Self-assembled micro-flowers of ultrathin Au/BiOCOOH nanosheets photocatalytic degradation of tetracycline hydrochloride and reduction of CO2

Constructing a novel type-Ⅱ ZnO/BiOCOOH heterojunction microspheres for the degradation of tetracycline and bacterial inactivation

A novel ZnO/BiOCOOH microsphere photocatalyst with a type-Ⅱ mechanism was developed for the first time. This strategy was accomplished by immobilizing ZnO onto 3D BiOCOOH microspheres via a single-step hydrothermal synthesis method. The ability to degrade tetracycline (TC) in water under visible light and inactivate bacteria of as-catalyst were analyzed. Among the prepared samples, the ZnO/BiOCOOH composite, with a mass ratio of 40%(Zn/Bi), exhibited the highest photocatalytic activity, which was able to degrade 98.22% of TC in just 90 min and completely eradicated Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) in 48 h, and had potential application in solving water resource environmental pollution. The photoelectric characteristics of the photocatalysts were examined by means of electrochemical impedance spectroscopy (EIS) and photoluminescence (PL) spectroscopy. The findings indicated that the superior photocatalytic performance could be credited to the dissociation of electrons (e-) and holes (h+) in heterojunction composites. Finally, electron paramagnetic resonance (EPR) and capture experiments were conducted to confirm the photocatalytic mechanism of the type-Ⅱ heterojunction. This work provides a new Bi-base photocatalyst for aqueous environmental control.

Environment-friendly organic coordination design of Z-scheme heterojunction N-BOB/BiOIO3 for efficient LED-light-driven photocatalytic and electrochemical performance

As the climate seriously changes, ecofriendly nanomaterials have attracted tremendous interest in renewable energy as photocatalysis. Herein, we designed a new green bismuth-based Z-scheme Bi2O22+ slabs coordinate with 2-aminoterephthalic acid (N-BOB)/BiOIO3 through a simple anion exchange and postsynthetic hydrothermal reaction. FTIR, XRD, FESEM and TEM were employed to characterize the functional groups, structure, and morphologies. UV-DRS revealed the difference in band energy of the N-BOB and N-BOB/BiOIO3. Toward Rh B, TC and CIP degradation tests, 1-N-BOB/BiOIO3 manifests the best photocatalytic degradation (52.3%, 63.6% and 30.2%) efficiency. Also, 1-N-BOB/BiOIO3 possesses high durability in photocatalytic reactions and can inhibit 32.3% of bacterial growth. The results indicate that the synergistic effect between surface amine groups and Z-scheme heterojunction harvests light absorption to increase solar-to-energy (STE) efficiency, accelerate the charge separation, and increases the active sites with high photoredox potential, thus improving the photocatalytic performance. ROS scavenging tests further elucidated that photogenerated holes and hydroxyl radicals play a critical role. In addition, the surface amine groups and benzene rings can be utilized for supercapacitors and other multidisciplinary applications. 0.5 N-BOB/BiOIO3/GO impressively showed 5 times higher specific capacitance than pure GO electrode. We hope this work provides new sight into designing green nanomaterials to relieve environmental pollution and leave behind a clean future for the next generation.

Boosting Exciton Dissociation and Charge Transfer in Triazole-Based Covalent Organic Frameworks by Increasing the Donor Unit from One to Two for the Efficient Photocatalytic Elimination of Emerging Contaminants

As novel photocatalysts, covalent organic frameworks (COFs) have potential for water purification. Insufficient exciton dissociation and low charge mobility in COFs yet restricted their photocatalytic activity. Excitonic dissociation and charge transfer in COFs could be optimized via regulating the donor-acceptor (D-A) interactions through adjusting the number of donor units within COFs, yet relevant research is lacking. By integrating the 1,2,4-triazole or bis-1,2,4-triazole unit with quinone, we fabricated COF-DT (with a single donor unit) and COF-DBT (with double donor units) via a facile sonochemical method and used to decontaminate emerging contaminants. Due to the stronger D-A interactions than COF-DT, the exciton binding energy was lower for COF-DBT, facilitating the intermolecular charge transfer process. The degradation kinetics of tetracycline (model contaminant) by COF-DBT (k = (12.21 ± 1.29) × 10-2 min-1) was higher than that by COF-DT (k = (5.11 ± 0.59) × 10-2 min-1) under visible-light irradiation. COF-DBT could efficiently photodegrade tetracycline under complex water chemistry conditions and four real water samples. Moreover, six other emerging contaminants, both Gram-negative and Gram-positive strains, could also be effectively eliminated by COF-DBT. High tetracycline degradation performance achieved in a continuous-flow system and in five reused cycles in both laboratory and outdoor experiments with sunlight irradiation showed the stability and the potential for the practical application of COF-DBT.

