Plasmon-Mediated Solar Energy Conversion via Photocatalysis in Noble Metal/Semiconductor Composites

Plasmon-Induced Hot Electrons in Nanostructured Materials: Generation, Collection, and Application to Photochemistry

Plasmon refers to the coherent oscillation of all conduction-band electrons in a nanostructure made of a metal or a heavily doped semiconductor. Upon excitation, the plasmon can decay through different channels, including nonradiative Landau damping for the generation of plasmon-induced energetic carriers, the so-called hot electrons and holes. The energetic carriers can be collected by transferring to a functional material situated next to the plasmonic component in a hybrid configuration to facilitate a range of photochemical processes for energy or chemical conversion. This article centers on the recent advancement in generating and utilizing plasmon-induced hot electrons in a rich variety of hybrid nanostructures. After a brief introduction to the fundamentals of hot-electron generation and decay in plasmonic nanocrystals, we extensively discuss how to collect the hot electrons with various types of functional materials. With a focus on plasmonic nanocrystals made of metals, we also briefly examine those based upon heavily doped semiconductors. Finally, we illustrate how site-selected growth can be leveraged for the rational fabrication of different types of hybrid nanostructures, with an emphasis on the parameters that can be experimentally controlled to tailor the properties for various applications.

Strong Interactions between Au Nanoparticles and BiVO4 Photoanode Boosts Hole Extraction for Photoelectrochemical Water Splitting

Strong metal-support interaction (SMSI) is widely proposed as a key factor in tuning catalytic performances. Herein, the classical SMSI between Au nanoparticles (NPs) and BiVO4 (BVO) supports (Au/BVO-SMSI) is discovered and used innovatively for photoelectrochemical (PEC) water splitting. Owing to the SMSI, the electrons transfer from V4+ to Au NPs, leading to the formation of electron-rich Au species (Auδ-) and strong electronic interaction (i.e., Auδ--Ov-V4+), which readily contributes to extract photogenerated holes and promote charge separation. Benefitted from the SMSI effect, the as-prepared Au/BVO-SMSI photoanode exhibits a superior photocurrent density of 6.25 mA cm-2 at 1.23 V versus the reversible hydrogen electrode after the deposition of FeOOH/NiOOH cocatalysts. This work provides a pioneering view for extending SMSI effect to bimetal oxide supports for PEC water splitting, and guides the interfacial electronic and geometric structure modulation of photoanodes consisting of metal NPs and reducible oxides for improved solar energy conversion efficiency.

Recent advances and mechanism of plasmonic metal-semiconductor photocatalysis

Benefiting from the unique surface plasmon properties, plasmonic metal nanoparticles can convert light energy into chemical energy, which is considered as a potential technique for enhancing plasmon-induced semiconductor photocatalytic reactions. Due to the shortcomings of large bandgap and high carrier recombination rate of semiconductors, their applications are limited in the field of sustainable and clean energy sources. Different forms of plasmonic nanoparticles have been reported to improve the photocatalytic reactions of adjacent semiconductors, such as water splitting, carbon dioxide reduction, and organic pollutant degradation. Although there are various reports on plasmonic metal-semiconductor photocatalysis, the related mechanism and frontier progress still need to be further explored. This review provides a brief explanation of the four main mechanisms of plasmonic metal-semiconductor photocatalysis, namely, (i) enhanced local electromagnetic field, (ii) light scattering, (iii) plasmon-induced hot carrier injection and (iv) plasmon-induced resonance energy transfer; some related typical frontier applications are also discussed. The study on the mechanism of plasmonic semiconductor complexes will be favourable to develop a new high-performance semiconductor photocatalysis technology.

Schottky Barrier-Based Built-In Electric Field for Enhanced Tumor Photodynamic Therapy

Photodynamic therapy's antitumor efficacy is hindered by the inefficient generation of reactive oxygen species (ROS) due to the photogenerated electron-hole pairs recombination of photosensitizers (PS). Therefore, there is an urgent need to develop efficient PSs with enhanced carrier dynamics. Herein, we designed Schottky junctions composed of cobalt tetroxide and palladium nanocubes (Co3O4@Pd) with a built-in electric field as effective PS. The built-in electric field enhanced photogenerated charge separation and migration, resulting in the generation of abundant electron-hole pairs and allowing effective production of ROS. Thanks to the built-in electric field, the photocurrent intensity and carrier lifetime of Co3O4@Pd were approximately 2 and 3 times those of Co3O4, respectively. Besides, the signal intensity of hydroxyl radical and singlet oxygen increased to 253.4% and 135.9%, respectively. Moreover, the localized surface plasmon resonance effect of Pd also enhanced the photothermal conversion efficiency of Co3O4@Pd to 40.50%. In vitro cellular level and in vivo xenograft model evaluations demonstrated that Co3O4@Pd could generate large amounts of ROS, trigger apoptosis, and inhibit tumor growth under near-infrared laser irradiation. Generally, this study reveals the contribution of the built-in electric field to improving photodynamic performance and provides new ideas for designing efficient inorganic PSs.

Sol-Gel TiO2 Thin Film on Au Nanoparticles for Heterogeneous Plasmonic Photocatalysis

A new, simple method for preparing substrates for photocatalytic applications under visible light is presented. It is based on the preparation of a dense array of gold nanoparticles (AuNPs) by thermal dewetting of a thin gold film followed by spin-coating of a thin TiO2 film prepared by sol-gel chemistry. The photocatalytic properties of these nanocomposite films are studied by surface-enhanced Raman spectroscopy (SERS) following the N-demethylation reaction of methylene blue as a model reaction. This approach shows that the semiconducting layer on the AuNPs can significantly increase the efficiency of the photoinduced reaction. The SERS study also illustrates the influence of parameters such as TiO2 thickness and position (on or under the AuNPs). Ultimately, this study emphasizes that the primary mechanism behind the N-demethylation reaction is both the increase in extinction and the improved electron transfer facilitated by the semiconducting layer. On the other hand, exclusive reliance on photothermal effects is ruled out.

Electrogenerated chemiluminescence imaging of plasmon-induced electrochemical reactions at single nanocatalysts

This study explores plasmon-induced electrochemical reactions on single nanoparticles using electrogenerated chemiluminescence microscopy (ECLM). Under laser irradiation, real-time screening showed lower plasmon-induced reaction efficiency for bimetallic Au@Pt nanoparticles compared to monometallic Au nanoparticles. ECLM offers a high-throughput imaging and precise quantitative approach for analyzing photo-electrochemical conversion at single nanoparticle level, valuable for both theoretical exploration and optimization of plasmonic nanocatalysts.

