Organosiloxane and Polyhedral Oligomeric Silsesquioxanes Compounds as Chemiluminescent Molecular Probes for Direct Monitoring Hydroxyl Radicals

Online chemiluminescence determination of the hydroxyl radical using coumarin as a probe

The hydroxyl radical (˙OH) is one of the strongest oxidizing species, which can react with a variety of organic and inorganic chemicals. Although ˙OH is widely used for degradation of environmental pollutants, detection of ˙OH remains a major challenge due to its high reactivity and short lifetime, especially online detection. In this study, a novel method for online detection of ˙OH by flow oxidization chemiluminescence (F-OCL) using coumarin as a probe was established. The concentrations of ˙OH determined by this new method were consistent with those determined by HPLC analysis. Because the new method has a short response speed, it was successfully used to quantify the dynamic change of ˙OH in the TiO2 photocatalytic process and Fenton reaction in real time. Furthermore, a combination of two chemiluminescence systems was developed to track the dynamics of ˙OH and hydrogen peroxide (H2O2) in homogeneous or heterogeneous Fenton reactions occurring in soil slurry. The proposed method and strategy have good application potential in online ROS monitoring of both natural and engineered systems.

New Perylene-Based Chemiluminescent Polymer Nanoparticles for Highly Selective Detection of the Superoxide Anion In Vivo

The superoxide anion (O2•-) is one of the primary reactive oxygen species in biological systems. Developing a determination system for O2•- in vivo has attracted much attention thanks to its complex biological function. Herein, we proposed a new perylene-based chemiluminescence (CL) probe, the SH-PDI polymer, which was capable of generating strong CL signals with O2•- in comparison with other ROS. The CL mechanism involved was proposed to be a kind of oxidation reaction induced by the breakage of the S-S and S-H bonds into sulfoxide bonds by O2•-. Subsequently, a nanoprecipitation method was introduced, using cumene-terminated poly(styrene-co-maleic anhydride) as the amphiphilic agent, to obtain water-soluble nanoparticles, SPPS NPs, which exhibited not only stronger CL intensity but also higher selectivity toward O2•- than the SH-PDI polymer. Moreover, the CL wavelength of the SPPS-O2•- system was found to be located at 580 and 710 nm, which was conducive to CL imaging. By virtue of these advantages, SPPS NPs were utilized to evaluate the O2•- level in vitro in the range of 0.25-60 μM at pH 7.0, with a detection limit of 8.2 × 10-8 M (S/N = 3). Moreover, SPPS NPs were also capable of imaging O2•- in an LPS-induced acute inflammation mice model and drug-induced acute kidney injury (AKI).

Organosilicon Fluorescent Materials

In the past few decades, organosilicon fluorescent materials have attracted great attention in the field of fluorescent materials not only due to their abundant and flexible structures, but also because of their intriguing fluorescence properties, distinct from silicon-free fluorescent materials. Considering their unique properties, they have found broad application prospects in the fields of chemosensor, bioimaging, light-emitting diodes, etc. However, a comprehensive review focusing on this field, from the perspective of their catalogs and applications, is still absent. In this review, organosilicon fluorescent materials are classified into two main types, organosilicon small molecules and polymers. The former includes fluorescent aryl silanes and siloxanes, and the latter are mainly fluorescent polysiloxanes. Their synthesis and applications are summarized. In particular, the function of silicon atoms in fluorescent materials is introduced. Finally, the development trend of organosilicon fluorescent materials is prospected.

A Novel Chemiluminescent Method for Efficient Evaluation of Heterogeneous Fenton Catalysts Using Cigarette Tar

The evaluation of the catalytic capacity of catalysts is indispensable research, as catalytic capacity is a crucial factor to dictate the efficiency of heterogeneous Fenton catalysis. Herein, we obtained cigarette tar-methanol extracts (CTME) by applying methanol to cigarette tar and found that CTME could cause CL reactions with Fe²⁺/H₂O₂ systems in acidic, neutral, and alkaline media. The CL spectrum experiment indicated that the emission wavelengths of the CTME CL reaction with Fe²⁺/H₂O₂ systems were about 490 nm, 535 nm, and 590 nm. Quenching experiments confirmed that hydroxyl radicals (•OH) were responsible for the CL reaction for CTME. Then the CL property of CTME was applied in-situ to rapidly determine the amounts of •OH in tetrachloro-1,4-benzoquinone (TCBQ)/H₂O₂ system in acidic, neutral and alkaline media, and the CL intensities correlated the best (R² = 0.99) with TCBQ concentrations. To demonstrate the utility of the CTME CL method, the catalytic capacity of different types and concentrations of catalysts in heterogeneous Fenton catalysis were examined. It was found that the order of CL intensities was consistent with the order of degradation efficiencies of Rhodamine B, indicating that this method could distinguish the catalytic capacity of catalysts. The CTME CL method could provide a convenient tool for the efficient evaluation of the catalytic capacity of catalysts in heterogeneous Fenton catalysis.

Co3O4 modified polymeric carbon nitride for external light-free chlorine activating degradation of organic pollutants

Advanced oxidation processes (AOPs) activated by chlorine have emerged as a green and efficient strategy for water treatment and have attracted widespread attention. However, most of them require continuous UV radiation during the degradation reaction, which increases the cost and is not conducive to practical application, in some ways. Hererin we proposed an external light-free chlorine activation methodology for the removal of organic pollutants with the assistance of the intrinsic chemiluminescence (CL) in the system. A very interesting phenomenon, 20-fold enhanced CL of Co₃O₄ nanoparticles modified polymeric carbon nitride (PCN/Co₃O₄) was observed in the presence of hypochlorous acid (HClO), compared with the pristine PCN nanosheets. Without ultraviolet (UV), even any other light-emitting devices, the strong intrinsic CL in the PCN/Co₃O₄-HClO system was found to be conducive to chlorine activation degradation of organic pollutants. The inner connection between the CL of the PCN/Co₃O₄-HClO system and the chlorine-based AOPs was further explored.

Transient Chemiluminescence Assay for Real-Time Monitoring of the Processes of SO32--Based Advanced Oxidation Reactions

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.

Advances in chemiluminescence and electrogenerated chemiluminescence based on silicon nanomaterials

Since 1950, when chemiluminescence (CL) of siloxane upon treatment with strong oxidants was discovered by Kurtz, many silicon-based nanomaterials with different elements, specific molecules, shapes and sizes have been developed as light emitters, energy acceptors, and catalyzers to provide valuable CL and electrogenerated CL (ECL) detection platforms in analytical chemistry fields. This review mainly focuses on the recent development of their mechanisms and sensing methodologies for small molecules, free radicals, ion, enzyme, protein, DNA, cancer cells, and metabolites based on specific reactions such as aptamer sensing and enzymatic reaction. Additionally, the future trend is discussed.

Off/On Amino-Functionalized Polyhedral Oligomeric Silsesquioxane-Perylene Diimides Based Hydrophilic Luminescent Polymer for Aqueous Fluoride Ion Detection

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.

Efficient generation of sulfate radicals in Fe(ii)/S(iv) system induced by WS2 nanosheets and examined by its intrinsic chemiluminescence

In this study, the generation of more SO₄˙⁻ and strong intrinsic chemiluminescence (CL) were achieved through activating sulfite (SO₃²⁻) with ferrous ions (Fe²⁺) on 5 nm-thick WS₂ nanosheets.