[Surface-enhanced raman spectroscopy study of vitamin B12 on copper electrode].

The vitamin B12 molecule has long fascinated chemists because of its exclusive complex structure and unusual reactivities in biological systems. In order to achieve a better understanding of the structural attribute of the Vitamin B12 molecule when it interacted with metal, in the present paper, the vitamin B12 molecules adsorbed on variation of copper electrode potential from 0 to -1.0 V was studied by surface-enhanced Raman spectroscopy (SERS). An excellent SERS substrate was obtained with insitu electrochemical oxidation-reduction cycle (ORC), and its surface roughness was characterized by atomic force microscope (AFM). Assignments of Raman peaks observed by normal Raman spectrum (NRS) and SERS spectra of vitamin B12 molecule were given based on previous literatures. It was found that the potential-dependent relative intensity changed in SERS spectra which depended on the vitamin B12 molecular orientation with respect to the copper surface according to the surface selection rule (SSR). It was concluded that the corrin ring was adsorbed in tilt form on copper surface and the Co-CN group was farther away from the copper surface at higher potentials. With the decrease in potential, the tilt angle between the corrin ring and copper surface became smaller, then the Co-N group and 5,6 dimethylbenzimidazole group got close to the copper surface. The results offered an important structural attribute of vitamin B12 molecule when it interacted with copper electrode for the first time, and supplied a meaningful reference for the electrochemical bioactivity of the vitamin B12 molecule.

[Raman, FTIR spectra and normal mode analysis of acetanilide].

The Raman and FTIR spectra of acetanilide (ACN) were measured experimentally in the regions of 3 500-50 and 3 500-600 cm(-1) respectively. The equilibrium geometry and vibration frequencies of ACN were calculated based on density functional theory (DFT) method (B3LYP/6-311G(d, p)). The results showed that the theoretical calculation of molecular structure parameters are in good agreement with previous report and better than the ones calculated based on 6-31G(d), and the calculated frequencies agree well with the experimental ones. Potential energy distribution of each frequency was worked out by normal mode analysis, and based on this, a detailed and accurate vibration frequency assignment of ACN was obtained.

[Thymine on silver island films: surface-enhanced Raman scattering and surface-enhanced infrared absorption studies].

Thymine, being one of the four nucleobases in the nucleic acid of DNA, has received an increasing interest due to its potential importance in genetics and possible applications in medical science. In the present study, adsorption of thymine on laser-ablated silver island films was comparatively analyzed by means of surface-enhanced Raman scattering (SERS) and surface-enhanced infrared absorption (SEIRA). Two new bands at 1305 and 1573 cm(-1) appeared in the SERS spectrum of thymine on silver island films and represented that the molecule configuration of thymine hydrolyzed ion compound changed its structure from a keto form to an enol one. The greater enhancements of in-plane ring breath vibration bands and of 1649 cm(-1) band associated with C(4)==O stretching vibration clearly suggested that the thymine molecules were adsorbed on the silver surface via O(8). The interaction of N(3) with silver surface could be inferred by the emergence of a stronger peak at 773 cm(-1), which was assigned to the ring breath caused by the stretching vibration of the C(6)--N(3)--C(2). The blue shift of ring breath vibration from 749 to 773 cm(-1) indicated that thymine ring should have some weak interaction with silver surface, i.e., there was a certain angle between the thymine ring and the silver surface. To sum up, the SERS spectrum indicated that thymine adsorbed on the silver surface as enolate through the O(8) and N(3) atoms. The molecular plane assumed a tilted orientation with respect to the silver surface. Laser-ablated silver island films also exhibited a good surface enhancement to infrared absorption for thymine. Enhancement factor was estimated to be about 200 under our experimental condition. There was no shift of C(2)==O stretching vibration in SEIRA spectrum, revealing that O(7) was not involved in the adsorption process. Consistent with our SERS spectrum, the greater enhancement of the thymine ring deformation vibration (1730 cm(-1)) in SEIRA agreed a tilted orientation of thymine on silver surface.

[Surface-enhanced Raman scattering spectra of Rh6G adsorbed on Ag nanowire arrays].

The degree of order and uniform of substrates is the key to surface-enhanced Raman scattering study. The structure of porous alumina template by anodic oxidation method is ordered and uniform and the template could be used as the substrate of SERS. Nanowire arrays of Ag were fabricated from the template of porous alumina. The authors observed the SERS signals of the Rh6G adsorbed on the Ag nanowire arrays. The results revealed that the SERS intensity depended on the length of the wires that emerged on the surface that was controlled by the etching time, but the frequency was not affected by the surface condition; the results also revealed that PO4(3-) can increase the intensity of SERS signals.

