Substitution Of Cl Research Articles

Developing a dual-site fluorescent probe for simultaneously discriminating Cys/Hcy and GSH, and visualizing metabolism of Cys to SO2

Biothiols as sulfur-containing active substances -play an important physiological and pathological function in organisms, however their specific markers in situ is a big challenging because they have high reactivity, the nature of the short half-life. Among of which due to their similar structure and properties, in particular, the research on their special physiological function is limited. In our study, we designed two biothiol nucleophilic substitution reaction sites in the benzene ring of SBD-Cl. Because of the conjugate effect of Cl, the para-sulfonic acid activated C was inactivated, the nucleophilic substitution of biothiol and Cl occurred, further, the intramolecular rearrangement occurred between the amino and sulfhydryl of Cys/Hcy, and the yellow fluorescence of SBD was released. However, GSH with large structure could not undergo intramolecular rearrangement, so there was no emission of yellow fluorescence, thus, Cys/Hcy and GSH can be detected distingusihly. In the above, adding SO2 can quench the red emission of benzopyrylium. In this way, we visualized the metabolism process from Cys to sulfur dioxide in the mitochondria with the probe. The above metabolic processes were further studied in zebrafish and tissues, and found the probe imaged tissue to a depth of 80 μm.

Sb3+‐Doping in Cesium Zinc Halides Single Crystals Enabling High‐Efficiency Near‐Infrared Emission

AbstractLuminescent metal halide materials with flexible crystallography/electronic structures and tunable emission have demonstrated broad application prospects in the visible light region. However, designing near‐infrared (NIR) light‐emitting metal halides remains a challenge. Here, an enlightening prototype is proposed to explore the high‐efficiency broadband NIR emission in metal halide systems by incorporating Sb3+ into the Cs2ZnCl4 matrix. Combined experimental analysis and density functional theory calculations reveal a modified self‐trapped excitons model to elaborate the NIR emission. The high photoluminescence quantum yield of 69.9% peaking at 745 nm and large full width at half maximum of 175 nm, along with excellent air/thermal stability, show the unique advantages of lead‐free metal halide Cs2ZnCl4:Sb3+ as the NIR light source. The substitution of Cl− by Br− further enables the red‐shift of emission peak from 745 to 823 nm. The NIR light‐emitting diode device based on Cs2ZnCl4:Sb3+ demonstrates potential as a non‐visible light source in night vision. This study puts forward an effective strategy to design the novel eco‐friendly and high‐efficiency NIR emissive materials and provides guidance for expanding the application scope of luminescent metal halides.

Proton and Water Transfer Pathways in the S2 → S3 Transition of the Water-Oxidizing Complex in Photosystem II: Time-Resolved Infrared Analysis of the Effects of D1-N298A Mutation and NO3- Substitution.

Photosynthetic water oxidation is performed through a light-driven cycle of five intermediates (S0-S4 states) in photosystem II (PSII). The S2 → S3 transition, which involves concerted water and proton transfer, is a key process for understanding the water oxidation mechanism. Here, to identify the water and proton transfer pathways during the S2 → S3 transition, we examined the effects of D1-N298A mutation and NO3- substitution for Cl-, which perturbed the O1 and Cl channels, respectively, on the S2 → S3 kinetics using time-resolved infrared spectroscopy. The S2 → S3 transition was retarded both upon NO3- substitution and upon D1-N298A mutation, whereas it was unaffected by further NO3- substitution in N298A PSII. The H/D kinetic isotope effect in N298A PSII was relatively small, revealing that water transfer is a rate-limiting step in this mutant. From these results, it was suggested that during the S2 → S3 transition, water delivery and proton release occur through the O1 and Cl channels, respectively.

Theoretical investigations of optoelectronic and thermoelectric properties of halide based double perovskite halides: K2TeX6

The double perovskite halides owing to their environmental stability, non-toxicity and remarkable efficiency are emerging as a potential candidate for photovoltaic, solar cell and thermoelectric applications. The tolerance factor and formation energy are computed for structural, and thermodynamic existence in cubic phase. The electron density regulates the charge transfer and bonding. Here we report a comprehensive study of optical, electronic, and thermoelectric properties of K2TeX6 (X = Cl, Br, and I). The electronic band structure analysis reveals indirect semiconducting band gap lying within 3.2–1.68 eV. The substitution of Cl with Br and I reduces band gap with a shift of maximum absorption from ultraviolet to visible region. The optical characteristics are analyzed for the incident energy range 0–5eV by computing dielectric constant, absorption, reflection, and optical loss. Moreover, transport properties are also explained in terms of the exotic variations in the calculated Seebeck coefficient, electronic and thermal conductivities. Figure of merit is elaborated to reveal their potential for thermoelectric applications.

