Plasmonic Harvesting of Light Energy for Suzuki Coupling Reactions

Thermo-photo catalysis: a whole greater than the sum of its parts

Thermo-photo catalysis, which is the catalysis with the participation of both thermal and photo energies, not only reduces the large energy consumption of thermal catalysis but also addresses the low efficiency of photocatalysis. As a whole greater than the sum of its parts, thermo-photo catalysis has been proven as an effective and promising technology to drive chemical reactions. In this review, we first clarify the definition (beyond photo-thermal catalysis and plasmonic catalysis), classification, and principles of thermo-photo catalysis and then reveal its superiority over individual thermal catalysis and photocatalysis. After elucidating the design principles and strategies toward highly efficient thermo-photo catalytic systems, an ample discussion on the synergetic effects of thermal and photo energies is provided from two perspectives, namely, the promotion of photocatalysis by thermal energy and the promotion of thermal catalysis by photo energy. Subsequently, state-of-the-art techniques applied to explore thermo-photo catalytic mechanisms are reviewed, followed by a summary on the broad applications of thermo-photo catalysis and its energy management toward industrialization. In the end, current challenges and potential research directions related to thermo-photo catalysis are outlined.

Mechanistic insight into deep holes from interband transitions in Palladium nanoparticle photocatalysts

Utilizing hot electrons generated from localized surface plasmon resonance is of widespread interest in the photocatalysis of metallic nanoparticles. However, hot holes, especially generated from interband transitions, have not been fully explored for photocatalysis yet. In this study, a photocatalyzed Suzuki-Miyaura reaction using mesoporous Pd nanoparticle photocatalyst served as a model to study the role of hot holes. Quantum yields of the photocatalysts increase under shorter wavelength excitations and correlate to “deeper” energy of the holes from the Fermi level. This work suggests that deeper holes in the d-band catalyze the oxidative addition of aryl halide R-X onto Pd⁰ at the nanoparticles' surface to form R-Pd^II-X complex, thus accelerating the rate-determining step of the catalytic cycle. The hot electrons do not play a decisive role. In the future, catalytic mechanisms induced by deep holes should deserve as much attention as the well-known hot electron transfer mechanism.

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Comparison of quantum yield across different wavelengths

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Interband transitions from shorter wavelength excitation offering deeper holes

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Deeper holes with stronger oxidizing power for higher quantum yield

Anisotropic Plasmonic Pd-Tipped Au Nanorods for Near-Infrared Light-Activated Photoacoustic Imaging Guided Photothermal-Photodynamic Cancer Therapy

The integration of photothermal therapy (PTT) and photodynamic therapy (PDT) has become a promising cancer treatment method. Herein, anisotropic metal hetero-nanostructure Pd-tipped Au nanorods (PTA NRs) were fabricated, which exhibit...

Bimetallic Janus Nanocrystals: Syntheses and Applications

Bimetallic Janus nanocrystals have received considerable interest in recent years owing to their unique properties and niche applications. The side-by-side distribution of two distinct metals provides a flexible platform for tailoring the optical and catalytic properties of nanocrystals. First, a brief introduction to the structural features of bimetallic Janus nanocrystals, followed by an extensive discussion of the synthetic approaches, is given. The strategies and experimental controls for achieving the Janus structure, as well as the mechanistic understandings, are specifically discussed. Then, a number of intriguing properties and applications enabled by the Janus nanocrystals are highlighted. Finally, this article is concluded with future directions and outlooks with respect to both syntheses and applications of this new class of functional nanomaterials.

Exploiting the upconversion luminescence, Lewis acid catalytic and photothermal properties of lanthanide-based nanomaterials for chemical and polymerization reactions

Lanthanide-based nanocrystals possess three unique physical properties that make them attractive for facilitating photoreactions, namely photon upconversion, Lewis acid catalytic activity and photothermal effect. When co-doped with suitable sensitizer and...

Mono- and Bimetallic Nanoparticles Stabilized by an Aromatic Polymeric Network for a Suzuki Cross-Coupling Reaction

This work addresses the Suzuki cross-coupling between 4-bromoanisole (BrAn) and phenylboronic acid (PBA) in an environmentally benign ethanol-water solvent catalysed by mono- (Pd) and bimetallic (PdAu, PdCu, PdZn) nanoparticles (NPs) stabilised within hyper-cross-linked polystyrene (HPS) bearing tertiary amino groups. Small Pd NPs of about 2 nm in diameters were formed and stabilized by HPS independently in the presence of other metals. High catalytic activity and complete conversion of BrAn was attained at low Pd loading. Introduction of Zn to the catalyst composition resulted in the formation of Pd/Zn/ZnO NPs, which demonstrated nearly double activity as compared to Pd/HPS. Bimetallic core-shell PdAu/HPS samples were 3-fold more active as compared to Pd/HPS. Both Pd/HPS and PdAu/HPS samples revealed promising stability confirmed by catalyst recycling in repeated reaction runs.

