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Chlorous acid water (CAW) is a chlorine-based disinfectant approved as a food additive in Japan. CAW is synthesized by the reaction of chloric acid aqueous solution with hydrogen peroxide under acidic conditions. However, in this synthesis method, various ions — such as Na + from NaClO 3 and the conjugate base of the acid used — remain in the solution, hindering the selective detection and decreasing stability of chloroperoxyl radical (ClOO•), a potential key disinfectant species. In this study, we aimed to establish a colorimetric quantification method for ClOO•. We prepared a high-purity ClOO• solution (ClO 2_cx ) by cation exchange and its purity and stability were evaluated using electron spin resonance (ESR) spectroscopy and total chlorine concentration measurements. Furthermore, several colorimetric methods—including DPD, TMB, and DPPH assays—were examined to quantify ClOO•, and their sensitivity and selectivity were comparatively assessed. ClOO• was the sole detectable oxidant in the solution, with a lifetime exceeding 100 h, indicating exceptional stability under ambient conditions. Among the evaluated colorimetric methods, the DPD-based method was found to be suitable for quantifying ClOO•, showing a wide detection range and excellent linearity. This study represents the first report of a colorimetric quantification method for ClOO•. Our findings are expected to be useful for quantitatively discussing the biological efficacy of ClOO• and its reaction mechanisms.

Background This study aimed to verify the effects of whitening agents on the color stability of aligner attachments made from flowable and packable composite resins after staining with coffee and wine. Methods Two composite groups were used for attachment preparation on epoxy resin master models: G-ænial Universal Injectable flowable (Group 1, N = 42) and G-ænial Posterior packable (Group 2, n = 42). Initial staining of samples was performed with coffee and red wine respectively, with a total period of 6 days representing 6 months of consumption. After staining, each main group was randomly divided into 3 groups related to distilled water as the control (Distilled Water (DW), n = 14) and whitening agents (Whitening Oral Rinse (WR), n = 14) (Carbamide Peroxide 22% (CP), n = 14) for a 14-day test period. Before staining (T0), after staining (T1), and after whitening (T2), color measurements were made with Vita Easy Shade V. ΔE 00 formula was used to determine color differences between T0-T1 ( ΔE 001 ) , T1-T2 ( ΔE 002 ) and T0-T2 ( ΔE 003 ) color measurement periods. Also, attachments’ whiteness change before and after whitening procedures was calculated using the Whiteness Index for Dentistry (WI D ) formula considering as ΔWI D1  = WI D (T2) − WI D (T0) and ΔWI D2  = WI D (T2) − WI D (T1). Results After immersion in staining solutions, ΔE 001 values of Group 2 were significantly higher than of values of Group 1 (p < 0.001). In Group 1, ΔWI D2 values in the WR and CP groups were found to be significantly higher than measurements in the DW group (p = 0.049 and p = 0.001). In Group 2, the value of ΔE 002 for subgroup CP was significantly higher than that for DW group (p = 0.023). Also, the ΔE 003 measurement of the WR group was higher than the measurement of the CP group (p < 0.001). In Group 2, the ΔWI D1 measurement of the CP group was lower than the measurements of the DW (p < 0.001) and WR (p = 0.014) groups. According to ΔWI D2 measurement in Group 2, CP measurements were higher than DW (p < 0.001) and WR (p = 0.024) measurements. Statistically significant differences were determined between the composite types for DW, WR, CP whitening types in terms of ΔE 003 and ΔWI D1 measurements and between the composites for CP whitening type in terms of ΔWI D2 measurements (p < 0.05). For all significant differences, measurements for Group 2 were found to be higher than for Group 1. Conclusion The color change of packable composite was more pronounced than that of the flowable composite after staining. Between whitening and staining stages, especially in packable composite group, carbamide peroxide whitening agent significantly effected the color and whiteness of the attachments compared to control distilled water group.

