Performance Analysis of Light-weight Scattering Coefficient Counter with AURORA 3000 Nephelometer over Delhi

From past many decades, the integrating nephelometers are generally used to measure the aerosol scattering coefficient for ground level at different wavelengths. In recent years, the research focus has been shifted toward the airborne observations using either tethered balloons or drones. For this particular purpose, one needs light-weight instruments which are capable of measuring the aerosol scattering coefficient suitable for airborne activities. Thus, we report the design and development of a light-weight scattering coefficient counter (weight 500 g, 7 '' x 3 '') with high sensitivity. This instrument has been specifically designed and developed for the measurement of aerosol scattering coefficient at 633 nm wavelength. The aerosol scattering coefficient calculation becomes extremely important for modeling aerosol optical/radiative properties. Delhi is one of the regions with high aerosol loadings, so one needs such Light-weight instruments for the aerosol scattering coefficient measurements. At present, this instrument has only been evaluated at ground level. But, before using the developed instrument for airborne observations, there is a strong need for comparison of the instrument against routinely used nephelometers for performance evaluation. Comparisons were performed between the light-weight scattering coefficient counter and high-end AURORA 3000 Nephelometer for two different seasons. For both the seasons, i.e., the monsoon season (July 25-August 24, 2017) and the winter season (February 1-28, 2018), we found a strong correlation (i.e., R-2 = 0.99). However, the highest value of scattering coefficient was found to be 98 +/- 32 Mm(-1) with a mean value of 55 Mm(-1) for the monsoon season, while the same for the winter season was observed to be 270 +/- 108 Mm(-1) with a mean value of 165 Mm(-1). This light-weight instrument could be a potential instrument for aerosol scattering observations, especially for airborne platforms with payload mass limitations

Mechanism of visible-light-driven photocatalytic degradation of endosulfan pesticide by gold nanoparticles

Spherical shaped gold nanoparticles (GNPs) of size around similar to 9 nm were successfully used for photocatalytic degradation of hazardous endosulfan (ES) pesticide. GNPs absorb sunlight at ambient condition in aqueous medium to enhance localized surface plasmon resonance (LSPR) which initiate hydrolysis, oxidation and reduction chemical reactions for the mineralization of ES molecules. Infrared transmittance spectra of GNPs treated ES solutions revealed formation of amorphous carbon and hydrocarbon as final reaction products indicating the nearly complete mineralization of ES as evidenced from their TEM images also. The disappearance of chloro carbon and sulphite functional groups peaks of ES in IR transmittance spectra confirmed their degradation. TEM images also support the optical absorption spectra consisting of inter-band and LSPR bands pertaining to individual and clustered GNPs ensembles. The redshift in LSPR absorption peak positions along minor and major axis of clustered GNPs ensembles is attributed to the change in GNPs polarizability on interaction with the electric component of visible light. The chemical reaction pathway for ES molecule degradation by the photocatalytic GNPs has been proposed in the light of inferences drawn from TEM images, IR transmittance and optical absorption spectra

Influence of defect pairs in Ga-based ordered defect compounds: a hybrid density functional study

In the present paper, density functional theory (DFT) based calculations have been performed to predict the stability, electronic, and optical properties of Ga-rich ordered defect compounds (ODCs). The calculated lattice constants, bulk modulus, their pressure derivatives, and optical constants show good agreement with available experimental data. The hybrid exchange correlations functional have been considered to calculate ground state total energy and energy band gap of the material. The calculated formation energy of ODCs comes smaller than pure CuGaSe2 (CGS). Our calculated optical absorption coefficients indicate that the energy band gap of ODCs can be tuned by changing the number of donor-acceptor defect pairs (2V(cu)(-), + Ga-cu(2+)). The band offset has been calculated to understand the reason of band gap alteration while the number of defect pair changes. Our results may be helpful for other experiments to further improve the performance of ODCs

High-speed, low-bias operated, broadband (Vis-NIR) photodetector based on sputtered Cu2ZnSn(S, Se)(4) (CZTSSe) thin films

