Near-field enhancement by plasmonic antennas for photocatalytic Suzuki-Miyaura cross-coupling reactions

Bridging Gaps in the Synthesis of g-CN/WO3-x for Photocatalytic H2O2 Generation: Insights into S-Scheme Heterojunction and Plasmon-Induced Hot Electrons

This study presents a systematic design for fabricating g-CN/WO3-x S-scheme heterojunctions with plasmonic features (localized surface plasmon resonance (LSPR) and hot electrons) to achieve superb photocatalytic H2O2 production activity. To optimize the synthesis, a rational approach is employed to how synthesis parameters influence the emergence of LSPR and hot electrons in WO3-x and their effect on the heterojunction's performance. As a result of such a comprehensive strategy, the developed synthesis methodology effectively bridges gaps in the literature, addressing underexplored strategies for improving photocatalytic efficiency for the controlled synthesis of the g-CN/WO3-x heterojunction. The plasmonic characteristics attributed to oxygen deficiency in WO3 (WO3-x) and g-CN/WO3-x and interactions of g-CN and WO3-x at the atomic level are further corroborated through a comprehensive analysis employing X-ray photoelectron spectroscopy (XPS), solid-state nuclear magnetic resonance (ssNMR), and electron paramagnetic resonance (EPR). Thanks to the presence of WO3-x, the light-harvesting ability of g-CN/WO3-x heterojunctions spans from the visible to near-infrared region. Moreover, the generation of hot electrons on the surface of WO3-x mitigates electron-hole recombination in the binary heterojunction. Consequently, the g-CN/WO3-x S-scheme heterojunctions synthesized with the optimal recipe provided a superior photocatalytic H2O2 generation rate of 1349.70 μmol·L-1 in 10% (v/v) aqueous methanol solution within 90 min, which is 2.36 and 7.17 times greater than that of pristine g-CN and WO3-x, respectively, superior to other similar photocatalysts tested in photocatalytic H2O2 production. The superb photocatalytic activity of the g-CN/WO3-x heterojunction is attributed to the synergistic effects aroused in the S-scheme heterojunction, promoting efficient charge separation with enhanced redox potentials and plasmon-induced hot electrons that both accelerate reactions through the photothermal effect and serve as additional reducing species. This research broadens the perspective toward constructing nonmetallic plasmonic S-scheme heterojunctions for fields utilizing LSPR phenomena, such as photocatalysis, photonics, and biomedicine.

Continuous photocatalytic C-C coupling achieved using palladium anchored to a covalent organic framework

We firstly reported a single-atom palladium photocatalyst, Pd-Ace-COF, for a continuous C-C coupling reaction. Under visible light irradiation, Pd-Ace-COF efficiently drives C-C coupling to form biphenyl with a >99% yield. Impressively, Pd-Ace-COF exhibits good stability and high activity in the continuous-flow reactor, highlighting its great potential for practical applications.

Design rules for catalysis in single-particle plasmonic nanogap reactors with precisely aligned molecular monolayers

Plasmonic nanostructures can both drive and interrogate light-driven catalytic reactions. Sensitive detection of reaction pathways is achieved by confining optical fields near the active surface. However, effective control of the reaction kinetics remains a challenge to utilize nanostructure constructs as efficient chemical reactors. Here we present a nanoreactor construct exhibiting high catalytic and optical efficiencies, based on a nanoparticle-on-mirror (NPoM) platform. We observe and track pathways of the Pd-catalysed C-C coupling reaction of molecules within a set of nanogaps presenting different chemical surfaces. Atomic monolayer coatings of Pd on the different Au facets enable tuning of the reaction kinetics of surface-bound molecules. Systematic analysis shows the catalytic efficiency of NPoM-based nanoreactors greatly improves on platforms based on aggregated nanoparticles. More importantly, we show Pd monolayers on the nanoparticle or on the mirror play significantly different roles in the surface reaction kinetics. Our data provides clear evidence for catalytic dependencies on molecular configuration in well-defined nanostructures. Such nanoreactor constructs therefore yield clearer design rules for plasmonic catalysis.

Recent Applications of Photothermal Conversion in Organic Synthesis

Photothermal conversion is a novel heating method that has emerged in recent years, wherein certain species can convert light to heat with great efficiency. These photothermal agents have shown immense promise for generating nanoscale thermal gradients under mild, visible light irradiation, providing a pathway for combining photochemistry with thermally driven reactivity. While this novel heating mechanism has been leveraged to great effect for applications such as photothermal therapeutics and steam water purification, it has seen limited use in organic synthesis. This outlook explores instances wherein the photothermal effect was used directly or as a synergistic component to drive organic reactions and postulates how it may be used moving forward.

