Search results for "laser"

Molecular structures and vibrations of m-methylaniline in the S0 and S1 states studied by laser induced fluorescence spectroscopy and ab initio calcu…

2000

Abstract The UV fluorescence excitation and dispersed fluorescence spectra of a jet-cooled m-methylaniline have been obtained for the S1←S0 transition, in which some of the bands have been observed for the first time. The main spectral bands have been assigned by comparison with those of other relevant substituted benzenes. It was found that the spectra exhibit an important feature which is the internal rotation of the methyl group in the electronic ground and excited states. Ab initio calculations at MP2/6-31G* and CIS/6-31G* show that the optimized structure of m-methylaniline in the ground state is not planar with the amino group having sp3 hybridation-like character due to the existence…

Development of a Matrix-Matched Sphalerite Reference Material (MUL-ZnS-1) for Calibration of In Situ Trace Element Measurements by Laser Ablation-Ind…

2016

Sphalerite (ZnS) is an abundant ore mineral and an important carrier of elements such as Ge, Ga and In used in high-technology applications. In situ measurements of trace elements in natural sphalerite samples using LA-ICP-MS are hampered by a lack of homogenous matrix-matched sulfide reference materials available for calibration. The preparation of the MUL-ZnS1 calibration material containing the trace elements V, Cr, Mn, Co, Ni, Cu, Ga, Ge, As, Se, Mo, Ag, Cd, In, Sn, Sb, Tl and Pb besides Zn, Fe and S is reported. Commercially available ZnS, FeS, CdS products were used as the major components, whereas the trace elements were added by doping with single-element ICP-MS standard solutions a…

A Metal-Free, Nonconjugated Polymer for Solar Photocatalysis

2017

Heterogeneous catalysts that can absorb light over the solar range are ideal for green photocatalysis. Recently, attention has been directed towards the generation of novel solar-light photocatalysts, in particular, metal-free polymers. Herein, it is demonstrated that a metal-free, nonconjugated, anthraquinone-based copolymer (poly[1,4-diamine-9,10-dioxoanthracene-alt-(benzene-1,4-dioic acid)] (COP)) with a strong absorption in the visible region is effective as a sunlight heterogeneous photocatalyst. As a proof of concept, it has been used to mineralize 2,5-dichlorophenol (2,5-DCP) in water under air and sunlight irradiation. The photocatalytic efficiency of COP compares well with that of …

Selective extraction of small proteins from biological samples using a novel restricted access column with cation exchange properties

2000

The determination of proteins utilising a polymer-based restricted access suppor material with ion exchange properties (IERAM) is outlined. Solid phase extraction coupled on-line with a mincrobore reversed phase HPLC system for the quantitation of small marker proteins is demonstrated. The cation-exchange restricted access packings were characterised with respect to their adsorption and desorption kinetics. The IERAM material was also investigated by capacity, selectivity, and biocompatibility determinations when applied to the quantification of small molecular weight proteins such as cytochrome C, Lysozyme, Ribonuclease A, Myoglobin, Insulin, human serum albumin, and a Tryptic inhibitor.

In-tube solid-phase microextraction coupled by in valve mode to capillary LC-DAD: Improving detectability to multiresidue organic pollutants analysis…

2009

Abstract A simple and fast capillary chromatographic method has been developed to identify and quantify organic pollutants at sub-ppb levels in real water samples. The major groups of pesticides (organic halogens, organic phosphorous, and organic nitrogen compounds), some hydrocarbons (polycyclic aromatic hydrocarbons), phthalates and some phenols such as phenol and bisphenol A (endocrine disruptors) were included in this study. The procedure was based on coupling, in-tube solid-phase microextraction (IT-SPME) by using a conventional GC capillary column (95% methyl–5% phenyl substituted backbone, 80 cm × 0.32 mm i.d., 3 μm film thickness) in the injection valve to capillary liquid chromatog…

Direct surface relief pattering of azo-polymers films via holographic recording

2014

In this work surface relief direct formation during holographic recording in poly (Disperse Red 1 – methacrylate) films was studied. In this material azo-dye Disperse Red 1 is covalently attached to the main polymeric chain making lateral mass transport in the film caused by a presence of light electric field direction modulation very fast and effective. Surface relief grating formation process was induced by 532 nm laser. Read-out was performed by 660 nm diode laser. Diffraction efficiencies kinetics dependence on polarization state of reading and recording beams was studied. Surface relief depth on the films was measured by AFM. Deep surface relief gratings were obtained in Poly (Dispers…

Salt concentration and particle density dependence of electrophoretic mobilities of spherical colloids in aqueous suspension.

2007

Using laser Doppler velocimetry in the superheterodyne mode, we conducted a systematic study of the electrophoretic mobility of dispersions of small silica spheres (a=18 nm) suspended in water at different salinities and particle concentrations. The concentration of NaCl was varied from 40 microM up to 16 mM, while the particle concentrations were varied between 4.2x10(18) and 2.1x10(20) m-3. We find a decrease of mobility with increasing salt concentrations and an increase with increased particle number densities. The latter observation is not backed by the standard cell model of electrophoresis with Shilov-Zharkikh boundary conditions. Rather, if the experimental data are interpreted with…

Structure analysis of acetylated and non-acetylated O-linked MUC1-glycopeptides by post-source decay matrix-assisted laser desorption/ionization mass…

1997

We have investigated the potential of structural elucidation of O-linked glycopeptides by post-source decay matrix-assisted laser desorption ionization mass spectrometry (PSD-MALDI-MS). In order to establish detailed fragmentation patterns and to dissect fragment ions with and without carbohydrate content, the same O-linked MUC1-derived glycopeptides with acetylated and non-acetylated sugars were analysed and compared. Furthermore, we were interested to examine possible differences in the fragmentation between glycopeptides with acetylated and non-acetylated sugars. The obtained PSD-MALDI-MS spectra showed a rather complete set of fragmentation data which allows us to localize the glycan on…

Diastereomeric Differentiation in the Quenching of Excited States by Hydrogen Donors

2003

Quantitative analysis of broad molecular weight distributions obtained by matrix-assisted laser desorption ionisation-time-of-flight mass spectrometry

1996

In order to quantify the error of matrix-assisted laser desorption ionisation (MALDI) time-of-flight (TOF) mass spectrometry in the determination of broad molecular weight distributions, different mixtures by weight of two poly(methyl methacrylate) standards were prepared. These mixtures, with well-defined bimodal molecular weight distributions were analysed by MALDI-TOF mass spectrometry using different matrices (2,4,6-trihydroxyacetophenone and 2,5-dihydroxybenzoic acid) and different cations (Li+, Na+, K+, Rb+ and Cs+) for doping the analyte. From the MALDI-TOF mass spectrometric data, the weight fractions of the two polymers of all mixtures were determined and compared to the values mea…