Defect engineering is an effective strategy to improve the catalytic activity of metal oxides, and quantitative characterization of surface defects is thus vital to the understanding and application of metal oxide catalysts. Herein, we found that ZnO nanoparticles with oxygen vacancy could trigger the luminol−H 2 O 2 system to emit a strong chemiluminescence (CL), and the CL intensity was strongly dependent on the oxygen vacancy of the ZnO nanoparticles. The mechanism of this CL reaction was discussed by means of the electron-spin resonance spectrum, X-ray photoelectron spectrum (XPS), and CL spectrum. The oxygen vacancy-dependent CL was attributed to the ability of the oxygen vacancy to readily adsorb and further dissociate H 2 O 2 into active • OH radicals. Taking advantage of this oxygen vacancy-dependent CL, we presented one method for quantifying the oxygen defects in ZnO. Compared with the current evaluation techniques (XPS and Raman spectroscopy), this CL method is rapid, low-cost, and easy to operate. This work introduces the CL technique into the field of material structure−property evaluation, and provides a new approach for exploring the defect function in ZnO defect engineering.
Most
of the known chemiluminescence (CL) systems are flash-type,
whereas a CL system with long-lasting and strong emission is very
favorable for accurate CL quantitative analysis and imaging assays.
In this work, we found that the oxidized g-C3N4 (g-CNOX) could trigger luminol-H2O2 to produce a long-lasting and intense CL emission. The CL emission
lasted for over 10 min and could be observed by the naked eye in a
dark room. By means of a CL spectrum, X-ray photoelectron spectra,
and electron spin resonance spectra, the possible mechanism of this
CL reaction was proposed. This strong and long-duration CL emission
was attributed to the high catalytic activity of g-CNOX nanosheets and continuous generation of reactive oxygen species
from H2O2 on g-CNOX surface. Taking
full advantage of the long-lasting CL property of this system, we
proposed one “non-in-situ mixing” mode of CL measurement.
Compared with the traditional “in-situ mixing” CL measurement
mode, this measurement mode was convenient to operate and had good
reproducibility. This work not only provides a long-lasting CL reaction
but also deepens the understanding of the structure and properties
of g-C3N4 material.
The upregulation of microRNA (miRNA) is highly related with some kinds of tumor, such as breast, prostate, lung, and pancreatic cancers. Therefore, for an important tumor biomarker, the point-of-care testing (POCT) of miRNA is of significant importance and is in great demand for disease diagnosis and clinical prognoses. Herein, a POCT assay for miRNA detection was developed via a portable pressure meter. Two hairpin DNA probes, H1 and H2, were ingeniously designed and functionalized with magnetic beads (MBs) and platinum nanoparticles (PtNPs), respectively, to form MBs-H1 and PtNPs-H2 complexes. In the presence of target microRNA 21 (miR-21), the cyclic strand displacement reaction (SDR) between MBs-H1 and PtNPs-H2 was triggered to continuously form the MBs-H1/PtNPs-H2 duplex. Owing to the amplification of cyclic SDR, numerous PtNPs were enriched onto the surface of MBs to catalytically decompose HO for the generation of much O. The gas pressure value has a linear relationship with the logarithmic value of miR-21 concentration in the range of 10 fM to 10 pM. The limit of detection is 7.6 fM, which is more sensitive than that in a number of previous reports. Hairpin DNA probes and magnetic separation highly ensured the specificity and reliability. Single-base mutation was easily discriminated, and the detection of miR-21 in the serum sample achieved satisfactory result. Therefore, it offers a reliable POCT strategy for the detection of miRNA, which is of great theoretical and practical importance for POCT clinical diagnostics.
Discovering efficient
antibacterial materials is crucial in the
area of increasing drug resistance. Herein, we synthesized carbon
dots (C-dots) with superior antibacterial activity through a simple
one-step hydrothermal method. In this method, p-phenylenediamine
serves as not only the carbon source but also the origin for the functional
group anchored on the obtained C-dots. The antibacterial activity
of the obtained C-dots was tested against Staphylococcus
aureus and Escherichia coli. The minimum bactericidal concentrations of the synthesized C-dots
against S. aureus and E. coli were 2 and 30 μg/mL, respectively,
which are lower than that of previously reported C-dots. The antibacterial
mechanism was investigated, and the results indicated that a large
number of −NH3
+ groups on the C-dots’
surface enhanced their antibacterial activity. Besides, the C-dots
exhibited negligible cytotoxicity.
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