Ce-MOFs with ferrocenedicarboxylic acid ligands (Ce-FcDC) as a bifunctional nanozyme exhibited high peroxidase (POD)-mimicking activity and superoxide dismutase (SOD)-mimicking activity. H 2 O 2 was produced from catalytic hydrolysis of peroxymonosulfate (PMS) using Ce-FcDC as a catalyst. The growth of E. coli and S. aureus were synergistically and more effectively suppressed by PMS in the presence of Ce-FcDC, in comparison with the sole use of PMS or Ce-FcDc. Under the catalysis of Ce-FcDC as the POD-mimicking nanozyme, PMS could be activated by Ce-FcDC to produce SO 4 •− and •OH and H 2 O 2 from the hydrolysis of PMS was further derivatized to O 2 •− and •OH. Ce-FcDC as the SOD-mimicking nanozyme causes O 2 •−  to form H 2 O 2 . The generation of O 2 •− and •OH were confirmed using p-benzoquinone and isopropanol alcohol as the scavengers. The resulted SO 4 •− , O 2 •− , and •OH from combination of PMS with Ce-FcDC as an activator may have key roles for suppressing the growth of E. coli and S. aureus . This strategy could be an effective approach for suppressing the growth and preventing infections or pollutions of some other microbial cells as well. Graphical abstract

Iron-based catalysts with high load content of iron sulfide (FeS) were commonly peroxymonosulfate (PMS) and hydrogen peroxide (H2O2) activators to degrade organic pollutants but limited catalytic efficiency and increased risk of ferrous ion leaching restricted their use. Meanwhile, various biomass materials such as straw, peel, and branch have been extensively prepared into biochar for mechanical support for iron-based catalysts; however, the preparation process of biochar was energy-intensive. In this study, FeS nanoparticles modified rape straw composites (RS–FeS) encapsulated with ethylenediaminetetraacetic acid (RS–EDTA–FeS) were successfully presented by in-situ synthesis method for efficiently activating PMS and H2O2 to degrade oxytetracycline (OTC), which was economical and environmentally friendly. The results showed that the modified rape straw can remove OTC efficiently, and the addition of EDTA also significantly enhanced the stability and the reusability of the catalyst. In addition, EDTA also promoted the activation of H2O2 at neutral pH. The OTC degradation efficiency of the two catalysts by PMS was faster than that of H2O2, but H2O2 had a stronger ability to remove OTC than PMS. The highest OTC removal efficiency of RS–FeS and RS–EDTA–FeS were 87.51 and 81.15%. O2•– and 1O2 were the major reactive oxidative species (ROS) in the PMS system. Furthermore, compared with RS–FeS, the addition of EDTA inhabited the generation of O2•– in the PMS system. Instead, O2•– and •OH were the major ROS in the H2O2 system, but 1O2 was also identified in RS–FeS/H2O2 system. RS–EDTA–FeS showed a trend of rising first and then decreasing in recycle test. Instead, the removal rate of OTC by RS–FeS decreased significantly with the increase in reuse times. In the actual wastewater test, the TOC removal of two catalysts active by H2O2 was better than PMS, which was consistent with the test results of OTC, indicating that the two catalysts have application value in the removal of organic pollutants in actual wastewater. This study directly used plant materials as catalysts and omits the preparation process of biochar, greatly reduces the preparation cost and secondary pollution of catalysts, and provides theoretical support for the deepening of advanced oxidation technology.

Tocopherols, lipid-soluble antioxidants play a crucial role in the antioxidant defense system in higher plants. The antioxidant function of α-tocopherol has been widely studied; however, experimental data on the formation of its oxidation products is missing. In this study, we attempt to provide spectroscopic evidence on the detection of oxidation products of α-tocopherol formed by its interaction with singlet oxygen and lipid peroxyl radical. Singlet oxygen was formed using photosensitizer rose bengal and thylakoid membranes isolated from Arabidopsis thaliana . Singlet oxygen reacts with polyunsaturated fatty acid forming lipid hydroperoxide which is oxidized by ferric iron to lipid peroxyl radical. The addition of singlet oxygen to double bond carbon on the chromanol head of α-tocopherol forms α-tocopherol hydroperoxide detected using fluorescent probe swallow-tailed perylene derivative. The decomposition of α-tocopherol hydroperoxide forms α-tocopherol quinone. The hydrogen abstraction from α-tocopherol by lipid peroxyl radical forms α-tocopheroxyl radical detected by electron paramagnetic resonance. Quantification of lipid and protein hydroperoxide from the wild type and tocopherol deficient ( vte1 ) mutant Arabidopsis leaves using a colorimetric ferrous oxidation-xylenol orange assay reveals that α-tocopherol prevents formation of both lipid and protein hydroperoxides at high light. Identification of oxidation products of α-tocopherol might contribute to a better understanding of the protective role of α-tocopherol in the prevention of oxidative damage in higher plants at high light.

