Radical Capture Research Articles

Preparation of phosphorus-doped mesoporous g-C3N4 and its photocatalytic degradation of tetracycline hydrochloride

P-doped tunnel-shaped carbon nitride is prepared for the first time using phosphonitrilic chloride trimer as P source and SBA-15 as template. The optimization experiments reveal that 20% P doped tunnel-shaped carbon nitride exhibited the best tetracycline hydrochloride (TC) degradation performance under visible light irradiation. The degradation rate constant is 0.23367 min−1, which is around 3 and 30 times faster than that of carbon nitride without P doping (0.07223 min−1) and without SBA-15 as template (0.00078 min−1). Radical capture experiment shows that h+ and ∙O2− are the main reactive radicals in the photocatalytic degradation process. The doped P element can increase the formation rate of ∙O2− and reduce the combination of photogenerated electron-hole pairs due to the presence of electron capture centers. The photocatalytic mechanism of P-doped tunnel-shaped carbon nitride is proposed, providing experimental data and theoretical basis for the practical application in polluted wastewater.

Additive-free synthesis of CuO pricky microspheres with enhanced photocatalytic activity

CuO pricky microspheres have been synthesized without additives by calcination after hydrothermal treatment at [Formula: see text]C for 6[Formula: see text]h. The product was characterized by SEM, TEM, EDS, etc. The unique pricky microspheres were formed with NH4HCO3 and urea as precipitators. Through a series of reaction experiments, the possible formation mechanism of nucleation, growth and secondary growth was proposed. With the assistance of H2O2, the degradation rate of RhB aqueous solution reached 87.16% after 50 min by simulated visible light degradation, which proved the good photocatalytic performance of the CuO pricky microspheres. After four cycles of degradation experiments, the degradation rate of RhB aqueous solution is still above 80%. The radical capture experiments showed that the main active groups in the degradation process were ⋅OH and [Formula: see text], and the mechanism of photocatalytic degradation of Rhb was proposed.

Metal-Controlled Switchable Regioselective Synthesis of Substituted Imidazoles and Pyrroles via Ring Opening/Cyclocondensation with 2H-Azirines.

Catalytic selective annulation of 2H-azirines constitutes a general and modular strategy for the generation of molecular complexity. By using Pd-catalyzed ring opening/heterocyclization associated with direct cleavage of C-N and C-C bonds under appropriate conditions, the formation of imidazoles is presented. Alternatively, the silver-catalyzed radical [3 + 2] cycloannulation of 2H-azirines and 1,3-dicarbonyl compounds provides highly functionalized pyrrole derivatives. Both aliphatic cyclic and acyclic diketones are tolerated with good regioselectivity. Moreover, a radical capture experiment was carried out to determine the proposed mechanism, providing support for a facile radical process.

Flower‐Like Ag6Si2O7/Bi12O17Cl2 p‐n Heterojunctions: Enhanced Photocatalytic Activity and Mechanistic Insight**

AbstractPhotocatalytic degradation is one of the effective ways to remove dyes. Accelerating the separation of photogenerated charge is an effective method for high efficiency visible‐driven catalysis. Here, a potential flower‐like Ag6Si2O7/Bi12O17Cl2 p‐n heterojunctions were successfully prepared. Ag6Si2O7/Bi12O17Cl2 can achieve light capture in a wider range of visible light and provide directional channel for carrier to achieve more efficient space charge separation. The constructed Ag6Si2O7/Bi12O17Cl2 showed excellent photocatalytic removal of 25 mg/L (100 mL) Rhodamine B (RhB) within 20 min. The rate constant for RhB degradation was 0.202 min−1 by Ag6Si2O7/Bi12O17Cl2‐2 which was more than 3.6 times greater than Bi12O17Cl2 (0.055 min−1) and 3.2 times greater than Ag6Si2O7 (0.063 min−1). In addition, the results of free radical capture experiment indicate the ⋅OH plays a leading role in the photocatalytic degradation of RhB and a possible Z‐scheme charge transfer paths and the formation of active species over Ag6Si2O7/Bi12O17Cl2 was proposed to elucidate the reaction mechanism.

