Presence Of Vibrational Modes Research Articles

Effect of Mo doping in vanadium pentoxide (V2O5) for dye degradation

In this work, a surfactant-free approach was successfully achieved for synthesizing V2O5 nanoparticles doped with varying concentrations of Mo (x = 2 %, 4 %, 6 %, and 8 %). The preparedsamples were characterizedusing Energy dispersive X-ray analysis (EDAX), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Scanning electron microscope (SEM), and Raman spectroscopy. XRD confirmed the orthorhombic structure of synthesized nanoparticles. SEM was used for analyzingthe nanoparticles' morphology. Sample purity and doping were verified by EDAX. Additionally, optical band gaps were obtained using a UV–visible Spectrometer. The presence of vibrational modes in the synthesizednanoparticles was identified using FTIR. The synthesized nanoparticles have a significant potential for dye degradation. The potential for dye degradation in 6 % Mo-doped V2O5 nanoparticles is higher than that in pure, 2 %, 4 %, and 8 % Mo-doped samples.

Influence of synthesis strategy on the formation of microspheres of self-assembled CuO rectangular nanorods and hierarchical structures of self-assembled Cu2O nanospheres from single precursor (copper (II) acetate monohydrate) and their structural, optical, thermal and magnetic properties

Here, microspheres of self-assembled CuO rectangular nanorods and hierarchical structures of self-assembled Cu2O nanospheres have been synthesized from single precursor (copper (II) acetate monohydrate) using hydrothermal method. The utility of NH3 and N2H4·H2O as reducing agents for the formation of phases and morphology of CuO and Cu2O has been investigated. The XRD patterns and Raman spectra indicate that the synthesized CuO and Cu2O nanostructures are single phase and high crystalline. The SEM images clearly show that the rectangular shaped CuO nanorods are densely packed and self-organized into microspheres whereas self-assembled Cu2O nanospheres makes hierarchical Cu2O structures. The TEM images reveal that the individual CuO rectangular nanorod is having ends with a small faceted nano-tip-like structure while the hierarchical nanostructures of Cu2O consist of agglomerated nanospheres with distinguishable grain boundaries. The presence of vibrational modes, associated with the relative motion of both copper and oxygen atoms, in the FTIR spectra also supports the formation of CuO and Cu2O phases, respectively. The optical properties of the synthesized materials were revealed using absorption spectra. The thermal behaviour was also investigated through DSC measurements. The magnetic properties have also been investigated in order to explore new insights responsible for specific magnetic behaviour.

Multiscale cyclic dynamics in light harvesting complex in presence of vibrations and noise

Starting from the many-body Schr\"odinger equation, we derive a new type of Lindblad Master equations describing a cyclic exciton/electron dynamics in the light harvesting complex and the reaction center. These equations resemble the Master equations for the electric current in mesoscopic systems, and they go beyond the single-exciton description by accounting for the multi-exciton states accumulated in the antenna, as well as the charge-separation, fluorescence and photo-absorption. Although these effects take place on very different timescales, their inclusion is necessary for a consistent description of the exciton dynamics. Our approach reproduces both coherent and incoherent dynamics of exciton motion along the antenna in the presence of vibrational modes and noise. We applied our results to evaluate energy (exciton) and fluorescent currents as a function of sunlight intensity.

Structural, spectroscopic and optical properties of pure and gadolinium doped neodymium phosphate nanoparticles prepared using wet chemical route

ABSTRACTNanoparticles of neodymium phosphate and 5% gadolinium (Gd) doped neodymium phosphate prepared by co-precipitation technique belong to the monoclinic monazite phase with space group P21/n. The average crystallite size calculated using Debye-Scherrer and Williamson Hall method matches very well with grain size observed from scanning electron microscope images and Image J software. FTIR analysis signifies the presence of vibration modes along with the phosphate group and a slight shift in wave number was observed with the substitution of gadolinium into neodymium phosphate. Ultraviolet absorption spectrophotometer show transitions from ground state to various excited state within the 4f shell and the absorption edge shifts towards the lower wavelength side (blue shift) with the addition of dopant. Raman spectrum further confirms the formation of phosphate group with relevant peaks.

Mechanosynthesis and structural characterization of nanocrystalline Ce1–xYxO2–δ (x=0.1–0.35) solid solutions

A series of nanostructured fluorite-type Ce1–xYxO2–δ (0≤x≤0.35) solid solutions, prepared via high-energy milling of the CeO2/Y2O3 mixtures, are investigated by XRD, HR-TEM, EDS and Raman spectroscopy. For the first time, complementary information on both the long-range and short-range structural features of mechanosynthesized Ce1–xYxO2–δ, obtained by Rietveld analysis of XRD data and Raman spectroscopy, is provided. The lattice parameters of the as-prepared solid solutions decrease with increasing yttrium content. Rietveld refinements of the XRD data reveal increase in microstrains in the host ceria lattice as a consequence of yttrium incorporation. Raman spectra are directly affected by the presence of oxygen vacancies; their existence is evidenced by the presence of vibration modes at ~560 and ~600cm–1. The detailed spectroscopic investigations enable us to separate extrinsic and intrinsic origin of oxygen vacancies. It is demonstrated that mechanosynthesis can be successfully employed in the one-step preparation of nanocrystalline Ce1–xYxO2–δ solid solutions.

