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Aggregation-induced emission is a promising pathway to get high photoluminescence from metal nanocluster assemblies. The self-assembly of metal nanoclusters with regular morphologies can restrict the rotation and vibration modes of capping ligands, reduce nanoclusters' non-radiative decay, and finally result in an aggregation-induced strong emission. In this study, silver nanocluster self-assemblies stabilized by thiosalicylic acid (TSA) were prepared in water by equilibrium shifting, which exhibit nanofiber-like morphologies. The resulting silver nanocluster self-assemblies exhibit aggregation-induced emission in solid or aggregated state with a decent quantum yield i.e., 13.05%. The obtained silver nanocluster self-assemblies were thoroughly characterized by fluorescence spectroscopy, UV-visible absorption spectroscopy, X-ray photoelectron spectroscopy (XPS), matrix assisted laser desorption/ionization time-of-flight mass spectroscopy (MALDI-TOF), powder X-ray diffraction (PXRD) and high-resolution transmission electron microscopy (HRTEM). These silver nanocluster self-assemblies with high photoluminescence in aggregated state may have potential use in light emitting devices and bioapplications.

Copper nanoclusters (CuNCs) exhibit susceptibility to oxidation in the subnanometer size range. In this work, a facile and green protocol is reported for the successful synthesis of water soluble CuNCs, with poly(vinylpyrrolidone) as a template and ascorbic acid as a mild reducing agent. The as-prepared CuNCs exhibit a green fluorescence and high quantum yield (QY = 44.67%) in water, which is the highest among the reported water soluble CuNCs. The origin of their highly luminescent nature was also investigated. In addition, the obtained CuNCs show good tolerability to high ionic strength, superior antioxidation properties, good photostability, time-stability, a large Stokes shift and ultralow cytotoxicity, laying the foundation for living cell imaging in THP-1 macrophages. A bright green fluorescence can be observed from the cells, indicating the potential practicality of CuNCs as a fluorescence marker in bioapplications. Interestingly, the as-prepared CuNCs exhibit a good selective fluorescence quenching response towards trinitrophenol over other nitro compounds. Furthermore, CuNCs were employed for sensing trinitrophenol based on the inner filter effect. A good linear relationship was obtained in the low concentration range of trinitrophenol, with a limit of detection of 3.91 × 10-7 M in aqueous medium. This result suggests the potential application of CuNCs as a probe in sensing and monitoring toxic trinitrophenol in the field of environmental security.

Achieving water splitting at low overpotential with high oxygen evolution efficiency and stability is important for realizing solar to chemical energy conversion devices. Herein we report the synthesis, characterization and electrochemical evaluation of highly active nickel nanoclusters (Ni NCs) for water oxidation at low overpotential. These atomically precise and monodisperse Ni NCs are characterized by using UV-visible absorption spectroscopy, single crystal X-ray diffraction and mass spectrometry. The molecular formulae of these Ni NCs are found to be Ni4(PET)8 and Ni6(PET)12 and are highly active electrocatalysts for oxygen evolution without any pre-conditioning. Ni4(PET)8 are slightly better catalysts than Ni6(PET)12 which initiate oxygen evolution at an amazingly low overpotential of ∼1.51 V (vs. RHE; η≈ 280 mV). The peak oxygen evolution current density (J) of ∼150 mA cm(-2) at 2.0 V (vs. RHE) with a Tafel slope of 38 mV dec(-1) is observed using Ni4(PET)8. These results are comparable to the state-of-the-art RuO2 electrocatalyst, which is highly expensive and rare compared to Ni-based materials. Sustained oxygen generation for several hours with an applied current density of 20 mA cm(-2) demonstrates the long-term stability and activity of these Ni NCs towards electrocatalytic water oxidation. This unique approach provides a facile method to prepare cost-effective, nanoscale and highly efficient electrocatalysts for water oxidation.

At present, thiol ligands are generally used whenever the classical Brust–Schiffrin two-phase method is employed to prepare metal nanoparticles. In general, the previous research was mainly focused on utilizing small molecular thiol compounds or thiol polymers as the stabilizers in organic phase to obtain small sized and uniform gold nanoparticles (Au NPs). Such preparations are usually associated with the problems of ligand exchange on the nanoparticle's surface due to strong Au–thiol interaction. Herein, we report an approach to produce fairly uniform Au NPs with diameters about 2–6 nm using thioether end-functional polymer ligands (DDT–PVAc and PTMP–PVAc) as the capping agents. These nanoparticles are thoroughly characterized using DLS, TEM, UV-Vis spectroscopy and other complementary techniques. The results indicate that multidentate thioether polymeric ligands (PTMP–PVAc) lead to formation of smaller but special ‘multimer’ morphology in organic phase; whereas fairly uniform nanoparticles are produced using monodentate thioether functionalized ligands (DDT–PVAc). Further modification of such polymer ligands to introduce the hydrophilic functionalities realizes the phase transfer of Au NPs from organic to aqueous media.

Latent fingerprints are made visible in a single step by in situ growth of gold nanoparticles on ridge patterns. The chemicals, among the essential components of human sweat, found responsible for the formation and assembly of gold nanoparticles are screened and used as ink to write invisible patterns, using common ball pen and inkjet printer, which are then developed by selectively growing gold nanoparticles by soaking them in gold salt solution.