Photo-enhanced dehydrogenation of formic acid on Pd-based hybrid plasmonic nanostructures

Coupling visible light with Pd-based hybrid plasmonic nanostructures has effectively enhanced formic acid (FA) dehydrogenation at room temperature. Unlike conventional heating to achieve higher product yield, the plasmonic effect supplies a unique surface environment through the local electromagnetic field and hot charge carriers, avoiding unfavorable energy consumption and attenuated selectivity. In this minireview, we summarized the latest advances in plasmon-enhanced FA dehydrogenation, including geometry/size-dependent dehydrogenation activities, and further catalytic enhancement by coupling local surface plasmon resonance (LSPR) with Fermi level engineering or alloying effect. Furthermore, some representative cases were taken to interpret the mechanisms of hot charge carriers and the local electromagnetic field on molecular adsorption/activation. Finally, a summary of current limitations and future directions was outlined from the perspectives of mechanism and materials design for the field of plasmon-enhanced FA decomposition.

UV-to-NIR Harvesting Conjugated Porous Polymer Nanocomposite: Upconversion and Plasmon Expedited Thioether Photooxidation

Photocatalysts capable of harvesting a broad range of the solar spectrum are essential for sustainable chemical transformations and environmental remediation. Herein, we have integrated NIR-absorbing upconversion nanoparticles (UCNP) with UV-Vis absorbing conjugated porous organic polymer (POP) through the in situ multicomponent C-C coupling to fabricate a UC-POP nanocomposite. The light-harvesting ability of UC-POP is further augmented by loading plasmonic gold nanoparticles (AuNP) into UC-POP. A three-times enhancement in the upconversion luminescence is observed upon the incorporation of AuNP in UC-POP, subsequently boosting the photocatalytic activity of UC-POP-Au. The spectroscopic and photoelectrochemical investigations infer the enhanced photocatalytic oxidation of thioethers, including mustard gas simulant by UC-POP-Au compared to POP and UC-POP due to the facile electron-hole pair generation, suppressed exciton recombination, and efficient charge carrier migration. Thus, the unique design strategy of combining plasmonic and upconversion nanoparticles with a conjugated porous organic polymer opens up new vistas towards artificial light harvesting.

A Surface Matrix of Au NPs Decorated Graphdiyne for Multifunctional Laser Desorption/Ionization Mass Spectrometry

The development of the valid strategy to enhance laser desorption/ionization efficiency gives rise to widespread concern in surface-assisted laser desorption/ionization mass spectrometry (SALDI-MS) technology. Herein, a hybrid of Au NP-decorated graphdiyne (Au/GDY) was fabricated and employed as the SALDI-MS matrix for the first time, and a mechanism based on photothermal and photochemical energy conversions was proposed to understand LDI processes. Given theoretical simulations and microstructure characterizations, it was revealed that the formation of a coupled thermal field and internal electric field endow the as-prepared Au/GDY matrix with superior desorption and ionization efficiency, respectively. Moreover, laser-induced matrix ablation introduced strain and defect level into the Au/GDY hybrid, suppressing the recombination of charge carriers and thereby facilitating analyte ionization. The optimized Au/GDY matrix allowed for reliable detection of trace sulfacetamide and visualization of exogenous/endogenous components in biological tissues. This work offers an integrated solution to promote LDI efficiency based on collaborative photothermal conversion and internal electric field, and may inspire the design of novel semiconductor-based surface matrices.

Self-Functionalized Superlattice Nanosensor Enables Glioblastoma Diagnosis Using Liquid Biopsy

Glioblastoma (GBM), the most aggressive and lethal brain cancer, is detected only in the advanced stage, resulting in a median survival rate of 15 months. Therefore, there is an urgent need to establish GBM diagnosis tools to identify the tumor accurately. The clinical relevance of the current liquid biopsy techniques for GBM diagnosis remains mostly undetermined, owing to the challenges posed by the blood-brain barrier (BBB) that restricts biomarkers entering the circulation, resulting in the unavailability of clinically validated circulating GBM markers. GBM-specific liquid biopsy for diagnosis and prognosis of GBM has not yet been developed. Here, we introduce extracellular vesicles of GBM cancer stem cells (GBM CSC-EVs) as a previously unattempted, stand-alone GBM diagnosis modality. As GBM CSCs are fundamental building blocks of tumor initiation and recurrence, it is desirable to investigate these reliable signals of malignancy in circulation for accurate GBM diagnosis. So far, there are no clinically validated circulating biomarkers available for GBM. Therefore, a marker-free approach was essential since conventional liquid biopsy relying on isolation methodology was not viable. Additionally, a mechanism capable of trace-level detection was crucial to detecting the rare GBM CSC-EVs from the complex environment in circulation. To break these barriers, we applied an ultrasensitive superlattice sensor, self-functionalized for surface-enhanced Raman scattering (SERS), to obtain holistic molecular profiling of GBM CSC-EVs with a marker-free approach. The superlattice sensor exhibited substantial SERS enhancement and ultralow limit of detection (LOD of attomolar 10-18 M concentration) essential for trace-level detection of invisible GBM CSC-EVs directly from patient serum (without isolation). We detected as low as 5 EVs in 5 μL of solution, achieving the lowest LOD compared to existing SERS-based studies. We have experimentally demonstrated the crucial role of the signals of GBM CSC-EVs in the precise detection of glioblastoma. This was evident from the unique molecular profiles of GBM CSC-EVs demonstrating significant variation compared to noncancer EVs and EVs of GBM cancer cells, thus adding more clarity to the current understanding of GBM CSC-EVs. Preliminary validation of our approach was undertaken with a small amount of peripheral blood (5 μL) derived from GBM patients with 100% sensitivity and 97% specificity. Identification of the signals of GBM CSC-EV in clinical sera specimens demonstrated that our technology could be used for accurate GBM detection. Our technology has the potential to improve GBM liquid biopsy, including real-time surveillance of GBM evolution in patients upon clinical validation. This demonstration of liquid biopsy with GBM CSC-EV provides an opportunity to introduce a paradigm potentially impacting the current landscape of GBM diagnosis.

Ultrasensitive MicroRNA Photoelectric Assay Based on a Mimosa-like CdS-NiS/Au Schottky Junction

Seeking and constructing superior photoactive materials have the potential to improve the performance of photoelectrochemical (PEC) biosensors. In this work, we proposed a novel mimosa-like ternary inorganic composite with a significantly enhanced light-harvesting ability and photogenerated carrier separation rate. This ternary photoactive material was obtained via electrodeposition of gold nanoparticles (Au) on the surface of transition metal sulfide composite of CdS and NiS (CdS-NiS/Au). The experimental results showed that the high initial photocurrent was acquired on CdS-NiS/Au (68-fold higher than that of individual CdS) with the synergistic effect of p-n heterojunction, Schottky junction, and the eminent optical properties of gold nanoparticles. Meanwhile, using silver nanoclusters prepared by link DNA protection as an effective quencher, integrating the duplex-specific nuclease-assisted rolling circle amplification strategy, a "Signal ON" PEC biosensor was fabricated for the detection of microRNA 21 (miRNA 21). With the release of the quencher, the recovered photocurrent is able to achieve determination of miRNA 21 within the range from 10 aM to 1 pM with a detection limit down to 4.6 aM (3σ). Importantly, this work not only provides a superb idea for designing ternary inorganic heteromaterials with exceptional photoactive ability but also allows the detection of other biomarkers by selecting appropriate recognition units.