Structural, surface and mechanical characterization of spray-deposited molybdenum disulfide thin films

Molybdenum disulfide (MoS2) was deposited with the precursor salt of ammonium molybdate tetrahydrate and thiourea on glass substrate at various precursor solution volume (10–50mL) using the spray pyrolysis technique. The X-ray diffraction pattern indicates the polycrystalline nature of the film with a hexagonal structure and the occurrence of peak shift due to stacking fault. The field-emission scanning electron micrograph shows the increment in grain growth with increase in the precursor solution volume, leading to the conversion of grains to nanoflakes. Energy dispersive spectrum confirms the presence of molybdenum and sulfur. Vickers microhardness shows increament in microhardness with decrease in the precursor solution volume. The mechanical properties related to microhardness were analyzed. Raman analysis confirms the hexagonal structure of MoS2 with the presence of vibrational modes.

Decomposed Sliding Mode Control of the Drive with Interior Permanent Magnet Synchronous Motor and Flexible Coupling

A decomposed sliding mode control of the drive with an interior permanent magnet synchronous motor and flexible coupling is presented. Decomposition exploits principles of vector control to divide motor into channel for control of magnetic flux and channel for control of torque separately. Sliding mode control principles are exploited to keep demanded value of magnetic flux and to control load angle in the presence of vibration modes and external disturbances. To obtain continues voltage as a control variable a smoothing integrator follows signum function in both channels. As a modification the switching governed by signum function is replaced by the high gain including rearrangement of the control system block diagram. The simulations indicate that the control system yields the desired robustness and further investigations are recommended.

A model for recombination in Type II dye-sensitized solar cells: Catechol–thiophene dyes

Recombination in dye-sensitized solar cells with direct injection is cast as internal conversion in the dye–Ti(OH) 2 complex. For catechol–thiophene dyes with 1, 2, or 3 thiophene units, the complex reproduces the previously observed dye-to-semiconductor bands. We compare the decomposition of the internal conversion rate by vibrational mode and predict a trend in recombination with the extension of conjugation, which offers an explanation for the trend in DSSC efficiency. We employ a simple model for the vibrational factors and show that they are only important in the presence of vibrational modes with ℏ ω ⩽ kT and strong electronic factors, as is the case here.

Structural and spectroscopic characterization of poly(styrene sulfonate) films doped with neodymium ions

Abstract This work reports the structural and spectroscopy characterization of poly(styrene sulfonate) (PSS) films doped with neodymium (Nd) ions. Nd–PSS films were processed using the acid of poly(styrene sulfonate) – H–PSS and neodymium nitrate – Nd(NO 3 ) 3 ; the maximum incorporation of Nd ions in the polymeric matrix was equal 19.3%. The absorption in the UV–Vis–NIR spectral region presents typical electronic transitions of Nd 3+ ions, with well resolved peaks. The infrared spectra present the transition bands of PSS with characteristic line shape broadening, and the presence of vibrational modes of N–O groups in the range of 1400–720 cm −1 , prove the permanence of Nd(NO 3 ) x , with x = 1, 2 and/or 3, in the H–PSS matrix. UV–Vis site selective photoluminescence data indicate that the incorporation of Nd 3+ introduces a blue shift in PSS emission (325–800 nm), decreasing the interaction between adjacent PSS lateral groups (aromatic rings). Nd 3+ reabsorption and energy transfer effects between the PSS matrix and Nd 3+ were also observed. The IR emission of Nd–PSS films at 1076 nm ( 4 F 3/2 → 4 I 11/2 ) present constant efficiency, independent on Nd 3+ concentration. The Judd–Ofelt theory was employed to analyze radiative properties. The excitation spectra prove the energy transfer between the polymeric matrix and Nd 3+ . Complex impedance data was used to probe relaxation processes during the charge transport within the polymeric matrix.

Probing inhibitors binding to human urokinase crystals by Raman microscopy: implications for compound screening.

Inhibition of urokinase activity represents a promising target for antimetastatic therapy for several types of tumor. The present study sets out to investigate the potential of Raman spectroscopy for defining the molecular details of inhibitor binding to this enzyme, with emphasis on single crystal studies. It is demonstrated that high quality Raman spectra from a series of five inhibitors bound individually to the active site of human urokinase can be obtained in situ from urokinase single crystals in hanging drops by using a Raman microscope. After recording the spectrum of the free crystal, a solution of inhibitor containing an amidine functional group on a naphthalene ring was added, and the spectrum of the crystal-inhibitor complex was obtained. The resulting difference Raman spectrum contained only vibrational modes due to bound inhibitor, originating from the protonated group, i.e., the amidinium moiety, as well as naphthalene ring modes and features from other functionalities that made up each inhibitor. The identification of the amidinium modes was placed on a quantitative basis by experimental and theoretical work on naphthamidine compounds. For the protonated group, -C-(NH2)(2)(+), the symmetric stretch occurs near 1520 cm(-1), and a less intense antisymmetric mode appears in the Raman spectra near 1680 cm(-1). The presence of vibrational modes near 1520 cm(-1) in each of the Raman difference spectra of the five complexes examined unambiguously identifies the protonated form of the amidinium group in the active site. Several advantages were found for single crystal experiments over solution studies of inhibitor-enzyme complexes, and these are discussed. The use of single crystals permits competitive binding experiments that cannot be undertaken in solution in any kind of homogeneous assay format. The Raman difference spectrum for a single crystal that had been exposed to equimolar amounts of all five inhibitors in the hanging drop showed only the Raman signature of the compound with the lowest K(i). These findings suggest that the Raman approach may offer a route in the screening of compounds in drug design applications as well as an adjunct to crystallographic analysis.