Synthesis of Sheet Like Nanostructures of NiO Using Potassium Dichromate as Surface Modifying Agent for the Sensitive and Selective Determination of Amlodipine Besylate (ADB) Drug

The monitoring of hypertension drugs is very critical and important to sustain a healthy life. In this study, we have synthesized nickel oxide (NiO) nanostructures using potassium dichromate as surface modifying agent by hydrothermal method. These NiO nanostructures were found highly active for the oxidation of ADB besylate (ADB). The unit cell structure and morphology were investigated by scanning electron microscopy (SEM) and powder X-ray diffraction (XRD) techniques. The SEM study has confirmed the nano sheet like morphology and XRD analysis has described the cubic unit arrays of NiO. After the physical characterization, NiO nanostructures were used to modify the surface of glassy carbon electrode (GCE) by drop casting method. Then cyclic voltammetry (CV) was used to characterize the electrochemical activity of NiO nanostructures in the0.1 M phosphate buffer solution of pH 10.0 and a well resolved oxidation peak was identified at 0.70 V. The linear range for the NiO nanostructures was observed from 20–90 nM with a regression coefficient of 0.99 using CV. The calculated limit of detection (LOD) was 2.125 nM and the limit of quantification (LOQ) was 4.08 nM. Further to validate the CV calibration plot, an amperometry experiment was performed on the NiO nanostructures and sensors exhibited a linear range of 10 nM to 115 nM with LOD of 1.15 nM. The proposed approach was successfully used for the determination of ADB from commercial tablets and it reveals that the sensor could be capitalized to monitor ADB concentrations from pharmaceutical products. The use of potassium dichromate as a surface modifying agent for the metal oxide nanostructures may be of great interest to manipulate their crystal and surface properties for the extended range of biomedical and energy related applications.     

Synthesis,characterization of V2O5 nanoparticles and determination of catalase mimetic activity by new colorimetric method

Journal of Thermal Analysis and Calorimetry - This paper deals with an advanced colorimetric method used to determine the catalase mimetic activity of V2O5 nanoparticles by measuring the decrease...     

Copper vanadate nanowires-based MIS capacitors: synthesis,characterization, and their electrical charge storage applications

Dielectric properties of porous glass nanocomposites with TGS crystals embedded into six porous matrices with average pore size from 5 to 312 nm were investigated in the temperature range from 280 to 380 K at selected frequencies. The results are discussed based on the effect of the particle size on the phase transition temperature of TGS nanocomposites. Temperature–size phase diagram of TGS composites was derived. Non-monotonic character of the temperature-driven phase transition (T _p) with the decreasing particle size was determined. The nature of the T _p variation can be ascribed to the size-effect theoretically predicted by Zhong et al. (Phys Rev B 50:698–703, 1994).     

Hydrodynamic and electrical considerations in the design of a four-electrode impedance-based microfluidic device

A four-electrode impedance-based microfluidic device has been designed with tunable sensitivity for future applications to the detection of pathogens and functionalized microparticles specifically bound to molecular recognition molecules on the surface of a microfluidic channel. In order to achieve tunable sensitivity, hydrodynamic focusing was employed to confine the electric current by simultaneous introduction of two fluids (high- and low-conductivity solutions) into a microchannel at variable flow-rate ratios. By increasing the volumetric flow rate of the low-conductivity solution (sheath fluid) relative to the high-conductivity solution (sample fluid), increased focusing of the high-conductivity solution over four coplanar electrodes was achieved, thereby confining the current during impedance interrogation. The hydrodynamic and electrical properties of the device were analyzed for optimization and to resolve issues that would impact sensitivity and reproducibility in subsequent biosensor applications. These include variability in the relative flow rates of the sheath and sample fluids, changes in microchannel dimensions, and ionic concentration of the sample fluid. A comparative analysis of impedance measurements using four-electrode versus two-electrode configurations for impedance measurements also highlighted the advantages of using four electrodes for portable sensor applications.

Prediction of low-sensitivity reactive dye recipe in exhaust dyeing influenced by material to liquor ratio and nature of salt

Reactive dyeings were carried out by exhaust method on 100% cotton knits. A trichromatic combination was chosen with only change in blue component. Colorimetric data were produced under controlled dyeing conditions by comparing the color difference between the target shade and resulting shades. Giving a change in liquor ratio and nature of salt the colorimetric data were regenerated again produced the shades. The data will be helpful to predict the low-sensitivity reactive dye recipe, which lead to the concept of right-first-time dyeing. The aim of this research is to help a dyer to select the right recipe. A set of the dye recipes was applied by dyeing with reactive dyes on cotton. Sodium chloride shows best results in terms of dye sensitivity as compared to Glauber's salt at low liquor ratio that is 1:10. Blue BRF in combination with yellow and red shows best result as compared to navy blue BF.     