Photodetectors have large applications in the current ongoing pandemic. These can be used to study the growth of viruses where depending upon the concentration the light intensity will be reduced. Since the viruses grow very fast therefore a device with very low response time as well as quick recovery will be useful for this study. If the device can be made from the non-toxic materials and sizes are quite small, they can be used for in vitro studies as well. Kesterite Cu2ZnSn(5, Se)(4) (CZTSSe) thin film can be deposited over flexible substrates. The detectivity of even very small area device is very high with ultra-small response and recovery time. The CZTSSe PD exhibited excellent broadband (Vis-NIR) photoresponse, high responsivity of 18.0 mA.W-1, a fast rise time of 82 ms, and a decay time of 97 ms, as well as high detectivity (similar to 10(9) Jones) with favorable self-powered characteristics. This work suggests significant scientific insights for photoconductivity properties of emerging kesterite CZTSSe thin-film materials for broadband, low-cost, high-efficiency next-generation thin-film photodetectors for various optoelectronic applications including diagnostic

Growth and Characterization of MnBi2Te4 Magnetic Topological Insulator

We report successful growth of magnetic topological insulator (MTI) MnBi(2)Te(4)singlecrystalby solid state reaction route via self flux method. The phase formation of MnBi(2)Te(4)singlecrystalis strongly dependent on the heat treatment. MnBi(2)Te(4)is grown in various phases i. e., MnBi4Te7, MnBi6Te10 and MnTe as seen in powder X-ray diffraction (PXRD) of crushed resultant crystal. The Rietveld analysis shows some impurity lines along with the main phase MnBi2Te4. Low temperature (10K) magneto-resistance (MR) in applied magnetic field of up to 6 Tesla exhibited - ve MR below 0.5 Tesla and +ve for higher fields. The studied MnBi2Te4, MTI crystal could be a possible candidate for Quantum Anomalous Hall (QAH) effect. Here we are reporting a newly discovered magnetic topological insulator MnBi(2)Te(4)having non-trivial symmetry as well as strong Spin-Orbit Coupling forQAH effect

Investigation of charge transfer properties in MEHPVV and rGO-AA nanocomposites for Green organic photovoltaic application

The rapid ascension in conjugated polymer-based organic electronic device applications is of highest concern and explored with utmost interest. They own distinct properties such as efficient dissociation in exciton pairs and better charge transfer capabilities that lead to an enhanced separation of exciton at the donor: acceptor interface. Therefore, an appropriate selection of donor and acceptor species is required for the development of an efficient organic solar cell device. In this work, an organic nanocomposite-based system in which conductive polymer MEHPPV poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] acts as an electron donor and green route reduced graphene oxide (rGO) via L-Ascorbic Acid (L-AA) as an acceptor material has been materialised for the photovoltaic energy conversion. The validation of charge-transfer properties in rGO-AA blended with conducting MEHPPV has been investigated using photoluminescence quenching phenomena and UV visible spectroscopy techniques. However, the reduction of GO is confirmed using X-ray diffraction, Raman spectroscopy, and morphology via scanning electron microscopy. The current-voltage characteristics reveal that the charge transfer occurred and an efficiency of 0.084 % has been noticed which confirms the utilisation of rGO-AA as an acceptor material for the development of green optoelectronic devices

Influence of substrate nitridation on properties of GaN nanorods grown on molybdenum foil by laser molecular beam epitaxy

We studied the effect of nitridation condition of Mo foil on the properties of GaN nanorods grown by laser molecular beam epitaxy. It is found that randomly size-distributed three-dimensional GaN islands were grown on bare Mo foil at growth temperature of 700. Upon nitridation of Mo foil with low nitrogen plasma flux, hexagonally-faceted inverse-tapered GaN nanorods were grown whereas tapered GaN nanorods were obtained for Mo foil nitridated under high nitrogen plasma flux. Using wet-chemical etching process, it is deduced that the inverse-tapered GaN nanorods have N-polarity while the tapered GaN nanorods have Ga-polarity. Optical analysis revealed that the inverse-tapered GaN nanorods have prominent near band edge (NBE) emission peak with negligible defect-related peaks whereas tapered GaN nanorods possess yellow luminescence peak along with NBE emission. The control of polarity of GaN nanords on flexible metal foils by tuning pre-nitridation condition is beneficial for futuristic nitride-based flexible opto-electronics devices

Investigations on key aspects of solution growth L-Alanine strontium chloride trihydrate single crystal for non-linear optical and photonic applications

