Radical Trapping Studies Research Articles

Optimization of Photocatalytic Degradation of Rhodamine B and Indigo Carmine Dyes Using Eco‐Friendly Kaolinite‐Silver Oxide Quantum Dots Nanocomposite Under Sunlight Irradiation

ABSTRACTIn this work, we present a simple method for the pyrofabrication of a new kaolinite‐ silver oxide quantum dots nanocomposite (Kao‐Ag2O/QDs) that is used for the degradation of rhodamine B (RhB) and indigo carmine (IC) dyes. A homogenous combination of kaolinite and silver nitrate was sintered up to 350 °C to create the extremely effective photocatalyst (Kao‐Ag2O/QDs). Various analytical techniques were employed to characterize the Kao‐Ag2O/QDs photocatalyst such as XRD, FTIR, XPS, SEM–EDX, TEM, DTA/TGA, ZP, BET, and UV–Vis DRS. The degradation of RhB and IC dyes through the photocatalyst was carried out in aqueous solutions utilizing several pH dye solutions and sustainable solar energy in atmosphere conditions. The nanocomposite that was prepared had shown an enhanced specific surface area of 53.3005 m2/g, a pore size of 8.1197 nm, and a total pore volume of 0.216 cm3/g. It also displayed an optical band gap energy of 2.9 eV. The study creates that employing the ideal dose of 2000 and 1500 mg/L of the Kao‐Ag2O/QDs photocatalyst at neutral conditions (pH = 7) resulted a maximum degradation effectiveness of RhB and IC of 91.06 and 93.46% after 90 min, respectively. RhB and IC dyes degradation followed Langmuir first‐order kinetics with a rate constant of 0.0217 and 0.0216 min−1 at pH = 7, respectively. The photocatalytic degradation activity for RhB dye is based on hydroxyl radicals (˙OH) and superoxide radicals (˙O2−), while the mechanism of IC removal is based on superoxide radicals (˙O2−), as revealed by scavenger‐based radical trapping studies. A triple reusability study found that the Kao‐Ag2O photocatalyst is highly stable with degradation efficiencies of RhB and IC dyes from the initial 91.09 to 90.04, 88.54, and 86.27% and from the initial 93.46 to 92.8, 91.4 and 89.32%, respectively. The optimal situations for the parameters were identified by the Box–Behnken design (BBD), which was well matched with photocatalytic degradation tests.

Comparative evaluation of α-Bi2O3/CoFe2O4 and ZnO/CoFe2O4 heterojunction nanocomposites for microwave induced catalytic degradation of tetracycline

Two microwave (MW) responsive heterojunction nanocomposite catalysts, i.e., α-Bi2O3/CoFe2O4 (BO/CFO) and ZnO/CoFe2O4 (ZO/CFO), with weight% ratio of 70/30, 50/50, 30/70 were synthesized by sequential thermal decomposition and co-precipitation methods, and used for the degradation of tetracycline (TC) under MW irradiation. The formation of desired catalysts was confirmed through the characterization results of XRD, FT-IR, SEM, VSM, UV-DRS, XPS, BET, etc. Using batch MW experiments, the catalyst dose, pH, initial TC concentration, reaction temperature, and MW power were optimized for TC removal. Under the following reaction conditions: catalyst dose ∼1 g/L, initial TC concentration ∼1 mg/L, temperature ∼90 °C, MW ∼450 W, BO/CFO, and ZO/CFO showed ∼97.55% and 88.23% TC degradation, respectively, after 5 min. The difference in the catalytic response against TC degradation indicated the difference in reflective loss (RL) between these two catalysts. The presence of other competitive anions has affected the removal efficiency of TC due to the scavenging effect. The radical trapping study revealed the significant contribution of TC degradation by hydroxyl radicals in the case of ZO/CFO, whereas for BO/CFO, superoxide (●O2−) and hydroxyl radicals (●OH) both played influential roles. The Z-scheme heterojunction of BO/CFO allowed the formation of ●O2− but the same was inhibited in type-II heterojunction of ZO/CFO due to the valance band position. The dielectric loss, magnetic loss, interfacial polarization, and high electrical conductivity, ‘hotspots’ were produced over the catalyst surface alongside electron-hole separation at heterojunctions, which were responsible for the generation of reactive oxygen species. In addition, Co3+/Co2+ and Fe3+/Fe2+ redox cycles have promoted ●O2− and sulfate radical production during persulfate application. Among the two MW responsive catalysts, BO/CFO could be a potential material for rapidly destroying emerging organic pollutants from wastewater without applying other oxidative chemicals under MW irradiation.