Influence of hollow glass microsphere on flame retardancy of ethylene-vinyl acetate/9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide composites

To improve combustion resistance properties of EVA resin, a series of flame-retardant EVA composites were prepared by melt blending 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) with hollow glass microspheres (HGM), abbreviated as EVA/HGM/DOPO. Attributable to the capture of free radicals by DOPO, the promotion of carbonation by HGM and the synergistic effects between HGM and DOPO, EVA/HGM/DOPO composites (4.0 wt% DOPO) exhibit better flame retardant performance, thermal stability, and smoke suppression performance. The limited oxygen index (LOI) results show that 4.0 wt% DOPO is replaced by HGM (EVA-5), the LOI value can be increased to the maximum value of 24.2%, and the vertical combustion reaches the V-2 level. Moreover, the peak of heat release rate (PHRR) value of sample EVA-5 was reduced by 26.5% and 42.8% in the microscale combustion calorimeter (MCC) and cone calorimeter test (CCT) compared to the pure EVA, respectively. The digital photographs and mass loss curves also give positive evidence of the synergistic condensed phase flame-retardant effects between HGM and DOPO. Particularly, the maximum smoke density (Ds, max) of EVA-5 composite is the lowest. The thermogravimetry analysis (TGA) results revealed that HGM/DOPO/EVA samples show higher thermal stability at high temperatures than EVA samples. Furthermore, the addition of HGM improved Young’s modulus compared to EVA. These results suggested the synergetic effect of DOPO and HGM additions, the high efficiency of the proposed strategy and the wide application prospect of the produced EVA flame retardant composite materials.

Z‐scheme ZnSnO3/Bi2WO6 with synergistic polarized electric field for efficient removal of diclofenac

The built‐in electric field induced by piezoelectric effect for suppressing the electron–hole recombination has gained substantial attention recently. In this study, a novel Z‐scheme ZnSnO3/Bi2WO6 (ZSO/BWO) piezo‐photocatalyst with synergistic polarized electric field was synthesized by a simple impregnation method. The optimized 1% ZSO/BWO shows high piezo‐photodegradation efficiency (99.9%, 60 min) and mineralization (42%, 60 min) of diclofenac (DCF) under the synergistic action of ultrasound and light, far exceeding that under sole ultrasound or illumination. The remarkable enhanced piezo‐photocatalytic activity of ZSO/BWO composite was attributed to the increased absorption, improved charge transfer, Z‐scheme heterojunction, and tight surface contact between ZSO and BWO. Moreover, the Z‐scheme mechanism of ZSO/BWO composites is studied in depth and confirmed by the free radical capture experiment and electron spin resonance technology. In addition, the corresponding intermediates of DCF degradation and the possible degradation pathways that were proposed on ZSO/BWO composites were analyzed by liquid chromatography–mass spectrometry and DFT. This work offers an efficient approach for constructing and preparing the highly efficient piezo‐photocatalysts for converting solar and mechanical vibration energies.

Exogenous inorganic anions assisted the transformation and formation of cubic ZnIn2S4 with excellent photocatalytic properties

Inorganic anions have a significant impact on the crystal structure of ZnIn2S4 due to their electronegativity and polarity. Using ZnSO4 and In(NO3)3 as metal precursors, the transformation of ZnIn2S4 from hexagonal to cubic phase and the controllable growth of active crystal plane achieved under simple experimental operation. The crystal structure, surface functional groups, morphology and physicochemical properties of the as-prepared materials were analyzed using modern instrument characterization techniques. In addition, tetracycline hydrochloride (HTC) and Cr(VI) solution were used as target pollutants to evaluate the photocatalytic performance of the materials, and the results showed that the higher relative content ratio of (311) crystal plane made the cubic ZnIn2S4 have better photocatalytic performance, that is, the photocatalytic activity of ZnIn2S4-pHH2SO4 was better, with the removal rates of HTC and Cr (VI) reaching 89.50 % and 98.21 %, respectively. Furthermore, EIS and Tafel curves indicated that ZnIn2S4-pHH2SO4 had a higher separation efficiency of photogenerated electrons and holes, and free radical capture experiments and EPR spectra showed that ·O2- and h+ were the main active species in the photocatalytic degradation of HTC, which establishes the relationship between the structure and properties of the material. The intermediates and possible degradation pathways of HTC were analyzed by 3D-EEM and LC-MS, and the photocatalytic degradation mechanism of HTC by ZnIn2S4-pHH2SO4 was proposed.

