Search

In situ surface-enhanced Raman spectroscopy (SERS) was used to monitor the electrochemical behavior of squaric acid on a gold electrode in aqueous solution, at different pH values. Octahydroxycyclobutane and other intermediates were identified. The formation of the squarate radical anion is suggested. The relative intensities of the bands in the SER spectra, together with the surface selection rules, suggest that different adsorption geometries of squaric acid and its deprotonated species are involved. In the presence of chloride, squaric acid and hydrogeno-squarate adsorb via the carbonyl and hydroxyl groups on the electrode surface, whereas their adsorption on metallic thin films occurs mainly via the carbonyl moieties. The observation of carbon monoxide and hydrocarbon bands confirms the catalytic effect of the metallic surfaces investigated in the decomposition of such oxocarbon species. [Copyright &y& Elsevier]

Cefoperazone is a broad-spectrum antibiotic that is extremely efficient in the treatment of respiratory, abdominal, or genital infections. Vibrational spectroscopic techniques, FT-IR, Raman, and SERS, along with DFT calculations, were involved in investigating the normal modes of vibration and adsorption behavior of this antibiotic. Using both the experimental and theoretical data, the bands in the Raman and IR spectra were assigned to the normal vibrational modes. The SERS spectra were successively obtained by using silver and gold colloidal nanoparticles as a substrate. Their analysis revealed that the molecule is chemisorbed on the nanostructured surface through the as-denoted nitrogen ring. Changes observed in the SERS spectra recorded at different cefoperazone concentrations, i.e., modifications in the relative intensity of specific bands suggest the reorientation of adsorbed molecules towards the metal surface. [ABSTRACT FROM AUTHOR]

Copyright of Fórum pro Konzervátory-Restaurátory is the property of Technical Museum in Brno and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Highlights • SERS is an extremely useful method to detect adsorbed molecules which are covalently bonded to the metallic Ag-NP. • SERS signal of bpy was enhanced by the Ag-NP embedded in the novel niobium phosphate substrate, allowing the detection at the concentration of 10–6 M. • Niobium phosphate containing Ag-NP on their surface is a useful sensor substrate for SERS applications. Abstract Surface-enhanced Raman scattering (SERS) is one of the most sensitive methods for the detection of adsorbed molecules on the nanostructured coinage-metal surface. The enhancements in the order of 104–106 are routinely observed. Such an effect makes SERS spectroscopy a technique applicable to the study the adsorption of analytes in the submonolayer regime. Novel SERS sensors require novel substrates with high activity for great sensibility detection of different molecules applied in many fields, such as detections of narcotics, explosives, and molecules with biological interest. In this work, silver nanoparticles embedded in niobium lead-pyrophosphate glasses (Pb 2 P 2 O 7 -Nb 2 O 5 -Na 2 O) were prepared by ion exchange process, where silver ions were introduced into glass surface by Ag+/Na+ ion exchange (NaNO 3 :AgNO 3 batch), and reduced to metallic silver by heat treatment at glass transition temperature (ca. 480 °C). The new substrate was characterized by Raman spectroscopy, optical absorption, transmission electron microscopy (TEM) and atomic force microscopy (AFM). Its application in SERS was demonstrated by studying the adsorption of 2,2-bipyridine (bpy) on the glass surface, which has marker bands for the coordination of the adsorbate with silver atoms. The optimal surface features in terms of SERS enhancement were also discussed and the sensing ability of this new substrate was demonstrated. [ABSTRACT FROM AUTHOR]

