Piezoelectric Field Research Articles

Layered perovskite piezoelectric Bi3TiNbO9 as a piezo-photocatalyst: Synergistically enhanced catalytic activity and mechanism

Photocatalysis is considered as a green and efficient technology for dealing with water pollution problems, but there exists serious carrier recombination in photocatalysis. Introducing a piezoelectric electric field to reduce carrier recombination and accelerate carrier separation and migration is a recognized as an effective approach, while it remains testing for exploitation for high-performance catalysts with light and stress dual response as well as the coupling catalytic mechanism. In this work, we report a novel layered perovskite structure piezo-photocatalyst Bi3TiNbO9 and conducted an analysis of potential piezo-photocatalytic mechanisms. The piezoelectric force microscopy (PFM) and COMSOL finite element analysis prove that the Bi3TiNbO9 is a piezoelectric with strong piezoelectricity. In the degradation of tetracycline hydrochloride, Bi3TiNbO9 exhibits significantly better piezo-photocatalysis performance compared to piezocatalysis and photocatalysis. It is owing to that the ultrasound results in piezoelectric polarization accompanied by the generation of piezo-potential, which can induce piezocatalysis and facilitate the separation and transfer of photo-generated carriers. Electron paramagnetic resonance (EPR) technique and electrochemical tests are carried out under different excitation sources to identify the dominant active species involved in the reaction and to disclose the origin for the high performance of piezo-photocatalysis from the perspective of carriers. This study adds a new member to the family of piezo-photocatalytic material system, and provides further understanding on the synergistic piezo-photocatalysis mechanism.

Internal piezoelectric field produced by tri-component (FTO: Sb-ZnO/MoS2) thin film for enhanced photocatalytic degradation of organic pollutants and antibacterial activity

The detection of organic dyes, pharmaceuticals, and microorganisms in the water environment continues to be a major concern worldwide. Hence, we report a novel method whereby a tri-component (Sb-ZnO/MoS2) immobilized on Fluorine-doped Tin Oxide (FTO) substrate for piezo-photocatalytic degradation of organic contaminants and bacterial disinfection. To determine the optical, electrochemical, physical, and chemical properties of the Sb-ZnO/MoS2, the following methods were applied, SEM & EDS, TEM, XRD, BET, UV-Vis DRS, PL, EIS and chronoamperometry. The SEM and TEM results showed long ZnO nanorods on the surface of stacked MoS2 nanosheets. Chronoamperometry studies showed that the Sb-ZnO/MoS2 tri-component exhibited a piezoelectric effect under ultrasonic vibration, indicating an internal piezoelectric field for inhibition of electrons and holes from recombination. According to PL studies, Sb-ZnO/MoS2 tri-component had a lower PL emission peak intensity, which suggests a better separation of electrons and holes. The developed tri-component was investigated for its catalytic degradation of methylene blue (MB), methyl orange (MO), and ciprofloxacin (CIP) under light and ultrasonic vibration. The coupling of light (photocatalysis) and ultrasonic irradiation (piezocatalysis) showed greater degradation efficiencies of 95, 82, and 72% for MB, MO, and CIP, respectively. The degree of mineralisation was recorded from total organic carbon (TOC) as 76, 70, and 52% for MB, MO, and CIP, respectively. In addition, Sb-ZnO/MoS2 tri-component was shown to have antibacterial activity against both E. coli and S. aureus bacterial strains. Therefore, this study reveals that the prepared Sb-ZnO/MoS2 tri-component can be applied for the simultaneous removal of dyes, pharmaceuticals, and disinfection of wastewater pollutants.

A Self‐Powered Wound Dressing Based on “Lock‐ON/OFF” Drug Release Combined Electric Stimulus Therapy for Accelerated Infected Wound Healing

AbstractTo facilitate the on‐demand release of hydrophilic antibiotics for accelerated repair of infected wounds, a self‐powered wound dressing incorporating a “Lock‐ON/OFF” electric field (EF)‐driven drug release mechanism combined with electrical stimulation (ES) therapy is presented. When subjected to mechanical stress, the drug exhibits controlled, slow‐release behavior, achieving a remarkable cumulative release rate of 88.57%—89 times higher than the non‐mechanical stress group. Conversely, in the absence of mechanical stress, the drug remains unreleased, maintaining a 0% cumulative release rate in a fully closed state. The dressing utilizes its piezoelectric effect to establish an electric field, enabling precise control of hydrophilic drug release by regulating the electrostatic balance between the drug carrier and the drug. Moreover, the piezoelectric field acts as an exogenous electric field, remodeling the endogenous electric field of the wound, and accelerating wound closure. Combining EF‐driven drug release with ES result in a 1.26 fold improvement in wound healing compared to ES alone. This study addresses precision therapy limitations in fully automated diagnosis and treatment, paving the way for advancements in remote diagnosis, wireless therapy, and on‐demand precision medicine.

