Material Study of Co2CrAl Heusler Alloy Magnetic Thin Film and Co2CrAl/n-Si Schottky Junction Device

The structural, optical, magnetic, and electrical properties of Co2CrAl Heusler alloy magnetic thin films grown on n-type silicon (100) substrate (n-Si) and glass substrate were studied. The films were deposited using DC magnetron sputtering. X-ray diffraction (XRD) analysis confirmed the polycrystalline nature of the films. The effect of grain size on transmittance was investigated. Magnetic measurements revealed the presence of magnetic ordering in the films. Partial densities of states (PDOS) of the Co2CrAl were calculated by density functional theory (DFT) methods using the Vienna Ab initio Simulation Package (VASP). Co2CrAl thin film deposited over a silicon substrate was investigated for I-V characteristics. The electrical behaviour confirmed the existence of a Co2CrAl/n-Si Schottky contact, which suggests a spin injection phenomenon from Co2CrAl to n-Si by tunnelling through the lowered Schottky barrier

pH Dependent surface enhanced Raman study of Phe + Ag Complex and DFT calculations for spectral analysis

Surface enhanced Raman spectra of Phenylalanine (Phe) in Ag colloidal solution have been recorded for Phe solutions of different pH. Spectral line-shape analyses of the enhanced modes, at 1005, 1380 and 1582 cm-1, between pH 4.5 and 10.5, have been carried out. The variation of spectral line-width with pH reveals two possible mechanisms in solution: (i) the fluctuation of pH in microscopic volume in an overall uniform pH solution and/or (ii) the motional narrowing caused by the intermolecular ionic interaction. We suggest that different charge states of the reference molecule are responsible for the observed bond softening with decrease in pH. The observed Raman shift and the Raman activity of the vibrational modes with maximum enhancement have been explained by carrying out DFT calculations.Comment: 17 pages, 5 figure

Synthesis, characterizations and antimicrobial activities of well dispersed ultra-long CdO nanowires

We present a simple, efficient, low cost and template free method for preparation of well dispersed ultra-long (1 μm) CdO nanowires. The CdO nanowires were characterized by x-ray diffraction (XRD), Transmission electron microscopy (TEM), UV-visible spectroscopy and Raman measurements. The direct and indirect band gaps were calculated to be 3.5 eV and 2.6 eV, respectively. In the Raman spectra only second order features were observed. The CdO nanowires were used to study antimicrobial activities against B.subtilis and E.coli microbes. It shows antimicrobial activity against B.subtilis and E.coli. However, the antimicrobial activities are better against B.subtilis than that of E.coli

Gas phase structural stability of neutral and zwitterionic forms of alanine in presence of (H2O)n=1–7 clusters : a density functional theory study

In the present contribution we have examined the gas phase structural stability of zwitterionic alanine (ZAla) relative to the stability of neutral alanine (Ala) in presence of water clusters of size n = 1–7 using Density Functional Theory (DFT) calculations. The gas phase structural energy, and thermodynamical parameters of Ala–(H2O)n=1–7 and ZAla–(H2O)n=2–7 complexes are calculated at B3LYP/6-311++G(d,p) level of theory. We do not get stable structure of ZAla and ZAla + (H2O) in gas phase. This implies that the hydrogen bonding with one water molecule does not produce stable structure of ZAla. However, we found the existence of stable structure of ZAla–(H2O)2 complex in gas phase. This essentially means that at least two water molecules are required to produce stable structure of ZAla in gas phase. Further, we also observed that the Ala–(H2O)2 is relatively more stable than that of ZAla–(H2O)2. The optimized energy of Ala–(H2O)3 and ZAla–(H2O)3 complexes is found to be almost same and thus these two complexes are said to be isoenergetic. The ZAla–(H2O)n complex is found to be structurally as well as thermodynamically more stable than that of Ala–(H2O)n for n ⩾ 4. It indicates that the possibility of finding the ZAla–(H2O)n complex is larger than that of Ala–(H2O)n for n ⩾ 4 in gas phase. The above observations are also well supported by the thermodynamical parameters such as: Gibbs energy, enthalpy and entropy of the complexes

Un-catalyzed peptide bond formation between two monomers of glycine, alanine, serine, threonine, and aspartic acid in gas phase: a density functional theory study