High performance visible light response 0D/2D MoS2QDs/BiOCl photocatalyst with synergetic effects of up-conversion and direct Z-scheme heterojunction

Constructing Z-scheme heterojunction has been regarded as a fascinating method to enhance the charge carrier separation rate and retain the high photoredox ability. In this paper, a novel 0D/2D MoS2QDs/BiOCl Z-scheme heterojunction with outstanding visible-light photocatalytic performance has been successfully prepared by a facile one-step strategy. The MoS2QDs with a diameter of 5 nm were uniformly distributed on the surface of BiOCl nanosheets. The optimized MoS2QDs/BiOCl heterojunction showed the most robust CIP and RhB degradation efficiency, which was approximately 32.2 and 44.7 times higher than that of pure BiOCl under visible light irradiation, respectively. This result can be attributed to the synergetic effects of up-conversion and direct Z-scheme heterojunction of the MoS2QDs. The optical property, morphology and surface feature of the catalyst were analyzed through the UV–vis DRS, PL, XRD, Raman, FT-IR, XPS, SEM and TEM. The study of ESR characterization and free radical capture experiments confirmed the Z-scheme heterojunction electron transfer route. Finally, a rational photocatalytic mechanism for pollutants degradation over the MoS2QDs/BiOCl heterojunctions were proposed. This study may provide a reliable strategy for the construction of Z-scheme bismuth-based heterojunction and its potential application in photocatalytic organic pollutants degradation.

Content of polyphenolic compounds, flavonoids, antioxidant activity and antibacterial activity of Jatropha dioica hydroalcoholic extracts against Streptococcus mutans

SummaryStreptococcus mutans has been associated with the development of dental caries. Semidesert bush Jatropha dioica Sessé, found in northern Mexico and widely used as traditional medicine, is known to inhibit pathogenic bacteria. The Folin–Ciocalteu method and free radical capture by DPPH technique were used to determine total polyphenols (TP) and antioxidant activity (AA) respectively. The toxicity and antimicrobial activity of the extract with the highest TP and AA were determined. The highest value of TP (46.06 mg GAE g−1) was determined in the dried root extract. A significant and positive correlation was observed between TP and AA. In the flavonoid quantification, the extract showed the highest value of 4.57 mg QE g−1. The hydroalcoholic extracts did not show toxicity. Hydroxycinnamic acid compounds and methoxyflavones and hydroxybenzoic acid were found in the extracts. These compounds are responsible for antibacterial activity. The minimum inhibitory concentration (MIC) against the Streptococcus mutans was found to be 3.75 mg mL−1.

Mechanistic Investigation of Ni-Catalyzed Reductive Cross-Coupling of Alkenyl and Benzyl Electrophiles.

Mechanistic investigations of the Ni-catalyzed asymmetric reductive alkenylation of N-hydroxyphthalimide (NHP) esters and benzylic chlorides are reported. Investigations of the redox properties of the Ni-bis(oxazoline) catalyst, the reaction kinetics, and mode of electrophile activation show divergent mechanisms for these two related transformations. Notably, the mechanism of C(sp3) activation changes from a Ni-mediated process when benzyl chlorides and Mn0 are used to a reductant-mediated process that is gated by a Lewis acid when NHP esters and tetrakis(dimethylamino)ethylene is used. Kinetic experiments show that changing the identity of the Lewis acid can be used to tune the rate of NHP ester reduction. Spectroscopic studies support a NiII-alkenyl oxidative addition complex as the catalyst resting state. DFT calculations suggest an enantiodetermining radical capture step and elucidate the origin of enantioinduction for this Ni-BOX catalyst.

