Intrinsically morphological effect of perovskite BaTiO3 boosting piezocatalytic uranium extraction efficiency and mechanism investigation

Heterogeneous piezo-self-Fenton material design: an intersecting solution for pollutant degradation and tumor therapy

Heterogeneous piezo-self-Fenton (EPSF), an integration of piezocatalysis and heterogeneous Fenton reactions, forms the foundation for efficient redox interfacial reactions in complex environments. The significant generation of reactive oxygen species (ROS) during the catalytic process and the mechanical energy-driven nature of the EPSF process provide distinct advantages in environmental remediation and biomedical applications. Numerous studies on EPSF catalysts have emerged in recent years across these fields. However, the construction approaches and design strategies for EPSF catalysts in various application scenarios remain unclear. This review synthesizes and analyzes studies on organic pollutant degradation and targeted tumor therapy. Based on the elucidation of redox processes in EPSF catalysis, the catalysts are categorized according to structural features, clarifying common material systems across different fields. The factors influencing EPSF catalytic performance are subsequently outlined, followed by an evaluation of corresponding enhancement strategies. Finally, design strategies for EPSF catalysts across applications are analyzed, emphasizing the commonalities and distinctions in catalyst design for different fields. Insights are provided to inform future catalyst development.

Piezoelectric biomaterials for providing electrical stimulation in bone tissue engineering: Barium titanate

With the increasing clinical demand for orthopedic implants, bone tissue engineering based on a variety of bioactive materials has shown promising applications in bone repair. And various physiological cues, such as mechanical, electrical, and magnetic stimulation, can influence cell fate and participate in bone regeneration. Natural bone has a piezoelectric effect due to the non-centrosymmetric nature of collagen, which can aid in cell adhesion, proliferation and differentiation, and bone growth by converting mechanical stimuli into electrical stimuli. Piezoelectric materials have the same piezoelectric effect as human bone, and they are able to deform in response to physiological movement, thus providing electrical stimulation to cells or damaged tissue without the need for an external power source. Among them, Barium titanate (BaTiO3) is widely used in tumor therapy, tissue engineering, health detection and drug delivery because of its good biocompatibility, low cytotoxicity and good piezoelectric properties. This review describes the piezoelectric effect of natural bone and the characteristics of various types of piezoelectric materials, from the synthesis and physicochemical characteristics of BaTiO3 and its application in biomedicine. And it highlights the great potential of BaTiO3 as piezoelectric biomaterials in the field of bone tissue engineering in anticipation of providing new ideas and opportunities for researchers. The translational potential of this article: This review systematically discusses barium titanate, a bioactive material that can mimic the piezoelectric effect of natural bone tissue, which can intervene in the regenerative repair of bone by providing a sustained electrical microenvironment for bone repair scaffolds. This may help to solve the current problem of poor osteogenic properties of bioactive materials by utilizing barium titanate.

Optimizing 3d electronic structure of LaCoO3 based on spin state tuning for enhancing photo-Fenton activity on tetracycline degradation

The water pollution caused by the abuse of antibiotics has significant harmful effects on the environment and human health. The photo-Fenton process is currently the most effective method for removing antibiotics from water, but it encounters challenges such as inadequate response to visible light, low yield and utilization of photogenerated electrons, and slow electron transport. In this study, spin state regulation was introduced into the photo-Fenton process, and the spin state of Co3+ was regulated through Ce displacement doping. The intermediate-spin state Ce-LaCoO3 could degrade 91.6 % of tetracycline within 120 min in the photo-Fenton system, which is 15.2 % higher than that of low-spin state LaCoO3. The improved degradation effect is attributed to the reasons that Ce-LaCoO3 in the intermediate-spin state have lower band gap, better charge transfer ability, and stronger adsorption capacity of H2O2, which can accelerate the redox cycle of Co2+/Co3+ and promote the generation of ·OH. This study presents a unique strategy for synthesizing efficient photo-Fenton materials to treat antibiotic wastewater effectively.

