Mediatorless Glucose Biosensor and Direct Electron
Transfer Type Glucose/Air Biofuel Cell Enabled with Carbon Nanodots
- Publication date
- Publisher
Abstract
Utilization
of carbon nanodots (CNDs), newcomers to the world of
carbonaceous nanomaterials, in the electrochemistry realm has rarely
been reported so far. In this study, CNDs were used as immobilization
supports and electron carriers to promote direct electron transfer
(DET) reactions of glucose oxidase (GOx) and bilirubin oxidase (BOD).
At the CNDs electrode entrapped with GOx, a high rate constant (<i>k</i><sub>s</sub>) of 6.28 ± 0.05 s<sup>–1</sup> for fast DET and an apparent Michaelis–Menten constant (<i>K</i><sub>M</sub><sup>app</sup>) as low as 0.85 ± 0.03
mM for affinity to glucose were found. By taking advantage of its
excellent direct bioelectrocatalytic performances to glucose oxidation,
a DET-based biosensor for glucose detection ranging from 0 to 0.64
mM with a high sensitivity of 6.1 μA mM<sup>–1</sup> and
a limit of detection (LOD) of 1.07 ± 0.03 μM (S/N = 3)
was proposed. Additionally, the promoted DET of BOD immobilized on
CNDs was also observed and effectively catalyzed the reduction of
oxygen to water at the onset potential of +0.51 V (vs Ag/AgCl). On
the basis of the facilitated DET of these two enzymes at CNDs electrodes,
a mediator-free DET-type glucose/air enzymatic biofuel cell (BFC),
in which CNDs electrodes entrapped with GOx and BOD were employed
for oxidizing glucose at the bioanode and reducing oxygen at the biocathode,
respectively, was successfully fabricated. The constructed BFC displayed
an open-circuit voltage (OCV) as high as 0.93 V and a maximum power
density of 40.8 μW cm<sup>–2</sup> at 0.41 V. These important
features of CNDs have implied to be promising materials for immobilizing
enzymes and efficient platforms for elaborating bioelectrochemical
devices such as biosensors and BFCs