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.

Construction of Ag/Ag2S/CdS Heterostructures through a Facile Two-Step Wet Chemical Process for Efficient Photocatalytic Hydrogen Production

We have demonstrated a two-step wet chemical approach for synthesizing ternary Ag/Ag₂S/CdS heterostructures for efficient photocatalytic hydrogen evolution. The CdS precursor concentrations and reaction temperatures are crucial in determining the efficiency of photocatalytic water splitting under visible light excitation. In addition, the effect of operational parameters (such as the pH value, sacrificial reagents, reusability, water bases, and light sources) on the photocatalytic hydrogen production of Ag/Ag₂S/CdS heterostructures was investigated. As a result, Ag/Ag₂S/CdS heterostructures exhibited a 3.1-fold enhancement in photocatalytic activities compared to bare CdS nanoparticles. Furthermore, the combination of Ag, Ag₂S, and CdS can significantly enhance light absorption and facilitate the separation and transport of photogenerated carriers through the surface plasma resonance (SPR) effect. Furthermore, the Ag/Ag₂S/CdS heterostructures in seawater exhibited a pH value approximately 2.09 times higher than in de-ionized water without an adjusted pH value under visible light excitation. The ternary Ag/Ag₂S/CdS heterostructures provide new potential for designing efficient and stable photocatalysts for photocatalytic hydrogen evolution.

Nanofluids for Direct-Absorption Solar Collectors-DASCs: A Review on Recent Progress and Future Perspectives

Owing to their superior optical and thermal properties over conventional fluids, nanofluids represent an innovative approach for use as working fluids in direct-absorption solar collectors for efficient solar-to-thermal energy conversion. The application of nanofluids in direct-absorption solar collectors demands high-performance solar thermal nanofluids that exhibit exceptional physical and chemical stability over long periods and under a variety of operating, fluid dynamics, and temperature conditions. In this review, we discuss recent developments in the field of nanofluids utilized in direct-absorption solar collectors in terms of their preparation techniques, optical behaviours, solar thermal energy conversion performance, as well as their physical and thermal stability, along with the experimental setups and calculation approaches used. We also highlight the challenges associated with the practical implementation of nanofluid-based direct-absorption solar collectors and offer suggestions and an outlook for the future.

Nanomaterials as multimodal photothermal agents (PTAs) against 'Superbugs'

Superbugs, also known as multidrug-resistant bacteria, have become a lethal and persistent threat due to their unresponsiveness toward conventional antibiotics. The main reason for this is that superbugs can rapidly mutate and restrict any foreign drug/molecule in their vicinity. Herein, nanomaterial-mediated therapies have set their path and shown burgeoning efficiency toward the ablation of superbugs. Notably, treatment modalities like photothermal therapy (PTT) have shown prominence in killing multidrug-resistant bacteria with their ability to generate local heat shock-mediated hyperthermia in such species. However, photothermal treatment has some serious limitations, such as high cost, complexity, and even toxicity to some extent. Hence, it is important to resolve such shortcomings of PTTs as they provide substantial tissue penetration. This is why multimodal PTTs have emerged and taken over this domain of research for the past few years. In this work, we have summarized and critically reviewed such exceptional works of recent times and provided a perspective to enhance their efficiencies. Profoundly, we discuss the design rationales of some novel photothermal agents (PTAs) and shed light on their mechanisms. Finally, challenges for PTT-derived multimodal therapy are presented, and capable synergistic bactericidal prospects are anticipated.

Exploiting the LSPR effect for an enhanced photocatalytic hydrogen evolution reaction

Incorporation of plasmonic metals is one of the most widely adopted strategies for improving the photocatalytic hydrogen evolution reaction (HER) activity of semiconductor photocatalysts. This article summarizes recent advances in the development of plasmonic metal-semiconductor photocatalysts and four localized surface plasmon resonance (LSPR) driven mechanisms by which plasmonic metal nanoparticles can contribute to enhancement of HER activity. In addition, principles for maximizing the contribution of these LSPR driven mechanisms are highlighted to provide insights for future design of plasmonic metal-semiconductor photocatalysts with enhanced HER activity.

Visible light-driven H2O2 synthesis over Au/C3N4: medium-sized Au nanoparticles exhibiting suitable built-in electric fields and inhibiting reverse H2O2 decomposition

Visible light-driven H₂O₂ production presents the unique merits of sustainability and environmental friendliness. The size of noble metal nanoparticles (NPs) determines their dispersion and electronic structure and greatly affects their photocatalytic activity. In this work, a series of sized Au NPs over C₃N₄ were modulated for H₂O₂ production. The results show that there is a volcanic trend in H₂O₂ with the decrease of Au particle size, and the highest H₂O₂ production rate of 1052 μmol g^-1 h^-1 is obtained from medium-sized Au particles (∼8.7 nm). The relationship between structure and catalytic performance is supported by experimental and theoretical methods. (1) First, medium-sized Au NPs promote photon absorption, and have a suitable built-in electric field at the heterojunction, which can be successfully tuned to achieve a more efficient h⁺-e^- spatial separation. (2) Second, medium-sized Au NPs enhance O₂ adsorption, and create selective 2e^- O₂ reduction reaction sites. (3) Particularly, medium-sized Au NPs promote the desorption of produced H₂O₂ and inhibit H₂O₂ decomposition, finally leading to the highest H₂O₂ selectivity. Excellent catalytic performance will be obtained by finely optimizing the particle size in a certain range. This work provides a new idea for preparing high efficiently photocatalysts for H₂O₂ production.

Size Effect in Hybrid TiO2:Au Nanostars for Photocatalytic Water Remediation Applications

TiO₂:Au-based photocatalysis represents a promising alternative to remove contaminants of emerging concern (CECs) from wastewater under sunlight irradiation. However, spherical Au nanoparticles, generally used to sensitize TiO₂, still limit the photocatalytic spectral band to the 520 nm region, neglecting a high part of sun radiation. Here, a ligand-free synthesis of TiO₂:Au nanostars is reported, substantially expanding the light absorption spectral region. TiO₂:Au nanostars with different Au component sizes and branching were generated and tested in the degradation of the antibiotic ciprofloxacin. Interestingly, nanoparticles with the smallest branching showed the highest photocatalytic degradation, 83% and 89% under UV and visible radiation, together with a threshold in photocatalytic activity in the red region. The applicability of these multicomponent nanoparticles was further explored with their incorporation into a porous matrix based on PVDF-HFP to open the way for a reusable energy cost-effective system in the photodegradation of polluted waters containing CECs.