[Study on the configuration and applications of high spectral resolution Raman spectrometer].

In the present paper the authors studied theoretically and experimentally the relationship between spectral resolution and grating density, the limitations to improve the spectral resolution by using high density grating, the use of longer focal length grating to increase spectral resolution without compromising instrument throughput and the effect of slit width on spectral resolution and sensitivity. Finally, two experiment results were provided to show why higher spectral resolution is important to ensure that critical information is not lost during a Raman measurement. Stressed silicon was produced by growing a thin crystalline layer of Si on an Si(x)Ge(1-x) substrate. It is possible to use Raman spectroscopy to probe the stress in the Si(x)Ge(1-x) and Si layers at the same time. The parameter to monitor the stress is the position of the Si-Si vibrational mode in Si(x)Ge(1-x) and Si. Such a measurement requires high spectral resolution because the peaks exhibit very subtle shifts. The authors' results clearly demonstrate that the resolution offered by a high density grating is necessary to properly monitor the very small frequency shift of this cap-layer Si-Si mode in order to properly characterize the strain structure. The Raman band around 180 cm(-1) is assigned to the radial breath mode of single wall carbon nanotube (SWCN). By measuring the frequencies excited with different laser, the diameters of the sample can be obtained. Practically, sample is always composed of SWCN with different but very close diameters and their Raman bands might overlap together and are difficult to determine the frequencies. The authors' results showed that only higher resolution with the long focal length spectrometer can give accurate number and frequencies of Raman bands, which leads to a correct analysis of the diameter distribution.

[Study on the vibrational spectra of 3,5-dimethoxybenzyl alcohol].

3,5-dimethoxybenzyl alcohol (L1 OH) is a kind of important pharmaceutical intermediate and it is also the starting material of a family of dendrimer LnOH (integer n means the layers of "branch"). A number of articles reported the structure and properties of the L1 OH. However, its molecular vibrational spectra have not been reported up to date. Study of vibrational spectra on L1 OH at the molecular level can provide new information, which is significant for the in-depth study of related molecules of drug and the dendrimer. Recent studies indicated a morphology effect on the light-harvesting functions of dendritic macromolecules. In the present report, the Raman and FTIR spectra of 3,5-dimethoxybenzyl alcohol were measured experimentally. And the density functional theory (DFT) method (B3LYP/6-311G(d,p)) were used to calculate the equilibrium geometry and vibration frequencies of L1 OH. The results showed that the calculated frequencies agree well with the experimental ones. Potential energy distribution of each frequency was worked out by normal mode analysis. Thereafter the authors got a detail assignment of the vibrational frequencies for L1 OH for the first time. Also, the results showed that the DFT is really a useful method in the study of molecular vibrational spectra.

[Study of density functional theory (DFT) for Raman spectra of CH3OLi and CH3CH2OLi].

Molecular configurations of CH3 OLi and CH3 CH2 OLi were structured based on the previous study that lithium atom and oxygen atom are directly joined by O-Li bond in alkoxy lithium (ROLi). Neither experimental nor theoretical Raman spectra of CH3 OLi and CH3 CH2 OLi have been reported up to now. In the present paper, DFT method at the B3LYP/ 6-31G(d,p) level was used to optimize molecular configurations of CH3 OLi and CH3 CH2 OLi, obtaining each corresponding equilibrium configuration. Vibration frequencies and Raman spectra of these two molecules were calculated based on equilibrium configuration. The vibration frequencies of obtained calculated results were analyzed by normal coordinate analysis. Besides, the Raman vibration modes of CH3 OLi and CH3 CH2 OLi were assigned according to potential energy distribution of each vibration frequency, which will provide theoretical basis for experimental workers to analyze the components of solid electrolyte interface film (SEI film) of lithium ion battery.

[Preparation of palladium nanoparticles by laser ablation and its spectral properties study].