An Amine-Assisted Ionic Monohydride Mechanism Enables Selective Alkyne cis-Semihydrogenation with Ethanol: From Elementary Steps to Catalysis.

The selective synthesis of Z-alkenes in alkyne semihydrogenation relies on the reactivity difference of the catalysts toward the starting materials and the products. Here we report Z-selective semihydrogenation of alkynes with ethanol via a coordination-induced ionic monohydride mechanism. The EtOH-coordination-driven Cl- dissociation in a pincer Ir(III) hydridochloride complex (NCP)IrHCl (1) forms a cationic monohydride, [(NCP)IrH(EtOH)]+Cl-, that reacts selectively with alkynes over the corresponding Z-alkenes, thereby overcoming competing thermodynamically dominant alkene Z-E isomerization and overreduction. The challenge for establishing a catalytic cycle, however, lies in the alcoholysis step; the reaction of the alkyne insertion product (NCP)IrCl(vinyl) with EtOH does occur, but very slowly. Surprisingly, the alcoholysis does not proceed via direct protonolysis of the Ir-C(vinyl) bond. Instead, mechanistic data are consistent with an anion-involved alcoholysis pathway involving ionization of (NCP)IrCl(vinyl) via EtOH-for-Cl substitution and reversible protonation of Cl- ion with an Ir(III)-bound EtOH, followed by β-H elimination of the ethoxy ligand and C(vinyl)-H reductive elimination. The use of an amine is key to the monohydride mechanism by promoting the alcoholysis. The 1-amine-EtOH catalytic system exhibits an unprecedented level of substrate scope, generality, and compatibility, as demonstrated by Z-selective reduction of all alkyne classes, including challenging enynes and complex polyfunctionalized molecules. Comparison with a cationic monohydride complex bearing a noncoordinating BArF- ion elucidates the beneficial role of the Cl- ion in controlling the stereoselectivity, and comparison between 1-amine-EtOH and 1-NaOtBu-EtOH underscores the fact that this base variable, albeit in catalytic amounts, leads to different mechanisms and consequently different stereoselectivity.

Congener-specific partition properties of chlorinated paraffins evaluated with COSMOtherm and gas chromatographic retention indices

Chlorinated Paraffins (CPs) are high volume production chemicals and have been found in various organisms including humans and in environmental samples from remote regions. It is thus of great importance to understand the physical–chemical properties of CPs. In this study, gas chromatographic (GC) retention indexes (RIs) of 25 CP congeners were measured on various polar and nonpolar columns to investigate the relationships between the molecular structure and the partition properties. Retention measurements show that analytical standards of individual CPs often contain several stereoisomers. RI values show that chlorination pattern have a large influence on the polarity of CPs. Single Cl substitutions (–CHCl–, –CH2Cl) generally increase polarity of CPs. However, many consecutive –CHCl– units (e.g., 1,2,3,4,5,6-C11Cl6) increase polarity less than expected from the total number of –CHCl– units. Polyparameter linear free energy relationship descriptors show that polarity difference between CP congeners can be explained by the H-bond donating properties of CPs. RI values of CP congeners were predicted using the quantum chemically based prediction tool COSMOthermX. Predicted RI values correlate well with the experimental data (R2, 0.975–0.995), indicating that COSMOthermX can be used to accurately predict the retention of CP congeners on GC columns.

Comparative Investigation on Chlorobenzene Oxidation by Oxygen and Ozone over a MnOx/Al2O3 Catalyst in the Presence of SO2.

