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首先,本实验中采用的两种基底对附子溶液样品均有增强作用,都出现了附子成分的特征峰,证明了本实验中采用的两种SERS基底都可以对样品进行增强。由于纯基底本身也存在着喇曼光谱,具有一定的峰强,所以SERS基底的增强效果主要体现在特征峰峰强I的增量ΔI上,其值等于SERS谱的峰强减去纯基底峰强。
其次,本实验中根据两种基底的不同特性,采用了不同的激光功率:TiO2-AgNPs薄膜采用的激光功率为1%,银胶纳米颗粒溶液采用的激光功率为10%。喇曼光谱的特征峰强可近似与激光功率的平方成正比[16]。已知两种基底采用的激光功率比值的平方为:
$ \begin{array}{l} {\left( {\frac{{{\rm{TiO_{2}-AgNPs薄膜采用的激光功率}}}}{{{\rm{银胶纳米颗粒溶液采用的激光功率}}}}} \right)^2} = \\ {\left( {\frac{{1\% }}{{10\% }}} \right)^2} = \frac{1}{{100}} \end{array} $
(1) 这说明两种不同基底所得的SERS中,同一喇曼位移处的峰强若相同,则TiO2-AgNPs薄膜基底的增强敏感度为银胶纳米颗粒溶液的100倍。
由于不同的基底具有不同的荧光干扰强度,所以本文中通过比较同一基底的SERS中的不同喇曼位移的相对峰强比,来定性地分析两种基底的增强效果。
$ \Delta I=\frac{I_{\mathrm{n}}-I_{\mathrm{s}}}{I_{{\mathrm{s}}}} \times 100 \% $
(2) 在附子溶液样品以TiO2-AgNPs薄膜基底与银胶纳米颗粒溶液基底进行表面增强所获取的喇曼光谱中,选取一个喇曼位移为732cm-1的特征峰作为基准,其特征峰峰强Is分别为47238和22657,再选取一个喇曼位移1398cm-1(此处为葡萄糖/葡萄糖醛酸化学键的喇曼位移)的特征峰作为对比峰,峰强In分别为60394和25368。带入(2)式中计算可得喇曼位移1398cm-1的相对峰强比,TiO2-AgNPs薄膜基底为27.85%;银胶纳米颗粒溶液基底为11.97%。
通过上述两个方面可以定性地分析出:TiO2-AgNPs薄膜作为SERS基底在本实验中对中药成分附子的增强效果更为明显,这与在血清溶液中的实验结果相同[16]。
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在相同的测试条件下,TiO2-AgNPs薄膜基底的测试手段更加容易。然而TiO2-AgNPs薄膜基底的制备过程复杂,且容易氧化、稳定性差,加之中药样品中成分的腐蚀和氧化作用更明显,导致基底的可用时间非常短。因此,TiO2-AgNPs薄膜基底更适合于高精度、小数量的中药溶液样品成分鉴定。
银纳米溶胶溶液基底在实验中需要吸入玻璃毛细管中进行喇曼散射,要寻找适合的银胶汇聚点进行对焦,对实验者操作的技巧要求较高。但银纳米溶胶溶液基底的制备相对较容易,具有稳定性高、易于保存、不容易氧化变质等优点。如果储存适当可用时间相对较长,制备一次可以用于大量样品的多次测量。虽然银纳米溶胶溶液基底的增强效果弱于TiO2-AgNPs薄膜基底,但其增强效果已经十分明显,可以满足一般情况的成分确定。因此,其更适于易氧化、数量大的中药溶液样品成分鉴定。
由实验可知,对于中药溶液样品,可根据实验的不同要求选择不同的SERS基底获取表面增强喇曼散射光谱,确定样品成分。
两种基底对中药溶液喇曼光谱增强作用的比较
Comparison of surface-enhanced Raman spectroscopy of traditional Chinese medicine solution induced by two substrates
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摘要: 为了对比分析TiO2-AgNPs薄膜与银胶纳米颗粒溶液两种表面增强喇曼光谱散射(SERS)基底对中药溶液样品的SERS增强效果,选取中药附子溶液作为实验样品,分别采用两种SERS基底通过喇曼散射实验取得其表面增量喇曼光谱,并进行了解析对比。结果表明,TiO2-AgNPs薄膜与银胶纳米颗粒溶液两种SERS基底都对中药附子溶液的喇曼散射光谱起到了明显的增强作用;TiO2-AgNPs薄膜的增强效果相对于银胶纳米颗粒溶液更为敏感,如在喇曼位移1398cm-1的相对峰强比,TiO2-AgNPs薄膜基底为27.85%,银胶纳米颗粒溶液基底为11.97%,但其具有易氧化、可用时间短、制备难度大、可重复性不高等缺点,因此更适于样品成分的精确鉴定,银胶纳米颗粒溶液具有制备更简单、使用时间长、稳定性和重复性好等优点,适于大量样品成分确定对比的检测;两种基底对中药溶液样品的SERS增强各有优势。此结果对国内外利用SERS技术分析中药有效成分的基底选择有一定参考作用。Abstract: In order to compare and analyze the enhancement effect of surface-enhanced Raman spectroscopy (SERS) by two substrates of TiO2-AgNPs thin film and silver sol nanoparticles solution on the samples of traditional Chinese medicine solution, aconite solution was selected as the experimental sample and surface enhancement Raman spectra of two substrates were obtained after Raman scattering experiment. The analytical comparison was made. The results show that, Raman scattering spectra of aconite solution are enhanced by two SERS substrates of TiO2-AgNPs film and silver sol nanoparticle solution. The enhancement effect 1398cm-1 of TiO2-AgNPs thin film is more sensitive than that of silver sol nanoparticles. For example, relative peak-to-intensity ratio at Raman shift of TiO2-AgNPs thin film is 27.85% and that of silver sol nanoparticle solution is 11.97%. However, TiO2-AgNPs thin film has disadvantages of easy oxidation, short usage time, difficult preparation and low repeatability. Therefore, it is more suitable for the accurate identification of sample components. Silver sol nanoparticle solution has advantages of simpler preparation, longer use time, good stability and repeatability. It is suitable for the determination and comparison of a large number of samples. The results can be used as the reference for the selection of substrate for analysis of active ingredients in traditional Chinese medicine by SERS technology at home and abroad.