Nano-size calcium peroxide (nCaO 2 ) is an appropriate oxygen source which can meet the needs of in situ chemical oxidation (ISCO) for contaminant remediation from groundwater. In the present study, an easy to handle procedure for synthesis of CaO 2 nanoparticles has been investigated. Modeling and optimization of synthesis process was performed by application of response surface methodology (RSM) and central composite rotatable design (CCRD) method. Synthesized nanoparticles were characterized by XRD and FESEM techniques. The optimal synthesis conditions were found to be 5:1, 570 rpm and 10 °C for H 2 O 2 :CaSO 2 ratio, mixing rate and reaction temperature, respectively. Predicted values showed to be in good agreement with experimental results ( R 2 values were 0.915 and 0.965 for CaO 2 weight and nanoparticle size, respectively). To study the efficiency of synthesized nanoparticles for benzene removal from groundwater, batch experiments were applied in biotic and abiotic (chemical removal) conditions by 100, 200, 400, and 800 mg/L of nanoparticles within 70 days. Results indicated that application of 400 mg/L of CaO 2 in biotic condition was able to remediate benzene completely from groundwater after 60 days. Furthermore, comparison of biotic and abiotic experiments showed a great potential of microbial stimulation using CaO 2 nanoparticles in benzene remediation from groundwater.

The increasingly severe antibiotic pollution has become one of the most critical issues. In this study, a zinc peroxide/peroxymonosulfate (ZnO2/PMS) double-oxidation system was developed for tetracycline (TC) degradation. A small amount of ZnO2 (10 mg) and PMS (30 mg) could effectively degrade 82.8% of TC (100 mL, 50 mg/L), and the degradation process could be well described by the pseudo-second-order kinetic model. Meanwhile, the ZnO2/PMS double-oxidation system showed high adaptability in terms of reaction temperature (2–40 °C), initial pH value (4–12), common inorganic anions (Cl−, NO3−, SO42− and HCO3−), natural water source and organic pollutant type. The quenching experiment and electron paramagnetic resonance (EPR) characterization results confirmed that the main reactive oxygen species (ROS) was singlet oxygen (1O2). Moreover, three possible pathways of TC degradation were deduced according to the analyses of intermediates. On the basis of comparative characterization and experiment results, a synergistic activation mechanism was further proposed for the ZnO2/PMS double-oxidation system, accounting for the superior degradation performance. The released OH− and H2O2 from ZnO2 could activate PMS to produce major 1O2 and minor superoxide radicals (•O2−), respectively.

In order to facilely achieve pretreatment and salt-free dyeing of greige knitted cotton fabrics, a combinative scouring, bleaching, and cationization pretreatment of the fabrics is designed in this study. The fabrics are first treated in a bath containing commercial scouring and bleaching agents, and then glycidyltrimethylammonium chloride (GTA) is directly added into the bath to achieve cationization of the fabrics. Utilization of the alkaline and high-temperature conditions in scouring and bleaching process, cationization can facilely proceed in a short time. Optimal pretreatment conditions are as follows: greige knitted cotton fabrics are treated in a bath containing 4 g/L scouring agent and 6 g/L 30% hydrogen peroxide at 90 °C for 60 min, and then 30 g/L GTA and 3 g/L sodium hydroxide are added in the bath for another 15 min treatment. Fiber performances, including whiteness, water absorptivity, diffusion time, and capillary effect, are tested and evaluated. X-ray diffraction analysis, surface morphology, and thermal analysis of the pretreated cotton are also investigated and compared with that treated only with scouring and bleaching agents. Much higher dye fixation and color yield could be realized on the pretreated cotton in salt-free reactive dyeing. Colorimetric properties of the dyes are studied and good colorfastness of the dyes on the cationic fabrics are obtained. All of the above results show promising prospects of this combinative pretreatment in real application.

