Juan Chai,Luohao Yuan,Shiwei Wang,Tong Li,Mingxue Wu,Zhiwei Huang,Hongfeng Yin
Three metal–organic frameworks {[Cu6(L1)4(DMF)(H2O)2·5H2O]}n (1), {Cu3(L1)2(phen)2(H2O)}n (2) and {[Cu8(μ3-OH)3(L2)4(NO3)(H2O)5]·3H2O}n (3) utilizing nitrogen-containing heterocyclic carboxylate bifunctional ligands (L1 = 5-(4-carboxypyridin-3-yl)isophthalic acid and L2 = 2-(5-carboxypyridin-2-yl)terephthalic acid) were self-assembled hydrothermally and characterized. MOFs 1–3 possess 3D networks which consist of three different types of Cu clusters {Cu2O2(OCO)4}, {Cu2O2N4(OCO)2} and {Cu4O10(OCO)4}, respectively. MOFs 1–3 efficiently catalyze the oxidation of cycloalkanes under mild conditions. Besides, the synthesized MOFs 1–3 exhibited high peroxidase-like activity and could be utilized to catalyze the oxidation of 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid ammonium salt) (ABTS) to produce green color in the presence of hydrogen peroxide (H2O2). The steady-state kinetics experiments of the oxidation of ABTS catalyzed by MOFs 1–3 were carried out, and the kinetic parameters were obtained. The results indicated that the affinity of MOFs 1–3 towards H2O2 and ABTS was higher than that of the natural horseradish peroxidase (HRP). The as-prepared MOF 1 can be applied for the colorimetric detection of H2O2 with a wide linear range of 0.5 to 200 μM and a limit of detection (LOD) of 0.097 μM. Therefore, the novel Cu-MOFs could be regarded as promising artificial enzyme mimics in catalysis, sensors and environment analysis.
Limei Yang,Ye Liu,Rongxue Wang,Linqian Hou,Yaling Yang
A K-doped carboxylated polydopamine (PDA) modification of the g-C3N4 (K-g-C3N4@PDA) nanozyme was effectively performed by one-step potassium salt-assisted thermal copolymerization and hydrothermal strategies. K-g-C3N4@PDA showed excellent peroxidase (POD)-like activity, and ferric ammonium citrate (FAC) efficiently promoted the generation of hydroxyl radicals (˙OH). Furthermore, K-g-C3N4@PDA oxidized 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) in the presence of H2O2 to produce a blue-green product, and FAC boosted the POD-like activity with an exceptional linear relationship and low detection limit (0.018 μg mL−1). Importantly, a recovery rate of 94.09–105.17% was attained when the developed method was effectively used to assess FAC in culinary salt samples using a spiking procedure.
An amplified colorimetric detection of Hg 2+ is proposed by combining T–Hg 2+ –T base pairs and hybridization chain reaction (HCR). Two hairpins consisting of three-fourths and one-fourth of the horseradish peroxidase (HRP)-mimicking DNAzyme in inactive configuration are used as functional elements. In the presence of Hg 2+ , one of the hairpins is opened by an assistant probe with the help of T–Hg 2+ –T base pairs and this triggers an autonomous cross-opening of the two hairpins using the strand displacement principle, resulting in the formation of DNA nanowires consisting of numerous reunited Q-quadruplex DNAzyme units. The resulting catalytically active hemin/G-quadruplex HRP-mimicking DNAzymes catalyze the oxidation of ABTS 2− by H 2 O 2 into a green-colored cationic radical ABTS •+ for the colorimetric readout. This “turn-on” sensing system enables the high sensitive and selective detection of aqueous Hg 2+ with a detection limit of 9.7 pM.
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