Catalytic oxidation of volatile organic compounds (VOCs) usually encounters complicated components in flue gas causing severe deactivation that restrict its application in specific conditions. The Cl substitution in chlorobenzene further increases poisoning risks. Ozone assistance has unique superiority that can overcome these bottleneck problems. Herein, this study performs a comparative investigation of CB oxidation by oxygen and ozone over a simple Mn/Al2O3 catalyst. CB conversion suffered from slight deactivation in oxygen atmosphere (from 90 to 70%) and more severe deactivation in the presence of SO2 (from 90 to 45%) at 480 °C. Introduction of ozone successfully attained high CB conversion at low temperature (120 °C) with excellent stability and less byproducts. Especially, CB oxidation by ozone maintained its original conversion in the presence of SO2. The deactivation process was simulated by synthesizing several sulfated catalysts. Direct sulfation on Mn/Al2O3 attained more severe deactivation in CB conversion and CO2 formation than sulfation on the Al2O3 support. Ozone with a strong oxidation property promoted the CB oxidation cycle, facilitated desorption of carbonaceous intermediates, and protected MnOx species from severe erosion, thus exhibiting high and stable performance in CB oxidation.

Mixed-halide perovskites solar cells through PbICl and PbCl2 precursor films by sequential chemical vapor deposition

Mixed halide perovskites with chlorine (Cl) content have received significant interest due to better charge transport properties and longer diffusion length compared to pure iodine-based perovskites. The superior properties of Cl-doped perovskites improve solar cell device performance, although the quantification of Cl composition in the perovskite films remain difficult to achieve. Hence, it is difficult to correlate the Cl-quantity with the improved device performance. In this work, we deposited Cl-doped perovskite films through a facile three- and two-step sequential chemical vapor deposition (CVD) where lead halide films were deposited in the first steps of the process and subsequently converted to perovskites. No Cl substitution by iodine was observed during a sequential deposition of lead chloride and lead iodide films which reacted to form a lead chloride iodide phase (PbICl). The substitution of Cl by iodine ions only occurred during the conversion to perovskite phase. Large perovskite grains (greater than 2 µm) were realized when converting a PbI2 film to perovskite compared to chlorine containing lead halide films, contradicting literature. However, Cl doped perovskite solar cells showed improved device efficiencies as high as 10.87% compared to an un-doped perovskite solar cell (8.76%).

A novel red-emission phenothiazine fluorescent protein chromophore based on oxygen‒chlorine bond (O–Cl) formation for real-time detection of hypochlorous acid in cells

Hypochlorous acid (HOCl/ClO−), a reactive oxygen species (ROS), plays an indispensable role in the human immune system. In this article, a novel red-emission phenothiazine fluorescent protein chromophore RFP-Ptz was developed for the detection of HOCl in cells. In the presence of HOCl, the fluorescence signal 610 nm rose gradually and reached its plateau with 15-fold enhancement; the fluorescence quantum yield increased from 0.01 to 0.12. The electrophilic substitution of Cl+ towards phenolic hydroxyl group made the probe exhibited a high selective fluorescence response with a limit of detection (LOD) of 6.76 × 10−7 M over other analyte species and ROS. This recognition mechanism of oxygen‒chlorine bond (O–Cl) formation has confirmed by HRMS. Finally, the RFP-Ptz can be used to response HOCl with low cytotoxicity and good biocompatibility (MTT cytotoxicity assay > 89.5%). The biocompatible RFP-Ptz was successfully applied to the fluorescence imaging of HOCl-related in SGC-7901 cells.

Enhanced ion conduction by enforcing structural disorder in Li-deficient argyrodites Li6−xPS5−xCl1+x

Solid electrolytes with high ionic conductivity and good stability are advantageous over the current liquid electrolytes in rechargeable Li-ion batteries. Argyrodites, Li6PS5X (X ​= ​Cl, Br, or I), with ionic conductivities on the order of mS/cm have attracted tremendous attention. However, the high potential of argyrodites in fast ion conduction is far from being reached. Significant enhancement in ion conduction relies on the fundamental understanding of the contributing factors for fast ion transport. Here, we have systematically prepared highly conductive Li-deficient Li6−xPS5−xCl1+x and examined the influence of Li-deficiency and Cl substitution of S on ion transport using impedance spectroscopy, solid-state NMR, and first-principles calculations. With increased Cl content, the amount of Cl− at S2− (4d) sites increases, forming a dominant 1S3Cl (4d) configuration. In addition, Li+ redistributes with significantly higher mobility. As a result, the activation energy for Li-ion transport decreases, and the conductivity increases to 17 ​mS/cm at 25 ​°C when x equals 0.7 (Li5.3PS4.3Cl1.7). This work not only reports a record ionic conductivity of Cl-containing argyrodites-type fast Li-ion conductors, but also provides new insights into anion disorder-induced ion transport, which has a wide and universal appeal in the development of fast ion conductors and mixed-anion functional materials.