Caratuberside A2: A New Pregnane from Caralluma Tuberculata

A medicinal herb, Caralluma tuberculata (Asclepiadaceae), furnished a pregnane type compound, caratuberside A2. The sugar linkage was at C-14 which is a rare site of substitution. The structure was elucidated by spectroscopic means, including COSY-45, J-resolved, HMBC, HMQC, C-H correlation experiments and derivatization.     

Nonequilibrium spin transport through a diluted magnetic semiconductor quantum dot system with noncollinear magnetization

The spin-dependent transport through a diluted magnetic semiconductor quantum dot (QD) which is coupled via magnetic tunnel junctions to two ferromagnetic leads is studied theoretically. A noncollinear system is considered, where the QD is magnetized at an arbitrary angle with respect to the leads’ magnetization. The tunneling current is calculated in the coherent regime via the Keldysh nonequilibrium Green’s function (NEGF) formalism, incorporating the electron–electron interaction in the QD. We provide the first analytical solution for the Green’s function of the noncollinear DMS quantum dot system, solved via the equation of motion method under Hartree–Fock approximation. The transport characteristics (charge and spin currents, and tunnel magnetoresistance (TMR)) are evaluated for different voltage regimes. The interplay between spin-dependent tunneling and single-charge effects results in three distinct voltage regimes in the spin and charge current characteristics. The voltage range in which the QD is singly occupied corresponds to the maximum spin current and greatest sensitivity of the spin current to the QD magnetization orientation. The QD device also shows transport features suitable for sensor applications, i.e., a large charge current coupled with a high TMR ratio.     

Sensitive ultrashort pulse chirp measurement

The chirp of an ultrashort laser pulse can be extracted with high accuracy from a modified spectrum auto-interferometric correlation waveform by using a new time domain algorithm that allows signal averaging. We display results revealing high sensitivity to chirp even with signal-to-noise levels approaching unity. Correction algorithms have been developed to accommodate signal distortion arising from bandwidth limitations, interferometer misalignment, and nonquadratic detector response.     

Manipulating the degradation rate of PVA nanoparticles by a novel chemical‐free method

The high water solubility of poly (vinyl alcohol) (PVA) is one of the challenging problems in its application. In order to rectify this problem, PVA needs to be crosslinked. Freeze‐thawing in solid state as a novel physical crosslinking method was employed for enhancement the stability of PVA nanoparticles in aqueous solutions during this study. PVA nanoparticles were successfully prepared by electrospraying and electrospray conditions were optimized in the view points of polymer concentration and solvent system. The morphology of nanoparticles was tailored from collapsed particles and mixture of particles/fibers to spherical particle by manipulating of polymer solution concentration and solvent system. After preparation of PVA nanoparticles in optimum condition, they were frozen at ?20°C and subsequently thawed at 25°C for different cycles of 1, 2, and 3. Field‐emission scanning electron microscope (FE‐SEM), Fourier‐transform infrared (FTIR), X‐ray diffraction (XRD), differential scanning calorimeter (DSC), and biodegradation were used to evaluate the effect of freeze‐thawing on properties of PVA nanoparticles. FE‐SEM showed the spherical morphology of the PVA nanoparticles with sizes ranging from 200 to 300 nm. The FTIR spectroscopy indicated that the crystallinity of PVA nanoparticles increases after freeze‐thawing process. Moreover, by increasing the number of cycles, degree of crystallinity of nanoparticles increases. The XRD and DSC analysis of PVA nanoparticles again demonstrated the increasing of crystallinity of nanoparticles after freeze‐thawing process. The biodegradation behavior of PVA nanoparticles after freeze‐thawing exhibited the decreasing of degradation rate by increasing the number of cycles. Our overall results present a solvent‐less and safe method for crosslinking of PVA nanoparticles in solid state, which make it suitable for biomedical applications.     

Effect of ultrasonic waves on crocin and safranal content and expression of their controlling genes in suspension culture of saffron (Crocus sativus L.)

The expression of biosynthesis controlling genes of crocin and safranal in saffron (Crocus sativus) can be influenced by ultrasonic waves. Sterilized saffron corms were cultured in a ½-MS medium supplemented by 2-4-D and BAP. Saffron callus cells were treated with ultrasonic waves in a cellular suspension culture under optimal growth conditions. The samples were collected at 24 and 72 hours after treatment in three replications. The secondary metabolites were measured by high-performance liquid chromatography and the gene expression was analysed by the real-time polymerase chain reaction. Results indicate that this elicitor can influence the expressions of genes CsBCH, CsLYC and CsGT-2; the ultrasonic waves acted as an effective mechanical stimulus to the suspension cultures. The analysis of variance of the ultrasonically produced amounts of safranal and crocin indicates that there is a significant difference between once- and twice-treated samples in that the amount of safranal was the highest within the samples taken from the twice-treated suspension culture at 72 h after the ultrasound treatment, and the crocin was maximised after 24 h passed the twice-applied ultrasound treatment.