基于贵金属纳米阵列与纳米颗粒拼合式SERS衬底及其性能研究

Surface-enhanced Raman scattering (SERS) has become the research hotspots of molecular detection fields due to the great application prospect in biological, food and environmental testing. The key issues for SERS-based detection in the practical application is to build the nanostructured SERS-substrates with high SERS-activity, uniform structures and stable chemical properties. According to the requirements of SERS-substrates for the practical application, we propose a kind of split type SERS-substrates built via the separated fabrication and combined SERS-measurement. First, we fabricate the ordered noble nanoarrays and nanoparticles, respectively. The noble nanoarray in the SERS substrates are coated with an ultrathin dielectric layer, and the noble nanoparticles are immersed in the organic solvent for liquid seal, restraining the oxidation and sulfuration of the noble materials. During the process of SERS measurement, the noble nanoparticles adsorb on the surface of nanounits of nanoarrays, and are separated from the nanounits of nanoarrays by the ultrathin dielectric layer, forming the nanogap (i.e SERS-hot spots) for the improvement of SERS activity. In addition, the SERS signals are uniform in the whole SERS-substrate due to the ordered structure of nanoarray. Consequently, our fabricated nanostructured SERS-substrates and the SERS-measurement method can meet the demands of SERS-based detection in the practical application. In the project, we will investigate the fabrication method of the split type SERS-substrates, and set up the relation among the structural parameters of the nanostructured SERS-substrates and the LSPR and SERS-activity, explore the enhanced mechanism of the SERS-substrates. Our results will provide the new ideal and method for the fabrication of SERS-substrates for practical application, and promote the practical application of SERS-based detection, which is very important to the ecology environment and human health.

表面增强拉曼(SERS)技术在生物、食品及环境检测领域有很大的应用前景，是分子检测领域的研究热点。而推动SERS技术实用化的关键是需要获取满足实用化要求的SERS衬底。本项目拟将超薄膜、有序纳米结构及纳米颗粒的制备技术整合起来，研发一种新型高性能拼合式SERS衬底。通过分体构筑方案，分别制备贵金属纳米阵列和纳米颗粒，并对阵列单元进行超薄膜包敷、对颗粒采用有机溶剂封存，确保其化学性质稳定；应用时，分散颗粒于含待测分子溶液中，并提取与阵列拼合，使颗粒与阵列单元间被超薄膜隔离，形成SERS热点；同时，利用阵列的有序性确保测试时信号均匀。通过分体构筑和拼合测试相结合，可获得集高活性、高化学稳定性且检测信号均匀为一体的SERS衬底。本项目通过系统研究拼合式衬底的构筑方法，获取衬底结构参数与LSPR、SERS效应间关系，探究衬底SERS增强机理；为推动SERS技术实用化提供新思路，具有重要的科学意义。

SERS技术对有机分子具有“指纹”识别能力，是分子检测领域的研究热点，在生物、食品及环境检测领域具有广泛应用前景。推动SERS技术实用化的关键是要获得满足实用化要求的SERS衬底。对于实际应用，SERS衬底需要同时满足以下三个要求：① 高的SERS活性（具有高密度活性点“hot spot”）；② 均一的结构（hot spot分布均匀，确保整个衬底SERS信号重复性）；③ SERS衬底的化学稳定性（较长的保质期）。一般来说，SERS衬底上的“hot spot”主要产生于贵金属纳米结构间隙（距离<10 nm）处，特别是当间隙被精确控制在5 nm范围内时具有大幅度增强的局域电磁场，赋予衬底高的SERS活性。鉴于此，课题组展开了在精确地调控纳米间隙条件下以实现高灵敏度、持久稳定性SERS检测的相关研究。.为此，课题组研究人员改进了薄膜/壳层隔离策略，研究了以纳米超薄膜、 有序纳米结构、 纳米颗粒制备及组装技术为基础，设计并构筑一种能新型高性能拼合式纳米结构SERS衬底。.该拼合式SERS衬底，由有序的Al2O3@Ag@Si纳米锥阵列和Ag纳米颗粒(Ag-NPs)组成，基于原子层沉积ALD技术精确控制间隙，纳米颗粒与阵列的拼合策略能够让探针分子进入中心热点区域，使热点得到充分发挥。在SERS测量时，将Ag-NPs分散在含有探针分子的液体中，然后自组装在Al2O3@Ag@Si纳米锥表面。由于超薄的Al2O3介电层将Ag-NPs与Ag@Si纳米锥分离，形成gap引入的热点。相关理论和实验研究表明，这种拼合组装有效地解决了壳隔离SERS底物的问题，提高了SERS活性，保证了SERS信号的再现性。同时，Ag-NPs的液封以及纳米锥上的介电层抑制了SERS衬底中Ag材料的氧化，延长了储存寿命和提高其化学稳定性。该研究对SERS基底在检测环境中有机污染物方面具有应用前景和新型衬底的构造也具有重要参考意义。