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Vibrational Spectra of Thiolate-Protected Gold Nanocluster with Infrared Reflection Absorption Spectroscopy: Size- and Temperature-Dependent Ordering Behavior of Organic Monolayer
摘要： Vibrational spectra of thiolate-protected gold nanoclusters, prepared in a monolayer manner using the Langmuir?Blodgett method, were measured by means of infrared re?ection absorption spectroscopy (IRAS). A transferred monolayer of gold nanoclusters ligated by dodecanethiolate or 2-phenylethane-1-thiolate onto a single-crystal gold (Au) surface of Au(111) exhibits worthy IRAS spectra that reveal temperature-dependent behaviors from 100 to 340 K as well as comprehensive peak assignments based on density functional theory calculations: the conformation change in ligands between all trans and gauche defect forms with temperature. In addition to the temperature dependence, the cluster size dependence of alkyl and phenyl moieties is discussed, compared with the IRAS spectra of the corresponding self-assembled monolayers (SAMs) on Au(111). Ligands spreading three-dimensionally from the Au core determine the coordination structure of the ligated Au nanoclusters.
关键词： self-assembled monolayers,density functional theory calculations,Langmuir?Blodgett method,thiolate-protected gold nanoclusters,Vibrational spectra,temperature-dependent behaviors,infrared re?ection absorption spectroscopy
更新于2025-09-12 10:27:22
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Confinement-Induced Giant Spin-Orbit-Coupled Magnetic Moment of Co Nanoclusters in TiO2 Films
摘要： High magnetization materials are in great demand for the fabrication of advanced multifunctional magnetic devices. Notwithstanding this demand, the development of new materials with these attributes has been relatively slow. In this work, we propose a new strategy to achieve high magnetic moments above room temperature. Our materials engineering approach invoked the embedding of magnetic nanoclusters in an oxide matrix. By precisely controlling pulsed laser deposition parameters, Co nanoclusters are formed in a 5 at.% Co-TiO2 film. The presence of these nanoclusters was confirmed using transmission electron microscopy, energy dispersive X-ray spectroscopy and X-ray absorption fine structure. The film exhibits a very high saturation magnetization of 99 emu/cm3. Detailed studies using X-ray magnetic circular dichroism confirm that Co has an enhanced magnetic moment of 3.5 μB/atom, whilst the Ti and O also contribute to the magnetic moments. First principles calculations supported our hypothesis that the metallic Co nanoclusters surrounded by a TiO2 matrix can exhibit both large spin and orbital moments. Moreover, a quantum confinement effect results in a high Curie temperature for the embedded Co nanoclusters. These findings reveal that 1-2 nm nanoclusters that are quantum confined can exhibit very large magnetic moments above room temperature, representing a promising advance for the design of new high magnetization materials.
关键词： TiO2,Quantum,Ferromagnetism,Enhanced magnetic moment,Confinement effect,Nanoclusters
更新于2025-09-11 14:15:04
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Ultra-fast annealing manipulated spinodal nano-decomposition in Mn-implanted Ge
摘要： In the present work, millisecond-range flash lamp annealing is used to recrystallize Mn-implanted Ge. Through systematic investigations of structural and magnetic properties, we find that the flash lamp annealing produces a phase mixture consisting of spinodally decomposed Mn-rich ferromagnetic clusters within a paramagnetic-like matrix with randomly distributed Mn atoms. Increasing the annealing energy density from 46, via 50, to 56 J cm?2 causes the segregation of Mn atoms into clusters, as proven by transmission electron microscopy analysis and quantitatively confirmed by magnetization measurements. According to x-ray absorption spectroscopy, the dilute Mn ions within Ge are in d5 electronic configuration. This Mn-doped Ge shows paramagnetism, as evidenced by the unsaturated magnetic-field-dependent x-ray magnetic circular dichroism signal. Our study reveals how spinodal decomposition occurs and influences the formation of ferromagnetic Mn-rich Ge–Mn nanoclusters.
关键词： flash lamp annealing,ion implantation,spinodal decomposition,Ge–Mn nanoclusters
更新于2025-09-11 14:15:04
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Au Nanocluster Growth on Graphene Supported on Ni(111)
摘要： Low energy alkali ion scattering is used to investigate the deposition of Au onto a single layer of graphene grown onto Ni(111) by chemical vapor deposition. The yield of 3.0 keV Na+ singly scattered from Au as a function of coverage indicates that it grows in a Volmer-Weber mode forming nanoclusters that increase in size with the amount of deposition. The neutralization probability of the scattered Na+ is high for the smallest clusters and decreases as they increase in size. This is presumably caused by the cluster edge atoms being positively charged combined with the fact that the ratio of edge to center atoms decreases with size, which is similar to the behavior of Au nanoclusters on oxide substrates. In addition, oxygen is intercalated under the graphene film to decouple it from the substrate, but no changes in the growth mode or neutralization probability are observed.
