Rapid and ultrasensitive (bio)chemical detection with dendritic metallic nanoparticle structures

对环境或生物样品中化合物的快速、定量和超灵敏检测的分析技术的需求在全球范围内不断增长。拉曼光谱法具有固有的生物化学特异性、样品制备简单和便携性，是原位样品检测的理想方法。拉曼光谱学的一种特定模式，称为“表面增强拉曼散射”（Sers），已经作为一种强大的分析技术出现，用于护理点诊断、爆炸物检测以及食品和水中的有害化学物质。Sers能够检测与金属纳米结构（1至100 nm）接触的分子，称为“热点”，并且可以将目标分子的拉曼信号增强高达14个数量级。** 阻碍Sers成为流行分析方法的一个主要障碍是缺乏可重复且具有成本效益的Sers基底，可以在其上进行灵敏的化学分析。如今，最有效的Sers基底的制造需要洁净室设施，以及劳动密集型和昂贵的纳米纤维技术。** 我们最近展示了一种简单而新颖的方法，可以克服这些瓶颈，从而允许无洁净室，原位和高效地生产超灵敏的纳米结构Sers基底。我们发现，在适当的实验条件下，胶体金属银（Ag）纳米粒子可以诱导组装成分支（“树枝状”）和高SERS活性的结构内的电场。使用我们的方法，可以在任何平坦表面上在几分钟内形成坚固，可重复使用和超灵敏的纳米颗粒树突Sers基底，在其上可以形成一对微电极。** 拟议的研究计划旨在从根本上了解电场引导的纳米颗粒树枝状组装现象以及所形成的树枝状晶体观察到的高Sers活性的原因。此外，通过利用这种生产SERS活性基底的创新方法，我们将开发一种用于实际应用的灵敏的（生物）化学检测平台。该研究计划将追求三个不同的目标：（1）提供对电场中纳米颗粒组装成SERS活性树突的机制的基本理解;（2）进一步增强这些结构的活性并使其对目标分析物具有选择性;（3）定量测试这些新的Sers基底在实际应用中的性能，例如在水下或地下水环境中检测爆炸物。该计划将培养3名博士，3名硕士和4名本科生，并为他们在医疗诊断，（生物）传感器，分析化学和胶体（食品，油漆，油墨，药品）等领域的职业生涯做好准备。**

The need for analytical technologies that provide rapid, quantitative, and ultrasensitive detection of chemical compounds in environmental or biological samples is globally on the rise. Raman spectroscopy, with its inherent biochemical specificity, simplicity in sample preparation and portability potential is an ideal method for in situ sample testing. One particular mode of Raman spectroscopy, termed “Surface-enhanced Raman scattering” (SERS), has emerged as a powerful analytical technique for applications in point-of-care diagnostics, detection of explosives, and harmful chemicals in food and water. SERS enables detection of molecules in contact with metallic nanostructures (1 to 100 nm), known as "hotspots", and can enhance the Raman signal of a target molecule up to 14 orders of magnitude. ******A major obstacle that prevents SERS from becoming a popular analytical method is the lack of reproducible and cost-effective SERS substrates, on which sensitive chemical analysis can be performed. The fabrication of the most effective SERS substrates nowadays requires clean room facilities, as well as labor-intensive and expensive nanofabrication techniques. ******We have very recently demonstrated a facile and novel method that overcomes these bottlenecks, thus allowing clean room-free, in situ and efficient production of ultrasensitive, nanostructured SERS substrates. We showed that, under proper experimental conditions, colloidal metallic silver (Ag) nanoparticles can be induced to assemble into branched (“dendritic”) and highly SERS-active structures inside an electric field. With our method, robust, reusable and ultrasensitive SERS substrates of nanoparticle dendrites can form in a few minutes on any flat surface, on which a pair of microelectrodes can be formed. ******The proposed research program aims at gaining a fundamental understanding of the phenomenon of electric field-guided dendritic assembly of nanoparticles and the reason for the observed high SERS activity of the formed dendrites. Additionally, by taking advantage of this innovative method for producing SERS-active substrates, we will develop a sensitive, (bio)chemical detection platform for real-world applications. This research program will pursue three distinct objectives: (1) To provide a fundamental understanding of the mechanism of nanoparticle assembly into SERS-active dendrites inside an electric field; (2) To further enhance the activity of these structures and render them selective to target analytes; (3) To quantitatively test the performance of these new SERS substrates in real-world applications, such as detection of explosives in underwater or ground water environments. The program will train 3 PhD, 3 Masters and 4 undergraduates and prepare them for careers in fields such as, medical diagnostics, (bio)sensors, analytical chemistry and Colloids (foods, paints, inks, pharmaceuticals). **