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A Novel Electrochemical Biosensor Based on Hematite (alpha-Fe2O3) Flowerlike Nanostructures for Sensitive Determination of Formaldehyde Adulteration in Fruit Juices
No full textHigh-performance electrochemical enzymatic biosensor based on flowerlike alpha-Fe2O3 nanostructures was successfully developed for the detection of potential food adulterant, formaldehyde (formalin). The biosensor was found to be highly sensitive (744.15 mu A mg(-1) Lcm(-2)) with linear range of detection (0.01-0.3 mg/L) and showed high shelf-life (9 weeks) and precision (0.73% RSD) with reasonably good reproducibility. The biosensor application in real sample analysis was successfully accomplished using cyclic voltammetry (CV) technique. The developed biosensor exhibited detection limits of 0.02 mg/L and 0.04 mg/L in extracted and commercial orange juice samples, respectively, while 0.03 mg/L in extracted mango juice and 0.05 mg/L in commercial mango juice were obtained. The obtained detection limits are well below the maximum daily dose reference set by Environmental Protection Agency (EPA), USA, for formaldehyde. Biosensor results were found in good agreement with those obtained with HPLC (p < 0.05) and highlight market acceptability with usefulness and effectiveness of the proposed method for food quality and safety evaluation
Anticorrosion and electromagnetic interference shielding behavior of candle soot-based epoxy coating
No full textThis article presents candle soot (CS) as anticorrosion coating material for mild steel (MS) in 3.5 wt % of NaCl solution using potentiodynamic polarization and electrochemical impedance spectroscopy. CS is easily available, low-cost material, and characterized by using X-Ray diffraction (XRD), Raman spectroscopy, UV-vis spectroscopy, Fourier-transform infrared (FTIR), and scanning electron microscopy (SEM). CS is superhydrobhobic in nature that helps to prevent corrosion by repelling water molecules from MS surface. The electrochemical results confirmed the prevention in corrosion process for MS using candle soot-epoxy (CS-EP) based anticorrosion coatings. The CS-based coatings displayed outstanding barrier properties in 3.5 wt % of NaCl solution in comparison to the neat EP coating. Different candle CS-EP coating combinations were tested that exhibited excellent corrosion inhibition performance with highest protection increased up to 98.45% at 0.2 wt % of CS. The surface morphological studies were used to analyze the MS surface conditions in absence and presence of CS-EP coating in 3.5 wt % of NaCl solution. CS-EP admixtures were also tested for their shielding effectiveness in the frequency range of 8.2-12.4 GHz and it has been found that on incorporation of 0.2 wt % of CS in EP resin total shielding effectiveness (SET) increased to -5.3 dB as compared to -0.33 dB for neat EP
Characteristics of gaseous and particulate ammonia and their role in the formation of secondary inorganic particulate matter at Delhi, India
No full textChemical characteristics of ambient ammonia (NH3), other trace gases (NO, NO2, SO2, and HNO3) and ionic species (NH4 (+), SO42-, NO3- and Cl- etc.,) of PM2.5 were estimated from January 2013 to December 2015 at an urban site of Delhi, India to evaluate the role of ambient NH3 in the formation of secondary inorganic aerosols over Delhi. The average mixing ratios of ambient NH3, NO, NO2, SO2 and HNO3 were recorded as 19.6 +/- 3.5 (ppb), 20.4 +/- 6.2 (ppb), 19.7 +/- 5.3 (ppb), 1.7 +/- 0.5 (ppb) and 1.2 +/- 0.3 (ppb), respectively during the entire study period. The mixing ratios of NH3, other trace gases (SO2, NO and NO2 ) and ionic species of PM2.5 were recorded higher during winter season (except HNO3). The result reveals that the increased relative humidity (RH) during winter season plays a major role in the formation of NH4+ aerosol over the observational site of Delhi. The annual average concentration of total water soluble inorganic ionic components (WSIC) in PM2.5 was 69.1 +/- 38.1 mu g m(-3) accounting for similar to 60% of PM2.5 concentration. The secondary aerosol components i.e. NH4+, SO42-, NO3- and Cl- shared the largest part of the total water soluble ions (61%) and PM2.5 concentration (36%). Among the secondary inorganic aerosol components in PM2.5 , SO42- was the most abundant component followed by NO3- and Cl-. Ion balance and molar equivalent ratios indicated that the sufficient amount of NH4+ was available to neutralize SO42-, NO3- and Cl- in the winter season followed by summer and monsoon seasons. The formation of NH4NO3 was higher in winter due to low temperature and high humid conditions that drives the reaction between NH3 and HNO3 in forward direction
