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In this study, we fabricated phosphorus-modified carbon felt electrode anodes for chloride oxidation in saline solutions to produce HClO via electrocatalysis, forming a compound fungicide saline applicable for debridement and disinfection. A low-cost phosphorus-modified carbon felt electrode (P@CF) with high chlorine evolution reaction activity was synthesized to address the reduced efficiency of CER and the solution's pH increase. Heteroatoms P and O were introduced into the carbon felt by phosphoric acid activation followed by heat treatment. The maximum active chlorine concentration on the P@CF electrode could reach 616.8 mg/L in 60 min under the optimal synthesis conditions of a phosphoric acid mass fraction of 30%, a phosphoric acid impregnation time of 3 h, and a heat treatment temperature of 300 °C. The active chlorine concentration was 1.8 times higher on the P@CF electrode compared to the original carbon felt electrode. The optimal reaction conditions for the generation of active chlorine were as follows: salt concentration of 9 g/L, voltage of 7 V, and electrode spacing of 2 cm as verified by response surfaces. This electrolysis reaction follows one-stage reaction kinetics. Subsequently, the disinfection efficacy of the produced disinfectants was examined. The prepared disinfectant was also compared to a commercially available hypochlorite disinfectant, showing similar disinfection effects on E. coli for both., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

To identify toxicity drivers within poorly characterized high-molar-weight disinfection by-products (DBPs), relatively stable high-yield initial transformation products generated from aromatic amino acids and peptides and humic substances have drawn much attention. In this study, initial transformation products in chlorination of the indole moiety in tryptophan (Trp) are proposed and their formation mechanisms were investigated using a quantum chemical computational method. The results indicate that 3-Cl-Trp+ is initially formed after the Cl + of HOCl attacks the indole moiety, and nucleophilic addition with nucleophilic agents (H 2 O and OCl - ) is thermodynamically preferred over deprotonation to generate 2-X-3-Cl-indoline moiety (X = OH and OCl), which is in contrast to indole. Over 25 types of initial transformation products are proposed from the 2-X-3-Cl-indoline moiety and two ring opening pathways were found at N1-C2 and C2-C3 bonds. Significantly, most structures of initial transformation products proposed based on experimental detection m/z values were confirmed using quantum chemical calculations and some new products are proposed in this work. The results are helpful to expand our understanding of the intrinsic reactivity of aromatic ring towards chlorination by hypochlorous acid.

This study demonstrated that NiO and Ni(OH) 2 as Ni(II) catalysts exhibited significant activity for organic oxidation in the presence of various oxyanions, such as hypochlorous acid (HOCl), peroxymonosulfate (PMS), and peroxydisulfate (PDS), which markedly contrasted with Co-based counterparts exclusively activating PMS to yield sulfate radicals. The oxidizing capacity of the Ni catalyst/oxyanion varied depending on the oxyanion type. Ni catalyst/PMS (or HOCl) degraded a broad spectrum of organics, whereas PDS enabled selective phenol oxidation. This stemmed from the differential reactivity of two high-valent Ni intermediates, Ni(III) and Ni(IV). A high similarity with Ni(III)OOH in a substrate-specific reactivity indicated the role of Ni(III) as the primary oxidant of Ni-activated PDS. With the minor progress of redox reactions with radical probes and multiple spectroscopic evidence on moderate Ni(III) accumulation, the significant elimination of non-phenolic contaminants by NiOOH/PMS (or HOCl) suggested the involvement of Ni(IV) in the substrate-insensitive treatment capability of Ni catalyst/PMS (or HOCl). Since the electron-transfer oxidation of organics by high-valent Ni species involved Ni(II) regeneration, the loss of the treatment efficiency of Ni/oxyanion was marginal over multiple catalytic cycles.

This paper addresses the influence of bubbling flow and service life of the Ti|Ti-Ru-Ir-oxides anode during the electrosynthesis of HClO in a laboratory-scale filter-press-type electrolyzer. The electrolyzer was assembled in a flow plant in recirculation mode. Polarization curves in rotating disk electrode (RDE) revealed the coexistence of the oxygen evolution reaction (OER) during HClO electrosynthesis in diluted chloride solutions (containing 35 mM NaCl at pH 3). CFD simulations of the two-phase (O 2 -H 2 O) flow were obtained by solving simultaneously the Navier-Stokes and charge conservation equations using a finite element method code. The O 2 -H 2 O simulations show the efficient gas release in the electrolyzer provoked by the continuous phase (H 2 O) inertia and the well-engineered cell design. The moderated O 2 dispersion caused a quasi-homogeneous current distribution along the anode. However, the current efficiency during HClO electrosynthesis gave values of ∼32% provoked by the OER on the anode. The HClO accumulations (from 3.02 to 6.64 mM) showed excellent agreement with CFD simulations. The accelerated life tests revealed that the Ti | Ti-Ru-Ir-oxides anode has a lifetime of at least 26 years during the HClO electrosynthesis in diluted chloride solutions., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Since the onset of the SARS-CoV-2 pandemic in early 2020, there has been a notable rise in sodium hypochlorite disinfectants. Sodium hypochlorite undergoes hydrolysis to generate hypochlorous acid for virus eradication. This chlorine-based disinfectant is widely utilized for public disinfection due to its effectiveness. Although sodium hypochlorite disinfection is convenient, its excessive and indiscriminate use can harm the water environment and pose a risk to human health. Hypochlorous acid, a reactive oxygen species, plays a crucial role in the troposphere, stratospheric chemistry, and oxidizing capacity. Additionally, hypochlorous acid is vital as a reactive oxygen species in biological systems, and its irregular metabolism and level is associated with several illnesses. Thus, it is crucial to identify hypochlorous acid to comprehend its environmental and biological functions precisely. Here, we constructed a new fluorescent probe, utilizing the twisted intramolecular charge transfer mechanism to quickly and accurately detect hypochlorous acid in environmental water and biosystems. The probe showed a notable increase in fluorescence when exposed to hypochlorous acid, demonstrating its excellent selectivity, fast response time (less than 10 seconds), a large Stokes shift (∼ 102 nm), and a low detection limit of 15.5 nM., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Inc.)