Iridium(III)porphyrin arrays with tuneable photophysical properties.

The photophysical properties of iridium(III) porphyrins complexes with two different axial ligands (Cl(CO) and bipyridine (bpy)) in solution and in cellulose acetate polymer matrix were investigated. The axial ligands substitution was made aiming to evaluate the photophysical properties and the solubility in different solvents. Therefore, dissimilar from the free porphyrin, non-polar solvents (as toluene) favours the quantum yield of iridium(III)porphyrins and ligands with a more extended π-conjugated compound as bpy results in higher yields. Moreover, despite all the porphyrins reveals a negative solvatochromism, the substitution of Cl(CO) ligand by bpy ligand exhibits similar solubility either on non-polar or polar solvents. The observed photoluminescence (PL) at room temperature appears at NIR region in contrast to the previously reported iridium(III) porphyrins. Comparing with free porphyrin H2TTP, the red/NIR PL spectra of the iridium(III)porphyrins (either in solution and in the polymer matrix) reveals remarkable changes. Particularly, a more significative decrease of the red/NIR intensity ratio was detected for [Ir(ttp)(bpy)2] 2 where the maxima of the NIR emission can be adjusted under suitable excitation wavelength.

Oxidative degradation of polycyclic aromatic hydrocarbons in contaminated industrial soil using chlorine dioxide

In situ chemical oxidation can be used to remediate soils contaminated with polycyclic aromatic hydrocarbons (PAHs). However, typical oxidation systems are limited by the acidic environment needed for Fenton reactions, cost and soil effects of activated persulfate, and large pores required for ozone or selected oxidation by permanganate. Chlorine dioxide (ClO2) is an environmentally friendly strong oxidant that is highly reactive with PAHs and produces limited halogenated byproducts. In this study, the kinetics, products, and mechanisms of PAH degradation in industrial soil using ClO2 were investigated. The degradation rate was approximately 84.24% for 0.90 mol kg−1 of ClO2; it increased with ClO2 concentration and temperature had little effect. The degradation process was divided into quick (<1h) and slow (1–48 h) reaction stages. PAH removal was significantly inhibited at higher pH levels, but > 70% of the PAHs were degraded at a typical soil pH of 5.0–7.0. Chemical pretreatment is favorable for PAH removal during ClO2 oxidation and the degradation rate was passively correlated with the desorbing fraction of the PAHs in the soil. Quenching experiments indicated that HOCl was the most important active species responsible for degradation. Among five representative PAH congeners, the degradation products of anthracene, phenanthrene, and benzo[a]pyrene were all oxygenated products. However, the degradation product of pyrene was the Cl substitution product and fluoranthene oxidation produced ring rupture oxygenated transformation and Cl substitution products. The mechanisms of PAH degradation by ClO2 oxidation include one-electron transfer, HOCl as a second oxidant, and •OH participation.

Isoniazid-functionalized Fe3O4 Magnetic Nanoparticles as a Green and Efficient Catalyst for the Synthesis of 3, 4-dihydropyrimidin-2(1H)-ones and their Sulfur Derivatives.