In the present report, un-catalyzed peptide bond formation between two monomers of glycine (Gly), alanine (Ala), serine (Ser), threonine (Thr), and aspartic acid (Asp) has been investigated in gas phase via two steps reaction mechanism and concerted mechanism at B3LYP/6-31G(d,p) and M062X/6-31G(d,p) level of theories. The peptide bond is formed through a nucleophilic reaction via transition states, TS1 and TS2 in stepwise mechanism. The TS1 reveals formation of a new C-N bond while TS2 illustrate the formation of C=O bond. In case of concerted mechanism, C-N bond is formed by a single four-centre transition state (TS3). The energy barrier is used to explain the involvement of energy at each step of the reaction. The energy barrier (20–48 kcal/mol) is required for the transformation of reactant state R1 to TS1 state and intermediate state I1 to TS2 state. The large value of energy barrier is explained in terms of distortion and interaction energies for stepwise mechanism. The energy barrier of TS3 in concerted mechanism is very close to the energy barrier of the first transition state (TS1) of the stepwise mechanism for the formation of Gly-Gly and Ala-Ala di- peptide. However, in case of Ser-Ser, Thr-Thr and Asp-Asp di-peptide, the energy barrier of TS3 is relatively high than that of the energy barrier of TS1 calculated at B3LYP/6-31G(d,p) and M062X/6-31G(d,p) level of theories. In both the mechanisms, the value of energy barrier calculated at B3LYP/6-31G(d,p) level of theory is greater than that of the value calculated at M062X/6-31G(d,p) level of theory

Probing self-associated structures of the solute molecule, acrylonitrile, the solvent molecule 2C1-phenol and their binary complexes via concentration-dependent Raman study and DFT calculation

Raman study of CN-stretching mode of acrylonitrile and ring-breathing mode of 2Cl-phenol was made in the binary mixture of (acrylonitrile + 2Cl-phenol) at different molar ratios of the two components. Raman spectra were recorded in the different spectral regions, 990–1070 cm−1 and 2170–2300 cm−1. Ring-breathing mode of 2Cl-phenol exhibited two components, which were attributed to the neat and self-associated dimer of 2Cl-phenol molecules. The self-associated structure of the dimer was obtained by geometry optimization. Other structures, which were calculated, include self-associated structure of acrylonitrile and the hydrogen-bonded complex of (acrylonitrile + 2Cl-phenol). All the geometry optimizations were made using density functional theory (DFT) and B3LYP functional employing the 6–31 + G(d,p) basis set. The variations of the linewidth and the peak position with concentration are explained on the basis of a model, which includes both the effect of concentration fluctuation in a microscopic volume and the influence of concentration-dependent microviscosity based on a model proposed recently by our grou

Surface-enhanced Raman measurements and DFT calculations for L-tryptophan of varying pH in silver sol

The interaction of L‐tryptophan (Trp) with silver colloids was investigated at between pH values of 6.11 and 10.6 of the sol. The measurements of surface‐enhanced Raman bands of Trp in the colloidal solution indicate the evolution of interaction between the metal particles and the molecules with increasing pH values for the sol. The experimental observations were explained using the estimated atomic charge distribution in the zwitterionic and anionic forms of the residue, obtained by density functional theory calculations. The variation in the ratio of the spectral intensities of the Fermi resonance bands with the pH reflects the effect of the colloidal environment on Trp. The results obtained can be used as a marker for describing the nature of the interaction of silver colloids with the specific terminus of the residue, at varying pH environments

Synthesis of well–dispersed silver nanorods of different aspect ratios and their antimicrobial properties against gram positive and negative bacterial strains

In the present contribution, we describe the synthesis of highly dispersed silver nanorods (NRs) of different aspect ratios using a chemical route. The shape and size of the synthesized NRs were characterized by Transmission Electron Microscopy (TEM) and UV-visible spectroscopy. Longitudinal and transverse absorptions bands confirm the rod type structure. The experimentally recorded UV-visible spectra of NRs solutions were fitted by using an expression of the extinction coefficient for rod like nano structures under the dipole approximation. Simulated and experimentally observed UV-visible spectra were compared to determine the aspect ratios (R) of NRs. The average values of R for NR1, NR2 and NR3 solutions are estimated to be 3.0 ± 0.1, 1.8 ± 0.1 and 1.2 ± 0.1, respectively. These values are in good agreement with those obtained by TEM micrographs. The silver NRs of known aspect ratios are used to study antimicrobial activities against B. subtilis (gram positive) and E. coli (gram negative) microbes. We observed that the NRs of intermediate aspect ratio (R = 1.8) have greater antimicrobial effect against both, B. subtilis (gram positive) and E. coli (gram negative). The NRs of aspect ratio, R = 3.0 has better antimicrobial activities against gram positive than on the gram negative

