Chlorine Incorporation Research Articles

Chloride doping of Co4S3 via methanol solvothermal synthesis for enhanced electrocatalytic nitrate reduction to ammonia

The electrocatalytic reduction of nitrate offers an environmentally friendly means of eliminating hazardous nitrate from wastewater while simultaneously yielding ammonia, a vital fertilizer precursor. Given the importance of nitrate reduction for environmental remediation and the potential of electrochemical methods, the development of a highly efficient and selective electrocatalyst specifically for nitrate reduction to ammonia (NO3ER) is crucial. The Cl-doped Co4S3 (Cl-Co4S3) catalyst was successfully synthesized via a solvothermal method in methanol, aiming to enhance nitrate electroreduction. The incorporation of chlorine was found to modulate the local electronic environment around cobalt atoms, enhancing their reactivity and leading to exceptional catalytic performance for nitrate reduction, leading to exceptional catalytic performance. At an operating potential of −0.61 V vs. the reversible hydrogen electrode, Cl-Co4S3 exhibited remarkable Faradaic efficiency (97.64 ± 2.03 %) and yield rate (0.652 ± 0.012 mmol h−1 cm−2) for ammonia production, surpassing the majority of reported electrocatalysts for NO3ER.

An alternative chlorine-assisted optimization of CdS/Sb2Se3 solar cells: Towards understanding of chlorine incorporation mechanism

The current strategies in the development of Sb2Se3 thin film solar cells involve fabrication and optimization of superstrate and substrate device architectures, with the preferable choice for TiO2 and CdS heterojunction layers. For CdS-based superstrate cells, several studies reported the necessity to apply CdCl2 or other metal halide-based post-deposition treatment (PDT), highlighting improvement of CdS/Sb2Se3 device efficiency. However, the need, effect, and mechanism of such PDT are very often not described. Additionally, the fact that many groups have not succeeded in demonstrating its benefits suggests that this strategy is not straightforward, requiring a deeper understanding towards a more unified concept. The present study proposes an alternative approach to the challenging CdCl2 PDT of CdS in CdS/Sb2Se3 device, involving controllable Cl incorporation in CdS films by systematically varying the concentration of NH4Cl in the CBD precursor solution from 1 to 8 mM. Structural and electrical characterizations are correlated with advanced measurements of Scanning Kelvin Probe, surface photovoltage, and atomic force microscopy to understand the impact of Cl incorporation on the properties of CdS films and CdS/Sb2Se3 devices. The validity of Cl incorporation in the CdS lattice and interdiffusion processes at the CdS-Sb2Se3 interface is confirmed by secondary ion mass spectrometry analysis. It is demonstrated that incorporation of 1 mM of NH4Cl, as a Cl source in CBD CdS, can boost the PCE of CdS/Sb2Se3 by ∼20 %. With this approach, we offer new perspectives on the optimization methodology for Cl-based CdS/Sb2Se3 device processing and complementary understanding of the physiochemistry behind these processes.

Sulfur and chloride co-doped g-C3N4 in photocatalytic peroxymonosulfate activation for enhanced acetaminophen removal: Combination of experiments and DFT calculations

As a green photocatalyst with simple synthesis method, excellent electronic structure, and metal-free properties, the deficiencies of pristine graphitic carbon nitride, such as high electron transfer resistance and narrow energy band gap, inhibit its photocatalytic activity to some extent. In this paper, we synthesized a sulfur and chlorine co-doped g-C3N4 (SCl-CN) capable of efficient photocatalytic activation of peroxymonosulfate (PMS) by calcining a mixture of ammonium chloride and thiourea. By means of DFT calculation, the contribution of sulfur and chlorine to photogenic electron hole separation was discussed. The electrostatic potential of SCl-CN and the adsorption model between SCl-CN and PMS were deduced, and the activation mechanism of PMS was further analyzed. According to the calculated results, the incorporation of sulfur and chlorine tuned the electronic configuration of the material and intensified the interactions between SCl-CN and PMS. It is shown that free and non-free radicals act simultaneously in the SCl-CN/PMS/Vis system. This study provides a new idea for the study of photocatalytic activation of PMS by non-metallic co-doped carbon nitride.