Reactive oxygen species (ROS), reactive sulfur species (RSS), metal ions, and nitrogen species (RNS) play important roles in a variety of biological processes, such as a signal transduction, inflammation, and neurodegenerative damage. These species, while essential for certain functions, can also induce stress-related diseases. The interrelation between ROS, RSS, Metal ions and RNS underscores the importance of quantifying their concentrations in live cells, tissues, and organisms. The review emphasizes the use of small-molecule-based fluorescent/chemodosimeter probes to effectively measure and map the species' distribution with high temporal and spatial precision, paying particular attention to in vitro and in vivo environments. These probes are recognized as valuable tools contributing to breakthroughs in modern redox biology. The review specifically addresses the relationship of HOCl/ClO ‾ (hypochlorous acid/Hypochlorite) with other reactive species. (Dual sensing probes)., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Hypochlorite (ClO - ), as one of reactive oxygen species (ROS), is closely linked to various illnesses and is essential for the proper functioning of immune system. Hence, monitoring and assessing ClO - levels in organisms are extremely important for the clinical diagnosis of ClO - -related disorders. In this study, a novel ClO - -selective fluorescent probe, DCP-ClO, was synthesized with dicyanoisophorone-xanthene unit as parent fluorophore, which displayed excellent selectivity towards ClO - , near-infrared emission (755 nm), large Stokes shift (100 nm), real-time response to ClO - , high sensitivity (LOD = 3.95 × 10 -8  M), and low cytotoxicity. The recognition mechanism of DCP-ClO towards ClO - was confirmed to be a typical ICT process by HPLC-MS, HR-MS, 1 H NMR and theoretical calculations. Meanwhile, DCP-ClO demonstrated remarkable efficacy in monitoring ClO - levels in water samples and eye-catching ability in imaging endogenous/exogenous ClO - in living organisms, which verified its potential as a powerful tool for the recognition of ClO - in complex biological systems., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Posttranslational modifications in fibrinogen resulting from induced oxidation or oxidative stress in the organism can have deleterious influence on optimal functioning of fibrinogen, causing a disturbance in assembly and properties of fibrin. The protective mechanism supporting the ability of fibrinogen to function in ROS-generating environment remains completely unexplored. The effects of very low and moderately low HOCl/ - OCl concentrations on fibrinogen oxidative modifications, the fibrin network structure as well as the kinetics of both fibrinogen-to-fibrin conversion and fibrin hydrolysis have been explored in the current study. As opposed to 25 Μm, HOCl/ - OCl, 10 μM HOCl/ - OCl did not affect the functional activity of fibrinogen. It is shown for the first time that a number of Met residues, AαMet476, AαMet517, AαMet584, BβMet367, γMet264, and γMet94, identified in 10 μM HOCl/-OCl fibrinogen by the HPLC-MS/MS method, operate as ROS scavengers, performing an important antioxidant function. In turn, this indicates that the fibrinogen structure is adapted to the detrimental action of ROS. The results obtained in our study provide evidence for a protective mechanism responsible for maintaining the structure and functioning of fibrinogen molecules in the bloodstream under conditions of mild and moderate oxidative stress., Competing Interests: Declaration of competing interest The authors declare no conflict of interest., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Hypothiocyanous acid (HOSCN) is an endogenous oxidant produced by peroxidase oxidation of thiocyanate (SCN - ), an ubiquitous sulfur-containing pseudohalide synthesized from cyanide. HOSCN serves as a potent microbicidal agent against pathogenic bacteria, viruses, and fungi, functioning through thiol-targeting mechanisms, independent of currently approved antimicrobials. Additionally, SCN - reacts with hypochlorous acid (HOCl), a highly reactive oxidant produced by myeloperoxidase (MPO) at sites of inflammation, also producing HOSCN. This imparts both antioxidant and antimicrobial potential to SCN - . In this review, we discuss roles of HOSCN/SCN - in immunity and potential therapeutic implications for combating infections., Competing Interests: Declaration of competing interest The authors declare that they have no conflicts of interest., (Copyright © 2024 Elsevier Inc. All rights reserved.)

The present investigation sought to assess the practicality of utilizing a combined pre-treatment approach comprising electrocoagulation, peroxide, and hypochlorite treatments for the removal of chemical oxygen demand (COD) and tannin/lignin from paper mill wastewater. The study aimed to optimize the operating parameters with a view to maximizing the removal efficiencies while minimizing energy consumption. A pair of iron electrodes were used as anode and cathode in the study, and the main operating parameters were determined as initial pH, applied current, treatment time and oxidant dosage/COD ratio. Response surface methodology (RSM) was used to evaluate the effect of these parameters on COD and tannin/lignin removals. The primary findings of the investigation indicated that the integration of electrocoagulation with peroxide and hypochlorite treatments exhibited efficacy in removing COD, tannin/lignin, colour, phenol, and turbidity from paper mill wastewater. The optimized conditions resulted in COD removal efficiencies of 48.13 ± 2.2% and 29.53 ± 1.4% for EC with H 2 O 2 and Ca(OCl) 2 , respectively. Tannin/lignin removal efficiencies were 92.59 ± 3.6% and 94.09 ± 1.8% for EC-H 2 O 2 and EC-Ca(OCl) 2 , respectively. The specific energy consumption (SEC) values showed that EC-Ca(OCl) 2 required 7 times more energy than EC-H 2 O 2 for removing 1 kg COD. The principal deduction drawn from the study was that EC-H 2 O 2 pre-treatment demonstrated superior COD removal efficiency and lower energy consumption, while EC-Ca(OCl) 2 pre-treatment exhibited greater efficiency in removing toxic and recalcitrant pollutants. In future studies, it would be useful to conduct research to increase COD removal efficiency in addition to tannin/lignin removal in EC-Ca(OCl) 2 process.

Although various activated sodium hypochlorite (NaClO) systems were proven to be promising strategies for recalcitrant organics treatment, the direct interaction between NaClO and pollutants without explicit activation is quite limited. In this work, a revolutionary approach to degrade sulfathiazole (STZ) in aqueous and soil slurry by single NaClO without any activator was proposed. The results demonstrated that 100% and 94.11% of STZ could be degraded by 0.025 mM and 5 mM NaClO in water and soil slurry, respectively. The elimination of STZ was shown to involve superoxide anion (O 2 •- ), chlorine oxygen radical (ClO•), and hydroxyl radical (•OH), according to quenching experiments and the analysis of electron paramagnetic resonance. The addition of Cl - , HCO 3 - , SO 4 2- , and humic acid (HA) marginally impeded the decomposition of STZ, while NO 3 - , Fe 3+ , and Mn 2+ facilitated the process. The NaClO process exhibited significant removal effectiveness at a neutral initial pH. Moreover, the NaClO facilitated application in various soil samples and water matrices, and the procedure was also successful in effectively eliminating a range of sulfonamides. The suggested NaClO degradation mechanism of STZ was based on the observed intermediates, and the majority of the products exhibited lower ecotoxicity than STZ. Besides, the experiment results by using X-ray diffraction (XRD) and a fourier transform infrared spectrometer (FTIR) indicated the negligible effects on the composition and structure of soil by the treatment of NaClO. Simultaneously, the experimental results also illustrated that the bioavailability of heavy metals and the physiochemical characteristics of the soil before and after the remediation did not change to a significant extent. Following the remediation of NaClO, the phytotoxicity tests showed reduced toxicity to wheat and cucumber seeds. As a result, treating soil and water contaminated with STZ by using NaClO was a reasonably practical and eco-friendly method., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Hypochlorous acid (HClO) is used in food preservation. However, excessive HClO can deteriorate nutritional composition of food, compromise its quality, and potentially induce various diseases. Consequently, the development of multifunctional fluorescent probes for the sensitive and selective detection of HClO is highly anticipated for food safety. In this work, we designed a nanoprobe using N-aminomorpholine (AM)-functionalized bromine-doped carbon dots (Br-CDs-AM) for sensing HClO. This nanoprobe exhibits pH stability, strong resistance to photobleaching, superior long-term photostability (12 weeks), high sensitivity (19.3 nM), and an ultrarapid response (8 s) for detecting HClO residues in food matrices with percentage recovery (96.5 %-108 %) and RSDs less than 5.34 %. In addition, extremely low cytotoxicity and outstanding biocompatibility enable the nanoprobe to be used primarily for lysosome tracking and rapidly visualizing HClO in live cells. Thus, this study provides a new pathway to design unconventional nanoprobes for food safety assessment and subcellular organelle-specific imaging HClO., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

For the first time, three acceptor-donor-acceptor (A-D-A)-type boranil fluorescent dyes, CSU-BF-R (R = H, CH 3 , and OCH 3 ), featuring phenothiazine as the donor, were designed and synthesized. CSU-BF-R exhibited remarkable photophysical characteristics, including large Stokes shifts (>150 nm), high fluorescence quantum yields (up to 40%), long-wavelength emissions, and strong red solid-state fluorescence. Moreover, these CSU-BF-R fluorescent dyes were demonstrated to function as highly selective and sensitive ratiometric fluorescent probes for detecting hypochlorous acid (HClO). The preliminary biological applications of CSU-BF-OCH3 for sensing intracellular HClO in living cells and zebrafish were demonstrated. Therefore, CSU-BF-R possess the potential to further explore the physiological and pathological functions associated with HClO and provide valuable insights into the design of high-performance A-D-A-type fluorescent dyes.