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[1] YANG D, YING Y. Applications of Raman spectroscopy in agricultural products and food analysis: a review[J]. Application Specification Reviews, 2011, 46(7): 539-560. [2] SCHLÜCKER S. Surface-enhanced Raman spectroscopy: concepts and chemical applications[J]. Angewandte Chemie—International Edition, 2014, 53(19): 4756-4795. doi: 10.1002/anie.201205748 [3] LU Sh Y, WANG Sh G, LIU W J, et al. Raman spectroscopy in ovarian cancer diagnostics[J]. Spectroscopy and Spectral Analysis, 2017, 37(6):1784-1788(in Chinese). [4] LI W, FAN X G, WANG X, et al.Design of rapid detection system for urotropine in food based on SERS[J]. Spectroscopy and Spectral Analysis, 2017, 37(6):1778-1783(in Chinese). [5] DONG J L, HONG M J, ZHENG X Q, et al. Discrimination of human, dog and rabbit blood using Raman spectroscopy[J]. Spectroscopy and Spectral Analysis, 2018, 38(2):459-466(in Chinese). [6] FAN Y X, LAI K Q, RASCO BARBARA A, et al. Analyses of phosmet residues in apples with surface-enhanced Raman spectroscopy[J]. Food Control, 2014, 37(1):153-157. [7] OU Y M, PEI L, L K Q, et al. Rapid analysis of multiple sudan dyes in chili flakes using surface-enhanced Raman spectroscopy coupled with Au-Ag core-shell nanospheres[J]. Food Analytical Methods, 2017, 10(3): 565-574. doi: 10.1007/s12161-016-0618-z [8] LIU Y D, X Q H, WANG H Y, et al. Quantitative study on phosmot residues in navel oranges based on surface enhanced Raman spectra[J]. Laser Technology, 2017, 41(4): 545-548(in Chinese). [9] SHARMA Y, DHAWAN A. Plasmonic "nano-fingers on nanowires"as SERS substrates[J]. Optics Letters, 2016, 41(9): 2085-2088. doi: 10.1364/OL.41.002085 [10] HUANG Y, CHEN Y, XUE X T, et al. Unexpected large nanoparticle size of single dimer hotspot systems for broadband SERS enhancement[J]. Optics Letters, 2018, 43(10): 2332-2335. doi: 10.1364/OL.43.002332 [11] LI R P, LI Y M, HAN J H, et al. In situ SERS monitoring of plasmonic nano-dopants during photopolymerization[J]. Optics Letters, 2017, 42(9): 1712-1715. doi: 10.1364/OL.42.001712 [12] TIAN Y, ZHANG H, XU L L, et al. Self-assembled monolayers of bimetallic Au/Ag nanospheres with superior surface-enhanced Raman scattering activity for ultra-sensitive triphenylmethane dyes detection[J]. Optics Letters, 2018, 43(4): 635-638. doi: 10.1364/OL.43.000635 [13] LIN R B, HU L, WANG J Zh, et al. Raman scattering enhancement of a single ZnO nanorod decorated with Ag nanoparticles: synergies of defects and plasmons[J]. Optics Letters, 2018, 43(10): 2244-2247. doi: 10.1364/OL.43.002244 [14] YE Y, LIU Y, SUN S. Theoretical and experimental study on Raman spectra of ammonium thiocyanate solution[J]. Laser Technology, 2015, 39(2): 280-283(in Chinese). [15] ZHENG L M, LV Y W, TANG Sh X, et al. Phase growth mechanism of ultra-fine nano-diamond prepared by nanosecond laser[J]. Laser Technology, 2016, 40(1): 25-28(in Chinese). [16] DENG Y.Comparative study of three SERS active substractes based on AgNPs[D]. Dalian: Dalian University of Technology, 2015: 16-36(in Chinese). [17] LEE P C, MEISEL D. Adsorption and surface-enhanced Raman of Dyes on silver and gold sols[J]. The Journal of Physical Chemistry, 1982, 86(17): 3391-3395. doi: 10.1021/j100214a025 [18] JI Sh F, JIANG T L, XU K, et al. FTIR study of the adsorption of water on ultradispersed diamond powder surface[J]. Applied Surface Science, 1998, 133(4): 231-238. [19] LIU Y, LIU Ch Y, ZHANG Zh Y, et al. The surface enhanced Raman scattering effects of composite nanocrystals of Ag-TiO2[J]. Spectrochimica Acta, 2001, A57(1):35-39. [20] YANG H D, LIN X, LIU Y L, et al. Preparation of three-dimensional hotpot SERS Substrate with silver nanocubes and its application in detection of pesticide[J]. Spectroscopy and Spectral Analysis, 2018, 38(1): 99-103(in Chinese). [21] LI D W. Controlled synthesis of carbon nanocoils and their application in SERS[D]. Dalian: Dalian University of Technology, 2013: 87-98(in Chinese).