Developing self-floating N-defective graphitic carbon nitride photocatalyst for efficient photodegradation of Microcystin-LR under visible light

The frequent occurrence of algal blooms in water bodies leads to a significant accumulation of microcystin-LR (MC-LR). In this study, we developed a porous foam-like self-floating N-deficient g-C3N4 (SFGN) photocatalyst for efficient photocatalytic degradation of MC-LR. Both the characterization results and DFT calculations indicate that the surface defects and floating state of SFGN synergistically enhance light harvesting and photogenerated carrier migration rate. The photocatalytic process achieved a nearly 100 % removal rate of MC-LR within 90 min, while the self-floating state of SFGN maintained good mechanical strength. ESR and radical capture experiments revealed that the primary active species responsible for the photocatalytic process was OH. This finding confirmed that the fragmentation of MC-LR occurs as a result of OH attacking the MC-LR ring. LC–MS analysis indicated that majority of the MC-LR molecules were mineralized into small molecules, allowing us to infer possible degradation pathways. Furthermore, after four consecutive cycles, SFGN exhibited remarkable reusability and stability, highlighting the potential of floating photocatalysis as a promising technique for MC-LR degradation.

Synthesis of Dual Z-Scheme CuBi2O4/Bi2Sn2O7/Sn3O4 Photocatalysts with Enhanced Photocatalytic Performance for the Degradation of Tetracycline under Visible Light Irradiation

The dual Z-scheme heterojunction CuBi2O4/Bi2Sn2O7/Sn3O4(CBS) was successfully constructed through in situ growth methods, and its photocatalytic performance was evaluated via degradation of tetracycline hydrochloride under visible light. Out of all samples, CBS-2 exhibited the highest photocatalytic activity, with an apparent rate constant of 2.34, 20.16, and 44.17 times that of Bi2Sn2O7, CuBi2O4, and Sn3O4, respectively. Even after four cycles, the photocatalytic efficiency remained above 85%. The improvement can be attributed to the construction of the Z-scheme heterojunction, which effectively promotes the separation and migration of photogenerated carriers. The possible photocatalytic degradation mechanism of dual Z-scheme heterojunction CBS was deduced based on the theory of free radical capture and energy band.

Synthesis of Z-type spherical B-g-C3N4/Bi2WO6 heterojunctions for enhanced rhodamine B degradation

A spherical B-g-C3N4/Bi2WO6 heterojunction photocatalyst was synthesized using the hydrothermal coprecipitation method. Scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), and ultraviolet–visible diffuse reflectance spectroscopy (DRS) showed that B-g-C3N4 was uniformly dispersed on the Bi2WO6 surface through a strong chemical bond, reducing the energy bandgap of Bi2WO6. The outcomes of the experiment regarding the photocatalytic degradation of rhodamine B (RhB) demonstrated a notable enhancement in the degradation rate for the 1:3 BCN/BWO composite. Specifically, the degradation rate was found to be 76 times greater than that of B-g-C3N4 and 7 times higher than that of Bi2WO6. Furthermore, a photocatalytic degradation mechanism was proposed based on the results of ultraviolet photoelectron spectroscopy (UPS) and free radical capture experiments. The direct Z-type B-g-C3N4/Bi2WO6 heterojunction structure promotes the effective separation of photogenerated carriers and enhances their oxidation-reduction ability.

Enhanced photocatalytic Cr(Ⅵ) reduction over the Z-scheme ZnO/ZnIn2S4 composite under visible light

In the present study, a series of ZnO/ZnIn2S4 photocatalysts with different mass ratios were synthesized for Cr(VI) removal. The surface morphology and chemical composition analysis results showed a well-distributed presence of ZnO nanoparticles on the surface of ZnIn2S4 with self-assembled microporous or mesoporous flower-like structure. The Mott−Schottky diagram indicated compatibility between the band structures of ZnO and ZnIn2S4. Moreover, the maximum Cr(VI) removal efficiency was achieved with 5% ZnO/ZnIn2S4 at pH 4.0, 1.6-fold and 14.5-fold higher than pristine ZnIn2S4 and ZnO, respectively. The pseudo-first-order kinetic model effectively simulated the Cr(VI) removal by ZnO/ZnIn2S4. The enhanced performance of ZnO/ZnIn2S4 was mainly attributed to the interaction between ZnO and ZnIn2S4, resulting in a Z-scheme heterojunction that improved visible-light absorption and charges separation efficiency. Fourier transform infrared and X-ray photoelectron spectroscopy indicated a partial reduction of Cr(VI) to Cr(III). At the same time, TR-PL tests demonstrated longer showed that the photogenerated carrier lifetimes in the compared heterojunction materials were higher than those of ZnO and ZnIn2S4. Free radical capture and electron paramagnetic resonance (EPR) experiments further confirmed that photogenerated electrons (e−) and superoxide radicals (·O2−) were the primary active species in the photoreduction of Cr(VI). These results highlight the potential of ZnO/ZnIn2S4 Z-scheme heterojunction as an efficient photocatalyst for wastewater treatment under visible light irradiation.

