Plasmonic Hybrid Nanostructures in Photocatalysis: Structures, Mechanisms, and Applications

(Sun)Light is an abundantly available sustainable source of energy that has been used in catalyzing chemical reactions for several decades now. In particular, studies related to the interaction of light with plasmonic nanostructures have been receiving increased attention. These structures display the unique property of localized surface plasmon resonance, which converts light of a specific wavelength range into hot charge carriers, along with strong local electromagnetic fields, and/or heat, which may all enhance the reaction efficiency in their own way. These unique properties of plasmonic nanoparticles can be conveniently tuned by varying the metal type, size, shape, and dielectric environment, thus prompting a research focus on rationally designed plasmonic hybrid nanostructures. In this review, the term "hybrid" implies nanomaterials that consist of multiple plasmonic or non-plasmonic materials, forming complex configurations in the geometry and/or at the atomic level. We discuss the synthetic techniques and evolution of such hybrid plasmonic nanostructures giving rise to a wide variety of material and geometric configurations. Bimetallic alloys, which result in a new set of opto-physical parameters, are compared with core-shell configurations. For the latter, the use of metal, semiconductor, and polymer shells is reviewed. Also, more complex structures such as Janus and antenna reactor composites are discussed. This review further summarizes the studies exploiting plasmonic hybrids to elucidate the plasmonic-photocatalytic mechanism. Finally, we review the implementation of these plasmonic hybrids in different photocatalytic application domains such as H₂ generation, CO₂ reduction, water purification, air purification, and disinfection.

Construction of CdSe-AuPd quantum dot 0D/0D hybrid photocatalysts: charge transfer dynamic study with electrochemical analysis for improved photocatalytic activity

The integration of semiconductor quantum dots and noble metal nanoparticles can efficiently couple numerous effects corresponding to the individual domains of the hybrid system for a variety of applications. Herein, we establish a direct correlation between the electronic band structure and optical band gap of monometallic and bimetallic alloy nanoparticle decorated CdSe quantum dots, which in turn regulate the charge shuttling dynamics in a quantum dot hybrid (QDH) system. Directly coupled Au, Pd, AuPd, and CdSe QDHs were prepared via a simple fabrication technique. The photoluminescence intensity of the QDHs was quenched compared to that of CdSe quantum dots with a maximumally diminished CdSe-AuPd system. Broadening of the absorbance peak along with a blue shift for QDHs confirm the interaction of the energy levels of the QDs and metal domains. AuPd decorated CdSe QDs demonstrate enhanced photocatalytic activity compared to their monometallic counterparts, which has made them interesting catalysts reported for the first time. Lifetime decay measurements, which isolated the individual charge-transfer steps, showed that a maximum amount of photoexcitons can be separated by bimetallic alloy decoration compared to monometallic ones. Cyclic voltammetry results offer insight into the change in the conduction band edge energy position for both monometallic and bimetallic incorporating semiconductor hybrid systems. Our findings reveal that photoexcited semiconductor quantum dots undergo charge equilibration when the QDs are in contact with metallic domains, influencing the shifting of the conduction band energy level of the hybrid to a more negative potential, and this is a maximum for the CdSe-AuPd hybrid, resulting in the best photocatalytic activity. Shuttling of electrons around the conduction band of CdSe and the Fermi level of the metallic domains is the main deciding factor for an efficient photocatalyst hybrid system.

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.

Ultrafine AuPd nanoparticles supported on amine functionalized monochlorotriazinyl β-cyclodextrin as highly active catalysts for hydrogen evolution from formic acid dehydrogenation

Au_0.3Pd_0.7/A-M-β-CD exhibits remarkable catalytic activity for hydrogen evolution from formic acid, which is attributed to strong metal–support interaction.

Gold catalyzed Heck-coupling of arenediazonium o-benzenedisulfonimides

An efficient gold catalyzed Heck coupling of arenediazonium o-benzenedisulfonimides is proposed. An o-benzenedisulfonimide anion enables a radical pathway that does not require the presence of photocatalysts or external oxidants.

Ultrasonic assisted synthesis of palladium-nickel/iron oxide core-shell nanoalloys as effective catalyst for Suzuki-Miyaura and p-nitrophenol reduction reactions

In this study, ultrasonic assisted synthesis of Pd-Ni/Fe₃O₄ core-shell nanoalloys is reported. Unique reaction condition was prepared by ultrasonic irradiation, releasing the stored energy in the collapsed bubbles and heats the bubble contents that leads to Pd(II) and Ni(II) reduction. Co-precipitation method was applied for the synthesis of Fe₃O₄ nanoparticles (NPs). Immobilized solution was produced by sonicating the aqueous mixture of Fe₃O₄ and mercaptosuccinic acid to obtain Pd-Ni alloys on Fe₃O₄ magnetic NP cores. The catalytic activity of the synthesized Pd-Ni/Fe₃O₄ core-shells was investigated in the Suzuki-Miyaura CC coupling reaction and 4-nitrophenol reduction, which exhibited a high catalytic activity in both reactions. These magnetic NPs can be separated from the reaction mixture by external magnetic field. This strategy is simple, economical and promising for industrial applications.

Activated nanostructured bimetallic catalysts for C–C coupling reactions: recent progress

This minireview highlights the recent progress made in the last decade towards the development of activated bimetallic alloy nanoparticle catalysts for C–C coupling reactions, including asymmetric C–C bond coupling reactions.