关键词： Au nanoclusters,Ni(111),graphene,Volmer-Weber growth mode,charge transfer,low energy alkali ion scattering
更新于2025-09-11 14:15:04
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Gold Nanoclusters Enhanced Photocatalytic Property of Bismuth Oxychloride
摘要： This paper have synthesized bismuth oxychloride (BiOCl) nano-plate (BNS) by hydrothermal method and fabricated BiOCl-gold nanoclusters (Au NCs) heterostucture nanomaterials (BANC) through electrostatic interaction. X-ray diffraction, transmission electron microscope and X-ray photoelectron spectroscopy characterizations indicate Au NCs successfully modified on BNS. The small energy gap makes Au NCs suitable for absorbing sunlight, while staggered energy bands between Au NCs and BiOCl could effectively separate electrons and holes, resulting in enhanced photocatlytic performance. Actually, under simulated sunlight irradiation, BANC could completely degrade rhodamine B within 30 minutes. the photostability test showed that the structure of BNAC did not changed after irradiation.
关键词： Electron transfer,Gold nanoclusters,Bismuth Oxychloride,Photocatalysis,Dye Degradation
更新于2025-09-10 09:29:36
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Electronic and Geometric Structure, Optical Properties, and Excited State Behavior in Atomically Precise Thiolate-Stabilized Noble Metal Nanoclusters
摘要： Ligand-protected noble metal nanoclusters are of interest for their potential applications in areas such as bioimaging, catalysis, photocatalysis, and solar energy harvesting. These nanoclusters can be prepared with atomic precision, which means that the properties of these nanoclusters can vary significantly depending on the exact stoichiometry and geometric structure of the system. This leads to important questions such as: What are the general principles that underlie the physical properties of these nanoclusters? Do these principles hold for all systems? What properties can be “tuned” by varying the size and composition of the system? In this Account, we describe research that has been performed to analyze the electronic structure, linear optical absorption, and excited state dynamics of thiolate-stabilized noble metal nanoclusters. We focus primarily on two systems, Au25(SR)18? and Au38(SR)24, as models for understanding the principles underlying the electronic structure, optical properties, luminescence, and transient absorption in these systems. In these nanoclusters, the orbitals near the HOMO?LUMO gap primarily arise from atomic 6sp orbitals located on Au atoms in the gold core. The resulting nanocluster orbitals are delocalized throughout the core of these systems. Below the core-based orbitals lies a set of orbitals that are primarily composed of Au 5d and S 3p atomic orbitals from atoms located around the exterior gold?thiolate oligomer motifs. This set of orbitals has a higher density of states than the set arising from the core 6sp orbitals. Optical absorption peaks in the near-infrared and visible regions of the absorption spectrum arise from excitations between core orbitals (lowest energy peaks) and excitations from oligomer-based orbitals to core-based orbitals (higher energy peaks). Nanoclusters with different stoichiometries have varying gaps between the core orbitals themselves as well as between the band of oligomer-based orbitals and the band of core orbitals. These gaps can slow down nonradiative electron transfer between excited states that have different character; the excited state electron and hole dynamics depend on these gaps. Nanoclusters with different stoichiometries also exhibit different luminescence properties. Depending on factors that may include the symmetry of the system and the rigidity of the core, the nanocluster can undergo large or small nuclear changes upon photoexcitation, which affects the observed Stokes shift in these systems. This dependence on stoichiometry and composition suggests that the size and the corresponding geometry of the nanocluster is an important variable that can be used to tune the properties of interest. How does doping affect these principles? Replacement of gold atoms with silver atoms changes the energetics of the sp and d atomic orbitals that make up the nanocluster orbitals. Silver atoms have higher energy sp orbitals, and the resulting nanocluster orbitals are shifted in energy as well. This affects the HOMO?LUMO gap, the oscillator strength for transitions, the spacings between the different bands of orbitals, and, as a consequence, the Stokes shift and excited state dynamics of these systems. This suggests that nanocluster doping is one way to control and tune properties for use in potential applications.