Anisotropic structural and optical properties of semi-polar (20–21) InGaN/GaN multiple quantum wells grown on patterned sapphire substrates

Semi-polar orientation owns the advantage of reduced internal piezoelectric fields by tilting the growth direction away from the conventional c-direction. The crystal symmetry and the balanced biaxial stress in growth plane are inevitably broken in the semi-polar orientation, leading to the appearance of anisotropic properties in both structural and optical performance. This report has investigated the structural and optical properties of semi-polar (20–21) InGaN/GaN multiple quantum wells overgrown on patterned sapphire substrates with a wide wavelength range from 415 nm to 521 nm. Polarization switching was not observed on these semi-polar (20–21) samples. The polarization ratio monotonically increases from 0.18 to 0.43 with increasing the emission wavelength, and the energy difference simultaneously increases from 17 meV to 29 meV. As increasing the excitation laser power, the polarization ratio drops slightly while the energy difference remains stable, indicating a saturation of the recombination to the topmost valence subband. These results help exploit the anisotropic structural and optical properties of semi-polar nitrides and promote the development of highly polarized light source for the application in the fields of display and communication.

Piezoelectric polarization field tuning Schottky barrier of Ni/Mn0.2Cd0.8S composite for hot electrons transfer to enhance photocatalytic hydrogen evolution

Coupling piezoelectric effect with local surface plasmon resonance (LSPR) for visible-light-driven photocatalytic hydrogen evolution is of great significance to realize the high-efficiency solar energy conversion. In this work, Ni/Mn0.2Cd0.8S plasmon piezo-photocatalysts were constructed by combining plasma metal Ni with structural distortion-enhanced Mn0.2Cd0.8S for piezo-photocatalytic hydrogen evolution. The influence of integrating plasma Ni with piezoelectric Mn0.2Cd0.8S on the photocatalytic performance was investigated together with the wavelength dependent experiments. Under simultaneous illumination and ultrasound, the optimized 1.5 wt%-Ni/Mn0.2Cd0.8S displayed ultrahigh piezo-photocatalytic hydrogen evolution rate of 72.38 mmol g−1 h−1, which was approximately 11.8 and 25.0-fold that of Mn0.2Cd0.8S and CdS, respectively. The significantly enhanced performance was assigned to the coupling of piezoelectric and LSPR effect, through which the internal piezoelectric polarization field generated by Mn0.2Cd0.8S could change the local contact characteristics of Mn0.2Cd0.8S and Ni interface, decreasing the degree of upward bending of the band and reducing the Schottky barrier height, thus promoting the interfacial transfer of plasmon hot electrons for photocatalytic hydrogen evolution. This work provides a reliable reference for developing high-performance plasmonic piezo-photocatalysts materials based on piezoelectric and LSPR effect.

Piezoelectric fields and martensitic transition in spontaneously ordered GaInP2/GaAs epi-layers

Piezoelectric fields and martensitic transition in spontaneously ordered GaInP2/GaAs epi-layers

Enhanced hydrogen evolution activity by novel RuSe2/CdS piezo-photocatalysts with piezoelectric field