Fatty acids from cooking fumes and hypochlorous acid (HOCl) released from indoor cleaning adversely affect respiratory health, but the molecular-level mechanism remains unclear. Here, the effect of cooking oil fumes [palmitic acid (PA), oleic acid (OA), and linoleic acid (LA)] on lung model phospholipid (POPG) hydrochlorination mediated by HOCl at the air-water interface of the hanged droplets was investigated. Interfacial hydrochlorination of POPG was impeded by OA and LA, while that of POPG was facilitated by PA. The effect on POPG hydrochlorination increased with the decrease in oil fume concentration. A potential mechanism with respect to the chain length of these oil fumes, regardless of their saturation, was proposed. PA with a short carbon chain looses the POPG packing and leads to the exposure of the C=C double bonds of POPG, whereas OA and LA with a long carbon chain hinder HOCl from reaching the C=C bonds of POPG. These results for short chain and low concentration dependence suggest that the decay of oil fumes or the conversion of short-chain species by indoor interfacial chemistry might be adverse to lung health. These results provide insights into the relationship between indoor multicomponent pollutants and the respiratory system., (© 2024 Author(s). Published under an exclusive license by AIP Publishing.)

Hypochlorous acid (HOCl) released from activated leukocytes plays a significant role in the human immune system, but is also implicated in numerous diseases due to its inappropriate production. Chlorinated nucleobases induce genetic changes that potentially enable and stimulate carcinogenesis, and thus have attracted considerable attention. However, their multiple halogenation sites pose challenges to identify them. As a good complement to experiments, quantum chemical computation was used to uncover chlorination sites and chlorinated products in this study. The results indicate that anion salt forms of all purine compounds play significant roles in chlorination except for adenosine. The kinetic reactivity order of all reaction sites in terms of the estimated apparent rate constant k obs-est (in M -1 s -1 ) is heterocyclic NH/N (10 2 -10 7 ) > exocyclic NH 2 (10 -2 -10) > heterocyclic C8 (10 -5 -10 -1 ), but the order is reversed for thermodynamics. Combining kinetics and thermodynamics, the numerical simulation results show that N9 is the most reactive site for purine bases to form the main initial chlorinated product, while for purine nucleosides N1 and exocyclic N 2 / N 6 are the most reactive sites to produce the main products controlled by kinetics and thermodynamics, respectively, and C8 is a possible site to generate the minor product. The formation mechanisms of biomarker 8-Cl- and 8-oxo-purine derivatives were also investigated. Additionally, the structure-kinetic reactivity relationship study reveals a good correlation between lg  k obs-est and APT charge in all purine compounds compared to FED 2 (HOMO), which proves again that the electrostatic interaction plays a key role. The results are helpful to further understand the reactivity of various reaction sites in aromatic compounds during chlorination.

Purpose: To study the stability of physicochemical properties and sterilizing effect about two commercially available hypochlorous acid (HClO) products under simulated clinical conditions, and to evaluate the compatibility of HClO on soft and hard tissues and cells in oral cavity., Methods: Samples of HClO solution with different production processes were prepared, to detect the changes of physicochemical indexes of each sample over time under simulated clinical conditions (shielded from light at 20-25 ℃, open the cover for 5 minutes every day), including free available chlorine, oxidation-reduction potential and pH. Through suspension quantitative germicidal test, the antibiosis-concentration curve of HClO solution was made, so as to calibrate the change of antibacterial ability of disinfectant with the decrease of available chlorine content during storage. Pulp, tongue and dentine were immersed in PBS, 100 ppm HClO, 200 ppm HClO and 3% NaClO. The influence on soft and hard tissues was evaluated by weighing method and microhardness test. The toxic effects of HClO, NaClO and their 10-fold diluent on human gingival fibroblasts were determined by CCK-8 cytotoxicity assay. GraphPad PRIS 8.0 software was used to analyze the data., Results: Under simulated conditions, the free available chlorine (FAC) of HClO solution decayed with time, and the attenuation degree was less than 20 ppm within 1 month. The bactericidal effect of each HClO sample was still higher than 5log after concentration decay. There was no obvious dissolution and destruction to soft and hard tissues for HClO(P＞0.05). The cell viability of HClO to human gingival fibroblast cells (HGFC) was greater than 80%, which was much higher than 3% NaClO (P＜0.001)., Conclusions: The bactericidal effect and stability of HClO solution can meet clinical needs, which has low cytotoxicity and good histocompatibility. It is expected to become a safe and efficient disinfection product in the field of living pulp preservation and dental pulp regeneration.

Hypochlorous acid (HClO) is a key signaling molecule which involved in various pathological and physiological processes and the immune system. It had been proved that excess HClO in the organisms was closely associated with diabetes. In this paper, we constructed a series of BODIPY-based fluorophores modified with olefinic bond. With the assistance of theoretical calculations, the optimized near-infrared (NIR) dye BDP-ENE-S-Me, which possessed the longest wavelength (690 nm) and the best stability, was screened and synthesized. Based on BDP-ENE-S-Me, we further introduced N, N-dimethylcarbamate group to construct a NIR fluorescent probe BDP-ENE-ClO. BDP-ENE-ClO displayed excellent selectivity and sensitivity with a low detection limit (49 nM) towards HClO. Besides, the probe was successfully applied in monitoring concentration fluctuations of HClO in vitro and in vivo caused by various stimuli. Most importantly, the over-production of HClO in the type I, type II diabetes and diabetic liver disease mice models could be visualized and assessed precisely with the assistance of BDP-ENE-ClO. By comparing fluorescent intensity of diabetic mice models with that of diabetic liver disease mice models, the probe was competent to assess the progression of diabetes., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Hypochlorous acid (HOCl) is a common reactive oxygen species (ROS) associated with the development of liver, tumor, inflammatory, and other diseases. In this work, the turn-on fluorescent probe named (WZ-HOCl) with a naphthalimide structure was designed and synthesized to detect endogenous HOCl in disease models. WZ-HOCl can achieve a fast response to HOCl with good linearity in the range of 0-45 μM (LOD = 147 nM). The application of WZ-HOCl in bioimaging was investigated by constructing a series of cellular disease models, and the results showed that WZ-HOCl could sensitively detect endogenous HOCl in inflammatory and liver disease models. It can also be used to differentiate between hepatocytes and hepatoma cells. WZ-HOCl will provide new methods and ideas for fluorescent probes in detecting drug-induced liver injury, alcoholic and non-alcoholic steatohepatitis, and some inflammation-related diseases., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Inc. All rights reserved.)

The generation and presence of excessive hypochlorous acid derivative ionic form (ClO - ) could cause various diseases, such as arteriosclerosis, DNA damage, and cardiovascular illness. It is a critical need to develop a highly sensitive sensor for reliable detection of ClO - in cells and water-soluble systems. In this work, a hydroxyl group has been introduced into the compound 2-amino-3-(((E)-4-(2-(2-(2-hydroxyethoxy)ethyl)-1,3-dioxo-2,3-dihydro-1H-benzo[de]isoquinolin-6-yl)benzylidene)amino)maleonitrile (NDC) to increase its solubility in water, at the same time, the hydrazone unit was designed as a specific recognition group for the "off-on" fluorescence probe of ClO - . The probe NDC presents high selectivity, sensitivity, anti-interference, and low detection limit (67 nM) for ClO - . The recognition mechanism that ClO - breaks the C=N bond and forms the fluorescent compound 4-(2-(2-(2-hydroxyethoxy)ethyl)-1,3-dioxo-2,3-dihydro-1H-benzo[de]isoquinolin-6-yl)benzaldehyde (ND-3) has been confirmed by time-of-flight mass spectrometry. The probe NDC presents a good performance in the actual test of water samples and can be designed as the test papers for the quick and convenient detection of ClO - range from 0 to 1 μM. Moreover, the practical application was demonstrated by the successful imaging of endogenous and exogenous ClO - in HeLa cells. Our fluorescent biomass-based platform opens vast possibilities for repeatability, sensitivity, and selectivity detection of ClO - in cells and water-soluble systems., Competing Interests: Declaration of Conflicting InterestsThe authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

