654 research outputs found
Sort by
Ultrafast Carrier dynamics of InxGa1-xN nanostructures grown directly on Si(111)
No full textWe show a flux dependence changes in structural, optical and electronic properties of InxGa1-xN nanostructures (NSs) namely nanocolumns (NCs), nanoflakes (NFs) and nanowall network (NWN) grown directly on Si(111) surface. Field emission scanning electron microscopy (FESEM) images were recorded to see morphological changes from NFs to NCs and NWNc etc, while high-resolution X-ray diffraction (HRXRD) ω−2θ scans were used to determine In incorporation. The maximum In incorporation was observed to be 20, 33 and 38% for the sharp transition from NFs to NCs and NWNs, respectively. The charge carrier dynamics of these grown NSs were probed using Ultrafast Femtosecond Transient Absorption Spectroscopy (UFTAS) with excitation at 350 nm pump wavelength. The UFTAS studies show the comparative charge carriers dynamics of the NWS, NCs and NFs. The charge carrier studies show a higher lifetime in NWNs as compare to NCs and NFs. Further, to examine electronic structure and level of degeneracy of these NSs, core-level and valence band spectra were analyzed by X-ray photoelectron spectroscopy (XPS), which manifest the upward band bending ranging from 0.2 eV to 0.4 eV
Groundwater: a regional resource and a regional governance
No full textGroundwater is a valuable renewable resource for human life. The two major threatening issues being faced by groundwater are its depletion and degradation which affect both the quantity and the quality of groundwater. Though scientific output has progressed well ahead in the domain of groundwater, very little has been done with respect to the establishment of the groundwater governance framework. Groundwater is perceived as a widely distributed resource, but it is fundamentally a local entity. The paper presents the groundwater governance framework from the regional perspective of Fatehgarh Sahib district of Punjab, India—an over-exploited groundwater region
Plasmonic stimulated photocatalytic/electrochemical hydrogen evolution from water by (001) faceted and bimetallic loaded titania nanosheets under sunlight irradiation
No full textThis study demonstrates the synthesis of TiO2 nanosheets (TNST) exhibiting high percentage (54%) of exposed (001) facets and decorated with co-deposited gold and platinum nanoparticles (NPs). The as synthesized as well as modified sheets are then investigated for the photo-reduction of water under sunlight irradiation using different alcohols as hole-scavengers. Structural and morphological studies manifest the formation of well-defined sheet structure of TiO2 with average dimensions of 55 nm × 46 nm. The measured d spacing of 0.34 nm and 0.23 nm corresponds to (101) and (001) facets of anatase TiO2. The presence of Au and Pt was confirmed by electron diffraction and X-ray photoelectron spectroscopy. TiO2 nanosheets (TNST's) with 0.4 and 0.75 wt % of Au and Pt (Au0.4/Pt0.75-TNSTs), respectively were found to exhibit higher efficiency. Furthermore, photo-electrochemical (PEC) water splitting studies revealed the increase in photocurrent from 2 mA at 0.5 V to 4.5 mA at 0.65 V for Au0.4/Pt0.75-TNST photoelectrodes, which otherwise was 0.15 mA for the bare TNST photoelectrodes at the same potential. The observed PEC performance was well supported by impedance analysis, wherein Au0.4/Pt0.75-TNSTs (338 Ω) are found to exhibit lower resistance in comparison to bare TNST (737 Ω), which could be due to brilliant photo conductance and interfacial charge transfer properties of Au0.4/Pt0.75-TNSTs. Photocatalytically the Au0.4/Pt0.75-TNST produced ∼143 μmol h1 of H2 gas under direct sunlight irradiation, which is found equivalent to 16.1% apparent quantum efficiency
Structural analysis of graphene oxide/silver nanocomposites: optical properties, electrochemical sensing and photocatalytic activity