Construction of Built-In Electric Field in TiO2@Ti2O3 Core-Shell Heterojunctions toward Optimized Photocatalytic Performance

A series of Ti₂O₃@TiO₂ core-shell heterojunction composite photocatalysts with different internal electric fields were synthesized using simple heat treatment methods. The synthesized Ti₂O₃@TiO₂ core-shell heterojunction composites were characterized by means of SEM, XRD, PL, UV-Vis, BET, SPV, TEM and other related analytical techniques. Tetracycline (TC) was used as the degradation target to evaluate the photocatalytic performance of the synthesized Ti₂O₃@TiO₂ core-shell heterojunction composites. The relevant test results show that the photocatalytic performance of the optimized materials has been significantly enhanced compared to Ti₂O₃, while the photocatalytic degradation rate has increased from 28% to 70.1%. After verification via several different testing and characterization techniques, the excellent catalytic performance is attributed to the efficient separation efficiency of the photogenerated charge carriers derived from the built-in electric field formed between Ti₂O₃ and TiO₂. When the recombination of electrons and holes is occupied, more charges are generated to reach the surface of the photocatalyst, thereby improving the photocatalytic degradation efficiency. Thus, this work provides a universal strategy to enhance the photocatalytic performance of Ti₂O₃ by coupling it with TiO₂ to build an internal electric field.

Heterojunction material BiYO3/g-C3N4 modified with cellulose nanofibers for photocatalytic degradation of tetracycline

Cellulose nanofibers (CNFs) with large specific surface area and superb adsorption capacity are excellent photocatalyst carriers. In this study, heterojunction powder material BiYO₃/g-C₃N₄ was successfully synthesized for the photocatalytic degradation of tetracycline (TC). The photocatalytic material BiYO₃/g-C₃N₄/CNFs was obtained by loading BiYO₃/g-C₃N₄ on CNFs using electrostatic self-assembly method. BiYO₃/g-C₃N₄/CNFs exhibit a fluffy porous structure and large specific surface area, strong absorption in the visible light range, and the rapid transfer of photogenerated electron-hole pairs. Polymer-modified photocatalytic materials overcome the disadvantages of powder materials that are easy to reunite and difficult to recover. With synergistic effects of adsorption and photocatalysis, the catalyst demonstrated excellent TC removal efficiency, and the composite maintained nearly 90 % of its initial photocatalytic degradation activity after five cycles of use. The superior photocatalytic activity of the catalysts is also attributable to the formation of heterojunctions, and the heterojunction electron transfer pathway was confirmed by experimental studies and theoretical calculations. This work demonstrates that there is great research potential in using polymer modified photocatalysts to improve photocatalyst performance.

Bismuth oxyformate microspheres assembled by ultrathin nanosheets as an efficient negative material for aqueous alkali battery

A negative electrode with high capacity and rate capability is essential to match the capacity of a positive electrode and maximize the overall charge storage performance of an aqueous alkali battery (AAB). Due to the 3-electron redox reactions within a wide negative potential range, bismuth (Bi)-based compounds are recognized as efficient negative electrode materials. Herein, hierarchically structured bismuth oxyformate (BiOCOOH) assembled by ultrathin nanosheets was prepared by a solvothermal reaction for application as negative material for AAB. Given the efficient ion diffusion channels and sufficient exposure of the inner surface area, as well as the pronounced 3-electron redox activity of Bi species, the BiOCOOH electrode offered a high specific capacity (C_s, 229 ± 4 mAh g^-1 at 1 A g^-1) and superior rate capability (198 ± 6 mAh g^-1 at 10 A g^-1) within 0 ∼ -1 V. When pairing with the Ni₃S₂-MoS₂ battery electrode, the AAB delivered a high energy density (E_cell, 217 mWh cm^-2 at a power density (P_cell) of 661 mW cm^-2), showing the potential of such a novel BiOCOOH negative material in battery-type charge storage.

Photoelectrochemical biosensor for DNA demethylase detection based on enzymatically induced double-stranded DNA digestion by endonuclease-exonuclease system and Bi4O5Br2-Au/CdS photoactive material

A novel photoelectrochemical (PEC) biosensor for the detection of DNA demethylase MBD2 was developed based on Bi₄O₅Br₂-Au/CdS photosensitive material. Bi₄O₅Br₂ was firstly modified with gold nanoparticles (AuNPs), following with the modification onto the ITO electrode with CdS to realize the strong photocurrent response as a result of AuNPs had good conductibility and the matched energy between CdS and Bi₄O₅Br₂. In the presence of MBD2, double-stranded DNA (dsDNA) on the electrode surface was demethylated, which triggered the digestion activity of endonuclease HpaII to cleave dsDNA and induced the further cleavage of the dsDNA fragment by exonuclease III (Exo III), causing the release of biotin labeled dsDNA and inhibiting the immobilization of streptavidin (SA) onto the electrode surface. As a results, the photocurrent was increased greatly. However, in the absence of MBD2, HpaII digestion activity was inhibited by DNA methylation modification, which further caused the failure in the release of biotin, leading to the successful immobilization of SA onto the electrode to realize a low photocurrent. The sensor had a detection of 0.3-200 ng/mL and a detection limit was 0.09 ng/mL (3σ). The applicability of this PEC strategy was assessed by studying the effect of environmental pollutants on MBD2 activity.