Selective Enhancement of Surface and Bulk E-Field within Porous AuRh and AuRu Nanorods

A variety of multisegmented nanorods (NRs) composed of dense Au and porous Rh and Ru segments with lengths controlled down to ca. 10 nm are synthesized within porous anodic aluminum oxide membranes. Despite the high Rh and Ru porosity (i.e., ∼40%), the porous metal segments are able to efficiently couple with the longitudinal localized surface plasmon resonance (LSPR) of Au NRs. Finite-difference time-domain simulations show that the LSPR wavelength can be precisely tuned by adjusting the Rh and Ru porosity. Additionally, light absorption inside Rh and Ru segments and the surface electric field (E-field) at Rh and Ru can be independently and selectively enhanced by varying the position of the Rh and Ru segment within the Au NR. The ability to selectively control and decouple the generation of high-energy, surface hot electrons and low-energy, bulk hot electrons within photocatalytic metals such as Rh and Ru makes these bimetallic structures great platforms for fundamental studies in plasmonics and hot-electron science.

Palladium cubes with Pt shell deposition for localized surface plasmon resonance enhanced photodynamic and photothermal therapy of hypoxic tumors

Multifunctional phototherapy nanoagents for imaging-guided synergistic photothermal therapy (PTT) and photodynamic therapy (PDT) are highly desirable in the field of solid tumor therapy. Nevertheless, the tumor microenvironment (TME) inherently associated with hypoxia significantly hampers the photodynamic effect of these multifunctional nanoagents. Herein, Pd nanocubes coated with an ultrathin Pt shell were prepared and further conjugated with fluorescein labeled and thiol functionalized polyethylene glycol (FITC-PEG-SH) (denoted as Pd@Pt-PEG). The deposition of a Pt shell on Pd nanocubes not only enhances the photothermal performance, exhibiting excellent hyperthermia outcomes and impressive photothermal (PT) imaging quality, but also leads to the formation of singlet oxygen (¹O₂) induced by plasmonic excitation. In the meantime, the catalytic activity of the Pt layer is enhanced by electronic coupling and the plasmonic effect, which induces the decomposition of endogenous overexpressed hydrogen peroxide (H₂O₂) in tumors to generate O₂ for conquering TME and augmenting ¹O₂ generation for efficacious tumor cell apoptosis. The modification of FITC-PEG-SH improves the biocompatibility and provides outstanding fluorescence (FL) imaging properties. Upon NIR laser irradiation, Pd@Pt-PEG allows in situ O₂ generation and dual-mode imaging-guided synergistic PTT/PDT that effectively kills hypoxic tumor cells, which makes it a promising nanotherapeutic agent for enhanced tumor therapy.

Nanostructured Photothermal Materials for Environmental and Catalytic Applications

Solar energy is a green and sustainable clean energy source. Its rational use can alleviate the energy crisis and environmental pollution. Directly converting solar energy into heat energy is the most efficient method among all solar conversion strategies. Recently, various environmental and energy applications based on nanostructured photothermal materials stimulated the re-examination of the interfacial solar energy conversion process. The design of photothermal nanomaterials is demonstrated to be critical to promote the solar-to-heat energy conversion and the following physical and chemical processes. This review introduces the latest photothermal nanomaterials and their nanostructure modulation strategies for environmental (seawater evaporation) and catalytic (C1 conversion) applications. We present the research progress of photothermal seawater evaporation based on two-dimensional and three-dimensional porous materials. Then, we describe the progress of photothermal catalysis based on layered double hydroxide derived nanostructures, hydroxylated indium oxide nanostructures, and metal plasmonic nanostructures. Finally, we present our insights concerning the future development of this field.

