Self-activated ‘green’ carbon nanoparticles for symmetric solid-state supercapacitors

Tuning of porosity and surface properties of nanoparticles especially on carbon-based nanomaterials, adopting a ‘greener’ or self-activation synthesis technique for electrical charge storage, is progressing. Herein, we report the self-activation of Teak wood sawdust in a nitrogen atmosphere at different activation temperatures to synthesize carbon nanoparticles. The activated carbon nanoparticles synthesized at 900 °C exhibits a maximum?~?360 m² g^?1 surface area with?~?2 nm average pore size diameter. Five electrolytes viz. KOH, KCl, Na₂SO₄, NaCl, and H₃PO₄ are used for studying the supercapacitance nature of the activated carbon nanoparticles in a 3-electrode configuration. A maximum specific capacitance of?~?208 F g^?1 @ 0.25 A g^?1 is obtained in 1 M KOH as the electrolyte. Two symmetric supercapacitors, aqueous (1 M KOH) and solid-state (PVA/KOH), are fabricated, and their performance difference is compiled. The solid-state symmetric supercapacitor performs in a wider voltage window (1.7 V) with a superior energy density of 27.1 Wh kg^?1 at a power density of 178 W kg^?1.

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Solid-state synthesis and effect of temperature on optical properties of Cu-ZnO, Cu-CdO and CuO nanoparticles

Controlling novel morphologies and developing effective doping strategies are two important tasks for advancing ZnO and CdO based nanomaterials. Modulation of band energies through size control offers new ways to control photoresponse and photoconversion efficiencies of the solar cell. The P-type semiconductors of copper oxide and zinc oxide are an important functional material used for photovoltaic cells. CuO is attractive as a selective solar absorber since it has high solar absorbance and a low thermal emittance. This work describes the synthesis and characterization of semiconducting nanoparticles (ZnO, CuO, CdO, Cu-ZnO, Cu-CdO) via one-step, solid-state reaction in the presence of polyethylene glycol 400.Solid-state mechanochemical processing—which is not only a physical size reduction process in conventional grinding but also a chemical reaction that is mechanically activated at the nanoscale during grinding. The present method is a simple and efficient method for the preparation of nanoparticles with high yield at low cost. The structural and chemical composition of the nanoparticles were analyzed by X-ray diffraction, field emission scanning electron microscopy and energy-dispersive spectrometer (FESEM/EDAX). Optical properties and band gap were studied by UV-vis absorption spectra. XRD data has been concluded that the Cu doping induced the lattice constants to change to some extent. These results have showed that the band gap energy decreases with increase in annealing temperature, which can be attributed to the improvement in crystallinity of the samples. The band gap of the Cu-ZnO and Cu-CdO crystals can be tuned in the range of 3.34-3.28 eV and 2.80-2.21 eV respectively, by the use of dopants.     

Effective face recognition using dual linear collaborative discriminant regression classification algorithm

Multimedia Tools and Applications - In recent decades, face recognition is an attractive and emerging research area in computer vision and pattern recognition applications. Still, facial...     

Atmospheric Fine and Coarse Mode Aerosols at Different Environments of India and the Bay of Bengal During Winter-2014: Implications of a Coordinated Campaign

