Chlorine radicals, including Cl• and Cl2 •–, can be produced in sunlight waters (rivers, oceans, and lakes) or water treatment processes (e.g., electrochemical and advanced oxidation processes). Dissolved organic matter (DOM) is a major reactant with, or a scavenger of, Cl• and Cl2 •– in water, but limited quantitative information exists regarding the influence of DOM structure on its reactivity with Cl• and Cl2 •–. This study aimed at quantifying the reaction rates and the formation of chlorinated organic byproducts produced from Cl• and Cl2 •– reactions with DOM. Laser flash photolysis experiments were conducted to quantify the second-order reaction rate constants of 19 DOM isolates with Cl• (k DOM–Cl•) and Cl2 •– (k DOM–Cl2•–), and compare those with the hydroxyl radical rate constants (k DOM–•OH). The values for k DOM–Cl• ((3.71 ± 0.34) × 108 to (1.52 ± 1.56) × 109 MC –1 s–1) were orders of magnitude greater than the k DOM–Cl2•– values ((4.60 ± 0.90) × 106 to (3.57 ± 0.53) × 107 MC –1 s–1). k DOM–Cl• negatively correlated with the weight-averaged molecular weight (M W) due to the diffusion-controlled reactions. DOM with high aromaticity and total antioxidant capacity tended to react faster with Cl2 •–. During the same experiments, we also monitored the formation of chlorinated byproducts through the evolution of total organic chlorine (TOCl) as a function of chlorine radical oxidant exposure (CT value). Maximum TOCl occurred at a CT of 4–8 × 10–12 M·s for Cl• and 1.1–2.2 × 10–10 M·s for Cl2 •–. These results signify the importance of DOM in scavenging chlorine radicals and the potential risks of producing chlorinated byproducts of unknown toxicity.

This study investigated the role of bromide ions in the degradation of nine pharmaceuticals and personal care products (PPCPs) during the UV/chlorine treatment of simulated drinking water containing 2.5 mgC L natural organic matter (NOM). The kinetics of contributions from UV irradiation and from oxidation by free chlorine, free bromine, hydroxyl radical and reactive halogen species were evaluated. The observed loss rate constants of PPCPs in the presence of 10 μM bromide were 1.6-23 times of those observed in the absence of bromide (except for iopromide and ibuprofen). Bromide was shown to play multiple roles in PPCP degradation. It reacts rapidly with free chlorine to produce a trace amount of free bromine, which then contributes to up to 55% of the degradation of some PPCPs during 15 min of UV/chlorine treatment. Bromide was also shown to reduce the level of HO and to change the reactive chlorine species to bromine-containing species, which resulted in decreases in ibuprofen degradation and enhancement in carbamazepine and caffeine degradation, respectively. Reactive halogen species contributed to between 37 and 96% of the degradation of the studied PPCPs except ibuprofen in the presence of 10 μM bromide ion. The effect of bromide is non-negligible during the UV/chlorine treatment.

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Carbamazepine (CBZ) is one of the pharmaceuticals most frequently detected in the aqueous environment. This study investigated the transformation products when CBZ is degraded by chlorine under ultraviolet (UV) irradiation (the UV/chlorine process). Detailed pathways for the degradation of CBZ were elucidated using ultra-high performance liquid chromatography (UHPLC)-quadrupole time-of-flight mass spectrometry (QTOF-MS). CBZ is readily degraded by hydroxyl radicals (HO) and chlorine radicals (Cl) in the UV/chlorine process, and 24 transformation products were identified. The products indicate that the 10,11-double bond and aromatic ring in CBZ are the sites most susceptible to attack by HO and Cl. Subsequent reaction produces hydroxylated and chlorinated aromatic ring products. Four specific products were quantified and their evolution was related with the chlorine dose, pH, and natural organic matter concentration. Their yields showed an increase followed by a decreasing trend with prolonged reaction time. CBZ-10,11-epoxide (I), the main quantified transformation product from HO oxidation, was observed with a peak transformation yield of 3-32% depending on the conditions. The more toxic acridine (IV) was formed involving both HO and Cl with peak transformation yields of 0.4-1%. All four quantified products together amounted to a peak transformation yield of 34.5%. The potential toxicity of the transformation products was assayed by evaluating their inhibition of the bioluminescence of the bacterium Vibrio Fischeri. The inhibition increased at first and the decreased at longer reaction times, which was in parallel with the evolution of transformation products.