Synthesis of doped and porous CuO with boosted light-harvesting features for the photocatalytic mineralization of azo dyes

Porous Ni-doped copper oxide (NCO) photocatalyst has been produced using chemical activation and metal doping techniques. Structural, optical, morphological, and electrical analyses were performed on copper oxide (CO) and porous NCO photocatalysts. The monoclinic-phased, UV/Vis light-triggered, electrically conductive, and porous-surfaced NCO photocatalyst was successfully synthesized, according to a detailed physicochemical investigation. The photo-decomposition abilities of synthetic porous NCO and counterpart CO photocatalysts were investigated and compared using Allura red (AR). According to the photocatalytic study, the porous NCO photocatalyst outperformed its counterpart (CuO) and eliminated 91.4% (adsorption: 18%; decomposition: 79%) of the AR dye in 48 min. Over the porous NCO photocatalyst, the AR dye disintegrated at a rate of 0.024 min−1, which is more than 1.84 times quicker than the rate of disintegration over the CO photocatalyst. The porous NCO photocatalyst, as synthesized, preserved 88% of its photocatalytic activity after five recyclability tests and had remarkable electron-hole separation activity, according to reusability tests and transient-photocurrent measurements. Also, the radical capture experiment suggested that superoxide and hydroxyl are important for porous NCO's photocatalytic activity. According to the findings of this research, the synthesis of ferromagnetic metal-doped and porous semiconductive materials has a great potential for azo dye breakdown, which makes it an efficient, cost-effective, and environmentally acceptable solution for the clean-up of polluted water.

Enhancement of tracking resistance of silicone rubber through charge dissipation and radical capture by fluorosilane-grafted iron oxide

Fluorosilane-grafted iron oxide (F-Fe2O3) was prepared via surface grafting reaction between iron oxide and perfluorooctyltriethoxysilane. The effect of F-Fe2O3 on the tracking resistance (TR) of addition-cured liquid silicone rubber (ALSR) was investigated by the inclined-plane test (IPT), surface potential decay test (SPDT), thermogravimetry (TGA), corona aging test and scanning electron microscopy (SEM). F-Fe2O3 delayed the occurrence of the intensive arc discharge and reduced the number of arc discharges. The corona resistance and TR of ALSR were effectively improved. ALSR/F-Fe2O3 with 0.15 phr F-Fe2O3 content passed the IPT at 4.5 kV, showing an erosion mass of 3.17%. The hydrophobicity and thermal stability of ALSR were also enhanced. The SPDT showed that F-Fe2O3 effectively dissipated charge. The results of thermal stability and corona resistance tests revealed that F-Fe2O3 could capture free radicals generated by the oxidation of methyl side groups of ALSR chains and thus inhibit the thermal degradation of ALSR during the arc discharge. Moreover, the charge dissipation by F-Fe2O3 could diminish the accumulation of charges in ALSR and reduce the damage of charges to the chains during arc discharge. Therefore, the TR of ALSR was enhanced.