Harnessing potassium peroxymonosulfate activation of WO3/diatomite composites for efficient photocatalytic degradation of tetracycline.

The increasing prevalence of pharmaceutical contaminants in aquatic ecosystems poses profound challenges for both environmental sustainability and public health. Addressing this pressing issue requires the development of innovative, cost-effective, and efficient remediation approaches. Here we report the synthesis of WO3/diatomite composites and their photocatalytic degradation in conjunction with potassium peroxymonosulfate (PMS) activation. By leveraging the synergistic effects, we observe a remarkable degradation of tetracycline, a significant pharmaceutical contaminant, under visible light. Analytically, we have elucidated the driving factors for the enhanced performance, emphasizing the optimal amount of WO3 (10%) in the composite and PMS concentration (3 mM). Specifically, the WO3/diatomite catalyst presents a degradation rate of 80.75% tetracycline (40 mg L-1) after 180 min of visible light irradiation. Also, we elucidate the primary roles of ˙SO4 - radicals in driving the photocatalytic reaction using free radical trapping studies. Our approach not only offers a direct solution to controlling pharmaceutical contamination but also opens new possibilities for advancing the design of composite-based photocatalysts by taking advantage of nature-derived materials.

Low temperature in situ fabrication of NiFe2O4/tetragonal-BiVO4/Bi2MoO6 ternary heterostructure: A conjugated step-scheme multijunction photocatalyst with synergistic charge migration for antibiotic photodegradation and H2 generation

Rational design of novel conjugated step-scheme (S-scheme) multijunction heterostructure with synergistic charge channelization, superior light harvesting efficiency and strong redox ability is a pioneering approach to mimic natural photosynthesis process. Herein, a mild cetyltrimethyl ammoniumbromide (CTAB) assisted one pot reflux synthesis route is designed for in situ integration of metal organic framework (MOF)-derived NiFe2O4 with tetragonal-BiVO4 (t-BiVO4) and γ-Bi2MoO6 to prepare NiFe2O4/t-BiVO4/Bi2MoO6 (NFO/BVO/BMO) ternary composites. Morphologically, fine dispersion of NiFe2O4 (NFO) quantum dots over γ-Bi2MoO6 (BMO) and t-BiVO4 (BVO) nanoplates yielded three types of microscopic heterojunctions among BMO-BVO, BVO-NFO and BMO-NFO phases. The ternary composites displayed important physicochemical attributes including high surface area, strong optical absorption, superior charge mobility and higher excited state lifetime which accounted for its improved photocatalytic activity towards ciprofloxacin degradation (>99% in 90 min) and H2 evolution (1.11 mmolh-1g−1, photon conversion efficiency 18.5%). Kinetics study revealed 12–55 fold higher ciprofloxacin photodegradation activity and 31–41 times higher H2 evolution rate for the ternary composite in comparison to the pure semiconductors. A conjugated S-scheme charge transfer mechanism has been deduced from comprehensive band position analysis and radical trapping study to explain the enhanced photocatalytic activity. This work for the first time demonstrated the rational construction of conjugated S-scheme heterostructures with potential application in water remediation and green H2 production.

Solar light-active S-scheme TiO2/In2S3 heterojunction photocatalyst for organic pollutants degradation

Heterojunction TiO2/In2S3 composite photocatalyst was prepared using a simple low-temperature one-step hydrothermal method. In2S3 nanosheets with a thickness of 1–5 nm were decorated with 20–30 nm TiO2 nanoparticles, forming a stable heterojunction. The electron transfer mechanism and band alignment between TiO2 and In2S3 was studied using X-ray photoelectron spectroscopy and UV–visible spectroscopy, which suggested the formation of an S-scheme heterojunction in TiO2/In2S3 composite. The TiO2/In2S3 composite with a 1:1 mole ratio showed 99.9% photocatalytic degradation of Rhodamine B within 20 minutes of solar light irradiation, which was better than the results for pristine TiO2, pristine In2S3, and their physical mixture, as well as any other previously reported materials of the same kind. The as-prepared TiO2/In2S3 composite showed excellent stability (98% for Rhodamine B) even after five successive reuse cycles. This excellent performance of TiO2/In2S3 was attributed to the S-scheme heterojunction because of an internal electric field, columbic attraction, and band bending. A radical trapping study showed that superoxide radicals O2·- contribute the most to the photocatalytic degradation of Rhodamine B followed by hydroxyl radicals (OH) and holes (hVB+). The use of a low synthesis temperature and a simple, one-step formation method, with no secondary pollutants generated, makes this process an environmentally friendly and sustainable solution for cost-effective wastewater treatment, highlighting its future commercial applications.

