Seiichiro Higuchi

Some considerations of the SERS effect of L‐phenylalanine in the near‐infrared region using silver colloid solution

The surface-enhanced Raman scattering (SERS) spectra of L-phenylalanine were examined in the near-infrared region using silver colloid solutions. It was shown that near-infrared SERS (NIR-SERS) was not detected for L-phenylalanine in a normal silver colloid solution, whereas in the visible region a distinct SERS intensity enhancement was realized for such sample systems. In the present study, this situation was considered from the viewpoint that the degree of aggregation of colloid particles necessary to cause the SERS effect is different between visible and near-infrared radiation. In this work, silver colloid solution containing dissolved L-phenylalanine was dropped on to a filter-paper and this filter-paper sample was then dried. It was confirmed by SEM (scanning electron microscopy) that as a result of this sample preparation, the degree of aggregation of colloid particles increased considerably. It was shown that the near-infrared SERS was detected with high sensitivity for L-phenylalanine adsorbed on silver particles condensed on filter-paper. From consideration of the magnitudes of the SERS intensity enhancement in this case, it is suggested that the mechanism of NIR-SERS for the present sample system is the electromagnetic effect, related to the excitation of surface plasmons (the surface plasmon polariton mechanism).

Identification and Determination of Oxygen-Containing Inorganosulfur Compounds by Laser Raman Spectrometry

A new method for the analysis of oxygen-containing inorganosulfur compounds was developed utilizing laser Raman spectrometry. The Raman spectra in the 1400–200 cmcm−1 region was observed for nine different oxygen-containing inorganosulfur compounds dissolved in aqueous solutions and in the solid states. The Raman spectra of these compounds exhibited the characteristic spectral features for oxygen-sulfur inorganic compounds. The relation between the Raman frequencies and the chemical structures of the compounds is discussed in terms of characteristic group frequencies analysis and structural parameters. A table of these characteristic Raman bands and the quantitative aspects for the determination for some of these compounds in aqueous solution are also reported. With the use of the thiocyanate ion as an internal standard, the relation between the peak intensities and concentrations of the compounds exhibited good linearity. It is also found that simultaneous determination of several different compounds is possible. The laser Raman spectroscopic method is shown to be very useful for the structural analysis, identification, and determination of these compounds in solid states and in aqueous solutions.

Determination of small amounts of some sulfonamide drugs by resonance raman spectrometry

Abstract Resonance Raman spectrometric determinations of eight sulfonamide drugs are discussed. All the samples were colorless and exhibited no resonance Raman effect with argon ion laser excitation. After conversion to colored derivatives by diazotization and coupling reactions of the aromatic primary amine moiety, the sulfonamides could be determined from their resonance Raman spectra; the detection limits were about 2 × 10 -3 M. However, the method cannot be used for identification of the individual drugs because the spectra obtained exhibited exactly the same spectral features. In order to obtain characteristic spectra, color development for the R—NH 2 molecule produced by hydrolysis of the sulfonamide with hydrochloric acid was examined. Three of the samples tested (sulfathiazole, sulfisoxazole and sulfisomezole) gave colored derivatives by a common chemical reaction system; the resonance Raman spectra then obtained exhibited characteristic spectral patterns.

Examination of the Photochemical Curing and Degradation of Oil Paints by Laser Raman Spectroscopy

In the present study, the curing and the degradation of oil paints by irradiation with ultraviolet light was investigated by laser Raman spectroscopy. At present, the curing reaction of oil paints is interpreted by several reaction schemes, although none of them is considered to be based on definite experimental evidence. The most typical examples are as follows: one is the radical termination reaction of the crosslinking type; the other, the polymerization reaction of the Diels—Alder reaction (diene reaction) type. In the present investigation, oil paint film (ZnO White and TiO2 White) was irradiated with a Xe lamp, and the time dependence of the Raman spectra of the films was examined. It is shown that the curing reaction cannot be explained by either of the above-mentioned reaction schemes. A new reaction mechanism for the curing and the degradation of paint films is proposed. It is concluded that the microscopic approach to the elucidation of the degradation mechanism of oil paint films based on Raman spectroscopy is very useful for the improvement of oil painting techniques.

