Fabrication of Flexible Surface-Enhanced Raman Spectroscopy Chip
柔性表面增强拉曼光谱(SERS)基底具有灵活形变的特点,适合不规则曲面的原位检测,甚至可以直接进行擦拭取样的检测。对不同反射率的衬底进行仿真分析和实验测试,可以看到衬底的反射率对拉曼信号的收集有极大的影响。在波长为532nm的光激发铝箔具有高反射率,因此选择铝箔作为衬底,采用银溶胶滴铸法制备柔性SERS芯片。实验通过控制溶剂成分,利用表面张力梯度引起向内马兰哥尼(Marangoni)流动以抑制咖啡环的产生,可以改善纳米粒子的分布均匀性。拉曼测试结果表明,SERS芯片的增强因子高达1.32×10 8,对R6G溶液的检测限低至1×10 -11 mol,同时芯片表现出良好的信号均匀性。
Objective Surface-enhanced Raman spectroscopy (SERS) can provide fingerprint information on target molecules with high detection sensitivity without being affected by water, which makes it an attractive non-destructive analysis technology. The SERS active substrate is key part of inspection applications. Therefore, a significant research effort has been devoted to the development of a stable, uniform, and repeatable SERS substrate. Unlike rigid SERS substrate, flexible SERS substrate can be flexibly deformed, which is convenient for in situ detection on irregular curved surfaces and can even be used for wipe sampling detection directly. However, the characteristics of the flexible substrate itself significantly impact the SERS performance, and the commonly used sol drop casting method to prepare SERS active substrates is significantly affected by the “coffee ring” effect. Because the effect caused uneven distribution of nanoparticles, uniformity of the SERS signal is affected. In this paper, simulation analysis and experimental research on the reflectivity of the substrate are carried out, and optimization of the substrate is performed to suppress the “coffee ring” effect. A high-throughput and array-type flexible SERS chip with excellent performance is successfully fabricated, which has application potential in biomedicine, food safety, environmental pollution, and other detection fields.
Methods To study the influence of substrate reflectivity on SERS performance, the Raman signal intensities of different substrates are compared and analyzed by simulation (COMSOL Multiphysics) and experimental tests. To eliminate the “coffee ring” effect generated from the evaporation of nanoparticle suspensions, we control the solvent composition by adding a certain proportion of ethylene glycol in Ag sol, and use inward Marangoni flow induced by the surface tension gradient, which ensure uniform deposition of nanoparticles. The array detection unit of the SERS chip is fabricated on aluminum foil through laser printing. Then, Ag sol mixed liquid is dropped into the detection area and confined by the hydrophobic toner film. The SERS chip is formed after the droplets dried in a vacuum drying oven. Rhodamine 6G (R6G) is used as a probe molecule for the SERS test, and the performance of the SERS chip is evaluated by calculating the Raman enhancement factor and performing a signal uniformity test.
Results and Discussions Simulation analysis results show that the greater the reflectivity of the substrate, the higher the intensity of the Raman signal. The Raman detection results for R6G molecules also show that the substrate with high reflectivity is helpful for Raman signal collection, which is consistent with the simulation results. Aluminum foil is chosen as the substrate because it has the strongest reflectivity under 532nm excitation light among the several materials used, and the SERS chip is manufactured using the Ag sol drop casting method. After adding ethylene glycol to the Ag sol, a tension gradient is formed on the surface of the droplet, resulting in an inward Marangoni flow, which prevents the nanoparticles from gathering on the edge of the droplet, thereby suppressing the “coffee ring” effect. The experimental results show that when 200μL of ethylene glycol is added to 1mL of Ag sol, the “coffee ring” effect is eliminated, and the Ag nanoparticles are uniformly distributed on the substrate. The Raman test results indicate that the SERS chip exhibited a high Raman enhancement factor of up to 1.32×10 8 and a detection limit of down to 10 -11 mol for R6G molecules. Furthermore, the chip showes good signal uniformity.
