An efficient one pot synthesis of water-dispersible calix[4]arene polyhydrazide protected gold nanoparticles--a "turn off" fluorescent sensor for Hg[II] ions

In the present study, we report the synthesis of aqueous stable gold nanoparticles by using calix[4]arene polyhydrazide (CPH) as both reducing and capping agents. The calix[4]arene polyhydrazide reduced gold nanoparticles (CPH-AuNps) were characterized by UV/Vis, particle size analyzer (PSA) and transmission electron mictroscopy (TEM). The records confirmed high stability of CPH-AuNps in aqueous solution over a long period of time and even at varied pH. Additionally, CPH-AuNps have been investigated for its application as "Turn Off" fluorescent sensor for Hg[II]. A concentration of Hg[II] in the limit of 10 nM to 10 microM can be detected based on fluorescence quenching of the CPH-AuNPs and it was also concluded from the spectroscopic data that CPH-AuNPs possess excellent selectivity to Hg[II] over several metal ions like Pb[II], Cu[II], Cd[II], Mn[II], Zn[II] and Ni[II].     

Application of laser-induced breakdown spectroscopy for total carbon quantification in soil samples

The increase of greenhouse gas (i.e., CO(2)) levels in the atmosphere has caused noticeable climate change. Many nations are currently looking into methods of permanent underground storage for CO(2) in an attempt to mitigate this problem. The goal of this work is to develop a process for studying the total carbon content in soils before, during, and after CO(2) injection to ensure that no leakage is occurring or to determine how much is leaking if it is occurring and what effect it will have on the ecosystem between the injection formation and the atmosphere. In this study, we quantitatively determine the total carbon concentration in soil using laser-induced breakdown spectroscopy (LIBS). A soil sample from Starkville, Mississippi, USA was mixed with different amounts of carbon powder, which was used as a calibration for additional carbon in soil. Test samples were prepared by adding different but known amounts of carbon powder to a soil sample and then mixing with polyvinyl alcohol binder before being pressed into pellets. LIBS spectra of the test samples were collected and analyzed to obtain optimized conditions for the measurement of total carbon in soil with LIBS. The total carbon content in the samples was also measured by a carbon analyzer, and the data (average of triplicates) were used as a reference in developing calibration curves for a modified version of the single linear regression model and the multiple linear regression model. The calibration data were then used to determine the total carbon concentration of an unknown sample. This work is intended to be used in the initial development of a miniaturized, field-portable LIBS analyzer for CO(2) leak detection.     

Eudragit S100 coated microsponges for Colon targeting of prednisolone

Context: Microsponge is a novel approach for targeting the drug to the colon for the management of colon ailments such as inflammatory bowel disease.

Objective: Prednisolone loaded microsponges (PLMs) were prepared and coated with Eudragit S 100 (ES) and evaluated for colon-specific drug delivery.

Materials and methods: PLMs were prepared using quasi emulsion solvent diffusion technique using ethyl cellulose, triethylcitrate (1% v/v, plasticizer) and polyvinyl alcohol (Mol. Wt. 72?kDa, emulsifying agent). The developed microsponges were compressed into tablets via direct compression technique using sodium carboxymethyl cellulose (Na CMC) and magnesium stearate as super-disintegrant and lubricant, respectively. The tablets were then coated with ES to provide protection against harsh gastric environment and manifest colon-specific drug release.

Results: PLMs were found to be nano-porous spherical microstructures with size around 35?µm and 86% drug encapsulation efficiency. Finally, they were compressed into tablets which were coated with Eudragit S 100 In vitro drug release from ES coated tablets was carried out at various simulated gastrointestinal fluids i.e. 1?hr in SGF (pH 1.2), 2 to 3?h in SIF (pH 4.6), 4–5?h in SIF (pH 6.8), and 6–24?h in SCF (pH 7.4) and the results showed the biphasic release pattern indicating prolonged release for about 24?h.

Discussion and conclusion: In vitro drug release studies revealed that drug starts releasing after 5?h by the time PLMs may enter into the proximal colon. Hence maximum amount of drug could be released in the colon that may result in reduction in dose and dose frequency as well as side effects of drug as observed with the conventional dosage form of prednisolone.     

Establishment and Development of Torque Metrology in CSIR-NPL for Providing the Traceability in Torque Measurements to User Industries

Torque primary standard machines are established at CSIR-NPL, India to realize the torque scale and to disseminate the same for user industries for providing the traceability in torque measurement. Two torque machines, a primary standard machine comprising of elastic hinge supported load lever with scale pan having an uncertainty of ±0.01 % and a secondary standard machine comprising of an unsupported lever arm with a scale pan suspended by a knife edge having an uncertainty of ±0.05 %, are established. The uncertainty of these machines are estimated theoretically by considering the uncertainty contributions of various input quantities which is also reaffirmed through the inter-comparison carried out on these machines.     

Processing of polyethylene terephthalate fiber reinforcement to improve compatibility with constituents of GFRP nanocomposites

The aim of the present research was to improve the impact strength of epoxy-based glass fiber-reinforced nanocomposites by the addition of polyethylene terephthalate (PET) fibers as reinforcement along with nanoclay. Hybrid nanocomposites containing clay as nano-filler and PET fibers as micro-reinforcement were fabricated. Nanocomposites with 1?phr clay and varying concentrations of PET fibers (1–3?phr) were processed using a vacuum-assisted hand layup. Addition of untreated PET fibers did not improve the impact strength of nanocomposites due to the lack of interaction between the inert PET fibers and other constituents. To improve the interfacial interaction, two different compatibilization procedures for the surface modification of PET fibers were used. In the first procedure, silane treatment of fibers was performed using two separate silane agents. In the second method, maleic anhydride (MAH) grafting was performed in the presence of ultraviolet radiations. Compatibilization of fibers was confirmed with scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) and Fourier transform infrared spectroscopy (FTIR). The results of impact and tensile testing showed an improvement of 19% in the impact strength of nanocomposites at 2?phr silane-treated PET fiber loading without significant loss in tensile strength. Finally, scanning electron micrographs of various nanocomposites were analyzed to correlate with the improved impact strength.     

