International Journal of Nanoscience

Bulk SiO₂-based inorganic–inorganic sonogel (SG) hybrid glasses were fabricated with Ag/SiO₂ supported metal nanoparticles (MNPs). The catalyst-free SG route was implemented to produce these optically active nanostructured composites by doping the liquid sol-phase with Ag/SiO₂ synthesized according to the deposition–precipitation method. As prepared Ag/SiO₂-MNPs exhibited particle diameters below 10 nm and homogeneous size distribution. The easy and homogeneous Ag/SiO₂ loading within the micro/mesoporous SiO₂-SG network has evidenced the guest–host chemical affinity of these systems. This fact allowed us to fabricate outstanding chemically, photo-physically and mechanically stable bulk hybrid monoliths with controllable geometry and doping rates, suitable for linear and nonlinear optical (NLO)–spectroscopic characterizations. Indeed, the hosting SG matrix provided an elevated thermal and mechanical stability protecting the reactive Ag nanoparticles from environment conditions, diminishing their tendency to from aggregates and, above all, preserving their pristine photophysical properties. Comprehensive morphological, structural, spectroscopic and NLO characterizations were performed on the obtained SiO₂:(Ag/SiO₂) hybrid composites. Results have shown that the nanocrystalline (NC) properties, multipolar nature and small sizes of the implemented Ag/SiO₂-nanoparticles, together with the bulk guest–host mechanical interactions, play a crucial role for the observation of outstanding spectroscopic and quadratic NLO properties of the developed hybrid systems.

Selenium and silver have unique properties and great potential in the field of physics, chemistry and biology. The bacterial strain Pseudomonas fluorescens was isolated by using Kings'B media and Cladosporium sp. was isolated by using potato dextrose agar for soil sample collected from Andhra Pradesh coal field of Singareni. Rapid formation of stable silver and selenium nanoparticles (AgNPs; SeNPs) were observed on exposure of the microbial culture with solution of silver nitrate and sodium selenite. The nanoparticles were characterized by UV-visible spectroscopy, X-ray diffraction (XRD) and atomic force microscopy (AFM). Further, the biologically synthesized nanoparticles were found to have efficient antimicrobial activity against pathogenic bacteria, thus implying significance of the present study in production of biomedical products. AgNPs synthesized by P. fluorescens showed more antimicrobial activity than Cladosporium sp. As the AgNPs are much smaller in size, they showed effective antimicrobial activity when compared to that of SeNPs which showed less effective antimicrobial activity in both P. fluorescens and Cladosporium sp. The microbes are capable of reducing both AgNPs and SeNPs. The biological synthesis of nanoparticles is useful when compared with other physical and chemical methods as they are eco-friendly.

For maximizing productivity, minimizing cost, time-boxing process and optimizing human effort, a single-step, cost-effective, ultra-fast and environmentally benign synthesis suitable for industrial production of nanocrystalline ZnO, and Ag-doped ZnO has been reported in this paper. The synthesis based on microwave-supported aqueous solution method used zinc acetate dehydrate and silver nitrate as precursors for fabrication of nanorods. The synthesized products were characterized by X-ray diffractometry (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy and UV-Vis–NIR spectroscopy. The undoped and Ag-doped ZnO nanorods crystallized in a hexagonal wurtzite structure having spindle-like morphology. The blue shift occurred at absorption edge of Ag-doped ZnO around 260 nm compared to 365 nm of bulk ZnO. The red shift occurred at Raman peak site of 434 cm^-1 compared to characteristic wurtzite phase peak of ZnO (437 cm^-1). The bandgap energies were found to be 3.10 eV, 3.11 eV and 3.18 eV for undoped, 1% Ag-doped, and 3% Ag-doped ZnO samples, respectively. The TEM results provided average particle sizes of 17 nm, 15 nm and 13 nm for undoped, and 1% and 3% Ag-doped ZnO samples, respectively.