In the modern era materials with high NLO efficiency, better mechanical and thermal properties are on leading edge and highly demanded for their efficient use in optical communication and fibers optics. In the present course of work, authors have grown successfully single crystals of L-alanine strontium chloride trihydrate(LASRT) by slow evaporation solution and slow cooling techniques so as to meet the demand of industries. Structure of the grown crystal with lattice parameters were confirmed by employing powder XRD technique. Mechanical strain present in the lattice is determined as -7.066 x 10(-2) by Williamson-Hall relation. The newly grown crystals were subjected to HRXRD to assess crystal perfection and various types of defects. In this research, quality of the grown crystals is found moderately good. The specimen has better transmission nearly 44% as indicated by UV-Vis spectra. Various remarkable parameters like optical band gap, reflectance, refractive index, extinction coefficient and electrical susceptibility are determined. Some important electronic parameters are calculated by using Claussius-Mossottee relation. Thermal properties were also investigated in detail by subjecting the crystals to TGA/DTA measurements. By photo acoustic analysis, thermal diffusivity (alpha) is found 1.8816 x 10(-6) m(2)/s which indicates large heat bearable capacity of the grown sample. Mechanical stability of LASRT is determined larger than already reported LOMHCl and LLHBr single crystals by Nano-indentation technique. Results for nonlinear optical testing, crystalline perfection and optoelectronic parameters indicate its suitability for laser applications

Integrated graphene quantum dot decorated functionalized nanosheet biosensor for mycotoxin detection

Decoration of graphene quantum dots (GQDs) on molybdenum disulfide (MoS2) nanosheets serves as an active electrode material which enhances the electrochemical performance of the analyte detection system. Herein, ionic surfactant cetyltrimethylammonium bromide (CTAB)-exfoliated MoS2 nanosheets decorated with GQD material are used to construct an electrochemical biosensor for aflatoxin B1 (AFB1) detection. An antibody of AFB1 (aAFB1) was immobilized on the electrophoretically deposited MoS2@GQDs film on the indium tin oxide (ITO)-coated glass surface using a crosslinker for the fabrication of the biosensor. The immunosensing study investigated by the electrochemical method revealed a signal response in the range of 0.1 to 3.0 ng/mL AFB1 concentration with a detection limit of 0.09 ng/mL. Also, electrochemical parameters such as diffusion coefficient and heterogeneous electron transfer (HET) were calculated and found to be 1.67 x 10(-5) cm(2)/s and 2 x 10(-5)cm/s, respectively. The effective conjugation of MoS2@GQDs that provides abundant exposed edge sites, large surface area, improved electrical conductivity, and electrocatalytic activity has led to an excellent biosensing performance with enhanced electrochemical parameters. Validation of the fabricated immunosensor was performed in a spiked maize sample, and a good percentage of recoveries within an acceptable range were obtained (80.2 to 98.3%)

Insights into coarse particle optics based on field evidence of particle morphology, chemical composition and internal structure

Aerosol particles scatter and absorb solar radiation and affect the Earth's radiation budget. The aerosol particles are usually non-spherical in shape and inhomogeneous in chemical composition. For simplicity, these particles are approximated as homogeneous spheres/spheroids in radiative models and in retrieval algorithms of the ground and spaceborne observations. The lack of information on particle morphology (especially shape), chemical composition (that govern their spectral refractive indices) and most importantly internal structure (three dimensional spatial distribution of chemical species) lead to uncertainty in the numerical estimation of their optical and radiative properties. Here, we present a comprehensive assessment of the particles' volumetric composition. The particles were collected from Jaisalmer (arid environment) and Delhi (urban environment) of India and subjected to Focused Ion-Beam (FIB) coupled with Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscope (EDS). Based on analysis of #2 particles from Jaisalmer, particles were observed to be composed of Fe, Ca, C, Al, Cu and Mg rich shell with Si and O rich core as opposed to those of Delhi particles (no #3) which were observed to be with Cu and S rich core and Hg, Ag, C, S and N rich shell. Based on the homogeneous sphere/spheroid assumption, conventional SEM-EDS and FIB-SEM-EDS results, different particle model shapes [single species homogeneous sphere (SP1) and spheroid (SPH1); multiple species homogeneously mixed sphere (SP2) and spheroid (SPH2); and core-shell (CS)] were considered for simulating their respective optical properties; SSA (Single Scattering Albedo) and g (Asymmetry parameter). The effect of internal structure on SSA was found to be prominent in particles having low value of the imaginary part of refractive index (k). While the same was observed to be low (nearly negligible) for the particle with the high value of k. The particles rich in copper are found to have high light absorbing property which causes positive radiative forcing