Shape-Dependent Catalytic Activity of Gold and Bimetallic Nanoparticles in the Reduction of Methylene Blue by Sodium Borohydride

In this study the catalytic activity of different gold and bimetallic nanoparticle solutions towards the reduction of methylene blue by sodium borohydride as a model reaction is investigated. By utilizing differently shaped gold nanoparticles, i.e., spheres, cubes, prisms and rods as well as bimetallic gold–palladium and gold–platinum core-shell nanorods, we evaluate the effect of the catalyst surface area as available gold surface area, the shape of the nanoparticles and the impact of added secondary metals in case of bimetallic nanorods. We track the reaction by UV/Vis measurements in the range of 190–850 nm every 60 s. It is assumed that the gold nanoparticles do not only act as a unit transferring electrons from sodium borohydride towards methylene blue but can promote the electron transfer upon plasmonic excitation. By testing different particle shapes, we could indeed demonstrate an effect of the particle shape by excluding the impact of surface area and/or surface ligands. All nanoparticle solutions showed a higher methylene blue turnover than their reference, whereby gold nanoprisms exhibited 100% turnover as no further methylene blue absorption peak was detected. The reaction rate constant k was also determined and revealed overall quicker reactions when gold or bimetallic nanoparticles were added as a catalyst, and again these were highest for nanoprisms. Furthermore, when comparing gold and bimetallic nanorods, it could be shown that through the addition of the catalytically active second metal platinum or palladium, the dye turnover was accelerated and degradation rate constants were higher compared to those of pure gold nanorods. The results explore the catalytic activity of nanoparticles, and assist in exploring further catalytic applications.

On the Roles of Electron Transfer in Catalysis by Nanoclusters and Nanoparticles

Electron transfer plays a major role in chemical reactions and processes, and this is particularly true of catalysis by nanomaterials. The advent of metal nanoparticle (NP) catalysts, recently including atomically precise nanoclusters (NCs) as parts of nanocatalyst devices has brought increased control of the relationship between NP and NC structures and their catalytic functions. Consequently, the molecular definition of these new nanocatalysts has allowed a better understanding and management of various kinds of electron transfer involved in the catalytic processes. This Minireview brings a chemist's view of several major aspects of electron-transfer functions concerning NPs and NCs in catalytic processes. Particular focus concerns the role of NPs and NCs as electron reservoirs and light-induced antenna in catalytic processes from H₂ generation to more complex reactions and sustainable energy production.

Gold Nanorods: The Most Versatile Plasmonic Nanoparticles

Gold nanorods (NRs), pseudo-one-dimensional rod-shaped nanoparticles (NPs), have become one of the burgeoning materials in the recent years due to their anisotropic shape and adjustable plasmonic properties. With the continuous improvement in synthetic methods, a variety of materials have been attached around Au NRs to achieve unexpected or improved plasmonic properties and explore state-of-the-art technologies. In this review, we comprehensively summarize the latest progress on Au NRs, the most versatile anisotropic plasmonic NPs. We present a representative overview of the advances in the synthetic strategies and outline an extensive catalogue of Au-NR-based heterostructures with tailored architectures and special functionalities. The bottom-up assembly of Au NRs into preprogrammed metastructures is then discussed, as well as the design principles. We also provide a systematic elucidation of the different plasmonic properties associated with the Au-NR-based structures, followed by a discussion of the promising applications of Au NRs in various fields. We finally discuss the future research directions and challenges of Au NRs.

Ag-decorated GaN for high-efficiency photoreduction of carbon dioxide into tunable syngas under visible light

Visible light-driven photoreduction of CO₂and H₂O to tunable syngas is an appealing strategy for both artificial carbon neutral and Fischer-Tropsch processes. However, the development of photocatalysts with high activity and selectivity remains challenging. For this case, we here design a hybrid catalyst, synthesized byin situdeposition of Ag crystals on GaN nanobelts, that delivers a tunable H₂/CO ratio between 0.5 and 3 under visible light irradiation (λ > 400 nm). The obtained photocatalyst delivers a maximal turnover frequency value of 3.85 h^-1and a corresponding yield rate of 2.12 mmol h^-1g^-1for CO production, while the photocatalytic activity keeps stable during five cycling tests. Additionally, syngas can be detected even atλ > 600 nm. Experiments and mechanistic studies reveal that the existence of Ag crystals not only extends the light absorption region but also promotes the charge transfer efficiency, and thereby leading to a photocatalytic improvement. Accordingly, the present work affords an opportunity for developing an efficient photo-driven system by using solar energy to alleviate CO₂emissions.