Rapid Printing and Patterning of Tough, Self-Healable, and Recyclable Hydrogel Thin-Films toward Flexible Sensing Devices

Direct and rapid printing and surface patterning of hydrogel thin films are of great significance in the construction of advanced electronic devices, yet they are greatly underdeveloped due to the intrinsic contradiction between mechanical strength and self-healability as well as recyclability. Here, we present a universal and rapid slipping-directed route with a newly developed water-soluble star polymer hydrogel for direct and reproducible printing and patterning of freestanding functional thin films with precisely controlled thicknesses, components, and surface structures on a large scale. The resulting thin films combine the features of large transmittance (93%), tough mechanical strength (114 MPa), multiresponsive self-healability, recyclability, and remarkable multifunctionality. With the unique humidity-sensitive properties as motivation, diverse humidity-sensing devices including an actuating switch, a supercapacitive sensor, and a noncontact electronic skin are facilely constructed through the humidity-induced transverse, longitudinal, and patterning assembly techniques, respectively. The method presented here is universal and efficient in the fabrication and assembly of thin films with controlled configuration and functionality for advanced flexible electronics.

Triangular-shaped homologous heterostructure as photocatalytic H2S scavenger and macrophage modulator for rheumatoid arthritis therapy

Rheumatoid arthritis (RA) is a chronic arthropathy causing cartilage destruction, bone erosion, and even disability. Although some advances in RA treatment have been made based on inflammatory cytokine inhibition, long-term treatment and drug effect have been restrained by severe side effects. Herein, we developed a resveratrol (RSV)-loaded Ag/Ag₂S triangular-shaped homologous heterostructure with polyethylene glycol/folic acid (PEG/FA) modification (Ag/Ag₂S-PEG-FA/RSV NTs) to simultaneously suppress inflammatory cytokine over-expression through photocatalytic H₂S scavenging and macrophage polarization stimulation. On one hand, the over-expressed H₂S, which acted as a pro-inflammatory mediator to activate the MAPK/ICAM-1 pathway and exacerbate inflammation, was eliminated through photocatalysis. The homologous Ag and Ag₂S of the heterostructure enhanced electron separation and transfer by acting as a charge acceptor and electron generator, respectively, which restrained electron/hole recombination and promoted photocatalysis efficiency. Additionally, the intrinsic superoxide dismutase (SOD) and catalase (CAT) activity of Ag decomposed the reactive oxygen species (ROS) over-expressed in the RA microenvironment, which supplied O₂ for the photocatalytic H₂S scavenging progress. On the other hand, RSV, a natural product with anti-inflammatory activity, could be delivered to the inflammatory joint by the targeting effect of PEG-FA, thus inhibiting the IκB/NF-κB pro-inflammatory pathway to induce macrophage interconversion balance from M1 to M2. As expected, the Ag/Ag₂S-PEG-FA/RSV NTs exhibited H₂S scavenging capacity and modulated macrophage polarization to reduce the inflammatory cytokine level and halt RA progression in vitro and in vivo. Overall, this study revealed a therapeutic strategy with high efficacy, which opens broad prospects for RA treatment.

C-scheme electron transfer mechanism: An efficient ternary heterojunction photocatalyst carbon quantum dots/Bi/BiOBr with full ohmic contact

With a facile one-pot solvothermal method, an efficient ternary heterojunction photocatalyst carbon quantum dots (CQDs)/Bi/BiOBr is firstly prepared. Ethylene glycol (EG) is used as the solvent and carbon source for the first time. At 190 °C for 3 h, while BiOBr is synthesized, EG is employed to prepare CQDs through bottom-up method. CQDs are grafted by a large number of functional groups with reducibility, which reduce some neighboring BiO⁺ to metal Bi. By modifying the solvothermal temperature and time, CQDs and Bi are in-situ controllably deposited on the surface of BiOBr microspheres. Due to different Fermi levels and work functions, the interfaces of CQDs, BiOBr and Bi are connected through ohmic junctions with low contact impedance. The hot electrons from Bi with surface plasmon resonance (SPR) properties, and electrons in the CB of BiOBr flow to CQDs, forming a C-scheme electron transfer mechanism. O₂^- from CQDs and h⁺ in the VB of BiOBr respectively attack the sites with higher and lower electron density in methyl orange (MO) molecule, resulting in its photodegradation into small molecular products.

Combination of Plasmon-Mediated Photochemistry and Seed-Mediated Methods for Synthesis of Bicomponent Nanocrystals

Plasmon resonances of metal nanocrystals resulted from free electrons oscillating around nanocrystals, leading to a strong electromagnetic field around them. Because these oscillating electrons possess higher energy than the original ones, also known as hot electrons, these were widely used as photocatalysts for various reactions. Also, the strength and distribution of the electromagnetic field around the nanocrystals strongly depended on their morphology and excited irradiation, which led to the reaction environment around nanocrystals being controllable. Here, we integrated the seed-mediated and plasmon-mediated photochemistry methods for fabricating bimetallic and semiconductor-metal nanocrystals with controllable morphologies and compositions of the nanocrystals, resulting from the highly anisotropic reaction environment around the nanocrystals. The highly anisotropic reaction environment around the template nanocrystal was caused by the distribution of electromagnetic fields around it and its exposure area in the reaction solution. This new synthesis method should enable the fabrication of various multicomponent nanocrystals with desirable functions for potential applications, such as photocatalysts, chemical sensors, biosensors, biomedicines, etc.

In-situ Pt nanoparticles decorated BiOBr heterostructure for enhanced visible light-based photocatalytic activity: Synergistic effect

Advanced functional materials for photocatalytic hydrogen (H₂) generation using abundant solar energy are the core of new and renewable energy research. In this paper, we report the in-situ deposition of platinum quantum-sized particles (Pt QDs) on bismuth oxybromide (BBr) 3D marigold flowers with exposed (101)/(110) facets (i.e. BBr-Pt) hierarchies prepared by a simple solvo-thermal method acting as a surfactant/structure stabilizer in the presence of CTAB. Synthesized samples were characterized by a series of analytical techniques. Intimate contact as demonstrated by HRTEM, effect of Pt loading in 3D-BiOBr nanostructure on photocatalytic H₂ production and crystal violet (CV) dye degradation rate under white LED light irradiation was studied. This was greatly improved by loading Pt QDs on BBr, the latter showing the highest photocatalytic activity for BBr-2Pt nanostructure, due to the synergistic effect of quantum-sized Pt nanoparticles and exposed ((101) and (110) planes). The BBr-2Pt nanostructure photocatalysts showed highest H₂ generation of 320.69 μmol g^-1, which is 142 folds larger than bare BBr (2.26 μmol g^-1).

