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This study presents a low-cost thyristor-controlled LC compensator scheme for the improvement of overall power quality in the distribution system. The parameters of the compensator have been designed and optimal triggering angles for thyristor switching have been obtained for reducing the unbalanced condition and harmonic injection at a high power factor. Compared to the traditional static VAr compensator schemes, the proposed technique can significantly reduce the harmonic injection into the system. The particle swarm optimization technique has been applied to compute the optimal triggering angles, and different aspects of the power quality factor have been assessed through rigorous simulations. Power quality assessment has been further validated through an experimental setup in the laboratory. Finally, a comparison of the proposed scheme with other similar schemes has been carried out to highlight its efficacy. [ABSTRACT FROM AUTHOR]

Biosurfactants are emerging as a revolutionary substitute for chemical surfactants in various industrial sectors due to their lower toxicity, biodegradable, and environmentally friendly nature. Robust surface activity properties and high emulsification of biosurfactants make them feasible for diverse applications in food industries, such as bakeries, meat and fish processing, heavy metal removal from vegetables, salad dressings, etc. Given the eco-friendliness and safety of biosurfactants, this review focuses on the latest developments in their use in the food business. Nevertheless, it is noteworthy that biosurfactants are not competitively priced with commercial surfactants; consequently, several unique challenges, including the requirement for costly raw substrates and labor-intensive downstream processing, must be addressed to enable the widespread industrial use of biosurfactants. This review recommends further in-depth studies using less expensive, environment-friendly substrates and utilizing state-of-the-art technologies such as genetic engineering and nanotechnologies for biosurfactant production that can overcome the barrier of poor yield and expensive biosurfactant. [ABSTRACT FROM AUTHOR]

With more widespread applications of nanotechnology, heat dissipation in nanoscale devices is becoming a critical issue. We study the thermal response of wafer-scale hexagonal boron nitride (hBN) layers, which find potential applications as ideal substrates in two dimensional devices. Sapphire-supported thin hBN films, 2′′ in size and of different thicknesses, were grown using metalorganic vapour phase epitaxy. These large-scale films exhibit wrinkles defects and grain boundaries over their entire area. The shift of phonon mode with temperature is analysed by considering the cumulative contribution of anharmonic phonon decay along with lattice thermal expansion, defect, and strain modulation. The study demonstrates that during heat treatment the strain evolution plays a dominating role in governing the characteristics of the wrinkled thinner films. Interestingly we find that both defects and strain determine the spectral line-width of these wafer-scale films. To the end, from Raman line-width, the changes in phonon lifetime in delaminated and as-grown films is estimated. The results suggest the possibility of a reduction in thermal transport in these wafer-scale films compared to their bulk counterpart. [ABSTRACT FROM AUTHOR]

Presents a study on laser-induced suppression of photocrystallization rate in amorphous selenium films. Methodology used to conduct study; Indication of findings; Discussion on results.

In this article, we compare the excitation wavelength dependence of the polarization anisotropy (ρ) of an internal field induced Raman scattering signal in individual bare InAs and InAs/GaSb core-shell nanowires. The measured value of ρ of the Raman scattering intensity for InAs/GaSb core-shell nanowires has a minimum at ∼500 nm, while for the bare InAs nanowire, the value of ρ monotonically increases over the same range of wavelengths. We have modeled the scattering intensities of both systems by considering the joint role of Raman tensor components and confinement of electromagnetic radiation inside the nanowire at two orthogonal polarization configurations of the electromagnetic radiation. The theoretical results allow us to understand that the observed behavior of ρ is related to the nanowire geometry and to the difference in the wavelength dependence of the dielectric constants of InAs and GaSb. This work shows the possibility of manipulating the polarization anisotropy by selecting suitable diameters and materials for the core and the shell of the nanowire. We also report a six-fold increase in Raman scattering intensity due to the GaSb shell on InAs nanowires. [ABSTRACT FROM AUTHOR]

We study band alignment in wurtzite/zinc-blende polytype InAs heterostructured nanowires using temperaturedependent resonance Raman measurements. Nanowires having two different wurtzite fractions are investigated. Using visible excitation wavelengths in resonance Raman measurements, we probe the electronic band alignment of these semiconductor nanowires near a high-symmetry point of the Brillouin zone (E1 gap). The strain in the crystal structure, as revealed from the shift of the phonon mode, explains the observed band alignment at the wurtzite/zinc-blende interface. Our experimental results are further supported by electronic-structure calculations for such periodic heterostructured interface. [ABSTRACT FROM AUTHOR]

