ISSN:0377-0486    

DOI:10.1002/jrs.1250221202

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractThis review summarizes the literature relating to the application of surface‐enhanced Raman scattering (SERS) and surface‐enhanced resonance Raman scattering (SERRS) techniques to the study of biological molecules. The emphasis is on publications that have appeared during the period from 1985 to 1991. The review is divided into six major parts. First, a brief overview of the current understanding of the mechanistic aspects of SERS/SERRS is given, with an emphasis on the relationship between theoretical predictions and experimental results. The most common experimental systems (colloids, metal island films, and electrodes) are described. Studies of biological systems are described in the second (small molecules), third (DNA and proteins) and fourth (membranes proteins and membrane preparations) sections. In the fifth or conclusion section, the potential use of SERS or SERRS as a method for obtaining spectra of native biological molecules is evaluated. Finally, the sixth section describes advances in Raman instrumentation in terms of their possible impact on future applications of SERS/SERRS techniques to biological molecu

ISSN:0377-0486    

DOI:10.1002/jrs.1250221203

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractThis review concentrates on the electronic contribution to surface‐enhanced Raman scattering (SERS). This socalled ‘chemical effect’ is quantitatively separated from classical electromagnetic enhancement. It proceeds by increased electron‐photon coupling at an atomically rough surface and by temporary charge transfer to adsorbate orbitals. These concepts are supported by various experimental results. The model accounts for the chemical specificity and vibrational selectivity of SERS and (partly) for the ‘SERS specificity’ of var

ISSN:0377-0486    

DOI:10.1002/jrs.1250221204

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractSurface‐enhanced resonance Raman scattering (SERRS) spectra were measured at O V (vs Ag/AgCl) for a hemicyanine dye and its protonated form (HC and HCH+) adsorbed on a silver electrode surface. The surface spectrum of HC shows a characteristic feature due to atransconformation, a band mainly due to a stretching frequency (νcc) at 1580 cm−1, which is appreciably lower than the corresponding frequency for HC in water (1592 cm−1); this result indicates that, on adsorption on the electrode surface, the resonance balance of HC between the quinoid and benzenoid forms shifts to the former. An adsorbate on a silver electrode surface from HCH+solution at pH 1.0 takes either a protonated form, HCH+, or a deprotonated form, HC, depending on the anodization conditions of granular structures assumes the deprotonated form, whereas the adsorbate on a surface containing smooth parts retains the protonated form; hence the surface morphology is related to the chemical properties of the silver electrode surfaces. It was also found that the adsorbate in the protonated state gives a prominent SERRS band at 885 cm−1assignable to an out‐of plane bending vibration of the central olefinic group, indicating that the adsorbate assumes a flat orientation on the silver elect

ISSN:0377-0486    

DOI:10.1002/jrs.1250221205

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractBy combining a high‐sensitivity charge‐coupled device detector with the total reflection technique, Raman spectra in the CH stretching region were recorded for thin Langmuir‐Blodgett (LB) films of dipalmitoylphosphatidylcholine (DPPC) prepared at various surface pressures encompassing the plateau region of its surface pressure‐area isotherm. Surface‐pressure dependences of the lateral packing and the conformational order are discussed using the peak intensity ratio between the 2880 and 2850 cm−1bands and that between the 2935 and 2850 cm−1bands. The results indicate that at higher surface pressures above the plateau, the hydrocarbon chains of DPPC are tightly packed and highly oriented with the all‐transconformation. Below the plateau, however, the chains are disordered because of the increased number of thegaucheconformers. The loosely packed hydrocarbon chains observed for the LB films deposited at lower surface pressures are gradually reoriented with time to form stable and highly ord

ISSN:0377-0486    

DOI:10.1002/jrs.1250221206

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractSurface‐enhanced Raman scattering (SERS) excited at several visible wavelengths and recorded using a cooled charged‐coupled device detector is reported from the mobile, interfacial, liquid‐like metal films (MELLFs) formed when solutions of metal complexes or pyridine in chlorocarbon solvents are mixed with aqueous sols of silver or gold. MELLF formation has not previously been reported for gold sols or for pyridine as stabilizer. Comparison of the spectra for the MELLFs formed from individual metal complexes and from 50:50 mixtures show that the spectral patterns observed for the latter are distinctive and are not generally equivalent to the sum of the spectra associated with the individual complexes, in contrast to the situation observed for sols where the individual spectra do appear to be additive. Raman scattering from both gold and silver MELLFs is readily observed at excitation wavelengths in the red, around 750 nm, but at 514 nm only that from silver films is detectable. These findings are considered in terms of particle size and absorption band intensities. A preliminary study of the film surface topography and particle size was carried out by scanning tunnelling electron microscopy (STM) of Ag MELLFs deposited on gold‐coated mica substrates. Computer‐processed images of the STM data show the presence on the film surface of finger‐like bars, 200–400 nm long with approximately square cross‐section, 40–60 nm side, together with other smaller cuboid features. The implications of these findings in relation to SERS are b

