Structure–performance relationship of Au nanoclusters in electrocatalysis:Metal core and ligand structure

Remarkable progress has characterized the field of electrocatalysis in recent decades,driven in part by an enhanced comprehension of catalyst structures and mechanisms at the nanoscale.Atomically precise metal nanoclusters,serving as exemplary models,significantly expand the range of accessible structures through diverse cores and ligands,creating an exceptional platform for the investigation of catalytic reactions.Notably,ligand‐protected Au nanoclusters(NCs)with precisely defined core numbers offer a distinct advantage in elucidating the correlation between their specific structures and the reaction mechanisms in electrocatalysis.The strategic modulation of the fine microstructures of Au NCs presents crucial opportunities for tailoring their electrocatalytic performance across various reactions.This review delves into the profound structural effects of Au NC cores and ligands in electrocatalysis,elucidating their underlying mechanisms.A detailed exploration of the fundamentals of Au NCs,considering core and ligand structures,follows.Subsequently,the interaction between the core and ligand structures of Au NCs and their impact on electrocatalytic performance in diverse reactions are examined.Concluding the discourse,challenges and personal prospects are presented to guide the rational design of efficient electrocatalysts and advance electrocatalytic reactions.

Au nanoclusters anchored on TiO_(2) nanosheets for high-efficiency electroreduction of nitrate to ammonia

Electrocatalytic nitrate reduction reaction(NO_(3)RR)offers a unique rationale for green NH_(3) synthesis,yet the lack of high-efficiency NO_(3)RR catalysts remains a great challenge.In this work,we show that Au nanoclusters anchored on TiO_(2) nanosheets can efficiently catalyze the conversion of NO_(3)RR-to-NH_(3) under ambient conditions,achieving a maximal Faradic efficiency of 91%,a peak yield rate of 1923μg·h^(-1)·mgcat.-1,and high durability over 10 consecutive cycles,all of which are comparable to the recently reported metrics(including transition metal and noble metal-based catalysts)and exceed those of pristine TiO_(2).Moreover,a galvanic Zn-nitrate battery using the catalyst as the cathode was proposed,which shows a power density of 3.62 mW·cm^(-2) and a yield rate of 452μg·h^(-1)·mgcat.-1.Theoretical simulations further indicate that the atomically dispersed Au clusters can promote the adsorption and activation of NO_(3)-species,and reduce the NO_(3)RR-to-NH_(3) barrier,thus leading to an accelerated cathodic reaction.This work highlights the importance of metal clusters for the NH_(3) electrosynthesis and nitrate removal.

Phosphorylation of NIR-II emitting Au nanoclusters for targeted bone imaging and improved rheumatoid arthritis therapy

Designing a theranostic probe for noninvasive bone imaging and bone disease therapy is both challenging and desirable.Herein,an ultrasmall Au nanocluster(NC,<2 nm)-based theranostic probe is developed to achieve highly temporospatial in vivo bone-targeted photoluminescence(PL)imaging in the second near-infrared window(NIR-Ⅱ)and enhanced rheumatoid arthritis(RA)therapy.The key design of the probe involves the surface phosphorylation of atomically precise NIR-Ⅱemitting Au_(44)NCs.This phosphorylation enhances the bone-targeting ability of the probe due to the highly concentrated phosphate groups,allowing the probe to realize in vivo bone-targeted NIR-ⅡPL imaging.Moreover,benefiting from the enhanced bone-targeting ability,ultrasmall hydrodynamic diameter,and excellent anti-inflammation and immunomodulatory effects,the probe not only demonstrates superior therapeutic efficacy for RA rats,effectively restoring the destructed cartilage to nearly normal but also exhibits good renal clearance and benign biocompatibility.These favorable attributes cannot be achieved by commercial methotrexate used for RA treatment.This study presents a new design paradigm for metal NC-based theranostic probes,offering the potential for high-resolution bone-targeted PL imaging and improved RA therapy.

Au-nanocluster-loaded human serum albumin nanoparticles with enhanced cellular uptake for fluorescent imaging

Protein-directed fluorescent Au nanoclusters have been widely studied owing to their potential applications in sensing,imaging,and drug and gene delivery.However,the use of nanoclusters in drug delivery is limited by low cellular uptake.In this study,human serum albumin-directed Au nanoclusters served as building blocks to obtain protein nanoparticles by desolvation.The nanoparticles had a decent quantum yield(QY),high colloidal stability and low cytotoxicity,and they could be readily conjugated with biological molecules.The cellular uptake of the Au nanoclusters and nanocluster-loaded protein nanoparticles were studied by confocal fluorescence microscopy.Agglomeration of the protein-directed Au nanoclusters into 50–150-nm nanoparticles dramatically increased the cellular uptake.