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Wearable electronics play a crucial role in advancing the rapid development of artificial intelligence, and as an attractive future vision, all-in-one wearable microsystems integrating powering, sensing, actuating and other functional components on a single chip have become an appealing tendency. Herein, we propose a wearable thermoelectric generator (ThEG) with a novel double-chain configuration to simultaneously realize sustainable energy harvesting and multi-functional sensing. In contrast to traditional single-chain ThEGs with the sole function of thermal energy harvesting, each individual chain of the developed double-chain thermoelectric generator (DC-ThEG) can be utilized to scavenge heat energy, and moreover, the combination of the two chains can be employed as functional sensing electrodes at the same time. The mature mass-fabrication technology of screen printing was successfully introduced to print n-type and p-type thermoelectric inks atop a polymeric substrate to form thermocouples to construct two independent chains, which makes this DC-ThEG flexible, high-performance and cost-efficient. The emerging material of silk fibroin was employed to cover the gap of the fabricated two chains to serve as a functional layer for sensing the existence of liquid water molecules in the air and the temperature. The powering and sensing functions of the developed DC-ThEG and their interactions were systematically studied via experimental measurements, which proved the DC-ThEG to be a robust multi-functional power source with a 151 mV open-circuit voltage. In addition, it was successfully demonstrated that this DC-ThEG can convert heat energy to achieve a 3.3 V output, matching common power demands of wearable electronics, and harvest biothermal energy to drive commercial electronics (i.e., a calculator). The integration approach of powering and multi-functional sensing based on this new double-chain configuration might open a new chapter in advanced thermoelectric generators, especially in the applications of all-in-one self-powered microsystems.

Microcystin-LR (MC-LR) is a potent hepatotoxin that is often associated with blooms of cyanobacteria. Experiments were conducted to evaluate the efficiency of the chlorine/UV process for MC-LR decomposition and detoxification. Chlorinated MC-LR was observed to be more photoactive than MC-LR. LC/MS analyses confirmed that the arginine moiety represented an important reaction site within the MC-LR molecule for conditions of chlorination below the chlorine demand of the molecule. Prechlorination activated MC-LR toward UV254 exposure by increasing the product of the molar absorption coefficient and the quantum yield of chloro-MC-LR, relative to the unchlorinated molecule. This mechanism of decay is fundamentally different than the conventional view of chlorine/UV as an advanced oxidation process. A toxicity assay based on human liver cells indicated MC-LR degradation byproducts in the chlorine/UV process possessed less cytotoxicity than those that resulted from chlorination or UV254 irradiation applied separately. MC-LR decomposition and detoxification in this combined process were more effective at pH 8.5 than at pH 7.5 or 6.5. These results suggest that the chlorine/UV process could represent an effective strategy for control of microcystins and their associated toxicity in drinking water supplies.

Density functional calculations have been performed to analyze the electronic and mechanical properties of a number of 2D boroxine-linked covalent organic frameworks (COFs), which are experimentally fabricated from di-borate aromatic molecules. Furthermore, the band structures are surprising and show flat-band characteristics which are mainly attributed to the delocalized π-conjugated electrons around the phenyl rings and can be better understood within aromaticity theories. Next, the effects of branch sizes and hydrostatic strains on their band structures are systematically considered within generalized gradient approximations. It is found that their band gaps will start to saturate when the branch size reaches 9. For boroxine-linked COFs with only one benzene ring in the branch, the band gap is robust under compressive strain while it decreases with the tensile strain increasing. When the branch size is equal or greater than 2, their band gaps will monotonously increase with the strain increasing in the range of [-1.0, 2.0] Å. All boroxine-linked COFs are semiconductors with controllable band gaps, depending on the branch length and the applied strain. In comparison with other 2D materials, such as graphene, hexagonal boron nitride, and even γ-graphyne, all boroxine-linked COFs are much softer and even more stable. That is, they can maintain the planar features under a larger compressive strain, which means that they are good candidates in flexible electronics.