Plasmon-based triggering leads to an effective increase of material catalytic activity in a number of relevant photoelectrochemical transformations, including nitrogen reduction for the production of ammonia. The efficiency of the plasmon assistance can be significantly increased through the rational design of hybrid photoelectrodes, e.g., by placing a redox-active material at plasmonic hot spots that may arise between two coupled nanostructures. In this work, we describe the creation and utilization of chiral plasmon-active hybrid structures (based on the so-called gold helicoids) coupled with redox-active 2H-MoS2. The chiral plasmon-active gold nanoparticles (with the same or opposite chirality) were spatially separated by thin two-dimensional (2D) flakes to reach mutual plasmon coupling between them. Using numerical simulations and SERS measurements, the dependence of the local enhancement of the electric field (EF) inside the created plasmon-active diastereomer consisting of Au helicoid-2D MoS2-Au helicoid "sandwich structure", on the mutual chirality of the nanoparticles is demonstrated. It is found that the plasmon energy is more efficiently "concentrated" in the MoS2 space using the "chiral trap" of light energy (i.e., chiral plasmonic lock), even in the case where the chiral handedness of Au nanoparticles is matching. The created hybrid structures were subsequently used for nitrogen reduction and ammonia production proceeding on the MoS2 surface. A clear dependence of the catalytic activity of MoS2 on the matching or mismatching of Au helicoid chiralities (and related local value of EF) is observed. In particular, a two-time increase in the ammonia yield is obtained in the case of matching chirality, compared to that in the case of mismatched configuration or the control experiments performed with nonchiral Au nanocubes. Hence, the utilization of chiral plasmonic nanoparticles and their dimers (or multimers) provides an additional opportunity for even more effective photosensibilization of redox-active materials.

• Klíčová slova
• MoS2 flakes, chiral gold helicoids, nitrogen reduction, plasmon coupling, plasmon-assisted chemistry,
• Publikační typ
• časopisecké články MeSH

Distinct advantages of surface enhanced Raman scattering (SERS) in molecular detection can benefit the enantioselective discrimination of specific molecular configurations. However, many of the recent methods still lack versatility and require customized anchors to chemically interact with the studied analyte. In this work, we propose the utilization of helicoid-shaped chiral gold nanoparticles arranged in an ordered array on a gold grating surface for enantioselective SERS recognition. This arrangement ensured a homogeneous distribution of chiral plasmonic hot spots and facilitated the enhancement of the SERS response of targeted analytes through plasmon coupling between gold helicoid multimers (formed in the grating valleys) and adjacent regions of the gold grating. Naproxen enantiomers (R(+) and S(-)) were employed as model compounds, revealing a clear dependence of their SERS response on the chirality of the gold helicoids. Additionally, propranolol and penicillamine enantiomers were used to validate the universality of the proposed approach. Finally, numerical simulations were conducted to elucidate the roles of intensified local electric field and optical helicity density on the SERS signal intensity and on the chirality of the nanoparticles and enantiomers. Unlike previously reported methods, our approach relies on the excitation of a chiral plasmonic near-field and its interaction with the chiral environment of analyte molecules, obviating the need for the enantioselective entrapment of targeted molecules. Moreover, our method is not limited to specific analyte classes and can be applied to a broad range of chiral molecules.

• Klíčová slova
• SERS, chiral gold nanoparticles, enantioselective detection, naproxen, plasmon coupling,
• Publikační typ
• časopisecké články MeSH

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.

• Publikační typ
• časopisecké články MeSH

The chiral recognition of organic compounds is of vital importance in the field of pharmacology and medicine. Unfortunately, the common analytical routes used in this field are significantly restricted by time spent and equipment demands. In this work, we propose an unprecedented alternative, aimed at enantiomer discrimination and estimation of their concentrations in an uncomplicated and instantaneous manner. The proposed approach is based on the creation of an optical fiber probe with two pronounced plasmonic bands attributed to gold and silver. The gold or silver surfaces were grafted with moieties, able to enunciating entrap chiral amines from solution, resulting in a wavelength shift corresponding to each plasmonic metal. As a model compound of chiral amine, we chose the DOPA, also taking in mind its high medical relevancy. For chiral detection, the optical fiber probe was simply immersed in an analytical solution of DOPA, and the selective shift of gold or silver plasmon bands was observed in the reflected light depending on DOPA chirality. The observed shifts depend on the concentration of DOPA enantiomers. In the case of a racemic mixture, the shifts of both plasmonic bands emerge, making possible the simultaneous determination of enantiomer concentrations and their ratio. The analytical cycle takes several minutes and requires very simple laboratory equipment.

• Klíčová slova
• DOPA, chiral detection, fiber-optic probe, instantaneous recognition, racemic mixture, surface plasmon resonance,
• MeSH
• optická vlákna normy   MeSH
• povrchová plasmonová rezonance metody   MeSH
• technologie optických vláken metody   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH