Abstract
Surface enhanced hyper Raman scattering (SEHRS) can provide many advantages to probing of biological samples due to unique surface sensitivity and vibrational information complementary to surface-enhanced Raman scattering (SERS). To explore the conditions for an optimum electromagnetic enhancement of SEHRS by dimers of biocompatible gold nanospheres and gold nanorods, finite-difference time-domain (FDTD) simulations were carried out for a broad range of excitation wavelengths from the visible through the short-wave infrared (SWIR). The results confirm an important contribution by the enhancement of the intensity of the laser field, due to the two-photon, non-linear excitation of the effect. For excitation laser wavelengths above 1,000 nm, the hyper Raman scattering (HRS) field determines the enhancement in SEHRS significantly, despite its linear contribution, due to resonances of the HRS light with plasmon modes of the gold nanodimers. The high robustness of the SEHRS enhancement across the SWIR wavelength range can compensate for variations in the optical properties of gold nanostructures in real biological environments.
Highlights
Hyper Raman scattering (HRS), a two-photon excited spontaneous Raman process, analogous to its one-photon counterpart Raman scattering, can be enhanced in the vicinity of a metal nanostructure, as surface-enhanced hyper Raman scattering (SEHRS) (Baranov and Bobovich, 1982; Madzharova et al, 2017)
In SEHRS they are combined with the high enhancement, the nanometer-scaled confinement, and with the unique ability of HRS to probe molecular vibrations that do not appear in Raman spectra, or even of silent modes observed neither by Raman nor IR spectroscopy (Kneipp et al, 2006b), due to different selection rules of the process that relies on a change in the hyperpolarizability of a molecule (Ziegler, 1990)
The selection of dimers of gold nanospheres and gold nanorods with a fixed size and inter-particle gap is based on a previous systematic experimental study, where we explored SEHRS enhancement by gold nanostructures as a function of nanoparticle size using an excitation wavelength of 1,064 nm, as well as finite-difference time-domain (FDTD) simulations of local field enhancements for this specific excitation condition (Madzharova et al, 2018)
Summary
Hyper Raman scattering (HRS), a two-photon excited spontaneous Raman process, analogous to its one-photon counterpart Raman scattering, can be enhanced in the vicinity of a metal nanostructure, as surface-enhanced hyper Raman scattering (SEHRS) (Baranov and Bobovich, 1982; Madzharova et al, 2017). In SEHRS they are combined with the high enhancement, the nanometer-scaled confinement, and with the unique ability of HRS to probe molecular vibrations that do not appear in Raman spectra, or even of silent modes observed neither by Raman nor IR spectroscopy (Kneipp et al, 2006b), due to different selection rules of the process that relies on a change in the hyperpolarizability of a molecule (Ziegler, 1990) This results in extraordinary possibilities to study e.g., the interaction of an organic or biological molecule with a surface (Golab et al, 1988; Hulteen et al, 2006).
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
