Monitoring and modulating the trajectory of eosinophilic esophagitis.

Current treatments of eosinophilic esophagitis (EoE) aim to eliminate esophageal mucosal inflammation and attenuate, stabilize, or reverse stricture formation. However, our ability to study the long-term course of esophageal strictures in patients with EoE is hampered by the short-term existence of this disease. It is unclear to what degree of control of inflammation is needed to prevent stricture formation. Additionally, identified phenotypes of EoE may ultimately dictate different levels of concern and time intervals for developing fibrosis. Currently, multiple methods are used to monitor patients' disease progression to fibrosis, as symptoms alone do not correlate with disease activity. Endoscopic findings and mucosal histology are used to monitor disease activity, but these focus on improvements in inflammation with inconsistent evaluation of underlying fibrosis. The use of functional lumen impedance planimetry, barium esophagraphy, and endoscopic ultrasound continues to expand in EoE. The rapid advancements in EoE have led to an armamentarium of measuring tools and therapies that holistically characterize disease severity and response to therapy. Nevertheless, our ability to evaluate gross esophageal fibrosis and stricture formation from a transmural rather than mucosal view should be a focus of future investigations because it is essential to monitoring and modulating the trajectory of EoE.

Nanoimprinting Solution-Derived Barium Titanate for Electro-Optic Metasurfaces.

Electro-optic metasurfaces have demonstrated significant potential in enhancing the modulation speed and efficiency for fast and large-scale free-space optical devices. Barium titanate has a strong electro-optic Pockels coefficient, but its availability in thin-film form is restricted due to costly growth processes or low thickness. Here, we fabricated active metasurfaces using an etch-free bottom-up process with sol-gel-based polycrystalline barium titanate with a large electro-optic coefficient similar to bulk lithium niobate. We achieve strong hybrid Mie/surface lattice resonances with a quality-factor of 200 at 633 nm wavelength, enhancing the light-matter interaction and therefore the Pockels effect. The metasurface transmission is electro-optically modulated with up to 5 MHz driving frequency at low voltages of less than 1 V thanks to resonant enhancement of the modulation amplitude by 2 orders of magnitude. This successful demonstration of electro-optic modulation in nanoimprinted barium titanate structures paves the way for low-cost and large-scale free-space modulators or tunable metalenses.

Tuning Exciton Emission via Ferroelectric Polarization at a Heterogeneous Interface between a Monolayer Transition Metal Dichalcogenide and a Perovskite Oxide Membrane.

We demonstrate the integration of a thin BaTiO3 (BTO) membrane with monolayer MoSe2 in a dual-gate device that enables in situ manipulation of the BTO ferroelectric polarization with a voltage pulse. While two-dimensional (2D) transition metal dichalcogenides (TMDs) offer remarkable adaptability, their hybrid integration with other families of functional materials beyond the realm of 2D materials has been challenging. Released functional oxide membranes offer a solution for 2D/3D integration via stacking. 2D TMD excitons can serve as a local probe of the ferroelectric polarization in BTO at a heterogeneous interface. Using photoluminescence (PL) of MoSe2 excitons to optically read out the doping level, we find that the relative population of charge carriers in MoSe2 depends sensitively on the ferroelectric polarization. This finding points to a promising avenue for future-generation versatile sensing devices with high sensitivity, fast readout, and diverse applicability for advanced signal processing.

Wireless Alerts and Data Monitoring from BNNO-MWCNTs/PDMS Composite Film-Based TENG Integrated Inhaler for Smart Healthcare Application.