An air washer-type humidifier has two useful functions: humidification, and air purification, and it applies to large indoor spaces. In this study, the efficacy of an air washer-type humidifier fed with 24 L of weakly acidic electrolyzed water（WAEW) at pH 5.0 and 30 mg/L in disinfecting attached bacteria and airborne microorganisms was studied in a 480 m3 indoor space. The humidifier was operated at a shower volume of 9.0 L/min of WAEW and at an air flow rate of 29 m3 /min. Volatilization of gaseous hypochlorous acid（HOCl (g) ) proceeded according to first-order kinetics during the 60 min of operation. Fresh WAEW was supplied to the humidifier every 60 min, and the HOCl (g) concentration in the indoor space was maintained within the range of 25-52 ppb for at least 180 min of operation. The number of viable bacterial cells on wet agar plates placed on the floor at a distance of 5-20 m away from the humidifier decreased by 2.0-3.0 log after 30 min of operation, and no viable cells were detected after 60 min of operation. A logarithmic reduction of more than 2.7 was achieved within 15 min against bacteria-attached plates placed at a 1.5 m-height position where the outlet airflow from the humidifier was directly exposed. This indicates that the disinfection efficacy of HOCl (g) volatilized from the humidifier depends on the rate of outlet airflow reaching the bacteria-attached plates. The number of viable airborne microorganisms decreased by approximately 54% after 180 min of operation. This study demonstrated that an air-washer-type humidifier can spread HOCl (g) evenly throughout a large indoor space and is effective in disinfecting attached bacteria and airborne microorganisms.

When a hypochlorite solution is ultrasonically fogged in a room, free chlorine, i.e., HOCl and OCl - , reaches various positions in two forms: fine fog droplets and gaseous hypochlorous acid（HOCl (g) ）. In this study, the cumulative amount of free chlorine reaching various positions on the floor away from the fogger was measured in a 90-m 3 room, using a sulfamate-carrying glass-fiber filter indicator. The fine droplets were blown out from the fogger into the spaces at different discharge port angles of 30 - 90°. Free chlorine was successfully trapped by sulfamate, forming monochlorosulfamate, which was stably retained on the indicator. The cumulative amount of free chlorine（ ng/indicator） increased with fogging time at each position and depended on the blow angle and distance from the fogger. Minor differences in the HOCl (g) concentration near the floor at all positions were observed. The disinfection efficacy of the fogging treatment against Staphylococcus aureus on wet surfaces was relatively higher at positions near the fogger and lower at positions far from the fogger. At each discharge port angle, a strong correlation between the logarithmic reduction in relative viable cells and the cumulative amount of free chlorine reaching S. aureus plates was observed. The slopes of the regression lines of correlation diagrams as a function of the cumulative amount of free chlorine were between -0.0362 and -0.0413 ng -1 . This study demonstrated that the cumulative amount of free chlorine measured using the filter indicator could reflect the sum of the free chlorine of both fine droplets and HOCl (g) , and that the disinfection efficiency depended on the cumulative amount of free chlorine reaching different areas.

On the basis of classical Schiff base reaction, two novel and efficient fluorescent probes (DQNS, DQNS1) were designed and synthesized by introducing Schiff base structure into dis-quinolinone unit for structural modification, which can be used to detect Al 3+ and ClO - . Because the power supply capacity of H is weaker than that of methoxy, DQNS shows better optical performance: a large Stokes Shift (132 nm), identify Al 3+ and ClO - with high sensitivity and selectivity, low detection limit (29.8 nM and 25 nM) and fast response time (10 min and 10 s). Through the working curve and NMR titration experiment, the recognition mechanism of Al 3+ and ClO - (PET and ICT) probes are confirmed. Meanwhile, it is speculated that the probe has continuity for the detection of Al 3+ and ClO - . Furthermore, DQNS detection of Al 3+ and ClO - was applied to real water samples and living cell imaging., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

We report the development of a bifunctional near-infrared fluorescent probe (QZB) for selective sensing of bisulfite (HSO 3 - ) and hypochlorous acid (HOCl). The synergistic detection of HSO 3 - and HOCl was achieved via a C=C bond recognition site. In comparison with the red-fluorescence QZB, two different products with non-fluorescence and paleturquoise fluorescence were produced by the recognition of QZB towards HSO 3 - and HOCl respectively, which can realize effectively the dual-functional detection of HSO 3 - and HOCl. QZB features prominent preponderances of dual-function response, near-infrared emission, reliability at physiological pH, low cytotoxicity and high sensitivity to HSO 3 - and HOCl. The detection of HSO 3 - in actual food samples has been successfully achieved using QZB. Utilization of QZB-based test strip to semi-quantitatively detect HSO 3 - and HOCl in real-world water samples by the "naked-eye" colorimetry are then demonstrated. Simultaneously, the determination of HSO 3 - and HOCl in real-world water sample has been achieved by smartphone-based standard curves. Additionally, the applications of QZB for imaging HSO 3 - and HOCl in vivo are successfully demonstrated. Consequently, the successful development of QZB could be promising as an efficient tool for researching the role of HSO 3 - /HOCl in the regulation of redox homeostasis regulation in vivo and complex signal transduction and for future food safety evaluation., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Triclocarban (TCC) is an antimicrobial agent commonly used in many household and personal care products, and has been found persistent in the aquatic environment. Here we elucidate the kinetics and mechanism of TCC degradation during chlorination process by density functional theory (DFT) calculation and experimental verification. Results showed that hypochlorous acid (HOCl)/hypochlorite (OCl - ) reacted with TCC via Cl-substitution, OH-substitution and C-N bond cleavage pathways. The reactivity of OCl - (2.80 × 10 -7  M -1  s -1 ) with TCC was extremely low and HOCl (1.96 M -1  s -1 ) played the dominant role in TCC chlorination process. The N site of TCC was the most reactive site for chlorination. The second-order rate constants, which are determined using density functional theory (DFT) (k TCC-chlorine C , 1.96 M -1  s -1 ), can be separated into reaction rate constants related to the reactions of HOCl and OCl - with different isomers of TCC (TCC2 and TCC6). The obtained k TCC-chlorine C was consistent with the experimental determined second-order rate constant (k TCC-chlorine E , 3.70 M -1  s -1 ) in chlorination process. Eight transformation products (TP348, TP382, TP127, TP161, TP195, TP330, TP204, and TP296) were experimentally detected for chlorination of TCC, which could also be predicted by DFT calculation. Explicit water molecules participated in the chlorination reaction by transmitting the proton and connecting with TCC, HOCl/OCl - and other H 2 O molecules, and obviously reduced the energy barrier of chlorination., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Lab-on-a-paper-based devices are promising alternatives to the existing arduous techniques for point-of-need monitoring. The present work reports an instant and facile method to produce a microfluidic paper-based analytical device (μPAD). The fabricated μPAD has been used to detect hypochlorite (OCl - ) by incorporating newly synthesized chromo-fluorogenic ratiometric probes 1 and 2 into the sample reception zone. The probes showed high selectivity and fast response (<10 s) toward OCl - with an excellent linear relationship in the concentration range of 0-100 μM. The concentration-dependent fluorometric change driven by the reaction of 1@μPAD with OCl - has been monitored using gel-doc imaging systems, which is unprecedented. Digitizing the intensity of the colour solution with different mathematical models of colour has developed a straightforward method for monitoring OCl - without any interference from its competitors. 1@μPAD can detect OCl - at ∼10 times lower than the WHO recommended limit. The detection limit of 1@μPAD via a digital camera-based fluorescence technique was found to be better over digital camera-based cuvette assays. Therefore, 1@μPAD has been successfully utilized to monitor OCl - in actual environmental water samples with portability, ease of use, and sensitivity. The analytical RSD was found to be ≤3% based on fluorimetric detection using 1@μPAD. The chemodosimetric reaction between OCl - and the probe was evidenced by UV-vis and fluorescence spectroscopy, 1 H NMR, and ESI-MS. The rapid response time, biocompatibility, low cytotoxicity, 100% aqueous solubility, ratiometric feature, and exclusive OCl - selectivity over other competitive ROS/RNS successfully lead to the application of the probes for bioimaging of exogenous as well as endogenous OCl - in normal cells (HEK293) and cancerous cells (HeLa).

