[Raman Spectroscopy Measurement System of Dual Wavelength Laser Module].

Fluorescence interference is one of common interference factors during detection of Raman spectroscopy, while shifted-excitation Raman difference spectroscopy (SERDS) is an effective detection means to reject it. SERDS excites the test substance by two laser with different wavelengths, then difference the obtained Raman spectroscopies. SERDS can eliminate the fluorescence interference effectively, because the fluorescence backgrounds of the two spectroscopies are the same while the Raman peaks are translated. The key factor of SERDS is the stability of the two excitation light wavelengths, the instability of wavelength difference would seriously affect the characteristics of the Raman peak reproduction. In this paper, the Raman spectroscopy measurement system is presented, where dual wavelength laser module can stably produce two bunch of excitation light (respectively 784.7 and 785.8 nm), which satisfies the requirements of SERDS detection. The major factors influencing wavelength of the laser are laser power and temperature. The system monitors them in real time to guarantee the stability of exciting light's wavelength. The hardware framework of this measurement system is mainly composed of ARM, dual wavelength laser module as well as its driving circuit, temperature control circuit, a digital optical switch, a spectrometer; the software of this system can achieve the Raman spectrogram automatically and then carry on the subsequent processing. The stability tests of this system for drive current and laser temperature are done. The experimental results demonstrate that the range of current proves to be less than 0.01 mA, the range of temperature less than 0.004 degrees C. The system can guarantee the stability of excitation wavelength effectively. Finally, perform the Raman spectroscopy detection to sesame oil of some brand and get good results.

An extremely stable and sensitive end-column electrochemical detector based on heated copper microdisk electrode with direct current for CE and CE-Chip.

A heated copper microdisk electrode (HCME) was fabricated and successfully applied to capillary electrophoresis (CE) and CE-Chip as an electrochemical detector (ECD) for the detection of three carbohydrates and shikimic acid (SA) in Illicium verum Hook F., respectively. The temperature of HCME was heated by twin-wire-wound coil with direct current to reduce the magnetic interference. Coupled with CE and CE-chip, this detector exhibits both extremely stable and sensitive performance at elevated temperature compared with that at room temperature. In successive detection of three carbohydrates and shikimic acid (SA), the HCME exhibits very stable response with RSD of ca. 2% with elevated temperature without renewing the electrode, while at room temperature, RSD of ca. 20% is obtained. This is very important in practical applications that tedious works, such as polishing and re-fixing the electrode at each detection, can be therefore avoided. In addition, the sensitivity is about 2-6 time increased, and the linear range is about an order wider at elevated temperature (ca. 60 degrees C) than that at room temperature (ca. 25 degrees C).

Surface analysis using shell-isolated nanoparticle-enhanced Raman spectroscopy.

Surface-enhanced Raman scattering (SERS) is a powerful fingerprint vibrational spectroscopy with a single-molecule detection limit, but its applications are generally restricted to 'free-electron-like' metal substrates such as Au, Ag and Cu nanostructures. We have invented a shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS) technique, using Au-core silica-shell nanoparticles (Au@SiO(2) NPs), which makes SERS universally applicable to surfaces with any composition and any morphology. This protocol describes how to prepare shell-isolated nanoparticles (SHINs) with different well-controlled core sizes (55 and 120 nm), shapes (nanospheres, nanorods and nanocubes) and shell thicknesses (1-20 nm). It then describes how to apply SHINs to Pt and Au single-crystal surfaces with different facets in an electrochemical environment, on Si wafer surfaces adsorbed with hydrogen, on ZnO nanorods, and on living bacteria and fruit. With this method, SHINs can be prepared for use in ~3 h, and each subsequent procedure for SHINERS measurement requires 1-2 h.

Highly sensitive detection of silybin based on adsorptive stripping analysis at single-sided heated screen-printed carbon electrodes modified with multi-walled carbon nanotubes with direct current heating.

A new disposable multi-walled carbon nanotubes modified single-sided heated screen-printed carbon electrode (MWNT/ss-HSPCE) was fabricated. The electrochemical behavior of silybin was investigated by cyclic voltammetry and the probable electrode reaction mechanism was proposed. A simple and cheap direct current heating supplier was used to heating the electrode for adsorptive accumulation of silybin. The square wave voltammetric stripping peak current of silybin at MWNT/ss-HSPCE with an elevated electrode temperature of 50°C only during accumulation step was dramatically improved compared with that at bare single-sided heated screen-printed carbon electrode (ss-HSPCE) without heating. This enhancement was mainly contributed to the combination of the advantages of multi-walled carbon nanotubes and electrically heated electrodes. Under optimum conditions, two detection linear ranges of silybin were from 1.0×10(-9) to 1.0×10(-7) M and 3.0×10(-7) to 1.0×10(-6) M. A detection limit of 5.0×10(-10) M could be obtained (S/N=3), which was more than two magnitudes lower than that at bare ss-HSPCE without heating. To the best of our knowledge, this was also at least two magnitudes lower than any others for electrochemical detection of silybin in the literature. Finally, the method was successfully applied to the determination of silybin in pharmaceutical tablets.