Micro and Nanosystems - Volume 5, Issue 1, 2013

Iron oxide nanoparticles (NPs) have been prepared in large-scale by wet-chemical method (150.0 oC and pH 8.33) using ferric chloride and urea as a starting materials in aqueous-alkaline medium. The structural, physical, and optical properties are characterized using FT-IR, UV–vis spectroscopy, Raman spectroscopy, powder X-ray diffraction, Fieldemission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS), and Electron diffraction system (EDS). The NPs size (average dia. 45 ± 5 nm) was measured by FE-SEM while the single phase of NPs were exemplified using powder X-ray diffraction technique. As-grown nanoparticles were applied for the photocatalytic degradation using acridine orange (ACR) and chemical sensing of aqueous ammonia. Almost 58.38% degradation with ACR was observed in presence of nanoparticles under UV sources (250 W). The silver electrode (AgE, surface area, 0.0216 cm2) was immobilized with NPs which enhanced ammonia-sensing performances in their electrical response (I-V characterization) for detecting and quantifying the ammonia in aqueous system. The analytical performances of NPs sensor were investigated that the sensitivity and stability of the sensor improved extensively using NPs thin-film on active silver surface. The calibration plot was linear (R =0.9337) over the large range of 5.0 μM to 0.5 M. The sensitivity was calculated as 4.6154 μAcm-2mM-1 with detection limit (2.5±0.2 μM), based on a signal/noise ratio (3N/S). This study has introduced a novel way for efficient chemical sensor development as well as active photo-catalyst using low-dimensional NPs for the detection of environmental carcinogenic and hazardous compounds.

Quantum chemical calculations have been carried out using Density Functional Theory (DFT) analysis with B3LYP method and Lanl2dz basis set to investigate (ZnO)n nano structures (n = 4–12) with substitution of Iron (Fe) as an impurity. We deeply investigated the effects after the substitution of one Fe atom in place of one Zn atom for each (ZnO)n nano structures. All the structures have been analyzed in detail and the relationship of the structural effects has also been discussed after the Fe substitution. The variation in Binding Energy (BE) as well as electronic properties have also been discussed. For the different cluster families relative energies were also calculated and the results obtained were compared to the previous works. In all cluster families, Binding Energy was found to increase when Fe was substituted and HOMO– LUMO energy gap was found to decrease when compared to the results of the pure form.

Manganese oxide nano-particles have been synthesized by hydrothermal process using aqueous combination of manganese chloride and urea as starting materials, where ammonium hydroxide is used as a reducing agent to adjust the pH at 10.55. The structural investigation of the as-grown nano-crystalline manganese oxide is analyzed by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), Fourier transform infrared spectrophotometer (FTIR), and Raman spectrophotometer, which revealed that the synthesized manganese oxide is well crystalline. Further, energy dispersive spectroscopy (EDS) confirms the composition of manganese oxide (Mn3O4) with Mn and O elements. UV-Visible absorption spectra (~293.44 nm) are used to investigate the optical properties of as-grown Mn3O4. The photocatalytic activity of the synthesized Mn3O4 is evaluated using color dye (Acridine Orange, AO), which degraded close to 47.38% in irradiation time (170 min). The chemical sensing of Mn3O4 coated electrodes has been primarily investigated by I-V technique, where ethanol is used as a model compound. The analytical performance of ethanol sensors exhibits the higher sensitivity (0.4777 μAcm-2mM-1) and a large linear dynamic range (0.17 μM to 0.17 M) in short response time (10.0 sec).

Environmental pollution is one of the global hot issues and need an urgent demand to detect and monitor the pollutants which affect the environment. Ammonia is one of the organic pollutants which cause severe harmful effect on environment due to its toxic nature. Therefore, electrochemical sensor has been fabricated using CeO2 nanoparticles (NPs) as a redox mediator to detect aqueous ammonia for environmental safety. The electrical response of the ethanol sensor was investigated by I-V technique which exhibited high sensitivity (0.3519 μA.cm-2.mM-1) and lower limit of detection (LOD = 0.395 μM). CeO2 nanoparticles were synthesized hydrothermally at low temperature and field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR), and Raman spectroscopy corroborated that the synthesized product is aggregated form of spherical nanoparticles, well crystalline possessing cubic phase with an average size of ~ 50 ± 10 nm. UV-Visible absorption spectrum confirmed that CeO2 nanoparticle is optically active with absorption band of 297 nm.