No full textIn the present study, graphene oxide/silver (GO/Ag) nanocomposites were synthesized via a facile simple one pot chemical reduction method using ethylene glycol/sodium borohydrate (EG/NaBH4) as solvent and reducing agent. GO was selected as a substrate and stabilizer to prepare GO/Ag nanocomposites. The synthesized GO/Ag nanocomposites were characterized by a series of techniques. Highly monodispersed stable crystalline silver nanoparticles having a face-centered cubic (fcc) phase were confirmed by X-ray powder diffraction (XRD) on GO signature. Scanning electron microscopy images showed that Ag nanoparticles are deposited on the GO sheet with a narrow size distribution. Transmission electron microscopy observations revealed that large numbers of Ag nanoparticles were uniformly distributed on GO sheet and well separated with an average size of 18 nm. Ultraviolet–visible (UV–Vis) spectroscopic results showed the peak of GO and surface plasmon resonance (SPR) of Ag nanoparticles. The SPR property of GO/Ag nanocomposites showed that there was an interaction between Ag nanoparticles and GO sheet. The intensities of the Raman signal of GO/Ag nanocomposites are gradually increased with attachment of Ag nanoparticles i.e. there is surface-enhanced Raman scattering activity. Electrochemical investigations indicated that the nanocomposites possessed an excellent performance for detecting towards 4-nitrophenol. An application of the obtained GO/Ag nanocomposites as a catalyst in the reduction of 4-nitrophenol to 4-aminophenol by NaBH4 was demonstrated. The GO/Ag nanocomposites exhibited high activity and stability for the catalytic reduction of 4-nitrophenol. The prepared GO/Ag nanocomposites act as photo-catalysts
Synthesis and characterization of highly luminescent N-doped carbon quantum dots for metal ion sensing
No full textIn the present study, highly luminescent N-doped carbon quantum dots were synthesized by surface passivation of citric acid using Ethylenediamine. As synthesized NCQDs were characterized using different techniques as TEM, DLS zetasizer, UV-Visible spectroscopy and Photoluminescence spectroscopy. N-CQDs were found to have the approx 6.7 nm diameter and spherical shape as confirmed from TEM. UV-Vis absorption spectra at wavelength 350 nm (λmax = 350 nm) confirmed their formation in the solution. From photoluminescence spectroscopy, it was found these NCQDs emits at wavelength 450 nm ((λex = 350 nm, λem = 450 nm). As-synthesized N-doped CQDs were successfully used for fe3+ ion detection relying on the quenching mechanism
MPA-capped CdSe QD/mercaptoethylamine-capped AuNP nanocomposite-based sensor for instant detection of trinitrotoluene
No full textCdSe quantum dots capped with mercaptopropionic acid (CdSe@MPA QDs) were synthesized by chemical route method. The developed CdSe@MPA QDs were pH optimized for higher emission. Gold nanoparticles in aqueous dispersion medium were synthesized by using sodium citrate as reduction agent and capped with mercaptoethylamine (MEA). Further, AuNP-MEA nanoparticles were conjugated with CdSe@MPAQDs. The “as-synthesized” nanomaterials and their composites were characterized by different analytical techniques like TEM, DLS, FTIR, UV-Vis, and PL spectroscopy. Upon excitation at λex = 400 nm, CdSe@MPA QDs show emission at 540 nm (λem) leading in a good spectral overlap with absorption spectra of AuNPs (λmax = 521 nm). Trinitrotoluene (TNT), being an electron deficient species can easily bind with electron-rich amine group. The amine functionalized GNPs (AuNP@MEA) were used as quenchers for FRET between QDs and GNPs to detect TNT. Using this assay, TNT has been selectively detected up to 21.9 nmol L−1 (LOD). Schematic diagram showing TNT detection based on FRET between gold nanoparticles and quantum dots is also suggested
Gene expression-based biomarkers for discriminating early and late stage of clear cell renal cancer
No full textIn this study, an attempt has been made to identify expression-based gene biomarkers that can discriminate early and late stage of clear cell renal cell carcinoma (ccRCC) patients. We have analyzed the gene expression of 523 samples to identify genes that are differentially expressed in the early and late stage of ccRCC. First, a threshold-based method has been developed, which attained a maximum accuracy of 71.12% with ROC 0.67 using single gene NR3C2. To improve the performance of threshold-based method, we combined two or more genes and achieved maximum accuracy of 70.19% with ROC of 0.74 using eight genes on the validation