Synergistic Enhancement of Piezocatalytic Activity of BaTiO3 Convex Polyhedrons Nanocomposited with Ag NPs/Co3O4 QDs Cocatalysts

Biomaterials based on advanced oxidation processes in tooth whitening: fundamentals, progress, and models

The increasing desire for aesthetically pleasing teeth has resulted in the widespread use of tooth whitening treatments. Clinical tooth whitening products currently rely on hydrogen peroxide formulations to degrade dental pigments through oxidative processes. However, they usually cause side effects such as tooth sensitivity and gingival irritation due to the use of high concentrations of hydrogen peroxide or long-time contact. In recent years, various novel materials and reaction patterns have been developed to tackle the issues related to H2O2-based tooth whitening. These can be broadly classified as advanced oxidation processes (AOPs). AOPs generate free radicals that have potent oxidizing properties, which can thereby increase the oxidation power and/or reduce the exposure time and can probably minimize the side effects of tooth bleaching. While there have been several reviews on clinical tooth whitening and the application of novel nanomaterials, a review based on the concept of AOPs in tooth bleaching application has not yet been conducted. This review describes the common types and mechanisms of AOPs, summarizes the latest research progress of new tooth bleaching materials based on AOPs, and proposes a model for tooth bleaching and a rate control step at the molecular level. The paper also reviews the shortcomings and suggests future development directions.

Highly efficient piezocatalytic composite with chitosan biopolymeric membranes and bismuth ferrite nanoparticles for dye decomposition and pathogenic S. aureus bacteria killing

Untreated wastewater harbors dangerous pathogens, chemicals, and pollutants, posing grave public health threats. Nowadays, there is a rising demand for eco-friendly technologies for wastewater treatment. Recently, piezoelectric materials-based wastewater treatment technology has captured considerable interest among researchers because of its noninvasiveness and rapidity. Herein, a highly efficient piezoelectric composite material is designed with chitosan-incorporated bismuth ferrite (BFO) nanocrystals, to decompose pollutants and ablate bacteria in wastewater. On one hand, piezoelectric BFO has shown exclusive piezo-coefficient for ultrasound-mediated reactive oxygen species (ROS) production. On the other hand, chitosan depicts its biocompatible nature, which not only promotes cellular adhesion but also significantly elevates the ROS production capabilities of BFO under ultrasound. The synergistic effect of these two piezoelectric units in one composite entity shows an improved ROS production, eradicating ∼87.8% of Rhodamine B within 80 min under soft ultrasound treatment (rate constant, k ≈ 0.02866 min-1). After performing the scavenger experiment, it has been found that hydroxyl radicals are the dominating factor in this case. Further, the reusability of the composite piezocatalyst is confirmed through multiple cycles (five times) of the same experiment. The high polarizability of the composite material facilitates the generation of piezoelectric power through finger tapping (∼12.05 V), producing substantial instantaneous piezo-voltage. Moreover, the sample exhibits remarkable antibacterial activity, with nearly 99% bacterial eradication within 30 min. This indicates a significant advancement in utilizing biopolymeric composites incorporated with BFO for fabricating versatile devices with multidimensional applications.

Heterostructured piezocatalytic nanoparticles with enhanced ultrasound response for efficient repair of infectious bone defects