Cl alloying improves thermal stability and increases luminescence in iodine-rich inorganic perovskites.

The inorganic perovskite CsPbI3 shows promising photophysical properties for a range of potential optoelectronic applications but is metastable at room temperature. To address this, Br can be alloyed into the X-site to create compositions such as CsPbI2Br that are stable at room temperature but have bandgaps >1.9 eV - severely limiting solar applications. Herein, in an effort to achieve phase stable films with bandgaps <1.85 eV, we investigate alloying chlorine into iodine-rich triple-halide CsPb(I0.8Br0.2-x Cl x )3 with 0 < x < 0.1. We show that partial substitution of iodine with bromine and chlorine provides a path to maintain broadband terrestrial absorption while improving upon the perovskite phase stability due to chlorine's smaller size and larger ionization potential than bromine. At moderate Cl loading up to ≈5%, X-ray diffraction reveals an increasingly smaller orthorhombic unit cell, suggesting chlorine incorporation into the lattice. Most notably, this Cl incorporation is accompanied by a significant enhancement over Cl-free controls in the duration of black-phase stability of up to 7× at elevated temperatures. Additionally, we observe up to 5× increased steady state photoluminescence intensity (PL), along with a small blue-shift. In contrast, at high loading (≈10%), Cl accumulates in a second phase that is visible at grain boundaries via synchrotron fluorescence microscopy and negatively impacts the perovskite phase stability. Thus, replacing small fractions of bromine for chlorine in the iodine-rich inorganic perovskite lattice results in distinct improvement thermal stability and optoelectronic quality while minimally impacting the bandgap.

The incorporation of chlorine and cosmogenic 36Cl into speleothem carbonate

AbstractCave carbonate mineral deposits (speleothems) contain trace elements that are intensively investigated for their significance as palaeoclimate and environmental proxies. However, chlorine, which is abundant in marine and meteoric waters, has been overlooked as a potential palaeo-proxy, while cosmogenic 36Cl could, in principle, provide a solar irradiance proxy. Here, total Cl concentrations analysed from various speleothems were low (3–14 mg/kg), with variations linked to crystal fabrics. High-resolution synchrotron radiation micro X-ray fluorescence (μ-XRF) trace element mapping showed Cl often associated with Na, Si, and Al. We propose that speleothems incorporate Cl in two fractions: (1) water soluble (e.g., fluid inclusions) and (2) water insoluble and strongly bound (e.g., associated with detrital particulates). However, disparities indicated that alternate unidentified mechanisms for Cl incorporation were present, raising important questions regarding incorporation of many trace elements into speleothems. Our first measurements of 36Cl/Cl ratios in speleothems required large samples due to low Cl concentrations, limiting the potential of 36Cl as a solar irradiance proxy. Critically, our findings highlight a knowledge gap into how Cl and other trace elements are incorporated into speleothems, how the incorporation mechanisms and final elemental concentrations are related to speleothem fabrics, and the significance this may have for how trace elements in speleothems are interpreted as palaeoclimate proxies.

Effect of aluminum and manganese ions on the chlorination of polyamide membranes

The deterioration of separation performance of polyamide membranes after chlorine exposure is a core issue in the application process of membrane technology. The co-existence of metal ions (i.e., Al3+ and Mn2+), which are ubiquitous in different types of water bodies, may complicate the chlorination process. This study systematically evaluated membrane degradation under the simultaneous presence of free chlorine and Al3+ or Mn2+. The membrane water flux after chlorine exposure of 2400 mg/L·h was decreased by 70 %, of which 49 % was resulted from chlorine exposure, attributing to competing effects of the decreased hydrophilicity (contact angle increased from 56° to 68°) and cross-linking degree (Onet/N ratio increased from 1.1 to 2.3). The changes in the physiochemical properties of membranes were due to chlorination and hydrolysis induced by chlorination. The addition of Al3+ or Mn2+ to chlorine resulted in a further reduction of 8 %–13 % for water flux, and a variation as high as 21 % (increase) and 15 % (decrease) for salt rejection compared to virgin membrane at different exposure periods. These cations similarly resulted in a more hydrophobic membrane surface with varied surface charge and the formation of deposition layers. In addition, Al3+ and Mn2+ did not affect chlorination degree (chlorine incorporation). However, Al3+ promoted chlorination-promoted hydrolysis, while Mn2+ inhibited, reflected by the opposite trends of Onet/N.