Delineating sources of groundwater recharge and carbon in Holocene aquifers of the central Gangetic basin using stable isotopic signatures
No full textStable isotopes of water (delta H-2, delta O-18) and delta C-13(TIC) were used as a tool to trace the recharge processes, natural carbon (organic and inorganic) source and dynamics in the aquifers of the central Gangetic basin, India. Stable isotope (delta H-2, delta O-18) record of groundwater (n = 105) revealed that the groundwater of Piedmont was recharged by meteoric origin before evaporation, while aquifers of the older and younger alluvium were recharged by water that had undergone evaporation loss. River Ganges and its tributaries passing through this area have very little contribution in recharging while ponds play no role in the recharging of adjacent aquifers. The connectivity of shallow aquifers of aquitard formation (comprised of clay/sandy clay with thin patches of fine grey sand), i.e. 25-60 m below ground level (bgl) with the main upper aquifer (at a depth of >120 m bgl) was found to be higher in older and younger alluvium. Negative values of delta C-13(TIC) (median -9.6 parts per thousand; range -13.2 to -5.4 parts per thousand) and high TIC (median 35 mM; range 31-46 mM) coupled with low TOC (median 1.35 mg/L; range 0.99-1.77 mg/L) indicated acceleration in microbial activity in the younger alluvium, especially in the active floodplain of river Ganges and its proximity
Effect of matrix content on the performance of carbon paper as an electrode for PEMFC
No full textPorous conducting carbon fiber-based composite paper is used as an electrode backing in the fuel cell assembly. It not only acts as a channel through which the reactant and product gases pass to and from the bipolar plate and the catalyst site but also helps in the flow of electrons. In order to perform its role efficiently, it should have sufficient strength, high electrical conductivity, and ideal porous structure. Carbon paper has been fabricated, which builds up the required composite properties. Studies have been conducted to optimize the fiber/matrix ratio in the carbon paper, while ensuring the perfect combination of porosity, mechanical strength, and electrical conductivity for an electrode in a proton electrolyte membrane fuel cells. Detail physico-mechanical and electrochemical characterizations further ascertain that the fiber/matrix ratio plays an important role in tuning the composite properties. The polarization curve of the unit proton exchange membrane (PEM) fuel cell (with an effective electrode area 4 cm(2)) shows a peak power density of 916 mW/cm(2) for the sample with fiber/matrix ratio of 65:35, which is almost the same as the commercially available sigracet gas diffusion layer (SGL) carbon paper tested under similar conditions. Further, proportionally enlarging the electrode area to 100 cm(2) shows that the carbon paper not only shows almost repeatable results in a given set up but also scales up
Evaluation of Uncertainty in the Effective Area and Distortion Coefficients of Air Piston Gauge Using Monte Carlo Method
No full textThe fixed number of trials in the Monte Carlo method (FMCM) has been employed for the evaluation of effective area along with their associated uncertainties and distortion coefficients of piston-cylinder (p-c) assembly of the air piston gauge with varying pressures ranging from 6.5 to 360 kPa. The FMCM uncertainty values are compared with the conventional method, i.e., the law of propagation of uncertainty in the experimental range 20-120 kPa using our primary pressure standard, i.e., ultrasonic interferometer manometer. It is observed that the relative uncertainty of the effective area using FMCM (~ 9.5 ppm) is lesser than that of the experimental value (~ 9.7 ppm) using the same parameters responsible for uncertainty measurement which leads to the quality enhancement in the measurement of pressure
Magnetic frustration and spontaneous rotational symmetry breaking in PdCrO2.