Infection of bone defects remains a challenging issue in clinical practice, resulting in various complications. The current clinical treatments include antibiotic therapy and surgical debridement, which can cause drug-resistance and potential postoperative complications. Therefore, there is an urgent need for an efficient treatment to sterilize and promote bone repair in situ. In this work, an ultrasound responsive selenium modified barium titanate nanoparticle (Se@BTO NP) was fabricated, which exhibited significant antibacterial and bone regeneration effects. Selenium nanoparticle (Se NP) was modified on the surface of barium titanate nanoparticle (BTO NP) to form heterostructure, which facilitated the second distribution of piezo-induced carriers under ultrasound (US) irradiation and improved the separation of electron-hole pairs. The Se@BTO NPs exhibited remarkable antibacterial efficiency with an antibacterial rate of 99.23 % against Staphylococcus aureus (S.aureus) and significantly promoted the osteogenic differentiation under ultrasound irradiation. The in vivo experiments exhibited that Se@BTO NPs successfully repaired the femoral condylar bone defects of rats infected by S.aureus, resulting in significant promotion of bone regeneration. Overall, this work provided an innovative strategy for the utilization of US responsive nanomaterials in efficient bacteria elimination and bone regeneration. STATEMENT OF SIGNIFICANCE: Infectious bone defects remain a challenging issue in clinical practice. Current antibiotic therapy and surgical debridement has numerous limitations such as drug-resistance and potential complications. Herein, we designed an innovative ultrasound responsive selenium modified barium titanate nanoparticle (Se@BTO NP) to achieve efficient non-invasive bacteria elimination and bone regeneration. In this work, Se@BTO nanoparticles can enhance the separation of electrons and holes, facilitate the transfer of free carriers due to the cooperative effect of ultrasound induced piezoelectric field and heterojunction construction, and thus exhibit remarkable antibacterial and osteogenesis effect. Overall, our study provided a promising strategy for the utilization of piezocatalytic nanomaterials in efficient antibacterial and bone regeneration.

Enhanced piezocatalytic hydrogen evolution performance of bismuth vanadate by the synergistic effect of facet engineering and cocatalyst engineering

Developing piezocatalysts with excellent piezocatalytic hydrogen evolution reaction (HER) performance is highly desired but also challenging. Here, facet engineering and cocatalyst engineering are employed to synergistically improve the piezocatalytic HER efficiency of BiVO₄ (BVO). Monoclinic BVO catalysts with distinct exposed facets are synthesized by adjusting pH of hydrothermal reaction. The BVO with highly exposed {110} facet exhibits a superior piezocatalytic HER performance (617.9 μmol g^-1h^-1) compared with that with {010} facet, owing to the strong piezoelectric property, high charge transfer efficiency, and excellent hydrogen adsorption/desorption capacity. The HER efficiency is enhanced by 44.7% by selectively depositing cocatalyst of Ag nanoparticles specifically on the reductive {010} facet of BVO, where the Ag-BVO interface provides the directional electron transport for high-efficiency charge separation. Under the collaboration between cocatalyst of CoO_x on {110} facet and the hole sacrificial agent of methanol, the piezocatalytic HER efficiency is evidently enhanced by 2 times because CoO_x and methanol can impede the water oxidation and improve the charge separation. This easy and simple strategy provides an alternative perspective on designing high-performance piezocatalysts.

Piezoelectric Metal-Organic Frameworks Based Sonosensitizer for Enhanced Nanozyme Catalytic and Sonodynamic Therapies

The regulation of electrostatic electric fields through electrical stimulation is an efficient method to increase the catalytic activity of nanozymes and improve the therapeutic effect of nanozyme catalytic therapy. Piezoelectric materials, which are capable of generating a built-in electric field under ultrasound (US), not only improve the activity of nanozymes but also enable piezoelectric sonodynamic therapy (SDT). In this study, a sonosensitizer based on a Hf-based metal-organic framework (UIO-66) and Au nanoparticles (NPs) was produced. Under US irradiation, UIO-66 can generate a built-in electric field inside the materials, which promotes electron-hole separation and produces reactive oxygen species (ROS). The introduction of Au NPs facilitated the electron transfer, which inhibited the recombination of the electron-hole pairs and improved the piezoelectric properties of UIO-66. The value of the piezoelectric constant (d₃₃) increased from 71 to 122 pmV^-1 after the deposition of Au NPs. In addition, the intrinsic catalase and peroxidase activities of the Au NPs were increased 2-fold after the stimulation from the built-in electric field induced through US exposure. In vivo and in vitro experiments revealed that the proposed sonosensitizer can kill cancer cells and inhibit tumor growth in mice through the enhanced piezoelectric SDT and nanozyme catalytic therapy. The piezoelectric sensitizer proposed in this work proved to be an efficient candidate that can be used for multiple therapeutic modalities in tumor therapy.