Palladium colloid was obtained via laser ablation under 1064 nm excitation from an Nd:YAG laser in redistilled deionized water. The Pd colloid consisted of "chemically pure" Pd nanoparticles, which were free from extraneous ions or other chemicals since no chemical reaction was involved in the preparation. There was no characteristic peak in UV/Vis spectrum of Pd colloid in the region of 200-800 nm. Hence, in contrast to the Au and Ag nanoparticles, the average size and the size distribution of the Pd nanoparticles could not be estimated from their UV/Vis adsorption spectral features. After the laser ablation, one drop (50 microL) of Pd colloid was deposited on the aluminum plate and dried naturally to form the Pd island films. This method resulted in the formation of a rough surface with a large number of separated Pd islands 20 microm in diameter. According to the SEM measurement, Pd nanoparticles with the average diameter of approximately 200 nm formed Pd island films. Surface-enhanced Raman scattering (SERS) activity of Pd colloid and Pd island films was evaluated by using 4-mercaptopyridine (4MPY) as a probe molecule. The SERS study revealed that Pd island film was a highly efficient SERS-active substrate while there was no SERS signal observed from Pd colloid. The surface enhancement factor of Pd island films for 4MPY was estimated, which could reach values as high as 8. 7 X 10(4) under 632.8 nm excitation. This value was comparable with the largest value of 10(4) cited in the literature. The SERS spectra of 4MPY molecules adsorbed on Pd surface showed that 4MPY molecules probably tilted from the Pd nanoparticle surface-via sulphur. By contrast, SERS spectrum of 4MPY adsorbed on Ag island films was recorded and analysed. From SERS data it was inferred that 4MPY molecules assumed the standing up orientation on the silver nanoparticle surface. It could be concluded that the 4MPY molecules were more perpendicular to the silver nanoparticle surface than to the Pd nanoparticle surface.

[Study on vibrational spectra of ethyl hexanoate molecule].

The vibrational spectra of ethyl hexanoate were calculated by the density functional theory (DFT) with B3LYP complex function, diffuse function and polarization function added to heavy atoms and light atoms. On the base of this, the normal Raman spectrum (NRS) and the infrared spectrum (IR) were assigned in detail in the present paper. Comparing the calculated results with the experimental data, the calculated results are in good agreement with the experimental results. The comparison of the experimental Raman and infrared spectra shows that in the experimental Raman spectrum, the strongest bands appear at the frequencies of 2600-3100 cm(-1), while the strongest band is not 1734 cm(-1) but 1444 cm(-1) at the frequencies of 400-2000 cm(-1). The band 1734 cm(-1) attributed to the C=O stretch vibration is the distinctive mark of organic ester compounds, and the band 1444 cm(-1) is related to the symmetric and anti-symmetric scissors vibration of C-H. In the experimental infrared spectrum, the strongest vibrational band is 1739 cm(-1), which is related to C=O stretch vibration; At the frequencies of 400-2000 cm(-1), the relative intensity of the infrared spectrum is distinctively stronger than that of the Raman spectrum, but the relative intensity of infrared spectrum is weaker than that of the Raman spectrum at the frequencies of 2600-3100 cm(-1). In the frequencies of 2600-2800 cm(-1), the vibrational bands 2762 and 2732 cm(-1) do not appear in the experimental spectra, which may originate from two reasons: (1) the weak interaction of molecules. Also, the relative intensity of these vibrational bands is very weak in the experimental spectra, and this may testify that the interaction of molecules is rather weak; (2) the vibrational bands may belong to second order vibrational mode at the frequencies of 2600-2800 cm(-1). The relative intensity of infrared bands is weaker than that of the Raman bands at the frequencies of 2600-2800 cm(-1). At the end, the stronger bands appearing in Raman and infrared experimental spectra are assigned as characteristic marks, respectively. The study on vibrational spectra of ethyl hexanoate molecule may have great application value in detection of liquor flavor, chemical industry and biology fields, providing important reference value for the related basic research field.

[Surface enhanced Raman scattering spectra of carbozole and azobenzene disperse red polymer].

Surface enhanced resonance Raman scattering (SERRS) was employed to study the molecule alignment of carbozole and azobenzene disperse red polymer on the surface of rough silver thin film. According to the selection rule of optical transitions and experiment results, it was found that the surface geometry of carbozole and azobenzene disperse red polymer was: this was physical adsorption between the carbazole group, which is from the monomer of carbazole and nitro-group which is from the monomer of azobenzene on the surface of rough silver film, and there is almost no interaction between the principal chain and the substrate because of the distance. This geometrical configuration of CAP on the surface of the substrate was proposed to damage the stabilities and efficiency of azobenzene derivatives based optical storage devices.