Strategic insight into enhanced photocatalytic remediation of pharmaceutical contaminants using spherical CdO nanoparticles in visible light region

The sustainable control of pharmaceutical micropollutants in water and wastewater environments is a great challenge in the 21st century. To address these issues, unique CdO nanoparticles (NPs) were synthesized using a facile hydrothermal approach and investigated for photocatalytic control of the antibiotic tetracycline, multidrug-resistant bacteria (MDRB), and total coliform in the wastewater effluent. The NPs were characterized using a range of techniques and it exhibited a spherical-like crystal structure with a mean size of 40 nm. The vibrational stretching mode of 1419 cm^-1 confirmed the formation of Cd-O (M - O). The synthesis protocol formed smoother surfaces and 1.88 eV band gap energy of CdO NPs, inducing excellent photocatalytic activity under visible LED light (blue and white) irradiation. The optimal catalyst dose and pH were 100 mg/L and 8-9, respectively. Blue light proved more effective than white light, resulting in 28% higher efficiency (93 ± 0.47%) in tetracycline degradation than white light under an identical intensity (20 mW/cm²). White light required a four-fold higher light intensity (80 mW/cm²) than blue light to induce comparable photocatalytic MDRB inactivation. Bacterial cell lysis by the photocatalytic treatment was confirmed by transmission electron microscopy (TEM). The used catalyst was easily recovered by 5 min of centrifugation and re-used without any noticeable change in the photocatalytic decomposition. The trapping experiment revealed that the CdO-based NPs contributed primarily to the generation of •O₂^- and •OH radicals (Type I), but the •O₂^- radicals were the dominant reactive oxygen species (ROS) in the photocatalytic process.

Dye recovery with photoresponsive citric acid-modified BiOCOOH smart material: Simple synthesis, adsorption-desorption properties, and mechanisms

Dye recovery is of great significance for a circular economy and sustainable development. However, green recovery strategies without secondary pollution remain a significant challenge. To resolve this issue, a light-responsive smart material (citric acid-modified BiOCOOH (m-BOCH)) was synthesized and applied for dye recovery through adsorption in the dark, and desorption under visible light. With the modification of citric acid, the adsorption level of methylene blue (MB) on m-BOCH (43.4%) was more than six times that of pure BiOCOOH (7.1%). The desorption rate was ∼90% in 120 min under 420 nm light irradiation (there was no desorption for pure BOCH). Further, the adsorption rate was improved to 83.9% and the desorption rate remained stable at an optimal pH of 10.09. Characterization results indicated that carboxyl groups were modified onto the surface of BiOCOOH and served as adsorption sites for MB. Under visible light exposure, the connections between the carboxyl groups and BiOCOOH were damaged, which led to the desorption of MB from the surface of the m-BOCH. The recovered MB exhibited a good staining effect on hepatic stellate cells (HSC) as a fresh dye. The regeneration of m-BOCH was achieved through a moderate hydrothermal process, and the adsorption and desorption capacities were restored to 80.8% and 85.7%, respectively. This research provides a novel environmentally compatible strategy for dye recovery without secondary pollution. This is a very promising treatment technique for dye effluents, which highlights the application of smart materials resource recycling for environmental remediation.

In2S3 nanoflakes grounded in Bi2WO6 nanoplates: A novel hierarchical heterojunction catalyst anchored on W mesh for efficient elimination of toluene

Toxic toluene can be completely oxidized in CO₂ and H₂O with novel three-dimensional (3D) In₂S₃@Bi₂WO₆ hierarchical crystals under visible light. Dense and uniform In₂S₃ nanoflakes are rooted in Bi₂WO₆ nanoplates which intercross with each other and are anchored on a pliable tungsten mesh. This leads to the construction of a stable and porous interface for adsorbing and decomposing target gaseous toluene. The firm contact between In₂S₃ and Bi₂WO₆ initiates the formation of a built-in electric field that helps in channeling the photogenerated electrons in Bi₂WO₆ CB to quench the holes in₂S₃ VB. This results in highly capable electrons and holes, as well as notable increase in the yields of •O₂^- and •OH. 99.7% of toluene is removed and 93.4% is converted to CO₂ when it is degraded in simulated air. This validates its remarkable efficacy in detoxifying toluene.

Facet-dependent CdS/Bi4TaO8Cl Z-scheme heterojunction for enhanced photocatalytic tetracycline hydrochloride degradation and the carrier separation mechanism study via single-particle spectroscopy

An efficient lateral Z-scheme CdS/Bi4TaO8Cl photocatalyst based on the facet-dependent charge separation mechanism and the bandgap structure characteristic was designed.