An Analysis of Successful Hit-to-Clinical Candidate Pairs.

An analysis of 156 published clinical candidates from the Journal of Medicinal Chemistry between 2018 and 2021 was conducted to identify lead generation strategies most frequently employed leading to drug candidates. As in a previous publication, the most frequent lead generation strategies resulting in clinical candidates were from known compounds (59%) followed by random screening approaches (21%). The remainder of the approaches included directed screening, fragment screening, DNA-encoded library screening (DEL), and virtual screening. An analysis of similarity was also conducted based on Tanimoto-MCS and revealed most clinical candidates were distant from their original hits; however, most shared a key pharmacophore that translated from hit-to-clinical candidate. An examination of frequency of oxygen, nitrogen, fluorine, chlorine, and sulfur incorporation in clinical candidates was also conducted. The three most similar and least similar hit-to-clinical pairs from random screening were examined to provide perspective on changes that occur that lead to successful clinical candidates.

Band-gap-engineered mixed-halide perovskite films through vacuum-based deposition approach

Mixed-halide perovskites offer the important characteristic of band-gap tunability, which is essential for tandem solar cells. Herein, the single-source vapor deposition method is reported for MAPbBr2Cl1 (MA (methyl ammonium) = CH3NH3), MAPbBr1.5Cl1.5 and MAPbBr1Cl2 perovskite films utilizing the corresponding mixed-halide perovskite nanoparticles as a source for thermal evaporation. Further, band-gap tuning in vacuum-deposited MAPbBr3 thin films is performed through MACl treatment with successful band-gap tuning from 2.37 to 2.48 eV. The limitation of chlorine (Cl) incorporation into the perovskite structure at room temperature is tackled by MACl treatment of vapor-deposited MAPbBr2Cl1, MAPbBr1.5Cl1.5 and MAPbBr1Cl2 films. The structural properties of MAPbBr3−x Cl x films show a continuous shift in the X-ray diffraction peak toward a higher 2θ value, confirming chlorine incorporation into the perovskite structure. Band-gap tuning in MAPbBr3−x Cl x films, from 2.37 to 2.86 eV, is confirmed by absorption spectroscopy. The mixed-halide perovskite films show an improved microstructure with MACl treatment, as observed from the increased grain size of the films. Further, emission studies show good stability of MAPbBr3−x Cl x films against phase segregation under continuous exposure to 325 nm wavelength illumination of 100 mW/cm2 for more than 60 min. The diminished phase segregation might help in advancing the application of mixed-halide perovskites for reliable optoelectronic devices.

Chlorine retention enables the indoor light harvesting of triple halide wide bandgap perovskites

Chlorine incorporation in triple halide perovskites reduces trap density and enhances the efficiency of indoor light harvesting.

The Design, Structure–Activity, and kinetic studies of 3-Benzyl-5-oxa-1,2,3,4-Tetrahydro-2H-chromeno-(3,4-c)pyridin-8-yl sulfamates as Steroid sulfatase inhibitors

Steroid sulfatase inhibitors block the local production of estrogenic steroids and are attractive agents for the treatment of estrogen-dependent cancers. Inspiration of coumarin-based inhibitors, we synthesized thirty-two 5-oxa-1,2,3,4-tetrahydro-2H-chromeno-(3,4-c)pyridin-8-yl sulfamates, focusing on the substitution derivatives on the adjacent phenyl ring and evaluated their abilities to block STS from human placenta and MCF-7 cells. SAR analysis revealed that the incorporation of chlorine at either meta and/or para position of the adjacent phenyl ring of the tricyclic skeleton enhanced STS inhibition. Di-substitutions at the adjacent phenyl ring were superior to mono and tri-substitutions. Further kinetic analysis of these compounds revealed that chloride-bearing compounds, such as 19m, 19v, and 19w, had KI of 0.02 to 0.11 nM and kinact/KI ratios of 8.8–17.5 nM-1min-1, a parameter indicated for the efficiency of irreversible inhibition. We also used the docking model to illustrate the difference in STS inhibitory potency of compounds. Finally, the safety and anti-cancer activity of selected compounds 19m, 19v, and 19w were also studied, showing the results of low cytotoxicity on NHDF cell line and being more potent than irosustat on ZR-75–1 cell, which was a hormone-dependent cancer cell line with high STS expression.

