Hong-Wu Zhang

Supramolecular hydrogels for creating gold and silver nanoparticles in situ

In situ fabrication of metal nanostructures such as metal nanoparticles (NPs) and nanoclusters (NCs) in supramolecular gels (particularly hydrogels) is important for the construction of novel and promising bio-/chemosensing platforms, and catalytic and antibacterial functional materials, because of their intriguing properties. Reported herein are our recent findings, in which we employed sodium salts of a series of structurally similar bile acid derivatives (BAs) to construct supramolecular hydrogels incorporating various metal ions including Ag+ and Au3+, and to investigate the feasibility of in situ fabrication of Ag NPs and Au NPs in these supramolecular hydrogel systems via a simple and environmentally friendly method of photoreduction, without adding any external reducing or stabilizing agents. These results demonstrated that the gelation ability of BAs induced by the coordination of Mn+ could also be tuned by a slight structural alteration of BAs, and forming Ag or Au NPs as effective nodes could facilitate increasing strength of the resulting supramolecular hydrogels. This is the first reported supramolecular hydrogel system capable of in situ formation of both Ag NPs and Au NPs, expected to open an entry for preparing novel functional gel materials incorporating metal nanostructures for numerous potential applications.

In situ synthesis of red emissive copper nanoclusters in supramolecular hydrogels

We report a simple and environmentally friendly method for the in situ synthesis of red emissive Cu nanoclusters (NCs) in supramolecular hydrogels via employing a series of bile acid derivatives (BAs) as pre-gelators. The encapsulated Cu NCs demonstrated excellent catalytic performance in the methylene blue (MB)–hydrazine (N2H4) reduction system.

Peroxidase-like activity of ferric ions and their application to cysteine detection

Although Fe3O4 magnetic nanoparticles (MNPs) have recently been developed as artificial enzymes in a wide range of applications, there is a debate on whether the observed peroxidase-like activity originates from the nature of the intact MNPs themselves or from the Fenton reaction of surface bound and free ferric/ferrous ions. In this work, Fe3+ ions serving as the peroxidase mimic towards the 3,3′,5,5′-tetramethyl benzidine (TMB)–H2O2 system was investigated in detail for the first time. Experimental results revealed that the peroxidase-like activity of Fe3+ ions is much higher than that of Fe3O4 MNPs. On the basis of these findings, a simple, highly sensitive and selective colorimetric sensing platform for L-cysteine (L-Cys) was developed with a limit of detection (LOD) as low as 0.97 μM.

Supramolecular aggregation/disaggregation-based molecular sensing: a review focused on investigations from China

Supramolecular aggregation and disaggregation induced by external stimuli can impact the optical or electrical signals of the aggregates/constituting units (receptors). Therefore, manipulating supramolecular aggregation/disaggregation has recently been employed to construct novel and promising photoluminescence (PL)-based sensing and recognition systems. The sensing systems were capable of substantially enhancing the sensitivity, relying on cooperative interactions occurring in the assembly/disassembly processes (mostly operating in emission turned-on or emission-enhanced mode). This review focuses mainly on recent advances in the new emerging PL-based sensing platforms, based on manipulating the behaviours of supramolecular aggregation/disaggregation, including aggregation-induced emission (AIE), metallophilic interactions-related sensing (metallophilic interactions-induced aggregation/disaggregation), metal coordination polymers-related sensing, and other sensing systems involving supramolecular aggregation/disaggregation. In particular, those sensing systems developed by scientists in China are summarized and highlighted.

Highly selective and sensitive recognition of histidine based on the oxidase-like activity of Cu2+ ions

Developing simple, highly sensitive and selective sensing systems for histidine (His) is important due to its biological significance. In this report, Cu2+ ions serving as the oxidase mimics towards O-phenylenediamine (OPD) were investigated in detail. Experimental results revealed that the oxidase-like activity of Cu2+ ions is substantially higher than that of Cu/CuO nanoparticles. On the basis of these findings, a simple, highly sensitive and selective PL sensing platform for His could be developed, with a limit of detection (LOD) as low as 0.33 μM. Furthermore, experiments of His recovery in human urine samples were successfully conducted by employing the established sensing system with satisfactory results.

A highly sensitive multi-catalytic sensing system for organophosphorus and organochlorine pesticides based on the peroxidase-like activity of ferric ions

Developing rapid, efficient and highly sensitive sensing systems for organophosphorus (OPs) and organochlorine pesticides is important due to their potential damage to human health. Considering that Fe3+ ions were recently found to have much higher peroxidase-like activity than that of Fe3O4 magnetic nanoparticles, in this work, a novel and highly sensitive multi-catalytic sensing system has been successfully developed for OPs and organochlorine pesticides, on the basis of the color reaction of 3,3′,5,5′-tetramethyl benzidine (TMB) driven by Fe3+ ions, together with two enzymatic catalytic systems of acetylcholinesterase (AChE) and choline oxidase (CHO). Sub nM level limits of detection could be achieved for four tested OPs and organochlorine pesticides. Furthermore, several fruit/vegetable samples were successfully employed for evaluating this established sensing system.

High-power laser-driven phosphor-in-glass for excellently high conversion efficiency white light generation for special illumination or display backlighting

High-power and high-brightness solid state laser lighting sources, fabricated with high-power blue laser diodes (LDs) and yellow-emitting phosphor converters, constitute a pioneering lighting technology for specialized lighting. Because of the high radiation flux and thermal stress produced by high-power blue LDs, there is an urgent need for a light converter with excellent heat-resistance and thermal stability. In this work, YAG:Ce phosphor-in-glass (PiG), prepared by embedding YAG:Ce phosphor in glass matrix, was developed. Because of the good chemical stability between the glass matrix and the phosphor as well as high refractive index of 1.84 of the glass matrix, the internal quantum efficiency of YAG:Ce-PiG material can reach up to 78.9% under 445 nm blue laser excitation. In comparison with reported papers, the content of the YAG phosphor in this PiG can reach up to 29 wt%, thus it can get more brightness when excited by higher LD power. Besides, systematic research on the thermal effect to the material and its luminescent properties when excited by a high-power blue LD is done in detail. Compared with traditional commercial phosphor-in-silicone (PiS) light converters, PiG can withstand higher blue LD power and maintain a higher luminescent intensity. By virtue of its better heat-resistance performance under exposure to high-power blue LD, the developed PiG light converter material is an ideal choice to replace traditional commercial PiS in high brightness lighting sources.