Get PDFIn the triangular layered magnet PdCrO2 the intralayer magnetic interactions are strong; however, the lattice structure frustrates interlayer interactions. In spite of this, long-range, 120 degrees antiferromagnetic order condenses at T-N = 38 K. We show here through neutron scattering measurements under in-plane uniaxial stress and in-plane magnetic field that this occurs through a spontaneous breaking of the threefold rotational symmetry of the nonmagnetic lattice, which relieves the interlayer frustration. We also show through resistivity measurements that uniaxial stress can suppress thermal magnetic disorder within the antiferromagnetic phase
Microstructural evolution of high quality AlN grown by PAMBE under different growth conditions
No full textThe morphological evolution of AlN microstructures by varying the growth temperature and Al/N flux ratio on Si (111) substrate via plasma-assisted molecular beam epitaxy has been investigated. The transformations in microstructures of AlN grown along the c-plane were explored as a function of N-2-flow rate, growth temperature and Al-flux. The structural analysis carried out using high resolution X-ray diffraction reveals single crystalline quality with reduced full widths at half maximum value of 15 arcmin corresponding to a screw dislocation density of 8.5 x 10(8) cm(-2). The topographical study of AlN grown by modulating growth conditions revealed an average surface roughness of 6.9 nm. It was exemplified that interplay between higher growth temperature and nitrogen flow rate is desired to prevent condensation of metallic Al on the surface. Also, the AlN pertaining less screw dislocation density leads to lower dark current which can be fruitful for various optoelectronic applications like vacuum-UV photodetectors
Monolayer graphene electrodes as alignment layer for ferroelectric liquid crystal devices
No full textTransparent electrodes and alignment layers are two essential parts of the liquid crystal (LC) cell fabrication. Conventionally, indium tin oxide (ITO) acts as transparent electrode and a polyimide film is used as alignment layer. In present study, both of these are replaced by using a monolayer graphene film deposited on glass substrate. The graphene film used to fabricate LC cell show excellent optical transmittance (similar to 95%) over 450-800 nm range and electrical resistance of 328.77 Omega/square. Moreover, the alignment of FLC mesogens over graphene monolayer is achieved owing to the pi-pi electron stacking between benzene rings of FLC and honeycomb structure of graphene. Polarizing optical microscopy (POM) shows homogeneous planar alignment of filled FLC over graphene under crossed polarizers. The cell is switched between bright and dark states under the application of electric field to demonstrate the working of LC cell. Further, dielectric relaxation spectroscopy is used to measure the dielectric constant and absorption of FLC. This application of graphene would lead to thin and defect-free devices based on LC
Mg-doped ZnO nanostructures for efficient Organic Light Emitting Diode
No full textZnO and Mg-doped ZnO nanostructures have been synthesized by a hydrothermal method for its potential application in Organic Light Emitting Diodes (OLED). Studies have been undertaken for structural as well as optical properties of ZnO after Mg doping with various concentrations. Field Emission Scanning Electron Microscopy with Energy-dispersive X-ray analysis reveals the morphology and chemical composition of nanostructures shows the formation of ZnO rod-like structure which, interestingly, converted into the multi-pod structure with Mg doping. X-ray diffraction reveals the hexagonal phase of the wurtzite structure of ZnO. UV-Visible absorption spectroscopy suggests the exciton characteristic, at room temperature, with band gap variation while Photoluminescence spectra reveal emission in two different spectral regions (ultraviolet and blue). Synthesized materials have been blended with Poly [9, 9-dioctylfluoreny1-2, 7-diyl] (PFO) and prototype OLED has been fabricated using these materials as an emissive layer. An electroluminescence spectrum shows prominent blue emission at 433 nm, 460 nm, and 490 nm at 6 V. Current-Voltage (I-V) characteristics indicate that the OLED device with 10% Mg doping in ZnO is most stable compared to others