Fabrication of Novel g-C3N4@Bi/Bi2O2CO3 Z-Scheme Heterojunction with Meliorated Light Absorption and Efficient Charge Separation for Superior Photocatalytic Performance

Herein, a novel g-C3N4@Bi/Bi2O2CO3 Z-scheme heterojunction was synthesized via simple methods. UV/Vis diffuse reflectance spectroscopy (DRS) revealed that the visible light absorption range of heterojunction composites was broadened from 400 nm to 500 nm compared to bare Bi2O2CO3. The XRD, XPS and TEM results demonstrated that metal Bi was introduced into g-C3N4@Bi/Bi2O2CO3 composites, and Bi may act as an electronic bridge in the heterojunction. Metal Bi elevated the separation efficiency of carriers, which was demonstrated by photocurrent and photoluminescence. The performance of samples was assessed via the degradation of Rhodamine B (RhB), and the results exhibited that g-C3N4@Bi/Bi2O2CO3 possessed notably boosted photocatalytic activity compared with g-C3N4, Bi2O2CO3 and other binary composites. The heterojunction photocatalysts possessed good photostability and recyclability in triplicate cycling tests. Radical trapping studies identified that h+ and •O2- were two primary active species during the degradation reaction. Based on the energy band position and trapping radical experiments, the possible reaction mechanism of the indirect Z-scheme heterojunction was also proposed. This work could provide an effective reference to design and establish a heterojunction for improving the photocatalytic activity of Bi2O2CO3.

Synergic effect of Type II ZnO/BiVO4 magnetic heterostructures for visible light‐driven degradation of bisphenol A and methyl violet

Construction of an effective heterojunction for unimpeded flow of photogenerated charges and their prolonged separation is imperative for environmental photocatalysis. Herein, we have designed an efficient magnetic ZnO/BiVO4 type‐II heterostructure, which was employed for proficient degradation of persistent methyl violet dye with an efficiency of 97.6% in 90 min and a hazardous organic pollutant, namely, bisphenol A. UV‐DRS and photoluminescence studies demonstrated that the fabricated nanocomposite exhibited effective light absorption and prolonged charge separation, thereby resulting in high photocatalytic efficacy under visible light irradiation. The efficacy of developed magnetic ZnO/BiVO4 was also compared with pristine BiVO4 and undoped magnetic ZnO, which indicated that the constructed heterostructure displayed approximately threefold and sixfold activity in contrast with bare BiVO4 and undoped magnetic ZnO nanoparticles, respectively. Radical trapping studies, ESR analysis along with GC‐MS analysis were conducted to elucidate the mechanistic pathway during the photodegradation process. This work provides a rational technical approach and research ideas for photocatalytic degradation of harmful organic pollutants in an environment‐friendly manner by employing energy‐efficient LEDs. Besides, good recyclability of catalyst makes it a promising candidate for large‐scale applications.

Facile low temperature reflux synthesis of Bi self-doped Bi2MoO6 and construction of CaFe2O4/Bi2MoO6 0D QD-2D p-n heterojunction photocatalyst for efficient bisphenol A degradation and Cr(VI) reduction

In this study, a mild reflux route was developed for facile synthesis of Bi-self doped Bi2MoO6 (BMOR) with nanoplate morphology. Microstructural study revealed substitution of Bi5+ ions in the molybdate layer which resulted in partial reduction of Mo6+ to Mo5+ ions and creation of Mo vacancy. The defect engineered BMOR material exhibited improved optical and photoelectrochemical properties compared to its undoped analogue. The BMOR material was subsequently employed as host lattice for construction of CaFe2O4/Bi2MoO6 0D-2D p-n heterojunctions by using an in situ preparative strategy. Well dispersed CaFe2O4 quantum dots over BMOR nanoplates provide a strong interfacial contact conducive for fast charge mobilization. Comprehensive characterization of the composites revealed extended UV–vis response, improved charge carrier separation, prolonged excited state life time and robust radical generation efficiency compared to pure components. The CaFe2O4/Bi2MoO6 composites displayed improved photocatalytic performance for bisphenol A (BPA) degradation (kapp = 0.0132 min−1) and Cr(VI) reduction (kapp = 0.15 min−1) with reaction rates 5–9 times higher than pure components. The involvement of •OH and •O2− radicals in the photodegradation of BPA was confirmed from radical trapping study. The formation of an interfacial p-n heterojunction and a double charge migration mechanism accounted for the improved photocatalytic efficacy of the composite.

