Controlled preparation and application of glutathione capped gold and platinum alloy nanoclusters with high peroxidase-like activity

In the present study,we have prepared glutathione capped gold and platinum alloy nanoclusters(AuPtNCs)in a controlled way by employing the hydrothermal method and optimized through adjusting the ratio of raw materials,reaction temperature,and time.Compared with the corresponding monometallic gold and platinum nanoclusters,the alloy nanoclusters’catalytic activity is improved dramatically in the oxidation of 3,3,5,5-tetramethylbenzidine(TMB)in the presence of H_(2)O_(2).And the maximum velocity is calculated to be 106×10^(-8)M·s^(-1) for TMB as substrate,being much better than that of other reported metallic nanoclusters and nanoparticles.Further study shows that the high catalytic activity mainly attributes to the synergistic effect of gold and platinum.Besides,they have been applied to determine H_(2)O_(2)in the presence of TMB,which shows high sensitivity with a limit of detection(LOD)at 100 n M.The proposed method has been used to determine H_(2)O_(2)in milk and contact lens solutions,which shows very good recovery and exhibits high practical application potential.Therefore,the present study provides a new type of alloy nanoclusters with high peroxidase-like activity,which will inspire more research interests on doping and alloying with Pt to improve the catalytic activity of metal nanoclusters.

Nicotinamide adenine dinucleotide(NAD^(+))reduction enabled by an atomically precise Au-Ag alloy nanocluster

The redox property of the ultrasmall coinage nanoclusters(with several to tens of Au/Ag atoms)has elucidated the electrontransfer capacity of nanoclusters,has been successfully utilized in a variety of redox conversions(such as from CO_(2)to CO).Nevertheless,their biological applications are mainly restricted by the scarcity of atomically precise,water-soluble metal nanoclusters,the limited application(mainly on the decomposition of H_(2)O_(2)in these days).Herein,mercaptosuccinic acid(MSA)protected ultrasmall alloy AuAg nanoclusters were prepared,the main product was determined[Au_(3)Ag_(5)(MSA)_(3)]−by electrospray ionization mass spectrometry(ESI-MS).The clusters can not only mediate the decomposition of H_(2)O_(2)to generate hydroxyl radicals,but is also able to mediate the reduction of nicotinamide adenine dinucleotide(NAD)to its reduced form of NADH.This is the first time that the atomically precise metal nanoclusters were used to mediate the coenzyme reduction.The preliminary mechanistic insights imply the reaction to be driven by the hydrogen bonding between the carboxylic groups(on the surface of MSA)and the amino N–H bonds(on NAD).In this context,the presence of the carboxylic groups,the sub-nanometer size regime(~1 nm),the synergistic effect of the Au-Ag clusters are pre-requisite to the NAD reduction.

Single-electron charging and ultrafast dynamics of bimetallic Au_(144−x)Agx(PET)_(60) nanoclusters

Alloying is an important strategy in tailoring the functionality of materials.In metal nanoclusters(NCs),the introduction of a heterometal leads to alloy nanoclusters that often outperform the homometal ones in terms of the physical and chemical properties.In this work,a series of four M_(144)(PET)60 alloy NCs(where,M=Au/Ag,PET=–SCH_(2)CH_(2)Ph)are synthesized and characterized.The silver doping into the homogold template(Au_(144))leads to more prominent optical absorption features in the steady-state spectrum in the visible range.Femtosecond transient absorption spectroscopy reveals the effect of Ag doping on the electronic relaxation dynamics compared to Au_(144)and the pump fluence independent dynamics.Electrochemical results reflect a narrowing of HOMO–LUMO gap(E_(g))induced by Ag doping.A temperature dependence of the single-electron charging is also observed for the series of alloy NCs,in which the E_(g)values of the alloy NCs enlarge as the temperature decreases,which is characteristic of semiconducting behavior.

