Ústav fyziky kondenzovaných látek - Department of Condensed Matter Physics

Plasmonic enhanced Raman spectroscopy

The relatively low cross-section of Raman scattering prevents routine application of Raman spectroscopy for characterization of surface structures with thickness in the monolayer range or biomolecular samples in the range of physiological concentrations. In these cases, the scattering efficiency can be augmented by using metallic nanostructures.
The resulting Raman enhancement is coming from amplification of the probing light in the near field, when suitably coupled to the electron plasma oscillations in the metallic nanostructures. Our focus lies in mutual tuning of the probing light and the nanostructures for optimal enhancement.

case studies:

Depth scan across ATR-Raman spectra with 10 mW excitation at 532 nm of Ag chip covered with (presumably a monolayer of) brilliant cresyl blue from 20 min soaking in 1 mM solution. The step between two subsequent spectra is 0.025 mm; x20 LWD objective with NA=0.4 was used to measure the spectra with accumulation of 1 s. (2020)

Absorbance of citrate capped silver nanoprisms, as prepared and after 4-step centrifugation (FWHM 187 nm). The inset shows for comparison result of rate-zonal centrifugation; the bottom unfractionated centrifuggate is equivalent to the 4-step centrifugation. (2020)

Tunable excitation SERRS spectra of 1uM solution of rhodamine 6G in Ag NP colloid with absorption maximum at 450 nm. The wavelengths of the excitating laser are given in legend, the vertical axes share absolute units (normalised to 50 s acquisition at 100 uW). The inset shows conventional Raman spectrum of 100 uM R6G (acquisition 100 s by 30 mW at 633 nm). As the optical path for both samples was same, the SERRS enhancement can be easily calculated, close to EF=10⁶ at 1510/cm R6G peak. (2015)

Turkevich method-synthetized Au NPs over graphite substrate. Using the advanced versions of the protocol, particles become practically monodisperse. (2014)

Excited plasmon in ATR-Raman as monitored in outgoing beam past the ATR ctystal: when changing continuously the wavelength of the excitation laser (shown 490-630 nm in 20 nm steps), the plasmonic dip follows the optimal resonance by shifting in incident angle and changing width. The sharpness of the SPR dip is due to using Ag chip and focusing probes. (2020)

UV-VIS characterization of silver colloids: maturing of decahedron AgNPs and comparison of their final state (FWHM 29 nm) to normalized absorbance of washed silver nanoprisms and Lee-Meisel type Ag colloid. (2020)

Ag NP mixture over AAO substrate. The shape (conjugately with size) of the NP is controlled by presence of halides during synthesis. Absorption maxima (ranging in general from VIS to IR) for the stocks shown in the bottom are given in the inset. (2015)

older studies