[Preliminary study on the surface enhanced Raman spectrum of tea].

In the present paper, taking Tiegunyin tea as an example, surface enhanced Raman scattering (SERS) spectrum of tea was obtained, the effects of different active substrates were explored from the aspects of enhanced factor, background noise, repeatability, and signal to noise ratio (SNR), while the impact of adsorption time on the measurement was also discussed. The results show that it is feasible to obtain the SERS spectrum of tea, and Raman signal of SERS spectrum was greatly enhanced compared with that of regular Raman spectrum. The active substrate of silver colloid prepared by the reduction of silver nitrate and trisodium citrate has a better enhanced effect, while different adsorption times have no direct influences on the SERS measurement. The method based on SERS firstly proposed in this paper may provide an alternative method for the discriminant analysis and quality identification of tea.

[Raman spectral analysis of theanine].

The L-theanine was tested using confocal Raman microscopy. Obvious Raman bands were showed in the range of 250 -1 700 and 2 800-3 000 cm(-1). The Raman bands were assigned with a preliminary analysis and the characteristic vibrational modes were gained in different range of wave numbers. Eight strong Raman bands were observed in the Raman spectra at 321, 900, 938, 1 153, 1 312, 1 358, 1 454 and 1 647 cm(-1), respectively. They are the characteristic Raman bands of L-theanine. The results showed that Raman spectroscopy might be a new kind of precise, direct and fast detecting method for theanine.