A wide variety of dihydropyrimidins (DHPMs) exhibit pharmacological and biological activities. Herein, an efficient one-pot synthesis of some 3, 4-dihydropyrimidin-2(1H)-one derivatives is reported using Fe3O4 @SiO2-Pr-INH. Recently, several catalysts have been used to improve the Biginellis-reaction. However, some of these catalysts have imperfections. Herein, a convenient method for the synthesis of 3, 4-dihydropyrimidin- 2(1H)-ones and their sulfur derivatives using Fe3O4 @SiO2-Pr-INH is reported. Firstly, the catalyst was synthesized through a simple four-step method. The Fe3O4 MNPs were synthesized using the chemical co-precipitation method, coated with a layer of silica using TEOS, and then functionalized with CPTMS. Subsequently, a nucleophilic substitution of Cl by isoniazid resulted in the formation of the magnetic Fe3O4@SiO2-Pr-INH. After the preparation and characterization of Fe3O4@SiO2-Pr-INH, its catalytic activity was studied in the synthesis of 3, 4-dihydropyrimidin-2(1H)-one derivatives. Following the optimization of the reaction conditions, several 3, 4-dihydropyrimidin-2(1H)-one derivatives were synthesized by the reaction of ethyl acetoacetate or acetylacetone, thiourea or urea and aromatic aldehydes at 80 °C under solvent-free conditions. Isoniazid-functionalized Fe3O4 magnetic nanoparticles (Fe3O4@SiO2-Pr-INH) were prepared using Fe3O4 with silica layer and their surface was modified with isoniazid. They were characterized successfully by infrared spectroscopy, powder X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy and were used for the synthesis of some 3, 4-dihydropyrimidin-2(1H)-one derivatives as catalysts. Aromatic aldehydes with electron-donating or electron-withdrawing groups afforded 3, 4- dihydropyrimidin-2(1H)-ones and their sulfur derivatives in good to excellent yields in short reaction times. Isoniazid-functionalized Fe3O4 magnetic nanoparticles (Fe3O4@SiO2-Pr-INH) were used as an efficient catalyst for Biginelli-type synthesis of 3, 4-dihydropyrimidin-2(1H)-ones and 3, 4-dihydropyrimidin- 2(1H)-thiones in good to excellent yields and short reaction times. It is noteworthy that this method has several advantages such as simple experimental procedures, the absence of solvent, environmentally benign process, stability and reusability of the catalyst.

First-Principles Design of Highly Functional Sulfide Electrolyte of Li10−xSnP2S12−xClx for All Solid-State Li-Ion Battery Applications

Using first-principles density functional theory calculations and ab initio molecular dynamic simulations, we propose Li10-xSnP2S12-xClx as a highly functional solid electrolyte for a Li ion battery. The underlying mechanisms of excellent Li ion conductivity and electrochemical stability are 2-fold: (i) complete replacement of expensive Ge4+ with relatively cheaper Sn4+ species and (ii) partial substitution of Cl– for S2– to form body-centered cubic anionic framework. The rationally controlled doping levels of the halide Cl atoms play a vital role to enlarge Li ion diffusion channel sizes. The unique feature of the electronic structure in Li10-xSnP2S12-xClx ensures its superior electrochemical durability in comparison to the conventional LGPS counterpart. We propose a design principle to crank up the stability even more, as high as 8 V, via forming passivating Li–Cl layers at the Li-metal anode surface. We propose Li10-xSnP2S12-xClx as a promising electrolyte material to facilitate a wide commercialization of all solid-state Li ion batteries.

Synthesis and spectroscopic properties of (N/O) mono- and dispirocyclotriphosphazene derivatives with benzyl pendant arms: study of biological activity.

The Cl replacement reactions of hexachlorocyclotriphosphazene (trimer; N 3 P 3 Cl 6 ) with sodium (N-benzyl)- aminopropanoxides (1 and 2) produced monospiro- (3 and 4), cis-, and trans-dispirocyclotriphosphazenes (13–16). The monospiro tetrakis-aminocyclotriphosphazenes (5–12) were obtained by the Cl substitutions of 3 and 4 with different secondary amines. The cis- (13 and 14) and trans-dispirophosphazenes (15 and 16) possessed 2 chiral P centers, and they were able to present meso and racemic forms, respectively. Moreover, the structures of compounds 5 and 14 were designated using X-ray data. The absolute configuration of compound 14 was found as SR in the solid state. Analytical and spectroscopic data of the phosphazenes were consistent with their suggested structures. Antimicrobial activities of the benzyl-pendant-armed cyclotriphosphazenes were scrutinized against G(+) and G(−) bacteria and yeast strains. The bacterium most affected by the synthesized compounds was Pseudomonas aeruginosa . Minimum inhibitory concentrations and minimal bacterial concentrations were in the range of 125–500 μM. Interactions between the phosphazenes (3–12 and 15) and plasmid DNA were studied with agarose gel electrophoresis. The phosphazene- DNA interaction studies of the cyclotriphosphazenes revealed that phosphazenes 3, 4, and 15 had a substantial effect on supercoiled DNA by cleavage of the double helix.

