In this work, we explore the nonenzymatic detection of
H2O2 using anodic SnO2 nanoporous
channels (NPC)
decorated with CuO quantum dots (QDs). The open-top and crack-free
morphology of SnO2 NPC was obtained by modified anodization.
The samples were characterized using X-ray diffraction (XRD), field
emission scanning electron microscopy (FESEM), energy-dispersive X-ray
analysis (EDAX), high-resolution transmission electron microscopy
(HRTEM), Raman and X-ray photoelectron (XPS) spectroscopy. FESEM
and HRTEM results show that SnO2 has a uniform channel
width and pore size with an average diameter of around 40 nm. XRD,
EDAX, XPS, Raman, and HRTEM measurements confirm the high purity of
anodic SnO2 NPC with successful deposition of CuO QDs.
Pristine (SnO2) and hybrid (SnO2-CuO) electrodes
were used directly as the nonenzymatic H2O2 biosensor.
The hybrid electrode demonstrated an ultrahigh sensitivity of ∼85,250
μA mM–1 cm–2 with an extremely
low limit of detection (0.001 μM), broad linear detection ranges
of 5–95 and 25–450 μM, and a quick response time
(less than 1.9 s) toward H2O2 detection. This
can be attributed to the advanced SnO2 nanoporous structure,
the reduced band gap, and the formation of additional surface sites
as a result of CuO QD decoration. H2O2 measurement
in human blood serum demonstrates high sensitivity, good accuracy,
and excellent selectivity of the fabricated hybrid electrode compared
to the commercially available biosensor. Density
functional theory results indicate that the formation of SnO2-CuO is energetically favorable. H2O2 is strongly
and selectively adsorbed over the SnO2-CuO nanostructure
possessing a large negative adsorption energy (−1.89 eV) and
evinces a significant decrease in the band gap (up to 1.59 eV) of
the hybrid structure. The fabricated biosensor showed the highest
sensitivity, excellent selectivity, good reproducibility, repeatability,
and stability, thus confirming it as a favorable candidate for nonenzymatic
H2O2 sensing and quantification.
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