Oxygen vacancy is known to act as a reactive center in
oxides to
produce radicals. Currently, X-ray photoelectron spectra (XPS) become
a unique spectral tool for analyzing oxygen vacancy based on the differences
in atomic number ratios between metal ions and lattice oxygen. In
this work, it was found that the superoxide radical (O2
•–)-luminol electrochemiluminescence (ECL)
intensity linearly increases with increasing the oxygen vacancy concentrations
of TiO2 samples coated on the electrodes. An experimental
study of the mechanism demonstrates that an increase in oxygen vacancy
concentrations could lead to an increase in the generation of O2
•–, resulting in an increase in the
O2
•–-related luminol ECL signals.
Accordingly, we have developed a rapid and simple O2
•–-luminol ECL platform to detect oxygen vacancy
in TiO2 samples, based on the relationship between O2
•– generation and oxygen vacancy.
The proposed ECL platform exhibits good reproducibility and stability
through the parallel ECL measurements. Moreover, the feasibility is
verified by analyzing the oxygen vacancy concentrations in different
TiO2 samples with varying the Co, Cr, Fe, and N doping
concentrations. The oxygen vacancy concentrations obtained by the
proposed ECL method could match well with those obtained by conventional
XPS measurements. Our successful construction of the ECL platform
will significantly promote the development of the oxygen vacancy detection
in oxides and deepen the understanding of the relationship between
oxygen vacancy and radicals.
Chemiluminescence (CL) probes for reactive oxygen species (ROS) are commonly based on a redox reaction between a CL reagent and ROS, leading to poor selectivity toward a specific ROS. The energy-matching rules in the chemiluminescence resonance energy transfer (CRET) process between a specific ROS donor and a suitable fluorescence dye acceptor is a promising method for the selective detection of ROS. Nevertheless, higher concentrations of fluorescence dyes can lead to the intractable aggregation-caused quenching effect, decreasing the CRET efficiency. In this report, we fabricated an orderly arranged structure of calcein-sodium dodecyl sulfate (SDS) molecules to improve the CRET efficiency between ONOOH* donor and calcein acceptor. Such orderly arranged calcein-SDS composites can distinguish peroxynitrite (ONOO(-)) from a variety of other ROS owing to the energy matching in the CRET process between ONOOH* donor and calcein acceptor. Under the optimal experimental conditions, ONOO(-) could be assayed in the range of 1.0-20.0 μM, and the detection limit for ONOO(-) [signal-to-noise ratio (S/N) = 3] was 0.3 μM. The proposed strategy has been successfully applied in both detecting ONOO(-) in cancer mouse plasma samples and monitoring the generation of ONOO(-) from 3-morpholinosydnonimine (SIN-1). Recoveries from cancer mouse plasma samples were in the range of 96-105%. The success of this work provides a unique opportunity to develop a CL tool to monitor ONOO(-) with high selectivity in a specific manner. Improvement of selectivity and sensitivity of CL probes holds great promise as a strategy for developing a wide range of probes for various ROS by tuning the types of fluorescence dyes.
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