Recently, surface-enhanced Raman scattering (SERS)-based immunoassays (SIA) have drawn much attention as diagnostic tools with large multiplex capacity and high sensitivity. However, several challengessuch as a low reproducibility, a time-consuming read-out process, and limited dynamic rangeremain. In this study, we report a reliable and sensitive SIA platform for prostate specific antigen (PSA) detection. Reliability and sensitivity were achieved by two approaches: (1) well-established SERS probes, so-called SERS dots that have high sensitivity (single particle detection) and little particle-to-particle variation in SERS intensity; and (2) a whole area-scanning readout method for rapid and reliable chip analysis rather than point scanning. As a feasibility test, PSA could be detected with high sensitivity (ca. 0.11 pg/mL, 3.4 fM LOD), with a wide dynamic range (0.001−1000 ng/mL). Thus, the developed platform will facilitate development of reliable immunoassays with high sensitivity and a wide dynamic range.

The Ce 3+ /Ce 4+ redox potential changes with the electrolyte, which could be due to unequal anion complexation free energies between Ce 3+ and Ce 4+ or a change in the solvent electrostatic screening. Ce complexation with anions and solvent screening also affect the solubility of Ce and charge transfer kinetics for electrochemical reactions involving waste remediation and energy storage. We report the structures and free energies of cerium complexes in seven acidic electrolytes based on Extended X-ray Absorption Fine Structure, UV−vis, and Density Functional Theory calculations. Ce 3+ coordinates with nine water molecules as [Ce(H 2 O) 9 ] 3+ in all studied electrolytes. However, Ce 4+ complexes with anions in all electrolytes except HClO 4 . Thus, our results suggest that Ce 4+ −anion complexation leads to the large shifts in standard redox potential. Long range screening effects are smaller than the anion complexation energies but could be responsible for changes in the Ce solubility with acid.

The fabrication of hollow metal nanostructures on a silica core template has been widely studied by taking advantage of the chemical stabilities of silica cores. When the size of the silica core reduces, however, this benefit is no longer effective because there are the synthetic difficulties which often cause dispersion instability, and therefore finally the aggregations of nanoparticles (NPs) are often caused during introduction of metallic nanostructures. This study reports the successful fabrication of silver nanoshells (AgNSs; 119, 152, 165, 186, and 207 nm) on amorphous silica nanoparticles (Si NPs) of different core sizes (59, 82, 103, 124, and 148 nm) by overcoming the increased instabilities during fabrication with reduced core sizes. Improvements related to fabrication were made by changing the reducing agents, controlling the amount of the dispersing agent and the concentration of Si NPs. All the AgNSs showed broad extinction from the visible to the near-infrared (NIR) region regardless of particle sizes, and their sizedependent surface properties were analyzed by introducing a concept of roughness factor, with AgNS of 152 nm exhibiting the highest degree of roughness. High SERS enhancements of AgNSs of all sizes were observed at three laser excitation wavelengths (532, 660, and 785 nm), and these enhancements correlated positively with the surface roughness. Therefore, our results provide a clear understanding of size-dependent SERS activity for AgNS, facilitating proper selection of AgNS with an appropriate size depending on the purpose of the investigation.