Metal-organic framework as a multi-component sensor for detection of Fe^(3+),ascorbic acid and acid phosphatase

In this research,a hydroxyl group functionalized metal-organic framework(MOF),UiO-66-(OH)_(2),was synthesized as a "on-off-on" fluore scent switching nanoprobe for highly sensitive and selective detection of Fe^(3+),ascorbic acid(AA) and acid phosphatase(ACP).UiO-66-(OH)_(2) emits yellow-green light under ultraviolet light,when Fe^(3+) was added,Fe^(3+) was chelated with hydroxyl group,the electrons in the excited state S_1 of the MOF transferred to the half-filled 3 d orbits of Fe^(3+),resulting in fluorescence quenching because of the nonradiative electron/hole recombination annihilation.AA could reduce Fe^(3+) to Fe^(2+),which can destroy the electron transfer between UiO-66-(OH)_(2) and Fe^(3+) after AA adding,resulted in nonoccurrence of the nonradiative electron transfer,leading to the recovery of UiO-66-(OH)_(2) fluorescence intensity.The probe can also be used to detect ACP based on the enzymolysis of 2-phospho-L-ascorbic acid(AAP) to produce AA.Benefitting from the hydroxyl group and the characteristics of UiO-66,including the high porosity and large surface area,the developed UiO-66-(OH)_(2) showed extensive advantages as a fluorescent probe for detection of multi-component,such as high sensitivity and selectivity,colorimetric detection,fast response kinetics and easy to operate,economical and secure.This is the first time to use active group functionalized MOFs as a multicomponent sensor for these three substances detection.

Colorimetric-assisted photoelectrochemical sensing for dual-model detection of sialic acid via oxidation-power mediator integration

Development of sensitive and accurate methods for sialic acid(SA) determination is of great significance in early cancer diagnosis.Here,a colorimetric-assisted Photoelectrochemical(PEC) sensor was constructed for SA detection based on the two pairs of cis-diol groups in SA molecule.With the specific recognition of SA via the two pairs of cis-diol groups,the prepared gold-modified Bi_(2)S_(3)(AuNPs@Bi_(2)S_(3)) and metal organic framework(Au@PCN-224) were introduced to the electrode and formed a sandwich structure.Based on the properties of inert electroconductivity and nanozyme of the PCN-224,dual-readout of photocurrent and visualization was achieved with the presence of 3',3',5',5'-tetramethylbenzidine(TMB).Moreover,to intensify the visualization signal,Ce^(3+) was employed as the mediator to boost the catalysis capability by transferring energy from PCN-224 surface to the whole system.With the unique SA recognition and the mediation of Ce^(3+),both the photocurrent and the visualization signals sensitively responded with the SA concentration linearly.The present method showed greatly high sensitivity,selectivity and accuracy for SA detection with a limit of detection of 1.44μmol/L and a wide linear range of 5-1000μmol/L.This method provided a new promising platform for SA detection and a potential strategy for design of novel biosensors with dual-model readout.