Access to highly active Ni–Pd bimetallic nanoparticle catalysts for C–C coupling reactions

A facile access to highly active (with enhanced TONs/TOFs) and durable bimetallic Ni–Pd nanoparticle catalysts for C–C coupling reactions was achieved by tuning Ni to Pd atomic ratio in the Ni–Pd nanoparticle catalyst and therefore the electronic charge transfer from Ni to Pd.

Fabrication of magnetic bimetallic Fe3O4@Au–Pd hybrid nanoparticles with recyclable and efficient catalytic properties

View of the preparation process and evaluation of the catalytic activity of Fe₃O₄@Pd and Fe₃O₄@Au–Pd NPs.

Gold nanoflowers with tunable sheet-like petals: facile synthesis, SERS performances and cell imaging

Gold nanoflowers with tunable sheet-like petals were controllably synthesized, and their SERS performances as well as their application in cell imaging were studied.

Using Scanning-Probe Block Copolymer Lithography and Electron Microscopy To Track Shape Evolution in Multimetallic Nanoclusters

Here we describe a general method for synthesizing multimetallic core-shell nanoclusters on surfaces. By patterning seeds at predesignated locations using scanning-probe block copolymer lithography, we can track shape evolution in nanoclusters and elucidate their growth pathways using electron microscopy. The growth of core-shell nanostructures on surface-bound seeds is a highly anisotropic process and often results in multimetallic anisotropic nanostructures. The shell grows at specific edge and corner sites of the patterned seeds and propagates predominately from the top hemisphere of the seeds.

Palladium-Based Nanomaterials: A Platform to Produce Reactive Oxygen Species for Catalyzing Oxidation Reactions

Oxidation reactions by molecular oxygen (O2 ) over palladium (Pd)-based nanomaterials are a series of processes crucial to the synthesis of fine chemicals. In the past decades, investigations of related catalytic materials have mainly been focused on the synthesis of Pd-based nanomaterials from the angle of tailoring their surface structures, compositions and supporting materials, in efforts to improve their activities in organic reactions. From the perspective of rational materials design, it is imperative to address the fundamental issues associated with catalyst performance, one of which should be oxygen activation by Pd-based nanomaterials. Here, the fundamentals that account for the transformation from O2 to reactive oxygen species over Pd, with a focus on singlet O2 and its analogue, are introduced. Methods for detecting and differentiating species are also presented to facilitate future fundamental research. Key factors for tuning the oxygen activation efficiencies of catalytic materials are then outlined, and recent developments in Pd-catalyzed oxygen-related organic reactions are summarized in alignment with each key factor. To close, we discuss the challenges and opportunities for photocatalysis research at this unique intersection as well as the potential impact on other research fields.

Oxidation of Aliphatic Alcohols by Using Precious Metals Supported on Hydrotalcite under Solvent- and Base-Free Conditions

Precious metal nanoparticles supported on magnesium-aluminum hydrotalcite (HT), TiO2 , and MgO were prepared by sol immobilization and assessed for the catalytic oxidation of octanol, which is a relatively unreactive aliphatic alcohol, with molecular oxygen as the oxidant under solvent- and base-free conditions. Compared with the TiO2 - and MgO-supported catalysts, platinum HT gave the highest activity and selectivity towards the aldehyde. The turnover number achieved for the platinum HT catalyst was >3700 after 180 min under mild reaction conditions. Moreover, the results for the oxidation of different substrates indicate that a specific interaction of octanal with the platinum HT catalyst could lead to deactivation of the catalyst.

Enhanced photocatalytic efficiency of AuPd nanoalloy decorated ZnO-reduced graphene oxide nanocomposites

Possible mechanism involved for the degradation of R6G dye upon UV irradiation by using ZnO–RGO–M (M = Au, Pd, AuPd) nanocomposite.

Segregation in bimetallic nanoparticles

Theoretical models and experimental results for segregation in bimetallic nanoparticles are discussed and compared in this perspective.

Au@Pd core–shell nanoparticles-decorated reduced graphene oxide: a highly sensitive and selective platform for electrochemical detection of hydrazine

An Au_core–Pd_shell-decorated reduced graphene oxide nanocomposite is successfully employed for the electrochemical detection of low-level hydrazine in an aqueous solution.

Facile synthesis of highly active PdAu nanowire networks as self-supported electrocatalyst for ethanol electrooxidation

In recent years, direct ethanol fuel cells (DEFCs) are attracting increasing attention owing to their wide applications. However, a significant challenge in the development of DEFC technology is the urgent need for highly active anode catalysts for the ethanol oxidation reaction. In this work, a facile and reproducible method for the high-yield synthesis of PdAu nanowire networks is demonstrated. The whole synthetic process is very simple, just mixing Na2PdCl4, HAuCl4, and KBr in an aqueous solution and using polyvinylpyrrolidone as a protective reagent while sodium borohydride as a reductant. The whole synthetic process can be simply performed at room temperature and completed in 30 min, which can greatly simplify the synthetic process and lower the preparation cost. Electrochemical catalytic measurement results prove that the as-prepared catalysts exhibit dramatically enhanced electrocatalytic activity for ethanol electrooxidation in alkaline solution. The facile synthetic process and excellent catalytic performance of the as-prepared catalysts demonstrate that they can be used as a promising catalyst for DEFCs.