Defect Engineering Enhancing Piezoelectric Catalytic Activity of Covalent Organic Framework Matrix Composites for Uranium Removal

Piezoelectric catalysis is an emerging green strategy, but the existing piezoelectric heterostructures are not sufficient in performance for catalytic reduction of low-reduction potential uranium under harsh conditions. This study innovatively employs a defect heterogeneous engineering strategy, wherein covalent organic frameworks (COFs) are grown in situ on the surface of zinc oxide (ZnO) via Schiff base reactions, and defects are introduced into the COF shell layer via imine exchange reactions to construct D-COF@ZnO for piezoelectric catalytic uranium removal. The comprehensive study shows that defect heterogeneous engineering increases the asymmetry induced polarization of the material to promote charge redistribution, and thus significantly improves the activity of piezoelectric catalysis. In addition, defect engineering optimizes the nanosize of D-COF@ZnO to expose a richer array of active sites, resulting in ultra-fast U(VI) removal kinetics and ultra-high removal capacity. In the actual nuclear wastewater settings, D-COF@ZnO demonstrates outstanding selective removal efficacy for uranium, manifesting its considerable application potential and efficiency superiority. This strategy holds profound implications for facilitating the application of piezoelectric catalytic technology in environmental protection domains such as uranium removal, manifesting its considerable potential and value.

Preparation and Piezocatalytic Performance of γ-AlON Particles for Dye-Pollutant Degradation Under Ultrasonic Vibration

Piezocatalytic materials have attracted widespread attention in the fields of clean energy and water treatment because of their ability to convert mechanical energy directly into chemical energy. In this study, γ-AlON particles synthesised using carbothermal reduction and nitridation (CRN) were used for the first time as a novel piezocatalytic material to degrade dye solutions under ultrasonic vibration. The γ-AlON particles exhibited good performance as a piezocatalytic material for the degradation of organic pollutants. After 120 min under ultrasonic vibration, 40 mg portions of γ-AlON particles in 50 mL dye solutions (10 mg/L) achieved 78.06%, 67.74%, 74.29% and 64.62% decomposition rates for rhodamine B (RhB), methyl orange (MO), methylene blue (MB) and crystal violet (CV) solutions, respectively; the fitted k values were 13.35 × 10-3, 10.79 × 10-3, 12.09 × 10-3 and 8.00 × 10-3 min-1, respectively. The piezocatalytic mechanism of γ-AlON particles in the selective degradation of MO was further analysed in free-radical scavenging activity experiments. Hydroxyl radicals (•OH), superoxide radicals (•O2-), holes (h+) and electrons (e-) were found to be the main active substances in the degradation process. Therefore, γ-AlON particles are an efficient and promising piezocatalytic material for the treatment of dye pollutants.

Application of catalytic technology based on the piezoelectric effect in wastewater purification

The demands of human life and industrial activities result in a significant influx of toxic contaminants into aquatic ecosystems. In particular, organic pollutants such as antibiotics and dye molecules, bacteria, and heavy metal ions are represented, posing a severe risk to the health and continued existence of living organisms. The method of removing pollutants from water bodies by utilizing the principle of the piezoelectric effect in combination with chemical catalytic processes is superior to other wastewater purification technologies because it can collect water energy, mechanical energy, etc. to achieve cleanliness and high removal efficiency. Herein, we briefly introduced the piezoelectric mechanisms and then reviewed the latest advances in the design and synthesis of piezoelectric materials, followed by a summary of applications based on the principle of piezoelectric effect to degrade pollutants in water for wastewater purification. Moreover, water purification technologies incorporating the piezoelectric effect, including piezoelectric effect-assisted membrane filtration, activation of persulfate, and battery electrocatalysis are elaborated. Finally, future challenges and research directions for the piezoelectric effect are proposed.

ZnO quantum dots decorated BaTiO3 for cancer sonodynamic therapy

Sonodynamic therapy depending on ultrasound irradiation, which generates reactive species to kill cancer cells, has attracted considerable attention due to the deep tissue penetration depth. However, the insufficient separation of electron/hole pairs induces its limited therapeutic efficiency. Herein, we use oxygen vacancy and ZnO quantum dots decoration techniques to enhance electron/hole separation and reactive species production. In oxygen vacancy-engineered BaTiO3, the higher oxygen vacancy concentration leads to more efficient adsorption of activate O2 and thus results in production of more radicals. In BaTiO3/ZnO heterostructures, the built-in electric field further improves separation of electron/hole pairs. The separated electron/hole react with O2/H2O to produce reactive species of •OH/∙O2- and kill cancer cells upon ultrasound irradiation. The work provides a guidance for sonosensitizers to tumor therapy.