We demonstrate a non-monotonic evolution of in-plane thermal conductivity of large-area hexagonal boron nitride films with thickness. Wrinkles and defects/impurities are present in these films. Raman spectroscopy, an optothermal non-contact technique, is employed to probe the temperature and laser power dependence property of the Raman active E2ghigh phonon mode, which, in turn, is used to estimate the rise in the temperature of the films under different laser powers. As the conventional Fourier law of heat diffusion cannot be directly employed analytically to evaluate the thermal conductivity of these films with defects and wrinkles, finite-element modeling is used instead. In the model, average heat resistance is used to incorporate an overall near-surface defect structure, and Voronoi cells with contact resistance at the cell boundaries are constructed to mimic the wrinkled domains. The effective in-plane thermal conductivity is estimated to be 87, 55, and 117 W/m K for the 2, 10, and 30 nm-thick films, respectively. We also present a quantitative estimation of the thermal resistance by defects and wrinkles individually to the heat flow. Our study reveals that the defects/impurities render a much higher resistance to heat transfer in the films than wrinkles. [ABSTRACT FROM AUTHOR]

Abstract: An internal field induced resonant intensity enhancement of Raman scattering of phonon excitations in InAs nanowires is reported. The experimental observation is in good agreement with the simulated results for the scattering of light under varying incident wavelengths, originating from the enhanced internal electric field in an infinite dielectric cylinder. Our analysis demonstrates the combined effect of the first higher lying direct band gap energy (E 1) and the refractive index of the InAs nanowires in the internal field induced Raman scattering. Furthermore, the difference in the relative contribution of electro-optic effect and deformation potential in Raman scattering of nanowires and bulk InAs over a range of excitation energies is discussed by comparing the intensity ratio of their LO and TO phonon modes. [Copyright &y& Elsevier]

The Atomic Force Microscope (AFM) is a versatile tool in experimental research. The principle of operation of the AFM is based on the measurement of force fields between an atomically sharp tip and surface atoms of metals or insulators. In this note, we demonstrate the ability and limitation of an indigenous AFM, designed and fabricated by us, for various measurements. In particular, short- and long-range interactions between two surfaces, of different geometrical configurations, have been measured and analysed. Our results indicate the reliability of our instrument for measuring forces in the nanonewton scale. [ABSTRACT FROM AUTHOR]

We describe a simple experiment on the diffraction of monochromatic light by interfering liquid surface waves. The surface wave profile, which acts as a reflection phase grating for incident light, is generated by electrically driven vertical oscillations of two or more slightly immersed exciters. The theoretical intensity of the diffracted light agrees well with observations. In particular, we show the relation between the intensity and the amplitude (height) of the surface wave. Although invisible to the naked eye, the interference of liquid surface waves can be optically detected from the characteristic features of the diffraction pattern. In addition, we can measure the amplitude, wavelength, and phase velocity of the surface wave that propagates along the line joining the exciters. [ABSTRACT FROM AUTHOR]

We report a detailed ab initio study of two superlattice heterostructures, one component of which is a unit cell of CuPt ordered InSb 0.5 As 0.5 . This alloy part of the heterostructures is a topological semimetal. The other component of each system is a semiconductor, zincblende-InSb, and wurtzite-InAs. Both heterostructures are semiconductors. Our theoretical analysis predicts that the variation in the thickness of the InSb layer in InSb/InSb 0.5 As 0.5 heterostructure renders altered bandgaps with different characteristics (i.e., direct or indirect). The study holds promise for fabricating heterostructures, in which the modulation of the thickness of the layers changes the number of carrier pockets in these systems. [ABSTRACT FROM AUTHOR]

Ge clusters are grown on Si substrate at room temperature (Ge-RT) and also at liquid nitrogen temperature (Ge-LNT) by cluster evaporation technique. These clusters show blue luminescence. Raman measurement demonstrates the increase in strain with annealing in diffused disordered Si at the interface between Ge-LNT clusters and Si substrate. This manifests in strain-relaxation in the clusters as observed by Photoluminescence (PL) measurements. The decrease in PL intensity for Ge-RT with annealing has been attributed to reduction in surface oxide species, which is supported by Raman spectroscopic measurements. The objective of the paper is to understand the effect of thermal annealing on both interfacial strain and interdiffusion of elemental Si at the interface, together with luminescence characteristics of the clusters. [Copyright &y& Elsevier]

Results of an in-situ extended X-ray absorption fine-structure study of photostructural changes in films of amorphous selenium are reported. It is shown that at first the average coordination number decreases by about 10%. As time elapses, the initial coordination number is restored. This change is attributed to breaking of ring-like structural fragments with subsequent formation of longer chains. This model is supported by a Raman scattering experiment demonstrating the disappearance upon photoexcitation of a peak at about 112 cm -1 characteristic of rings. [ABSTRACT FROM AUTHOR]

We report electron transmission and Raman spectroscopy study of InAs nanowires. We demonstrate that the temperature dependent behavior of optical phonon energies can be used to determine the relative wurtzite fraction in the InAs nanowires. Furthermore, we propose that the interfacial strain between zincblende and wurtzite phases along the length of the wires manifests in the temperature-evolution of the phonon linewidths. From these studies, temperature-dependent Raman measurements emerge as a non-invasive method to study polytypism in such nanowires. [ABSTRACT FROM AUTHOR]