Metal–ligand interfaces for well-defined gold nanoclusters

Ligand engineering for well-defined gold nanoclusters(Au NCs) is getting more extensive attention. Organizing the Au-ligand interfaces on gold NCs can achieve the structural and functional control. This review focuses on the Au-ligand interfaces including gold-phosphorus(Au-P), gold-sulfur(Au-S), gold-selenium(Au-Se), gold-carbon(Au-C), and gold-nitrogen(Au-N), derived from the bonding between Au atoms and the different ligands(e.g., organic phosphine, thiolate, selenolate, alkynyl,n-heterocyclic carbene and nitrogenous ligands). The formation mechanism of Au-ligand interfaces is well discussed. In addition, the effects of Au-ligand interfaces on the stability, optical property, and catalysis are also presented. We hope the advances in this research area can boost the development of Au NC sciences.

Structure regulated catalytic performance of gold nanocluster-MOF nanocomposites

Atomically precise gold(Au)nanoclusters(NCs)as visible light photosensitizers supported on the substrate for photoredox catalysis have attracted considerable attentions.However,eficient control of their photocatalytic activity and long-term stability is still challenging.Herein,we report a coordination-assisted self-assembly strategy in combination with electrostatic interaction to sandwich Au2:(Capt)18(abbreviated as AU25,Capt=captopril)NCs between an inner core and an outer shell made of UiO-66,denoted as UiO-66@Au25@UiO-66.Notably,the sandwich-like nanocomposite displays significantly enhanced catalytic activity along with an excellent stability when used in the selective photocatalytic aerobic oxidation of sulfide to sulfoxide.As comparison,AU25 NCs simply located at the outer surface or insider matrix of UiO-66(short as Au2/UiO-66 and AU2s@UiO-66)show poor stability and low conversion,respectively.This structure regulated difference in the catalytic performances of three nanocomposites is assigned to the varied distribution of active sites(Au NCs)in metal-organic frameworks(MOFs).This work offers the opportunity for application of nanoclusters in catalysis,energy conversion and even biology.

Dual-emissive nanohybrid nanoclusters for sensitive ions of carbon dots and gold determination of mercuric

The present work reports a sensitive and selective fluorescent sensor for the detection of mercury ion, Hg（II）, by hybridizing carbon nanodots （C-dots） and gold nanoclusters （Au NCs） through intrinsic interactions of the two components. The C-dots serve as the reference signal and the Au NCs as the reporter. This method employs the specific high affinity metallophilic Hg2^-Au＋ interactions which can greatly quench the red fluorescence of Au NCs, while the blue fluorescence of C-dots is stable against Hg（II）, leading to distinct ratiometric fluorescence changes when exposed to Hg（II）. A limit of detection of 28 nM for Hg（II） in aqueous solution was estimated. Thus we applied the sensor for the detection of Hg（II） in real water samples including tap water, lake water and mineral water samples with good results. We further demonstrated that a visual chemical sensor could be manufactured by immobilizing the nanohybrid probe on a cellulose acetate circular filter paper. The paper-based sensor immediately showed a distinct fluorescence color evolution from pink to blue after exposure to a drop of the Hg（II） solution

The reactive activities of natural amino acids: key principles of peptide-templated Au cluster synthesis

Coating of gold nanoclusters with peptides is an important targeting method in biomedical applications.However, their synthetic method highly influences their targeting ability. Current methods often use harsh reagents and organic solvents to control morphology, which are not preferred for biomedical applications. Recently, several peptides with specific amino acid sequences have successfully been used to reduce Au ions and synthesize biocompatible peptide-covered gold particles in situ.However, the molecular mechanism of peptide-assisted nanocluster formation is yet unclear. Thus, reactive abilities of different amino acids should be studied to improve design of peptides with predetermined amino acid content and consequently, synthesize gold nanoclusters with improved performance. In this theoretical study, we have approximated the reactive abilities of 20 natural amino acids in their neutral state using density functional theory calculations, such as Fukui indices and HOMO/LUMO composition analysis. We have found that the top reducing agents are tryptophan, histidine, and tyrosine, and thestrongest binding can be expected from methionine and cysteine. Further study of the exact reactive sites in these high reactive amino acids provided the deep insight for the peptide design route for the targeted gold nanocluster formation.