Tailoring of enhanced interfacial polarization in WO3_3 nanorods grown over reduced graphene oxide synthesized by a one-step hydrothermal method

In the present report, well-defined WO3 nanorods (NRs) and a rGO–WO$_3$ composite were successfully synthesized using a one-pot hydrothermal method. The crystal phase, structural morphology, shape, and size of the as-synthesized samples were studied using X-ray diffraction (XRD) and transmission electron microscopy (TEM) measurements. The optical properties of the synthesized samples were investigated by Raman, ultraviolet-visible (UV-Vis) and photoluminescence (PL) spectroscopy. Raman spectroscopy and TEM results validate the formation of WO$_3$ (NRs) on the rGO sheet. The value of the dielectric constant (ε′) of WO3 NRs and rGO–WO$_3$ composite is decreased with an increase in frequency. At low frequency (2.5 to 3.5 Hz), the value of ε′ for the rGO–WO3 composite is greater than that of pure WO$_3$ NRs. This could be due to the fact that the induced charges follow the ac signal. However, at higher frequency (3.4 to 6.0), the value of ε′ for the rGO–WO$_3$ composite is less compared to that of the pure WO3 NRs. The overall decrease in the value of ε′ could be due to the occurrence of a polarization process at the interface of the rGO sheet and WO3 NRs. Enhanced interfacial polarization in the rGO–WO$_3$ composite is observed, which may be attributed to the presence of polar functional groups on the rGO sheet. These functional groups trap charge carriers at the interface, resulting in an enhancement of the interfacial polarization. The value of the dielectric modulus is also calculated to further confirm this enhancement. The values of the ac conductivity of the WO$_3$ NRs and rGO–WO$_3$ composite were calculated as a function of the frequency. The greater value of the ac conductivity in the rGO–WO$_3$ composite compared to that of the WO$_3$ NRs confirms the restoration of the sp:$^{++}$ network during the in situ synthesis of the rGO–WO$_3$ composite, which is well supported by the results obtained by Raman spectroscopy

Controlled synthesis and magnetic properties of monodispersed ceria nanoparticles

In the present study, monodispersed CeO2 nanoparticles (NPs) of size 8.5 ± 1.0, 11.4 ± 1.0 and 15.4 ± 1.0 nm were synthesized using the sol-gel method. Size-dependent structural, optical and magnetic properties of as-prepared samples were investigated by X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), high resolution transmission electron microscopy (HR-TEM), ultra-violet visible (UV-VIS) spectroscopy, Raman spectroscopy and vibrating sample magnetometer (VSM) measurements. The value of optical band gap is calculated for each particle size. The decrease in the value of optical band gap with increase of particle size may be attributed to the quantum confinement, which causes to produce localized states created by the oxygen vacancies due to the conversion of Ce4+ into Ce3+ at higher calcination temperature. The Raman spectra showed a peak at ∼461 cm-1 for the particle size 8.5 nm, which is attributed to the 1LO phonon mode. The shift in the Raman peak could be due to lattice strain developed due to variation in particle size. Weak ferromagnetism at room temperature is observed for each particle size. The values of saturation magnetization (Ms), coercivity (Hc) and retentivity (Mr) are increased with increase of particle size. The increase of Ms and Mr for larger particle size may be explained by increase of density of oxygen vacancies at higher calcination temperature. The latter causes high concentrations of Ce3+ ions activate more coupling between the individual magnetic moments of the Ce ions, leading to an increase of Ms value with the particle size. Moreover, the oxygen vacancies may also produce magnetic moment by polarizing spins of f electrons of cerium (Ce) ions located around oxygen vacancies, which causes ferromagnetism in pure CeO2 samples