Over the past few decades, drug-induced liver damage (DILI) has become a serious public health problem due to drug abuse. Among multifarious reactive oxygen species, mounting evidence attests that ClO - has been used as a potential biomarker in DILI. In this work, a new "turn-on" fluorescent probe 1 was designed and synthesized by modifying 4'-hydroxybiphenyl-4-carbonitrile (dye 2 ) with N, N -dimethylthiocarbamate as a response site for detecting ClO - . Probe 1 displayed a low detection limit (72 nM), fast response time (30 s), wide pH operating range (6-8), great tissue penetration, large Stokes shift (125 nm) and 291-fold fluorescence enhancement at 475 nm in the mapping of ClO - . Probe 1 could trace amounts of exogenous and endogenous ClO - with high sensitivity in MCF-7 cells and HeLa cells. Expectantly, the fluoxetine-induced liver injury model is successfully established, and probe 1 has been used for detecting the fluctuation of ClO - levels in the mouse model of fluoxetine-induced liver injury. All in all, probe 1 with its high specificity, good biological compatibility and liver tissue penetration ability is expected to assist with the early diagnosis of DILI and the clinical screening of various new drugs. We expect that probe 1 could be efficiently used as a powerful molecular tool to predict clinical DILI and explore molecular mechanisms between molecules and disease.

A certain amount of hypochlorite can help to regulate the body's defense system while excessive hypochlorite has some complex influence on health. Herein, a thiophene-derived biocompatible turn-on fluorescent probe (TPHZ) was synthesized and characterized for the detection of hypochlorite (ClO - ). The fluorescence and colorimetric sensing of the probe followed an ICT OFF strategy. The experimental results showed a remarkable turn on fluorescence enhancement from colorless to bright blue after the addition of ClO - within 130 s in a solvent system having 80% water with high selectivity and a low detection limit of 53.8 nM. The sensing mechanism was attributed to ClO - mediated electrophilic addition to the imine bond which was justified by DFT calculations, and ESI-MS and 1 H-NMR titration experiments. The probe was used in an application to visualize ClO - in human breast cancer cells which can be helpful for investigating the functions of hypochlorite in living cells. Finally, by virtue of fine photophysical properties, good sensing performance, good water solubility and low limit of detection, the probe TPHZ was successfully applied to TLC test strips, and commercial bleach and water samples.

Being one of the vital reactive oxygen species (ROS), abnormal level of hypochlorite ion (ClO - ) may pose detrimental threats to living organisms. Therefore, highly selective, and rapid monitoring of ClO - in living system is of prime importance to protect living organisms from its harmful effects. In this regard, design of synthetic fluorescent probes for ClO - has garnered considerable attention. However less fluorescence emission in aggregated state and less photostability of several existing probes for ClO - inspired us to design aggregation induced emission (AIE) active fluorescent probes SH1 and SH2. Probes were rationally designed by introducing thiourea moiety that selectively reacted through desulfurization reaction and resulted in highly selective detection of ClO - . Hypochlorite induced desulfurization reaction was validated through 1 H NMR titration and DFT studies. Fine tuning of probes SH1 and SH2 prompted highly sensitive nanoscale (55 nM and 77 nM) and rapid (15 and 35 sec) detection of ClO - . Probe SH1 displayed less cytotoxic effect to live cells before it was successfully applied for bioimaging of ClO - in live MCF-7 cells. Moreover, probes displayed excellent sensing potential for ClO - in blood serum and real water samples. Advantageously, probe coated portable fluorescent films were fabricated for the easy and fast monitoring of ClO - . Of note, this work offers excellent design strategy for highly selective detection of ClO - that may lead to clinical trials., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

A novel dual-response fluorescence probe ( XBT-CN ) was developed by using a fluorescence priming strategy for quantitative monitoring and visualization of hydrazine (N 2 H 4 ) and hypochlorite (ClO - ). With the addition of N 2 H 4 /ClO - , the cleavage reaction of C=C bond initiated by N 2 H 4 /ClO - was transformed into corresponding hydrazone and aldehyde derivatives, inducing the probe XBT-CN appeared a fluorescence "off-on" response, which was verified by DFT calculation. HRMS spectra were also conducted to confirm the sensitive mechanism of XBT-CN to N 2 H 4 and ClO - . The probe XBT-CN had an obvious fluorescence response to N 2 H 4 and ClO - , which caused a significant color change in unprotected eyes. In addition, the detection limits of XBT-CN for N 2 H 4 and ClO - were 27 nM and 34 nM, respectively. Interference tests showed that other competitive analytes could hardly interfere with the detection of N 2 H 4 and ClO - in a complex environment. In order to realize the point-of-care detection of N 2 H 4 and ClO - , an XBT-CN @hydrogel test kit combined with a portable smartphone was developed. Furthermore, the portable test kit has been applied to the detection of N 2 H 4 and ClO - in a real-world environment and food samples, and a series of good results have been achieved. Attractively, we demonstrated that XBT-CN @hydrogel was successfully applied as an encryption ink in the field of information security. Finally, the probe can also be used to monitor and distinguish N 2 H 4 and ClO - in living cells, exhibiting excellent biocompatibility and low cytotoxicity.

Hypochlorous acid (HClO) and derivative ionic form (ClO - ) are significant components of reactive oxygen species, and thus various diseases are correlatively related to the concentration of ClO - . Recently, paper-based indicators have been confirmed to be efficient strategy for sensing hazardous and noxious substances. However, most of these materials can only achieve qualitative detection of the substrates. Herein, an extremely simple manufacturing strategy was proposed to convert commonly-used paper into nano-engineered fluorescent biomass-based platform (CMJL-FP) integrated with on-demand self-assembled colorimetric and ratiometric fluorescence sensor (CMJL) for rapid ClO - quantitative detection in organisms or water sources using smartphones. The CMJL exhibited a highly selective and sensitive ratiometric response to ClO - at a low detection limit (LOD = 92.6 nM). The associating interactions between the fluorescence nano-particles and micro-nano fibers of CMJL-FP ensure good-stability during ClO - detection. It has been experimentally demonstrated that CMJL-FP allows one to realize the rapid quantitative detection of ClO - ions in living cells and large-scale water sources by using color recognition software as part of a simple smartphone. Therefore, integrating the proposed fluorescent paper with smartphones provides an effective, sustainable, cheap and conceptual strategy for quantitative detection of hazardous and noxious substances in organisms and environments., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

The structure and thermal properties of pulsed electric field (PEF) assisted sodium hypochlorite oxidized starch were investigated. The carboxyl content of the oxidized starch was increased by 25 % when compared with the traditional oxidation method. Dents and cracks were evident on the surface of the PEF-pretreated starch. Compared with native starch, the peak gelatinization temperature (T p ) of PEF-assisted oxidized starch (POS) was reduced by 10.3 °C, while that of the oxidized starch without PEF treatment (NOS) was only reduced by 7.4 °C. In addition, PEF treatment further reduces the viscosity and improve the thermal stability of the starch slurry. Therefore, PEF treatment combined with hypochlorite oxidation is an effective method to prepare oxidized starch. PEF showed great potential in expanding starch modification, to promote a wider application of oxidized starch in the paper, the textile and the food industry., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