Enhanced Photocatalytic Oxidation of RhB and MB Using Plasmonic Performance of Ag Deposited on Bi2WO6

Visible-light-driven heterostructure Ag/Bi2WO6 nanocomposites were prepared using a hydrothermal method followed by the photodeposition of Ag on Bi2WO6. A photocatalyst with a different molar ratio of Ag to Bi2WO6 (1:1, 1:2 and 2:1) was prepared. The catalytic performance of Ag/Bi2WO6 towards the photocatalytic oxidation of rhodamine B (RhB) and methylene blue (MB) was explored. Interestingly, the Ag/Bi2WO6 (1:2) catalyst exhibited superior performance; it oxidized 83% of RhB to Rh-110 and degraded 68% of MB in 90 min. This might be due to the optimum amount of Ag nanoparticles, which supported the rapid generation and transfer of separated charges from Bi2WO6 to Ag through the Schottky barrier. An excess of Ag on Bi2WO6 (1:1 and 2:1) blocked the active sites of the reaction and did not produce the desired result. The introduction of Ag on Bi2WO6 improved the electrical conductivity of the composite and lowered the recombination rate of charge carriers. Our work provides a cost-effective route for constructing high-performance catalysts for the degradation of toxic dyes.

Plasmonic CuxS Nanocages for Enhanced Solar Photothermal Cell Warming

Highly efficient plasmonic photothermal nanomaterials are benefitial to the successful resuscitation of cells. Copper sulfide (Cu_xS) is a type of plasmonic solar photothermal semiconductor material that expands the light collecting range by altering its localized surface plasmonic resonance (LSPR) to the near- to mid-infrared (IR) spectral region. Particularly, nanocages (or nanoshells) have hybridized plasmon resonances as the result of superpositioned nanospheres and nanocavities, which extend their receiving range for the solar spectrum and increase light-to-heat conversion rate. In this work, for the first time, we applied colloidal hollow Cu_xS nanocages to revive cryopreserved HeLa cells via photothermal warming, which showed improved cell warming rate and cell viability after cell resuscitation. Moreover, we tested the photothermal performance of Cu_xS nanocages with concentrated light illumination, which exhibited extraordinary photothermal performance due to localized and enhanced illumination. We further quantified each band's contribution during the cell warming process via evaluating the warming rate of cryopreserved cell solution with illumination by monochromatic UV, visible, and NIR lasers. We studied the biosafety and toxicity of Cu_xS nanocages by analyzing the generated copper ion residue during cell warming and cell incubation, respectively. Our study shows that Cu_xS nanocages have huge potential for cell warming and are promising for vast range of applications, such as nanomedicine, life science, biology, energy saving, etc.

Research Progress of Plasmonic Nanostructure-Enhanced Photovoltaic Solar Cells

Enhancement of the electromagnetic properties of metallic nanostructures constitute an extensive research field related to plasmonics. The latter term is derived from plasmons, which are quanta corresponding to longitudinal waves that are propagating in matter by the collective motion of electrons. Plasmonics are increasingly finding wide application in sensing, microscopy, optical communications, biophotonics, and light trapping enhancement for solar energy conversion. Although the plasmonics field has relatively a short history of development, it has led to substantial advancement in enhancing the absorption of the solar spectrum and charge carrier separation efficiency. Recently, huge developments have been made in understanding the basic parameters and mechanisms governing the application of plasmonics, including the effects of nanoparticles’ size, arrangement, and geometry and how all these factors impact the dielectric field in the surrounding medium of the plasmons. This review article emphasizes recent developments, fundamentals, and fabrication techniques for plasmonic nanostructures while investigating their thermal effects and detailing light-trapping enhancement mechanisms. The mismatch effect of the front and back light grating for optimum light trapping is also discussed. Different arrangements of plasmonic nanostructures in photovoltaics for efficiency enhancement, plasmonics’ limitations, and modeling performance are also deeply explored.

Pd Nanosheet-Decorated 2D/2D g-C3N4/WO3·H2O S-Scheme Photocatalyst for High Selective Photoreduction of CO2 to CO

The development of the global economy in recent years, environmental problems, greenhouse effect, and so forth have been of concern for countries all over the world. The key for solving the greenhouse effect is the reduction of CO₂. With the development of photocatalytic reduction of CO₂, hybrid photocatalytic nanostructures composed of noble metals and plasmonic semiconductors are being widely studied. In this work, S-scheme photocatalysts with a g-C₃N₄/WO₃·H₂O/Pd heterostructure was constructed by introducing ultrathin Pd nanosheets into the optimized 2D/2D g-C₃N₄/WO₃·H₂O binary system. The S-scheme charge transfer generated by the matched band gap of g-C₃N₄ and WO₃·H₂O can effectually improve the electron transfer rate and the redox ability of photogenerated carriers. The introduction of Pd nanosheets can inject a large number of hot electrons into the semiconductor on the basis of the S-scheme heterojunction to participate in the reaction. The S-scheme electron transfer method is used to improve the utilization rate of thermionic electrons and achieve the effect of widening the near-infrared-light absorption area of the composite material. Moreover, the reaction was carried out in water without the addition of any sacrificial agent, which can better reflect the green environmental protection of the experiment. This investigation will promote the broad-spectrum application of new and environment-friendly thermoelectron-assisted S-scheme photocatalysts, and on this basis, the possible reaction mechanism is discussed.

Constructing Schottky junctions via Pd nanosheets on DUT-67 surfaces to accelerate charge transfer

The separation, transfer and recombination of charge often affect the rate of photocatalytic reduction of CO₂. Schottky junctions can promote the rapid separation of space charge. Therefore, in this paper, Pd nanosheets were grown on the surface of DUT-67 by a hydrothermal method, and a Schottky junction was constructed between DUT-67 and Pd. Under the action of the Schottky junction, the CO yield of 0.3-Pd/DUT-67 reached 12.15 μmol/g/h, which was 17 times higher than that of DUT-67. Efficient charge transfer was demonstrated in photochemical experiments. The large specific surface area and the increased light utilization rate also contributed to the increase in the CO₂ reduction efficiency. In addition, the mechanism of Pd/DUT-67 photocatalytic reduction of CO₂ was proposed.