There are various potential applications in which carbon nanotubes (CNTs) may be subjected to bending in a cantilevered configuration leading to buckling which in turn may affect their electrical, electronic as well as load bearing properties. Using atomistic simulations, we study buckling and post-buckling behavior of six single-walled CNTs subjected to bending in cantilever loading (i.e., flexure in addition to shear and axial compression). Starting with small kinks on the compression side corresponding to locations of high strain energy density, ripples form on the tube wall as bending progresses, until the tube flattens maximally at a critical location giving rise to a stable hinge that rotates under continued bending. The critical buckling curvature, locations of initial and stable hinges and rotational properties of the hinge are determined. Beyond the linear elastic region, the rotational stiffness depends on the hinge angle dropping close to zero (at the same angle for each tube) before beginning to rise again, reminiscent of snap-through buckling of shells, a property that can be exploited for sensing and signal amplification applications.

Lithium titanate nanorods have been synthesized via the hydrothermal process using lithium acetate, titanium butoxide and ethylenediamine as raw materials. X-ray diffraction (XRD) analysis shows that lithium titanate nanorods are composed of orthorhombic Li₂Ti₃O₇ phase. Scanning electron microscopy (SEM) shows that the diameter and the length of lithium titanate nanorods are about 40–150 nm and 1 μm, respectively. UV-Vis diffuse reflectance spectrum indicates that the bandgap of the lithium titanate nanorods is 3.63 eV. Ethylenediamine plays an essential role in the formation of lithium titanate nanorods. Ethylenediamine-assisted nucleation and crystalline growth process have been proposed to explain the formation and growth of lithium titanate nanorods. Photocatalytic degradation of methylene blue (MB) dye over the lithium titanate nanorods has been investigated under UV-Vis light irradiation. MB solution with the initial concentration of 2.5 mgL^-1 can be degraded totally using 10 mg lithium titanate nanorods in 10 mL MB solution.

A new series of multi-walled carbon nanotube reinforced polybenzoxazine (MWCNT/PBZ) nanocomposites was successfully designed and developed. Three different maleimido terminal benzoxazine monomers (MI-BZs) were synthesized using N-(4-hydroxyphenyl) maleimide (HPM) and formaldehyde solution through Mannich condensation reaction and were characterized by FT-IR and NMR spectroscopy. Varying weight percentages (0 wt.%, 0.5 wt.%, 1.0 wt.% and 1.5 wt.%) of glycidyl-MWCNT were then incorporated into benzoxazine matrices to prepare MWCNT/PBZ nanocomposites. The nanocomposites having higher weight percentage of MWCNT were found to possess excellent thermal properties than those of neat PBZs. The developed nanocomposites exhibited better flame retardancy and higher dielectric constant. The optical properties ascertained from the UV-Vis absorption bands at the region of 300–350 nm and strong fluorescent emissions were observed in the wavelength range of 300–550 nm from Photoluminescence analysis. The intensity of characteristic diffraction peaks corresponding to g-MWCNT confirmed the reinforcement of MWCNT in the benzoxazine matrices, which indicated the successful formation of nanocomposites. The morphological studies ascertain the compatibility and uniform dispersion of MWCNT in the PBZ network.

The new era of portable electronic devices demands lesser power dissipation for longer battery life and design compactability. Leakage current and leakage power are dominating factors which greatly affect the power consumption in low voltage and low power applications. For many numerical representations of binary numbers, combinational circuits like adder, encoder, multiplexer, etc. are useful circuits for arithmetic operation. A novel high speed and low power half adder cell is introduced here which consists of AND gate and OR gate. This cell shows high speed, lower power consumption than conventional half adder. In CMOS technology, transistors used have small area and low power consumption. It is used in various applications like adder, subtract or, multiplexer, ALU and microprocessors digital VLSI systems. As the scaling technology reduces, the leakage power increases. In this paper, multi threshold complementary metal oxide semiconductor (MTCMOS) technique is proposed to reduce the leakage current and leakage power. MTCMOS is an effective circuit level technique that increases the performance of a cell by using both low- and high-threshold voltage transistors. Leakage current is reduced by 85.37% and leakage power is reduced by 87.45% using MTCMOS technique as compared to standard CMOS technique. The half adder design simulation work was performed by cadence simulation tool at 45-nm technology.