Recently, the electron mobility in wedge-shaped c-GaN nanowall networks has been estimated to cross the theoretical mobility limit for bulk GaN. Significant blue-shift of the bandgap has also been observed. Both the findings are explained in terms of two-dimensional electron gas (2DEG) formed at the central vertical plane of the walls due to the polarization charges at the two inclined faces. Carrier concentration and mobility have earlier been determined from thermoelectric power and conductivity measurements with the help of a statistical model. Due to the network nature of the system, direct measurements of these quantities from Hall experiments are not possible. Search for a better way to estimate mobility in this system thus becomes important. Since, strain can also lead to the blue-shift of the bandgap, it is also imperative to evaluate carefully the role of strain. Here, using Raman spectroscopy, we have estimated carrier concentration and mobility in these nanowall networks with varied average tip-widths. Depth distribution of strain and luminescence characteristics are also studied. The study reveals that strain has no role in the bandgap enhancement. Moreover, the electron mobility, which is determined from the lineshape analysis of the A1(LO)-plasmon coupled mode in Raman spectra, has been found to be significantly higher than the theoretical limit of mobility for bulk GaN for the same electron concentration. These results thus corroborate the picture of polarization induced vertical 2DEG formation in these walls as predicted theoretically. [ABSTRACT FROM AUTHOR]

Wafer-scale thin films of hexagonal boron nitride have exceptional thermal and mechanical properties, which harness the potential use of these materials in two-dimensional electronic, device applications. Along with unavoidable defects, grains, and wrinkles, which develop during the growth process, underlying substrates influence the physical and mechanical properties of these films. Understanding the interactions of these large-scale films with different substrates is, thus, important for the implementation of this 2D system in device fabrication. MOVPE-grown 2 and 30 nm hBN/sapphire films of size 2 in. diameter are delaminated chemically and transferred on quartz, SiO2/Si, and sapphire substrates. The structural characteristics of these films are investigated by employing Raman spectroscopy. Our results suggest that not only the roughness but also the height modulation at the surface of the substrates play a pivotal role in determining substrate-mediated mechanical strain inhomogeneity in these films. The statistical analysis of the spectral parameters provides us with the overall characteristics of the films. Furthermore, a Stark difference in the thermal evolution of strain in these films depending on substrate materials is observed. It has been demonstrated that not only the differential thermal expansion coefficient of the substrates and the films, but also slippage of the latter during the thermal treatment determines the net strain in the films. The role of the slippage is significantly higher in 2 nm films than in 30 nm films. We believe that the observations provide crucial information on the structural characteristics of the substrate-coupled wafer-scale hBN films for their future use in technology. [ABSTRACT FROM AUTHOR]

The correlations between properties of hydrogenated diamondlike carbon films and their Raman spectra have been investigated. The films are prepared by plasma deposition technique, keeping different hydrogen to methane ratios during the growth process. The hydrogen concentration, sp3 content, hardness, and optical Tauc gap of the materials have been estimated from a detailed analysis of their Raman spectra. We have also measured the same parameters of the films by using other commonly used techniques, such as sp3 content in films by x-ray photoelectron spectroscopy, their Tauc gap by ellipsometric measurements, and hardness by microhardness testing. The reasons for the mismatch between the characteristics of the films, as obtained by Raman measurements and by the above mentioned techniques, have been discussed. We emphasize on the importance of the visible Raman spectroscopy in reliably predicting the above key properties of diamondlike carbon films. [ABSTRACT FROM AUTHOR]

Abstract Using first principles calculations we unveil the interfacial strain relaxation in (wurtzite-InAs) n /(zinc-blend-InSb) m multilayer specimens. We have shown that the distribution of strain along the growth direction depends on the relative thickness of the segments of the multilayer. The observed result has been explained in view of the propagation of lattice deformation due to lattice mismatch between InAs and InSb. To the end we have demonstrated that the fine tuning of the strain with the thickness of layers can be exploited to vary the band gap along the length of the multilayer. The modulation of the band gap in a multilayer system finds various applications in designing optoelectronic devices. Highlights • Strain profile in (InAs) n /(InSb) m multilayer systems, using first principles density functional theory calculations, is reported. • The role of relative thickness of the components of the multilayers in strain distribution is discussed. • The modulation of band gap along the length of the multilayer due to the strain distribution has been demonstrated. [ABSTRACT FROM AUTHOR]

Resonance Raman measurements are carried out on defect-free wurtzite GaP nanowires over the excitation energy range between 2.19 and 2.71 eV. Resonances of the E1(LO) and A1(LO) modes demonstrate the existence of energy states with Γ9hh and Γ7V (Γ7C) symmetries of the valence (conduction) band and enable us to measure wurtzite phase GaP band energies. In addition, we have performed temperature dependent resonant Raman measurements, which allowed us to extrapolate the zero temperature values of Γ point energies. Our results provide the necessary feedback required for refining the available theoretical calculations to derive the correct wurtzite III-V semiconductor band structure. [ABSTRACT FROM AUTHOR]

