Surface Plasmon-Induced Hot Electrons as the Racemate to Regulate Ionization

Abstract

Plasmon-assisted reactions have different reaction mechanisms than conventional chemical reactions occurring in solutions, and the hot electrons produced by plasmon decay play an irreplaceable role in plasmon-assisted coupling reactions. Here, we use p-mercaptobenzoic acid (pMBA) to illustrate this point from different aspects. In a typical chemical reaction, a base is added to deprotonate the carboxylic acid group in pMBA. In this system, however, there is no alkali or external charge to remove the hydrogen, but it is obvious that this system is a dynamic process. Here, although a Lewis base (Ag NPs) was used as the base, the generated hot electrons were trapped by hydrogen ions in an acidic environment, which reduced the efficiency of the ionization reaction. We used SERS to study the ionization of pMBA and to propose a method to regulate its ionization by adjusting its substituents. Furthermore, in contrast to previous studies, the direction of electron flow is clearly defined in this reaction system.

Molecular Cocatalyst-Induced Enhancement of the Plasmon-Mediated Coupling of p-Nitrothiophenols at the Silver Nanoparticle–Graphene Oxide Interface

“…Surface adsorption of certain molecules may be another effective strategy to accelerate the plasmon-mediated reactions. Recently, thiophenol and phenyl molecules have been chemically adsorbed on the surface of plasmonic metals for highly efficient chemical reactions. − However, the molecules need to be strongly adsorbed on the surface of the plasmonic metal and may block the catalytically active sites, limiting the potential of surface molecular engineering in accelerating chemical reactions. To further improve the adsorption-induced enhancement of reactions, the molecules may also be adsorbed asymmetrically on the heterostructures of the plasmonic metal with other materials.…”

Novel Clarification of Surface Plasmon Coupling Reactions of Aromatic Alkynamine and Nitro Compounds

“… 27 − 30 The p -mercaptobenzoic acid (pMBA) molecule is selected as the probe molecule because of its prominent characteristic peaks of 1075 and 1590 cm –1 in SERS. 31 , 32 However, these model molecules are all used in the traditional sulfhydryl bonding mode, and the sulfhydryl pretreatment process for nonsulfhydryl molecules can achieve contact with traditional noble metal nanomaterials to achieve Raman signal enhancement. As a result, in addition to the complexity of this process, the number of sulfhydryl probe molecules is limited, and the application of SERS detection is further greatly restricted.…”

“…If the target molecule has a complex matrix, this will hinder its access to plasmonic nanostructures and reduce the enhancement of the Raman signal. However, if preprocessing is performed to separate the target molecules to be detected, it will be a cumbersome procedure, which violates the important performance of SERS rapid detection. − A lot of research has been undertaken to show that the aromatic compounds p -mercaptoaniline (PATP) and p -mercaptonitrobenzene (PNTP) adsorbed on plasmonic nanostructures are catalyzed into an azo material called p -mercaptoazobenzene (DMAB) with the aid of plasmon through plasmon-catalyzed coupling reactions. − The p -mercaptobenzoic acid (pMBA) molecule is selected as the probe molecule because of its prominent characteristic peaks of 1075 and 1590 cm –1 in SERS. , However, these model molecules are all used in the traditional sulfhydryl bonding mode, and the sulfhydryl pretreatment process for nonsulfhydryl molecules can achieve contact with traditional noble metal nanomaterials to achieve Raman signal enhancement. As a result, in addition to the complexity of this process, the number of sulfhydryl probe molecules is limited, and the application of SERS detection is further greatly restricted.…”