Density Functional Theory Study of the Initial Stages of Cl-Induced Degradation of α-Cr2O3 Passive Film

The ion exchange and point defect models are two prominent models describing the role of anions, such as chlorides, in the degradation of passive oxide films. Here the thermodynamic feasibility of critical steps of Cl-induced degradation of a hydroxylated α-Cr2O3 (0001) surface, as proposed by these two models, are studied. Both models begin with Cl substitution of surface OH and H2O, which becomes less favorable with increasing Cl coverage. The initial stages of Cl-induced breakdown of the α-Cr2O3 depend on Cl coverage and the presence of O vacancy near the surface as follows: (1) neither Cl insertion (supporting the ion exchange model) nor Cr vacancy formation (supporting the point defect model) is feasible at low Cl coverages except in the presence of O vacancies near the surface, where Cl insertion is thermodynamically feasible even at low coverages, (2) in the absence of O vacancies, Cr vacancy formation becomes feasible from 10/12 ML onwards whereas Cl insertion by exchange with subsurface OH only becomes feasible at full coverage. This implies that at higher coverages Cl-induced degradation first initiatesthrough a vacancy formation mechanism, but both insertion and vacancy formation would be feasible at full coverage.

Control of C3N4and C4N3carbon nitride nanosheets’ electronic and magnetic properties through embedded atoms

In the present work, the effect of various embedded atom impurities on tuning electronic and magnetic properties of C3N4 and C4N3 nanosheets have been studied using first-principles calculations. Our calculations show that C3N4 is a semiconductor and it exhibits extraordinary electronic properties such as dilute-magnetic semiconductor (with H, F, Cl, Be, V, Fe and Co); metal (with N, P, Mg and Ca), half-metal (with Li, Na, K, Al, Sc, Cr, Mn, and Cu) and semiconductor (with O, S, B, C, Si, Ti, Ni and Zn) with the band gaps in the range of 0.3-2.0 eV depending on the species of embedded atom. The calculated electronic properties reveal that C4N3 is a half-metal and it retains half-metallic character with embedded H, O, S, F, B, N, P, Be, Mg, Al, Sc, V, Fe, Ni and Zn atoms. The substitution of Cl, C, Cr and Mn atoms create ferromagnetic-metal character in the C4N3 nanosheet, embedded Co and Cu atoms exhibit a dilute-magnetic semiconductor nature, and embedded Ti atoms result in the system becoming a semiconductor. Therefore, our results reveal the fact that the band gap and magnetism can be modified or induced by various atom impurities, thus, offering effective possibilities to tune the electronic and magnetic properties of C3N4 and C4N3 nanosheets.

Improvement in the thermoelectric performance of highly reproducible n-type (Bi,Sb)2Se3 alloys by Cl-doping.

(Bi,Sb)2Se3 alloys are promising alternatives to commercial n-type Bi2(Te,Se)3 ingots for low-mid temperature thermoelectric power generation due to their high thermoelectric conversion efficiency at elevated temperatures. Herein, we report the enhanced high-temperature thermoelectric performance of the polycrystalline Cl-doped Bi2−xSbxSe3 (x = 0.8, 1.0) bulks and their sustainable thermal stability. Significant role of Cl substitution, characterized to enhance the power factor and reduce the thermal conductivity synergetically, is clearly elucidated. Cl-doping at Se-site of both Bi1.2Sb0.8Se3 and BiSbSe3 results in a high power factor by carrier generation and Hall mobility improvement while maintaining converged electronic band valleys. Furthermore, point defect phonon scattering originated from mass fluctuations formed at Cl-substituted Se-sites reduces the lattice thermal conductivity. Most importantly, spark plasma sintered Cl-doped Bi2−xSbxSe3 bulks are thermally stable up to 700 K, and show a reproducible maximum thermoelectric figure of merit, zT, of 0.68 at 700 K.