Photocatalytic hydrogen production is identified as a prospective route for solving the energy crisis and reducing environmental pollution. However, the complexation of photogenic carriers and the lack of active sites hinder the efficiency of photocatalysis. The piezoelectric effect and the corporation of cocatalyst are considered as effective strategies to facilitate the separation of the photogenic charge carriers. Ru-based compounds such as RuSe2, RuTe2, RuS2 and their derivatives are considered as potentially alternative catalysts to the platinum cocatalyst for the hydrogen evolution realution. Herein, we prepare a novel RuSe2/CdS piezo-photocatalysts in which RuSe2 cocatalyst is synthesized by microwave method to enable efficient piezo-photocatalytic hydrogen production. The experimental results show that the hydrogen production efficiency of 1.5% RuSe2/CdS is 63.857 μmol/mg/h under solar and ultrasonic conditions, which is about 7.54 times that of pure CdS (8.468 μmol/mg/h). More importantly, the hydrogen production efficiency of 1.5% RuSe2/CdS is remain stable after seven cycles of experiments. The enhanced piezo-photocatalytic activity is attributed to the interaction and the matching energy bands between RuSe2 and CdS, which facilitates photogenic electrons extend from CdS to RuSe2 cocatalyst. This work exposes a prospect for improving photocatalytic performance, and achieving efficient piezo-photocatalysis by using mechanical energy.

Development of ternary Pt/BaTiO3/Bi2O3 heterostructured piezo-photocatalysts for antibiotic degradation

The efficient separation of surface and bulk photocarriers is very crucial for improving the photocatalytic activity of semiconductors. To achieve this goal, herein we have developed ternary Pt/BaTiO3/Bi2O3 (Pt/BTO/BO) heterostructured piezo-photocatalysts with high capacity for antibiotic degradation. The ternary heterostructures were constructed by anchoring BTO and Pt nanoparticles on the surface of BO microrods. Their piezo-photocatalytic performance and mechanism was elucidated through the degradation of ciprofloxacin (CIP). It is revealed that the ternary heterostructures exhibit obviously enhanced photocatalysis under illumination of simulated sunlight; typically the photocatalytic activity of the 2 %Pt/9%BTO/BO sample is improved by 8.2 and 2.4 times over that of single BTO and BO, respectively. This phenomenon originates from the improved separation of photocarriers by the BTO/BO and Pt/BO interface fields. More interestingly, when simulated-sunlight illumination was accompanied with ultrasonic vibration, the piezo-photocatalysis of 2 %Pt/9%BTO/BO shows a further improvement in the CIP degradation. The coupled piezo-photocatalysis shows a synergistic enhancement factor SF = 2.64. Efficient separation of bulk photocarriers, which is caused by ultrasonic-induced piezoelectric polarization field, is the main reason for the elevated piezo-photocatalysis. Additionally, the decomposition process of CIP and potential toxicity of substances generated during the CIP degradation process were elucidated.

Non-noble plasmonic TiN modified BiOBr for the piezo-photocatalytic removal of sulfisoxazole: Simultaneous improvement of photocatalytic and piezoelectric properties

Piezo-photocatalytic systems have the capacity to degrade environmental contaminants by exploiting mechanical and photonic energy. Herein, we report on a strategy for the modification of bismuth bromide oxide (BiOBr) with a non-noble metal plasma (titanium nitride (TiN)). The synthesized piezo-photocatalytic system demonstrated excellent performance for the degradation of sulfisoxazole (SIZ), where the 2-TiN/BiOBr samples exhibited a high degradation rate of 94.9 % in 70 min, with a rate constant that was 4.68 times higher than that of BiOBr. This improved catalytic performance was attributed to the localized surface plasmon resonance (LSPR) effect and high electronic conductivity of TiN, which improved the photocatalytic and piezoelectric properties of BiOBr. The hypothesis of an extended piezoelectric field was verified in conjunction with density functional theory (DFT) calculations. This work presents a new perspective for improved piezoelectric photocatalytic systems, which have great potential for utilizing solar and mechanical energy for environmental remediation.

Enhanced environmental purification with novel Pd/ZnO nanorod–decorated building materials through piezo‐photocatalytic synergistic effect

AbstractIntegrating photocatalytic technology with building materials is an imperative new trend in the green building field. Here, a novel Pd/ZnO nanorod array‐decorated ceramic tile has been designed for the first time, aiming to purify the surrounding environment. Because of the piezoelectric characteristics of ZnO nanorods, the environmental degradation efficiency of this tile‐based structure under light irradiation could be improved through injecting mechanical vibration stress. The unique piezo‐photocatalytic synergistic effect, due to the piezoelectric field created by bent ZnO nanorods and the Schottky junction formed by the noble metal Pd/ZnO heterostructures, could effectively separate the photoinduced carriers and reduce the rate of recombination, boosting the degradation efficiency. The tile‐based Pd/ZnO reaches the greatest catalytic efficiency of 75% for dye degradation in 30 min when ultrasonic and solar irradiation are applied simultaneously. Present results offer a fresh idea for creating novel piezo‐photocatalytic materials applied in eco‐friendly green buildings.

