Raising Near-Infrared Photoluminescence Quantum Yield of Au Quantum Rod to 50% in Solutions and 75% in Films.

Highly emissive gold nanoclusters (NCs) in the near-infrared (NIR) region are of wide interest, but challenges arise from the excessive nonradiative dissipation. Here, we demonstrate an effective suppression of the motions of surface motifs on the Au(PET) rod (PET = 2-phenylethanethiolate) by noncoordinative interactions with amide molecules and accordingly raise the NIR emission (875/1045 nm peaks) quantum yield (QY) from 18% to 50% in deaerated solution at room temperature, which is rare in Au NCs. Cryogenic photoluminescence measurements indicate that amide molecules effectively suppress the vibrations associated with the Au-S staple motifs on Au and also enhance the radiative relaxation, both of which lead to stronger emission.

Bright near-infrared emission from the Au(SR) nanocluster.

The synthesis of atomically precise gold nanoclusters with high photoluminescence quantum yield (PLQY) in the near-infrared (NIR) region and understanding their photoluminescence mechanism are crucial for both fundamental science and practical applications. Herein, we report a highly luminescent, molecularly pure Au(PET) (PET = 2-phenylethanethiolate) nanocluster with PLQY of 19% in the NIR range (915 nm). Steady state and time-resolved PL analyses, as well as temperature-dependent PL measurements reveal the emission nature of Au(PET), which consists of prompt fluorescence (weak), thermally activated delayed fluorescence (TADF), and phosphorescence (predominant).

Three-atom-wide gold quantum rods with periodic elongation and strongly polarized excitons.

Atomically precise control over anisotropic nanoclusters constitutes a grand challenge in nanoscience. In this work, we report our success in achieving a periodic series of atomically precise gold quantum rods (abbrev. Au QRs) with unusual excitonic properties.

Visible to NIR-II Photoluminescence of Atomically Precise Gold Nanoclusters.

Atomically precise gold nanoclusters (NCs) have emerged as a new class of precision materials and attracted wide interest in recent years. One of the unique properties of such nanoclusters pertains to their photoluminescence (PL), for it can widely span visible to near-infrared-I and -II wavelengths (NIR-I/II), and even beyond 1700 nm by manipulating the size, structure, and composition. The current research efforts focus on the structure-PL correlation and the development of strategies for raising the PL quantum yields, which is nontrivial when moving from the visible to the near-infrared wavelengths, especially in the NIR-II regions.

Elucidating the Near-Infrared Photoluminescence Mechanism of Homometal and Doped M(SR) Nanoclusters.

More than a decade of research on the photoluminescence (PL) of classic Au(SR) and its doped nanoclusters (NCs) still leaves many fundamental questions unanswered due to the complex electron dynamics. Here, we revisit the homogold Au (ligands omitted hereafter) and doped NCs, as well as the Ag and doped ones, for a comparative study to disentangle the influencing factors and elucidate the PL mechanism. We find that the strong electron-vibration coupling in Au leads to weak PL in the near-infrared region (∼1000 nm, quantum yield QY = 1% in solution at room temperature).

Preserving Macroporosity in Type III Porous Liquids.

Preserving large permanent pore structures in a fluid may endow conventional liquids with emergent physical properties. However, such materials are challenging to make because of the tendency of the pores to be filled and occupied by the solvent molecules. Here, we report the design and synthesis of the first Type III porous liquid (PL) containing uniform yet stable 480 nm cavities.

Photoluminescence of the Au(SR) nanocluster comprises three radiative processes.

Photoluminescence of ultrasmall, atomically precise gold nanoclusters constitutes an area of significant interest in recent years for both fundamental research and biological applications. However, the exploration of near-infrared photoluminescence of gold nanoclusters is still in its infancy due to the limitations of synthetic methods and characterization techniques. Herein, the photoluminescence properties of an Au(PET) (PET = 2-phenylethanethiolate) nanocluster are investigated in detail.

Near-Infrared Dual Emission from the Au(SR) Nanocluster and Tailoring of Intersystem Crossing.

This work presents the synthesis and intriguing photoluminescence of the Au(PET) (PET = 2-phenylethanethiolate) nanocluster (NC). The Au(PET) NC exhibits dual emission at 875 and 1040 nm, which are revealed to be fluorescence and phosphorescence, respectively. The emission quantum yield (QY) of Au(PET) in dichloromethane is 11.

Exploration of Hierarchical Metal-Organic Framework as Ultralight, High-Strength Mechanical Metamaterials.

Due to the extraordinarily high surface to volume ratio and enormous structural and chemical diversities, metal-organic frameworks (MOFs) have drawn much attention in applications such as heterogeneous catalysis, gas storage separation, and drug delivery, and so on. However, the potential of MOF materials as mechanical metamaterials has not been investigated. In this work, we demonstrated that through the concerted effort of molecular construct and mesoscopic structural design, hierarchical MOFs can exhibit superb mechanical properties.

Atomically precise metal nanoclusters meet metal-organic frameworks.