• Y 3-x Nd x Al 5 O 12 system studied to mimic substituted garnets for MA transmutation. • Synthesis route enabled stabilization of 33 mol% Nd3+ substituted garnet observed. • Incorporation of Nd3+ causes expansion of the cubic garnet phase. • Stabilization of defect stabilized rhombohedral NdAlO 3 in Nd3+-rich region. • Thermal conductivity/thermal expansion decrease with Nd3+ incorporation in Y 3 Al 5 O 12. The present work reports structural and thermophysical investigation in Nd3+- substituted Y 3 Al 5 O 12 (YAG). In addition to being an interesting system for studying the effect of isovalent substitution on phase/structural evolution in a garnet system, it has direct relevance as an inert matrix for burning minor actinides (MA: Am, Cm, and Np) for reducing the long-term radiotoxicity of nuclear wastes. More importantly, garnet has superior thermal conductivity than the zirconia-based systems which are widely being explored for this application. In order to investigate the phase miscibility and resulting thermophysical behavior, fourteen nominal compositions in Y 3-x Nd x Al 5 O 12 (0.0 ≤ x ≤ 3.0) system (Nd3+: chosen as the surrogate for MA) were synthesized by gel combustion followed by variable temperature annealing. The atomistic-level mixing ensured high solubility (33 mol% at 1273 K) of Nd3+ in YAG retaining the garnet-phase but the solubility reduced (13 mol%) upon annealing at 1773 K. Raman spectroscopy supported the phase evolution with composition and temperature. The microstructure of select compositions was investigated using SEM/EDS. Nd3+ caused dilation of garnet lattice, increase in average thermal expansion, and lowering of thermal conductivity. It must be emphasized that Nd-doped garnet still possessed better thermal conductivity compared ZrO 2 -based systems, a desirable attribute for matrices for MA-transmutation. Other important thermodynamic functions such as molar heat capacity, entropy and molar Gibbs free energy were determined. The study exhibits (a) roles of ionic size, synthesis route, temperature on phase relations upon isovalent substitution in YAG; (b) validation of the thermophysical performance of YAG-type material for MA transmutation. [Display omitted] [ABSTRACT FROM AUTHOR]

Half-metallic ferromagnetic full Heusler alloy NiFeMnSn is a promising material in spintronic device fabrication as it carries high spin polarization and high Curie temperature (Tc = 405 K). Understanding electronic excitations in a spin-polarized band structure is essential for the further use of this material in spin-based devices and to optimize the spin-dependent electronic structure in related compounds. In this Letter, we report electronic Raman scattering of NiFeMnSn with spectral signatures at a higher wavenumber than expected from the calculated phonon modes of the system. Temperature-dependent Raman spectroscopy demonstrates a non-monotonic behavior of the Raman shift with temperature across Tc. The orbital resolved electronic density of states and electronic band structure for both spin channels of the system, as obtained from the first principles density functional theory calculations, suggest that the observed Raman signatures originate from the Fe d orbital and its splitting due to the crystal field near the Fermi level. Furthermore, a strong magnetic field dependence of the spectral profile is observed. The study not only exhibits electronic Raman scattering in a Heusler alloy compound, which was unexplored to date, but also establishes Raman scattering as a promising probe to study the orbital-resolved partial density of states in the band structure near the Fermi level of a Heusler alloy. [ABSTRACT FROM AUTHOR]

The article presents a mapping of the residual strain along the axis of InAs/InSb heterostructured nanowires. Using confocal Raman measurements, we observe a gradual shift in the transverse optical phonon mode along the axis of these nanowires. We attribute the observed shift to a residual strain arising from the InAs/InSb lattice mismatch. We find that the strain is maximum at the interface and then monotonically relaxes towards the tip of the nanowires. We also analyze the crystal structure of the InSb segment through selected area electron diffraction measurements and electron diffraction tomography on individual nanowires. [ABSTRACT FROM AUTHOR]

The underlying physics which explains the role of cationic and anionic defect dynamics in determining the catalytic activity and ionic conductivity of aliovalent ion-doped ceria is complex and not yet fully understood. To address this issue, we have investigated the structural evolution of LaxCe1-xO2–δ, where x =0.1, 0.2, 0.3, 0.4, and 0.5. Rietveld refinements of the X-ray diffraction patterns reveal that the crystal structure belongs to a disordered fluorite phase for all samples. We find a systematic increase in the lattice parameter along with a gradual decrease in oxygen site occupancy with the increase in La3+ doping concentration. In Raman spectra of doped compounds, other than well-known crystalline F2g and defect related modes, we observe the presence of an additional Raman mode. The Raman line-shape analysis indicates the non-resonant Fröhlich character of this mode. Temperature dependent Raman measurements demonstrate unique characteristics of this Raman peak. In addition, from the change in relative intensity ratio of the Raman modes related to different types of defect states, we show that vacancies cannot be considered as isolated defects beyond a critical doping level. We propose that the evolution of Raman intensities of defect related modes and Fröhlich mode with the doping level can be used as a marker to determine the role of electron-phonon coupling and anion vacancies in the catalytic activity of doped ceria. Furthermore, by studying the photocatalytic measurements for La3+ doped ceria compounds, we demonstrate that the anion vacancies do not always play a direct role in controlling functional properties. [ABSTRACT FROM AUTHOR]