Transformation of tetracyclines induced by Fe(III)-bearing smectite clays under anoxic dark conditions

Smectite clays are widely found in subsurface soils and waters. Although they strongly sequester tetracyclines (TCs), little is known about their reactions with these antibiotics under dark anoxic conditions. This study investigated the interactions between TCs and Fe-bearing smectite clays and the influences of environmental factors. Fe-bearing smectite clays were shown to significantly induce the transformation of TCs, including tautomerization, dechlorination, and dehydration. Moreover, the adsorbed TCs reduced the structural Fe(III) in clay particles to structural Fe(II) through electron transfer. The transformation of TCs was more readily induced by smectite clays with a higher rather than a lower Fe content. Tetrahedral Fe(III), and distorted cis- or trans-octahedral Fe(III), were more reactive as an electron acceptor than cis-octahedral Fe(III), as observed on the Mössbauer and FTIR spectra. A lower pH facilitated the adsorption of TCs through dimethyl-amino, amide, and conjugated –OH functional groups and induced a higher rate of TCs transformation. The transformation of chlortetracycline (CTC) was faster than that of oxytetracycline or tetracycline (TTC) due to -Cl substitution. The major transformation CTC products included keto-CTC, epi-CTC, iso-CTC, anhydro-CTC and TTC. Mixtures of these transformed products were found to have a higher acute toxicity than their parent compounds to Photobacterium phosphoreum T3. Our study revealed several previously overlooked interactions between TCs and clay particles that could cause these antibiotics to become unstable in the subsurface environment, with negative effects on the soil-borne microbial community.

Combined in-situ determination of halogen (F, Cl) content in igneous and detrital apatite by SEM-EDS and LA-Q-ICPMS: A potential new provenance tool

Apatite is an accessory mineral that is widely present in most igneous and metamorphic rocks, and is a common detrital component in clastic rocks. As apatite typically incorporates U at sufficient concentrations to enable thermochronometry (e.g., U-Pb, fission track, and (UTh)/He), it is commonly used in detrital provenance studies. Apatite also incorporates a wide range of trace elements at concentrations readily detectable by routine laser ablation-quadrupole-inductively coupled plasma-mass spectrometry (LA-Q-ICPMS) analysis, which can also yield diagnostic provenance information (in particular Sr-Y-REE). However, detrital thermochronometry is of limited use in the case of source terrane(s) with similar crystallisation or cooling histories, while trace elements may yield non-diagnostic provenance information when their source rocks are lithologically similar (e.g., co-genetic granitoids). Here we test a complementary provenance approach which exploits F and Cl substitution into the stoichiometric Z-site in the apatite lattice. Halogen abundance in igneous apatite typically reflects the source melt composition and its subsequent differentiation history, offering potential for provenance discrimination. We apply this method to apatite from bedrock samples of five late- to post-tectonic granitoids in the Grampian and Moine terranes of the Scottish Caledonides, which yield zircon UPb ages of ca. 425–398 Ma. Emplacement over this relatively short time window makes it difficult to discriminate between sediment sourced from these plutons using radiometric dating alone. Apatite F content was measured using an energy dispersive X-ray spectrometer coupled to a scanning electron microscope (SEM-EDS), while Cl and trace element (Sr-Y-REE) abundances were determined by LA-Q-ICPMS. We show that the sampled granitoids can be divided into three groups based on their apatite trace element contents and into three separate groupings based on their F and Cl abundances; all five plutons can thus be discriminated from each other using their integrated trace elements and F-Cl systematics. The granitoid groups identified by their apatite F and Cl contents correlate with those depicted by their modal mineralogy as defined in Quartz-Alkali Feldspar-Plagioclase (QAP) space, with granitoids richer in K-Feldspar (and thus more evolved) yielding apatites with higher F contents. As a pilot study, we also analysed apatite from modern river sediment in the Spey River catchment of the Grampian terrane, for which UPb age data were also acquired. The Spey detrital apatites yield UPb ages that are indistinguishable at the 2σ-level, but their trace element abundances allow three bedrock types to be distinguished: I-type granitoids, S-type granitoids and medium- to high-grade metamorphic rocks. The detrital apatite F and Cl data do not permit such straightforward discrimination, as apatites from S-type granitoid and metamorphic rocks have comparably low Cl contents. However, the detrital apatites with I-type granitoid affinity display significant dispersion in halogen contents (yielding the lowest F abundances with correspondingly the highest Cl contents), which identifies the presence of several more “mafic” I-type granitoid bodies in the Spey catchment. Apatite F and Cl abundances thus have potential for detailed characterisation of the individual components of granitoid suites, including delineating I-type granitoids or the presence of less evolved magmatic bodies among detrital apatites.