Boosting plasmon-enhanced electrochemistry by in situ surface cleaning of plasmonic nanocatalysts.

The application of surface plasmons in heterogeneous catalysis has attracted widespread attention due to their promising potential for harvesting solar energy. The effect of surface adsorbates on catalysts has been well documented in many traditional reactions; nonetheless, their role in plasmonic catalysis has been rarely studied. In this study, an in situ electrochemical surface cleaning strategy is developed and the influence of surface adsorbates on plasmon-enhanced electrochemistry is investigated. Taking Au nanocubes as an example, plasmonic catalysts with clean surfaces are obtained by Cu2O coating and in situ electrochemical etching. During this process, the surface adsorbates of Au nanocubes are removed together with the Cu2O shells. The Au nanocubes with clean surfaces exhibit remarkable performance in plasmon-enhanced electrooxidation of glucose and an enhancement of 445% is demonstrated. The Au NCs with clean surfaces can not only provide more active sites but also avoid halides as hole scavengers, and therefore, the efficient utilization of hot holes by plasmonic excitation is achieved. This process is also generalized to other molecules and applied in electrochemical sensing with high sensitivity. These results highlight the critical role of surface adsorbates in plasmonic catalysis and may forward the design of efficient plasmonic catalysts for plasmon-enhanced electrochemistry.

Colorimetric and fluorescence dual-mode pH sensor based on nitrogen-doped carbon dots and its diverse applications.

A dual-mode pH sensor based on nitrogen-doped carbon dots (N-CDs) with the source of o-phenylenediamine and tryptophan has been constructed. Under the stimulation of pH, the N-CDs exhibited prominent both color and fluorescence changes, leading to the rarely discovered colorimetric and fluorescent dual-readouts for the evaluation of pH. The mathematic relationship was established between pH and fluorescence intensity of N-CDs, and between pH and the UV-Vis absorbance ratio at 630 nm and 488 nm of N-CDs, respectively, over a quite broad pH range of 2.2 to 12.0. Multiple techniques are used to explore the dual-mode pH-responsive mechanism, and the preliminary explanation is put forward. The experimental results show that the N-CDs have visualized pH sensing applicability for actual samples, including various water samples and HeLa cell. Furthermore, the N-CD ink is developed for successful information encryption and anti-counterfeiting. This work might provide valuable insights into the sensing mechanism of CDs, and the application potential of CDs in broader fields.

Common materials, extraordinary behavior: An ultrasensitive and enantioselective strategy for D-Tryptophan recognition based on electrochemical Au@p-L-cysteine chiral interface.

The poly-L-cysteine modified Au nanoparticles (Au@p-L-Cys) were constructed on electrode surface as a highly efficient chiral interface for tryptophan (Trp) enantiomers recognition via one step electropolymerization. With the aid of Cu2+, L-Cys residues and D-Trp target formed a sandwich complex D-Trp-Cu2+-L-Cys, while L-Trp was unable to form such complex due to the steric hindrance provided by the chiral interface, which was confirmed by the electrochemical and SEM results. With the introduction of ferricyanide probe, D-Trp produced significant current decrease while L-Trp produced a slight current increase, which implied the successful enantioselective recognition of Trp enantiomers (specifically D-Trp) in the true sense. This novel sensor showed a surprisingly wide linear range toward D-Trp of 6 × 10-7 M to 1 × 10-2 M, with a detection limit as low as 75 nM (S/N = 3). Moreover, the exclusive enantioselectivity toward D-Trp was discovered since other amino acids showed negligible interference to detection of D-Trp. The recovery of D-Trp in human serum was between 91.30 and 109.3%, which further verified the satisfying specificity and practicality of the proposed strategy. The coordination thermodynamics by UV-Vis spectroscopy and DFT simulation were also used to investigate the enantioselective mechanism. These results highlight the great potential of using Au@p-L-Cys to construct chiral interface for enantiomers recognition and hold the promise of practical application of electrochemical chiral sensors in fields like pharmaceutics and bioanalysis.