Yu Han,Wenxing Wang,Penglin Jiang,Yucong Yan,Hui Zhang,Deren Yang
Au nanorings are of particular interest in catalysis owing to their fascinating properties, however, it still remains a tremendous challenge to generate such hollow nanostructures with small size. Here, we report the synthesis of Au nanorings with an outer diameter of less than 20 nm by a seed-mediated approach with Pd nanoplates as seeds in the presence of Ag+ ions. The incorporation of Ag+ ions substantially slows down the reduction rate of the Au precursor through an underpotential deposition (UPD) process, leading to the formation of small Au nanoparticles. These small Au nanoparticles then coalesced into nanorings on small Pd nanoplates. The outer diameter of the Au nanorings is tuned by varying the size of the Pd nanoplates. The smallest Au nanorings are evaluated as catalysts towards the hydrogenation of 4-nitrophenol, showing substantially enhanced catalytic activity relative to the Au nanoparticles with the same size. This enhancement in the catalytic activity can be attributed to the unique structural features including the large specific surface areas, convenient accessibility of both interior and exterior surfaces for the reactants, and existence of highly active sites in the interior part.
Yan Bingsong,Liu Wendong,Duan Guangbin,Ni Pengjuan,Jiang Yuanyuan,Zhang Chenghui,Wang Bo,Lu Yizhong,Chen Chuanxia
A convenient and sensitive colorimetric assay for acetylcholinesterase (AChE) and its inhibitor has been designed based on the oxidase-like activity of {100}-faceted Pd square nanoplates which are grown in situ on reduced graphene oxide (PdSP@rGO). PdSP@rGO can effectively catalyze the oxidation of colorless 3,3′,5,5′-tetramethylbenzidine (TMB) without the assistance of H 2 O 2 to generate blue oxidized TMB (oxTMB) with a characteristic absorption peak at 652 nm. In the presence of AChE, acetylthiocholine (ATCh), a typical AChE substrate, is hydrolyzed to thiocholine (TCh). The generated TCh can effectively inhibit the PdSP@rGO-triggered chromogenic reaction of TMB via cheating with Pd, resulting in color fading and decrease in absorbance. Thus, a sensitive probe for AChE activity is constructed with a working range of 0.25–5 mU mL −1 and a limit of detection (LOD) of 0.0625 mU mL −1 . Furthermore, because of the inhibition effect of tacrine on AChE, tacrine is also detected through the colorimetric AChE assay system within the concentrations range 0.025–0.4 μM with a LOD of 0.00229 μM. Hence, a rapid and facile colorimetric procedure to sensitively detect AChE and its inhibitor can be anticipated through modulating the oxidase-like activity of PdSP@rGO. Graphical abstract
Colorimetric method for detection of AChE and its inhibitor is established by modulating the oxidase mimetic activity of {100}-faceted Pd square nanoplates on reduced graphene oxide (PdSP@rGO).
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