Conclusions Flexible SERS chips have many advantages in Raman detection applications. In this work, simulation analysis and experimental tests show that the high reflectivity of the substrate has a significant impact on improving the SERS performance of the chip. By adding a certain proportion of ethylene glycol solution to the Ag sol, the surface tension state of the solution can be changed, ensuring uniform distribution of silver nanoparticles on the chip, thereby eliminating the “coffee ring” effect generated during deposition of the nanoparticles. The flexible SERS chip shows good Raman detection performance. The array structure of the SERS chip enables it to achieve high-throughput, multiparameter detection. It has strong application potential in fields such as biomedicine, food safety, and environmental pollution.
文枰：重庆大学光电工程学院光电技术与系统教育部重点实验室, 重庆 400044中国科学院传感器技术国家重点实验室, 上海 200050四川文理学院智能制造学院, 四川 达州 635000
张志强：重庆大学光电工程学院光电技术与系统教育部重点实验室, 重庆 400044中国科学院传感器技术国家重点实验室, 上海 200050
李丹阳：重庆大学光电工程学院光电技术与系统教育部重点实验室, 重庆 400044中国科学院传感器技术国家重点实验室, 上海 200050
陈李：重庆大学光电工程学院光电技术与系统教育部重点实验室, 重庆 400044中国科学院传感器技术国家重点实验室, 上海 200050
李顺波：重庆大学光电工程学院光电技术与系统教育部重点实验室, 重庆 400044
徐溢：重庆大学光电工程学院光电技术与系统教育部重点实验室, 重庆 400044
【1】Kneipp K, Kneipp H, Itzkan I, et al. Ultrasensitive chemical analysis by Raman spectroscopy [J]. Chemical Reviews. 1999, 99(10): 2957-2976.
【2】Zrimsek A B, Chiang N, Mattei M, et al. Single-molecule chemistry with surface-and tip-enhanced Raman spectroscopy [J]. Chemical Reviews. 2017, 117(11): 7583-7613.
【3】Zhang Y, Zhao S J, Zheng J K, et al. Surface-enhanced Raman spectroscopy (SERS) combined techniques for high-performance detection and characterization [J]. TrAC Trends in Analytical Chemistry. 2017, 90: 1-13.
【4】Wang T Y, Wang Y Y, Lin X L, et al. Ultrasensitive quantitative detection of alpha-fetoprotein based on SERS spectroscopy [J]. Chinese Journal of Lasers. 2020, 47(2): 0207026.
王廷银, 王运燚, 林学亮, 等. 基于SERS光谱技术的甲胎蛋白超灵敏定量检测 [J]. 中国激光. 2020, 47(2): 0207026.
【5】Bruzas I, Lum W, Gorunmez Z, et al. Advances in surface-enhanced Raman spectroscopy (SERS) substrates for lipid and protein characterization: sensing and beyond [J]. The Analyst. 2018, 143(17): 3990-4008.
【6】Liu Y, Zhou H B, Hu Z W, et al. Label and label-free based surface-enhanced Raman scattering for pathogen bacteria detection: a review [J]. Biosensors and Bioelectronics. 2017, 94: 131-140.
【7】Xie X H, Pu H B, Sun D W. Recent advances in nanofabrication techniques for SERS substrates and their applications in food safety analysis [J]. Critical Reviews in Food Science and Nutrition. 2018, 58(16): 2800-2813.
【8】Dong Z H, Liu Y, Qin Y Y, et al. Fabrication of fiber SERS probes by laser-induced self-assembly method in a meniscus and its applications in trace detection of pesticide residues [J]. Chinese Journal of Lasers. 2018, 45(8): 0804009.
董子豪, 刘晔, 秦琰琰, 等. 激光诱导液面自组装法制备光纤SERS探针及其农药残留检测应用 [J]. 中国激光. 2018, 45(8): 0804009.
【9】Jiang Y F, Sun D W, Pu H B, et al. Surface enhanced Raman spectroscopy (SERS): a novel reliable technique for rapid detection of common harmful chemical residues [J]. Trends in Food Science & Technology. 2018, 75: 10-22.