Raman scattering intensities of the NO2 symmetric stretching vibration band of some aromatic nitrocompounds (II)

Abstract Raman scattering intensities of the NO2 symmetric stretching vibration band were measured for some aromatic nitrocompounds. It was shown that in the case of ortho alkyl-substituted nitrobenzenes, the intensities decrease in an orderly fashion with the increase of the degrees of twisting of NO2 group from the plane of benzene ring. From this result, it was assumed that the factor determining the intensities in question is the conjugation effect between NO2 group and benzene ring. Then, the intensities for some para substituted nitrobenzenes were examined, and the influence of substituents was discussed in terms of the conjugation effect. It was shown that when the electron donating character of substituents becomes stronger, the intensities intensity change among the compounds. The more experimental data and the detailed theoretical analysis of them are necessary not only for the elucidation of spectroscopic aspects of the intensity in question, but also for establishing the criterion for the appl...

Comparative Investigation on the Concentration-Dependences of the Half-Band Widths of Infrared Absorption and Raman Bands

Abstract It is demonstrated that the fashions of the concentration-dependences of half-band widths are markedly different between the corresponding bands in i.r. absorption and Raman spectra when the i.r. absorption intensities of the bands are extremely large. On the other hand, when the i.r. intensities are not so great, the similar behaviour is observed for the changes in the half-band widths. In this study, these phenomena have been discussed in terms of the vibrational relaxation of resonance type and the local field effect.

Raman circular intensity differential spectra of some chiral compounds with related structures

Abstract Raman circular intensity differential spectra of certain dialkyl tartrates and two series of compounds with a bicyclic ring or a menthane ring, respectively, are presented. The relation between the R-CID signals and the structural features of these compounds are discussed.

Surface enhancement effect on the diffuse reflectance infrared Fourier transform spectra of compounds having a pyridine ring

Abstract A surface enhancement effect was examined for the diffuse reflectance infrared spectra of structurally related compounds having a pyridine ring when a silver colloidal solution was used as the medium which induced the effect. Filter paper, which was considered to provide a favorable state of aggregation of the silver colloidal particles, was used for the preparation of the samples to be measured. It was proved experimentally that when the molecules were dissolved in the silver colloidal solution and the resulting solution was applied dropwise to filter paper, the spectra measured for the filter paper sample exhibited a surface-enhanced infrared absorption (SEIRA) effect for some samples, but not for other samples. It was speculated that the existence of an electron-donating functional group in the molecule was necessary for the realization of SEIRA in the diffuse reflectance infrared spectra. This speculation was confirmed by experiments involving other types of molecules: l -phenylalanine, m -aminophenol and p -chloroaniline.

Microanalysis of some carcinogenic polycyclic aromatic nitrocompounds by preresonance Raman spectrometry.

大気浮遊粒子中に含まれ,有機溶媒可溶成分として抽出される多環芳香族ニトロ化合物は発がん性が極めて強い.本研究では,この種の化合物について前期共鳴ラマン法による微量分析的検討を行った.試料からの強い蛍光によるバックグラウンドについては,四塩化炭素溶液の場合,レーザー光照射による消光が非常に有効であった.各スペクトルは共鳴ラマン効果による強度の増大を受けた強いバンドについて十分な選択性を示す.感度については,10-6Mのオーダー(数百ppb)の検出限界が得られたが,これが更に低い場合も見いだされた.更に,スペクトルは広い濃度範囲で定量性があることが示された.これらの結果は,前期共鳴ラマン法がこの種の化合物の環境科学的検討に十分な有効性をもつことを示唆するものと結論される.

Magnetic Circular Dichroism Spectra of p-Disubstituted Benzenes Possessing Both Electron-Donating and Accepting Groups

Abstract The magnetic circular dichroism (MCD) and absorption spectra of some p-disubstituted benzenes possessing both electron-donating and accepting groups were measured. The electronic spectra of the above compounds are characterized by the appearance of two absorption bands, one of which appears at 25000–40000 cm−1 region with large intensity, and another at 40000–50000 cm−1 region with rather small intensity. These absorption bands, especially the latter one, have been investigated by means of the MCD spectra and molecular orbital calculations based on the Pariser-Parr-Pople method.