Publications by authors named "Rongchao Jin"

193 Publications

Hydrogen Evolution Electrocatalyst Design: Turning Inert Gold into Active Catalyst by Atomically Precise Nanochemistry.

J Am Chem Soc 2021 Jul 16;143(29):11102-11108. Epub 2021 Jul 16.

Department of Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States.

Electrocatalytic hydrogen evolution reaction (HER) holds promise in the renewable clean energy scheme. Crystalline Au and Ag are, however, poor in catalyzing HER, and the ligands on colloidal nanoparticles are generally another disadvantage. Herein, we report a thiolate (SR)-protected AuAg(SR) nanocluster with low coverage of ligands and a core composed of three icosahedral () units for catalyzing HER efficiently. This trimeric structure, together with the monomeric Au(SR) and dimeric Au(SR), constitutes a unique series, providing an opportunity for revealing the correlation between the catalytic properties and the catalyst's structure. The AuAg(SR) surprisingly exhibits high catalytic activity at lower overpotentials for HER due to its low ligand-to-metal ratio, low-coordinated Au atoms and unfilled superatomic orbitals. The current density of AuAg(SR) at -0.3 V vs RHE is 3.8 and 5.1 times that of Au(SR) and Au(SR), respectively. Density functional theory (DFT) calculations reveal lower hydrogen binding energy and higher electron affinity of AuAg(SR) for an energetically feasible HER pathway. Our findings provide a new strategy for constructing highly active catalysts from inert metals by pursuing atomically precise nanoclusters and controlling their geometrical and electronic structures.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/jacs.1c04606DOI Listing
July 2021

Double-helical assembly of heterodimeric nanoclusters into supercrystals.

Nature 2021 Jun 16;594(7863):380-384. Epub 2021 Jun 16.

Department of Chemistry, Carnegie Mellon University, Pittsburgh, PA, USA.

DNA has long been used as a template for the construction of helical assemblies of inorganic nanoparticles. For example, gold nanoparticles decorated with DNA (or with peptides) can create helical assemblies. But without such biological ligands, helices are difficult to achieve and their mechanism of formation is challenging to understand. Atomically precise nanoclusters that are protected by ligands such as thiolate have demonstrated hierarchical structural complexity in their assembly at the interparticle and intraparticle levels, similar to biomolecules and their assemblies. Furthermore, carrier dynamics can be controlled by engineering the structure of the nanoclusters. But these nanoclusters usually have isotropic structures and often assemble into commonly found supercrystals. Here we report the synthesis of homodimeric and heterodimeric gold nanoclusters and their self-assembly into superstructures. While the homodimeric nanoclusters form layer-by-layer superstructures, the heterodimeric nanoclusters self-assemble into double- and quadruple-helical superstructures. These complex arrangements are the result of two different motif pairs, one pair per monomer, where each motif bonds with its paired motif on a neighbouring heterodimer. This motif pairing is reminiscent of the paired interactions of nucleobases in DNA helices. Meanwhile, the surrounding ligands on the clusters show doubly or triply paired steric interactions. The helical assembly is driven by van der Waals interactions through particle rotation and conformational matching. Furthermore, the heterodimeric clusters have a carrier lifetime that is roughly 65 times longer than that of the homodimeric clusters. Our findings suggest new approaches for increasing complexity in the structural design and engineering of precision in supercrystals.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/s41586-021-03564-6DOI Listing
June 2021

Total Structure of Bimetallic Core-Shell [Au Cd (SR) ] Nanocluster and Its Implications.

Angew Chem Int Ed Engl 2021 Jun 14. Epub 2021 Jun 14.

College of Materials Science and Engineering, Qingdao University of Science and Technology, Qingdao, 266042, P. R. China.

Bimetallic core-shell nanostructures hold great promise in elucidating the bimetallic synergism. However, it remains a challenge to construct atomically precise core-shell with high-valence active metals on the gold surface. In this work, we report the total structure of a [Au Cd (SR) ] core-shell nanocluster and multiple implications. Single crystal X-ray diffraction (SCXRD) reveals that the structure possesses a two-shelled Au @Au core and a closed cadmium shell of Cd , and the core-shell structure is then protected by 52 thiolate (-SR) ligands. The composition of the nanocluster is further confirmed by electrospray ionization mass spectrometry (ESI-MS). A catalytic test for styrene oxidation and a comparison with relevant nanoclusters reveal the surface effect on the catalytic activity and selectivity.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/anie.202106804DOI Listing
June 2021

Isomerization-induced enhancement of luminescence in Au(SR) nanoclusters.

Chem Sci 2020 Jul 17;11(31):8176-8183. Epub 2020 Jul 17.

Department of Chemistry, Carnegie Mellon University Pennsylvania 15213 USA

Understanding the origin and structural basis of the photoluminescence (PL) phenomenon in thiolate-protected metal nanoclusters is of paramount importance for both fundamental science and practical applications. It remains a major challenge to correlate the PL properties with the atomic-level structure due to the complex interplay of the metal core ( the inner kernel) and the exterior shell ( surface Au(i)-thiolate staple motifs). Decoupling these two intertwined structural factors is critical in order to understand the PL origin. Herein, we utilize two Au(SR) nanoclusters with different -R groups, which possess the same core but different shell structures and thus provide an ideal system for the PL study. We discover that the Au(CHT) (CHT: cyclohexanethiolate) nanocluster exhibits a more than 15-fold higher PL quantum yield than the Au(TBBT) nanocluster (TBBT: -butylbenzenethiolate). Such an enhancement is found to originate from the different structural arrangement of the staple motifs in the shell, which modifies the electron relaxation dynamics in the inner core to different extents for the two nanoclusters. The emergence of a long PL lifetime component in the more emissive Au(CHT) nanocluster reveals that its PL is enhanced by suppressing the nonradiative pathway. The presence of long, interlocked staple motifs is further identified as a key structural parameter that favors the luminescence. Overall, this work offers structural insights into the PL origin in Au(SR) nanoclusters and provides some guidelines for designing luminescent metal nanoclusters for sensing and optoelectronic applications.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1039/d0sc01270jDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8163317PMC
July 2020

Single and bi-excitonic characteristics of ligand-modified silicon nanoparticles as demonstrated single particle photon statistics and plasmonic effects.