Recent advances in plasmon-enhanced Raman spectroscopy for catalytic reactions on bifunctional metallic nanostructures

Metallic nanostructures exhibit superior catalytic performance for diverse chemical reactions and the in-depth understanding of reaction mechanisms requires versatile characterization methods. Plasmon-enhanced Raman spectroscopy (PERS), including surface-enhanced Raman spectroscopy (SERS), shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS), and tip-enhanced Raman spectroscopy (TERS), appears as a powerful technique to characterize the Raman fingerprint information of surface species with high chemical sensitivity and spatial resolution. To expand the range of catalytic reactions studied by PERS, catalytically active metals are integrated with plasmonic metals to produce bifunctional metallic nanostructures. In this minireview, we discuss the recent advances in PERS techniques to probe the chemical reactions catalysed by bifunctional metallic nanostructures. First, we introduce different architectures of these dual-functionality nanostructures. We then highlight the recent works using PERS to investigate important catalytic reactions as well as the electronic and catalytic properties of these nanostructures. Finally, we provide some perspectives for future PERS studies in this field.

Tip-Enhanced Raman Analysis of Plasmonic and Photocatalytic Properties of Copper Nanomaterials

Theoretical predictions suggest that, in addition to gold (Au) and silver (Ag), several other metals such as copper (Cu) and aluminum (Al) can be used as plasmonic materials. However, their plasmonic and photocatalytic properties remain poorly understood. In this contribution, we employed tip-enhanced Raman spectroscopy to examine photocatalytic properties of Cu nanowires and nanocubes (CuNWs and CuNCs). Our results show that both CuNWs and CuNCs demonstrate a far more efficient photocatalytic dimerization of 4-nitrobenzenethiol to 4,4'-dimercaptoazobenzene than Au nano and microplates. We also found that CuNWs and CuNCs can neither reduce 4-mercaptobenzoic acid (4-MBA) to the corresponding aromatic alcohol nor dearboxylate it forming benzenethiol. We infer that this is due to a unique coordination of 4-MBA on Cu surfaces that was only rarely observed on Au and Ag nanomaterials. Finally, we found that Cu nanostructures can oxidize 4-mercapto-phenyl-methanol to 4-MBA, which was previously only observed on gold-platinum nanoplates.

Seagrass-inspired design of soft photocatalytic sheets based on hydrogel-integrated free-standing 2D nanoassemblies of multifunctional nanohexagons

Natural leaves are virtually two-dimensional (2D) flexible photocatalytic system. In particular, seagrass can efficiently harvest low-intensity sunlight to drive photochemical reactions continuously in an aqueous solution. To mimic this process, we present a novel 2D hydrogel-integrated photocatalytic sheet based on free-standing nanoassemblies of multifunctional nanohexagons (mNHs). The mNHs building blocks is made of plasmonic gold nanohexagons (NHs) decorated with Pd nanoparticles in the corners and CdS nanoparticles throughout their exposed surfaces. The mNHs can self-assemble into free-standing 2D nanoassemblies and be integrated with thin hydrogel films, which can catalyze chemical reactions under visible light illumination. Hydrogels are translucent, porous, and soft, allowing for continuous photochemical conversion in an aqueous environment. Using methylene blue (MB) as a model system, we demonstrate a soft seagrass-like photodegradation design, which offers high efficiency, continuous operation without the need of catalyst regeneration, and omnidirectional light-harvesting capability under low-intensity sunlight irradiation, defying their rigid substrate-supported random aggregates and solution-based discrete counterparts.

In-situ nanospectroscopic imaging of plasmon-induced two-dimensional [4+4]-cycloaddition polymerization on Au(111)

Plasmon-induced chemical reactions (PICRs) have recently become promising approaches for highly efficient light-chemical energy conversion. However, an in-depth understanding of their mechanisms at the nanoscale still remains challenging. Here, we present an in-situ investigation by tip-enhanced Raman spectroscopy (TERS) imaging of the plasmon-induced [4+4]-cycloaddition polymerization within anthracene-based monomer monolayers physisorbed on Au(111), and complement the experimental results with density functional theory (DFT) calculations. This two-dimensional (2D) polymerization can be flexibly triggered and manipulated by the hot carriers, and be monitored simultaneously by TERS in real time and space. TERS imaging provides direct evidence for covalent bond formation with ca. 3.7 nm spatial resolution under ambient conditions. Combined with DFT calculations, the TERS results demonstrate that the lateral polymerization on Au(111) occurs by a hot electron tunneling mechanism, and crosslinks form via a self-stimulating growth mechanism. We show that TERS is promising to be plasmon-induced nanolithography for organic 2D materials.