Construction of direct Z-scheme g-C3N4/BiYWO6 heterojunction photocatalyst with enhanced visible light activity towards the degradation of methylene blue.

Construction of the Z-scheme heterojunction photocatalyst achieved highly improved photocatalytic ability by its high redox ability of the photoinduced e--h+ pairs. In the study, Z-scheme g-C3N4/BiYWO6 heterojunction photocatalyst is prepared by the single-step hydrothermal method. Further, its photocatalytic ability was assessed by degrading methylene blue under visible light exposure. Particularly, the optimized 30 wt% of g-C3N4 in the g-C3N4/BiYWO6 composite exposes almost complete degradation after 90min, that is ~ 3.0 times greater than the bare BiYWO6 and g-C3N4 with the rate constant value 0.032min-1. Experimentally, the radical trapping studies indicate O2·- and ·OH radicals are playing a vital role in the photocatalytic degradation process. Also, the Z-scheme g-C3N4/BiYWO6 heterojunction photocatalyst exhibits excellent photoelectrochemical property and it is stable after 5 cycles, which indicates its good reusability nature. These enhancements are due to the newly formed heterostructure that facilitates the migration and separation efficiency of the photoproduced e--h+ pairs. Hence, the synthesized Z-scheme g-C3N4/BiYWO6 heterostructure could be an excellent material for wastewater remediation works.

Revealing the charge transfer mechanism in magnetically recyclable ternary g-C3N4/BiOBr/Fe3O4 nanocomposite for efficient photocatalytic degradation of tetracycline antibiotics.

Pharmaceutical compounds in water bodies pose hazards to the ecosystem because of their biotoxicity potency. To eradicate such pharmaceutical compounds, a novel g-CN/BiOBr/Fe3O4 nanocomposites was prepared using a simplistic route and appraised for photodegradation of model tetracycline antibiotics. The g-CN/BiOBr/Fe3O4 nanocomposites exhibited complete tetracycline degradation in just 60min exposure of simulated light irradiation, which is 6 times higher than the g-CN. Under the analogous condition, the tetracycline mineralization ability of the g-CN/BiOBr/Fe3O4 nanocomposites was evaluated to be 78% of total organic carbon removal. The superior photocatalytic performance is ascribed to the extended visible light harvesting ability and enhanced charge carrier separation/transfer with impeded recombination rate in light of effective indirect Z-scheme heterojunction construction. Based on band-edge potential and radical trapping studies indicate that h+>•O2->•OH are the active species responsible for photodegradation. Furthermore, the ternary nanocomposites are magnetically retrievable and recyclable while retaining their stable photocatalytic performance. This work endows a new perspective on the rational design and construction of magnetically recoverable ternary nanocomposite for environmental remediation.

Boosting the photocatalytic performance of Bi2Fe4O9 through formation of Z-scheme heterostructure with In2S3: Applications towards water decontamination

Design of biocompatible nano-heterostructure photocatalyst with broad UV–visible spectrum response and strong redox ability is a promising approach with potential application in micropollutant degradation and pathogen deactivation from aqueous sources. Herein, we have reported the facile fabrication of In2S3/Bi2Fe4O9 (ISxBFO) binary heterostructure by hydrothermally depositing In2S3 nanoparticles (20–40 nm) over Bi2Fe4O9 nanocuboids/nanoplates prepared by combustion synthesis route. In depth characterization study revealed broad spectrum UV–Vis absorption, large interfacial contact, improved charge carrier separation and mobility and a longer excited state life time (4.7 ns) for the ISxBFO heterostructure materials. The integration of In2S3 with Bi2Fe4O9 strongly boosts the optoelectrical and photocatalytic property of pristine Bi2Fe4O9. The ISxBFO heterostructure material exhibited enhanced photocatalytic efficiency for aqueous phase degradation of sulfamethoxazole antibiotics (kapp = 0.06 min−1) and phenyl urea herbicides (kapp = 0.028 min−1) with reaction rates 3–8 times higher than the pure BFO component. The MTT assay experiments confirmed non-cytotoxic nature of treated sulfamethoxazole and diuron solutions. The composite materials also displayed convincing antibacterial behavior towards toxigenic Vibrio cholerae pathogen. Haemagglutination assay study revealed excellent biocompatibility of the binary composite up to 200 mg L−1. Radical trapping study suggested expeditious generation of •OH and •O2− radicals over the ISxBFO surface which is nearly 3.8 and 2.3 times higher than pure BFO and In2S3 respectively. The occurrence of a direct Z-scheme mechanism is inferred from radical trapping and XPS study which accounted for the improved photocatalytic activity and strong radical generation property of the ISxBFO heterostructure material.