In recent years, the implementation of energy-harvesting technology in medical equipment has attracted significant interest owing to its potential for self-powered and smart healthcare systems. Herein, the integration of a triboelectric nanogenerator (TENG) is proposed into an inhaler for energy-harvesting and smart inhalation monitoring. For this initially, barium sodium niobium oxide (Ba2NaNb5O15) microparticles (BNNO MPs) are synthesized via a facile solid-state synthesis process. The BNNO MPs with ferroelectricity and high dielectric constant are incorporated into polydimethylsiloxane (PDMS) polymer to make BNNO/PDMS composite films (CFs) for TENG fabrication. The fabricated TENG is operated in a contact-separation mode, and its electrical output performance is compared to establish the optimal BNNO MPs concentration. Furthermore, multi-wall carbon nanotubes (MWCNTs), a conductive filler material, are used to enhance the electrical conductivity of the CFs, thereby improving the electrical output performance of the TENG. The robustness/durability of the proposed BNNO-MWCNTs/PDMS CF-based TENG are investigated. The proposed TENG device is demonstrated to harvest electrical energy from mechanical motions via regular human activities and power portable electronics. The TENG is integrated into the inhaler casing to count the number of sprays remaining in the canister, send the notification to a smartphone via Bluetooth, and harvest energy.

Ultrasound stimulated piezoelectric barium titanate and boron nitride nanotubes in nonconductive poly-ε-caprolactone nanofibrous scaffold for bone tissue engineering.

Nanomaterials can provide unique solutions for the problems experienced in tissue engineering by improving a scaffold's physico-bio-chemical properties. With its piezoelectric property, bone is an active tissue with easy adaptation and remodeling through complicated mechanisms of electromechanical operations. Although poly(ε-caprolactone) (PCL) is an excellent polymer for bone tissue engineering, it is lack of conductivity. In this study, piezoelectric barium titanates (BaTiO3) and boron nitride nanotubes (BNNTs) are used as ultrasound (US) stimulated piezoelectric components in PCL to mimic piezoelectric nature of bone tissue. Electric-responsive Human Osteoblast cells on the scaffolds were stimulated by applying low-frequency US during cell growth. Biocompatibility, cell adhesion, alkaline phosphatase activities and mineralization of osteoblast cells on piezo-composite scaffolds were investigated. BaTiO3or BNNTs as reinforcement agents improved physical and mechanical properties of PCL scaffolds.In vitrostudies show that the use of BaTiO3or BNNTs as additives in non-conductive scaffolds significantly induces and increases the osteogenic activities even without US stimulation. Although BaTiO3is one of the best piezoelectric materials, the improvement is more dramatic in the case of BNNTs with the increased mineralization, and excellent chemical and mechanical properties.

Esophagogastric Junction Outflow Obstruction (EGJOO): A Manometric Phenomenon or Clinically Impactful Problem.

PURPOSE OF REVIEW: Esophagogastric junction outflow obstruction (EGJOO), defined manometrically by impaired esophagogastric junction relaxation (EGJ) with preserved peristalsis, can be artifactual, due to secondary etiologies (mechanical, medication-induced), or a true motility disorder. The purpose of this review is to go over the evolving approach to diagnosing and treating clinically relevant EGJOO. RECENT FINDINGS: Timed barium esophagram (TBE) and the functional lumen imaging probe (FLIP) are useful to identify clinically relevant EGJOO that merits lower esophageal sphincter (LES) directed therapies. There are no randomized controlled trials evaluating EJGOO treatment. Uncontrolled trials show effectiveness for pneumatic dilation and peroral endoscopic myotomy to treat confirmed EGJOO; Botox and Heller myotomy may also be considered but data for confirmed EGJOO is more limited. Diagnosis of clinically relevant idiopathic EGJOO requires symptoms, exclusion of mechanical and medication-related etiologies, and confirmation of EGJ obstruction by TBE or FLIP. Botox LES injection has limited durability, it can be used in patients who are not candidates for other treatments. PD and POEM are effective in confirmed EGJOO, Heller myotomy may also be considered but data for confirmed EGJOO is limited. Randomized controlled trials are needed to clarify optimal management of EGJOO.

Hiatal hernia reporting: time to remove subjectivity?

