Application of a 2D Molybdenum Telluride in SERS Detection of Biorelevant Molecules

Two-dimensional (2D) transition-metal dichalcogenides have become promising candidates for surface-enhanced Raman spectroscopy (SERS), but currently very few examples of detection of relevant molecules are available. Herein, we show the detection of the lipophilic disease marker beta-sitosterol on few-layered MoTe2 films. The chemical vapor deposition (CVD)-grown films are capable of nanomolar detection, exceeding the performance of alternative noble-metal surfaces. We confirm that the enhancement occurs through the chemical enhancement (CE) mechanism via formation of a surface-analyte complex, which leads to an enhancement factor of approximate to 10(4), as confirmed by Fourier transform infrared (FTIR), UV-vis, and cyclic voltammetry (CV) analyses and density functional theory (DFT) calculations. Low values of signal deviation over a seven-layered MoTe2 film confirms the homogeneity and reproducibility of the results in comparison to noble-metal substrate analogues. Furthermore, beta-sitosterol detection within cell culture media, a minimal loss of signal over 50 days, and the opportunity for sensor regeneration suggest that MoTe2 can become a promising new SERS platform for biosensing.Peer reviewe

Can Plasmon Change Reaction Path? : Decomposition of Unsymmetrical Iodonium Salts as an Organic Probe

Plasmon-assisted transformations of organic compounds represent a novel opportunity for conversion of light to chemical energy at room temperature. However, the mechanistic insights of interaction between plasmon energy and organic molecules is still under debate. Herein, we proposed a comprehensive study of the plasmon-assisted reaction mechanism using unsymmetric iodonium salts (ISs) as an organic probe. The experimental and theoretical analysis allow us to exclude the possible thermal effect or hot electron transfer. We found that plasmon interaction with unsymmetrical ISs led to the intramolecular excitation of electron followed by the regioselective cleavage of C–I bond with the formation of electron-rich radical species, which cannot be explained by the hot electron excitation or thermal effects. The high regioselectivity is explained by the direct excitation of electron to LUMO with the formation of a dissociative excited state according to quantum-chemical modeling, which provides novel opportunities for the fine control of reactivity using plasmon energy.Peer reviewe

Selective methane chemiresistive detection using MWCNTs array decorated by metal organic framework layer

Methane as a main component of natural gas, but simultaneously an explosive compound with pronounced negative environmental impact. Therefore, methane should be detected with high precision and reliability. However, the inertness and non-polar nature of methane is limiting its simple detection (e.g., by a chemiresistive approach) living a gap in sensing solution. In this paper, we propose a selective chemiresistive methane sensor consisting of abundant carbon materials (multi-walled carbon nanotubes - MWCNTs) with a metal-organic framework (PCN-14). The sensor is based on decorating a non-ordered array of MWCNTs with PCN-14, which is known to have high selectivity towards methane. The methane molecules are selectively entrapped by PCN-14 pores, which significantly affect the resistance of created hybrid materials. As a result, we could detect methane under air pressure and at room temperature, with a negligible false response from other interfering gases or moisture (except hydrogen or ethane). Despite its extreme simplicity, our chemiresistive sensor does not require chemical reaction or material-destructive binding/oxidation of methane. Therefore, long operation time and sensor stability were expected and experimentally confirmed. Finally, the initial resistance of MWCNTs-PСN-14 hybrid materials was adjusted to be measurable by a portative multimeter range, which makes our approach very simple and technically undemanding

Сan Plasmon Change Reaction Path? An Unprecedented Regioselective Decomposition of Unsymmetrical Iodonium Salts

Plasmon-assisted transformations of organic compounds represent a novel opportunity for conversion of light to chemical energy at room temperature. Herein, we propose a comprehensive investigation of plasmon-triggered decomposition of iodonium salts containing various substituents (ISs). We found that plasmon interaction with unsymmetrical ISs led to the intramolecular excitation of electron followed by the regioselective cleavage of C–I bond with the formation of electron-rich radical species. Such unprecedented C–I cleavage brings the possibility of selective surface modification using ISs. The high regioselectivity is explained by the direct excitation of electron to LUMO with the formation of dissociative excited state ac-cording to quantum-chemical modeling.</p

Unveiling the role of chemical and electronic structure in plasmon-assisted homolysis of alkoxyamines

The excitation of localized plasmon resonance on nanoparticles followed by the interaction with organic molecules leads to new pathways of chemical reactions. Although a number of physical factors (temperature, illumination regime, type of nanoparticles, etc.) are affecting this process, the role of the chemical factors is underestimated. Challenging this assumption, here we studied the kinetic of plasmon-induced homolysis of five alkoxyamines (AAs) with different chemical and electronic structures using electron paramagnetic resonance (EPR). The kinetic data revealed the dependence of plasmonic homolysis rate constant (kd) with the HOMO energy of AAs, which cannot be described by the kinetic parameters derived from thermal homolysis experiments. The observed trend in kd allowed to suggest the key role of intramolecular excitation mechanism supported by the TDFDT calculations, additional spectroscopic characterization, and control experiments. Our work sheds light on the role of the electronic structure of organic molecules in plasmonic chemistry