The adsorption behavior of two hydroxyl-terminated Schiff bases on the silver surface and the correlated study of SERS effect

Fabrication of stable antibody-modified field effect transistors using electrical activation of Schiff base cross-linkages for tumor marker detection

In this paper, we present a method of fabricating a rigid antibody-immobilized surface using electric activation of a glutaraldehyde (GA)-modified aminopropylsilyl surface for stable antibody-modified field effect transistors (FETs). Electric activation of the GA-modified gate surface of the FET reduces Schiff bases, which are easily hydrolyzed and collapsed, formed between GA and 3-aminopropyltriethoxysilane, resulting in preventing the immobilized antibodies from desorbing from the surface. The lack of Raman peaks that could be assigned to a Schiff base after the electrical activation of the GA-modified surface indicated that the electric activation had reduced the Schiff base. The use of the antibody-modified FETs has three advantages for the detection of antigens: increased sensitivity, distinct recognition ability, and improved reproducibility. A tumor marker, alpha-fetoprotein (AFP), was quantitatively detected up to a concentration of 10 ng/mL using the antibody-modified FET. The detection ability of the FET accomplished a cutoff value of hepatic cancer. The quantitative detection of AFP in a solution with contaminating proteins was also demonstrated. This electric activation method is applicable to other antibody-modified FETs.

The effect of size and size distribution on the oxidation kinetics and plasmonics of nanoscale Ag particles

We employed a simple and effective electroless (EL) plating approach to produce silver nanoparticles (NPs) on bare silicon, on dielectric ZnO nanowires (NWs) and on Si NWs, respectively. The surface stability of the homogeneous Ag NPs formed on the ZnO NW surfaces was investigated by surface enhanced Raman spectroscopy (SERS), which show that the attachment of thiol to the Ag surface can slow down the oxidation process, and the SERS signal remains strong for more than ten days. To further examine the Ag NP oxidation process in air, the oxygen content in the silicon nanowire core/Ag sheath composites was monitored by the energy dispersive x-ray (EDX) method. The amount of oxygen in the system increases with time, indicating the silver NPs were continuously oxidized, and it is not clear if saturation is reached in this time period. To investigate the influence of the Ag NPs size distribution on the oxidation process, the oxygen amount in the NPs formed by EL deposition and e-beam (EB) evaporation on a bare silicon surface was compared. Results indicate a faster oxidation process in the EL formed Ag NPs than those produced by EB evaporation. We attribute this observation to the small diameter of the EL produced silver particles, which results in a higher surface energy.