Basil oil is a promising skin penetration enhancer for transdermal delivery of labetolol hydrochloride

The present work investigates effectiveness of basil oil, a volatile oil containing alcoholic terpenes, as a potential penetration enhancer for improved skin permeation of labetolol hydrochloride (LHCl) with reference to camphor, geraniol, thymol, and clove oil. Saturation solubilities of LHCl were determined in water, vehicle (ethanol:water, 60:40 v/v) and vehicle containing 5% w/v terpenes. Comparable (P > 0.05) saturation solubilities were found suggesting an insignificant increase in LHCl flux across rat skin on account of thermodynamic activity. Permeation of LHCl in vehicle per se and in presence of 5% w/v enhancer was investigated by performing in vitro rat abdominal skin permeation studies using a side-by-side glass diffusion cell. Various parameters viz. steady state flux, permeability coefficient, lag time, partition coefficient, diffusion coefficient, and enhancement ratios (ER) were calculated from the permeation data. Basil oil produced the maximum enhancement (ER = 46.52) over neat vehicle, among all enhancers. Activation energies for LHCl permeation in water, vehicle per se and in presence of 5% w/v basil oil were found to be 23.16, 18.71, and 10.98 kcal/mole, respectively. Lowering of activation energy in presence of basil oil suggests creation of new polar pathways in the skin for enhanced permeation of LHCl. Basil oil is proposed as a promising penetration enhancer for improved transdermal drug delivery of labetolol.     

Chromium(VI) removal from aqueous system using Helianthus annuus (sunflower) stem waste

The objective of this study was to investigate the Cr(VI) removal efficiency of sunflower waste from aqueous system under different process conditions. Two adsorbents were prepared by pre-treating the sunflower stem waste. One adsorbent was prepared by boiling it and second adsorbent was prepared by treating it with formaldehyde. Batch mode experiments were carried out as a function of solution pH, adsorbent dosage, Cr(VI) concentration and contact time. FT-IR spectra and SEMs of the adsorbents were recorded to explore the number and position of functional groups available for the binding of Cr(VI) ions and morphology of the studied adsorbents. The removal of chromium was dependent on the physico-chemical characteristics of the adsorbent, adsorbate concentration and other studied process parameters. Maximum metal removal was observed at pH 2.0. The efficiencies of boiled sunflower stem absorbent and formaldehyde-treated sunflower stem absorbent for the removal of Cr(VI) were 81.7 and 76.5%, respectively for dilute solutions at 4.0g/L adsorbent dose. The applicability of Langmuir, Freundlich and Dubinin-Radushkevich isotherms was also tested. The results revealed that the hexavalent chromium is considerably adsorbed on sunflower stem and it could be an economical method for the removal of hexavalent chromium from aqueous systems.     

A parametric finite element study and an analytical model of particle distributions on post-necking deformation and failure mode in AA5754 aluminum alloy sheets

Finite element analysis of a simplified large particle field, edge constrained plane strain model is used for parametric studies of the influence of particle distributions on post-necking deformation and failure mode in AA5754 aluminum sheets. The models show that the post-necking deformation decreases with volume fraction of particles and fraction of stringers, and increases with interparticle spacing. It is to be noted that a stringer is a string of second phase particles that is frequently observed in continuous strip cast (CC) sheet aluminum alloys. The post-necking deformation initially decreases with the length of stringers, but after a critical stringer length, it increases. An analytical model to estimate the number of stringers which act as initial active damage sources is able to predict a critical stringer length for least post-necking deformation and can serve as a design tool.     

Faster response of NO₂ sensing in graphene-WO₃ nanocomposites

Graphene-based nanocomposites have proven to be very promising materials for gas sensing applications. In this paper, we present a general approach for the preparation of graphene-WO(3) nanocomposites. Graphene-WO(3) nanocomposite thin-layer sensors were prepared by drop coating the dispersed solution onto the alumina substrate. These nanocomposites were used for the detection of NO(2) for the first time. TEM micrographs revealed that WO(3) nanoparticles were well distributed on graphene nanosheets. Three different compositions (0.2, 0.5 and 0.1 wt%) of graphene with WO(3) were used for the gas sensing measurements. It was observed that the sensor response to NO(2) increased nearly three times in the case of graphene-WO(3) nanocomposite layer as compared to a pure WO(3) layer at room temperature. The best response of the graphene-WO(3) nanocomposite was obtained at 250?°C.     

Electronic and optical properties of ultrathin single walled boron nanotubes – An ab initio study

We have employed density functional theory calculations in generalized-gradient approximation to investigate electronic and optical properties of single walled boron nanotubes. We have calculated binding energy per atom, band structure, partial density of states, dielectric function, absorption spectra and loss function for armchair (3, 3), zigzag (5, 0) and chiral (4, 2) nanotubes. Our calculations show that (4, 2) nanotube is highly stable and semiconducting with direct band gap of 0.40 eV followed by armchair (3, 3) and zigzag (5, 0) nanotubes depicting metallic nature. The optical properties of periodic nanotubes were performed for parallel and perpendicular polarized light. It is found that all the three nanotubes are anisotropic in nature and chiral (4, 2) nanotube showing single peak for both absorption spectra as well as loss function irrespective of polarization direction.