Electric Field Assisted Femtosecond Laser Preparation of Au@TiO2 Composites with Controlled Morphology and Crystallinity for Photocatalytic Degradation

TiO₂ is popular in photocatalytic degradation dye pollutants due to its abundance and its stability under photochemical conditions. Au loaded TiO₂ can achieve efficient absorption of visible light and deal with the problem of low conversion efficiency for solar energy of TiO₂. This work presents a new strategy to prepare Au nanoparticles-loaded TiO₂ composites through electric−field−assisted temporally−shaped femtosecond laser liquid-phase ablation of Au³⁺ and amorphous TiO₂. By adjusting the laser pulse delay and electric field parameters, gold nanoparticles with different structures can be obtained, such as nanospheres, nanoclusters, and nanostars (AuNSs). AuNSs can promote the local crystallization of amorphous TiO₂ in the preparation process and higher free electron density can also be excited to work together with the mixed crystalline phase, hindering the recombination between carriers and holes to achieve efficient photocatalytic degradation. The methylene blue can be effectively degraded by 86% within 30 min, and much higher than the 10% of Au nanoparticles loaded amorphous TiO₂. Moreover, the present study reveals the crystallization process and control methods for preparing nanoparticles by laser liquid ablation, providing a green and effective new method for the preparation of high-efficiency photocatalytic materials.

Visible light-driven novel Bi2Ti2O7/CaTiO3 composite photocatalyst with enhanced photocatalytic activity towards NO removal

Photocatalysis is regarded as a promising technology for removal of nitrogen oxide (NO), however, the low photocatalytic efficiencies under visible light irradiation and the deactivation of the photocatalyst are as yet the significant issues that should be addressed. In this work, visible-light-driven Bi₂Ti₂O₇/CaTiO₃ heterojunction composites were synthesized by a facile in-situ hydrothermal method. The Bi₂Ti₂O₇/CaTiO₃ composites displayed superior visible light photocatalytic activity than pure CaTiO₃ and pure Bi₂Ti₂O₇ in the removal of NO at the 600 ppb level in air. Among all the composites, Bi₂Ti₂O₇/CaTiO₃ containing 20 wt% Bi₂Ti₂O₇ exhibited the best photocatalytic activity, achieving a maximum removal efficiency of 59%. The improved photocatalytic performance is mainly attributed to the strong visible-light-absorbing ability, the presence of an appropriate density of oxygen vacancy defects and the formation of heterojunction between CaTiO₃ and Bi₂Ti₂O₇, resulting in an efficient charge separation at the interface as proven by photoluminescence (PL) and photo-induced current measurements. According to trapping experiments and spin-trapping ESR analysis, the ^•O₂^- and h⁺ are the principal reactive species involved in the photocatalytic NO removal. In addition, the as-obtained Bi₂Ti₂O₇/CaTiO₃ composite showed good chemical stability, which is beneficial for practical applications in air pollution removal.

Encapsulating Copper Nanocrystals into Metal-Organic Frameworks for Cascade Reactions by Photothermal Catalysis

Composite materials with multifunctional properties usually possess synergetic effects in catalysis toward cascade reactions. In this work, a facile strategy to the encapsulation of octahedral Cu₂ O nanocrystals (NCs) by metal-organic frameworks (MOFs) is reported, and an oriented growth of MOF enclosures (namely, HKUST-1) around Cu₂ O NCs with desired feedstock ratio is achieved. The strategy defines the parameter range that precisely controls the etching rate of metal oxide and the MOF crystallization rate. Finally, the Cu@HKUST-1 composites with uniform morphology and controlled MOF thickness have been successfully fabricated after the reduction of Cu₂ O to Cu NCs in HKUST-1. The integration of Cu NCs properties with MOF advantages helps to create a multifunctional catalyst, which exhibits cooperative catalytic activity and improved recyclability toward the one-pot cascade reactions under mild conditions involving visible-light irradiation. The superior performance can be attributed to the plasmonic photothermal effect of Cu NCs, while HKUST-1 shell provides Lewis acid sites, substrates and H₂ enrichment, and stabilizes the Cu cores.