Enhanced photocatalytic performance of NH2-MIL-125(Ti)/SrTiO3 heterostructures by the piezoelectric effect of SrTiO3

Applying piezoelectric effect on modulating charge transport behavior was considered as one efficient strategy to make feasible charge separation in photocatalysts towards boosting hydrogen evolution performance. Here, with employing corona-poling treatment, SrTiO3 is converted to be a piezoelectric component in the constructed type II NH2-MIL-125(Ti)/SrTiO3 heterojunction. Since the piezoelectric field could tilt the band bending to a degree to be convenient for the charge transfer from SrTiO3 to NH2-MIL-125(Ti), it is also favorable to offer additional active sites on SrTiO3 to form dual reduction sites for the following piezo-photocatalytic reaction. Both the ameliorated surficial polarization and charge transfer trajectory in NH2-MIL-125(Ti)/SrTiO3 type II heterojunction are devoted to the boosted hydrogen production rate for NH2-MIL-125(Ti)/SrTiO3-0.1 (NM/STO-0.1), that is up to 1562.3 μmol h−1 g−1, 1.79 times higher than that of unpolarized NM/STO-0.1 (871.6 μmol h−1 g−1) and 2.35 times higher than that of NH2-MIL-125(Ti) (663.8 μmol h−1 g−1), respectively. This research reported initially the assistant of SrTiO3 with piezoelectric feature for enhanced performance photocatalytic hydrogen evolution, which could be one prominent strategy to achieve the reasonable design of efficient photocatalytic system.

Anomalous reverse mechanical polarization switching in negative piezoelectric CuInP2S6.

van der Waals ferroelectric CuInP2S6 (CIPS) has drawn significant attention not only because of its unique properties but also owing to its technological potential for nanoelectronics. Mechanical polarization switching provides a new approach to modulating polarization states through flexoelectricity. This approach is particularly favourable for CIPS to avoid surface damage under an electric field due to the coupling between polarization switching and ionic motion. Here, we report anomalous downward-to-upward polarization switching under tip force in CIPS nanoflakes, which is believed to stem from the competition between piezoelectric and flexoelectric fields induced by tip pressure, together with the unique quadruple-well state present in CIPS. This work provides novel insights into the polarization switching mechanism of CIPS, elucidating the interplay between competing piezoelectric and flexoelectric fields, and it may pave the way for the design of electromechanical devices based on flexoelectric engineering.

Strain modulation effect of superlattice interlayer on InGaN/GaN multiple quantum well

The strong piezoelectric field in InGaN/GaN heterostructure quantum wells severely reduces the light emission efficiency of multiple quantum well (MQW) structures. To address this issue, a strain modulation interlayer is commonly used to mitigate the piezoelectric polarization field and improve the luminescence performance of the devices. To investigate the influence and mechanism of strain modulation in the InGaN/GaN superlattice (SL), epitaxial wafers with an n-type InGaN/GaN SL interlayer sample, and their corresponding control samples are prepared. The measured temperature-dependent photoluminescence (PL) spectra of the epitaxial wafers, show that the introduction of an SL interlayer leads to a shorter-wavelength emission and enhancement of internal quantum efficiency. As the temperature increases, a blue shift of the PL peak is observed. However, for the sample with an SL interlayer, the blue shift of the PL peak with temperature increasing is relatively small. Electroluminescence (EL) experiments indicate that the introduction of an SL interlayer significantly increases the integrated intensity of the EL peak and reduces its full width at half maximum. These phenomena collectively indicate that the incorporation of a superlattice interlayer can partly suppress the quantum-confined Stark effect (QCSE) that affects the light emission efficiency. Theoretical calculations show that the introduction of a superlattice strain layer before growing an active multiple quantum well can weaken the polarization-induced built-in electric field in the active quantum well, reduce the tilt of the energy band in the multiple quantum well active region, increase the overlap of electron and hole wave functions, enhance the emission probability, shorten the radiative recombination lifetime, and promote competition between radiative recombination and non-radiative recombination, thereby achieving higher recombination efficiency and improving light emission intensity. This study provides experimental and theoretical evidence that the strain modulation SL interlayer can effectively improve the device performance and offer guidance for optimizing the structural design of devices.