dataset. These eight genes include four underexpressed (NR3C2, ENAM, DNASE1L3, FRMPD2) and four overexpressed (PLEKHA9, MAP6D1, SMPD4, C11orf73) genes in the late stage of ccRCC. Second, models were developed using state-of-art techniques and achieved maximum accuracy of 72.64% and 0.81 ROC using 64 genes on validation dataset. Similar accuracy was obtained on 38 genes selected from subset of genes, involved in cancer hallmark biological processes. Our analysis further implied a need to develop gender-specific models for stage classification. A web server, CancerCSP, has been developed to predict stage of ccRCC using gene expression data derived from RNAseq experiments
An Accurate and Simple Approach to Detect Eye Centers in Low Resolution Face Images
No full textThis paper introduces a new approach for accurate eye center localization based upon optimized image gradients algorithm. The proposed approach requires pre-fetched feature descriptors to detect the accurate iris centers amongst the possible eye center candidates computed by image gradients over the face image data-set. The results of the proposed algorithm for detecting eye, iris, and iris centers over the test set images of publicly available low resolution and challenging data-set show an accuracy percentage of 98.9, 95.7, and 89.2, respectively. The comparison results obtained by the proposed approach were at par with the state-of-the-art techniques involving complex calculations and training requirements. So, the superior performance and outcome of the proposed approach show the usefulness of optimizing the results of simple image gradients by pre-fetched Scale Invariant Feature Transform feature descriptors in detecting iris centers under unconstrained environments. The proposed approach may be useful for the development of real-time eye gaze tracking application with improved robustness and accuracy
Influence of annealing on dielectric and polarization behavior of PVDF thick films
No full textThe polyvinylidene fluoride (PVDF) thick film has been fabricated by a solution casting method. The fabricated film is subjected to annealing at 50, 90, 100, 110 and 130 °C for 5 h. The effect of annealing on structural, crystalline, dielectric and polarization behavior is investigated. The β-phase PVDF is found to coexist with α-phase for annealing temperature upto 100 °C, after that β-phase is converted to α-phase. The film annealed at 100 °C, exhibits enhanced permittivity, reduced tangent loss and enhanced polarization. The dielectric permittivity and tangent loss of film annealed at 100 °C are ~11 and ~0.025 respectively for the frequency range of 103–105 Hz. The saturation polarization for this film is ~1.27 µC/cm2. The enhanced dielectric permittivity and polarization for the film annealed at 100 °C might be attributed to increase in crystalline α and β-phase interface as well as crystalline amorphous interface. The thick film of PVDF with improved dielectric and polarization behavior could be useful for high power electronics applicatio
Enhancing linearity in I–V characteristics by B/N doping in graphene for communication devices
No full textTo explore communication applications, a study towards achieving linearity in the I–V characteristics through increasing concentrations of Boron (B) / Nitrogen (N) doping on pristine graphene sheet is investigated. Individual B/N doping of 6.25, 12.50, 18.75 and 25% has been done in the same sub lattice using Density Functional Theory (DFT) along with Non Equilibrium Greens Function (NEGF) calculations. The modification in the electronic and transport properties of graphene sheet are also investigated. In comparison to the variation of band gap from 0.35 to 1.183 eV and 0.36 to 1.149 eV for B and N respectively, an insignificant variation in effective mass is reported. Apart from linearity, variation in conductance in doped structures is seen. B doping increases conductivity and yields ON current of 610 µA while N doping gives ON current of 310 µA for maximum doping concentrations. In this work, the sustained carrier mobility and high gain linear characteristics of doped graphene obtained will help to utilise a graphene channel for different communication device applications