A multifunctional dehydroabietic acid-based fluorescent probe (CPS) was designed and synthesized by introducing the 2,6-bis(1 H -benzo[ d ]imidazol-2-yl)phenol fluorophore. The probe CPS could selectively recognize Cu 2+ , Zn 2+ and ClO - ions from other analytes, and it showed fluorescence quenching behavior toward Cu 2+ and a ratiometric response to Zn 2+ and ClO - by changing from green fluorescence to blue and cyan, respectively. The detection limits toward Cu 2+ , Zn 2+ and ClO - ions were 3.8 nM, 0.253 μM and 0.452 μM, respectively. In addition, CPS presented many fascinating merits, such as high selectivity, a short response time (15-20 s), a wide pH range (3-10) and high photostability. The sensing mechanisms of CPS were verified by 1 H-NMR, ESI-MS, FT-IR and Job's plot methods. Meanwhile, CPS exhibited satisfactory detection performance in water samples. More importantly, the probe could be applied as a promising tool for visual bioimaging of three ions in living cells and zebrafishes.

Being one of the important reactive oxygen species (ROS), hypochlorite ions (ClO - ) are involved in the control of several pathological and physiological processes. However, overexpression of ClO - may prompt several disorders including cancer. Therefore, two fluorescein functionalized compounds with catechol (probe 1) and 2-naphthyl (probe 2) as substituents were synthesized through Schiff base reaction to recognize ClO - in food items and industrial samples. While probe 2 exhibited turn-off fluorescent response towards ClO - with limit of detection (LOD) of 86.7 nM, structurally alike probe 1 showed excellent ratiometric response with low detection limit (36.3 nM), large Stokes shift (353 nm), and 'fast' response time (15 s). 1 H NMR titration experiments favored spiroring opening of probe 1 upon the reaction with ClO - . Probe 1 was successfully utilized for the monitoring of exogenous ClO - in industrial samples. Further, fabrication of probe coated fluorescent paper strips and recognition of ClO - in sprouting potato show diverse practical applicability of our probes., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Chloramines (NH 2 Cl, NHCl 2 , and NCl 3 ) are toxic compounds that can be created during the use of bleach-based disinfectants that contain hypochlorous acid (HOCl) and the hypochlorite ion (OCl - ) as their active ingredients. Chloramines can then readily transfer from the aqueous-phase to the gas-phase. Atmospheric chemical ionization mass spectrometry using iodide adduct chemistry (I-CIMS) made observations across two periods (2014 and 2016) at an urban background site on the University of Leicester campus (Leicester, UK). Both monochloramine (NH 2 Cl) and molecular chlorine (Cl 2 ) were detected and positively identified from calibrated mass spectra during both sampling periods and to our knowledge, this is the first detection of NH 2 Cl outdoors. Mixing ratios of NH 2 Cl reached up to 2.2 and 4.0 parts per billion by volume (ppbv), with median mixing ratios of 30 and 120 parts per trillion by volume (pptv) during the 2014 and 2016 sampling periods, respectively. Levels of Cl 2 were observed to reach up to 220 and 320 pptv. Analysis of the NH 2 Cl and Cl 2 data pointed to the same local source, a nearby indoor sports complex with a swimming pool and a cleaning product storage shed. No appreciable levels of NHCl 2 and NCl 3 were observed outdoors, suggesting the indoor pool was not likely to be the primary source of the observed ambient chloramines, as prior measurements made in indoor pool atmospheres indicate that NCl 3 would be expected to dominate. Instead, these observations point to indoor cleaning and/or cleaning product emissions as the probable source of NH 2 Cl and Cl 2 where the measured levels provide indirect evidence for substantial amounts transported from indoors to outdoors. Our upper estimate for total NH 2 Cl emissions from the University of Leicester indoor sports complexes scaled for similar sports complexes across the UK is 3.4 × 10 5 ± 1.1 × 10 5 μg h -1 and 0.0017 ± 0.00034 Gg yr -1 , respectively. The Cl-equivalent emissions in HCl are only an order of magnitude less to those from hazardous waste incineration and iron and steel sinter production in the UK National Atmospheric Emissions Inventory (NAEI).

The Golgi apparatus (GA) is a vital organelle in biological systems and excess reactive oxygen species (ROS) is produced during stress in the Golgi apparatus. Hypochlorous acid (HOCl) is a significant reactive oxygen species and has strong oxidative and antibacterial activity, but excessive secretion of hypochlorous acid can affect Golgi structure or function abnormally, it will lead to a series of diseases including Alzheimer's disease, neurodegenerative diseases, autoimmune diseases, and Parkinson's disease. In present work, a novel fluorescent probe for Golgi localization utilizing naphthalimide derivatives was constructed to detect hypochlorous acid. The fluorescent probe used a derivatived 1,8-naphthalimide as the emitting fluorescence group, phenylsulfonamide as the localization group and dimethylthiocarbamate as the sensing unit. When HOCl was absent, the intramolecular charge transfer (ICT) process of the developed probe was hindered and the probe exhibited a weak fluorescence. When HOCl was present, the ICT process occurred and the probe showed strong green fluorescence. When the HOCl concentration was altered from 5.0 × 10 -7 to 1.0 × 10 -5  mol·L -1 , the fluorescence intensity of the probe well linearly correlated with the HOCl concentration. The detection limit of 5.7 × 10 -8  mol·L -1 was obtained for HOCl. The HOCl fluorescent probe possessed a rapid reaction time, a high selectivity and a broad working pH scope. In addition, the probe possessed good biocompatibility and had been magnificently employed to image Golgi HOCl in Hela cells. These characteristics of the probe demonstrated its ability to be used for sensing endogenous and exogenous hypochlorous acids within the Golgi apparatus of living cells., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Hypochlorous acid (HOCl), as an important biological reactive oxygen species (ROS), plays an important role in microbial immune defense and inflammatory response. Abnormal levels of HOCl in lysosomes can cause lysosomal membrane rupture and release of various hydrolases, leading to a variety of diseases, including cancer. In order to better monitor the level of HOCl in lysosomes, phenothiazine was chosen as fluorophore to construct a NIR fluorescent probe PMM with intramolecular change transfer process (ICT). PMM is a colorimetric and ratiometric fluorescent probe, which has high sensitivity with a low detection limit (20 nM), high selectivity and anti-interference. PMM has good stability in the weakly acidic environment of pH 4.0-5.5. PPM has good localization ability for lysosomes and has been successfully used for fluorescence imaging of exogenous and endogenous HOCl in HepG2 cells. Moreover, nude mouse imaging also demonstrated that PMM could be used to detect HOCl in vivo., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Conversion of the redox probe hydroethidine (HE) to 2-chloroethidium (2-Cl-E + ) by myeloperoxidase (MPO)-derived hypochlorous acid (HOCl) provides comparable specificity and superior sensitivity to measurement of 3-chlorotyrosine (3-Cl-Tyr), the gold standard biomarker for MPO chlorinating activity in biological systems. However, a limitation of the former method is the complex mixture of products formed by the reaction of HE with reagent HOCl, coupled with the difficult purification of 2-Cl-E + from this mixture for analytical purposes. This limitation prompted us to test whether 2-Cl-E + could be formed by reaction of HE with the strong and widely used chlorinating agent, N-chlorosuccinimide (NCS). Unexpectedly, such reaction yielded 2-chlorohydroethidine (2-Cl-HE) as the major product in addition to 2-Cl-E + , as assessed by high performance liquid chromatography (HPLC), mass spectrometry (MS), and nuclear magnetic resonance (NMR). 2-Cl-HE was also observed to be the major chlorination product formed from HE with both reagent and enzymatically generated HOCl, just as it was formed ex vivo in different healthy and diseased mouse and human tissues upon incubation with glucose/glucose oxidase to generate a flux of hydrogen peroxide (H 2 O 2 ). Quantification of 2-Cl-HE plus 2-Cl-E + improved the sensitivity of the HE-based method compared with measurement of only 2-Cl-E + . Moreover, 2-chlorodimidium (2-Cl-D + ) was developed as a practical internal standard instead of the previously used internal standard, deuterated 2-Cl-E + (d 5 -2-Cl-E + ). Overall, the present study describes an improved method for the detection of MPO/chlorinating activity in biological systems of health and disease., (Copyright © 2022 The Authors. Published by Elsevier Inc. All rights reserved.)

