Plasmonic Heating Plays a Dominant Role in the Plasmon-Induced Photocatalytic Reduction of 4-Nitrobenzenethiol

Abstract

It is believed that plasmon-excited electrons from Ag and Au nanostructures can induce photochemical reactions. However, the influence of heat generated by nanoparticle (NP) hotspots during light irradiation was not systematically studied yet. To evaluate the role of plasmonic heating, we performed a surface-enhanced Raman spectroscopy study of the photocatalytic conversion of 4-nitrobenzenthiol to 4-aminobenzenthiol by metal NPs with different compositions and shapes having localized surface plasmon resonances (LSPRs) spanning the whole visible range. Our collective results based on temperature-dependent studies and multiwavelength analyses show that contrary to the previous reports, the photocatalytic reaction is not only determined by the excitation of LSPRs or by the NP material (Ag or Au) but also drastically dependent on the plasmon-induced heating. This work has strong implications for the development and engineering of novel plasmonic and photonic applications where the role of localized temperature must be considered.

Mechanistic Studies of Plasmon Chemistry on Metal Catalysts

“…[40,41,42,47] More complicated situations have emerged from the reactions initiated from pNTP, pATP, and DMAB molecules.W here pNTP or pATPm olecules are concerned, it is reported that the LSP forms an azo bond to generate DMAB molecules; [23][24][25][26][27][28][29][30] however,other observations include reduction from pNTP to pATP, and dissociation of pNTP and the azo bond in DMAB as ac onsequence of the LSP. [24,35,56,57] Furthermore,d ifferent mechanisms were suggested even for the same chemical reaction. This confusing and chaotic situation suggests that, in some cases,m ore than two excitation mechanisms operate synergistically because the LSP serves as three excitation sources:a ne lectric field, electron-hole pairs,a nd heat.…”

“…Golubev et al concluded that local heating was crucial for plasmon-induced reduction from pNTP to pATP, which was investigated by multiwavelength and temperaturedependent SERS measurements. [57] Thel ocal heating mechanism was also applied to explain the dehydrogenation from phenyl rings in 2,13-bis(aldehyde)- [7]thiaheterohelicene molecules observed during TERS measurements. [37] Yu et al used scanning electrochemical microscopy (SECM) to investigate the effects of both the hot carriers and local heating generated by the LSP on photoelectrochemical reactions.…”

Mechanistic Studies of Plasmon Chemistry on Metal Catalysts

“…More complicated situations have emerged from the reactions initiated from p NTP, p ATP, and DMAB molecules. Where p NTP or p ATP molecules are concerned, it is reported that the LSP forms an azo bond to generate DMAB molecules; however, other observations include reduction from p NTP to p ATP, and dissociation of p NTP and the azo bond in DMAB as a consequence of the LSP . Furthermore, different mechanisms were suggested even for the same chemical reaction.…”

“…Golubev et al. concluded that local heating was crucial for plasmon‐induced reduction from p NTP to p ATP, which was investigated by multiwavelength and temperature‐dependent SERS measurements . The local heating mechanism was also applied to explain the dehydrogenation from phenyl rings in 2,13‐bis(aldehyde)‐[7]thiaheterohelicene molecules observed during TERS measurements .…”

Surface Plasmon Enhanced Chemical Reactions on Metal Nanostructures

“…Based on the unique features, SERS has been widely used in medical diagnosis, single molecule detection, pesticide analysis, safety inspections, and identification [7]. Notably, plasmonic metal nanomaterials (such as Ag, Au, and Cu), rough metal films, and gaps between metal surfaces and metal nanomaterials are the widely used SERS platforms for promoting photochemical reactions [8]. The molecules comprising of mostly aromatic or unsaturated bonds are generally targeted for SERS measurements.…”