CoSe hollow microspheres with superior oxidase-like activity for ultrasensitive colorimetric biosensing.

As one of the transition metal dichalcogenide, CoSe has received much attention because of its superior physicochemical properties. In this work, a self-templated approach was proposed for constructing CoSe hollow microspheres by utilizing ZIF-67 hollow sphere as a template. In the followed selenylation process, selenium vapor reacts with cobalt ion in ZIF-67 to form CoSe microspheres. The obtained CoSe microspheres retain the cavity of the ZIF-67 and massive uniformly dispersed CoSe nanoparticles are embedded throughout carbon walls. The hollow interior and porous structure of CoSe microspheres provide an enhanced surface-volume ratio and short charge/mass transfer distance. The CoSe microspheres show a typical oxidase-like property able to promote 3,3',5,5'-tetramethylbenzidine (TMB) oxidation by dissolved oxygen to produce an intensive color reaction. Reactive oxygen species trials demonstrate that ·OH, O and O radicals coexist in the TMB-CoSe system. Based on its inhibitive role, a rapid and ultrasensitive determination of glutathione was reached, showing four orders of magnitude linear range from 0.005 to 10 μM and a limit of detection of 4.62 nM (S/N = 3). The assay has been successfully used to glutathione determination in practical samples.