Cleaning surfaces with sodium hypochlorite (NaOCl) bleach can lead to high levels of gaseous chlorine (Cl 2 ) and hypochlorous acid (HOCl); these have high oxidative capacities and are linked to respiratory issues. We developed a novel spectral analysis procedure for a cavity ring-down spectroscopy (CRDS) hydrogen peroxide (H 2 O 2 ) analyzer to enable time-resolved (3 s) HOCl quantification. We measured HOCl levels in a residential bathroom while disinfecting a bathtub and sink, with a focus on spatial and temporal trends to improve our understanding of exposure risks during bleach use. Very high (>10 ppmv) HOCl levels were detected near the bathtub, with lower levels detected further away. Hypochlorous acid concentrations plateaued in the room at a level that depended on distance from the bathtub. This steady-state concentration was maintained until the product was removed by rinsing. Mobile experiments with the analyzer inlet secured to the researcher's face were conducted to mimic potential human exposure to bleach emissions. The findings from mobile experiments were consistent with the spatial and temporal trends observed in the experiments with fixed inlet locations. This work provides insight on effective strategies to reduce exposure risk to emissions from bleach and other cleaning products.

Excessive hypochlorite (ClO - ) is easy to form residues in water, which will seriously endanger human health and environmental pollution. Therefore, it is essential to develop a sensitive fluorescent sensor to detect ClO - in water. Herein, a simple and economical fluorescent probe for the detection of ClO - was designed by highly exfoliated graphite-like carbon nitride (Ex&#95;g-C 3 N 4 ). The results showed that Ex&#95;g-C 3 N 4 had obvious fluorescence quenching effect on ClO - with high selectivity and anti-interference ability, which was feasible for making probes for detecting ClO - in water. Sensing experiments showed that the Ex&#95;g-C 3 N 4 probe had the detection limit of 5.56 nM while the detection range was 0-62 mM in water. Moreover, the fast response time of Ex&#95;g-C 3 N 4 was less than 30 s, illustrating the superior sensitivity. Besides, the fluorescence sensing experiment was carried out in various liquid conditions, which demonstrated that Ex&#95;g-C 3 N 4 probe had outstanding detecting application in natural environment. A portable fluorescent test strip for rapid detecting ClO - was successfully developed. The response of the probe on test strip towards ClO - was investigated, and the detection limit (0.1 μM) is low enough to meet the safety requirements in tap water. Furthermore, the quenching mechanism of Ex&#95;g-C 3 N 4 probe was also discussed., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

A novel near-infrared (NIR) fluorescent probe ( SWJT-9 ) was designed and synthesized for the detection of hypochlorite anion (ClO - ) using a diaminomaleonitrile group as the recognition site. SWJT-9 had large Stokes shift (237 nm) and showed an excellent NIR fluorescence response to ClO - with the color change under the visible light. It showed a low detection limit (24.7 nM), high selectivity, and rapid detection (within 2 min) for ClO - . The new detection mechanism of SWJT-9 on ClO - was confirmed by 1 H NMR, MS spectrum, and the density functional theory (DFT) calculations. In addition, the probe was successfully used to detect ClO - in HeLa cells.

Hypochlorous acid (HOCl) and peroxynitrite (ONOO - ) are two important highly reactive oxygen/nitrogen species, which commonly coexist in biosystems and play pivotal roles in many physiological and pathological processes. To investigate their function and correlations, it is urgently needed to construct chemical tools that can track the production of HOCl and ONOO - in biological systems with distinct fluorescence signals. Here, we found that the coumarin fluorescence of coumarin-benzopyrylium ( CB ) hydrazides (spirocyclic form) is dim, and their fluorescence properties are controlled by their benzopyran moiety via an intramolecular photo-induced electron transfer (PET) process. Based on this mechanism, we report the development of a fluorescent probe CB2-H for the simultaneous detection of HOCl and ONOO - . ONOO - can selectively oxidize the hydrazide group of CB2-H to afford the parent dye CB2 (Abs max /Em max = 631/669 nm). In the case of HOCl, it undergoes an electrophilic attack on the benzopyran moiety of CB2-H to give a chlorinated product CB2-H-Cl , which inhibits the PET process within the probe and thus affords a turn-on fluorescence response at the coumarin channel (Abs max /Em max = 407/468 nm). Due to the marked differences in absorption/emission wavelengths between the HOCl and ONOO - products, CB2-H enables the concurrent detection of HOCl and ONOO - at two independent channels without spectral cross-interference. CB2-H has been applied for dual-channel fluorescence imaging of endogenously produced HOCl and ONOO - in living cells and zebrafish under different stimulants. The present probe provides a useful tool for further exploring the distribution and correlation of HOCl and ONOO - in more biosystems.

Hypochlorous acid is an important active substance involved in a variety of physiological processes in living organisms, while abnormal concentrations of HOCl are strongly associated with a variety of diseases such as cancer, inflammation, atherosclerosis, and Alzheimer's disease. As a result, it's crucial to establish a reliable method for tracking HOCl in vivo in order to investigate its physiological consequences. In this work, we developed a fluorescent probe DFSN with both AIE and ESIPT for imaging HOCl in vivo. DFSN not only has a basic structure and is easy to synthesize, but also has superior performance. The probe responds to HOCl in less than 10 s and has good selectivity and sensitivity to HOCl (DL = 6.3 nM), with a 110-fold increase in fluorescence intensity following response. In addition, DFSN can realize the rapid detection of hypochlorous acid with naked eyes. Moreover, DFSN can be used for the detection of exogenous and endogenous HOCl in RAW264.7 cells, and additionally enables the tracking of HOCl in cancer cells (Hela cells and HepG2 cells). More notably, it has been utilized to image hypochlorous acid in zebrafish with great success. The probe DFSN will be useful in determining the physiological significance of HOCl., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Five fluorescent derivatives of hydroxyphenyl-benzothiazole (HBT) with different methyl positions at the hydroxyphenyl group were synthesized with good yield. Their reactivity and fluorescent response to hypochlorite were carefully studied. It was found that the HBT derivatives with meta-methyl (3-HBT or 5-HBT) showed the highest reactivity to hypochlorite under basic conditions, accompanied by the most efficient fluorescence quenching, whereas HBT derivatives with ortho or para methyl exhibited the least reactivity to hypochlorite. The LUMO and HOMO of 3-HBT were further verified to explain the fluorescence behavior by density functional theory (DFT) calculation. The excellent selectivity of 3-HBT toward hypochlorite against other reactive oxygen species (ROS) was also evaluated under the same conditions. The compounds emit bright green fluorescence in a solid-state, which is convenient for designing sensing devices for hypochlorite in water samples. Thus, the HBT derivatives with meta methyl (3-HBT) were successfully applied to fabricate paper sensors for the quantification of hypochlorite in tap water. Hence, the fluorescent 3-HBT exhibits great promise as a selective and sensitive hypochlorite probe in chemical and biological applications., (Copyright © 2022 Elsevier B.V. All rights reserved.)