A systematic study was carried out demonstrating that surface concentration is the key factor that must be controlled to overcome the reproducibility problems that has long been haunting surface enhanced Raman spectroscopy (SERS), converting it in a quantitative analytic tool without using any internal standard. The 1,10-phenanthroline molecule (phen) used as model compound can assume different orientations on the surface as a function of surface concentration, but a linear response as a function of concentration was realized in a well-defined range of gold nanoparticles (AuNPs) and phen concentration ratios, allowing to fully explore the very high sensitivity of SERS technique. A detection at a low concentration (5.0 × 10−8 mol dm−3) was achieved controlling the surface concentration in the optimum range where the signals of the species of analytic interest are maximized whilst the signals of all other species are minimized. Copyright © 2017 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Different samples of cellulosic materials were analyzed by Raman spectroscopy and wood chips from Pinus elliottii , treated with acidic and alkaline aqueous solutions, were used to evaluate diagnostic signatures of the chemical structure of the cellulosic fibres. Cotton and whiskers synthesized from cotton, ancient Egyptian linen from a mummy wrapping, and five different paper sheets used in museum handling were compared. The complementarity of the Raman spectroscopic and scanning electron microscopic data facilitated the evaluation of the crystallinity, the level of organization and chain sizes of the fibres and the identification of different oxidation products. Intensity ratios measured from pairs of key bands were used to characterize the crystallinity, chain lengths and presence of oxidative decomposition in the range of the studied samples. Finally, the Raman spectra of the ancient Egyptian linen specimen indicated a potential future application of the proposed analysis for the characterization of archaeological pieces composed of linen. [ABSTRACT FROM AUTHOR]

Water pollution is hazardous to the health of humans and other organisms, and detection of pollutants in aquatic environments is of primary importance for water quality monitoring. Raman spectroscopy offers an effective tool for qualitative analysis and quantitative detection of contaminants in a water environment. This article focuses on applications of Raman spectroscopy for detection of water quality. In this article, various Raman spectroscopy techniques employed for water quality detection are presented based on the types of pollutants: organics, inorganics, and biological contaminants. Additionally, the relevant detection parameters are reviewed, such as detection materials, limit of detection, detection range, peak positions, and selectivity. Furthermore, the advantages and limitations of various Raman spectroscopy techniques are summarized. Finally, the future development of Raman spectroscopy for detection of water quality is discussed. [ABSTRACT FROM AUTHOR]

Perchlorate, which causes health concerns because of its effects on the thyroid function, is highly soluble and mobile in the environment. In this study, diethyldithiocarbamate (DDTC)-modified silver nanoplates were fabricated on a copper wire to perform the on-site microextraction and detection of perchlorate. This fiber could be inserted into water or soil to extract perchlorate through electrostatic interaction and then can be detected by a portable Raman spectrometer, owing to its surface-enhanced Raman (SERS) activity. A relatively stable vibrational mode (δ(HCH)(CH3), (CH2)) of DDTC at 1273 cm−1 was used as an internal standard, which was negligibly influenced by the absorption of ClO4−. The DDTC-modified Ag/Cu fiber showed high uniformity, good reusability and temporal stability under continuous laser radiation each with an RSD lower than 10%. The qualitative and quantitative detection of perchlorate were also realized. A log–log plot of the normalized SERS intensity against perchlorate concentration showed a good linear relationship. The fiber could be also directly inserted into the perchlorate-polluted soil, and the perchlorate could thereby be detected on site. The detection limit in soil reached 0.081 ppm, which was much lower than the EPA-published safety standard. The recovery of the detection was 105% and comparable with the ion chromatography. This hyphenated method of microextraction with direct SERS detection may find potential application for direct pollutant detection free from complex sample pretreatment. [ABSTRACT FROM AUTHOR]

We report on the tuning of the Kondo effect in thin Au films containing a monolayer of cobalt(II) terpyridine complexes by altering the ligand structure around the Co2+ ions by depositing a thin Au capping layer on top of the monolayer on Au by magnetron sputtering (more energetic) and e-beam evaporation (softer). We show that the Kondo effect is slightly enhanced with respect to that of the uncapped film when the cap is deposited by evaporation, and significantly enhanced when magnetron sputtering is used. The Kondo temperature (TK) increases from 3 to 4.2/6.2 K for the evaporated/sputtered caps. X-ray absorption spectroscopy and surface-enhanced Raman spectroscopy investigation showed that the organic ligands remain intact upon Au e-beam evaporation; however, sputtering inflicts significant change in the Co2+ electronic environment. The location of the monolayer-on the surface or embedded in the film-has a small effect. However, the damage of Co-N bonds induced by sputtering has a drastic effect on the increase of the impurity-electron interaction. This opens up the way for tuning of the magnetic impurity states, e.g. spin quantum number, binding energy with respect to the host Fermi energy, and overlap via the ligand structure around the ions. [ABSTRACT FROM AUTHOR]