Feasibility investigation on deep ocean compact autonomous Raman spectrometer developed for in-situ detection of acid radical ions

A newly developed Deep Ocean Compact Autonomous Raman Spectrometer （DOCARS） system is introduced and used for in-situ detection of acid radical ions in this paper. To evaluate the feasibility and capability of DOCARS for quantitative analysis of the acid radical ions in the deep ocean, extensive investigations have been carried out both in laboratory and sea trials during the development phase. In the laboratory investigations, Raman spectra of the prepared samples （acid radical ions solutions） were obtained, and analyzed using the method of internal standard normalization in data processing. The Raman signal of acid radical ions was normalized by that of water molecules. The calibration curve showed that the normalized Raman signal intensity of SO4^2-, NO3^-, and HCO^-3 increases linearly as the concentration rises with correlation coefficient R^2 of 0.99, 0.99, and 0.98 respectively. The linear function obtained from the calibration curve was then used for the analysis of the spectra ,data acquired in the sea trial under a simulating chemical field in the deep-sea environment. It was found that the detected concentration of NO3 according to the linear function can reflect the concentration changes of NO~ after the sample was released, and the detection accuracy of the DOCARS system for SO^2-_4 is 8%. All the results showed that the DOCARS system has great potential in quantitative detection of acid radical ions under the deep-sea environment, while the sensitivity of the DOCARS system is expected to be improved.

PRODUCTION OF HIGHLY GRAPHITIZED MULTIWALlED CARBON ANOTUBES

Multiwalled carbon nanotubes ( MWNTs) were prepared by DCarc dischargein hydrogen gas, and werethermally purified byinfrared radiation in air. The morphology of pristineand purified MWNTs was observed by scanning electron microscope ( SEM) , and the crys tallinestructureand perfection wereinvestigated by high resolution transmission electron mi croscope( HRTEM) and Raman spectrometer. Itcameto the conclusion thatthese MWNTs possessed a high degreeof graphitization and very narrow centralchannel(about1 0 nm indiameter) , giving risetotheappearanceof breathing modesfor MWNTs.

Raman spectroscopic detection using a two-dimensional echelle spectrometer

In order to meet the high-resolution and wide spectrum range of the backscattering Raman system, this paper designs and builds a Raman test system based on the echelle spectrometer. In the optical splitting system, compared with the ordinary planar grating spectrometer, the use of the echelle improves the resolution of the system without increasing the volume of the system. The use of intensified charge-coupled device(ICCD) in the detection system improves the signal-to-noise ratio(SNR) and the detection limit of weak spectrum. Finally, the Raman system was spectrally calibrated. The broadband backscattering Raman experimental results are given and discussed. The experimental results show that the system has an excellent application prospect for broadband and high-resolution Raman spectrum measurement.