This review summarizes the recent applications of confocal laser scanning microscopy in materials science.

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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Using a green catalyst of luminol chemiluminescence (CL), Mg-Al-carbonate layered double hydroxides (denoted as Mg-Al-CO(3) LDHs), a novel, sensitive and rapid CL method was developed for the determination of hydrogen peroxide (H(2)O(2)). The corresponding linear regression equation was established in the range of 0.05-10 μM for H(2)O(2). The detection limit (S/N = 3) is 0.02 μM and the relative standard deviation (RSD) for nine repeated measurements of 1.0 μM H(2)O(2) was 2.9%. This proposed method has been successfully applied to detect H(2)O(2) in rainwater samples with good accuracy and precision. The novel methodology is expected to provide a general protocol for the determination of H(2)O(2) as well as for numerous other oxidase-based reactions giving H(2)O(2) as a product (e.g., glucose).

In this study, Mg-Al-carbonate layered double hydroxides (denoted as Mg-Al-CO(3) LDHs) were found to catalyze the chemiluminescence (CL) emission from peroxynitrous acid (ONOOH). The enhanced CL signals resulted from the concentration of peroxynitrite (ONOO(-)) onto the LDHs surface by electrostatic attraction, meaning that ONOO(-) can interact with the intercalated carbonate easily and effectively. Moreover, ascorbic acid can react with ONOO(-), or its decomposition products (e.g., ˙OH and ˙NO(2)), resulting in a decrease in the CL intensity from the Mg-Al-CO(3) LDHs-catalyzed ONOOH reaction. Based on these findings, a sensitive, selective and rapid CL method was developed for the determination of ascorbic acid using Mg-Al-CO(3) LDHs-catalyzed ONOOH as a novel CL system. The CL intensity was proportional to the concentration of ascorbic acid in the range from 5.0 to 5000 nM. The detection limit (S/N = 3) was 0.5 nM and the relative standard deviation (RSD) for nine repeated measurements of 0.1 μM ascorbic acid was 2.6%. This method has been successfully applied to determine ascorbic acid in commercial liquid fruit juices with recoveries of 97-107%. This work is not only of importance for a better understanding of the unique properties of LDHs-catalyzed CL but also of great potential for extensive applications in many fields, such as luminescence devices, bioanalysis, and labeling probes.