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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]

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]

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]

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]

Abstract: In this article, we discuss metal–protein interactions in the Ag–lysozyme complex by spectroscopic measurements. The analysis of the variation in relative intensities of SERS bands reveals the orientation and the change in conformation of the protein molecules on the Ag surface with time. The interaction kinetics of metal–protein complexes has been analyzed over a period of 3h via Raman measurements. Our analysis indicates that the Ag nanoparticles most likely interact with Trp123 which is in close proximity to Phe34 of the lysozyme molecule. [ABSTRACT FROM AUTHOR]

Abstract: Surface enhanced Raman spectra of Phenylalanine (Phe) in Ag colloidal solution have been recorded for Phe solutions at different pH. Spectral line-shape analyses of three enhanced modes have been carried out between pH 4.5 and 10.5. The variation of line-width with pH reveals two mechanisms in solution: (i) the fluctuation of pH in microscopic volume and (ii) the motional narrowing caused by the intermolecular ionic interaction. The different charge states of the reference molecule are responsible for the observed bond softening with decrease in pH. The ‘Raman shift’ and the ‘Raman activity’ of the vibrational modes with maximum enhancement have been explained by carrying out DFT calculations. [Copyright &y& Elsevier]