Nanoscale 2021 Jun 8. Epub 2021 Jun 8.

Department of Chemistry, Carnegie Mellon University, Pittsburgh, PA 15213, USA.

Silicon nanoparticles (Si NPs) are of great interest to researchers due to their fluorescence properties, low toxicity, and the low cost of the Si precursor. Recent studies have shown that Si NPs surface-modified with secondary aryl amine ligands emit light at wavelengths ranging from cyan to yellow and with quantum yields of up to 90%. The predominant emitting state in these species has been assigned to a charge-transfer (CT) transition from the ligand to the Si particle as the emission wavelength is determined by the dipolar properties of the ligand rather than the size of the Si core. This contribution focuses on the single-molecule emission properties of Si NPs functionalized with a 1,2,3,4-tetrahydrocarbazole-4-one ligand (Te-On) which have a peak emission wavelength of 550 nm and a quantum yield of 90%. In single-particle dispersed emission spectra, a weak long-wavelength sideband is seen in addition to the dominant yellow emission derived from the CT state. The photon statistical behavior of single Si NPs in the red emission region is consistent with that of a state having collective or bi-excitonic character. In contrast, the yellow emission exhibits predominantly CT character. Deposition of the sample onto a thin gold film causes the CT emission to be quenched whereas that attributed to a bi-exciton state of the Si core is enhanced. These results provide new insights into the mechanism of single-molecule intensity fluctuation in these surface-modified silicon nanoparticles that will benefit proposed applications in biological labeling and as single-photon sources.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1039/d1nr00108fDOI Listing
June 2021

Programmable Metal Nanoclusters with Atomic Precision.

Adv Mater 2021 May 13:e2006591. Epub 2021 May 13.

Department of Chemistry, Carnegie Mellon University, Pittsburgh, PA, 15213, USA.

With the recent establishment of atomically precise nanochemistry, capabilities toward programmable control over the nanoparticle size and structure are being developed. Advances in the synthesis of atomically precise nanoclusters (NCs, 1-3 nm) have been made in recent years, and more importantly, their total structures (core plus ligands) have been mapped out by X-ray crystallography. These ultrasmall Au nanoparticles exhibit strong quantum-confinement effect, manifested in their optical absorption properties. With the advantage of atomic precision, gold-thiolate nanoclusters (Au (SR) ) are revealed to contain an inner kernel, Au-S interface (motifs), and surface ligand (-R) shell. Programming the atomic packing into various crystallographic structures of the metal kernel can be achieved, which plays a significant role in determining the optical properties and the energy gap (E ) of NCs. When the size increases, a general trend is observed for NCs with fcc or decahedral kernels, whereas those NCs with icosahedral kernels deviate from the general trend by showing comparably smaller E . Comparisons are also made to further demonstrate the more decisive role of the kernel structure over surface motifs based on isomeric Au NCs and NC series with evolving kernel or motif structures. Finally, future perspectives are discussed.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/adma.202006591DOI Listing
May 2021

Observation of Core Phonon in Electron-Phonon Coupling in Au Nanoclusters.

J Phys Chem Lett 2021 Feb 9;12(6):1690-1695. Epub 2021 Feb 9.

Department of Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States.

Temperature-dependent optical properties are of paramount importance for fundamentally understanding the electron-phonon interactions and phonon modes in atomically precise nanocluster materials. In this work, low-temperature optical absorption spectra of the icosahedral [Au(SR)] nanocluster are measured from room temperature down to liquid helium temperature by adopting a thin-film-based technique. The thin-film measurement is further compared with results from the previous solution-based method. Interestingly, the previously missing core phonon is revealed by a quantitative analysis of the film data through peak deconvolution and fitting of the temperature trend with a theoretical model. The two lowest-energy absorption peaks (at 1.6 and 1.8 eV) of Au are determined to couple with the staple-shell phonon (average energy ∼350 cm) in the solution state, but in the solid state these electronic transitions couple with the core phonon (average energy ∼180 cm). The suppression of the staple-shell phonon in the solid state is attributed to the intracluster and cluster-matrix interactions.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acs.jpclett.1c00050DOI Listing
February 2021

Ultrabright [email protected] nanoclusters: 71.3% phosphorescence quantum yield in non-degassed solution at room temperature.

Sci Adv 2021 Jan 6;7(2). Epub 2021 Jan 6.

Department of Chemistry, Carnegie Mellon University, Pittsburgh, PA 15213, USA.

The photoluminescence of metal nanoclusters is typically low, and phosphorescence emission is rare due to ultrafast free-electron dynamics and quenching by phonons. Here, we report an electronic engineering approach to achieving very high phosphorescence (quantum yield 71.3%) from a [[email protected](SPh Bu)(PPh(CHCN))] nanocluster (abbreviated ) in non-degassed solution at room temperature. The structure of has a single-Au-atom kernel, which is encapsulated by a rigid Cu(I) complex cage. This core-shell structure leads to highly efficient singlet-to-triplet intersystem crossing and suppression of nonradiative energy loss. Unlike the phosphorescent organic materials and organometallic complexes-which require de-aerated conditions due to severe quenching by air (i.e., O)-the phosphorescence from is much less sensitive to air, which is important for lighting and biomedical applications.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1126/sciadv.abd2091DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7787487PMC
January 2021

The role of ligands in atomically precise nanocluster-catalyzed CO electrochemical reduction.

