Non-covalent functionalization of graphene with poly(diallyl dimethylammonium) chloride: Effect of a non-ionic surfactant

Kaur, P.,Shin, M.S.,Sharma, N.,Kaur, N.,Joshi, A.,Chae, S.R.,Park, J.S.,Kang, M.S.,Sekhon, S.S. Pergamon Press ; Elsevier Science Ltd 2015 International journal of hydrogen energy Vol.40 No.3

Carbon based nanomaterials (carbon nanotubes, graphene etc) containing various hetero atoms are promising metal free catalysts for oxygen reduction reaction in fuel cells. We report the non-covalent functionalization of graphene with poly(diallyl dimethylammonium) chloride (PDDA), a polyelectrolyte containing nitrogen, using a very simple method. The addition of a non-ionic surfactant (Triton X-100) during functionalization has been observed to improve the interactions between graphene and PDDA. An up-shift in the position of G-peak in the Raman spectra, down-shift in the binding energy (B.E.) of N1s peak and an up-shift in the B.E. of C1s peak in XPS spectra have been observed due to an inter-molecular charge-transfer from carbon in graphene to nitrogen in PDDA, which get enhanced in the presence of Triton X-100. Graphene functionalized with PDDA also show good thermal stability. The addition of a non-ionic surfactant enhances the non-covalent functionalization of graphene with PDDA, which is desirable from applications point of view.

Effect of illumination on hydrogenated amorphous silicon thin films doped with chalcogens

Sharma, S.K.,Kumar, K.N.P.,Kang, K.J.,Mehra, R.M. North-Holland 2009 Journal of non-crystalline solids Vol.355 No.31

Hydrogenated amorphous silicon thin films doped with chalcogens (Se or S) were prepared by the decomposition of silane (SiH<SUB>4</SUB>) and H<SUB>2</SUB>Se/H<SUB>2</SUB>S gas mixtures in an RF plasma glow discharge on 7059 corning glass at a substrate temperature 230<SUP>o</SUP>C. The illumination measurements were performed on these samples as a function of doping concentration, temperature and optical density. The activation energy varied with doping concentration and is higher in Se-doped than S-doped a-Si:H thin films due to a low defect density. From intensity versus photoconductivity data, it is observed that the addition of Se and S changes the recombination mechanism from monomolecular at low doping concentration films to bimolecular at higher doping levels. The photosensitivity (σ<SUB>ph</SUB>/σ<SUB>d</SUB>) of a-Si,Se:H thin films decreases as the gas ratio H<SUB>2</SUB>Se/SiH<SUB>4</SUB> increased from 10<SUP>-4</SUP> to 10<SUP>-1</SUP>, while the photosensitivity of a-Si,S:H thin films increases as the gas ratio H<SUB>2</SUB>S/SiH<SUB>4</SUB> increased from 6.8x10<SUP>-7</SUP> to 1.0x10<SUP>-4</SUP>.

Serum and CSF Mineral Profile of Himalayan Yak (Bas grunniens) in their Natural Habitat

Singh, S.P.,Kumar, N.,Sharma, K.B.,Kumar, R. Asian Australasian Association of Animal Productio 1999 Animal Bioscience Vol.12 No.2

Mineral profile of serum and cerebrospinal fluid (CSF) of 15 Himalayan Yak (adult female, n=8; adult male n=4 and young male,n=3) was studied in their natural habitat at an altitude of 3300 meters above mean sea level at Sangla in north western Himalayas. The macro and micro minerals estimated in serum and CSF were; Sodium, Potassium, Calcium and Magnesium and Zinc, Copper and Iron respectively. The values recorded among different Yak groups did not significantly differ from each other except serum iron and haemoglobin which were significantly higher (p<0.05 ) in young male Yaks compared to the adult male and female Yaks. An observation of great significance was considerably higher potassium and lower sodium level in Yaks compared to other bovine species of plains. The serum potassium values in some adult female Yaks were recorded as high as 10.4 mEq/l and the values varied between 6.6 to 9.8 mEq/l in young male Yaks. The serum Sodium values and Na:K ratios in Yak serum ranged between 117.5 to 122.6 mEq/l and 13.7 to 15.3 respectively. The possible relationship of high serum Potassium value with hypoxic conditions and hostile mountain environment has been discussed.

