海绵状Ag方形纳米颗粒阵列的高效绿色制备及其近红外SERS应用

The large specific surface area and high porosity of the porous Ag nanoparticles enable increasing the number of target molecules in local enhancement electric range and produce abundant inherent hotspots. The clean surface makes these hotspots readily accessible by target molecules, but the present preparation methods suffer from multistep and complicated processes, strict reaction conditions and surfactants. Based on our previous research results, an interesting, remarkably simple and environment-friendly route to fabricate sponge-like Ag nanocubes by reducing Ag3PO4 nanocubes by using NaBH4 as a reducing agent will be developed. The three-dimensional sponge-like structure was full of tiny intersecting Ag nanorods, which make it show surface plasmon resonance (SPR) over the entire visible region as well as in the near infrared (NIR) region of the spectrum. Additionally, the nanogaps among these Ag nanorods, and the sharp corners as well as the edges of these nanocubes can produce high-density SERS “hotspots”. Therefore, a new NIR SERS active substrate based on monolayer porous Ag nanocubes arrays was constituted by an air-water interfacial self-assembly method. The influence of amount of NaBH4 and reaction time on morphology of the sponge-like Ag nanocubes will be studied systematically. Moreover, the self-assemble process of the sponge-like Ag nanocubes and the electromagnetic field coupling effect in the SERS active substrate will be explored. The motivation of this project is to develop a high-yield and green method to prepare the sponge-like nanoparticles for the SERS active substrate with perfect performance. The research achievement will provide the important theoretical foundation and experimental data for applications of porous sponge-like noble metal nanostructures in chemical and biological sensing area.

本项目针对现有多孔Ag纳米颗粒制备工艺复杂、反应条件苛刻及存在表面活性剂等不足，提出硼氢化钠（NaBH4）还原磷酸银（Ag3PO4）方形纳米颗粒，制备海绵状Ag方形纳米颗粒的新方法。此法简单快捷、高效环保，整个过程既无需使用任何有机溶剂，也无需进行高温处理。该海绵状方形纳米颗粒由Ag纳米棒交叉构成，在可见光和近红外区域均显示出SPR现象。此外，这些纳米棒之间以及方形纳米颗粒边、角处存在大量纳米间隙，从而产生三维分布的高密度SERS“热点”。进一步提出以该海绵状Ag方形纳米颗粒为结构单元，使用气-液界面自组装方法构筑海绵状Ag方形纳米颗粒有序阵列近红外SERS活性基底的策略。系统研究NaBH4的加入量、反应时间对纳米颗粒形貌的影响；揭示海绵状Ag方形纳米颗粒的自组装机制；深入探索该类基底的SERS增强机理。旨在发展一种海绵状金属方形纳米颗粒简单，绿色的制备方法，实现高性能SERS基底的构筑。

本项目针对现有海绵状多孔Ag纳米颗粒制备工艺复杂，反应条件苛刻及存在表表面活性剂的缺点，探究了硼氢化钠（NaBH4）还原磷酸银（ Ag3PO4）方形纳米颗粒，制备海绵状Ag纳米颗粒的方法。此法简单、快速、环保、经济，整个过程无需使用表面活性剂、有机溶剂和高温处理。. 采用简单的离子交换法，通过调节反应的水热温度合成了立方体与内凹结构八角体形Ag3PO4颗粒。对这三种形貌Ag3PO4颗粒进行物理和光学性质研究。研究表明Ag3PO4球形、立方体和内凹八角体的相应禁带宽度分别为2.56、2.50和2.46 eV。在可见光照射下，内凹结构八角体形Ag3PO4颗粒在60 min内对亚甲基蓝的降解率可达99%，这归因于内凹结构八角体形Ag3PO4颗粒所暴露的高指数晶面，所暴露晶面不仅可以明显提高光吸收响应和光利用率，可以产生更多的光生电子空穴对来参与反应； . 以内凹结构八角体形Ag3PO4颗粒为模板，NaBH4为还原剂，经过一次还原、二次还原分别得到单分散性良好，形貌均一且粒径分布均匀的八角海绵状多孔Ag、八角中空笼状多孔Ag颗粒。两种多孔Ag纳米颗粒的尺寸形貌可控，且在制备过程中无需添加保护剂。两种多孔Ag材料具有粗糙表面、尖锐枝角，并且八角中空笼状多孔Ag材料具有空心的内部，均可以被用来组装为SERS基底，八角中空笼状多孔Ag材料表现出更优异的SERS活性。八角中空笼状多孔Ag材料对4-ATP分子和福美双分子的检测下限分别为10-11 M和10-8 M，八角海绵状多孔Ag材料对4-ATP分子和福美双分子的检测下限分别为10-10 M和10-8 M。优异的SERS活性来自于纳米孔的SERS“热点”和尖锐的边角。. 该制备方法具有普适性，可以延伸至其他形貌的多孔合金纳米颗粒。所制备的多孔Ag材料具有特殊的形貌和优异的光学性能，在表面等离激元、SERS检测、药物传递、光热治疗和催化领域有着广泛应用。

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