The objective of this study was to synthesize a novel choline hydroxide ionic liquid-based tooth bleaching gel. Ionic liquid-based gels were synthesized and characterized using FTIR along with pH testing. Tooth sample preparation was carried out in line with ISO 28399:2020. The effects of synthesized gels on tooth samples were tested. Tooth samples were stained and grouped into three experimental groups: EAI (22% choline hydroxide gel), EAII (44% choline hydroxide gel), and EB (choline citrate gel) and two control groups: CA (commercial at-home 16% carbamide peroxide gel) and CB (deionized water). The tooth color analysis, which included shade matching with the Vitapan shade guide (n = 2), and digital colorimetric analysis (n = 2) were evaluated. The surface characteristics and hardness were analyzed with 3D optical profilometry, Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDX), and Microhardness testing (n = 3), respectively. The tooth color analysis (Vitapan shade guide) revealed that all the tooth samples treated with synthesized choline citrate gel (EB) showed an A1 shade as compared to the other four groups, giving a range of shades. An analysis of the ΔE values from digital colorimetry; EAI, EAII, CA, and CB showed ΔE values in a range that was clinically perceptible at a glance. However, EB showed the highest value of ΔE. The mean microhardness values for the five groups showed that the effects of three experimental gels i.e., 44% choline hydroxide, 22% choline hydroxide, and choline citrate, on the microhardness of the tooth samples were similar to that of the positive control, which comprised commercial at-home 16% carbamide peroxide gel. SEM with EDX of three tested subgroups was closely related in surface profile, elemental composition, and Ca/P ratio. The roughness average values from optical profilometry of four tested subgroups lie within approximately a similar range, showing a statistically insignificant difference (p > 0.05) between the tested subgroups. The synthesized novel experimental tooth bleaching gels displayed similar tooth bleaching actions without any deleterious effects on the surface characteristics and microhardness of the treated tooth samples when compared with the commercial at-home tooth bleaching gel.

Degradation of 2,4,6-trichlorophenol (2,4,6-TCP) by zero-valent iron (ZVI) activating three common peroxides (peroxymonosulfate (PMS), hydrogen peroxide (H 2 O 2 ), and peroxydisulfate (PS)) was investigated. The effects of ZVI dosage, peroxides concentration, initial pH, and Cl - concentration were examined. The 2,4,6-TCP degradation efficiencies by Fe 0 /peroxides (PMS, H 2 O 2 , PS) were compared. Results showed that the order for degradation efficiency was H 2 O 2 ≥PMS>PS. The degradation efficiency of 2,4,6-TCP in ZVI/peroxides systems were optimal at c(Ox) = 1 mmol•L -1 ; c(Fe 0 ) = 0.1 g/L; initial pH = 3.2. Additionally, pH had a vital effect on 2,4,6-TCP degradation. At pH<3.2, ferrous play a vital role in all reaction, and accelerate the reaction rate rapidly. The existence of NaCl showed different results in the four systems. Chloride had little effect on 2,4,6-TCP degradation when chloride concentration at 5 mM, whereas the presence of 300 mM chloride significantly accelerated the degradation of 2,4,6-TCP from 72.7% to 95.2% in ZVI-PMS system. Notably, the other three systems showed opposite results. In contrast, the AOX (Absorbable Organic Halogen) values were highest in ZVI-PMS-Cl - system, due to the formation of lots of refractory chlorinated phenols as identified by GC-MS. These findings are good for choosing the most suitable technology for chlorophenol wastewater treatment.