Significant progress has been made in both fields of atomically precise metal nanoclusters (NCs) and metal-organic frameworks (MOFs) in recent years. A promising direction is to integrate these two classes of materials for creating unique composites with improved properties for catalysis and other applications. NCs incorporated with MOFs exhibit an optimized catalytic performance in many catalytic reactions, in which MOFs play a vital supporting role or as cocatalysts.

Reverse synthesis of yolk-shell metal-organic frameworks.

We report the first examples of yolk-shell metal-organic framework (MOF) heterostructures based on topologically distinct MOFs: ZIF-8/ZIF-67 and UiO-66. This was accomplished through an innovative reverse synthesis strategy: A hollow UiO-66 was first constructed; the precusors of the ZIFs were then loaded into the cavity of hollow UiO-66 through a mixed solvent impregnation method; subsequent crystallization under solvothermal condition led to the formation of yolk-shell MOFs containing one or multiple ZIF particles confined within a chemically robust single crystalline UiO-66 shell.

Tracking and Visualization of Functional Domains in Stratified Metal-Organic Frameworks Using Gold Nanoparticles.

We report here a new technique for the identification and visualization of functional domains in stratified metal-organic frameworks (MOFs). The technique, namely, gold diffusion enabled domain identification, utilizes the diffusion of Au nanoparticles within MOF cavities to track and selectively stain the more Au-philic domain in an MOF particle thereby allowing direct observation of domains, determination of domain sequences, and, in certain cases, domain boundaries under transmission electron microscopy. This method is an excellent tool for studying MOF materials with complex domain hierarchy.

Tuning Metal-Organic Framework Nanocrystal Shape through Facet-Dependent Coordination.

We studied coordination-dependent surfactant binding on shaped MOF nanocrystals. Cetyltrimethylammonium bromide (CTAB) on the surface of ZIF-8 was used as a model system. Infrared spectroscopic analysis and molecular dynamics simulations reveal different coordination environments for Zn nodes on {100} and {110} facets, resulting in different CTAB adsorption.

Directional Engraving within Single Crystalline Metal-Organic Framework Particles via Oxidative Linker Cleaving.

An oxidative linker cleaving (OLC) process was developed for surgical manipulation of the engraving process within single crystalline MOFs particles. The strategy relies on selective degradation of 2,5-dihydroxyterephthalic acid linker into small molecular fragments by oxidative ring-opening reactions, resulting in controllable scissoring of framework. By regulation of the generation and diffusion of oxidative species, the core MOFs will undergo divergent etching routes, producing a series of single crystalline hollow and yolk-shell MOF structures.

Aperture-Opening Encapsulation of a Transition Metal Catalyst in a Metal-Organic Framework for CO Hydrogenation.

The aperture-opening process resulting from dissociative linker exchange in zirconium-based metal-organic framework (MOF) UiO-66 was used to encapsulate the ruthenium complex (PNP)Ru(CO)HCl in the framework (PNP = 2,6-bis((di- tert-butyl-phosphino)methyl)pyridine). The resulting encapsulated complex, [Ru]@UiO-66, was a very active catalyst for the hydrogenation of CO to formate. Unlike the analogous homogeneous catalyst, [Ru]@UiO-66 could be recycled five times, showed no evidence for bimolecular catalyst decomposition, and was less prone to catalyst poisoning.

Using a Multi-Shelled Hollow Metal-Organic Framework as a Host to Switch the Guest-to-Host and Guest-to-Guest Interactions.

A bio-inspired design of using metal-organic framework (MOF) microcrystals with well-defined multi-shelled hollow structures was used as a matrix to host multiple guests including molecules and nanoparticles at separated locations to form a hierarchical material, mimicking biological structures. The interactions such as energy transfer (ET) between different guests are regulated by precisely fixing them in the MOF shells or encapsulating them in the cavities between the MOF shells. The proof-of-concept design is demonstrated by hosting chromophore molecules including rhodamine 6G (R6G) and 7-amino-4-(trifluoromethyl)coumarin (C-151), as well as metal nanoparticles (Pd NPs) into the multi-shelled hollow zeolitic imidazolate framework-8 (ZIF-8).

Activation of peroxymonosulfate by surfactants as the metal-free catalysts for organic contaminant removal.

The present work described that tertiary ammonium surfactants containing bromide ion as novel metal-free catalysts were innovatively coupled with peroxymonosulfate (PMS) to build a simple catalytic oxidation system, possessing outstanding catalytic ability with organic dye Reactive Red M-3BE (RR M-3BE) as the target pollutant. Furthermore, cetyltrimethylammonium bromide (CTAB), a representative of cationic surfactant, was selected to further investigate the catalytic oxidation performance. It is found that at the critical micelle concentration (CMC) of CTAB, the oxidation efficiency of the CTAB/PMS system was optimal due to the strong electrostatic attraction between the CTA micelle and reactive anions (Br and HSO), concentrating HSO and Br at the micellar surface, which accelerated the catalytic oxidation reaction between Br and HSO, generating a mass of highly active reactive species.