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

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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). **