flask. The solution was taken to ice-bath treatment (0°C for 2 hrs) and the resultant product was kept in the oven (60°C, overnight) for complete vaporization. Results: This paper describes the synthesis of Perovskite material and fabrication of Perovskite sensitized solar cell making use of chemical route and doctor blading. Various properties like structural, morphological and photovoltaic properties of Perovskite sensitized solar cell has been described. Conclusion: We have synthesized a novel CH3NH3PbI3 material and characterized it by various experimental techniques. The bandgap of perovskite is determined to be 2.26 eV using UV-Vis absorption spectroscopy. The strucural characterization using XRD shows the formation of pure pervoskite material. A maximum IPCE of 14.6% is obtained at the 400nm wavelength. The fabricated PSSC using PEO-based solid electrolyte shows stable efficiency of 0.53% at 1 sun condition in the room environment.

Background: The study of chalcogenide at nano scale have great importance for understanding electrical, optical and structural properties because they having wide range of application for fundamental and technological studies. Objective: The aim of present work is to study the structural, optical and electrical properties of Se85In9Bi6 nano-chalcogenide thin films. Method: Melt-quenching technique was applied for bulk alloy preparation. The DSC and XRD measurements were done to confirm the nature of the alloy. PVCT had been used for the deposition of thin films of different thickness. FESEM and HRTEM were used to study the particle size and surface morphology. The optical studies were done by a computerized JASCO spectrophotometer and dcconductivity measurement was done under high vacuum. Results: The HRTEM and FESEM images show that the thin films contains high yield of nonoparticles. The absorption coefficient (α) and extinction coefficient (k) both increases as photon energy increase but both decreases as thickness increases. The optical absorption follows the rule of indirect transition and its value increases from 1.36 to 1.49 eV as the thickness increases from 20 to 80 nm. The dc conductivity increases as the temperature increases and activation energy increases as thickness increases. Conclusion: From the study of structural, electrical and optical characteristics of the Se85In9Bi6 nano chalcogenide thin films we found that due to change in thickness different parameters changes and we can say that our prepared sample has possible application for different devices.

Background: Since the available metals are not able to meet the desired structural, mechanical and electrochemical properties therefore composites and nanocomposites are being used now a days. Composites are an amalgamation of materials that are mixed together to develop new compound with special and superior properties as compared to the base material. Nanocomposite is a new approach in which out of two phase, any one phase should consist of single unit sized particle whose dimension lies in between 1 and 1000 nanometres (nm) but usually it lies between 1-100 nm Objective: The present paper provides an overview on the different types of nanocomposites, their manufacturing, mechanical behaviour & industrial applications. Method: Gupta et al. synthesized iron (Fe) - alumina (Al2O3) metal matrix nanocomposites synthesized via powder metallurgy technique. Composition selected for the study was in the range of 5-30wt% of Al2O3 in Fe matrix. Specimens were synthesized by ball milling, compaction and sintering in argon atmosphere in temperature range of 900-1100°C for 1 to 3 hour respectively. Results: It was found that due to reactive sintering between iron and alumina particles an iron aluminate (FeAl2O4) phase forms. Formation of nano iron aluminate phases and related properties also depend on processing parameters. It was also found that the mechanical and electrochemical properties varies with the sintering parameters which in turn depend upon the iron aluminate phase formation. Conclusion: Metal Matrix Nanocomposites are excellent for manufacturing materials having high strength in the case of shear & compression processes and have ability to work at elevated temperature.

Background: Due to its wide band gap, high exciton binding energy and high breakdown strength, the nanostructures of ZnO may find applications for electronic, photonic devices, and highfrequency applications. Objective: The aim of the present work is to study electrical transport of thin film composed of a-ZnO nanorods. Method: Physical vapour condensation method was employed to fabricate the nanorods of ZnO. The morphology of these nanorods was investigated with the help of scanning electron microscope. X-ray diffraction pattern of as-prepared thin film was recorded using X-ray diffractometer. For dc conductivity measurements, four-probe method was used. Result: The as-prepared ZnO nanorods have diameter ranging from 10-20 nm and the length is of order of few hundred nanometers. XRD pattern of film composed of ZnO nanorods suggests the amorphous nature. Temperature dependence of dc conductivity has been studied over the temperature range of (297- 4.2K). For the temperature range of 297-120K, Mott’s three dimensional variable range hopping (VRH) is applied to explain the electrical conduction. For lower temperature range (120 - 4.2K), 2Dvariable- range hopping in localized states near the Fermi level may be responsible for the transport of carriers. Conclusion: Variable range hopping mechanism (VRH) has been suggested for the entire temperature range (298-4.2K) on the basis of temperature dependence of dc conductivity data, which changes from 3D to 2D on moving to lower temperatures side (below 125K).

