Peak plasmon resonant scattering wavelength

Figure 4. Effect of silver particle s shape on the peak plasmon resonance scattering wavelength. Reproduced from [14] with permission from the publisher.

Figure 3. Calculated extinction (black), absoiption (dark grey), and scattering (Ggbt grey) cross section as a Auction of wavelength for a 20,40,80, and 120 nm diameter gold particle in water. As the particle diameter is increased, the plasmon resonance scattering peak shifts to loiiger wavelengths and beconre broader.

In contrast, metals often show negative values of s. In that case both the absorption and the scattering show resonances when s + 2sm = 0, which corresponds to the dipolar plasmon oscillation mode, and a peak appears in the absorption spectrum this is observed especially clearly with alkali and noble metals (Fig. 5.3-14). For most metals, the plasmon peak shifts towards longer wavelengths and becomes sharper for matrices with a larger refractive index. This is clearly observed for the alkali metals in Fig. 5.3-14 for a computation of... 

According to Van Duyne et al. [43,44], in order to obtain SER spectra with enhancement factors as large as possible, the excitation and scattering wavelengths should, if possible, sit at the two sides of a surface plasmon resonance extinction peak [43,44]. In addition, the excitation wavelength can be selected corresponding to the molecular absorption, and... 

The measured Raman spectra of adenine nanocrystals with and without the tip are shown in Fig. 8.6b. Strong enhancement of the Raman peaks was observed when the tip was in contact with the sample. The inset of Fig. 8.6b shows the absorption spectrum of the adenine nanocrystals. The Raman excitation wavelength (266 nm) used in the experiment was closely matched to the maximum absorption peak of adenine nanocrystals. The observed spectra of the adenine nanocrystals were consistent with the reported resonance Raman spectrum of the deoxyribonucleotides of adenine (dAMP) for 266-nm excitation [72-74]. This experiment is the first demonstration of plasmonically enhanced DUV resonance Raman scattering from biologically relevant molecules. The quartz peaks observed around 500 cm remained unchanged with and without the tip, indicating the localized character of the tip-enhancement effect. The estimated enhancement factor was 1.3 x 10. ... 

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