Human serum albumin (HSA), the most abundant plasma protein in the human body is known to form fibrils under partial denaturing conditions. Natural polyphenols are known to interact with HSA and some polyphenols have been shown to be potent inhibitors of amyloid fibrillation. (−)-Epigallocatechin gallate (EGCG), the major component of green tea is known to inhibit amyloid fibrillation. In this report, we have investigated the effect of EGCG on native HSA as well as on the fibrillation process of HSA from amide III band analysis of their respective visible Raman spectra. The differential role of the tryptophan (Trp214) residue present in domain II of HSA in the absence and presence of EGCG has been pointed out using fluorescence anisotropy and visible Raman spectroscopy. [ABSTRACT FROM AUTHOR]

In this article we revisit the much-studied behavior of self-assembled aggregates of gold colloidal particles. In the literature, the electrostatic interactions, van der Waals interactions, and the change in free energy due to ligand-ligand or ligand-solvent interactions are mainly considered to be the dominating factors in determining the characteristics of the gold aggregates. However, our light scattering and imaging experiments clearly indicate a distinct effect of light in the growth structure of the gold colloidal particles. We attribute this to the effect of a non-uniform distribution of the electric field in aggregated gold colloids under the influence of light. [ABSTRACT FROM AUTHOR]

The present work reports detailed structural and electrical studies on A-site substituted La x Gd 1-x InO 3 (0.0 ≤x ≤ 1.0) system with structurally different end members in search for tailored lead-free relaxors. The motivation is the possibility to manipulate the crystal structure to maneuver electrical properties in hexagonal GdInO 3 , a candidate for geometric ferroelectricity. The hybrid synthesis protocol involving gel-combustion led to stabilisation of metastable polymorphs in some nominal compositions due to kinetic stabilisation. Non-preference of La3+ for 7- fold coordinated A-site in hexagonal structure manifested in wide-ranging orthorhombic phase field prevailing even in Gd3+-rich region, also supported by theoretical studies. P-E studies on Gd3+-rich compositions exhibited hysteresis loop which suddenly became narrow for the nominal composition La 0.4 Gd 0.6 InO 3 with very low remanent polarisation. This along with broad maximum exhibited in plot of dielectric constant vs temperature that shifts to higher T upon increasing frequency, for La 0.4 Gd 0.6 InO 3 , supports presence of relaxor-type behavior. Signature of hexagonal-type vibrations in otherwise bulk orthorhombic (by XRD) La 0.4 Gd 0.6 InO 3 and anomalous trend in La/Gd vibrational mode along with narrowing down of Raman modes have been cited as plausible structural reasons for the relaxor behaviour. This has significance in context of structure-electrical property relationship leading to development of potential lead-free relaxors. [Display omitted] • Detailed phase evolution in GdInO 3 (P6 3 cm)- LaInO 3 (Pnma) with composition and T. • C-type metastable phases observed by synthesis route endowed kinetic stabilisation. • Non-preference of La3+ for 7-fold capped octahedra yields wide orthorhombic field. • Extremely low field independent leakage current (4 × 10−5 μA/mm2) observed for GdInO 3. • New lead-free relaxor by A-site distortion by 40 mol%La3+ substitution in h-GdInO 3. [ABSTRACT FROM AUTHOR]

Abstract: The second-order transverse acoustic mode and amorphous Raman modes, originating from a continuous random network and medium range ordering (MRO), in high energy light ion (HELI) irradiated GaAs are investigated. The change in the phonon density of states of the transverse acoustic mode phonon distinguishes the effect of HELI irradiation on highly resistive undoped and chromium-doped GaAs. The boson mode, originating from the MRO of the system, has been identified and a model based on phonon-fracton scattering has been used for the explanation of this “boson mode”. The spectral dimension, correlation length and the scaling factor, with which the elastic constant varies with length in MRO regions in GaAs, are estimated. [Copyright &y& Elsevier]

The problem of finding minimum (local as well as absolute) path lengths joining given points (or terminals) on a plane is known as the Steiner problem. The Steiner problem arises in finding the minimum total road length joining several towns and cities. We study the Steiner tree problem using six-pin soap films. Experimentally, we observe spanning trees as well as Steiner trees partly by varying the pin diameter. We propose a possibly exact expression for the length of a spanning tree or a Steiner tree, which fails mysteriously in certain cases. [ABSTRACT FROM AUTHOR]

