Aggregation of Silver Particles Trapped at an Air−Water Interface for Preparing New SERS Active Substrates

Abstract

In this paper, we propose a novel technique for the fabrication of active substrates of surface-enhanced Raman scattering (SERS). It was found that the silver particles themselves and the analyte-covered silver particles can be trapped at the air-water interface. In the presence of electrolyte, for example, KCl that is generally used to activate silver colloids for additional SERS enhancement, the trapped silver particles and clusters can attract each other spontaneously to form two-dimensional silver particle films. By this technique, the prerequisite aggregation of silver colloids for the SERS process is provided. At the same time, because the aggregation occurs only at the interface, problems of irreversible aggregation and instability of silver colloids can largely be overcome. The SERS enhancement ability of these silver particle films is larger by 1-2 orders than that of usual active substrates such as silver colloids and silver mirror. Their strong enhancement ability may arise from the unique two-dimensional structure itself.

Enhanced Raman Scattering as a Probe for 4-Mercaptopyridine Surface-modified Copper Oxide Nanocrystals

“…38 A single peak appears at 1612 cm -1 corresponding to N-protonation, whereas the corresponding band appears at 1580 cm -1 due to N-deprotonation, and a pair of peaks are found at 1612 and 1580 cm -1 at weakly acidic conditions. 39 This result indicates that the N atom is deprotonated in the Raman spectrum of 4-Mpy adsorbed on CuO nanocrystals. This deprotonation marker appears in the spectrum coincident with the lack of the band at 1250 cm -1 characteristic of the in-plane N-H deformation.…”

Nanostructures and nanostructured substrates for surface—enhanced Raman scattering (SERS)

“…Similar procedures use photo-reduced AgCl to form silver nanoparticles on quartz surfaces. 45 This method involves the immersion of cleaned quartz slides in poly(diallydimethylammonium chloride) (PDDA) followed by rinsing in distilled water and immersion in a solution of freshly prepared silver nanoparticles (used as 'seeds' for the process), followed by further rinsing. These structures are then immersed in a solution of silver nitrate and sodium citrate and irradiated with a sodium lamp for an extended period.…”

Surface-enhanced Raman scattering of silver-gold bimetallic nanostructures with hollow interiors

“…Additionally, the laser was focused ͑approximately 100 m spot size͒ with a fixed focusing distance for all the samples, which was estimated to be 180 m. Figure 1 shows field emission scanning electron microscopy ͑FE-SEM͒ image of the hollow nanostructures on ITO, in which the hollow interiors of the nanostructures can be clearly observed because the center position was darker than the edge, and the surface coverage of the hollow nanostructures can be obtained to be 3.8 particles/ m 2 from the high Meanwhile some aggregates ͑occupying ϳ15%͒ can also be observed, which may be formed at the air-water interface. 30,31 SERS spectra of p-ATP on the silver-gold bimetallic hollow nanostructure with a mean diameter of 100 nm…”