INTRODUCTION: The size of a hiatal hernia (HH) is a key determinant of the approach for surgical repair. However, endoscopists will often utilize subjective terms, such as "small," "medium," and "large," without any standardized objective correlations. The aim of this study was to identify HHs described using objective axial length measurements versus subjective size allocations and compare them to their corresponding manometry and barium swallow studies. METHODS AND PROCEDURES: Retrospective chart reviews were conducted on 93 patients diagnosed endoscopically with HHs between 2017 and 2021 at Newton-Wellesley Hospital. Information was collected regarding their HH subjective size assessment, axial length measurement (cm), manometry results, and barium swallow readings. Linear regression models were used to analyze the correlation between the objective endoscopic axial length measurements and manometry measurements. Ordered logistic regression models were used to correlate the ordinal endoscopic and barium swallow subjective size allocations with the continuous axial length measurements and manometry measurements. RESULTS: Of the 93 endoscopy reports, 42 included a subjective size estimate, 38 had axial length measurement, and 12 gave both. Of the 34 barium swallow reads, only one gave an objective HH size measurement. Axial length measurements were significantly correlated with the manometry measurements (R2 = 0.0957, p = 0.049). The endoscopic subjective size estimates were also closely related to the manometry measurements (R2 = 0.0543, p = 0.0164). Conversely, the subjective size estimates from barium swallow reads were not significantly correlated with the endoscopic axial length measurements (R2 = 0.0143, p = 0.366), endoscopic subjective size estimates (R2 = 0.0481, p = 0.0986), or the manometry measurements (R2 = 0.0418, p = 0.0738). Mesh placement was significantly correlated to pre-operative endoscopic axial length measurement (p = 0.0001), endoscopic subjective size estimate (p = 0.0301), and barium swallow read (p = 0.0211). However, mesh placement was not significantly correlated with pre-operative manometry measurements (0.2227). CONCLUSIONS: Endoscopic subjective size allocations and objective axial length measurements are associated with pre-operative objective measurements and intra-operative decisions, suggesting both can be used to guide clinical decision making. However, including axial length measurements in endoscopy reports can improve outcomes reporting.

Modular air-liquid interface aerosol exposure system (MALIES) to study toxicity of nanoparticle aerosols in 3D-cultured A549 cells in vitro.

We present a novel lung aerosol exposure system named MALIES (modular air-liquid interface exposure system), which allows three-dimensional cultivation of lung epithelial cells in alveolar-like scaffolds (MatriGrids®) and exposure to nanoparticle aerosols. MALIES consists of multiple modular units for aerosol generation, and can be rapidly assembled and commissioned. The MALIES system was proven for its ability to reliably produce a dose-dependent toxicity in A549 cells using CuSO4 aerosol. Cytotoxic effects of BaSO4- and TiO2-nanoparticles were investigated using MALIES with the human lung tumor cell line A549 cultured at the air-liquid interface. Experiments with concentrations of up to 5.93 × 105 (BaSO4) and 1.49 × 106 (TiO2) particles/cm3, resulting in deposited masses of up to 26.6 and 74.0 µg/cm2 were performed using two identical aerosol exposure systems in two different laboratories. LDH, resazurin reduction and total glutathione were measured. A549 cells grown on MatriGrids® form a ZO-1- and E-Cadherin-positive epithelial barrier and produce mucin and surfactant protein. BaSO4-NP in a deposited mass of up to 26.6 µg/cm2 resulted in mild, reversible damage (~ 10% decrease in viability) to lung epithelium 24 h after exposure. TiO2-NP in a deposited mass of up to 74.0 µg/cm2 did not induce any cytotoxicity in A549 cells 24 h and 72 h after exposure, with the exception of a 1.7 fold increase in the low exposure group in laboratory 1. These results are consistent with previous studies showing no significant damage to lung epithelium by short-term treatment with low concentrations of nanoscale BaSO4 and TiO2 in in vitro experiments.

Clinical Implementation of DIGEST as an Evidence-Based Practice Tool for Videofluoroscopy in Oncology: A Six-Year Single Institution Implementation Evaluation.