Abstract: In this article, we have compared the metal–amino acid interactions in Tyr–Ag and Phe–Ag complexes through pH dependent SERS measurements. By analyzing the variation in relative intensities of SERS bands with the pH of the amino acid solution, we have obtained the orientation and conformation of the amino acid molecules on the Ag surface. The results obtained from our experimental studies are supported by the energy minimized structures and the observed charge distributions in different terminals of the molecules. This, in a way, shows that SERS measurements not only exhibit the interaction of the amino acid molecules with Ag clusters but also demonstrate their orientation around it. We have addressed a long standing query on whether the amine group is directly attached to the Ag surface along with the carboxylate group and π-electrons in these systems. In addition, pH dependent optical absorption and transmission electron microscopy measurements have been performed to understand the required conditions for the appearance of the SERS spectra in the light of the aggregation of metal particles and the number of hot sites in the sol. Our results confirm that the formation of hot sites in the sol plays a direct role in forming a stable Ag–ligand complex. Furthermore, the interaction kinetics of metal–amino acid complexes have been analyzed via both Raman and absorption measurements. [Copyright &y& Elsevier]

Modern materials science requires efficient processing and characterization techniques for low dimensional systems. Raman and photoluminescence spectroscopy are important nondestructive tools which provide much information about such systems. Commercial Raman spectrometers are expensive. We discuss a less expensive apparatus with assembled collection optics. Studies of Ge nanoparticles, porous silicon (nanowire), carbon nanotubes, and two-dimensional InGaAs quantum layers demonstrate that this apparatus is useful for teaching and research on nanomaterials. [ABSTRACT FROM AUTHOR]

We embarked on a study of Scandium (Sc) doped (onto Ga site) gallium ferrite (GaFeO3) and found remarkable magnetic properties. In both doped as well as parent compounds, there were three types of Fe3+ions (depending on the symmetry) with the structure conforming to space group Pna21 (Sp. Grp. No. 33) below room temperature down to 5 K. We also found that all Fe3+ions occupy octahedral sites, and carry high spin moment. For the higher Sc substituted sample (Ga1-xScxFeO3:x = 0.3), a canted magnetic ordered state is found. Spin-phonon coupling below Néel temperature was observed in doped compounds. Our results indicated that Sc doping in octahedral site modifies spin-phonon interactions of the parent compound. The spin-phonon coupling strength was estimated for the first time in these Sc substituted compounds. [ABSTRACT FROM AUTHOR]

Microwave radiations from various electronic devices are of serious health concern. In this article, using spectroscopic measurements, we show that the microwave radiation of strength 22 dBm and frequency 10 GHz facilitates protein fibrillation. However, this adverse effect of low-field radiation can be restricted by the presence of biocompatible citrate-capped gold nanoparticles. The dissipative field by metallic particles is able to disrupt the fibrillar network. We believe that the obtained results paved a way to find a therapeutic measure to combat fibrillation related diseases. [ABSTRACT FROM AUTHOR]

Optical properties of nanocrystalline red-emitting phosphor, europium-doped yttria (Y2O3:Eu3+), of average particle size of 15 nm are investigated. The intensity of the strongest emission line at 612 nm is found to be highest in the nanocrystalline sample with 4 at. wt % of europium. The narrow electronic emission spectrum suggests a crystalline surrounding in this nanomaterial. We have estimated the strength of the crystal-field parameter at the dopant site, which plays a crucial role in determining the appearance of the intense emission line. The equilibrium temperature of this system has also been calculated from the intensity ratio of Stokes and anti-Stokes Raman scattering. Though known for the bulk samples, our approach and consequent results on the crystalline nanomaterial of Y2O3:Eu3+ provide a unique report, which, we believe, can be of considerable significance in nanotechnology. [ABSTRACT FROM AUTHOR]

Rare earth indates are an interesting class of compounds with rich crystallography. The present study explores the crystallographic phases observed in REInO3 (RE: La–Yb) systems and their dependence on synthesis routes and annealing temperature. All REInO3 compositions were synthesized by a solid state route as well as gel-combustion synthesis (GC) followed by annealing at different temperatures. The systems were well characterized by powder XRD studies and were analysed by Rietveld refinement for the structural parameters. The cell parameters were observed to decrease in accordance with the trend in ionic radii on proceeding from lighter to heavier rare earth ions. Interestingly, the synthesis route and the annealing temperature had a profound bearing on the phase relationships observed in the REInO3 series. The solid state synthesized samples depicted an orthorhombic phase (Pbnm) field for LaInO3 to SmInO3, followed by a hexagonal-type phase (P63cm) for GdInO3 to DyInO3. However, the phase field distribution was greatly influenced upon employing gel-combustion (GC) wherein both single-phasic hexagonal and orthorhombic phase fields were found to shrink. Annealing the GC-synthesized compositions to still higher temperatures (1250 °C) further evolved the phase boundaries. An important outcome of the study is observance of polymorphism in SmInO3 which crystallized in the hexagonal phase when synthesized by GC and orthorhombic phase by solid state synthesis. This reveals the all-important role played by synthesis conditions. The existence and energetics of the two polymorphs have been elucidated and discussed with the aid of theoretical studies. [ABSTRACT FROM AUTHOR]

