Jiang-Shan Shen

A ratiometric luminescent sensing of Ag+ ion via in situ formation of coordination polymers

A ratiometric luminescent sensing of Ag(+) ion is developed via the Ag(I)-NCys coordination polymeric luminophore in situ formed in aqueous solution upon mixing Ag(+) ion with the designed fluorescent thiol ligand NCys.

Highly selective iodide-responsive gel–sol state transition in supramolecular hydrogels

We demonstrate for the first time a highly selective anion-responsive reversible gel–sol state transition in a supramolecular hydrogel of Ag(I)-glutathione (GSH) coordination polymers, which allows for facile and selective visual recognition of I−via naked eyes even in a strongly colored and/or fluorescent background. Such a strategy overcomes the drawback of spectral interferences which are often encountered in conventional colorimetric and fluorimetric means. It was rationalized that I− functioned as a depolymerizing agent for the Ag(I)-GSH supramolecular hydrogels. A feasible quantitative assay for I− was established that afforded satisfactory results for simulated wastewater samples. We believe that this strategy can in principle be applicable to other species by following a smart gel–sol state transition in designed supramolecular hydrogel.

Metal-Metal-Interaction-Facilitated Coordination Polymer as a Sensing Ensemble: A Case Study for Cysteine Sensing

A detailed investigation of the absorption and CD signals of Ag(I)-cysteine (Cys) aqueous solutions at buffered or varying pH has allowed us to suggest that coordination polymers are formed upon mixing Ag(I) and Cys bearing a Ag(I)-Cys repeat unit. The formation of the coordination polymers are shown to be facilitated by both the Ag(I)···Ag(I) interaction and the interaction between the side chains in the polymeric backbone. The former allows for an immediate spectral sensing of Cys with enantiomeric discrimination capacity with both high sensitivity and selectivity, and the contribution of the side-chain/side-chain interaction serves to guide extended sensing applications by means of modulating this interaction. With our preliminary data on the corresponding Cu(I)-Cys and Au(I)-Cys systems that exhibited similar spectral signals, we conclude that the M(I)-SR coordination polymers (M = Cu, Ag, or Au) could in general function as spectral sensing ensembles for extended applications. This sensing ensemble involves the formation of coordination polymers with practically no spectral background, thus affording high sensing sensitivity and selectivity.

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.

A photoluminescent nanocrystal-based signaling protocol highly sensitive to nerve agents and highly toxic organophosphate pesticides

A photoluminescent II-VI group semiconductor nanocrystal (NC)-based signaling platform composed of thioglycolic acid capped CdS NCs and acetylcholinesterase-acetylthiocholine enzyme catalytic reaction system was developed that was shown to be highly sensitive to nerve agents and toxic organophosphate pesticides with detection limits down to sub-nM levels. This new sensing protocol does not require troublesome conjugation of biomacromolecules onto the surface of NCs.

Enhanced saccharide sensing based on simple phenylboronic acid receptor by coupling to Suzuki homocoupling reaction.

Substantially enhanced monosaccharide fluorescent sensing in aqueous solutions using a simple phenylboronic acid receptor is achieved by coupling the classic strategy based on saccharide-boronic acid interaction with catalytic Suzuki homocoupling reaction.

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.