Au@C/Pt core@shell/satellite supra-nanostructures: plasmonic antenna-reactor hybrid nanocatalysts

Integration of plasmonic nanoantennas with catalytically active reactors in deliberately designed hybrid supra-nanostructures creates a dual-functional materials platform, based upon which precise modulation of catalytic reaction kinetics becomes accomplishable through optical excitations of plasmon resonances. Here, we have developed a multistep synthetic approach that enables us to assemble colloidal Au@C/Pt core@shell/satellite supra-nanostructures, in which the Au core functions as a light-harvesting plasmonic nanoantenna, the Pt satellites act as catalytically active reactors, and the C shell serves as a nanoscale dielectric spacer separating the reactors from the antenna, respectively. By adjusting several synthetic parameters, the size of the Au core, the thickness of the C shell, and the surface coverage of Pt satellites can all be tuned independently. Choosing Pt-catalyzed cascade oxidation of 3,3',5,5'-tetramethylbenzidine in an aerobic aqueous environment as a model reaction, we have systematically studied the detailed kinetic features of the catalytic reactions both in the dark and under visible light illumination over a broad range of reaction conditions, which sheds light on the interplay between plasmonic and catalytic effects in these antenna-reactor nanohybrids. The plasmonic antenna effect can be effectively harnessed to kinetically modulate multiple crucial steps during the cascade reactions, benefiting from plasmon-enhanced interband electronic transitions in the Pt satellites and plasmon-enhanced intramolecular electronic excitations in chromogenic intermediate species. In addition to the plasmonic antenna effect, photothermal transduction derived from plasmonic excitations can also provide significant contributions to the kinetic enhancements under visible light illumination. The knowledge gained from this work serves as important guiding principles for rational design and structural optimization of plasmonic antenna-reactor hybrid nanomaterials, endowing us with enhanced capabilities to kinetically modulate targeted catalytic/photocatalytic molecule-transforming processes through light illumination.

Promises of Plasmonic Antenna-Reactor Systems in Gas-Phase CO2 Photocatalysis

Sunlight-driven photocatalytic CO2 reduction provides intriguing opportunities for addressing the energy and environmental crises faced by humans. The rational combination of plasmonic antennas and active transition metal-based catalysts, known as "antenna-reactor" (AR) nanostructures, allows the simultaneous optimization of optical and catalytic performances of photocatalysts, and thus holds great promise for CO2 photocatalysis. Such design combines the favorable absorption, radiative, and photochemical properties of the plasmonic components with the great catalytic potentials and conductivities of the reactor components. In this review, recent developments of photocatalysts based on plasmonic AR systems for various gas-phase CO2 reduction reactions with emphasis on the electronic structure of plasmonic and catalytic metals, plasmon-driven catalytic pathways, and the role of AR complex in photocatalytic processes are summarized. Perspectives in terms of challenges and future research in this area are also highlighted.

High refractive index dielectric coating on plasmonic nanoantennas for strong visible light absorption in small transition metal nanoparticle reactors

A more practical model for plasmonic core@shell-satellite antenna-reactor photocatalysts is promoted. In contrast to the mainstream view, total light absorption in the Pt nanoparticle (NP) reactors can be further improved by 70% after coating a 10-nm-thick high refractive index TiO₂ shell on the large Ag antenna as a result of more Pt NPs undergoing high absorption enhancement. The enhancement effect is maximized at the electric quadrupole (EQ) resonance. Considering the high refractive index of the TiO₂ coating and the embedding of the Pt NPs, the underlying physics is addressed within classical electrodynamics, making a necessary supplement to the conventional plasmonic near-field enhancement mechanism. These findings provide a general strategy for developing novel, to the best of our knowledge, visible light photocatalysts made of transition metals directly.

Efficient Suzuki-Miyaura cross-coupling reaction by loading trace Pd nanoparticles onto copper-complex-derived Cu/C-700 solid support

The development of efficient carbon-carbon cross-coupling catalysts with low noble metal amounts attracts much attention recently. Herein, a Cu/C-700/Pd nanocomposite is obtained by loading trace Pd²⁺ onto carbon support derived from a novel mononuclear copper complex, {[Cu(POP)₂(Phen)₂]BF₄}. The as-prepared nanomaterial features the facial structure of highly dispersed copper phosphide nanoparticles as well as Pd nanoparticles via neighboring Cu-Pd sites. The Cu/C-700/Pd nanocomposite shows excellent catalytic activity (99.73%) and selectivity in Suzuki-Miyaura cross-coupling reaction, at trace Pd loading (0.43 mol%). Compared with the reported palladium nano catalysts, its advantages are proved. The appealing gateway to this stable, innovative and recyclability, Cu/C-700/Pd nanostructure recommends its beneficial utilization in carbon-carbon coupling and other environmentally friendly processes.