A Hierarchical-Structured Impeller with Engineered Pd Nanoparticles Catalyzing Suzuki Coupling Reactions for High-Purity Biphenyl

Suzuki cross-coupling reactions catalyzed by palladium are authoritative protocols in fine-chemical synthesis. Mass transfer and catalyst activity are both significant factors affecting the reaction efficiency in heterogeneous reactions. Although the holistic catalysts hold great promise in heterogeneous reactions due to the enhanced mass transport and convenient recycling, the unsatisfied catalytic activity has impeded further large-scale applications. In addition, another pronounced barrier is the product separation in the intricate system. Here, the catalytic production and separation of biphenyl (purity of 99.7%) were achieved by integrating the Suzuki cross-coupling reactions and the crystallization separation for the first time. A hierarchical-structured impeller with Pd nanoparticles (NPs) loaded on the Ni(OH)₂ nanosheets was prepared to catalyze the Suzuki reactions for bromobenzene, which exhibits a high turnover frequency (TOF) value of 25,976 h^-1 and a yield of 99.5%. The X-ray absorption fine structure (XAFS) analysis has unveiled that the electron transfer between the Pd NPs and Ni(OH)₂ accounts for the greatly enhanced catalytic activity. The findings inspire new insights toward rational engineering of highly efficient holistic catalysts for Suzuki reaction, and the innovative integrated technology offers an avenue for the separation and collection of products.

Metal-Organic Framework Membranes Encapsulating Gold Nanoparticles for Direct Plasmonic Photocatalytic Nitrogen Fixation

Photocatalytic nitrogen fixation reaction can harvest the solar energy to convert the abundant but inert N₂ into NH₃. Here, utilizing metal-organic framework (MOF) membranes as the ideal assembly of nanoreactors to disperse and confine gold nanoparticles (AuNPs), we realize the direct plasmonic photocatalytic nitrogen fixation under ambient conditions. Upon visible irradiation, the hot electrons generated on the AuNPs can be directly injected into the N₂ molecules adsorbed on Au surfaces. Such N₂ molecules can be additionally activated by the strong but evanescently localized surface plasmon resonance field, resulting in a supralinear intensity dependence of the ammonia evolution rate with much higher apparent quantum efficiency and lower apparent activation energy under stronger irradiation. Moreover, the gas-permeable Au@MOF membranes, consisting of numerous interconnected nanoreactors, can ensure the dispersity and stability of AuNPs, further facilitate the mass transfer of N₂ molecules and (hydrated) protons, and boost the plasmonic photocatalytic reactions at the designed gas-membrane-solution interface. As a result, an ammonia evolution rate of 18.9 mmol g_Au^-1 h^-1 was achieved under visible light (>400 nm, 100 mW cm^-2) with an apparent quantum efficiency of 1.54% at 520 nm.

Control of Chemical Reaction Pathways by Light-Matter Coupling

Because plasmonic metal nanostructures combine strong light absorption with catalytically active surfaces, they have become platforms for the light-assisted catalysis of chemical reactions. The enhancement of reaction rates by plasmonic excitation has been extensively discussed. This review focuses on a less discussed aspect: the induction of new reaction pathways by light excitation. Through commentary on seminal reports, we describe the principles behind the optical modulation of chemical reactivity and selectivity on plasmonic metal nanostructures. Central to these phenomena are excited charge carriers generated by plasmonic excitation, which modify the energy landscape available to surface reactive species and unlock pathways not conventionally available in thermal catalysis. Photogenerated carriers can trigger bond dissociation or desorption in an adsorbate-selective manner, drive charge transfer and multielectron redox reactions, and generate radical intermediates. Through one or more of these mechanisms, a specific pathway becomes favored under light. By improved control over these mechanisms, light-assisted catalysis can be transformational for chemical synthesis and energy conversion.

First-Principles Insights into Plasmon-Induced Catalysis

The size- and shape-controlled enhanced optical response of metal nanoparticles (NPs) is referred to as a localized surface plasmon resonance (LSPR). LSPRs result in amplified surface and interparticle electric fields, which then enhance light absorption of the molecules or other materials coupled to the metallic NPs and/or generate hot carriers within the NPs themselves. When mediated by metallic NPs, photocatalysis can take advantage of this unique optical phenomenon. This review highlights the contributions of quantum mechanical modeling in understanding and guiding current attempts to incorporate plasmonic excitations to improve the kinetics of heterogeneously catalyzed reactions. A range of first-principles quantum mechanics techniques has offered insights, from ground-state density functional theory (DFT) to excited-state theories such as multireference correlated wavefunction methods. Here we discuss the advantages and limitations of these methods in the context of accurately capturing plasmonic effects, with accompanying examples.