Background: Carbon black - silicon rubber nanocomposites are under consideration for medical applications involving tremor mitigation as well as general therapeutic applications involving muscle relaxation therapy. Method: Carbon black filled silicon rubber composites containing 40-100 phr (per hundred) carbon black were investigated for their electrical conductivity under different loads over time. Rheological experiments involving evaluations of the storage moduli, G´ for the composites were also performed to infer rate and strain dependence of the composites’ conductivity under compressive loads. Results: Due to the high deformability of silicon rubber, the percolation thresholds for carbon black - silicon composites were shown to be a function of compressive loads applied on them. Conductivity of such composites increased with time and compressive load levels applied. The rheological experiments revealed that strain level and frequency can also indirectly affect the resistivity/conductivity levels in carbon black -filled silicon rubber composites, with the storage modulus increasing monotonically with increasing frequency (rate), and the stiffness of the carbon black /silicon rubber composite decreasing with increasing strain levels. Thus, it becomes easier to compact the nanocomposite further at higher strain levels and we would expect the rate of decay in resistivity to be lower at higher rates of pressure application. Conclusion: Our experimental results reveal that the two important service parameters, strain level and loading rate can be used for controlling the resistivity/conductivity levels in carbon black-filled silicon rubber composites.

Background: The impending energy crisis and increasing environmental pollution have prompted researchers to look for new functional materials to efficiently address these issues. In this context the useful properties of thermoelectric materials can be harvested to tackle the aforementioned issues. Based on the synergistic interplay of properties of carbon nanotubes and conducting polymers (in particular polyaniline) their nanocomposite can be utilized efficiently to replace the conventional inorganic thermoelectric materials. Method: Multiwall carbon nanotubes (CNTs) were subjected to acid refluxing to form functionalized CNTs (FCNTs) with carboxylic functionality and improved dispersibility in solvents. Subsequently, FCNTs filled polyaniline (PANI) matrix based composite (PFCNT) is formed and its thermoelectric (TE) performance is evaluated. Results: The electron microscopy images provide the visual evidence of dispersion of FCNTs inside PANI matrix and formation of heterojunctions. The FCNT composite displays optimum electrical conductivity & Seebeck coefficient which in combination with low thermal conductivity facilitates the realization of moderate yet promising value of TE figure of merit (i.e. ZT value) reaching ~0.001 at room temperature. Conclusion: We have successfully functionalized CNTs (FCNTs) and synthesized FCNTs/PANI composites (PFCNT) by wet phase physical mixing of the phases. The heterostructure formation between FCNTs and PANI enables the PFCNT composite to exhibit a promising value of TE figure of merit (ZT~0.001) at room temperature.

Objective: To prepare sustained release micro-/nanospheres of Ketoprofen (KFN) loaded Eudragit ® RS100 with ethyl cellulose and polycaprolactone (PCL). Method: The sustained release micro-/nanospheres of Ketoprofen (KFN) loaded Eudragit® RS100 with ethyl cellulose and polycaprolactone (PCL) were prepared by single emulsion [oil-in-water (o/w)] solvent evaporation method. Results: The resultant micro-/nanospheres were evaluated for their size, surface morphology, encapsulation efficiency and in vitro drug release. The prepared KFN loaded Eudragit® RS100 with ethyl cellulose micro-/nanospheres was showed encapsulation efficiency in the range from 59.81% to 96.14% while KFN loaded PCL micro-/nanospheres showed 54.46% to 88.52%. The micro-/nanospheres were found discrete and globular in shape. The absence of interaction between KFN and polymers were confirmed by Fourier Transform Infrared spectroscopy (FTIR). The X-ray diffraction (XRPD) revealed the dispersion of drug within micro-/nanospheres formulation. The in-vitro drug released study showed sustained release drug profile over a period of 12 h. Conclusion: These results could be helpful for finding the optimum formulation valuables for encapsulation efficiency as well as drug released profile of sustained release micro-/nanospheres.

Background: In the present article, thermal stability of single-layered graphene sheets (SLGSs) resting on Winkler–Pasternak elastic medium is investigated. Method: Eringen's nonlocal elasticity equations are introduced in novel four-variable plate theory considering the small-scale influences. The advantage of the presented theory is that, in addition to considering the small scale effect, the displacement field is expressed with only four unknowns by utilizing undetermined integral terms. Analytical solutions are determined for three types of temperature variations as uniform, linear and nonlinear temperature rise within the thickness of the SLGS. The effects induced by shear deformation, thickness ratio, size parameter, and elastic foundation coefficients are all examined.

Background: Titania (TiO2) is an environment-friendly semiconductor system with immense potential in the fields of photocatalysis, photovoltaics, sunscreen lotion and so on. In the past, nanoscale titania with inclusion of suitable dopants, were shown to improve optoelectronic, photochromic as well as antibacterial responses at large. Objective: To obtain a qualitative assessment of introduction of mixed phase, modified radiative emission and thermal stability due to inclusion of Ag into titania system. Method: A simple sol-gel route has been employed to synthesize un-doped and Ag-doped nano-titania systems. Results: Apart from diffraction peaks due to anatase phase of titania, the respective peaks (121) and (110) due to brookite and rutile phases have been witnessed in case of Ag-doped systems. In the photoluminescence spectra, the near band edge emission (NBE) peak has been located at ~407 nm, whereas ∼ 430 nm peak is assigned to the self-trapped excitons (STE) localized on the TiO6 2- octahedra. Thermogravimetric analysis (TGA) have revealed that, Ag- doped nano-titania systems could exhibit relatively low weight loss at high temperatures, as compared to their un-doped counterpart. Conclusion: X-ray diffractograms have revealed the co-existence of adequate rutile and brookite phases, apart from the dominant anatase phase after inclusion of Ag into titania. The manifestation in near band edge emission and defect related emission intensities have been witnessed in the luminescence spectra. The Ag-doped samples are thermally more stable as compared to the un-doped nano-titania system.