Challenges and prospects in the selective photoreduction of CO2 to C1 and C2 products with nanostructured materials: a review

Solar fuel generation through CO₂ hydrogenation is the ultimate strategy to produce sustainable energy sources and alleviate global warming. The photocatalytic CO₂ conversion process resembles natural photosynthesis, which regulates the ecological systems of the earth. Currently, most of the work in this field has been focused on boosting efficiency rather than controlling the distribution of products. The structural architecture of the semiconductor photocatalyst, CO₂ photoreduction process, product analysis, and elucidating the CO₂ photoreduction mechanism are the key features of the photoreduction of CO₂ to generate C1 and C2 based hydrocarbon fuels. The selectivity of C1 and C2 products during the photocatalytic CO₂ reduction have been ameliorated by suitable photocatalyst design, co-catalyst, defect states, and the impacts of the surface polarisation state, etc. Monitoring product selectivity allows the establishment of an appropriate strategy to generate a more reduced state of a hydrocarbon, such as CH₄ or higher carbon (C2) products. This article concentrates on studies that demonstrate the production of C1 and C2 products during CO₂ photoreduction using H₂O or H₂ as an electron and proton source. Finally, it highlights unresolved difficulties in achieving high selectivity and photoconversion efficiency of CO₂ in C1 and C2 products over various nanostructured materials.

A Schottky-Barrier-Free Plasmonic Semiconductor Photocatalyst for Nitrogen Fixation in a "One-Stone-Two-Birds" Manner

Plasmonic photocatalysis has received much attention owing to attractive plasmonic enhancement effects in improving the solar-to-chemical conversion efficiency. However, the photocatalytic efficiencies have remained low mainly due to the short carrier lifetime caused by the rapid recombination of plasmon-generated hot charge carriers. Although plasmonic metal-semiconductor heterostructures can improve the separation of hot charge carriers, a large portion of the hot charge carriers are lost when they cross the Schottky barrier. Herein, a Schottky-barrier-free plasmonic semiconductor photocatalyst, MoO_{3- x} , which allows for efficient N₂ photofixation in a "one-stone-two-birds" manner, is demonstrated. The oxygen vacancies in MoO_{3- x} serve as the "stone." They "kill two birds" by functioning as the active sites for the chemisorption of N₂ molecules and inducing localized surface plasmon resonance for the generation of hot charge carriers. Benefiting from this unique strategy, plasmonic MoO_{3- x} exhibits a remarkable photoreactivity for NH₃ production up to the wavelength of 1064 nm with apparent quantum efficiencies over 1%, and a solar-to-ammonia conversion efficiency of 0.057% without any hole scavenger. This work shows the great potential of plasmonic semiconductors to be directly used for photocatalysis. The concept of the Schottky-barrier-free design will pave a new path for the rational design of efficient photocatalysts.

Plasmon-assisted facile selective gaseous isopropanol dehydrogenation over Ag nanocubes

The present research showed that the non-heating effect of plasmonic absorption caused a great increase in the acetone dehydrogenation over Ag nanocubes in high selectivity at low temperatures.

Magnetically Controllable Flowerlike, Polyhedral Ag-Cu-Co3O4 for Surface-Enhanced Raman Scattering

Syntheses of Cu-, Ag-, and Ag-Cu-Co₃O₄ nanomaterials are of interest for a wide range of applications including electrochemistry, thermal catalysis, energy storage, and electronics. However, Co₃O₄-based nanomaterials have not been explored for surface-enhanced Raman scattering (SERS). Here, we present Cu-, Ag-, and Ag-Cu-Co₃O₄ nanomaterials of a hierarchical flower shape comprising two separate phases: a pure Cu or Ag core and multiple Co₃O₄ branches, in which the optical properties of the core and the magnetic properties of the branches are integrated. In addition, a series of nonmagnetic Cu-dominant Cu-Co-O polyhedra without Co₃O₄ branches were derived from Cu-Co₃O₄. The polyhedron morphology can be controlled and transformed among cubes, cuboctahedra, and truncated octahedra by tuning the amounts of ligands and additives to vary the potential energy and growth rate of specific crystal facets. The flowerlike Cu-, Ag-, and Ag-Cu-Co₃O₄ were characterized for SERS enhancement, showing that Ag-Cu-Co₃O₄ does not enhance SERS from 4-mercaptobenzoic acid (4-MBA) but dramatically and selectively does so for adsorbed rhodamine 6G. Obviously, the synergy of Ag and Cu within the Co₃O₄ flower constraint promotes the SERS activity. This type of spinel with not only excellent SERS activity but also ferromagnetism could be of great potential in tandem SERS detection/magnetic separation and related applications.

Harvesting Hot Holes in Plasmon-Coupled Ultrathin Photoanodes for High-Performance Photoelectrochemical Water Splitting

The harvesting of hot carriers produced by plasmon decay to generate electricity or drive a chemical reaction enables the reduction of the thermalization losses associated with supra-band gap photons in semiconductor photoelectrochemical (PEC) cells. Through the broadband harvesting of light, hot-carrier PEC devices also produce a sensitizing effect in heterojunctions with wide-band gap metal oxide semiconductors possessing good photostability and catalytic activity but poor absorption of visible wavelength photons. There are several reports of hot electrons in Au injected over the Schottky barrier into crystalline TiO₂ and subsequently utilized to drive a chemical reaction but very few reports of hot hole harvesting. In this work, we demonstrate the efficient harvesting of hot holes in Au nanoparticles (Au NPs) covered with a thin layer of amorphous TiO₂ (a-TiO₂). Under AM1.5G 1 sun illumination, photoanodes consisting of a single layer of ∼50 nm diameter Au NPs coated with a 10 nm shell of a-TiO₂ (Au@a-TiO₂) generated 2.5 mA cm^-2 of photocurrent in 1 M KOH under 0.6 V external bias, rising to 3.7 mA cm^-2 in the presence of a hole scavenger (methanol). The quantum yield for hot-carrier-mediated photocurrent generation was estimated to be close to unity for high-energy photons (λ < 420 nm). Au@a-TiO₂ photoelectrodes produced a small positive photocurrent of 0.1 mA cm^-2 even at a bias of -0.6 V indicating extraction of hot holes even at a strong negative bias. These results together with density functional theory modeling and scanning Kelvin probe force microscope data indicate fast injection of hot holes from Au NPs into a-TiO₂ and light harvesting performed near-exclusively by Au NPs. For comparison, Au NPs coated with a 10 nm shell of Al₂O₃ (Au@Al₂O₃) generated 0.02 mA cm^-2 of photocurrent in 1 M KOH under 0.6 V external bias. These results underscore the critical role played by a-TiO₂ in the extraction of holes in Au@a-TiO₂ photoanodes, which is not replicated by an ordinary dielectric shell. It is also demonstrated here that an ultrathin photoanode (<100 nm in maximum thickness) can efficiently drive sunlight-driven water splitting.