Piezoelectric properties of (Sr0.2Ca0.8)3TaGa3Si2O14 and Ca3TaGa3Si2O14 single crystals grown via vertical Bridgman method

(Sr0.2Ca0.8)3TaGa3Si2O14 and Ca3TaGa3Si2O14 single crystals were successfully grown using the vertical Bridgman method, and the piezoelectric properties of these crystals were studied.

Piezoelectric PZT film-driven resonant torsional MEMS electric field sensor

Piezoelectric PZT film-driven resonant torsional MEMS electric field sensor

High photopiezocatalytic energy conversion via effective charge separation and deformability in the asymmetric ternary heterojunction Bi4Ti3O12/PPy/TiO2

Boosted electric field via enhanced dipoles, increased charge transmission towards the catalyst surface and promoted electron energy via piezoelectric field resulted in the highly efficient photopiezocatalytic activity of ternary structures.

Piezoelectric field and defect engineering synergistically improved photocatalytic performance of K0.5Na0.5BixNb1-xO3 for degradation of organic pollutants

Semiconductor photocatalysts have been widely researched in wastewater treatment and photocatalysis predominantly depends on the redox reaction of photoinduced charge carriers on semiconductor surface. Afterwards, photoinduced carrier concentration and the effective separation of electrons and holes have been proved to be pivotal in promoting photocatalytic efficiency. Further, the internal electric field established by polarization of piezoelectric materials is considered an efficient means of separating electrons and holes. Hence, as a typical representative of piezoelectric materials, (K0.5Na0.5)Nb1-xBixO3 was designed and prepared by introducing Bi2O3 in (K0.5Na0.5)NbO3 to construct defects intentionally, and thus reduce the band gap and increase carrier concentration by the hybrid energy levels, for another promote efficient separation of electrons and holes by virtue of the built-in field created by piezoelectric polarization and pinning holes by defects. Thereinto, the K of Rh B degradation by (K0.5Na0.5)Nb0.98Bi0.02O3 reached 0.07846 min−1 under the combined light irradiation and ultrasonic, meanwhile 95 % Rh B can be degraded within 20 min and nearly 100 % in 60 min with eminent cycling stability, which is brilliant than previous reports on KNN-based catalyst. This work provides not only a novel piezo-photocatalytic degradation material but also a built-in electric field and defect synergy strategy for boosting carrier separation.

Ultrasound‐Activated Piezocatalyst Triggers Sulfate Radical Production for Augmented Oxidative Tumor Suppression

Sonopiezoelectric therapy (SPT) has gained ever‐increasing prominence in tumor therapy as a combination of ultrasound (US) and piezoelectric nanomaterials to generate cytotoxic reactive oxygen species (ROS) for tumor suppression. In this study, the facile hydrothermal method is used to construct the distinct 2D piezocatalyst Bi2Fe4O9 nanosheets (BFO NSs). The engineered BFO NSs can create a piezoelectric field when exposed to US irradiation, facilitating the separation of electron–hole (e−–h+) pairs to play a crucial role in Fe3+/Fe2+ circulation, which catalyzes the activation of peroxymonosulfate (PMS), resulting in an amplified production of cytotoxic sulfate radical (SO4•−). The produced SO4•− combines with ROS generated by SPT including hydroxyl radicals (•OH), and singlet oxygen (1O2), leading to the augmented oxidative tumor suppression. The BFO NSs and PMS are further integrated into a thermal hydrogel (BFO/PMS‐Gel) for in vitro and in vivo investigations on their catalytic antitumor effects. In both in vitro and in vivo studies, it is validated that BFO/PMS‐Gel, under US irradiation, significantly enhances radicals generation efficiency, which achieves superior antitumor performance while maintaining high therapeutic biocompatibility and biosafety, providing a representative paradigm of US‐activated multiple radicals production as enabled by piezoelectric nanomedicine for antitumor treatment.