Non-trivial capacitance behaviour of gallium selenide (ε-GaSe) single crystals has been discussed. The emphasis of our discussion is focussed to the physical mechanism and theoretical interpretation of experimentally observed data. The crystal used for this purpose was grown by vertical Bridgeman technique (VBT). The grown crystal belongs to ε- polytype (ε-GaSe) with hexagonal crystal structure. The functions of ε-GaSe single crystals as a dielectric medium have been studied by measuring the capacitance with varying frequency and temperature. The obtained results revealed that at a constant temperature, the value of capacitance decreases with frequency while, for a given frequency, the value of capacitance gradually increases with temperature. Capacitance measured at room temperature was found negative in higher regions of frequency: an unusual behaviour.

The Single-walled carbon nanotube (SWCNT) based on 1-Amino-nonenthiol (ANT) was highly organized (nano level) forming an aggregated SWCNT-ANT self-assembled layer (SAL) on gold substrates. The fabricated nanosurfaces were investigated specially using FT-IR, cyclic voltammetry (CV), Raman spectroscopy, electrochemical quartz crystal microbalance (EQCM), and atomic force microscopy (AFM) techniques. The perpendicular aggregation of SWCNT-ANTs on chemically polished Au(111) substrates was fabricated by their spontaneous chemical bonding between carboxyl derivatized SWCNT-COOH and ANT SAL on Au(111), via peptide bonds, or directly by synthesized SWCNT-ANT composites. Raman spectroscopy and AFM surface images clearly revealed that the aggregated SWCNTANT (dia. 25-70 nm) has been organized on gold(111) substrates, forming a SAL with a random orientation.

Environmental friendly and biodegradable nanocomposite (NC) has been developed by efficient intercalation of poly propylene carbonate (PPC) into the interlayer space of cloisite 20B (C-20B) for biomedical and food packaging applications. The physicochemical and structural characterization was studied by X-ray diffraction (XRD) and Fourier transforms infrared spectroscopy. Thermal stability, mechanical property and anti-water sorption capacity of PPC and nanocomposite were scrutinized by thermal gravimetric analysis (TGA), differential scanning calorimeter (DSC), nanoindentation analyzer and thin film diffusion analyzer, respectively. Nanocomposite showed very high thermal decomposition temperature (Td50%) and 10 °C higher glass transition temperature when compared to pure PPC. In addition the nanocomposite exposes high elastic modulus, hardness and anti-water sorption property as compared to PPC. Therefore, this nanocomposite can be used in biomedical and food packaging applications.

In the regime of strong quantization single-electron states are considered theoretically in the wide-band semiconductor film, placed in a homogeneous electrostatic field. For a certain range of values of the external field, explicit expressions were obtained for the energy spectrum and envelope wave functions of charge carriers in the film. The dependence of the parameters of direct interband electro-optical transitions in the film on the intensity of the external field and the effective mass of charge carriers was also considered.

Microelectromechanical Systems (MEMS) technology allows the development of sensors with small size, lightweight, low cost, and high sensitivity. This paper presents the structural and electro-thermal design of a novel magnetic field sensor based on Sandia Ultra-planar Multi-level MEMS Technology V (SUMMTiV) process, which exploits the Lorentz force and operates at atmospheric pressure. The proposed sensor can detect magnetic field densities in twoorthogonal directions (2D) using an optical sensing technique. It is integrated by simple resonant structure of polysilicon beams (17 μm × 2.25 μm), and aluminum loop (13 μm × 0.7 μm) and a micromirror (60 μm × 60 μm). For an alternating current of 1 mA, the sensor has a theoretical linear response for magnetic field densities from 500 to 10000 μT, a bending resonant frequency of 7066 Hz, a theoretical sensitivity of 93.1 μm·T-1, a theoretical resolution of 410.3 μT and low power consumption close to 4.5 μW.