【10】Tong Q, Wang W J, Fan Y N, et al. Recent progressive preparations and applications of silver-based SERS substrates [J]. TrAC Trends in Analytical Chemistry. 2018, 106: 246-258.
【11】Zhang Y, Wang G, Yang L, et al. Recent advances in gold nanostructures based biosensing and bioimaging [J]. Coordination Chemistry Reviews. 2018, 370: 1-21.
【12】Mosier-Boss P. Review of SERS substrates for chemical sensing [J]. Nanomaterials. 2017, 7(6): 142.
【13】Hamajima S, Mitomo H, Tani T, et al. Nanoscale uniformity in the active tuning of a plasmonic array by polymer gel volume change [J]. Nanoscale Advances. 2019, 1(5): 1731-1739.
【14】Lee T, Jung S, Kwon S, et al. Formation of interstitial hot-spots using the reduced gap-size between plasmonic microbeads pattern for surface-enhanced Raman scattering analysis [J]. Sensors. 2019, 19(5): 1046.
【15】Sivashanmugan K, Lee H, Syu C H, et al. Nanoplasmonic Au/Ag/Au nanorod arrays as SERS-active substrate for the detection of pesticides residue [J]. Journal of the Taiwan Institute of Chemical Engineers. 2017, 75: 287-291.
【16】Wen S P, Su Y, Wu R, et al. Plasmonic Au nanostar Raman probes coupling with highly ordered TiO2/Au nanotube arrays as the reliable SERS sensing platform for chronic myeloid leukemia drug evaluation [J]. Biosensors and Bioelectronics. 2018, 117: 260-266.
【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.
【18】Jiang H Z, Xu D P, Kang W G, et al. Fractal study and SERS effect of silver nanowires with high surface roughness [J]. Acta Optica Sinica. 2019, 39(7): 0716001.
江恒泽, 徐大鹏, 康维刚, 等. 高表面粗糙度银纳米线的分形研究和SERS效应 [J]. 光学学报. 2019, 39(7): 0716001.
【19】Chen X J, Chen Q N, Wu D Z, et al. Sonochemical and mechanical stirring synthesis of liquid metal nanograss structures for low-cost SERS substrates [J]. Journal of Raman Spectroscopy. 2018, 49(8): 1301-1310.
【20】Huang W R, Yu C X, Lu Y R, et al. Mass-production of flexible and transparent Te-Au nylon SERS substrate with excellent mechanical stability [J]. Nano Research. 2019, 12(6): 1483-1488.
【21】Deegan R D, Bakajin O, Dupont T F, et al. Capillary flow as the cause of ring stains from dried liquid drops [J]. Nature. 1997, 389(6653): 827-829.
【22】Hu H, Larson R G. Marangoni effect reverses coffee-ring depositions [J]. The Journal of Physical Chemistry B. 2006, 110(14): 7090-7094.
【23】Usman M, Guo X, Wu Q S, et al. Facile silicone oil-coated hydrophobic surface for surface enhanced Raman spectroscopy of antibiotics [J]. RSC Advances. 2019, 9(25): 14109-14115.
【24】Gao Y K, Yang N, You T T, et al. Superhydrophobic “wash free” 3D nanoneedle array for rapid, recyclable and sensitive SERS sensing in real environment [J]. Sensors and Actuators B: Chemical. 2018, 267: 129-135.
【25】Yang S K, Dai X M, Stogin B B, et al. Ultrasensitive surface-enhanced Raman scattering detection in common fluids [J]. PNAS. 2016, 113(2): 268-273.
【26】Wang Q Z, Liu Y N, Bai Y W, et al. Superhydrophobic SERS substrates based on silver dendrite-decorated filter paper for trace detection of nitenpyram [J]. Analytica Chimica Acta. 2019, 1049: 170-178.
【27】Ji B, Zhang L, Li M, et al. Suppression of coffee-ring effect via periodic oscillation of substrate for ultra-sensitive enrichment towards surface-enhanced Raman scattering [J]. Nanoscale. 2019, 11(43): 20534-20545.
【28】Zhao X F, Yu J, Zhang C, et al. Flexible and stretchable SERS substrate based on a pyramidal PMMA structure hybridized with graphene oxide assivated AgNPs [J]. Applied Surface Science. 2018, 455: 1171-1178.