A Flower-like Cadmium Cobaltite Architecture for Efficient Degradation of Crystal Violet using a Photo‐Induced Catalytic Method: Insight into the Degradation Pathway

The present study describes the potential use of cadmium cobaltite nano-flower (CCNF) as photocatalyst for the removal of organic dye. The CCNF was prepared through facile, one-pot and costeffective hydrothermal approach. The designed CCNF was found to possess heterogeneous photocatalytic potential against the oxidative degradation of crystal violet dye taken as a model pollutant. The photocatalytic performance of CCNF was evaluated under visible light. The best photocatalytic performance was achieved under visible light with almost complete degradation (87.80%) exhibited within 2 hr of irradiation time. Furthermore, the degradation efficiency of the prepared CCNF was determined in the presence and absence of quenchers and under different pH conditions. The intermediates and final products were investigated by FTIR analysis. The radical trapping studies show that holes (h+), superoxide radicals (•O2ˉ) and hydroxyl radicals (•OH) were identified as the main active species in the reaction. The plausible catalytic mechanism and process were proposed. Finally, this technique can be effortlessly scaled-up for the removal of various polycyclic organic wastes that may be of potential industrial and environmental interests.

Visible Light Photocatalytic Degradation of Sunset Yellow Dye and Industrial Textile Wastewater Using Pd-BiFeO3 Composite

Herein, pristine BiFeO3 and Pd-incorporated BiFeO3 (Pd-BiFeO3) composite were synthesized using hydrothermal synthesis method. The physiochemical and optical properties of the synthesized materials were investigated using numerous techniques. The Pd-BiFeO3 composite significantly enhanced the photocatalytic degradation of sunset yellow (SSY) dye in comparison with the pristine BiFeO3 under visible light irradiation. The enhanced photoactivity was credited to the improved photogenerated charge carrier separation, which was in accordance with the photoelectrochemical measurements. Moreover, the Pd-BiFeO3 composite can be recycled for seven consecutive runs without sufficient loss of photocatalytic activity. Radical trapping studies suggested that the hydroxyl radical (•OH), hydrogen peroxide (H2O2) and hole (h+) were the key reactive oxidizing species. A possible photocatalytic enhancement mechanism of Pd-BiFeO3 composite was stated. Finally, for the first time, the Pd-BiFeO3 composite was also applied towards the effective degradation of industrial textile wastewater.

Facile synthesis of Bi2MoO6-Ag2MoO4 nanocomposite for the enhanced visible light photocatalytic removal of methylene blue and its antimicrobial application

The novel Bi2MoO6-Ag2MoO4 nano-photocatalyst was prepared via facile sono-chemical route. Bi2MoO6-Ag2MoO4 nanocomposite was characterized by high-resolution transmission electron microscopy (HR-TEM), fourier transverse infrared spectroscopy (FTIR), X-ray diffraction (XRD), BET surface area analyzer, photoluminescence (PL), X-ray photoelectron spectroscopy and UV–visible diffuse reflectance spectroscopy. XRD and SAED pattern shows that the particles were crystalline in nature. The formation of heterojunction with tuned band gap of 2.89 eV enhanced the photocatalytic performance of nanocomposite under visible light irradiation. Bi2MoO6-Ag2MoO4 nanocomposite followed the pseudo-first order kinetic and it showed high correlation coefficient value (R2 > 0.95), and it fitted well to the Langmuir–Hinshelwood model. Bi2MoO6-Ag2MoO4 nanocomposite exhibited 91.8% degradation which was highly effective than individual Ag2MoO4 (54.66%) and Bi2MoO6 (58.6%). The radical trapping study reveals the key reactive species involved in photocatalytic degradation process such as .OH. The Bi2MoO6-Ag2MoO4 nanocomposite was found to be highly reusable for the degradation of MB dye by showing 91.8% degradation efficiency after 6th cycle. Antimicrobial activity of the Bi2MoO6-Ag2MoO4 nanocomposite was superior when compared with Ag2MoO4 and Bi2MoO6 nanoparticles. The prepared nanocomposite proved a robust alternative as a solar radiation driven photocatalyst and it also acts as an antimicrobial agent for the treatment of environmental water.