Twin Boundaries-Induced Centrosymmetric Breaking of Hollow CaTiO3 Nanocuboids for Piezocatalytic Hydrogen Evolution

Piezocatalysis, a transformative mechanochemical energy conversion technique, has received considerable attention over the past decade for its role in processes such as hydrogen evolution from water. Despite notable progress in the field, challenges remain, particularly in the areas of limited piezocatalysis efficiency and limited availability of materials requiring a non-centrosymmetric structure. Here, a pioneering contribution is presented by elucidating the piezocatalytic properties of hollow CaTiO3 nanocuboids, a centrosymmetric material with a nominally nonpolar state. Remarkably, CaTiO3 nanocuboids exhibit an impressive hydrogen production rate of 3.44 mmol g-1 h-1 under ultrasonic vibrations, surpassing the performance of the well-established piezocatalyst BaTiO3 (2.23 mmol g-1 h-1). In contrast, commercial CaTiO3 nanoparticles do not exhibit piezocatalytic performance. The exceptional performance of hollow CaTiO3 nanocuboids is attributed to the abundance presence of twin boundaries on the {110} facet within its crystal structure, which can impart significant polarization strength to CaTiO3. Extending the investigation to other centrosymmetric materials, such as SrZrO3 and BaZrO3, the experimental results also demonstrate their commendable properties for piezocatalytic hydrogen production from water. This research underscores the significant potential of centrosymmetric materials in piezocatalysis.

Constructing Ce-OH groups on CeO2 for enhancing removal and recovery of uranium from wastewater and seawater

Efficient recovery of uranium from wastewater and seawater provides an important guarantee for the sustainable growth of nuclear energy. Herein, we skillfully use the alkali etching method to construct CeO2 hollow spheres rich in Ce-OH groups for the removal and recovery of uranium from water matrixes. It is found that the CeO2 exhibits fast adsorption kinetics (equilibrium time within 10 min) and moderate adsorption capacity (143.1 mg/g), and the removal efficiency of low concentration uranium (0.1 g/L and 1 g/L) reaches 100% within 1 min of adsorption. Moreover, the adsorption of uranium by CeO2 is almost unaffected by common anions and cations in the environment, even if the concentration of anions is 1000 times that of uranium. More importantly, the CeO2 can enrich uranium concentration in seawater by 167.9 times and the recovery rate reaches 83.9%. Mechanistic studies reveal that the adsorption of uranium by CeO2 is mainly attributed to the rich Ce-OH groups on the surface of CeO2, resulting in the rapid adsorption of U(VI) and mainly forms a single-bridge model. The findings of this study provide a green and efficient path for the removal and recovery of uranium from wastewater and seawater.

Boosted charge transfer in a naturally formed Ca(Al2Si2O8)/Fe2O3 heterojunction for piezocatalytical formation of H2O2 and solidification of U(VI)

Energy and environmental issues make the generation of H2O2 and the separation of U(VI) from water very important topics. In this work, we disclosed a low-cost, high-efficiency method for separating U(VI) from water based on the naturally formed catalyst (red volcanic stone powders, RVSP) of Ca(Al2Si2O8)/Fe2O3 heterojunction through a piezocatalytic pathway induced by ultrasonication. The charges were found to be elevatedly separated due to the formation of the heterojunction. It is found that under ultrasonication, charges were effectively separated and then reacted with water to form H2O2 with a high yield of 196.7 μmol·g-1 in 4 h, which further solidifies U(VI) to form a solid of UO2O2. The removal rate of U(VI) in water reached 96 % (50 ppm) within 150 min. Furthermore, the results calculated by VASP show that the cyclic variation of the conduction bands under a cyclic force field facilitates the charge separation, and thus may promote piezocatalysis. Most importantly, the application study in real seawater indicates that U(VI) piezocatalysis based on natural minerals has great potential. This work presents a comprehensive investigation of U(VI) piezocatalysis by Ca(Al2Si2O8)/Fe2O3 and provides a new idea for piezocatalytic extraction of uranium.

Advanced Photocatalytic Uranium Extraction Strategies: Progress, Challenges, and Prospects

Nuclear energy with low carbon emission and high-energy density is considered as one of the most promising future energy sources for human beings. However, the use of nuclear energy will inevitably lead to the discharge of nuclear waste and the consumption of uranium resources. Therefore, the development of simple, efficient, and economical uranium extraction methods is of great significance for the sustainable development of nuclear energy and the restoration of the ecological environment. Photocatalytic U(VI) extraction technology as a simple, highly efficient, and low-cost strategy, received increasing attention from researchers. In this review, the development background of photocatalytic U(VI) extraction and several photocatalytic U(VI) reduction mechanisms are briefly described and the identification methods of uranium species after photocatalytic reduction are addressed. Subsequently, the modification strategies of several catalysts used for U(VI) extraction are summarized and the advantages and disadvantages of photocatalytic U(VI) extraction are compared. Additionally, the research progress of photocatalytic technology for U(VI) extraction in actual uranium-containing wastewater and seawater are evaluated. Finally, the current challenges and the developments of photocatalytic U(VI) extraction technology in the future are prospected.