A Review on Metal Ions Modified TiO2 for Photocatalytic Degradation of Organic Pollutants

TiO2 is a semiconductor material with high chemical stability and low toxicity. It is widely used in the fields of catalysis, sensing, hydrogen production, optics and optoelectronics. However, TiO2 photocatalyst is sensitive to ultraviolet (UV) light; this is why its photocatalytic activity and quantum efficiency are reduced. To enhance the photocatalytic efficiency in the visible light range as well as to increase the number of the active sites on the crystal surface or inhibit the recombination rate of photogenerated electron–hole pairs electrons, various metal ions were used to modify TiO2. This review paper comprehensively summarizes the latest progress on the modification of TiO2 photocatalyst by a variety of metal ions. Lastly, the future prospects of the modification of TiO2 as a photocatalyst are proposed.

Metal-facilitated Photocatalytic Nanohybrids: Rational Design and Promising Environmental Applications

As a promising technique to potentially address the energy crisis and environmental issues, photocatalysis has been reported widely to exhibit various outstanding behaviors in production of new fuels/chemicals and treatment of contaminants. The photocatalytic performance is extremely dependent on the used photocatalysts, so that the design and preparation of efficient photocatalysts are critically important for significantly improving the photocatalytic activity. Among various strategies, the hybridization of metal with semiconductors has recently been attracting more and more research interest owing to their expended spectral absorption, promoted transferring rate of charge carriers and Plasmon-enhanced effect. In this minireview, the metal-facilitated hybrid photocatalysts are overviewed comprehensively to first reveal unique functions of metals in improvement of photoactivity and summarize the emerging metal-involved hybrid systems. Subsequently, the synthetic methods towards hybrid photocatalysts are introduced and their practical applications are emphasized in environmental remediation including degradation of organic pollutants, conversion of harmful gases, treatment of heavy metal ions and sterilization of bacteria. At the end, the challenges for industrializing these hybrid photocatalysts are discussed carefully and future development is suggested rationally.

Gold Nanoparticles Photosensitization towards 3,4,9,10-Perylenetetracarboxylic Dianhydride Integrated with a Dual-Particle Three-Dimensional DNA Roller: A General "ON-OFF-ON" Photoelectric Plasmon-Enhanced Biosensor

A high initial signal for the sensitive detection of analytes is critical in photoelectrochemical (PEC) biosensing systems. As a semiconductor, 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) possesses an appropriate optical band gap of 2.5 eV and inherently intense and stable PEC response. When gold nanoparticles (Au NPs) are electrodeposited on the surface of PTCDA to form a Schottky junction (Au NPs/PTCDA), a surprising and satisfactory PEC performance is unfolded before our eyes. Considering the outstanding PEC behaviors of Au NPs/PTCDA and the great quenching effect of gold nanoclusters (Au NCs), the "ON-OFF-ON" PEC sensing platform has been developed for microRNA 1246 (miRNA 1246) detection combined with the cascaded quadratic amplification strategy of the polymerization/nicking reaction and dual-particle 3D DNA roller. The higher initial PEC signals of the system can be acquired by regulating the deposition time for 35 s (-0.2 V), which is derived from the synergetic effect of localized surface plasmon resonance of Au NPs and the formation of a Schottky junction. The dual-particle 3D DNA roller has been designed to guarantee wide walking space, remarkable operation performances, and inhibition of derailment. The proposed biosensor shows a dynamic range from 10 aM to 1 pM at a low detection limit of 3.1 aM and exhibits good analytical behaviors while analyzing miRNA 1246 in healthy human serum samples. This work not only expands the application of organic photoelectric materials in bioanalysis but also provides potential possibility of detecting other biomarkers by choosing appropriate target units.

Hot Electrons in TiO2-Noble Metal Nano-Heterojunctions: Fundamental Science and Applications in Photocatalysis

Plasmonic photocatalysis enables innovation by harnessing photonic energy across a broad swathe of the solar spectrum to drive chemical reactions. This review provides a comprehensive summary of the latest developments and issues for advanced research in plasmonic hot electron driven photocatalytic technologies focusing on TiO2-noble metal nanoparticle heterojunctions. In-depth discussions on fundamental hot electron phenomena in plasmonic photocatalysis is the focal point of this review. We summarize hot electron dynamics, elaborate on techniques to probe and measure said phenomena, and provide perspective on potential applications-photocatalytic degradation of organic pollutants, CO2 photoreduction, and photoelectrochemical water splitting-that benefit from this technology. A contentious and hitherto unexplained phenomenon is the wavelength dependence of plasmonic photocatalysis. Many published reports on noble metal-metal oxide nanostructures show action spectra where quantum yields closely follow the absorption corresponding to higher energy interband transitions, while an equal number also show quantum efficiencies that follow the optical response corresponding to the localized surface plasmon resonance (LSPR). We have provided a working hypothesis for the first time to reconcile these contradictory results and explain why photocatalytic action in certain plasmonic systems is mediated by interband transitions and in others by hot electrons produced by the decay of particle plasmons.

Solvothermal Crystallization of Ag/AgxO-AgCl Composites: Effect of Different Chloride Sources/Shape-Tailoring Agents

In the present work, AgCl microcrystals were obtained by solvothermal crystallization to investigate the effect of H+, Na+, K+, and different shape-tailoring agents (non-ionic: polyvinylpyrrolidone vs. anionic: sodium dodecyl sulfate) on the textural and photocatalytic properties of the samples. The crystallization process resulted in secondary products, such as AgxO or Ag, AgClO3, AgClO4, which were further transformed during the photocatalytic tests. The most efficient photocatalyst (assessed for methyl orange degradation) was synthesized using HCl, as a chloride source and polyvinylpyrrolidone, as a shape-tailoring agent. Therefore, the ability of polyvinylpyrrolidone to enhance the photocatalytic activity was also investigated, and it was found that the addition of 0.6 g polyvinylpyrrolidone resulted in the most efficient photocatalyst. Moreover, AgxO, being a charge separator, could play a critical role in the photocatalytic process, while reversibly transforming to Ag back and forth.

Fundamentals and applications of photo-thermal catalysis

Photo-thermal catalysis has recently emerged as an alternative route to drive chemical reactions using light as an energy source.

Selectivity control of organic chemical synthesis over plasmonic metal-based photocatalysts

The factors, issues, and design of plasmonic metal-based photocatalysts for selective photosynthesis of organic chemicals have been discussed.