Layer-by-layer alloying of NIR-Ⅱ emissive M50(Au/Ag/Cu)superatomic nanocluster

The intermetallic synergy plays a critical role in exploring the chemical-physical properties of metal nanoclusters.However,the controlled doping or layer-by-layer alloying of atom-precise metal nanoclusters(NCs)has long been a challenging pursuit.In this work,two novel alloy nanoclusters[PPh_(4)]_(4)[Ag_(32)Cu_(18)(PFBT)_(36)]((AgCu)_(50))and[PPh_(4)]_(4)[Au_(12)Ag_(20)Cu_(18)(PFBT)_(36)](Au_(12)(AgCu)_(38)),where PFBT is pentafluorobenzenethiolate,with shell-by-shell configuration of M_(12)@Ag_(20)@Cu_(18)(PFBT)_(36)(M=Ag/Au)were synthesized by a facile one-pot co-reduction method.Notably,a fingerprint library of[Ag_(50)−xCux(PFBT)_(36)]^(4−)(x=0 to 50)from Ag_(50)to Cu_(50)has been successfully established as revealed by electrospray ionization mass spectrometry.Single-crystal X-ray diffraction analysis of trimetallic Au_(12)(AgCu)_(38)confirmed the layer-by-layer alloying under reducing conditions.What is more,(AgCu)_(50)and Au12(AgCu)_(38)both show broad photoluminescence(PL)peak in the second near-infrared(NIR-II)window,and the Au doping in the innermost shell considerably enhances the photoluminescence intensity.This work not only offers an insight in the process of metal cluster alloying but also provides a platform to study the doping-directed PL properties in the multimetallic cluster system.

Aggregation of Surface Structure Induced Photoluminescence Enhancement in Atomically Precise Nanoclusters

Although intermolecular aggregation-induced emission(AIE)has been extensively studied in nanocluster science,it remains challenging to activate AIE via intracluster aggregation(i.e.,the aggregation at the single-molecular level).Here,an intracluster AIE system based on the Pt_(1)Ag_(24)(SR)18 nanocluster has been established.Specifically,triggered by the addition of free thiol ligands,the Ag_(2)(SR)_(3)surface motif structures of Pt_(1)Ag_(24)(SR)18 are aggregated to nanocluster poles.

One-step rapid synthesis,crystal structure and 3.3 microseconds long excited-state lifetime of Pd1Ag28 nanocluster

Doping foreign atom(s)in metal nanoclusters is an effective strategy to engineer the properties and functionalities of metal nanoclusters.However,until now,to dope Pd atom into Ag nanoclusters remains a huge challenge.Here we develop a one-step rapid method to synthesize the Pd-doped Ag nanocluster with high yield.The prepared Pd1Ag28 nanocluster was characterized by mass spectroscopy,X-ray photoelectron spectroscopy,X-ray crystallography,fluorescence spectroscopy,ultraviolet-visible absorption spectroscopy and transient absorption spectroscopy.The nanocluster exhibits a perfect face-centered cubic(FCC)kernel structure with a tetrahedron-like shell.Of note,Pd1Ag28 nanocluster had an unexpectedly long excited-state lifetime of 3.3 microseconds,which is the longest excited-state lifetime for Ag-based nanoclusters S0 far.Meanwhile,the excellent near-infrared luminescence indicated the nanocluster has the potential in fluorescent bio-imaging.Besides,it was revealed that Pd1Ag28 nanocluster could be transformed into Au1Ag28 nanocluster via ion exchange reaction of AuPPhzCl with Pd1Ag28 nanocluster.This work provides an efficient synthetic protocol of alloy nanoclusters and wil contribute to study the effect of foreign atom on the properties of metal nanoclusters.

Synthesis and structure of Au_(19)Ag_4(S-Adm)_(15) nanocluster:Polymorphs and optical properties

Polymorphism is a common phenomenon in nature.Here,we report one-pot wet chemical method to synthesize two polymorphs of Au_(19)Ag_(4)(S-Adm)_(15) nanocluster protected by 1-adamantanethiol(HSAdm),which adopt P-1 and P2_(1)/c space group respectively.The crystal structures of two polymorphs were determined by X-ray crystallography.Compared to the previously reported Au_(19)Ag_(4)(S-Adm)_(15)nanocluster adopting P2_(1)/n space group,polymorphs of Au_(19)Ag_(4)(S-Adm)_(15) with P-1 and P2_(1)/c space group show the different optical properties.Moreove r,Au_(19)Ag_(4)(S-Adm)_(15) with P-1 space group exhibits good thermal stability.Meanwhile,we investigated the effect of solvent and molar ratio of metal precursors on the polymorphs.This work provides an insight to polymorphs of metal nanoclusters.