Structural Control over Bimetallic Core-Shell Nanorods for Surface-Enhanced Raman Spectroscopy

Bimetallic nanorods are important colloidal nanoparticles for optical applications, sensing, and light-enhanced catalysis due to their versatile plasmonic properties. However, tuning the plasmonic resonances is challenging as it requires a simultaneous control over the particle shape, shell thickness, and morphology. Here, we show that we have full control over these parameters by performing metal overgrowth on gold nanorods within a mesoporous silica shell, resulting in Au-Ag, Au-Pd, and Au-Pt core-shell nanorods with precisely tunable plasmonic properties. The metal shell thickness was regulated via the precursor concentration and reaction time in the metal overgrowth. Control over the shell morphology was achieved via a thermal annealing, enabling a transition from rough nonepitaxial to smooth epitaxial Pd shells while retaining the anisotropic rod shape. The core-shell synthesis was successfully scaled up from micro- to milligrams, by controlling the kinetics of the metal overgrowth via the pH. By carefully tuning the structure, we optimized the plasmonic properties of the bimetallic core-shell nanorods for surface-enhanced Raman spectroscopy. The Raman signal was the most strongly enhanced by the Au core-Ag shell nanorods, which we explain using finite-difference time-domain calculations.

Filamentous fungal in situ biosynthesis of heterogeneous Au/Cd0.5Zn0.5S nano-photocatalyst: A macroscopic assembly strategy for preparing composite mycelial pellets with visible light degradation ability

Visible light degradation is a green and economic technology for sewage treatment receiving widespread attention. Here, the filamentous fungus Phomopsis sp. XP-8 was developed as a bioreactor to successively biosynthesize Cd_0.5Zn_0.5S quantum dots and gold nanoparticles (AuNPs) in situ and formed heterogeneous Au/Cd_0.5Zn_0.5S nano-photocatalyst inside cells. This strategy synchronously mediates the microscopic and macroscopic assembly of zero-dimensional materials by microorganisms. The heterogeneous catalyst functionalized composite mycelium pellets (CMP) not only have excellent visible light degradation activity but some unique characteristics. The outstanding organic dye biosorption capacity of CMP increases the contact rate between organic dyes and nano-catalysts, improving catalytic activity. High mechanical strength makes CMP easy to separate and recycle, which overcomes the difficulty of nano-catalyst recovery after use and avoids creating secondary pollution to the environment. This study not only broadens the means of heterogeneous nano-catalyst synthesis but also provides a new perspective on the macroscopic assembly of nanomaterials.

Plasmonic Photoelectrocatalysis in Copper-Platinum Core-Shell Nanoparticle Lattices

This paper reports that strongly coupled bimetallic core-shell nanoparticle arrays show photoelectrocatalytic activity for hydrogen evolution reactions (HER). We fabricated large-area Cu-Pt nanoparticle lattices by combining top-down lithography and solution-based chemistry. These coupled lattices support two different types of plasmon modes, localized surface plasmons from individual particles and surface lattice resonances (SLRs) from the 2D lattice, that increased HER catalytic activity under white-light illumination up to 60%. Comparing photoelectrocatalytic performances of the two plasmon modes at different wavelength ranges, we found that SLRs had two-fold activity enhancement over that from localized surface plasmons.

Recent Progress in Plasmonic Hybrid Photocatalysis for CO2 Photoreduction and C–C Coupling Reactions

Plasmonic hybrid nanostructures have been investigated as attractive heterogeneous photocatalysts that can utilize sunlight to produce valuable chemicals. In particular, the efficient photoconversion of CO2 into a stable hydrocarbon with sunlight can be a promising strategy to achieve a sustainable human life on Earth. The next step for hydrocarbons once obtained from CO2 is the carbon–carbon coupling reactions to produce a valuable chemical for energy storage or fine chemicals. For these purposes, plasmonic nanomaterials have been widely investigated as a visible-light-induced photocatalyst to achieve increased efficiency of photochemical reactions with sunlight. In this review, we discuss recent achievements involving plasmonic hybrid photocatalysts that have been investigated for CO and CO2 photoreductions to form multi-carbon products and for C–C coupling reactions, such as the Suzuki–Miyaura coupling reactions.

Understanding and Improving Photocatalytic Activity of Pd-Loaded BiVO4 Microspheres: Application to Visible Light-Induced Suzuki-Miyaura Coupling Reaction

The effective utilization of visible light is required for exploiting photocatalytic reactions in indoor and outdoor environments. In this study, Pd-supported BiVO₄ microspheres (Pd-BiVO₄) were prepared for visible light-induced photocatalytic reactions. Under irradiation with a white light-emitting diode, the obtained Pd-BiVO₄ composite exhibited considerably improved catalytic activity for the decomposition of an organic dye compared with other BiVO₄ catalysts. The Pd-BiVO₄ composite was also effective for catalytic organic transformation via the visible light-induced Suzuki-Miyaura coupling reaction. The photogenerated electrons in the conduction band of BiVO₄ flowed to the Pd nanoparticles and amplified cross-coupling reaction. The influence of the crystal structure and grain size of BiVO₄ and the role of the deposited Pd nanoparticles were fully investigated to elucidate the visible light activity of the catalyst. This system highlights the possibility of an indoor light source with low energy density for sustainable organic transformations.

