CoSe2 hollow microspheres with superior oxidase-like activity for ultrasensitive colorimetric biosensing

As one of the transition metal dichalcogenide, CoSe2 has received much attention because of its superior physicochemical properties. In this work, a self-templated approach was proposed for constructing CoSe2 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 CoSe2 microspheres. The obtained CoSe2 microspheres retain the cavity of the ZIF-67 and massive uniformly dispersed CoSe2 nanoparticles are embedded throughout carbon walls. The hollow interior and porous structure of CoSe2 microspheres provide an enhanced surface-volume ratio and short charge/mass transfer distance. The CoSe2 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, 1O2 and O2•− radicals coexist in the TMB-CoSe2 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.