The hydroxyl radical (·OH) is
a strong oxidizing agent in situ generated in advanced
oxidation processes (AOPs)
and crucial for assessing the performances of AOPs toward organic
contaminants’ degradation. Herein, we developed a specific
luminescent probe, APDI (N′ N′-di(propylethylenediamine)-perylene-3,4,9,10-tetracarboxylic
diimide), to selectively detect ·OH among diverse reactive oxygen
species and other radicals. Based on the transient chemiluminescence
(TCL) spectra, the in situ concentration profile
of ·OH within 0.01 s interval time in classical Fenton reactions
and four kinds of SO3
2–-based AOPs was
obtained, which provides insights into the high dynamic processes
of the whole ·OH generation and consumption processes. Besides,
compared with acidic conditions, reduced degradation efficiencies
in Fe2+–SO3
2– and Fe2+–SO3
2––H2O2 systems were found under neutral conditions. The complete
depletion of active free radicals due to SO2
–̇ radicals generated from Fe2+ and SO3
2– should account most for decreased degradation
efficiencies evidenced by a new SO2* TCL signal discovered
in the TCL spectra. In addition, similar phenomena have also been
found in other M(n–1)+–SO3
2–-related AOPs. As SO3
2– and HSO3
– often exist naturally in
wastewater, more efforts are needed to improve the performance of
Fe2+–H2O2 systems. This discovery
has important significance for organic contaminant degradation in
a natural environment.
Despite the tremendous progress in the research of luminescent probes for reactive oxygen species (ROS), designing luminescent ROS probes with high sensitivity for the individual ROS is still retarded because of their high reactivity and the rapid and complex interconversion reactions among them. Herein, organosiloxane and polyhedral oligomeric silsesquioxanes (POSS) compounds are designed as a novel class of luminescent molecular probes to produce extraordinary chemiluminescence (CL) based on the specific electrophilic attack of • OH. No CL signal can be obtained by the other ROS and strong oxidants. AEAP-POSS formed by hydrolytical condensation of 3-(2-aminoethylamino)propyl]trimethoxysilane (AEAPTMS) is constructed to covalently link a dye molecular, perylene diimide derivative (PDI), and an intramolecular chemiluminescence resonance energy transfer (CRET) system is obtained to realize the red shift of CL wavelength and enhanced CL intensity. This probe based on CRET is applied to monitor inherent • OH in ambient particular matter (PM 2.5 and PM 10 ). Density functional theory (DFT), ion chromatograph, X-ray photoelectron spectroscopy (XPS), particle size analysis, and fluorescence spectrum (FL) are applied to study the CL mechanism. These studies discover that electronically carbonyl CH 3 CO • is the CL emitter, and the silicon−oxygen skeleton in the organosiloxane and POSS compounds plays the key role in undergoing chemiluminescence (CL) reaction.
Fluoride ion detection
in water focuses much attention due to the
serious healthy impact in human pathologies. For fluoride recognition,
the chemical affinity between fluoride and silicon has been developed
on the basis of the degradation mechanism. However, most fluorescent
probes are the “turn off” type due to the aggregation
of the degradational products. Herein, we first developed an “off–on”
hydrophilic luminescent polymer composed of amino-functionalized polyhedral
oligomeric silsesquioxane (AE-POSS) and perylene diimides (PDIs) for
fluoride ion in water. The AE-PDI polymer was “turned off”
because of the photoinduced electron transfer (PET) between PDI and
AE-POSS, and then after reaction with F–, the fluorescent
emission could “turn on” obviously because the PET was
blocked by the degradation of the cage. The PET from amino-POSS to
PDI was proved by FL spectrum and energies of HOMO and LUMO orbitals. 29Si, 19F NMR, and 1H NMR titration,
XRD, FTIR, size analysis, and ion chromatography were applied to demonstrate
the degradation mechanism. These results indicated that the higher
quantum yield could be obtained by introducing the amide group in
the PDI and the products of AE-PDI polymer might exist in the form
of complex compounds with partial condensation of organosiloxane.
With high selectivity and sensitivity (detection limit of 16.2 ppb),
this probe was successfully applied for F– detection
in actual water samples.
Photocatalytic production of reactive oxygen species from O 2 at the interface of the photocatalyst is significant to convert luminous energy like daylight into chemical energy and could be momentous for a reactive oxygen species-based chemiluminescence system. Herein, we synthesized a novel K + ion-doped tri-s-triazine/ triazine mixed carbon nitride (MCN), in which K + ions were intercalated into the layers in a bridging manner. After a mild daylight treatment for 30 min, the MCN suspension could produce long-lifetime reactive oxygen species and further directly produce intense and stable chemiluminescence emission in the presence of luminol. In particular, the chemiluminescence intensity was 780 times that of H 2 O 2 −luminol, and MCN could be recycled several times in the chemiluminescence system. The mechanism results revealed a large number of reactive oxygen species that were generated from O 2 on the surface of MCN through a temperate photocatalytic process. In the theoretical calculation, the charge density of N interacting with K + ions was significantly more negative than that at the corresponding position in graphitic carbon nitride, which was beneficial to the adsorption and activation of oxygen, and the narrower band gap suggested that the doping of K + ions was conducive to the intramolecular charge transfer interaction. Then, the long-lifetime reactive oxygen species triggered the conversion of luminol into an excited-state intermediate, which further transferred energy to MCN, producing strong chemiluminescence emission. The K + ion-doped MCN might conduct as an efficient photocatalyst for reactive oxygen species generation, recyclable catalysts, and luminophores in the photoinduced chemiluminescence system.
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