Efficiently activating peroxymonosulfate by CoFe-LDHs/MoS2 for rapid degradation of tetracycline

A series of CoFe-LDHs@MoS2-x (x = 0.1, 0.2 and 0.5) samples were successfully synthesized to activate peroxymonosulfate (PMS) for tetracycline (TC) removal. With the introduction of MoS2 could promote the catalytic performance via accelerating the Fe2+/Fe3+ and Co2+/Co3+ cycle. About 98.8 % of TC could be removed over 12 min under a neutral condition in the CoFe-LDHs@MoS2-0.2/PMS system, which was 4.4 times higher than that of CoFe-LDHs/PMS system. The main reactive oxygen species (ROS) in CoFe-LDHs@MoS2-0.2/PMS system were also explored by using quenching and free radical capture experiments. The singlet oxygen (1O2) played a major role for the TC removal. Besides, the decomposition pathways of TC were deduced by UPLC-QTOF/MS, and the stability of catalysts had also been studied. This work provided theoretical and experimental basis for designing and preparation more effective heterogeneous catalysts for PMS activation.

Convenient synthesis of seaweed-derived porous carbon supported Cu-MoO2 composite as high-performance photocatalyst

The development of a simple and convenient method for synthesizing photocatalysts for the degradation of tetracycline remains a great challenge. In this work, a Cu-MoO2@C composite was successfully synthesized by a high-temperature carbonization of ammonium molybdate infiltrated copper alginate aerogel, which was obtained by curing a mixture of sodium alginate and ammonium molybdate using Cu2+ ions. The photocatalytic properties of the prepared composites were evaluated by the degradation of tetracycline. The results showed that the introduction of Cu nanoparticles on the MoO2@C hybrid could significantly improve the catalytic performance, and the degradation rate of tetracycline reached 92.48 % after 60 min light exposure. Tetracycline's estimated photodegradation rate constant, which was 0.04013 min−1, was 5 times more than that of the composite without Cu loading. Furthermore, the reaction mechanism was explored by electron spin resonance (ESR) test and free radical capture reagent. Intermediate products of tetracycline degradation were analyzed by liquid mass spectrometry (LC-MS).

Hydroalcoholic extraction of antioxidant compounds in Japanese grape pseudofruits

The pseudofruit of Japanese grape is rich in sugar and phenolic compounds but little explored for extracting antioxidant compounds. The objective of the study was to extract and evaluate the antioxidant capacity of these pseudofruits harvested at two maturation stages: the development phase (DP) and the mature phase (MP). The pseudofruits were evaluated regarding the centesimal composition and physicochemical characteristics and submitted to extraction with 100% water, 50% ethanol, and 100% ethanol. For the extracts, we determined the phenolic compound content and the antioxidant activity using radical capture methods ABTS and DPPH. Pseudofruits may be considered a good source of dietary fiber, regardless of the maturation stage, proving to be a promising raw material for use in foods. Moreover, pseudofruits in the MP presented an increase in the contents of soluble solids, reducing and non-reducing sugars, and titratable acidity, attributed to the formation of the galacturonic acid during the maturation process. Among the solvent used, extraction with 50% ethanol resulted in a larger phenolic compound content and better antioxidant activity, especially for the pseudofruits in the DP, characterizing them as a vegetable matrix of excellent antioxidant capacity and with potential for application in foods and drugs.

Experimental study on the effect of passive retardation method for thermal runaway mitigation of lithium-ion battery

To delay and suppress the thermal runaway of 18650-type lithium-ion battery, three TRRs (thermal runaway retardants) with various mitigation mechanisms were proposed, and the results were compared to the commonly used thermal management material PA (paraffin). A 200 W heating rod was used to trigger thermal runaway, the flame height, battery temperature, and mass loss were recorded and the suppression effects of different materials were discussed. The results show that PA delays the onset of thermal runaway, however, the higher flame, faster temperature rise, and longer burning time are all a sign of increased danger. TRRH (phenoxy cyclophosphazene) with radical capture effect enables the reduction in flame height and peak temperature by 60.87% and 30.31% compared to a single battery. However, the lack of heat absorption prevents TRRH from reducing the battery surface temperature. TRRM (magnesium hydroxide) and TRRS (sodium acetate trihydrate) have a positive effect on the reaction rate, temperature rise, and flame of the battery. TRRS performs better, and lowering the battery surface temperature to below 400 °C and delaying the onset of thermal runaway by more than 25 min. This study brings novelty to the thermal runaway suppression of lithium-ion batteries, especially from the perspective of pre-filled materials.