Nitrogen-doped carbon nanotubes for self-powered memristive systems

Memristive devices are one of the promising candidates for creating neuromorphic systems due to the possibility of multilevel switching, low operating voltages and high scalability. However, as with any passive element, the memristor requires an external bias voltage to operate, which requires the inclusion of a power source in the circuit. In this regard, of great interest are works on the creation of self-powered memristive systems consisting of connecting in series a memristor and a nanogenerator that converts the energy of the external environment into electrical energy [1, 2]. Such a memristive system has a high potential for applications in aerospace and implantable electronics. At the moment, the first self-powered memristive and sensor systems based on metal oxides and piezoelectric nanogenerators (PENG) have already been developed [2]. The main problems in this area are to reduce the size of the nanogenerator and to match the output parameters of the nanogenerator and the input parameters of the memristor. In the framework of this work, these problems are being resolved by creating a self-powered memristive system based on nitrogen-doped carbon nanotubes (N-CNTs). Previously, we studied the memristive properties of N-CNTs and showed that nanotubes demonstrate reproducible multilevel switching with a resistance ratio in the high- and low-resistance states (HRS/LRS) of about 4⋅105 [3, 4]. It was found that the memristive effect in N-CNTs is due to the incorporation of nitrogen atoms into the nanotube structure and the formation of an internal piezoelectric field [4]. As part of further studies, it was found that an array of vertically aligned N-CNTs is a promising material for creating PENG: the generated output voltage is hundreds of mV and the current generated by single nanotube reaches hundreds of nA [5]. The results obtained allow us to speak about the possibility of developing a self-powered memristive system by connecting in series a memristor and PENG based on N-CNTs. To optimize the output characteristics of the PENG, in particular, the amplitude of the generated voltage, and the input switching voltage of the N-CNT-based memristor, studies were carried out to increase the piezoelectric response and reduce the switching voltage of the N-CNT resistance by changing the concentration of the dopant nitrogen in the nanotube growth process. It was found that it is necessary to grow N-CNTs with a doping nitrogen concentration of up to 12% and a high aspect ratio of length to diameter (more than 60) to create PENG with an output voltage of up to 2 V. These N-CNT parameters are provided at a low growth temperature (500–550 C°) and high ratio of acetylene and ammonia flows (1:5 - 1:6). On the contrary, the N-CNTs with a small aspect ratio (less than 30) and doping nitrogen concentrations of 4–6% are required for the manufacture of memristors with a minimum switching voltage (about 2 V), These N-CNT parameters are provided by increasing the growth temperature to 615 C° and reduction in growth time. The obtained results can be used in the development of self-powered memristive and sensor systems based on nitrogen-doped carbon nanotubes.

Efficient piezo-photocatalysis of Bi2O2(OH)NO3/BiOI heterojunction: Collaboration of piezoelectric polarization and interface electric field

Effective removal of recalcitrant pollutants is crucial for environmental protection. Tetracycline hydrochloride, as a representative recalcitrant organic pollutant, poses a potential threat to environmental integrity when present in aquatic ecosystems. Coupling piezoelectric polarization, capable of considerably promoting the photocharge separation, acts as a very prevalent and attractive strategy to improve the photocatalytic activity. In this study, an efficient piezo-photocatalytic system was developed in Bi2O2(OH)NO3/BiOI heterojunction by collaborating with interfacial electric field and vibration-induced piezoelectric polarization. The construction of type II heterojunction allows an interfacial electric field to propel the photogenerated electrons from BiOI to Bi2O2(OH)(NO3) under visible light irradiation. The introduction of vibration-induced piezoelectric polarization field strengthens the interfacial electric field, which further promote the separation and migration of photogenerated charges. Profiting from the above advantages, Bi2O2(OH)(NO3)/BiOI heterojunction exhibited a remarkable piezo-photocatalytic performance, achieving an over 80% degradation efficiency of tetracycline hydrochloride within 10 min, which far surpasses that under individual photocatalysis or ultrasound-induced piezocatalysis and also exceeds most of the previously reported piezo-photocatalysts. The combination of electron paramagnetic resonance, piezoresponse force microscopy, COMSOL simulation, and photoelectrochemical tests are conducted to probe the synergistically-catalytic mechanism. This work not only elucidates the comprehensive impact of interfacial electric field and piezoelectric polarization on charge separation, but also highlights the tremendous potential of piezo-photocatalysis for environmental remediation.