SERS intensity

The enthalpy of the adsorption of chlorobenzene was determined from the temperature-dependence of the SERS intensities [4.301]. 

It is clear from these H20 results that the decreases in SERS intensities as UPD layers grow on electrodes cannot be solely attributed to decreases in adsorbate coverage. This report represents the first concrete evidence for this fact in the electrochemical SERS environment. 

Figure 1. Plots of the relative surface concentrations (solid curves) and relative peak intensities (points, dashed curve) of the 500 cm-- - [Ru(III)-NHj stretch] and 460 cm l [Ru(II)-NH3 stretchJ as a function of electrode potential for Ru(NH3)g +/2+ electrostatically adsorbed at chloride-coated silver. Ru(III) and Ru(II) surface concentrations determined by integrating cyclic voltammogram obtained for conditions [50 ttM Ru(NH3)g3+ in 0.1 M KC1, 50 V sec l sweep rate] where faradaic response dominated by adsorbed redox couple. Both surface concentration and SERS intensities for Ru(III) and Ru(II) normalized to values at -100 and -500 mV vs SCE. SER spectra obtained using 647.1 irradiation.

For the outer-sphere Co(NH3)63+ reduction, the SERS and current-potential data are closely compatible in that the SERS intensities drop sharply at potentials towards the top of the voltammetric wave where the overall interfacial reactant concentration must decrease to zero. Some discrepancies between the SERS and electrochemical data were seen for the inner-sphere Cr(NH3)sBr2 and Cr(NH3)sNCS2+ reductions, in that the SERS intensities decrease sharply to zero at potentials closer to the foot of the voltammetric wave. This indicates that the inner-sphere reactant bound to SERS-active sites is reduced at significantly lower overpotentials than is the preponderant adsorbate. (15)This suggests that SERS-active surface sites might display unusual electrocatalytic activity in some cases. 

Table 10.1. Anti-Stokes to Stokes SERS Intensity Ratios at 1174 cm 1 for Crystal Violet (CV) Attached to Silver Clusters at Various Locations ...

The preparation of rough silver films by vapor deposition results in reproducible and stable surfaces for SERS. For example, deposition of 20-nm Ag films onto Teflon, polystyrene, or latex spheres [29,30] has been performed. These substrates produced strong SERS intensities for various organic adsorbates and good reproducibility between multiple rims. However, vapor deposition can be slow and needs access to a vacuum system. There are also some variables that need to be controlled, such as the film thickness, deposition temperature, and use of annealing procedures. Moreover, unless the experiment is performed under vacuum, the film is exposed to the atmosphere after deposition. Even a brief exposure to the atmosphere results in contamination of the surface and the formation of an inactive oxide layer. 

The adsorbates were applied through incubation of the cleaned SERS substrates in a 10 nM solution of Rhodamine 6G in water. SERS intensities... 

Stretching vibrations and indicated that the R6G were adsorbed on the surface of Ag-MWCNTs-Nafion. The characteristic Raman peaks in Fig. 6.3 were in agreement with other works [47, 72-74]. The SERS intensity of R6G obtained at the surface of Ag-MWCNTs-Nafion is higher than those at the surfaces of Ag and Ag-CB-Nafion. The results show that the three-dimensional nanostructure of... 

Muniz-Miranda M, Neto N, Sbrana G (2003) SERS intensities of benzodiazines adsorbed on silver nanoparticles. J Mol Struct 651-653 85-90... 

Figure 8.15 shows a sequence of subsequent SER spectra 10-69 from the point B in zone 1 having lower luminosity compared to point A. As expected, the lower luminosity also correlates to smaller SERS intensity, as seen from the strongest peaks at 1,510 and 1,270 cm Again time dependence of the peak intensities is observed. The strongest enhancement does not concern the aromatic stretch vibration but is found for the Raman peak near 1,300 cm (1,270 cm ), thus supporting that the enhancement is dependent on the adsorption position and the distance to the metal. 

At this point, it is important to clarify what is meant by the enhancement factor before discussing hot spots further. Typically, the enhancement factor is calculated as the ratio of the detected Raman signal under SERS conditions compared to the signal obtained under normal conditions, for equal numbers of active molecules and surface area exposed to the laser beam. This value is proportional to the intensity of the local electromagnetic field ( ) to the fourth power, i.e., jEj which results from the enhancement of both the incident and emitted photons [15]. Throughout the rest of the chapter, the enhancement factor that is quoted refers to this the enhancement of SERS intensity, rather than that associated with the local electromagnetic field unless otherwise stated. 

Fig. 10.5 Experimental (symbols) and calculated (dashed lines) SERS intensity as a function of segment length for smooth and rough rods produced using on-wire lithography. Theoretical values were calculated using the discrete dipole approximation and scaled to maximum experimental value (Figure reproduced from Ref. [66])...

Fig. 11.10 A representative imaging scheme using SERS multiplexing, (a) A general concept scheme. Distribution of several targets can be imaged from a single scan by Raman intensity mapping of specific SERS band of each SERS tag, and (b) an example by Woo et al. [71]. The three different SERS intensity maps correspond to distributions of CD34, Sca-1, and SP C proteins on tissue sample. They were obtained by single scan at the pre-selected area...

Xia and coworkers have demonstrated that the polarization of light plays an important role for nanoparticles with anisotropic shapes, especially with tmncated comers [77]. Optical dark-field mode imaging was employed to identify individual silver nanocubes deposited on silicon substrate as shown in Fig. 15.10a. Raman spectra were collected from the nanocubes, which were oriented in different directions with respect to the laser polarization. Subsequent SEM imaging of the same cubes enabled the authors to directly correlate the orientation of the nanocubes with respect to the light polarization and the SERS enhancement factor. They observed dramatic variation in SERS intensity when the nanocubes were oriented at different angles relative to the polarization of excitation laser as shown in Fig. 15.10b. SERS spectra of 1,4-benzenedithiol adsorbed on Ag nanocubes oriented in different directions showed different intensities with respect to the light polarization direction. The individual nanocubes with sharp comers were the most... 

The dependence of SERS intensity of CuTMPyP4 on the mass thickness of the silver evaporated on the surface of AAO has been studied to establish the optimum thickness of Ag films. The results obtained will be useful for fabrication of efficient AAO-based SERS-active substrates. 

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