Nanoscale 2021 Feb;13(4):2333-2337

Department of Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA.

Ligand effects are of major interest in catalytic reactions owing to their potential critical role in determining the reaction activity and selectivity. Herein, we report ligand effects in the CO2 electrochemical reduction reaction at the atomic level with three unique Au25 nanoclusters comprising the same kernel but different protecting ligands (-XR, where X = S or Se, and R represents the carbon tail). It is observed that a change in the carbon tail shows no obvious impact on the catalytic selectivity and activity, but the anchoring atom (X = S or Se) strongly affects the electrocatalytic selectivity. Specifically, the S site acts as the active site and sustains CO selectivity, while the Se site shows a higher tendency of hydrogen evolution. Density functional theory (DFT) calculations reveal that the energy penalty associated with the *COOH formation is lower on the S site by 0.26 eV compared to that on the Se site. Additionally, the formation energy of the product (*CO) is lower on the sulfur-based Au nanocluster by 0.43 eV. We attribute these energetic differences to the higher electron density on the sulfur sites of the Au nanocluster, resulting in a modified bonding character of the reaction intermediates that reduce the energetic penalty for the *COOH and *CO formation. Overall, this work demonstrates that S/Se atoms at the metal-ligand interface can play an important role in determining the overall electrocatalytic performance of Au nanoclusters.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1039/d0nr07832hDOI Listing
February 2021

Boosting CO Electrochemical Reduction with Atomically Precise Surface Modification on Gold Nanoclusters.

Angew Chem Int Ed Engl 2021 Mar 12;60(12):6351-6356. Epub 2021 Feb 12.

Department of Chemistry, Carnegie Mellon University, Pittsburgh, PA, 15213, USA.

Thiolate-protected gold nanoclusters (NCs) are promising catalytic materials for the electrochemical CO reduction reaction (CO RR). In this work an atomic level modification of a Au NC is made by substituting two surface Au atoms with two Cd atoms, and it enhances the CO RR selectivity to 90-95 % at the applied potential between -0.5 to -0.9 V, which is doubled compared to that of the undoped Au . Additionally, the Cd-doped Au Cd exhibits the highest CO RR activity (2200 mA mg at -1.0 V vs. RHE) among the reported NCs. This synergetic effect between Au and Cd is remarkable. Density-functional theory calculations reveal that the exposure of a sulfur active site upon partial ligand removal provides an energetically feasible CO RR pathway. The thermodynamic energy barrier for CO formation is 0.74 eV lower on Au Cd than on Au . These results reveal that Cd doping can boost the CO RR performance of Au NCs by modifying the surface geometry and electronic structure, which further changes the intermediate binding energy. This work offers insights into the surface doping mechanism of the CO RR and bimetallic synergism.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/anie.202016129DOI Listing
March 2021

Optical Properties and Excited-State Dynamics of Atomically Precise Gold Nanoclusters.

Annu Rev Phys Chem 2021 Apr 9;72:121-142. Epub 2020 Dec 9.

Department of Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA; email:

Understanding the excited-state dynamics of nanomaterials is essential to their applications in photoenergy storage and conversion. This review summarizes recent progress in the excited-state dynamics of atomically precise gold (Au) nanoclusters (NCs). We first discuss the electronic structure and typical relaxation pathways of Au NCs from subpicoseconds to microseconds. Unlike plasmonic Au nanoparticles, in which collective electron excitation dominates, Au NCs show single-electron transitions and molecule-like exciton dynamics. The size-, shape-, structure-, and composition-dependent dynamics in Au NCs are further discussed in detail. For small-sized Au NCs, strong quantum confinement effects give rise to relaxation dynamics that is significantly dependent on atomic packing, shape, and heteroatom doping. For relatively larger-sized Au NCs, strong size dependence can be observed in exciton and electron dynamics. We also discuss the origin of coherent oscillations and their roles in excited-state relaxation. Finally, we provide our perspective on future directions in this area.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1146/annurev-physchem-090419-104921DOI Listing
April 2021

Atomically precise nanoclusters with reversible isomeric transformation for rotary nanomotors.

Nat Commun 2020 Nov 26;11(1):6019. Epub 2020 Nov 26.

State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 116023, Dalian, China.

Thermal-stimuli responsive nanomaterials hold great promise in designing multifunctional intelligent devices for a wide range of applications. In this work, a reversible isomeric transformation in an atomically precise nanocluster is reported. We show that biicosahedral [AuAg(PPh)Cl]SbF nanoclusters composed of two icosahedral AuAg units by sharing one common Au vertex can produce two temperature-responsive conformational isomers with complete reversibility, which forms the basis of a rotary nanomotor driven by temperature. Differential scanning calorimetry analysis on the reversible isomeric transformation demonstrates that the Gibbs free energy is the driving force for the transformation. This work offers a strategy for rational design and development of atomically precise nanomaterials via ligand tailoring and alloy engineering for a reversible stimuli-response behavior required for intelligent devices. The two temperature-driven, mutually convertible isomers of the nanoclusters open up an avenue to employ ultra-small nanoclusters (1 nm) for the design of thermal sensors and intelligent catalysts.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/s41467-020-19789-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7693277PMC
November 2020

Inhomogeneous Quantized Single-Electron Charging and Electrochemical-Optical Insights on Transition-Sized Atomically Precise Gold Nanoclusters.

ACS Nano 2020 Nov 16. Epub 2020 Nov 16.

Department of Chemistry, Georgia State University, Atlanta, Georgia 30302, United States.

Small differences in electronic structures, such as an emerging energy band gaps or the splitting of degenerated orbitals, are very challenging to resolve but important for nanomaterials properties. A signature electrochemical property called quantized double layer charging, , "continuous" one-electron transfers (1e, ETs), in atomically precise Au(TBBT), Au(BM), and Au(TBBT) is analyzed to reveal the nonmetallic to metallic transitions (whereas TBBT is 4--butylbenzenethiol and BM is benzyl mercaptan; abbreviated as Au, Au, and Au). Subhundred milli-eV energy differences are resolved among the "often-approximated uniform" peak spacings from multipairs of reversible redox peaks in voltammetric analysis, with single ETs as internal standards for calibration and under temperature variations. Cyclic and differential pulse voltammetry experiments reveal a 0.15 eV energy gap for Au and a 0.17 eV gap for Au at 298 K. Au is confirmed metallic, displaying a "bulk-continuum" charging response without an energy gap. The energy gaps and double layer capacitances of Au and Au increase as the temperature decreases. The temperature dependences of charging energies and HOMO-LUMO gaps of Au and Au are attributed to the counterion permeation and the steric hindrance of ligand, as well as their molecular compositions. With the subtle energy differences resolved, spectroelectrochemistry features of Au and Au are compared with ultrafast spectroscopy to demonstrate a generalizable analysis approach to correlate steady-state and transient energy diagram for the energy-in processes. Electrochemiluminescence (ECL), one of the energy-out processes after the charge transfer reactions, is reported for the three samples. The ECL intensity of Au is negligible, whereas the ECLs of Au and Au are relatively stronger and observable (but orders of magnitudes weaker than our recently reported bimetallic AuAg). Results from these atomically precise nanoclusters also demonstrate that the combined voltammetric and spectroscopic analyses, together with temperature variations, are powerful tools to reveal subtle differences and gain insights otherwise inaccessible in other nanomaterials.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acsnano.0c04914DOI Listing
November 2020

Atom-by-Atom Evolution of the Same Ligand-Protected Au, Au, AuCd, and Au Nanocluster Series.

J Am Chem Soc 2020 Nov 10. Epub 2020 Nov 10.

Department of Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States.

Atom-by-atom manipulation on metal nanoclusters (NCs) has long been desired, as the resulting series of NCs can provide insightful understanding of how a single atom affects the structure and properties as well as the evolution with size. Here, we report crystallizations of Au(SAdm) and AuCd(SAdm) (SAdm = adamantanethiolate) which link up with Au(SAdm) and Au(SAdm) NCs and form an atom-by-atom evolving series protected by the same ligand. Structurally, Au(SAdm) has an Au(SAdm) surface motif which is longer than the Au(SAdm) on Au(SAdm), whereas AuCd(SAdm) lacks one staple Au atom compared to Au(SAdm) and thus the surface structure is reconstructed. A single Cd atom triggers the structural transition from Au with a 10-atom bioctahedral kernel to AuCd with a 13-atom cuboctahedral kernel, and correspondingly, the optical properties are dramatically changed. The photoexcited carrier lifetime demonstrates that the optical properties and excited state relaxation are highly sensitive at the single atom level. By contrast, little change in both ionization potential and electron affinity is found in this series of NCs by theoretical calculations, indicating the electronic properties are independent of adding a single atom in this series. The work provides a paradigm that the NCs with continuous metal atom numbers are accessible and crystallizable when meticulously designed, and the optical properties are more affected at the single atom level than the electronic properties.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/jacs.0c09110DOI Listing
November 2020

Toward Active-Site Tailoring in Heterogeneous Catalysis by Atomically Precise Metal Nanoclusters with Crystallographic Structures.

Chem Rev 2021 01 17;121(2):567-648. Epub 2020 Sep 17.

Department of Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States.

Heterogeneous catalysis involves solid-state catalysts, among which metal nanoparticles occupy an important position. Unfortunately, no two nanoparticles from conventional synthesis are the same at the atomic level, though such regular nanoparticles can be highly uniform at the nanometer level (e.g., size distribution ∼5%). In the long pursuit of well-defined nanocatalysts, a recent success is the synthesis of atomically precise metal nanoclusters protected by ligands in the size range from tens to hundreds of metal atoms (equivalently 1-3 nm in core diameter). More importantly, such nanoclusters have been crystallographically characterized, just like the protein structures in enzyme catalysis. Such atomically precise metal nanoclusters merge the features of well-defined homogeneous catalysts (e.g., ligand-protected metal centers) and enzymes (e.g., protein-encapsulated metal clusters of a few atoms bridged by ligands). The well-defined nanoclusters with their total structures available constitute a new class of model catalysts and hold great promise in fundamental catalysis research, including the atomically precise size dependent activity, control of catalytic selectivity by metal structure and surface ligands, structure-property relationships at the atomic-level, insights into molecular activation and catalytic mechanisms, and the identification of active sites on nanocatalysts. This Review summarizes the progress in the utilization of atomically precise metal nanoclusters for catalysis. These nanocluster-based model catalysts have enabled heterogeneous catalysis research at the single-atom and single-electron levels. Future efforts are expected to achieve more exciting progress in fundamental understanding of the catalytic mechanisms, the tailoring of active sites at the atomic level, and the design of new catalysts with high selectivity and activity under mild conditions.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acs.chemrev.0c00495DOI Listing
January 2021

Pressure-Induced Optical Transitions in Metal Nanoclusters.

ACS Nano 2020 Sep 19;14(9):11888-11896. Epub 2020 Aug 19.

Department of Mechanical Engineering, Stanford University, Stanford, California 94305, United States.

Currently, a comprehensive understanding of the relationship between atomic structures and optical properties of ultrasmall metal nanoclusters with diameters between 1 and 3 nm is lacking. To address this challenge, it is necessary to develop tools for perturbing the atomic structure and modulating the optical properties of metal nanoclusters beyond what can be achieved using synthetic chemistry. Here, we present a systematic high-pressure study on a series of atomically precise ligand-protected metal nanoclusters. A diamond anvil cell is used as a high-pressure chamber to gradually compress the metal nanoclusters, while their optical properties are monitored . Our experimental results show that the photoluminescence (PL) of these nanoclusters is enhanced by up to 2 orders of magnitude at pressures up to 7 GPa. The absorption onset red-shifts with increasing pressure up to ∼12 GPa. Density functional theory calculations reveal that the red-shift arises because of narrowing of the spacing between discrete energy levels of the cluster due to delocalization of the core electrons to the carbon ligands. The pressure-induced PL enhancement is ascribed to (i) the enhancement of the near-band-edge transition strength, (ii) suppression of the nonradiative vibrations, and (iii) hindrance of the excited-state structural distortions. Overall, our results demonstrate that high pressure is an effective tool for modulating the optical properties and improving the luminescence brightness of metal nanoclusters. The insights into structure-property relations obtained here also contribute to the rational design of metal nanoclusters for various optical applications.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acsnano.0c04813DOI Listing
September 2020

Heteroatom Tracing Reveals the 30-Atom Au-Ag Bimetallic Nanocluster as a Dimeric Structure.

J Phys Chem Lett 2020 Sep 20;11(17):7307-7312. Epub 2020 Aug 20.

Department of Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States.

Understanding the formation of face-centered cubic (fcc) nanostructures at the atomic level remains a major task. With atomically precise nanoclusters (NCs) as model systems, herein we devised an atom-tracing strategy by heteroatom doping into Au(SR) (SR = S-CH) to label the specific positions in M(SR) NCs (M = Au/Ag), which clearly reveals the dimeric nature of M. Interestingly, the specific position is also consistent with the Ag-doping site in M(SR). Electronic orbital analysis shows intrinsic orbital localization at the two specific positions in M, which are decisive to the electronic structure of M, regardless of Au or Ag occupancy. The fcc dimeric NC, which would not be discovered without Ag tracing, provides a possible explanation for the wide accessibility of nonsuperatomic Au-SR NCs.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acs.jpclett.0c01977DOI Listing
September 2020

Atomically precise alloy nanoclusters: syntheses, structures, and properties.

Chem Soc Rev 2020 Sep 6;49(17):6443-6514. Epub 2020 Aug 6.

Department of Chemistry and Centre for Atomic Engineering of Advanced Materials, Anhui Province Key Laboratory of Chemistry for Inorganic/Organic Hybrid Functionalized Materials, Anhui University, Hefei, Anhui 230601, China.

Metal nanoclusters fill the gap between discrete atoms and plasmonic nanoparticles, providing unique opportunities for investigating the quantum effects and precise structure-property correlations at the atomic level. As a versatile strategy, alloying can largely improve the physicochemical performances compared to the corresponding homo-metal nanoclusters, and thus benefit the applications of such nanomaterials. In this review, we highlight the achievements of atomically precise alloy nanoclusters, and summarize the alloying principles and fundamentals, including the synthetic methods, site-preferences for different heteroatoms in the templates, and alloying-induced structure and property changes. First, based on various Au or Ag nanocluster templates, heteroatom doping modes are presented. The templates with electronic shell-closing configurations tend to maintain their structures during doping, while the others may undergo transformation and give rise to alloy nanoclusters with new structures. Second, alloy nanoclusters of specific magic sizes are reviewed. The arrangement of different atoms is related to the symmetry of the structures; that is, different atoms are symmetrically located in the nanoclusters of smaller sizes, and evolve into shell-by-shell structures at larger sizes. Then, we elaborate on the alloying effects in terms of optical, electrochemical, electroluminescent, magnetic and chiral properties, as well as the stability and reactivity via comparisons between the doped nanoclusters and their homo-metal counterparts. For example, central heteroatom-induced photoluminescence enhancement is emphasized. The applications of alloy nanoclusters in catalysis, chemical sensing, bio-labeling, and other fields are further discussed. Finally, we provide perspectives on existing issues and future efforts. Overall, this review provides a comprehensive synthetic toolbox and controllable doping modes so as to achieve more alloy nanoclusters with customized compositions, structures, and properties for applications. This review is based on publications available up to February 2020.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1039/c9cs00633hDOI Listing
September 2020

Seeing Ligands on Nanoclusters and in Their Assemblies by X-ray Crystallography: Atomically Precise Nanochemistry and Beyond.

J Am Chem Soc 2020 08 24;142(32):13627-13644. Epub 2020 Jul 24.

Department of Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States.

Ligands are of tremendous importance for colloidal nanoparticles (NPs) in terms of surface protection, size and shape control, tailoring properties, self-assembly, and applications. However, it is very challenging to obtain unambiguous information on the ligands and their interactions and patterning on NPs. The recent advent of atomically precise nanochemistry has opened new horizons. One can now see ligands with atomic resolution and understand their behavior on the surface of ultrasmall NPs (1-3 nm) and also in their assemblies. Such atomically precise NPs (or nanoclusters, NCs) bridge up with conventional NPs by providing unprecedented opportunities to reveal the specific patterns formed by intra- and inter-particle ligand interactions. In this Perspective, we first discuss how to achieve atomically precise NCs and determine their total structures. Then, we highlight the intra-particle ligand interactions (i.e., the ligand shell), including the various patterns formed on the NCs, the ligand patterning modes on facets and edges, and some aesthetic patterns assembled by ligands that are akin to biomolecular organization. The inter-particle ligand interactions and their roles in directing the self-assembly of NCs into coherent superlattices are also discussed, which provides a deep understanding of assembly mechanisms, with the insights from atomically precise NCs hinting for the assembly of conventional NPs. Overall, the success in achieving atomically precise NCs is expected to bring new opportunities to fields beyond nanochemistry, especially to materials design, engineering, and applications.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/jacs.0c05866DOI Listing
August 2020

Atomic-precision engineering of metal nanoclusters.

Dalton Trans 2020 Aug;49(31):10701-10707

Department of Chemistry, Carnegie Mellon University, Pittsburgh, PA 15213, USA.

Ultrasmall metal nanoparticles (below 2.2 nm core diameter) start to show discrete electronic energy levels due to strong quantum confinement effects and thus behave much like molecules. The size and structure dependent quantization induces a plethora of new phenomena, including multi-band optical absorption, enhanced luminescence, single-electron magnetism, and catalytic reactivity. The exploration of such new properties is largely built on the success in unveiling the crystallographic structures of atomically precise nanoclusters (typically protected by ligands, formulated as MnLmq, where M = metal, L = Ligand, and q = charge). Correlation between the atomic structures of nanoclusters and their properties has further enabled atomic-precision engineering toward materials design. In this frontier article, we illustrate several aspects of the precise engineering of gold nanoclusters, such as the single-atom size augmenting, single-atom dislodging and doping, precise surface modification, and single-electron control for magnetism. Such precise engineering involves the nanocluster's geometric structure, surface chemistry, and electronic properties, and future endeavors will lead to new materials design rules for structure-function correlations and largely boost the applications of metal nanoclusters in optics, catalysis, magnetism, and other fields. Following the illustrations of atomic-precision engineering, we have also put forth some perspectives. We hope this frontier article will stimulate research interest in atomic-level engineering of nanoclusters.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1039/d0dt01853hDOI Listing
August 2020

Structural distortion and electron redistribution in dual-emitting gold nanoclusters.

Nat Commun 2020 Jun 9;11(1):2897. Epub 2020 Jun 9.

Department of Chemistry, Carnegie Mellon University, Pittsburgh, PA, 15213, USA.

Deciphering the complicated excited-state process is critical for the development of luminescent materials with controllable emissions in different applications. Here we report the emergence of a photo-induced structural distortion accompanied by an electron redistribution in a series of gold nanoclusters. Such unexpected slow process of excited-state transformation results in near-infrared dual emission with extended photoluminescent lifetime. We demonstrate that this dual emission exhibits highly sensitive and ratiometric response to solvent polarity, viscosity, temperature and pressure. Thus, a versatile luminescent nano-sensor for multiple environmental parameters is developed based on this strategy. Furthermore, we fully unravel the atomic-scale structural origin of this unexpected excited-state transformation, and demonstrate control over the transition dynamics by tailoring the bi-tetrahedral core structures of gold nanoclusters. Overall, this work provides a substantial advance in the excited-state physical chemistry of luminescent nanoclusters and a general strategy for the rational design of next-generation nano-probes, sensors and switches.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/s41467-020-16686-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7283347PMC
June 2020

Ligand exchange on Au(SR): substituent site effects of aromatic thiols.

Nanoscale 2020 May;12(17):9423-9429

Department of Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA.

Understanding the critical roles of ligands (e.g. thiolates, SR) in the formation of metal nanoclusters of specific sizes has long been an intriguing task since the report of ligand exchange-induced transformation of Au38(SR)24 into Au36(SR')24. Herein, we conduct a systematic study of ligand exchange on Au38(SC2H4Ph)24 with 21 incoming thiols and reveal that the size/structure preference is dependent on the substituent site. Specifically, ortho-substituted benzenethiols preserve the structure of Au38(SR)24, while para- or non-substituted benzenethiols cause its transformation into Au36(SR)24. Strong electron-donating or -withdrawing groups do not make a difference, but they will inhibit full ligand exchange. Moreover, the crystal structure of Au38(SR)24 (SR = 2,4-dimethylbenzenethiolate) exhibits distinctive ππ stacking and "anagostic" interactions (indicated by substantially short AuH distances). Theoretical calculations reveal the increased energies of frontier orbitals for aromatic ligand-protected Au38, indicating decreased electronic stability. However, this adverse effect could be compensated for by the AuH-C interactions, which improve the geometric stability when ortho-substituted benzenethiols are used. Overall, this work reveals the substituent site effects based on the Au38 model, and highlights the long-neglected "anagostic" interactions on the surface of Au-SR NCs which improve the structural stability.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1039/d0nr01430cDOI Listing
May 2020

Heterometal-Doped M (M = Au/Ag/Cd) Nanoclusters with Large Dipole Moments.

ACS Nano 2020 Jun 21;14(6):6599-6606. Epub 2020 Apr 21.

Department of Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States.

Dipole moment (μ) is a critical parameter for molecules and nanomaterials as it affects many properties. In metal-thiolate (SR) nanoclusters (NCs), μ is commonly low (0-5 D) compared to quantum dots. Herein, we report a doping strategy to give giant dipoles (∼18 D) in M (M = Au/Ag/Cd) NCs, falling in the experimental trend for II-VI quantum dots. In M NCs, high μ is caused by the Cd-Br bond and the arrangement of heteroatoms along the axis. Strong dipole-dipole interactions are observed in crystalline state, with energy exceeding 5 kJ/mol, directing a "head-to-tail" alignment of AuAgCd(SR)X (SR = adamantanethiolate) dipoles. The alignment can be controlled by doping. The optical absorption peaks of M show solvent polarity-dependent shifts (∼25 meV) with negative solvatochromism. Detailed electronic structures of M are revealed by density functional theory and time-dependent DFT calculations. Overall, the doping strategy for obtaining large dipole moments demonstrates an atomic-level design of clusters with useful properties.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acsnano.0c01000DOI Listing
June 2020

Chirality and Surface Bonding Correlation in Atomically Precise Metal Nanoclusters.

Adv Mater 2020 Oct 17;32(41):e1905488. Epub 2020 Mar 17.

Department of Chemistry, Carnegie Mellon University, Pittsburgh, PA, 15213, USA.

Chirality is ubiquitous in nature and occurs at all length scales. The development of applications for chiral nanostructures is rising rapidly. With the recent achievements of atomically precise nanochemistry, total structures of ligand-protected Au and other metal nanoclusters (NCs) are successfully obtained, and the origins of chirality are discovered to be associated with different parts of the cluster, including the surface ligands (e.g., swirl patterns), the organic-inorganic interface (e.g., helical stripes), and the kernel. Herein, a unified picture of metal-ligand surface bonding-induced chirality for the nanoclusters is proposed. The different bonding modes of M-X (where M = metal and X = the binding atom of ligand) lead to different surface structures on nanoclusters, which in turn give rise to various characteristic features of chirality. A comparison of Au-thiolate NCs with Au-phosphine ones further reveals the important roles of surface bonding. Compared to the Au-thiolate NCs, the Ag/Cu/Cd-thiolate systems exhibit different coordination modes between the metal and the thiolate. Other than thiolate and phosphine ligands, alkynyls are also briefly discussed. Several methods of obtaining chiroptically active nanoclusters are introduced, such as enantioseparation by high-performance liquid chromatography and enantioselective synthesis. Future perspectives on chiral NCs are also proposed.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/adma.201905488DOI Listing
October 2020

Controlling magnetism of Au(TBBT) nanoclusters at single electron level and implication for nonmetal to metal transition.

Chem Sci 2019 Nov 4;10(42):9684-9691. Epub 2019 Sep 4.

Department of Chemistry , Carnegie Mellon University , 4400 Fifth Ave , Pittsburgh , PA , USA . Email: ; Email:

The transition from the discrete, excitonic state to the continuous, metallic state in thiolate-protected gold nanoclusters is of fundamental interest and has attracted significant efforts in recent research. Compared with optical and electronic transition behavior, the transition in magnetism from the atomic gold paramagnetism (Au 6s) to the band behavior is less studied. In this work, the magnetic properties of 1.7 nm [Au(TBBT)] nanoclusters (where TBBT = 4--butylbenzenethiolate) with 81 nominal "valence electrons" are investigated by electron paramagnetic resonance (EPR) spectroscopy. Quantitative EPR analysis shows that each cluster possesses one unpaired electron (spin), indicating that the electrons fill into orbitals instead of a band, for that one electron in the band would give a much smaller magnetic moment. Therefore, [Au(TBBT)] possesses a nonmetallic electronic structure. Furthermore, we demonstrate that the unpaired spin can be removed by oxidizing [Au(TBBT)] to [Au(TBBT)] and the nanocluster transforms from paramagnetism to diamagnetism accordingly. The UV-vis absorption spectra remain the same in the process of single-electron loss or addition. Nuclear magnetic resonance (NMR) is applied to probe the charge and magnetic states of Au(TBBT), and the chemical shifts of 52 surface TBBT ligands are found to be affected by the spin in the gold core. The NMR spectrum of Au(TBBT) shows a 13-fold splitting with 4-fold degeneracy of 52 TBBT ligands, which are correlated to the quasi- symmetry of the ligand shell. Overall, this work provides important insights into the electronic structure of Au(TBBT) by combining EPR, optical and NMR studies, which will pave the way for further understanding of the transition behavior in metal nanoclusters.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1039/c9sc02736jDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6977549PMC
November 2019

Atomically resolved AuCu(SR) nanoalloy reveals Marks decahedron truncation and Penrose tiling surface.

Nat Commun 2020 Jan 24;11(1):478. Epub 2020 Jan 24.

Department of Chemistry, Carnegie Mellon University, Pittsburgh, PA, 15213, United States.

Gold-copper alloys have rich forms. Here we report an atomically resolved [AuCu(p-MBT)]Cl nanoalloy (p-MBT = SPh-p-CH). This nanoalloy exhibits unusual structural patterns. First, two Cu atoms are located in the inner 7-atom decahedral kernel (M, M = Au/Cu). The M kernel is then enclosed by a second shell of homogold (Au), giving rise to a two-shelled M (i.e. AuCu) full decahedron. A comparison of the non-truncated M decahedron with the truncated homogold Au kernel in similar-sized gold nanoparticles provides for the first time an explanation for Marks decahedron truncation. Second, a Cu(SR) exterior cage resembling a 3D Penrose tiling protects the M decahedral kernel. Compared to the discrete staple motifs in gold:thiolate nanoparticles, the Cu-thiolate surface of AuCu forms an extended cage. The Cu-SR Penrose tiling retains the M kernel's high symmetry (D). Third, interparticle interactions in the assembly are closely related to the symmetry of the particle, and a "quadruple-gear-like" interlocking pattern is observed.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/s41467-020-14400-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6981204PMC
January 2020

Three-Stage Evolution from Nonscalable to Scalable Optical Properties of Thiolate-Protected Gold Nanoclusters.

J Am Chem Soc 2019 12 6;141(50):19754-19764. Epub 2019 Dec 6.

Department of Chemistry , Carnegie Mellon University , Pittsburgh , Pennsylvania 15213 , United States.

The evolution of the optical properties of gold nanoclusters (NCs) versus size is of great importance because it not only reveals the nature of quantum confinement in NCs, but also helps to understand how the molecular-like Au NCs transit to plasmonic nanoparticles. While some work has been done in studying the optical properties of NCs of certain individual sizes, the global picture remains unclear, such as the detailed relationship between size/structure and properties. Here, we investigate the grand evolution of the optical properties by comparing the steady-state absorption, bandgap, transient absorption, as well as carrier dynamics of a series of thiolate-protected gold NCs ranging from tens to hundreds of gold atoms. We find that, on the basis of their optical behaviors, gold NCs can be classified into three groups: (i) ultrasmall NCs (ca. <50 Au atoms) are nonscalable as their optical properties are strongly dependent on the structure rather than size; (ii) medium-sized NCs (about 50-100 Au atoms) show both size- and structure-dependent optical properties; and (iii) large-sized gold NCs (ca. >100 Au atoms) exhibit optical properties solely dependent on size, and the structure effect fades out. Unraveling the grand evolution from nonscalable to scalable optical properties and their mechanisms will greatly deepen scientific understanding of the nature of quantum-sized gold NCs and will also provide implications for plasmonic NPs.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/jacs.9b09066DOI Listing
December 2019

Au Ag Nanoclusters with Non-Metallicity: A Drum of Silver-Rich Sites Enclosed in a Marks-Decahedral Cage of Gold-Rich Sites.

Angew Chem Int Ed Engl 2019 Dec 8;58(52):18798-18802. Epub 2019 Nov 8.

Department of Chemistry, Carnegie Mellon University, Pittsburgh, PA, 15213, USA.

The synthesis and structure of atomically precise Au Ag (average x=98) alloy nanoclusters protected by 55 ligands of 4-tert-butylbenzenethiolate are reported. This large alloy structure has a decahedral M (M=Au/Ag) core. The Au atoms are localized in the truncated Marks decahedron. In the core, a drum of Ag-rich sites is found, which is enclosed by a Marks decahedral cage of Au-rich sites. The surface is exclusively Ag-SR; X-ray absorption fine structure analysis supports the absence of Au-S bonds. The optical absorption spectrum shows a strong peak at 523 nm, seemingly a plasmon peak, but fs spectroscopic analysis indicates its non-plasmon nature. The non-metallicity of the Au Ag nanocluster has set up a benchmark to study the transition to metallic state in the size evolution of bimetallic nanoclusters. The localized Au/Ag binary architecture in such a large alloy nanocluster provides atomic-level insights into the Au-Ag bonds in bimetallic nanoclusters.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/anie.201908694DOI Listing
December 2019

Luminescence and Electron Dynamics in Atomically Precise Nanoclusters with Eight Superatomic Electrons.

J Am Chem Soc 2019 Nov 14;141(47):18715-18726. Epub 2019 Nov 14.

Department of Chemistry , Kansas State University , Manhattan , Kansas 66506 , United States.

The [Au(SR)] and [Au(dppe)Cl] [dppe = 1,2-bis(diphenylphosphino)ethane] nanoclusters both possess a 13-atom icosahedral core with 8 delocalized superatomic electrons (8e), but their emission properties and time-resolved electron dynamics differ significantly. In this work, experimental photoluminescence and photoluminescence decay measurements are combined with time-dependent density functional theory calculations of radiative and nonradiative decay properties and lifetimes to elucidate the similarities and differences in the emission of these two nanoclusters with similar cores. In this work, the photodynamic properties of [Au(dppe)Cl] are elucidated theoretically for the first time. [Au(dppe)Cl] exhibits a single strong emission peak compared to the weaker bimodal luminescence of [Au(SR)] (modeled here as [Au(SH)]). The strongly emissive state is found to arise from deexcitation out of the S state, similar to what is seen for [Au(SH)]. Both theory and experiment exhibit microsecond lifetimes for this state. Transient absorption measurements and theoretical calculations demonstrate that the excited-state lifetimes for higher excited states are typically less than 1 ps. The decay times for the higher excited states of [Au(dppe)Cl] and its model compound [Au(pe)Cl] [pe = 1,2-bis(phosphino)ethane] are observed to be shorter than the lifetimes of the corresponding states of [Au(SR)]; this occurs because the energy gap separating degenerate sets of unoccupied orbitals is only ∼0.2 eV in [Au(dppe)Cl] compared to a ∼0.6 eV energy gap in [Au(SH)].
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/jacs.9b07626DOI Listing
November 2019

Fusion growth patterns in atomically precise metal nanoclusters.

Nanoscale 2019 Nov 11;11(41):19158-19165. Epub 2019 Sep 11.

Department of Chemistry, Carnegie Mellon University, Pittsburgh, PA 15213, USA.

Atomically precise nanoclusters of coinage metals in the 1-3 nm size regime have been intensively pursued in recent years. Such nanoclusters are attractive as they fill the gap between small molecules (<1 nm) and regular nanoparticles (>3 nm). This intermediate identity endows nanoclusters with unique physicochemical properties and provides nanochemists opportunities to understand the fundamental science of nanomaterials. Metal nanoparticles are well known to exhibit plasmon resonances upon interaction with light; however, when the particle size is downscaled to the nanocluster regime, the plasmons fade out and step-like absorption spectra characteristic of cluster sizes are manifested due to strong quantum confinement effects. Recent research has revealed that nanoclusters are commonly composed of a distinctive kernel and a surface-protecting shell (or staple-like metal-ligand motifs). Understanding the kernel configuration and evolution is one of the central topics in nanoscience research. This Review summarizes the recent progress in identifying the growth patterns of atomically precise coinage nanoclusters. Several basic kernel units have been observed, such as the M, M and M polyhedrons (where, M = metal atom). Among them, the tetrahedral M and icosahedral M units are the most common ones, which are adopted as building blocks to construct larger kernel structures via various fusion or aggregation modes, including the vertex- and face-sharing mode, the double-strand and alternate single-strand growth, and cyclic fusion of units, as well as the fcc-based cubic growth pattern. The identification of the kernel growth pathways has led to deeper understanding of the evolution of electronic structure and optic properties.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1039/c9nr05789gDOI Listing
November 2019
-->