In this work, the two pyridylhydrazone-tethered BODIPY compounds ( 2 and 3 ) were synthesized. These compounds aimed to detect hypochlorous acid (HOCl) species via cyclic triazolopyridine formation. The open forms and the resulting cyclic forms of BODIPYs ( 2 , 3 , 4 , and 5 ) were fully characterized by nuclear magnetic resonance, mass spectrometry, infrared spectroscopy, and single-crystal X-ray diffraction. These two probes can selectively detect HOCl through a fluorescence turn-on mechanism with the limit of detections of 0.21 µM and 0.77 µM for compounds 2 and 3 , respectively. This fluorescence enhancement phenomenon could be the effect from C = N isomerization inhibition due to HOCl-triggered triazolopyridine formation. In cell imaging experiments, these compounds showed excellent biocompatibility toward RAW 264.7 murine live macrophage cells and greatly visualized endogenous HOCl in living cells stimulated with lipopolysaccharide., Competing Interests: The authors declare no conflict of interest.

The COVID-19 pandemic has underlined the importance of disinfectants as tools to prevent and fight against coronavirus spreading. An ideal disinfectant and sanitizer must be nontoxic to surface contact, noncorrosive, effective, and relatively inexpensive as it is hypochlorous acid (HOCl). The present work intended to evaluate, on different surfaces, the bactericidal and virucidal effectiveness of nebulized HOCl and test its safety usage in 2D and 3D skin and lung models. Our data showed that HOCl at the dose of 300 ppm did not affect cellular and tissue viability, not their morphology. The HOCl bactericidal properties varies with the surface analyzed: 69% for semi-porous, 96-99.9% for flat and porous. This discrepancy was not noticed for the virucidal properties. Overall, this study showed that nebulized HOCl can prevent virus and bacteria growth without affecting lung and skin tissues, making this compound a perfect candidate to sanitize indoor environments.

Free available chlorine (FAC) is widely used to inactivate viruses by oxidizing viral components, including genomes. It is commonly assumed that hypochlorous acid (HOCl) is the chlorinating agent responsible for virus inactivation; however, recent studies have underscored that minor constituents of FAC existing in equilibrium with HOCl, such as molecular chlorine (Cl 2 ), can influence FAC reactivity toward select organic compounds. This study measures the FAC reaction kinetics with dsDNA and ssDNA extracted from representative bacteriophages (T3 and ϕX174) in samples augmented with chloride. Herein, chloride enhances FAC reactivity toward dsDNA and, to a lesser extent, toward ssDNA, especially at pH < 7.5. The enhanced reactivity can be attributed to the formation of Cl 2 . Second-order rate constants were determined for reactions of ssDNA and dsDNA with HOCl and Cl 2 . DNA chlorination kinetics followed the reactivity-selectivity principle, where the more-reactive nucleophilic species (ssDNA, ∼100× more reactive than dsDNA) reacted less selectively with electrophilic FAC species. The addition of chloride was also shown to enhance the inactivation of bacteriophage T3 (dsDNA genome) by FAC but did not enhance the inactivation of bacteriophage ϕX174 (ssDNA genome). Overall, the results suggest that Cl 2 is an important chlorinating agent of nucleic acids and viruses.

Reduction of HOCl to Cl - by in-situ electrochemical synthesis or ex-situ addition of H 2 O 2 is a feasible method to minimize Cl-DBPs and ClO x - (x = 2, 3, and 4) formation in electrochemical oxidative water treatment systems. This work has investigated the kinetics and mechanism of the reaction between H 2 O 2 and HOCl. The kinetics study showed the species-specific second order rate constants for HOCl with H 2 O 2 (k 1 ), HOCl with HO 2 - (k 2 ) and OCl - with H 2 O 2 (k 3 ) are 195.5 ± 3.3 M -1 s -1 , 4.0 × 10 7 M -1 s -1 and 3.5 × 10 3 M -1 s -1 , respectively. The density functional theory calculation showed k 2 is the most advantageous thermodynamically pathway because it does not need to overcome a high energy barrier. The yields of 1 O 2 generation from the reaction of H 2 O 2 with HOCl were reinvestigated by using furfuryl alcohol (FFA) as a probe, and an average of 92.3% of 1 O 2 yields was obtained at pH 7-12. The second order rate constants of the reaction of 1 O 2 with 13 phenolates were determined by using the H 2 O 2 /HOCl system as a quantitative 1 O 2 production source. To establish a quantitative structure activity relationship, quantum chemical descriptors were more satisfactory than empirical Hammett constants. The potential implications in electrochemical oxidative water treatment were discussed at the end., (Copyright © 2022 Elsevier B.V. All rights reserved.)

A new ratiometric fluorescent probe ( E )-2-(benzo[ d ]thiazol-2-yl)-3-(8-methoxyquinolin-2-yl)acrylonitrile (HQCN) was synthesised by the perfect blending of quinoline and a 2-benzothiazoleacetonitrile unit. In a mixed aqueous solution, HQCN reacts with hydrazine (N 2 H 4 ) to give a new product 2-(hydrazonomethyl)-8-methoxyquinoline along with the liberation of the 2-benzothiazoleacetonitrile moiety. In contrast, the reaction of hypochlorite ions (OCl - ) with the probe gives 8-methoxyquinoline-2-carbaldehyde. In both cases, the chemodosimetric approaches of hydrazine and hypochlorite selectively occur at the olefinic carbon but give two different products with two different outputs, as observed from the fluorescence study exhibiting signals at 455 nm and 500 nm for hydrazine and hypochlorite, respectively. A UV-vis spectroscopy study also depicts a distinct change in the spectrum of HQCN in the presence of hydrazine and hypochlorite. The hydrazinolysis of HQCN exhibits a prominent chromogenic as well as ratiometric fluorescence change with a 165 nm left-shift in the fluorescence spectrum. Similarly, the probe in hand (HQCN) can selectively detect hypochlorite in a ratiometric manner with a shift of 120 nm, as observed from the fluorescence emission spectra. HQCN can detect hydrazine and OCl - as low as 2.25 × 10 -8 M and 3.46 × 10 -8 M, respectively, as evaluated from the fluorescence experiments again. The excited state behaviour of the probe HQCN and the chemodosimetric products with hydrazine and hypochlorite are studied by the nanosecond time-resolved fluorescence technique. Computational studies (DFT and TDDFT) with the probe and the hydrazine and hypochlorite products were also performed. The observations made in the fluorescence imaging studies with human blood cells manifest that HQCN can be employed to monitor hydrazine and OCl - in human peripheral blood mononuclear cells (PBMCs). It is indeed a rare case that the single probe HQCN is found to be successfully able to detect hydrazine and hypochlorite in PBMCs, with two different outputs.

Optically monitoring hypochlorous acid (HClO) in living body favors diagnosis and study of inflammatory diseases. However, this has been hampered by limited strategies to develop highly fluorogenic tools in the deep-penetration near-infrared spectrum. Herein, a near-infrared aza-BODIPY-bisferrocene triad Fc 2 -CBDP that unexpectedly achieves an exceptionally sensitive and selective fluorescence turn-on (>220-fold) response toward HClO through single-ferrocene oxidation and boron-alkynyl hydrolysis cascade is reported. Mechanism insight shows that Fc 2 -CBDP features "enhanced charge transfer"-caused quenching due to intramolecular bisferrocene electronic coupling, which is decoupled in the reaction with HClO. The utility of Fc 2 -CBDP for intracellular HClO imaging is evaluated and, more importantly, in vivo high-contrast deep-tissue imaging of lymphatic inflammation and colitis is realized. This work provides new insights into both HClO and ferrocene chemistry, and extends the reach of fluorogenic strategies in the near-infrared biosensing., (© 2022 Wiley-VCH GmbH.)