Journals
2018 EN
Juluri Raghavendra Rao · Ravulapalli Sathyavathi · Vadavlli Saikiran
+1 more
Embedded silver nanostructures with different shapes and sizes are grown in Si substrates by chemical vapor deposition (CVD) method. Systematic study of their surface‐enhanced Raman properties is performed. Influence of shape, size, and coverage of the nanoparticles on the average enhancement factors is calculated with the help of standard analyte molecules viz. crystal violet and Rhodamine 6G to optimize the substrates for future sensing applications.
Journals
2018 EN
Bhat Usha · Singh Rajendra · Vishal Badri
+4 more
Van der Waals heterostructures of (TMD L = 1 /BN L = 1–4 /TMD L = 1/ BN L = 1–4 ), [TMD = MoS 2 , WS 2 , and ReS 2 ] are grown on c ‐plane sapphire substrate by pulsed laser deposition (PLD) under slow kinetic condition. The heterostructure systems show strong emission around 2.3 eV and subsidiary peaks around 2.8, 1.9, 1.7, and 1.5 eV. BN and transition metal dichalcogenides (TMDs) form type‐I heterojunction and the emission peaks observed are explained in terms of various band to band recombination processes and considering relative orientation of Brillouin zones. The emission peak around 2.3 eV is promising for solar and photovoltaic applications. The observation is almost similar for three different heterostructure systems.
Journals
2018 EN
Sahu Lokesh K. · Tripathi Nidhi · Sheel Varun
+4 more
The present study investigates the impact of tropical cyclone (TC) Nilam on the vertical distribution of carbon monoxide (CO) over Chennai in southern India. Measurements of OZone and water vapour by Airbus In‐service airCraft (MOZAIC) profiles of CO measured during October–November 2012 were analysed. The vertical profiles of CO on 15 October and 2 November were influenced by convective motions with a significant decrease in outgoing long‐wave radiation (OLR) compared to that on normal days of observations. The near‐surface mixing ratios of CO (185 ± 24 ppbv) in convectively influenced conditions were much lower than those measured during normal days (>210 ppbv). The occurrence of minimum CO values at altitudes of 4–6 km coincided with the lowest lapse rate (LR) value of 4–5 °C/km. The uplift of surface air masses led to a large increase in the CO mixing ratio in the free troposphere. The differences in CO between the lower and free troposphere were relatively small (40–50 ppbv) and large (90–100 ppbv) during convective and normal days, respectively. In the lower troposphere, elevated values of CO (>250 ppbv) were measured for lighter wind speeds from the north, while lower values (<150 ppbv) were measured for strong winds from the western sectors. The Model for OZone And Related chemical Tracers (MOZART‐4) and Chemistry Climate Model 2 (CCM2) simulations did not capture the detailed features of the CO profiles. For cyclone‐influenced measurements in the lower troposphere, MOZART‐4 underestimated the CO values by approximately 13%, but CCM2 overestimated the CO values by 70%. In the upper troposphere, MOZART‐4 and CCM2 underestimated the observations by 6–8% and 12–22%, respectively. The mixing scheme of the model and simulated concentrations seem to be the key causes of disagreements. However, the performances of both the MOZART‐4 and CCM2 simulations were better for convection‐free normal days.
Journals
2018 EN
Sahu Pooja · Ali Sk. Musharaf
The structural and flow characteristics of fluids within carbon nanotube (CNT) is dictated by the interaction of fluid molecules within the nanocavity of CNT. Therefore, in the present study, dispersion corrected density functional theory has been used to investigate the structure and interaction of polar and nonpolar molecules within CNT. The present study shows that there is profound effect on the interaction due to dispersion. The interaction energy of the confined water was found to be reduced with increasing distance of the water molecule from the wall of the CNT. The water is preferentially adsorbed over methane due to stronger interaction with CNT over methane. Further, water is preferentially adsorbed over methanol molecule when interaction is calculated without dispersion but after inclusion of dispersion interaction, the calculated results show that the methanol–CNT interaction is stronger than that of water molecule and hence preferentially adsorbed within the CNT as revealed from MD simulation. The present calculation reveals that that the effect of CNT confinement on the IR spectra of the single file water is quite considerable compared to the IR spectra of tetrahedral bulk water cluster. Therefore, the present results might be useful for the separation of polar molecule from nonpolar molecule during fabrication of CNT‐based filter and purification system.