Incorporation of chlorine in nuclear waste glasses using high-pressure vitrification: Solubility, speciation, and local environment of chlorine

Abstract The solubility, speciation, and local atomic environment of chlorine have been determined for aluminoborosilicate glasses equilibrated with various sources of chlorine (NaCl and PdCl2) at high pressure (0.5–1.5 GPa) and high temperature (1350–1400 °C). The Cl solubility reaches up to 11 mol% in borosilicate glass and appears to be strongly influenced by the concentration of network-modifying cations (Ca and Na) and increases with increasing CaO + Na2O content. The Cl solubility is enhanced in Ca-bearing rather than Na-bearing borosilicate glass, suggesting a higher affinity of chlorine for alkaline-earth cations. Cl K-edge XANES and Cl 2p XPS spectra reveal that chlorine dissolves in glasses only as chloride species (Cl–) and no evidence of oxidized species is observed. Using PdCl2 as a chlorine source leads to a pre-edge signal for PdCl2 in the XANES spectra. The EXAFS simulations show that the Cl– local environment is charge compensated by Na+ or Ca2+ at a distance to first neighbor on the order of 2.7 Å, which is comparable to the observed distances in crystalline chloride compounds. The coordination to charge compensating cation is lower in the case of Ca2+ (~1.1) than Na+ (~4.3).

Chlorine incorporation into SiO2 beyond the chemical equilibrium

The long-haul subsea applications have driven recent development to focus on incorporation of chlorine replacing germania as index adapting component in ultralow loss fibers. We present a method to dope silica glass with a chlorine level above the one expected from thermodynamical equilibrium consideration. Gaseous SiCl4 was used as dopant for the treatment of porous green body prepared by the powder sinter technique (REPUSIL). To be able to optimize the chlorination process steps, the exhaust species of the individual steps had been analyzed using an online process monitoring of exhaust gases via IR spectroscopy. Finally, we could realize a chlorine level of 1.2 wt% Cl with an initial pressure of SiCl4 of 0.1 bar while the calculation of thermodynamic chemical equilibrium predicted only a maximum level of less than 1.0 wt% Cl in SiO2 under those optimized conditions.

Pt nanoenzyme decorated yolk-shell nanoplatform as an oxygen generator for enhanced multi-modality imaging-guided phototherapy

The unsatisfactory efficacy of conventional theranostic agents in ablating tumor poses urgent demands on the development of high-performance integrated theranostic agents utilizing rising nanotechnology. To cope with the existing limitations, here we presented an intelligent nanoplatform based on yolk-shell Fe3O4@polydopamine prepared by mussel-inspired polydopamine chemistry and sacrificial template method as well as subsequent incorporation of Pt nanoparticles and chlorine 6 (Ce6) by in situ reduction and electrostatic adsorption for photodynamic therapy (PDT) and photothermal (PTT). The resultant nanoplatform could effectively deliver photosensitizer Ce6 to tumor sites, then promoting the decomposition of endogenous H2O2 to oxygen, finally achieving enhanced PDT therapy, which is demonstrated by in vitro and in vivo evaluations. Importantly, the generated oxygen bubbles could improve the echogenicity signal of yolk-shell microspheres and thereby provide enhanced ultrasonic (US) signal for imaging solid tumors. Overall, the synergistic combination of magnetic Fe3O4, green polydopamine, catalytic Pt nanoparticles, photosensitive Ce6 enabled the hybrid nanoplatform to have good biocompatibility, efficient tumor accumulation, excellent phototherapy efficiency, high T2-weighted magnetic resonance imaging (MRI) and fluorescence imaging ability (FL). Our study integrating the merits of PDT/PTT and US/MRI/FL into a single nanoplatform will open an avenue of therapeutic strategy toward biomedical applications.