ISSN:0377-0486    

DOI:10.1002/jrs.1250221207

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractSurface‐enhanced Raman scattering (SERS) from citrate‐coated colloidal particles suspended in organic solvents is used to study surface reactions in an organic phase. Stable colloids which gave good SERS were produced from ethanol and acetonitrile. SERS was easily discriminated from the bulk solvent Raman scattering. Compounds which are sparingly soluble in water including 2,2′‐bipyridine and benzene‐1,2,4,5‐tetracarboxylic acid dianhydride produced good SERS in ethanol. In the latter case, no SERS was observed from an aqueous colloid. Therefore, some form of solvent‐dependent molecular recognition may operate. The formation of a bipyridine complex with copper(II) at the surface in a solvent system in which the ligand and complex are both soluble was observed. The solvent altered surface reactions. In the ethanol colloid, in contrast to the result in aqueous colloid, pyridine does not replace citrate readily. This work demonstrates the potential for the expansion of the use of colloidal SERS into the field of surface reactions in contact with an organic phase and is related to metal liqu

ISSN:0377-0486    

DOI:10.1002/jrs.1250221208

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractRaman spectroscopy due to electric fields at surfaces, which manifests itself as surface‐enhanced Raman scattering (SERS) from adsorbate modes, and as electric field‐induced Raman scattering (EFIRS) from substrate modes, is discussed. In SERS experiments with benzene adsorbed on small Ni/SiO2and Pt/SiO2clusters, using exciting radiation of different wavelengths, we observed not only very strong peaks of the normally Raman active vibrational modes but also normally infrared‐active and some inactive modes. Although the frequencies of the modes are only slightly shifted with respect to liquid benzene, the relative intensites of the Raman lines are considerably changed and in addition they are dependent on the excitation wavelength. The observation of metal‐carbon vibrations indicates a strong interaction between the adsorbate and the metal atoms. Therefore, in addition to the electric field, a metal‐molecule electronic charge transfer may be responsible for the enhancement mechanism.EFIRS is based on the symmetry‐forbidden scattering from the longitudinal optical (LO) substrate phonon. It allows the detection of the static electric field in the surface region of semiconductor substrates, which originates from electronic band bending. By EFIRS the band bending can be monitored at surfaces and interfaces for coverages from submonolayer up to more than 100 monolayers, depending on the overlayer material. Here, the Sb/GaAs(110) interface is treated as an example. Considerable band bending dynamics is observed for overlayer thicknesses up to 100 monolayers. Simultaneous analysis of the overlayer structure by Raman scattering from the Sb vibration modes allows the interpretation of the band bendi

ISSN:0377-0486    

DOI:10.1002/jrs.1250221209

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractLangmuir‐Blodgett (LB) monolayers of dysprosium and holmium bisphthalocyanine complexes (DyPc2and HoPc2) were prepared at 10°C and transferred to glass slides coated with gold island films. Surface‐enhanced resonance Raman scattering (SERRS), and visible absorption spectrometry were used to monitor the interaction between the LB monolayer and NOx(NO2‐N2O4) gas. It is shown that the absorption and inelastic scattering spectra of LB are sensitive tools to monitor the interaction between the MPc2molecule and the NO2, allowing the spectral properties of the adduct formed by chemisroption to be dete

ISSN:0377-0486    

DOI:10.1002/jrs.1250221210

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractThe behaviour of adenine and 2′‐deoxyadenosine‐5′‐monophosphate (dAMP) at positive surface potentials of a silver working electrode was investigated using surface‐enhanced Raman scattering (SERS). The use of positive potentials in the presence of adenine or dAMP leads to a rapid accumulation of an intense spectrum. It is proposed that complexes of adenine (dAMP) with silver generate the observed spectra. Adenine and dAMP can be distinguished spectroscopically due to various different complexes that can be formed for adenine and not for dAMP. The SERS spectra of the silver‐adenine complexes show broad, unresolved bands between 1200 and 1500 cm−1, while the spectra of complexes of silver with dAMP show clearly resolved bands. The formation of Ag+‐adenine complexes gives rise to a decrease in pH and must therefore be associated with deprotonation of the adenine ring system. The SERS spectra of adenine can be obtained in solutions with a pH of 3.0, 7.5 and 11.0 whereas the SERS spectra of dAMP can only be obtained at a pH of 7.5 and 11.0. The time dependence of the SERS spectra of dAMP suggests that at least two different complexes of silver with dAMP are involved. The observed spectra are completely different from the ‘classical’ SERS spectrum of adenine and dAMP. This spectrum is characterized by an intense band at 729 cm−1(at –700 mVvs. SCE). At open loop potential, however, the spectra of the Ag‐dAMP complex change slowly to the ‘cla

ISSN:0377-0486    

DOI:10.1002/jrs.1250221211

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY