Molecular mimetic self-assembly of noble metal nanoclusters

Ph.DDOCTOR OF PHILOSOPH

Heating or cooling: temperature effects on the synthesis of atomically precise gold nanoclusters

Developing an efficient, well-controlled synthesis strategy for gold nanoclusters (Au NCs) is crucial for delivering their expected applications in many fields; and such development requires fundamental understandings on the synthetic chemistry. The synthesis of Au NCs typically consists of a pair of reversible reactions: a fast reduction-growth reaction and a slow size-focusing reaction. Here we demonstrate that the above two reactions can be well-balanced while accelerated in a heated synthesis protocol, thus providing an efficient and scalable synthesis method to obtain thermodynamically favorable Au25(SR)18 NCs (SR denotes thiolate ligand) with high yield (>95% on gold atom basis) and fast kinetics. By investigating the Au NC formation behavior at different temperature, we identified the endothermic nature of the reductive formation of Au25(SR)18 NCs from Au(I)-thiolate complex precursors. More interestingly, if overheated, after the formation of Au25(SR)18, there exists an irreversible first-order reaction, which could transform Au25(SR)18 into Au NCs of mixed sizes. As a result, 40 °C is identified as the optimal temperature to synthesize Au25(SR)18 in aqueous solution, as the half-life of the transformation reaction (67.8 h) is much longer than the time needed to obtain high yield Au25(SR)18. The detailed understandings on the temperature effects of Au NC synthesis would facilitate the development of efficient synthesis strategies for atomically precise Au NCs with predesigned size, composition and structure

Toward greener synthesis of gold nanomaterials: from biological to biomimetic synthesis

In the past two decades, the use of biomolecules, either from biological or biomimetic systems (or so-called biological or biomimetic synthesis), has emerged as a promising green approach to synthesize gold nanomaterials (Au NMs). Here, we describe recent progress on the biological and biomimetic syntheses of Au NMs. We focus our discussions on the selection principles of biomolecules, synthesis mechanisms involving biomolecules, recent evolution from biological to biomimetic synthesis, and the contributions of bioinspired synthesis to green production of Au NMs. We hope this review will provide a guideline for the green synthesis of Au NMs and other metal NMs, further paving their way toward practical applications in the field of biomedicine

Aggregation-induced emission in luminescent metal nanoclusters

10.1093/nsr/nwaa208National Science Review86nwaa20

Electrospray Ionization mass spectrometry: a powerful platform for noble-metal nanocluster analysis

Electrospray ionization mass spectrometry (ESI-MS) is an analytical technique that measures the mass of a sample through “soft” ionization. Recent years have witnessed a rapid growth of its application in noble-metal nanocluster (NC) analysis. ESI-MS is able to provide the mass of a noble-metal NC analyte for the analysis of their composition (n, m, q values in a general formula [MnLm]q), which is crucial in understanding their properties. This review attempts to present various developed techniques for the determination of the composition of noble metal NCs by ESI-MS. Additionally, advanced applications that use ESI-MS to further understand the reaction mechanism, complexation behavior, and structure of noble metal NCs are introduced. From the comprehensive applications of ESI-MS on noble-metal NCs, more possibilities in nanochemistry can be opened up by this powerful technique

How Work-Family Conflict Influenced the Safety Performance of Subway Employees during the Initial COVID-19 Pandemic: Testing a Chained Mediation Model

This study examined the impact of work-family conflict on subway employees' safety performance during the initial wave of the COVID-19 pandemic. We proposed a chain mediation model in which job burnout and affective commitment play mediating roles in this process. Using questionnaire data from 632 Chinese subway employees during February 2020, structural equation modeling analyses were performed. The analyses showed that work-family conflict had a significant negative impact on subway employee safety performance. Moreover, job burnout completely mediated the influence of work-family conflict on safety performance, while affective commitment only partially mediated the influence of job burnout on safety performance. These findings suggest the important role played by Work-Family balance during the pandemic and contribute to a deeper understanding of the inner mechanisms. We also discussed several practical implications for organizations to reduce the negative impact of work-family conflict on safety performance

Converting ultrafine silver nanoclusters to monodisperse silver sulfide nanoparticles via a reversible phase transfer protocol

To achieve better control of the formation of silver sulfide (Ag2S) nanoparticles, ultrasmall Ag nanoclusters protected by thiolate ligands (Ag-44(SR)(30) and Ag-16(GSH)(9)) are used as precursors, which, via delicate chemistry, can be readily converted to monodisperse Ag2S nanoparticles with controllable sizes (4-16 nm) and switchable solvent affinity (between aqueous and organic solvents). This new synthetic protocol makes use of the atomic monodispersity and rich surface chemistry of Ag nanoclusters and a novel two-phase protocol design, which results in a well-controlled reaction environment for the formation of Ag2S nanoparticles

Converting ultrafine silver nanoclusters to monodisperse silver sulfide nanoparticles via a reversible phase transfer protocol

To achieve better control of the formation of silver sulfide (Ag_2S) nanoparticles, ultrasmall Ag nanoclusters protected by thiolate ligands (Ag_(44)(SR)_(30) and Ag_(16)(GSH)_9) are used as precursors, which, via delicate chemistry, can be readily converted to monodisperse Ag_2S nanoparticles with controllable sizes (4–16 nm) and switchable solvent affinity (between aqueous and organic solvents). This new synthetic protocol makes use of the atomic monodispersity and rich surface chemistry of Ag nanoclusters and a novel two-phase protocol design, which results in a well-controlled reaction environment for the formation of Ag_2S nanoparticles