Journals
2018 EN
Srinu Akula · Peera Shaik Gouse · Parthiban Velayutham
+2 more
This paper describes the synthesis of low cost electrocatalyst for oxygen reduction reaction (ORR) from spent coffee grounds (SCGs) through heteroatom engineering and simultaneous co‐doping of N and P. The co‐doping of N and P to coffee carbon (N−P/CC) brings maximum defect sites in the catalyst which are favourable for ORR in relation to the individual heteroatom doped catalyst. Microscopic analysis confirms that N−P co‐doped coffee carbon (N−P/CC) undergoes slight structural changes by altering its porosity as well as surface area. Electrochemical studies confirm that, N−P/CC has superior catalytic activity with no effect to CO which makes it highly desirable as a metal‐free electrocatalyst for ORR. The developed catalyst is subjected to 10,000 repeated potential cycles in alkaline media and is found only ∼30 mV loss in its E 1/2 potential, while the drop in E 1/2 is about ∼180 mV from its original value even after 1000 potential cycles for the commercial Pt/C catalyst. XPS analysis for N−P/CC shows the presence of active pyridinic‐N, graphitic‐N species and active P−C and P−O bonds. Co‐existence of all these species induces maximum polarization of C−C bonds in the carbon matrix and synergistically enhances the ORR behaviour in alkaline medium.
Journals
2018 EN
Sahoo Smruti R. · Sahu Sridhar · Sharma Sagar
We present a detailed theoretical study of the structural, charge transport, and optical properties of three indolocarbazole derivatives, viz., 11, 12‐Dihydroindolo[2, 3‐a]carbazole (DIC), 5, 10‐dimethyl‐5,10‐dihydrobenzo[a]indolo[2, 3‐c]carbazole (DMDBIC), and 2,11‐dimethoxydibenzo[2, 3:5,6]pyrrolizino[1, 7‐bc]indolo[1, 2,3‐lm]carbazole (DMDPIC). DFT calculations along with previously reported x‐ray crystal structures reveal that the studied compounds are planar and do not undergo significant changes in structure upon oxidation or reduction. The maximum hole anisotropic charge mobilities for DIC was found to be 0.338 cm 2 V −1 s −1 at Φ =175.89° and 355.81° and the maximum electron mobility was 0.181 cm 2 V −1 s −1 at Φ =85.94° and 265.85°. For DMDBIC, the predicted maximum anisotropic hole, and electron mobility was 0.501 cm 2 V −1 s −1 and 0.775 cm 2 V −1 s −1 , respectively at Φ =56.72° and 236.63°, while for DMDPIC the predicted maximum anisotropic hole and electron mobility as 1.586 cm 2 V −1 s −1 and 0.594 cm 2 V −1 s −1 , respectively at Φ =0° and 180.0°. The calculated mobilities show that these compounds may be suitable candidates as a p‐type organic semiconductor with better stability than acene compounds.
Journals
2018 EN
Das Subrata · Sahu Amrita · Joshi Mayank
+4 more
In this work, we present the synthesis and structural characterization of a new Zn(II)‐Schiff base complex, [Zn( L )(H 2 O)] ( 1 ), [ L = N,N′ ‐bis(3‐methoxysalicylidene)‐1,3‐diamino‐2‐propanol]. Single crystal X‐ray structural analysis reveals that 1 crystallizes in monoclinic system with P 2 1 /c space group. The compound shows good photo‐luminescence property in methanol medium. This Zn(II) complex has been evaluated as a catalytic system in the catalytic oxidation of 3,5‐di‐ tert ‐butylcatechol (DTBC) in methanol. The Zn(II) complex displays good catecholase like activity with significant turn over, k cat (h –1 )=7.99×10 2 in methanol under aerobic condition. Very interestingly, we are able to isolate the oxidation product as 3,5‐di‐ tert ‐butylquinone ( 2 ) in association with the substrate in the form of a single crystal. Electron paramagnetic resonance (EPR), electron spray ionization (ESI) mass and 1 H nuclear magnetic resonance (NMR) spectral analyses of the reaction mixture between Zn(II) complex and DTBC recommend that the course of catalysis proceeds through substrate‐catalyst adduct formation & confirm the presence of radical pathways in favour of oxidation products. The computation studies have been executed with density functional theory and all experimental observations are well rationalised with extensive theoretical calculations. Being a redox inactive metal ion, catalytic oxidation of DTBC by Zn(II) complexes will always be a remarkable example in the scientific community.