Electrical and mechanical properties of diluted magnetic semiconductor Zn_1-xMn_xS nanocrystalline films

Sreekantha Reddy, D.,Kang, B.,Yu, S.C.,Dwarakanadha Reddy, Y.,Sharma, S.K.,Gunasekhar, K.R.,Rao, K.N.,Sreedhara Reddy, P. Elsevier 2009 Current Applied Physics Vol.9 No.2

Nanostructured Zn<SUB>1-x</SUB>Mn<SUB>x</SUB>S films (0=<x=<0.25) were deposited on glass substrates by simple resistive thermal evaporation technique. All the films were deposited at 300K in a vacuum of 2x10<SUP>-6</SUP>m bar. All the films temperature dependence of resistivity revealed semiconducting behaviour of the samples. Hot probe test revealed that all the samples exhibited n-type conductivity. The nanohardness of the films ranges from 4.7 to 9.9GPa, Young's modulus value ranging 69.7-94.2GPa.

Biogenerated silica nanoparticles synthesized from sticky, red, and brown rice husk ashes by a chemical method

Sankar, S.,Sharma, S.K.,Kaur, N.,Lee, B.,Kim, D.Y.,Lee, S.,Jung, H. Ceramurgica ; Elsevier Science Ltd 2016 CERAMICS INTERNATIONAL Vol.42 No.4

An inexpensive chemical method was used to synthesize biogenic mesoporous silica (m-SiO<SUB>2</SUB>) from rice husk ash (RHA). A comparative study was carried out to produce silica nanoparticles (S-SiO<SUB>2</SUB>, R-SiO<SUB>2</SUB>, and B-SiO<SUB>2</SUB>) from three type of rice husk ashes (sticky, red, and brown). The microstructure of m-SiO<SUB>2</SUB> was dependent on the geographical provenance and the types of RHA. An analysis of the SEM and TEM micrographs reveals that the S-SiO<SUB>2</SUB> nanoparticles had a clustered spherical shape, while R-SiO<SUB>2</SUB> and B-SiO<SUB>2</SUB> nanoparticles were found to be purely spherical. The average crystallite size of S-SiO<SUB>2,</SUB> R-SiO<SUB>2</SUB> and B-SiO<SUB>2</SUB> nanoparticles evaluated from the TEM measurements were observed to be 50, 20 and 10nm, respectively. The XRD pattern of silica nanopowders had an absence of sharp peaks that confirmed the amorphous nature of the material. The Fourier transform infrared (FTIR) spectra of silica nanoparticles showed the symmetric Si-O and O-Si-O stretching bond vibrations at 462, 1088, and 1098cm<SUP>-1</SUP>. The surface area of S-SiO<SUB>2,</SUB> R-SiO<SUB>2</SUB> and B-SiO<SUB>2</SUB> nanopowders was measured to be 7.5513, 201.45, and 247.18m<SUP>2</SUP>g<SUP>-1</SUP>, respectively. The surface area of uniformly-distributed spherical nanoparticles of B-SiO<SUB>2</SUB> was observed the highest, which can be applied for the application of energy storage and drug delivery systems.

Rapid thermal annealing induced modification in structural and electronic structure properties of Ti_0.95Co_0.05O_2@?δ thin films

Rodrigues, E.C.,Sharma, S.K.,de Menezes, A.S.,Chae, K.H.,Gautam, S.,Aljawf, R.N.,Kumar, S. Pergamon Press 2016 Materials research bulletin Vol.83 No.-

Thin film of Ti<SUB>0.95</SUB>Co<SUB>0.05</SUB>O<SUB>2-δ</SUB> was deposited on Si (100) using PLD method and annealed in O<SUB>2</SUB> and N<SUB>2</SUB> environment. Raman spectra confirm that all the films have rutile structure. Surface morphology indicates that the surface roughness and grain size increase with annealing. The electronic structure studied by NEXAFS spectroscopy at O K, Ti L<SUB>3,2</SUB> and Co L<SUB>3,2</SUB>-edges revealed that peak intensities decrease significantly for the film annealed N<SUB>2</SUB> environment. The ligand-field splitting estimated from the energy difference between the t<SUB>2g</SUB> and e<SUB>g</SUB> features in O K-edge spectra were 2.71eV for as-deposited and O<SUB>2</SUB> annealed film, whereas reduced more than double (@?1.32eV) for the film annealed in N<SUB>2</SUB>. Atomic multiplet calculations and experimentally observed NEXAFS spectra at Co L<SUB>3,2</SUB>-edge and Ti L<SUB>3,2</SUB>-edge confirm that Co present in 2+ and Ti in +4 valence state, whereas the multiplet structures of O<SUB>2</SUB> annealed film looks similar to Co metal.

Electrical and mechanical properties of diluted magnetic semiconductor Zn1-xMnxS nanocrystalline films

D. Sreekantha Reddy,강병원,유성초,Y. Dwarakanadha Reddy,S.K. Sharma,K.R. Gunasekhar,K.N. Rao,P. Sreedhara Reddy 한국물리학회 2009 Current Applied Physics Vol.9 No.3

Nanostructured Zn1-xMnxS films (0 ≼ x ≼ 0.25) were deposited on glass substrates by simple resistive thermal evaporation technique. All the films were deposited at 300 K in a vacuum of 2 × 10-6 m bar. All the films temperature dependence of resistivity revealed semiconducting behaviour of the samples. Hot probe test revealed that all the samples exhibited n-type conductivity. The nanohardness of the films ranges from 4.7 to 9.9 GPa, Young’s modulus value ranging 69.7–94.2 GPa.