【29】Xiong Z Y, Lin M S, Lin H T, et al. Facile synthesis of cellulose nanofiber nanocomposite as a SERS substrate for detection of thiram in juice [J]. Carbohydrate Polymers. 2018, 189: 79-86.
【30】Zhou N N, Meng G W, Zhu C H, et al. A silver-grafted sponge as an effective surface-enhanced Raman scattering substrate [J]. Sensors and Actuators B: Chemical. 2018, 258: 56-63.
【31】Xu J T, Li X T, Wang Y X, et al. Flexible and reusable cap-like thin Fe2O3 film for SERS applications [J]. Nano Research. 2019, 12(2): 381-388.
【32】Zhang W Y, Man P H, Wang M H, et al. Roles of graphene nanogap for the AgNFs electrodeposition on the woven Cu net as flexible substrate and its application in SERS [J]. Carbon. 2018, 133: 300-305.
【33】Wu H X, Luo Y, Hou C J, et al. Flexible bipyramid-AuNPs based SERS tape sensing strategy for detecting methyl parathion on vegetable and fruit surface [J]. Sensors and Actuators B-Chemical. 2019, 285: 123-128.
【34】Zeng F Y, Mou T T, Zhang C C, et al. Paper-based SERS analysis with smartphones as Raman spectral analyzers [J]. The Analyst. 2019, 144(1): 137-142.
【35】Reokrungruang P, Chatnuntawech I, Dharakul T, et al. A simple paper-based surface enhanced Raman scattering (SERS) platform and magnetic separation for cancer screening [J]. Sensors and Actuators B: Chemical. 2019, 285: 462-469.
【36】Oliveira M J. Quaresma P, de Almeida M P, et al. Office paper decorated with silver nanostars-an alternative cost effective platform for trace analyte detection by SERS [J]. Scientific Reports. 2017, 7(1): 2480.
【37】Xu Y Y, Man P H, Huo Y Y, et al. Synthesis of the 3D AgNF/AgNP arrays for the paper-based surface enhancement Raman scattering application [J]. Sensors and Actuators B: Chemical. 2018, 265: 302-309.
【38】Kim W, Lee S H, Kim J H, et al. Paper-based surface-enhanced Raman spectroscopy for diagnosing prenatal diseases in women [J]. ACS Nano. 2018, 12(7): 7100-7108.
【39】Stamplecoskie K G, Scaiano J C, Tiwari V S, et al. Optimal size of silver nanoparticles for surface-enhanced Raman spectroscopy [J]. The Journal of Physical Chemistry C. 2011, 115(5): 1403-1409.
【40】Araújo A, Caro C, Mendes M J, et al. Highly efficient nanoplasmonic SERS on cardboard packaging substrates [J]. Nanotechnology. 2014, 25(41): 415202.
【41】Kim D, Jeong S, Park B K, et al. Direct writing of silver conductive patterns: improvement of film morphology and conductance by controlling solvent compositions [J]. Applied Physics Letters. 2006, 89(26): 264101.
【42】Yang F, Chen L, Li D Y, et al. Printer-assisted array flexible surface-enhanced Raman spectroscopy chip preparation for rapid and label-free detection of bacteria [J]. Journal of Raman Spectroscopy. 2020, 51(6): 932-940.
【43】Zong C, Xu M, Xu L J, et al. Surface-enhanced Raman spectroscopy for bioanalysis: reliability and challenges [J]. Chemical Reviews. 2018, 118(10): 4946-4980.
Yang Feng,Wen Ping,Zhang Zhiqiang,Li Danyang,Chen Li,Li Shunbo,Xu Yi. Fabrication of Flexible Surface-Enhanced Raman Spectroscopy Chip[J]. Chinese Journal of Lasers, 2021, 48(1): 0113001
杨峰,文枰,张志强,李丹阳,陈李,李顺波,徐溢. 柔性表面增强拉曼光谱芯片制备[J]. 中国激光, 2021, 48(1): 0113001