Shining light on transition metal sulfides: New choices as highly efficient antibacterial agents

Globally, millions of people die of microbial infection-related diseases every year. The more terrible situation is that due to the overuse of antibiotics, especially in developing countries, people are struggling to fight with the bacteria variation. The emergence of super-bacteria will be an intractable environmental and health hazard in the future unless novel bactericidal weapons are mounted. Consequently, it is critical to develop viable antibacterial approaches to sustain the prosperous development of human society. Recent researches indicate that transition metal sulfides (TMSs) represent prominent bactericidal application potential owing to the meritorious antibacterial performance, acceptable biocompatibility, high solar energy utilization efficiency, and excellent photo-to-thermal conversion characteristics, and thus, a comprehensive review on the recent advances in this area would be beneficial for the future development. In this review article, we start with the antibacterial mechanisms of TMSs to provide a preliminary understanding. Thereafter, the state-of-the-art research progresses on the strategies for TMSs materials engineering so as to promote their antibacterial properties are systematically surveyed and summarized, followed by a summary of the practical application scenarios of TMSs-based antibacterial platforms. Finally, based on the thorough survey and analysis, we emphasize the challenges and future development trends in this area.

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.

A versatile strategy for controlled assembly of plasmonic metal/semiconductor hemispherical nano-heterostructure arrays

Recent advances in manipulating plasmonic properties of metal/semiconductor heterostructures have opened up new avenues for basic research and applications. Herein, we present a versatile strategy for the assembly of arrays of plasmonic metal/semiconductor hemispherical nano-heterostructures (MSHNs) with control over spacing and size of the metal/semiconductor heterostructure array, which can facilitate a wide range of scientific studies and applications. The strategy combines nanosphere lithography for generating the metal core array with solution-based chemical methods for the semiconductor shell that are widely available and kinetically controllable. Periodic arrays of Au/Cu₂O and Ag/Cu₂O heterostructures are synthesized to demonstrate the approach and highlight the versatility and importance of the tunability of plasmonic properties. The morphology, structure, optical properties, and elemental compositions of the heterostructures were analyzed. This strategy can be important for understanding and manipulating fundamental nanoscale solid-state physical and chemical properties, as well as assembling heterostructures with desirable structure and functionality for applications.

Plasmonic Photocatalysts for Sunlight-Driven Reduction of CO2 : Details, Developments, and Perspectives

Plasmonic photocatalysis is among the most efficient processes for the photoreduction of CO₂ into valuable fuels. The formation of localized surface plasmon resonance (LSPR), energy transfer, and surface reaction are the significant steps in this process. LSPR plays an essential role in the performance of plasmonic photocatalysts as it promotes an excellent, light absorption over a broad wavelength range while simultaneously facilitating an efficient energy transfer to semiconductors. The LSPR transfers energy to a semiconductor through various mechanisms, which have both advantages and disadvantages. This work points out four critical features for plasmonic photocatalyst design, that is, plasmonic materials, size, shape of plasmonic nanoparticles (PNPs), and the contact between PNPs and semiconductor. Various developed plasmonic photocatalysts, as well as their photocatalytic performance in CO₂ photoreduction, are reviewed and discussed. Finally, perspectives of advanced architectures and structural engineering for plasmonic photocatalyst design are put forward with high expectations to achieve an efficient CO₂ photoreduction shortly.

Efficient Solar Evaporation by [Ni(Phen)3 ][V14 O34 Cl]Cl Hybrid Semiconductor Confined in Mesoporous Glass

Efficient utilization of solar energy for water evaporation is an advanced and environmentally friendly technology to address the crisis of global drinking water shortages. This study concerns an efficient solar vapor generator comprised of a light-absorbing and photothermal hybrid compound [Ni(Phen)₃ ][V₁₄ O₃₄ Cl]Cl (NiV₁₄ ) confined in mesoporous and hydrophilic glass (meso-glass). The generator is floated in water by supporting it on a domestic melamine-formaldehyde (MF) foam to ensure evaporation at the water-air interface. The porous structures and poor thermal conductivities of the meso-glass and MF foam contribute to enabling a consistent water supply, strong solar thermal localization, and less heat dissipation and convection. Associated with the strong photothermal role of NiV₁₄ , these synergistic effects lead to a water evaporation rate of 14.38 kg m^-2  h^-1 with total water evaporation efficiency of 111.4% under 6 suns and a daily solar water purification yield of 42.00 L m^-2 under 1 sun irradiation. This solar evaporation system shows great promise for high-efficiency water purification application.

Enhanced OER Performances of Au@NiCo2S4 Core-Shell Heterostructure

Transition metal sulfides have attracted a lot of attention as potential oxygen evolution reaction (OER) catalysts. Bimetallic sulfide possesses superior physicochemical properties due to the synergistic effect between bimetallic cations. By introducing a metal-semiconductor interface, the physicochemical properties of transition metal sulfide can be further improved. Using the solvothermal method, Au@NiCo₂S₄ core-shell heterostructure nanoparticles (NPs) and bare NiCo₂S₄ NPs were prepared. The measurement of the OER catalytic performance showed that the catalytic activity of Au@NiCo₂S₄ core-shell heterostructure was enhanced compared to bare NiCo₂S₄ NPs. At the current density of 10 mA cm⁻², the overpotential of Au@NiCo₂S₄ (299 mV) is lower than that of bare NiCo₂S₄ (312 mV). The Tafel slope of Au@NiCo₂S₄ (44.5 mV dec⁻¹) was reduced compared to that of bare NiCo₂S₄ (49.1 mV dec⁻¹), indicating its faster reaction kinetics. Detailed analysis of its electronic structure, chemical state, and electrochemical impedance indicates that the enhanced OER catalytic performances of bare Au@NiCo₂S₄ core-shell NPs were a result of its increased proportion of high-valance Ni/Co cations, and its increased electronic conductivity. This work provides a feasible method to improve OER catalytic performance by constructing a metal-semiconductor core-shell heterostructure.

Controlled Synthesis of Au Nanocrystals-Metal Selenide Hybrid Nanostructures toward Plasmon-Enhanced Photoelectrochemical Energy Conversion

A simple method for the controllable synthesis of Au nanocrystals–metal selenide hybrid nanostructures via amino acid guiding strategy is proposed. The results show that the symmetric overgrowth mode of PbSe shells on Au nanorods can be precisely manipulated by only adjusting the initial concentration of Pb²⁺. The shape of Au–PbSe hybrids can evolve from dumbbell-like to yolk-shell. Interestingly, the plasmonic absorption enhancement could be tuned by the symmetry of these hybrid nanostructures. This provides an effective pathway for maneuvering plasmon-induced energy transfer in metal–semiconductor hybrids. In addition, the photoactivities of Au–PbSe nanorods sensitized TiO₂ electrodes have been further evaluated. Owing to the synergism between effective plasmonic enhancement effect and efficient interfacial charge transfer in these hybrid nanostructures, the Au–PbSe yolk-shell nanorods exhibit an outstanding photocurrent activity. Their photocurrent density is 4.38 times larger than that of Au–PbSe dumbbell-like nanorods under light irradiation at λ > 600 nm. As a versatile method, the proposed strategy can also be employed to synthesize other metal–selenide hybrid nanostructures (such as Au–CdSe, Au–Bi₂Se₃ and Au–CuSe).