Relationship of Somatic Cell Count and Mastitis: An Overview

Sharma, N.,Singh, N.K.,Bhadwal, M.S. Asian Australasian Association of Animal Productio 2011 Animal Bioscience Vol.24 No.3

Mastitis is characterized by physical, chemical and bacteriological changes in the milk and pathological changes in the glandular tissue of the udder and affects the quality and quantity of milk. The bacterial contamination of milk from the affected cows render it unfit for human consumption and provides a mechanism of spread of diseases like tuberculosis, sore-throat, Q-fever, brucellosis, leptospirosis etc. and has zoonotic importance. Somatic cell count (SCC) is a useful predictor of intramammary infection (IMI) that includes leucocytes (75%) i.e. neutrophils, macrophages, lymphocytes, erythrocytes and epithelial cells (25%). Leucocytes increase in response to bacterial infection, tissue injury and stress. Somatic cells are protective for the animal body and fight infectious organisms. An elevated SCC in milk has a negative influence on the quality of raw milk. Subclinical mastitis is always related to low milk production, changes to milk consistency (density), reduced possibility of adequate milk processing, low protein and high risk for milk hygiene since it may even contain pathogenic organisms. This review collects and collates relevant publications on the subject.

Effect of the oxidation process on the luminescence of HF-treated porous silicon

S.N.Sharma,R.Banerjee,A.K.Barua 한국물리학회 2003 Current Applied Physics Vol.3 No.2, 3

Porous silicon (PS) films were prepared by lateral anodization of crystalline silicon in HF based solutions at dierent currentdensities. The oxidation mechanism of the HF-treated PS films has been monitored by means of photoluminescence (PL) and. 10 s resulted in the increment ofpolysilane/hydride species on the surface of PS rather than any change in the dimensions of the silicon-crystallites. It has been foundthat HF-treated PS surfaces are relatively stable against oxidation as compared to untreated PS films. Upon oxidation of the HF-treated PS films, the PL intensity initially increases as a result of reduction in crystallite size to exhibit quantum size eects and thendecreases owing to loss of luminescing structures due to over-oxidation of the Si-columns. We infer that the surface passivationemission mechanisms are responsible to explain the luminescence properties of PS.. 2002 Elsevier Science B.V. All rights reserved.

Optically Controlled Silicon MESFET Modeling Considering Diffusion Process

S. N. Chattopadhyay,N. Motoyama,A. Rudra,A. Sharma,S. Sriram,C. B. Overton,P. Pandey 대한전자공학회 2007 Journal of semiconductor technology and science Vol.7 No.3

An analytical model is proposed for an optically controlled Metal Semiconductor Field Effect Transistor (MESFET), known as Optical Field Effect Transistor (OPFET) considering the diffusion fabrication process. The electrical parameters such as threshold voltage, drain-source current, gate capacitances and switching response have been determined for the dark and various illuminated conditions. The Photovoltaic effect due to photogenerated carriers under illumination is shown to modulate the channel cross-section, which in turn significantly changes the threshold voltage, drainsource current, the gate capacitances and the device switching speed. The threshold voltage VT is reduced under optical illumination condition, which leads the device to change the device property from enhancement mode to depletion mode depending on photon impurity flux density. The resulting I-V characteristics show that the drain-source current IDS for different gate-source voltage Vgs is significantly increased with optical illumination for photon flux densities of Φ = 10<SUP>15</SUP> and 10<SUP>17</SUP> /㎠s compared to the dark condition. Further more, the drain-source current as a function of drain-source voltage VDS is evaluated to find the I-V characteristics for various pinch-off voltages VP for optimization of impurity flux density QDiff by diffusion process. The resulting I-V characteristics also show that the diffusion process introduces less process-induced damage compared to ion implantation, which suffers from current reduction due to a large number of defects introduced by the ion implantation process. Further the results show significant increase in gate-source capacitance Cgs and gate-drain capacitance Cgd for optical illuminations, where the photo-induced voltage has a significant role on gate capacitances. The switching time τ of the OPFET device is computed for dark and illumination conditions. The switching time τ is greatly reduced by optical illumination and is also a function of device active layer thickness and corresponding impurity flux density QDiff. Thus it is shown that the diffusion process shows great potential for improvement of optoelectronic devices in quantum efficiency and other performance areas.