Single crystals of the iron-pnictide compound BaFe 2 (As 1 − x P x) 2 for x ∼ 0.23, with a doping concentration near quantum criticality and enhanced nematic fluctuating state in the doping-temperature phase diagram, have been studied. Transport measurements confirm the presence of a magneto-structural transition at 60 K from the tetragonal to the orthorhombic phase, followed by a superconducting transition below 16 K. Micro-Raman spectra of the compound exhibit a phonon mode at 211 cm−1 and two broad modes (BMs) at 515 cm−1 and 635 cm−1, which corresponds to an energy difference of 15 meV. The temperature dependent Raman measurements reveal that the intensity of these BMs drop over the temperature range between 80 K and 300 K. In the non-superconducting state, strong anisotropic behaviour is observed for these BMs in polarization dependent Raman scattering. Electronic structure calculations for doped and undoped BaFe 2 As 2 show that while Fe d x z and d y z orbitals do not split in the tetragonal phase, the splitting energy is 13.5 meV in the orthorhombic phase of the doped system, which is reasonably close to the experimentally observed value of the energy separation of the BMs. We believe that the reported BMs are consistent with the signature of electronic Raman scattering involving the crystal field levels of d -orbitals of Fe2＋ due to local breaking of the C 4 symmetry in the doped system. • Local symmetry breaking in tetragonal phase of P doped BaFe 2 As 2 near quantum critical point. • Signature of crystal field splitting using temperature dependent micro Raman spectroscopy. • Calculation of Fe d orbitals split energies in local orthorhombic phase using DFT. [ABSTRACT FROM AUTHOR]

In this article, we report negative thermal expansion and spin frustration in hexagonal GdInO3. Rietveld refinements of the x-ray diffraction patterns reveal that the negative thermal expansion in the temperature range of 50-100 K stems from the triangular lattice of Gd3+ ions. The downward deviation of the low-temperature inverse susceptibility (χ-1) versus T plot from the Curie-Weiss law and the large value of the ratio, 0CW|/TN>28, where θCW and TN are respectively Curie-Weiss and Neel temperature, indicate a strong spin frustration, which inhibits long-range magnetic ordering down to 1.8 K. Magnetostriction measurements clearly demonstrate a spin-lattice coupling in the system. Low-temperature anomalous phonon softening, as obtained from temperature-dependent Raman measurements, also reveals the same. Our experimental observations are supported by first-principles density functional theory calculations of the electronic and phonon dispersion in GdInO3. The calculations suggest that the GdInO3 lattice is highly frustrated at low temperature. Further, the calculated normal mode frequencies of the Gd-related G point phonon modes reveal significant magnetoelastic coupling in this system. The competitive role of magnetic interaction energy and thermal stabilization energy in determining the change in interatomic distances is the possible origin for the negative thermal expansion in GdInO3 over a limited range of temperature. [ABSTRACT FROM AUTHOR]

Structural and functional applications involving La 2 Zr 2 O 7 exploit the data on fluorite to pyrochlore phase transition, because of the strong dependence on the physical properties of the system with its phase stability. Though studied for decades, the origin of fluorite to pyrochlore phase transition in La 2 Zr 2 O 7 is still not well understood. In this article, we confirm the presence of a fluorite to pyrochlore phase transition in La 2 Zr 2 O 7 system in the temperature range 1000–1450 °C. The phase transition along with the associated structural properties is investigated with the help La 2 Zr 2 O 7 samples calcined at different temperatures. [ABSTRACT FROM AUTHOR]

Raman spectroscopy and Hall measurements have been carried out to investigate the differences in near-surface charge carrier modulation in high energy (~100 MeV) silicon ion (Si8+) and oxygen ion (O7+) irradiated n-GaAs. In the case of O ion irradiation, the observed decrease in carrier concentration with increase in ion fluence could be explained in the view of charge compensation by possible point defect trap centers, which can form because of elastic collisions of high energy ions with the target nuclei. In Si irradiated n-GaAs one would expect the carrier compensation to occur at a fluence of 2.5 × 1013 ions/cm2, if the same mechanism of acceptor state formation, as in case of O irradiation, is considered. However, we observe the charge compensation in this system at a fluence of 5 × 1012 ions/cm2. We discuss the role of the complex defect states, which are formed because of the interaction of the primary point defects, in determining carrier concentration in a Si irradiated n-GaAs wafer. The above results are combined with the reported data from the literature for high energy silver ion irradiated n-GaAs, in order to illustrate the effect of both electronic and nuclear energy loss on trap creation and charge compensation. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

In this study, we attempt to find the origin of atypical doping concentration dependant electrical properties of group III element (Al, Ga, In) doped ZnO thin films. The carrier density and mobility of these films are measured and compared for a wide range of doping concentrations. It is found that donor density determines the electrical properties of the films for a low level of doping, whereas lattice defects play a dominant role beyond a certain level of doping concentration. We also demonstrate an interrelationship between the electrical properties and the structural/optical properties of the films. We find 2% as optimum doping concentration for Al-, Ga- or In-doped ZnO for obtaining highest conducting layers and Ga emerges as the most effective dopant among all. [ABSTRACT FROM AUTHOR]