In this paper, we present mass concentrations of particulate matter [PM_2.5, PM₁₀ size fractions and total suspended particulates (TSP)] measured simultaneously over land stations (Kullu, Patiala, Delhi, Ajmer, Agra, Lucknow, Varanasi, Giridih, Kolkata, Darjeeling, Jorhat, Itanagar, Imphal, Bhubaneswar, and Kadapa), mostly distributed across the Indo-Gangetic plain (IGP) of India as well as in the marine atmosphere over Bay of Bengal (BoB) in the period from 20 January to 3 February, 2014. The main objective of this study was to quantify the continental outflow of particulates (PM_2.5, PM₁₀ and TSP) from IGP and associated regions into the BoB along with low level north-east wind flow during winter monsoon period. The present study provides a glimpse of the aerosol loading over the IGP region. During this campaign, the highest average PM_2.5 (187.8 ± 36.5 µg m^?3, range 125.6–256.2 µg m^?3), PM₁₀ (272.6 ± 102.9 µg m^?3, range 147.6–520.1 µg m^?3) and TSP (325.0 ± 71.5 µg m^?3, range 220.4–536.6 µg m^?3) mass concentrations were recorded at Varanasi, Kolkata and Lucknow over middle and lower IGP regions. The PM_2.5 (average 41.3 ± 11.9 µg m^?3; range 15.0–54.4 µg m^?3), PM₁₀ (average 53.9 ± 18.9 µg m^?3; range 30.1–82.1 µg m^?3) and TSP (average 78.8 ± 29.7 µg m^?3; range 49.1–184.5 µg m^?3) loading over BoB were found to be comparable to land stations and suggests possible continental outflow. Over the continental region, the highest PM_2.5/PM₁₀ ratio was recorded at Delhi (0.87). The PM_2.5/PM₁₀ ratio over BoB (0.77) was found to be quite high and comparable to Varanasi (0.80) and Agra (0.79).     

Magnetic and Structural Investigation of ZnSe Semiconductor Nanoparticles Doped With Isolated and Core‐Concentrated Mn2+ Ions

X‐Ray magnetic circular dichroism (XMCD) experiments on diluted magnetic semiconductor nanocrystals (2–7 nm) are reported in order to study their local electronic structure and magnetic properties. ZnSe nanoparticles containing either single manganese ions (Mn²⁺) distributed in the lattice of the entire particle or a MnSe core in the center are prepared using high temperature approaches. The Mn²⁺ concentration is varied between less than one to several tens of manganese ions per nanocrystal. For all samples it is shown that the Mn²⁺ is exclusively present in the bulk of ZnSe nanoparticles with no evidence for oxidation to higher Mn‐oxidation states. The magnetic ions are highly polarized inside the nanocrystals reaching about 80% of the theoretical value of a pure d⁵ state under identical conditions for the case of isolated manganese ions. Nanocrystals with a MnSe core ZnSe shell structure reach <50% of this value. Thus, their polarization is significantly more hindered, which is due to the significantly enhanced Mn–Mn interactions and a more distorted crystalline lattice. In contrast, no coupling between the manganese centers is observed in the nanoparticles doped samples with low concentrations of Mn²⁺, indicating that these ions are isolated in the bulk of the nanoparticles.     

Mössbauer studies on CuFeSe2

Mössbauer studies at room and liquid nitrogen temperatures were carried out on synthetic, slowly cooled and quenched samples of CuFeSe₂. The iron ion is found to be in the ionic state F³⁺. A small quadrupole splitting is observed due to a slight distortion from tetrahedral symmetry.     

Toxicological assessment of the yeast Rhodotorula gracilis in experimental animals

Rhodotorula gracilis is an oleaginous yeast known to synthesize lipids and carotenoid pigments. In this study, the toxicological evaluation of a locally isolated strain, R. gracilis CFR-1, in freeze-dried form has been studied to assess its safety as a source of natural colorant and nutritional additive in experimental animals. Acute and subacute studies on freeze-dried R. gracilis were conducted on both sexes of albino rats. Acute doses of R. gracilis at 0.5–6.0?g/kg body weight (w/w) did not show any symptoms of toxicity nor mortality of the adult rats. Feeding of low concentrations of R. gracilis at the 0.1–2.0% level (w/w) for 14 weeks did not induce any significant change in food intake and gain in body weight of the experimental rats compared to control animals. There were no significant differences in the absolute and relative weights of vital organs, hematological parameters, macroscopic and microscopic changes in vital organs and serum enzyme levels between the experimental and control groups. The fecal matter of R. gracilis-fed rats did not show any viable cells. The results clearly show that acute and subacute oral feeding of freeze-dried whole cells of R. gracilis for 14 weeks did not produce any toxic effects on male and female rats.