Photoinduced Enhanced Raman from Lithium Niobate on Insulator Template

Abstract

Photoinduced enhanced Raman spectroscopy from a lithium niobate on insulator (LNOI)-silver nanoparticle template is demonstrated both by irradiating the template with 254 nm ultraviolet (UV) light before adding an analyte and before placing the substrate in the Raman system (substrate irradiation) and by irradiating the sample in the Raman system after adding the molecule (sample irradiation). The photoinduced enhancement enables up to an ∼sevenfold increase of the surface-enhanced Raman scattering signal strength of an analyte following substrate irradiation, whereas an ∼threefold enhancement above the surface-enhanced signal is obtained for sample irradiation. The photoinduced enhancement relaxes over the course of ∼10 h for a substrate irradiation duration of 150 min before returning to initial signal levels. The increase in Raman scattering intensity following UV irradiation is attributed to photoinduced charge transfer from the LNOI template to the analyte. New Raman bands are observed following UV irradiation, the appearance of which is suggestive of a photocatalytic reaction and highlight the potential of LNOI as a photoactive surface-enhanced Raman spectroscopy substrate.

Surface Enhanced Raman Scattering Revealed by Interfacial Charge-Transfer Transitions

“…Al-Shammari et al extended this strategy to a lithium niobate film substrate decorated with photodeposited Ag nanoparticles, which showed a 7-fold increase in the signal intensity of ATP. 106 The enhancement from PIERS was demonstrated to last for a time span of~10 h, which is an order of magnitude longer than that observed with the previously reported TiO 2 -based substrate. The PICT from the substrate to 4-ABT was confirmed to be the main contribution to the observed enhancement, with a relatively slow charge recombination rate in lithium niobate being responsible for the increased PIERS duration.…”

New Mechanism for Long Photo‐Induced Enhanced Raman Spectroscopy in Au Nanoparticles Embedded in TiO2

“…Other mechanisms have been considered in very specific systems, in 2018, Al‐Shammari et al. [ 28 ] have reported on their study of PIERS on Ag NP drop casted on lithium niobate and, in 2020, Abid et al. [ 29 ] have published their results of PIERS on AuNP drop casted on a 2D material, WS 2 .…”

“…In these systems, the wavelength of the LSP resonance (LSPR) is always blue-shifted after UV irradiation. Other mechanisms have been considered in very specific systems, in 2018, Al-Shammari et al [28] have reported on their study of PIERS on Ag NP drop casted on lithium niobate and, in 2020, Abid et al [29] have published their results of PIERS on AuNP drop casted on a 2D material, WS 2 . In the first case, it seems that the Raman enhancement is favored by a photocatalytic effect.…”

“…[30]. PIERS has already been demonstrated successful on a diversity of molecules: Raman probes, [27][28][29]31] biomolecules (DNA, [32] tyrosine, [33] and glucose [27] ), explosives, [27,34] and organic pollutants. [35,36] It has also been used for the study of V O dynamics in semiconductors.…”

Photo-induced enhanced Raman spectroscopy (PIERS): sensing atomic-defects, explosives and biomolecules

“…The process was termed "Photo-induced enhanced Raman Spectroscopy", PIERS. Utilizing PIERS as an additional enhancement mechanism for trace level detection, additional studies on both traditional semiconductors 15,16 and un-conventional SERS substrates 17 have since been reported. Although within PIERS, resonant vibronic-coupling charge transfers are utilized, hence, a metal-free system would still facilitate semiconductordefect-analyte transfers with a noticeable PIERS enhancement.…”