关键词： ligand-protected noble metal nanoclusters,doping,electronic structure,optical properties,transient absorption,luminescence,atomic precision
更新于2025-09-10 09:29:36
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A Single Fluorophore Ratiometric Nanosensor Based on Dual-Emission DNA-templated Silver Nanoclusters for Ultrasensitive and Selective Pb2+ Detection
摘要： Lead ion (Pb2+) is known as a major non-degradable environmental pollutant and is quite harmful to human health. In our investigation, a novel ratiometric fluorescent nanosensor with DNA-AgNCs as single fluorophore has been successfully constructed for ultrasensitive and specific detection of Pb2+. The single-strand DNA templated silver nanoclusters present green emission, which can be converted into red emission after approaching a specific DNA segment by forming duplex with its complementary DNA strands (ds-DNA-AgNCs). The ds-DNA-AgNCs contains rA cleavage site of Pb2+-dependent DNAzyme configuration. In the presence of Pb2+, the specific DNA segment would be released from the ds-DNA-AgNCs, resulting in discoloration of DNA-AgNCs from red to green. Since Pb2+ can successively cleave the rA site, the signal change from red to green emission is amplified. Thus, benefiting from the Pb2+-dependent DNAzyme and the charming properties of DNA-AgNCs, the proposed platform exhibits a good linear relationship from 0.001 nM to 10 nM with a detection limit of 1.0 pM for Pb2+ determination, which is lower than most of the reported Pb2+ biosensors. Moreover, this sensitive ratiometric fluorescent probe exhibits excellent selectivity toward Pb2+ detection in real samples, such as lake water, tap water, and human serum samples, illustrating the huge potential applications for complicated samples in the future.
关键词： Pb2+ detection,Ratiometric fluorescent nanosensor,DNA-templated silver nanoclusters,Single fluorophore
更新于2025-09-10 09:29:36
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Silver doping induced luminescence enhancement and red shift of gold nanoclusters with aggregation-induced emission
摘要： Deep understanding on the luminescence property of aggregation-induced emission (AIE) featured metal nanoclusters (NCs) is highly desired. This paper reports an systematic study on enhancing the luminescence of AIE-featured Au NCs, which is achieved by Ag doping to engineer the size/structure and aggregation states of the Au(I)-thiolate motifs in the NC shell. Moreover, by prolonging reaction time, the luminescence of the as-synthesized AuAg NCs could be further tailored from orange to red, which is also due to the variation of the Au(I)-thiolate motifs of NCs. This study can facilitate the better understanding of this AIE-featured luminescent probe and the design of other synthetic routes for this rising family of functional materials.
关键词： bimetallic,aggregation-induced emission,luminescence enhancement,nanoclusters,red shift
更新于2025-09-10 09:29:36
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Determination of the activity of T4 polynucleotide kinase phosphatase by exploiting the sequence-dependent fluorescence of DNA-templated copper nanoclusters
摘要： A fluorometric method is described for the determination of the activity of the enzyme T4 polynucleotide kinase phosphatase (T4 PNKP). A short 3′-terminus phosphorylated DNA strand is hybridized with a long DNA strand to produce a partially double-stranded DNA (dsDNA) substrate. On addition of T4 PNKP, the substrate is dephosphorylated to generate the long dsDNA, and then the long dsDNA acted as a template for synthesizing copper nanoclusters (CuNCs). The dsDNA-templated CuNCs display fluorescence with excitation/emission peak wavelengths of 340/570 nm. The fluorescence is DNA sequence-dependent. A DNA substrate was designed to enhance fluorescence and to reduce the background in order to improve the sensitivity of the assay. The assay has an analytical range that extends from 0.07 U mL?1 to 15 U mL?1 and a detection limit of 0.06 U mL?1.
关键词： Near-zero background,Label-free,Copper nanoclusters,T4 polynucleotide kinase phosphatase activity,Fluorescent biosensing
更新于2025-09-10 09:29:36
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Metal-Enhanced Fluorescence of Gold Nanoclusters as a Sensing Platform for Multi-component Detection
摘要： Metal-enhanced fluorescence (MEF) has been applied to construct biosensing systems in the recent decades owing to its favorable optical properties. Herein, silver nanoparticles (AgNPs) are used to enhance fluorescence of gold nanoclusters (AuNCs), by fabricating a core-shell composite nanostructure Ag@SiO2-AuNCs consisting of a silver core, a silica shell and an outer conjugated layer of AuNCs. The core-shell MEF-capable nanoparticles possess water dispersibility, high stability and good biocompatibility. The interaction between AuNCs on the surface of the outer silica shell and the silver core, significantly improves the excitation efficiency, and thus enhances the fluorescence emission, photostability and quantum yield of the AuNCs. The composite nanoparticle Ag@SiO2-AuNCs provides a fluorescence enhancement of up to 3.21-fold when the separation distance (the thickness of the silica shell) is about 10 nm. Finally, the composite nanostructures have further been applied to develop a sensing platform for multi-component detection based on the MEF capability and the OFF-ON-OFF switching nature of the fluorescence signal, and the detection limits for Cu2+, inorganic pyrophosphate (PPi) and pyrophosphatase (PPase) are 39 nM, 78.7 nM and 0.976 mU, respectively. This platform has been applied to detect Cu2+, PPi and PPase with satisfactory results in living cells.
关键词： Metal-enhanced fluorescence (MEF),Fluorescence sensor,Core-shell composite nanostructure,Gold nanoclusters (AuNCs)
更新于2025-09-10 09:29:36