Migratory functionalization of unactivated alkyl bromides for construction of all-carbon quaternary centers via transposed tert-C-radicals

Despite remarkable recent advances in transition-metal-catalyzed C(sp3)−C cross-coupling reactions, there remain challenging bond formations. One class of such reactions include the formation of tertiary-C(sp3)−C bonds, presumably due to unfavorable steric interactions and competing isomerizations of tertiary alkyl metal intermediates. Reported herein is a Ni-catalyzed migratory 3,3-difluoroallylation of unactivated alkyl bromides at remote tertiary centers. This approach enables the facile construction of otherwise difficult to prepare all-carbon quaternary centers. Key to the success of this transformation is an unusual remote functionalization via chain walking to the most sterically hindered tertiary C(sp3) center of the substrate. Preliminary mechanistic and radical trapping studies with primary alkyl bromides suggest a unique mode of tertiary C-radical generation through chain-walking followed by Ni–C bond homolysis. This strategy is complementary to the existing coupling protocols with tert-alkyl organometallic or -alkyl halide reagents, and it enables the expedient formation of quaternary centers from easily available starting materials.

Iridium nanoparticles anchored WO3 nanocubes as an efficient photocatalyst for removal of refractory contaminants (crystal violet and methylene blue)

A series of novel visible light driven Iridium loaded WO3 (Ir/WO3) nanocomposites were successfully synthesized via single step hydrothermal process. The Ir/WO3 nanocomposites were systematically characterized by powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX), transmission electron microscopy (TEM) and UV–vis diffused reflectance spectra (UV–vis DRS) techniques. The WO3 nanocparticles were showed nanocubes-like structure and Ir NPs were anchored on surface of WO3 which was confirmed by SEM and TEM analysis. Optical result indicated that the absorption band edge is positioned in the visible region with band gap energy of WO3, Ir/WO3 (1%), Ir/WO3 (3%) and Ir/WO3 (5%) was 2.87, 2.8, 2.6 and 2.5 eV, respectively. From EDX and XPS analysis, Ir/WO3 nanocomposite contains Ir, W and O elements only. The Ir/WO3 nanocatalysts have been utilized for the photodegradation of crystal violet (CV) and methylene blue (MB) organic pollutants under the visible light irradiation. Compared to pure WO3 and other Ir/WO3 nanocomposites, 3% loaded Ir/WO3 catalyst exhibited superior photocatalytic efficiency towards the degradation of CV and MB. The enhancement of photocatalytic activity was mainly due to the presence of Ir nanoparticles on the surface of WO3 nanocubes preventing the photogeneration electrons-holes pair recombination and the synergistic bonding interaction between Ir NPs and WO3 nanocubes. Various factors such as Ir loading concentration, effect of catalyst, effect of pollutants and stability of the photocatalyst were explained. Furthermore, the possible photocatalytic mechanism of Ir/WO3 catalyst was determined by radical trapping studies. This novel Ir/WO3 nanocomposite proved to an efficient tool catalyst for the organic contaminants abatements.

Explicating charge transfer dynamics in anodic TiO2/ZnO/Zn photocatalytic fuel cell for ameliorated palm oil mill effluent treatment and synchronized energy generation