The dark side of photocatalysis: near-infrared photoredox catalysis for organic synthesis

Near-Infrared photoredox catalysis is now consider as the next evolution of this field.

Efficient photocatalytic chemoselective and stereoselective C–C bond formation over AuPd@N-rich carbon nitride

High unsymmetrical chemoselective Ullmann biaryl products and satisfactory Z-type stereoselective Heck reaction products could be achieved through changing the visible light color over AuPd@N-Rich carbon nitride under mild conditions.

Tip-enhanced Raman imaging of photocatalytic reactions on thermally-reshaped gold and gold–palladium microplates

The plasmonic/photocatalytic properties of thermally-reshaped walled gold–palladium microplates (WAu@PdMPs) have been explored by TERS.

Recent Advances in Plasmon-Promoted Organic Transformations Using Silver-Based Catalysts

Plasmonics has emerged as a promising methodology to promote chemical reactions and has become a field of intense research effort. Ag nanoparticles (NPs) as plasmonic catalysts have been extensively studied because of their remarkable optical properties. This review analyzes the emergence and development of localized surface plasmon resonance (LSPR) in organic chemistry, mainly focusing on the discovery of novel reactions with new mechanisms on Ag NPs. Initially, the basics of LSPR and LSPR-promoted photocatalytic mechanisms are illustrated. Then, the recent advances in plasmonic nanosilver-mediated photocatalysis in organic transformations are highlighted with an emphasis on the related reaction mechanisms. Finally, a proper perspective on the remaining challenges and future directions in the field of LSPR-promoted organic transformations is proposed.

Pd nanoparticles as a plasmonic material: synthesis, optical properties and applications

This review provides an overview of current progress in Pd nanoparticles supporting localized surface plasmon resonance and their applications. We begin by analyzing briefly the optical properties of Pd putting particular focus on outlining the origin of its size- and shape-dependent LSPR, high refractive index sensitivity, and high absorption contribution. The differences in the optical behavior with Au and Ag, the primary plasmonic materials, are highlighted. The main strategies to synthesize Pd nanoparticles, pure or hybrid, with well-defined optical properties are then reviewed. In this section, we include only those works that carry out the study of the optical properties of the nanoparticles. The applications of plasmonic Pd nanoparticles are also discussed in detail. This review is concluded with a section devoted to the future perspectives highlighting the most relevant challenges to be addressed to take Pd nanoparticles from the laboratory to real applications.

Gold nanobipyramid-embedded silver-platinum hollow nanostructures for monitoring stepwise reduction and oxidation reactions

Metal hollow nanostructures based on gold nanobipyramids (Au NBPs) are of great interest for the combination of tunable plasmonic resonances and excellent physicochemical properties. Based on the core-shell Au NBP@Ag nanorods with desired sizes, herein we reported the synthesis and growth mechanism of Au NBP-embedded AgPt hollow nanostructures with tunable thickness and size. The Au NBP@AgPt nanoframes were obtained at lower temperature, in which cetyltrimethylammonium bromine (CTAB) was applied as a capping agent to guide the deposition of Pt atoms on the edges and corners of Au NBPs@Ag nanorods. With the increase of reaction temperature, the Au NBP@AgPt nanoframes convert into nanocages due to the atomic migration to the surfaces. The surface plasmon resonance of the Au NBP@AgPt hollow nanostructure shifts from red to blue, which is ascribed to the changes in coverage area and location site of the AgPt alloy. When CTAB was replaced by cetyltrimethylammonium chloride (CTAC), Au NBP@AgPt nanocages dominate the product. The surface roughness and thickness of the nanocages can be controlled by the temperature and the amount of Pt precursor. Moreover, Au NBP@AgPt hollow nanostructures show excellent surface-enhanced Raman scattering and exhibit remarkable stability in harsh environments. Taking into account the advantages of the plasmonic property (Au NBPs), catalytic activity (Pt) and plasmon-enhanced signal (Ag), the Au NBP@AgPt hollow nanostructures are a promising candidate for technological applications in catalytic reactions.