Clinical implementation of evidence-based practice (EBP) tools is a healthcare priority. The Dynamic Grade of Swallowing Toxicity (DIGEST) is an EBP tool developed in 2016 for videofluoroscopy in head and neck (H&N) oncology with clinical implementation as a goal. We sought to examine: (1) feasibility of clinical implementation of DIGEST in a national comprehensive cancer center, and (2) fidelity of DIGEST adoption in real-world practice. A retrospective implementation evaluation was conducted in accordance with the STARI framework. Electronic health record (EHR) databases were queried for all consecutive modified barium swallow (MBS) studies conducted at MD Anderson Cancer Center from 2016 to 2021. Implementation outcomes included: feasibility as measured by DIGEST reporting in EHR (as a marker of clinical use) and fidelity as measured by accuracy of DIGEST reporting relative to the decision-tree logic (penetration-aspiration scale [PAS], residue, and Safety [S] and Efficiency [E] grades). Contextual factors examined included year, setting, cancer type, MBS indication, and provider. 13,055 MBS were conducted by 29 providers in 7,842 unique patients across the lifespan in diverse oncology populations (69% M; age 1-96 years; 58% H&N cancer; 10% inpatient, 90% outpatient). DIGEST was reported in 12,137/13,088 exams over the 6-year implementation period representing 93% (95% CI: 93-94%) adoption in all exams and 99% (95% CI: 98-99%) of exams excluding the total laryngectomy population (n = 730). DIGEST reporting varied modestly by year, cancer type, and setting/provider (> 91% in all subgroups, p < 0.001). Accuracy of DIGEST reporting was high for overall DIGEST (incorrect SE profile 1.6%, 200/12,137), DIGEST-safety (incorrect PAS 0.4% 51/12,137) and DIGEST-efficiency (incorrect residue 1.2%, 148/12,137). Clinical implementation of DIGEST was feasible with high fidelity in a busy oncology practice across a large number of providers. Adoption of the tool across the lifespan in diverse cancer diagnoses may motivate validation beyond H&N oncology.

Direct Observation of Trace Elements in Barium Titanate of Multilayer Ceramic Capacitors Using Atom Probe Tomography.

Accurately controlling trace additives in dielectric barium titanate (BaTiO3) layers is important for optimizing the performance of multilayer ceramic capacitors (MLCCs). However, characterizing the spatial distribution and local concentration of the additives, which strongly influence the MLCC performance, poses a significant challenge. Atom probe tomography (APT) is an ideal technique for obtaining this information, but the extremely low electrical conductivity and piezoelectricity of BaTiO3 render its analysis with existing sample preparation approaches difficult. In this study, we developed a new APT sample preparation method involving W coating and heat treatment to investigate the trace additives in the BaTiO3 layer of MLCCs. This method enables determination of the local concentration and distribution of all trace elements in the BaTiO3 layer, including additives and undesired impurities. The developed method is expected to pave the way for the further optimization and advancement of MLCC technology.

Significant Oxygen Underestimation When Quantifying Barium-Doped SrTiO Layers by Atom Probe Tomography.

In this paper, the capability for quantifying the composition of Ba-doped SrTiO layers from an atom probe measurement was explored. Rutherford backscattering spectrometry and time-of-flight/energy elastic recoil detection were used to benchmark the composition where the amount of titanium was intentionally varied between samples. The atom probe results showed a significant divergence from the benchmarked composition. The cause was shown to be a significant oxygen underestimation (≳14 at%). The ratio between oxygen and titanium for the samples varied between 2.6 and 12.7, while those measured by atom probe tomography were lower and covered a narrower range between 1.4 and 1.7. This difference was found to be associated with the oxygen and titanium predominantly field evaporating together as a molecular ion. The evaporation fields and bonding chemistries determined showed inconsistencies for explaining the oxygen underestimation and ion species measured. The measured ion charge state was in excellent agreement with that predicted by the Kingham postionization theory. Only by considering the measured ion species, their evaporation fields, the coordination chemistry, the analysis conditions, and some recently reported density functional theory modeling for oxide field emission were we able to postulate a field emission and oxygen neutral desorption process that may explain our results.

Engineering Refractive Index Contrast in Thin Film Barium Titanate-on-Insulator.