This article reports a comprehensive study on damage evolution in undoped InP due to 100 MeV silver (Ag 7+ ) ion irradiation. Raman and Rutherford back scattering channeling (c-RBS) measurements are employed to bring out two different aspects of disorder in the system. While Raman spectroscopy revealed a monotonic increase in sub-surface strain due to ion irradiation, the later detected heavy damage in the wafer at high fluences. Furthermore, we have estimated the lattice temperature under above irradiation conditions in InP using a unified thermal spike model. The model includes both inelastic thermal spike and elastic collision spike along with the effect of latent heat. This model explains the observed damage evolution of the target. Above experimental techniques in conjunction with the simulation model provides a qualitative explanation of the damage accumulation leading to structural modification in the Ag ion-irradiated InP wafer. [ABSTRACT FROM AUTHOR]

In vitro fibrillation of hen egg white lysozyme (HEWL) causes complete reduction of Cu(II) to Cu(I) at pH 7. Here in the present article, we have shown the presence of both Cu(II) and Cu(I) at pH 11 during fibrillation of HEWL using electron paramagnetic resonance and Raman spectroscopy. Our results suggest the existence of a partially reducing environment during fibrillation of hen egg white lysozyme at pH 11. The fibrillation process is governed by the pH of the solution and maximum fibrillation is found to occur at pH 11. Fibrils formed in the absence of Cu(II) were also found to cause significant hemolysis of RBC. [ABSTRACT FROM AUTHOR]

[Display omitted] • Resonance Raman spectroscopy is employed for diagnosis of diabetic retinopathy. • Statistical analysis of spectral data holds promise in early detection of the disease. • The study endorses carotenoid level in human serum as a biomarker for the pathosis. Diabetic retinopathy (DR) is a common health concern. Unfortunately, the metabolic pathway causing DR is yet to be understood. The carotenoid level in the human body is known to protect the health of the eyes. In this work, resonance Raman spectroscopy and multivariate analysis of the spectral data of human serum are reported as next-generation spectropathologic tools to detect retinal degeneration efficiently. The proposed technique shows promise by endorsing ocular carotenoids as a critical biomarker for such pathosis. Furthermore, the multivariate analysis of the spectral data distinguishes between two different stages of the disease. The machine learning algorithm is used to estimate a significant accuracy of 94% of the proposed model for the classification. As the carotenoid level can be controlled by dietary intake, we believe that the reported results also indicate a therapeutic role of the same in DR. [ABSTRACT FROM AUTHOR]

Abstract: The formation of strained layers and a non-monotonic evolution of strain in high energy (100MeV) silver ion (Ag7+) irradiated undoped semi-insulating GaAs are observed and analyzed using Raman scattering and high resolution X-ray diffraction (HRXRD) measurements. At low fluence, compressively strained layers are formed, whereas, with increase in fluence both compressive and tensile strains appear as observed from HRXRD measurements. Further, at low fluence, the change in compressive strain with increase in fluence is found to be sharper than what is observed at higher fluence, thereby suggesting a critical fluence value, beyond which there is a simultaneous generation and annihilation of vacancy type defects. The initial blue shift and subsequent relative red shift beyond above critical fluence in the Raman peak also qualitatively reveal non-monotonic evolution of strain in this case. Finally, we demonstrate the sensitivity of Raman spectroscopy in detecting the decrease in lattice ordering in the crystal in the low fluence regime, below the detection limit of Rutherford back-scattering channeling (c-RBS) measurements. [Copyright &y& Elsevier]

In this article, we report the structural phase transitions in Bi4 V2 O11 as observed from temperature-dependent Raman scattering and X-ray diffraction measurements. Four different types of highly disordered coordination polyhedra around the vanadium atoms with large dispersion of V-O bond lengths are observed in Bi4 V2 O11 at ambient temperature. The observed V-O bond lengths could be grouped into two categories, viz. shorter <1.7 Å and longer >1.7 Å. The Raman modes of Bi4 V2 O11 could be assigned to vibration of these bonds and V-O-V linkages. We could correlate the difference in degree of anharmonicity of the phonon modes with temperature to differences in V-O bond strength. The local structure of vanadium-oxygen network in Bi4 V1.8 Cu0.2 O10.7 was also obtained by similar studies. The effect of highly disordered anion sublattice in the doped compound is reflected in the broadening of the Raman modes. [ABSTRACT FROM AUTHOR]

Highlights: [•] PCA of Raman data discriminates molecular structure of HEWL protein and fibrils. [•] SD of scores in PCA plots determines variability in the structure within a species. [•] Overall structure significantly differs for fibrils grown at different pH values. [•] Overall structure of fibrils grown at different pH values in Cu(II) has similarity. [•] Presence of Cu(II), inhibits the formation β-sheet component in HEWL fibrils. [ABSTRACT FROM AUTHOR]