Journals
2018 EN
Kumari Rinki · Kumar Sahu Sumanta
The synthesis of highly fluorescent longer wavelength emissive carbon quantum dots (CQDs) is still a great challenge as well as an important issue, hindering its application in white light emitting diode (WLED). Herein, we have demonstrated a simple one‐pot solvothermal route for the synthesis of nitrogen and sulphur co‐doped CQDs using pyromellitic acid (PA), diethylenetriamine (DETA) and thiourea. At the specific molar ratio of the precursors, the orange color emissive CQDs (O‐CQDs) are synthesized and possess longer wavelength emission (611 nm). Additionally, O‐CQDs exhibits temperature and pH dependent photoluminescence (PL) properties. The O‐CQDs shows color correlated temperature (CCT) of 1745 K with high color purity of 98%. Simultaneously, as‐synthesized nitrogen and sulphur co‐doped CQDs shows concentration‐dependent PL properties, which display not only the brightness with stable orange color but also possess range of multicolour emission at different PL excitation. Solid host matrix of O‐CQDs is fabricated with poly‐(methyl methacrylate) (PMMA) chloroform solution and orange emissive property is investigated by wrapping the film over LED (InGaN) bulb. These studies will open up new opportunities to explore the tunable optical properties of carbon quantum dots and its applications in WLED devices.
Journals
2018 EN
Sahu Puspanjali · Prusty Gyanaranjan · Guria Amit K.
+1 more
For efficient charge separations, multimaterial hetero‐nanostructures are being extensively studied as photocatalysts. While materials with one heterojunction are widely established, the chemistry of formation of multijunction heterostructures is not explored. This needs a more sophisticated approach and modulations. To achieve these, a generic multistep seed mediated growth following controlled ion diffusion and ion exchange is reported which successfully leads to triple‐material hetero‐nanostructures with bimetallic‐binary alloy‐binary/ternary semiconductors arrangements. Ag 2 S nanocrystals are used as primary seeds for obtaining AuAg‐AuAgS bimetallic‐binary alloyed metal–semiconductor heterostructures via partial reduction of Ag(I) using Au(III) ions. These are again explored as secondary seeds for obtaining a series of triple‐materials heterostructures, AuAg‐AuAgS‐CdS (or ZnS or AgInS 2 ), with introduction of different divalent and trivalent ions. Chemistry of each step of the gold ion–induced changes in the rate of diffusion and/or ion exchanges are investigated and the formation mechanism for these nearly monodisperse triple material heterostructures are proposed. Reactions without gold are also performed, and the change in the reaction chemistry and growth mechanism in presence of Au is also discussed.
Journals
2018 EN
Kumar Pramod · Satyam Abhigyan · Cigognini Daniela
+2 more
Development of implantable devices based on the principles of in vitro organogenesis has been hindered due to the prolonged time required to develop an implantable device. Herein we assessed the influence of serum concentration (0.5% and 10%), oxygen tension (0.5%, 2% and 20%) and macromolecular crowding (75 μg/ml carrageenan) in extracellular matrix deposition in human corneal fibroblast culture (3, 7 and 14 days). The highest extracellular matrix deposition was observed after 14 days in culture at 0.5% serum, 2% oxygen tension and 75 μg/ml carrageenan. These data indicate that low oxygen tension coupled with macromolecular crowding significantly accelerate the development of scaffold‐free tissue‐like modules. Copyright © 2016 John Wiley & Sons, Ltd.