Spatially Separated Redox Cocatalysts on Ferroelectric Nanoplates for Improved Piezophotocatalytic CO2 Reduction and H2O Oxidation

Utilizing solar and mechanical vibration energy for catalytic CO₂ reduction and H₂O oxidation is emerging as a promising way to simultaneously generate renewable energy and mitigate climate change, making it possible to integrate two energy resources into a reaction system for artificial piezophotosynthesis. However, the practical applications are hindered by undesirable charge recombination and sluggish surface reaction in the photocatalytic and piezocatalytic processes. This study proposes a dual cocatalyst strategy to overcome these obstacles and improve the piezophotocatalytic performance of ferroelectrics in overall redox reactions. With the photodeposition of AuCu reduction and MnO_x oxidation cocatalysts on oppositely poled facets of PbTiO₃ nanoplates, band bending occurs along with the formation of built-in electric fields on the semiconductor-cocatalyst interfaces, which, together with an intrinsic ferroelectric field, piezoelectric polarization field, and band tilting in the bulk of PbTiO₃, provide strong driving forces for the directional drift of piezo- and photogenerated electrons and holes toward AuCu and MnO_x, respectively. Besides, AuCu and MnO_x enrich the active sites for surface reactions, significantly reducing the rate-determining barrier for CO₂-to-CO and H₂O-to-O₂ transformation, respectively. Benefiting from these features, AuCu/PbTiO₃/MnO_x delivers remarkably improved charge separation efficiencies and significantly enhanced piezophotocatalytic activities in CO and O₂ generation. This strategy opens a door for the better coupling of photocatalysis and piezocatalysis to promote the conversion of CO₂ with H₂O.

Enhanced piezo-photocatalysis in Bi0.5Na0.5TiO3@Ag composite to efficiently degrade multiple organic pollutants

The synergistic piezo-photocatalysis with enhanced efficiency for degrading obstinate pollutants in wastewater is considered as an advanced way to ameliorate the global water contamination. In this work, we report a facile route to construct the Bi_0.5Na_0.5TiO₃@Ag composite by photoreduction of AgNO₃ to obtain Ag on Bi_0.5Na_0.5TiO₃ nanoparticles. And the composite was used to degrade three representative pollutants, i.e. ciprofloxacin, methyl orange and mitoxantrone hydrochloride. Remarkably, for methyl orange solution with the initial concentration of 10 mg/L, the degradation rate constant of the composite reached 0.051 min^-1. H⁺ and •O₂^- play a major role in this degradation process, verified by the radical quenching experiments. The absorption platform of Bi_0.5Na_0.5TiO₃ was located in the UV region, after introducing Ag in the composite, the absorption region broadened to both UV and visible light, greatly promoting the response to light. Simultaneously, the induced piezo-potential by mechanical energy in Bi_0.5Na_0.5TiO₃ hindered the carrier recombination, resulting in high-efficiency synergistic piezo-photocatalytic process. This work provides a paradigm to innovate both material and catalytic way for degrading multiple organic pollutants.

A Novel Strategy for Excellent Piezocatalytic Activity in Lead-Free BaTiO3-Based Materials via Manipulating the Multiphase Coexistence

Piezocatalysis is regarded as a fascinating technology for water remediation and possible disease treatment. A high piezoelectric coefficient (d₃₃) is one of the most important parameters to determine piezocatalytic performance, which can be manipulated via phase boundary design. Herein, a novel strategy for excellent piezocatalytic activity in lead-free BaTiO₃-based materials via manipulating the multiphase coexistence is proposed. The piezocatalyst of 0.82Ba(Ti_0.89Sn_0.11)O₃-0.18(Ba_0.7Ca_0.3)TiO₃ (0.82BTS-0.18BCT) with multiphase coexistence is prepared, and a large d₃₃ can be obtained. As a result, 0.82BTS-0.18BCT exhibits excellent piezocatalytic performance for the degradation of Rhodamine B (RhB). Furthermore, the removal rate of RhB could reach more than 90% after vibration for 30 min, and the reaction rate constant (k) could reach 0.0706 min^-1, which is much superior to that of most other representative perovskite-structured piezoelectric materials. Excellent piezocatalytic performance can be attributed to the strong local ferro-/piezoelectric response induced by the multiphase coexistence, as confirmed by the in situ piezoresponse force microscopy (PFM). Finally, the piezocatalytic degradation mechanism is analyzed systemically and proposed. This work not only provides a high-efficiency piezocatalyst but also sheds light on developing efficient BT-based piezocatalysts by manipulating the multiphase coexistence.