Practical control of SERRS enhancement

Abstract

The demonstration that quantitative and sensitive analysis can be carried out using surface enhanced resonance Raman scattering (SERRS) prompted a discussion and investigation of the main variables which are within the control of the analyst using colloidal silver as the substrate. Previous papers have dealt with the crucial need to obtain good chemisorption of the analyte to the surface and have reported the use of specially designed dyes for SERRS. One of the most variable processes is the aggregation of the colloid. Here, we investigate the addition of controlled amounts of an organic aggregating agent, poly-L-lysine, at concentrations which reduce the zeta potential in a controlled manner, thus aiding aggregation control. The relationship between the excitation frequency, the surface plasmon resonance frequency of the silver colloid and the frequency of the maximum absorbance of the molecular chromophore is studied using low concentrations of dye and no aggregating agent. Under these conditions, little to no aggregation is expected. The magnitude of the enhancement is strongly dependent on the frequency of the molecular chromophore as well as the plasmon resonance frequency. However, when sodium chloride is used to aggregate the colloid, a larger enhancement is obtained and the strong dependence on the molecular chromophore largely disappears. A much broader enhancement profile is obtained which appears to be related more to the specific enhancement processes caused by aggregation than the frequency of the chromophore. However, the total enhancement for SERRS is higher than for SERS thus indicating that the chromophore is still important to the process.

Mixed metal nanoparticle assembly and the effect on surface-enhanced Raman scattering

“…[3][4][5] An alternative method to provide greater control over the aggregation and assembly state of the nanoparticles is to use a DNA templated approach. This has previously been used to assemble nanoparticles in a number of different studies [6][7][8][9] but only recently to investigate the enhancement of the SERS effect.…”

Manganese oxide nanoparticle-assisted laser desorption/ionization mass spectrometry for medical applications

“…The nanoparticles showed positive charge in pH < 10 indicating that NH 2 groups transformed into NH + 3 group on the nanoparticle surface. The zeta potential was more than +30 mV that was considered as the threshold value for electrostatic stabilization [19]. Magnetization results ( figure 3(d)) indicated paramagnetic behavior at 300 K and antiferromagnetic behavior with sigmoid curve at 5 K [20,21].…”

Synthesis and Characterization of Functionalized Magnetic Nanoparticles for the Detection of Pesticide

“…This indicated that NH 2 groups on nanoparticle's surface transformed into NH 3 + group. The zeta potential was more than +30 mV that was considered as the threshold value for electrostatic stabilization [32].…”