We report on a system of surface-enhanced Raman scattering (SERS) using solution-phase Ag decorated CuO nanoparticles. The Ag/CuO nanocomposite exhibits up to a 10 5 Raman signal enhancement as determined using the target molecule 4-aminothiophenol (4-ATP) at concentrations down to 10 μM. The surface plasmon absorption of Ag shifted slightly toward higher binding energy, which is attributed to electron transfer (charge transfer) from Ag to CuO. Further, metallic particles deposited on semiconductor materials formed a local electromagnetic field which altered the interfacial charge distribution. Using solution-phase SERS detection, the dynamic hot spot density was increased significantly, allowing for highly efficient analyte adsorption onto the Ag/CuO nanocomposite with increased electromagnetic field. The observed SERS signal enhancement in this solution-phase Ag/CuO nanocomposite system is attributed to a combination of chemical charge-transfer effect and electromagnetic enhancement occurring simultaneously at the metal−semiconductor interface. Because SERS detection is performed in the solution phase, this method provides a system for in-situ detection in aqueous environment and is thus well suited for monitoring analyte concentrations.

Structure transition cascade: Insulin fibrils undergo a secondary structural transition-from the α-rich to the β-rich form-upon progressively increasing the incubation time from 0.5 to ten hours. Atomic force microscopy measurements show that the fibril surface chemistry changes from hydrophilic to hydrophobic and the aggregation rate increases fivefold.