A sustainable green device known as photocatalytic fuel cell (PFC) uses organics found in wastewater as fuel for the energy conversion. Hence, the effective PFC constructing from anodic TiO2/ZnO/Zn and cathodic TiO2/CuO/Cu was proposed for refractory palm oil mill effluent (POME) removal as well as energy recovery. Among the as-prepared photoanodes, anodic ZnO/Zn coated with 2 layers of TiO2 (TZ2) showed high crystallinity, low band gap, appropriate hydroxyl group and interfacial charge carrier separation that enable its superior photoactivity, which presented an enhancement of 3.67 times and 4.64 times in photocatalytic and energy performance over pristine ZnO/Zn. Among several examined influential parameters, the electrolyte concentration was the most influential factor due to its provision of OH− ions that can capture the photogenerated holes to enhance the electron-hole pair separation. The optimized system reached 90 % of COD removal efficiency of POME. Furthermore, an open circuit voltage (Voc), short circuit current density (Jsc) and power density (Pmax) of 1173 mV, 0.2652 mA cm-2 and 0.0734 mW cm-2 was achieved, respectively. The photoanode maintained high recyclability performance after repeated experimental cycles. In-depth mechanism investigations confirmed that the marked cell performance was attributed to not only the accelerated charge carrier separation due to deposition of TiO2 onto ZnO/Zn as verified by the photoelectrochemical tests, but also the dominant active species, including hydroxyl (OH) radicals and hole (h+) found in the radical trapping study. The assessed electrical energy efficiency of PFC using anodic TZ2 manifested reduced energy consumption of 1.77 times as compared to PFC using pristine anodic ZnO. The toxicity experiments via wild algae indicated reduction in toxicity. This work advances the practical application of promising PFC for environmental protection and energy recovery.

Fabrication of nanocomposite photocatalyst CuBi2O4/Bi3ClO4 for removal of acid brown 14 as water pollutant under visible light irradiation.

In the present study, CuBi2O4/Bi3ClO4 nanocomposites have been fabricated via an improved Pechini sol-gel process using the mixtures of various gelling agents and polybasic acids. This work shows that by controlling the reaction conditions such as kind of polybasic acids, gelling agents, pH and mole ratio of polybasic acid to total metals, the CuBi2O4/Bi3ClO4 nanocomposites with ultrafine sphere-like, irregular polyhedral-like, plate-like and cubic-like morphologies were prepared. The phase, elemental composition, morphology and optical characteristics of as-synthesized CuBi2O4/Bi3ClO4 nanostructures were analyzed utilizing UV-Vis, FESEM, TEM, HRTEM, FT-IR, XRD, TOC and EDS techniques. Furthermore, the CuBi2O4/Bi3ClO4 nanocomposites exhibited excellent TOC removal (75%) and photocatalytic activity (92%) to photodegradation of acid brown 14 azo dye as water pollutants under visible light irradiation. The excellent degradation activity of CuBi2O4/Bi3ClO4 photocatalyst can be attributed to the strong visible light absorption, high charge separation efficiency, fine particle size distribution and proper band gap of the nanocomposite. In addition, the reliable photocatalytic mechanism was discussed on the basis of the radical trapping study, which revealed the h+ and O2- radicals were the prevailing active species in the photocatalytic process.

Visible Light-Induced Radical Mediated DNA Damage.

Light-responsive compounds have been used to manipulate biological systems with spatial and temporal control of the event of interest. Illumination of alkylcobalamins with green light (>500nm) produces carbon-centered radicals, which have been demonstrated to effectively cause DNA damage. Molecules that cause DNA and RNA strand scission are useful for studying polynucleotide structure and the binding of small molecules and proteins to polynucleotides. Most molecules that cause DNA damage in a light-dependent manner require high energy, short wavelength ultraviolet light, which is readily absorbed by nucleotide bases causing damage to the polynucleotides. Therefore, using alkylcobalamins is advantageous for causing strand scission of polynucleotides, because they are activated by light wavelengths that are not absorbed by nucleotide bases. Green-light illumination of methylcobalamin effectively causes DNA strand scission based on gel mobility assays. This cleavage is due to the generation of carbon-centered radicals based on the results of a radical trapping study. In addition, synthesis of an alkylcobalamin with a DNA binding moiety, spermine, improves DNA cleavage efficacy by an order of magnitude in comparison with methylcobalamin.

Microwave‐Assisted Radical Insertion/Cyclization of Vinyl Isocyanides for the Synthesis of Multi‐Substituted Isoquinolines

AbstractA convenient microwave‐assisted method for the synthesis of multi‐substituted isoquinolines from the radical insertion/cyclization reaction of vinyl isocyanides with a C(sp3)‐H bond adjacent to a heteroatom has been described. The methodology presented here achieves wide substrate scope and good to excellent yields. A radical mechanism is proposed, which is supported by kinetic isotope effect (KIE) studies, radical trapping studies and Hammett plot analysis.