Effect of chlorination on the characteristics of effluent organic matter and the phototransformation of sulfamethoxazole in secondary wastewater

Chlorination is the most common disinfection technology used to treat wastewater effluent discharged into receiving aquatic environments. Effluent organic matter (EfOM) abundant in wastewater is a well-known photosensitizer and it greatly affects phototransformation of antibiotics in water. However, effects of chlorination on the characteristics and photochemical properties of EfOM have not been studied in sufficient detail. This paper investigated effects of chlorination on the characteristics of EfOM, and its impact on the phototransformation of sulfamethoxazole (SMX). Correlations between the EfOM characteristics and steady-state concentrations of reactive intermediates (RI) formed in the system were established. Chlorination was shown to preferentially remove the aromatic protein-like substances in EfOM, and the incorporation of chlorine into followed by the cleavage of the aromatic rings in EfOM molecules led to the formation of low molecular aliphatic organic matter. Both unaltered and chlorinated EfOM promoted the photodegradation of SMX whose rate constant in the wastewater was 1.32–1.65 times higher than that in pH 8 phosphate buffer. However, the rate of SMX photodegradation decreased at higher chlorination concentrations. The photodegradation of SMX was found to proceed through direct photolysis and oxidation by the RIs generated from EfOM and the self-sensitization of SMX. The steady-state concentrations of ·OH, 1O2 and 3EfOM* were 2.15–5.50 × 10−16, 0.42–1.51 × 10−13, and 2.54–5.82 × 10−14 M in unaltered and chlorinated wastewater. The steady-state concentrations of ·OH were well correlated with the removal of the fluorescence regional integration (ΔFRI) for humic-like and soluble microbial products (SMPs), while the photodegradation rate constant of SMX and the steady-state concentration of 1O2 and 3EfOM* showed good correlations with ΔFRI for tryptophan and fulvic-like substances. Six transformation products (TPs) of SMX were identified. These findings provide new insights into the photochemical properties of chlorinated EfOM in the aquatic environments and its roles in the degradation of antibiotics and other trace-level pharmaceuticals.

Iodide vs Chloride: The Impact of Different Lead Halides on the Solution Chemistry of Perovskite Precursors

Controlled perovskite growth from solution is crucial for efficient optoelectronic applications and requires a deep understanding of the perovskite precursor chemistry. The so-called “chlorine route” to lead–iodide perovskite, using PbCl2 or MACl additive as a precursor, is frequently employed to form homogeneous perovskite layers by retarding perovskite crystallization. To understand the role of chlorine-containing lead precursors in solution, we analyze the chemical interaction of PbCl2 and PbI2 precursors with commonly employed solvents (γ-butyrolactone (GBL), N,N-dimethylformamide (DMF), and dimethyl sulfoxide (DMSO)) by combining first-principles simulations and experimental UV–vis spectroscopy in diluted precursor solutions. Ab initio molecular dynamics simulations reveal reduced solvation and an increased free energy barrier of lead-halide bond dissociation of PbCl2 compared to PbI2 with chlorine acting as a stronger ligand, which, in turn, limits the solvent coordination. In contrast to PbI2, PbCl2 absorption spectra lack signatures of high-valent [PbCln]2–n complexes and show low sensitivity on the employed solvent, as confirmed by combined UV–vis and excited-state time-dependent density functional theory (TD-DFT) analysis. Altogether, our data suggest the presence of residual chlorine coordinated to Pb even in the presence of high iodine excess, which may retard the perovskite growth and could also lead to chlorine incorporation within the lead–iodide perovskite crystal.

Front Cover: Re‐Programming and Optimization of a L‐Proline cis‐4‐Hydroxylase for the cis‐3‐Halogenation of its Native Substrate (ChemCatChem 18/2021)

The Front Cover represents the discovery of a novel path during a scientist′s journey towards the biocatalytic incorporation of chlorine into L-proline. In their Communication, A. Papadopoulou et al describe the remodeling of an Fe/αKG hydroxylase into a halogenase utilizing the tools of protein engineering. By employing several rounds of directed evolution, a remodeled halogenase variant with a 98-fold improved apparent kcat/Km was generated. The reprogrammed biocatalyst is the first example of a stereo- and regioselective halogenase derivatizing L-proline at the C3 position and highlights the possibility to successfully access the diverse chemistries of Fe/αKG-dependent dioxygenases to expand the biocatalytic toolbox. More information can be found in the Communication by A. Papadopoulou et al.