Magneto bound exciton and the charged exciton in a GaMn_0.02As/Ga_0.6Al_0.4As quantum dot are reported with the spatial confinement effect. The numerical calculations are carried out with the inclusion of exchange interaction between the carrier and the magnetic impurities. The binding energies of exciton and the trions and the optical transition energy are obtained as a function of dot radius. Numerical computations are followed using exact diagonalization method. The spin polaronic energy of the exciton and the charged excitons are obtained using a mean field theory in the presence of magnetic field strength. The magnetization of Mn ion impurities as a function of dot radius is investigated. The effective g-factor of conduction (valence) band electron (hole) is obtained in the GaMnAs quantum dot. The magnetic field induced size dependence of effective Landé g-factor is computed. The result shows that (i) the geometrical dependence on sp-d exchange interaction in the GaMn_0.02As/Ga_0.6Al_0.4As quantum dot has great influence with the geometrical confinement, (ii) the monotonic behavior of effective g-factor with the reduction of dot radius is observed, (iii) the Landé factor is more sensitive if the geometrical confinement effect is included and (iv) the value of effective g-factor increases when the spatial confinement is enhanced for all the dot radii. Our results show that the effective Landé g-factor can be manipulated negative to positive values in the GaMn_0.02As/Ga_0.4Al_0.6As quantum dot.

This paper presents the growth of bismuth ferrite (Bi₂Fe₄O₉) thin film by radio frequency magnetron reactive sputtering on p-Si (100) substrate and the characterization of the grown thin film. The deposited thin film is characterized by X-ray diffraction (XRD), field emission scanning electron micrograph (FESEM), energy dispersive X-ray analysis (EDAX), dielectric measurements and vibrating sample magnetometer (VSM) analysis. The XRD study reveals the orthorhombic structure of the crystallites and the particle size is calculated as 45 nm. The FESEM result confirms that the film has smooth surface and uniform distribution of nanoclusters. The percentage of chemical compositions of the film is confirmed by EDAX measurement. The dielectric behavior of the film is examined in terms of the dielectric constant and the dielectric loss as a function of frequency. The magnetic behavior of the film is measured using VSM with the applied magnetic field of about 1 Tesla and the result shows the ferromagnetic behavior of the sample at room temperature.

Carbon nanotubes have been observed to emit ultraviolet, visible and infrared radiation when exposed to microwaves. We have performed experiments in which both short (0.5 μm–2 μm) and long (5 μm–30 μm) single and double-walled carbon nanotubes were exposed to 2.46 GHz microwaves at a pressure of ~ 10^-6 Torr. Structural modifications of the carbon nanotubes due to microwave absorption have been studied using the Raman spectroscopy G-band and D-band intensities, which suggest that microwave irradiation at relatively low pressure results in an increase in nanotube defects, especially in the case of the long nanotubes. Furthermore, a comparison of the spectra of the radiation emitted from the nanotubes suggests that the longer nanotubes emitted radiation of much greater intensity than the shorter nanotubes. Based on the results of the experiments and results described in previous reports, the ultraviolet, visible and infrared radiation emitted as the result of microwave absorption by carbon nanotubes seems to be primarily blackbody radiation emitted due to Joule heating. However, the presence of several broad photopeaks in the spectra of the emitted radiation (which do not seem to be related to gases absorbed by the nanotubes or the presence of catalyst particles) suggest that emissions are not the result of Joule heating alone.

In this paper, a new ultra-compact optical biosensor based on photonic crystal (phc) resonant cavity is proposed. This sensor has ability to work in chemical optical processes for the determination and analysis of liquid material. Here, we used an optical filter based on two-dimensional phc resonant cavity on a silicon layer and an active area is created in center of cavity. According to results, with increasing the refractive index of cavity, resonant wavelengths shift so that this phenomenon provides the ability to measure the properties of materials. This novel designed biosensor has more advantage to operate in the biochemical process for example sensing protein and DNA molecule refractive index. This nanoscale biosensor has quality factor higher than 1.5 × 10⁴ and it is suitable to be used in the home healthcare diagnostic applications.