FeS2 loading on chlorinated carbon nanotubes surface triggered by sulfur addition and their use as electrocatalyst for ORR

Herein, we report on the synthesis of chlorinated sulfur doped carbon nanotubes (SClCNTs) with excellent oxygen reduction reaction (ORR) activity using the pyrolysis and thermal annealing methods. The morphology and quality of the materials produced were dependent on the synthesis method used. The pyrolysis of acetylene over a solution mixture of dichlorobenzene and thiophene resulted in the poisoning of the catalyst and inhibition of CNT growth. Thermal annealing of ClCNTs in the presence of sulfur at various temperatures (800 °C–1000 °C) resulted in production of SClCNTs with increased density. Materials produced at 800 °C revealed formation of metal particles clustered at the surface of the SClCNTs, whilst those produced at 900 and 1000 °C appeared much cleaner, with evidence of well-defined cube-shaped metal nanoparticles decorated at their surface. XRD and XPS revealed the identity of the metal nanoparticles as pyrite (FeS2). The formation of this pyrite nanoparticles was thought to have been initiated by the presence of defects on the walls of the ClCNTs because of chlorine incorporation. The formation of FeS2 nanoparticles was explained using the vapor-liquid-solid process. The enhanced graphitization of carbon materials due to loading of FeS2 nanoparticles on their surface was confirmed by Raman spectra analysis. The ORR activity was greatly enhanced after addition of sulfur into the ClCNTs, the greatest enhancement was observed for materials produced at 900 °C, annealing temperature.

In-Situ Nano-Auger Probe of Chloride-Ions during CH3NH3PbI3-xClx Perovskite Formation.

Organo-halide perovskite solar cells (PSCs) have emerged as next-generation photovoltaics, owing to their high power-conversion efficiency (PCE), lower production cost, and high flexibility. ABX3-structured methylammonium lead triiodide (CH3NH3PbI3 or MAPbI3) perovskite is a widely studied light-absorbing material in PSCs. Interestingly, a small amount of chlorine incorporation into MAPbI3 increases charge carrier diffusion lengths (from 129 nm to 1069 nm), which enables planar structured PSCs with high PCEs. However, existence of chloride ions in the final perovskite film is still under debate. Contrastingly, few studies reported a negligible amount or absence of chloride ions in the final film, while others reported detection of chloride ions in the final film. Herein, we observed the microstructure and chlorine content of MAPbI3−xClx thin films with increasing temperature via an in-situ nano-Auger spectroscopy and in-situ scanning electron microscopic analysis. The relative precipitation of MAPbI3−xClx films occur at lower temperature and MAPbI3−xClx grains grow faster than those of MAPbI3 grains. Local concentrations of chlorine at intragrain and the vicinity of grain boundary were analyzed to understand the behavior and role of the chloride ions during the microstructural evolution of the MAPbI3−xClx films.

Catalytic C–H Oxidation Enhances Polyethylene Bonding

Selectively adding functionality to commodity plastics is an abiding challenge in polymer science. In this issue of Chem, Hartwig and co-workers describe a selective, catalytic oxidation of polyethylene C–H bonds by using high-valent ruthenium-oxo species. The transformation increases polyethylene’s adhesive properties without significantly modifying its thermal stability or mechanical strength.

Selective, Catalytic Oxidations of C–H Bonds in Polyethylenes Produce Functional Materials with Enhanced Adhesion

Summary The synthesis of functional and processable polyethylenes from simple vinyl monomers with controlled molecular weights and architectures has been a grand challenge of polymer chemistry. Post-polymerization modification of the homopolymers of ethylene is attractive for this purpose but has been hampered by the lack of efficient methods for the selective functionalization of C–H bonds in polyolefins. We report the selective, catalytic oxidation of C–H bonds in commodity polyethylenes with varying molecular weights and architectures. Remarkably, the functionalized materials, even at low levels of functionalization, exhibit physical properties that are absent in unmodified polyolefins, such as strong adhesion and the ability to be painted with common waterborne latex paint. Such observations indicate that selectively modified polyethylenes as described here may help to transform existing commodity plastics into more valuable and potentially more sustainable materials.