Barium titanate-on-insulator has demonstrated excellent vertical optical confinement, low loss, and strong electro-optic properties. To fabricate a waveguide-based device, a region of higher refractive index must be created to confine a propagating mode, one way of which is through dry etching to form a ridge. However, despite recent progress achieved in etching barium titanate and similar materials, the sidewall and surface roughness resulting from the physical etching typically used limit the achievable ridge depth. This motivates the exploration of etch-free methods to achieve the required index contrast. Here, we introduce three etch-free methods to create a refractive index contrast in barium titanate-on-insulator, including a metal diffusion method, proton beam irradiation method, and crystallinity control method. Notably, molybdenum-diffused barium titanate leads to a large index change of up to 0.17. The methods provided in this work can be further developed to fabricate various on-chip barium titanate optical waveguide-based devices.

Flexural strength and translucency of barium-silicate-filled resin nanoceramics for additive manufacturing.

OBJECTIVE: This in vitro study aimed to evaluate the flexural strength (FS) and translucency parameter (TP) of resin nanoceramics (RNCs) with barium silicate for additive manufacturing. MATERIALS AND METHODS: An RNC slurry was prepared by mixing a barium silicate filler and resin monomer. For the FS tests, specimens with three filler contents (0, 50, and 63 wt%) were designed according to ISO6872 for dental ceramics and ISO10477 for dental polymers. These specimens were then formed into discs with thicknesses of 1 and 2 mm for TP measurement. RESULTS: In the specimens prepared according to ISO6872, the FS increased significantly depending on the filler content. However, in the case of ISO10477, there was no significant difference between the FSs of the specimens with 0 and 50 wt% filler contents. The increase in thickness affected translucency, and the lowest translucency was obtained at a filler content of 63 wt%. The filler distribution was dense in the specimen with 63 wt% filler and uniform but relatively sparse in the specimen with 50 wt% filler. More voids were observed in the specimen with 63 wt% filler. The thickness and filler content of the specimen affected its TP. The TP of the specimen with 63 wt% filler was similar to that of human enamel. CONCLUSION: The FS was significantly higher at a filler content of 63 wt%. The lowest translucency was obtained at a filler content of 63 wt% for all tested thicknesses. CLINICAL SIGNIFICANCE: Increasing the filler content was advantageous for the mechanical properties of the RNCs. A high filler content led to low translucency in the RNCs. Therefore, the esthetics of human teeth can be reproduced if layering according to the filler content is performed in areas where esthetic characteristics are required.

Charge Storage Properties of Ferrimagnetic BaFe12O19 and Polypyrrole-BaFe12O19 Composites.

This investigation is motivated by an interest in multiferroic BaFe12O19 (BFO), which combines advanced ferrimagnetic and ferroelectric properties at room temperature and exhibits interesting magnetoelectric phenomena. The ferroelectric charge storage properties of BFO are limited due to high coercivity, low dielectric constant, and high dielectric losses. We report the pseudocapacitive behavior of BFO, which allows superior charge storage compared to the ferroelectric charge storage mechanism. The BFO electrodes show a remarkably high capacitance of 1.34 F cm-2 in a neutral Na2SO4 electrolyte. The charging mechanism is discussed. The capacitive behavior is linked to the beneficial effect of high-energy ball milling (HEBM) and the use of an efficient dispersant, which facilitates charge transfer. Another approach is based on the use of conductive polypyrrole (PPy) for the fabrication of PPy-BFO composites. The choice of new polyaromatic dopants with a high charge-to-mass ratio plays a crucial role in achieving a high capacitance of 4.66 F cm-2 for pure PPy electrodes. The composite PPy-BFO (50/50) electrodes show a capacitance of 3.39 F cm-2, low impedance, reduced charge transfer resistance, enhanced capacitance retention at fast charging rates, and good cyclic stability due to the beneficial effect of advanced dopants, HEBM, and synergy of the contribution of PPy and BFO.

Effect of Ba2+ on the biomineralization of Ca2+ and Mg2+ ions induced by Bacillus licheniformis.

The effect of barium ions on the biomineralization of calcium and magnesium ions is often overlooked when utilizing microbial-induced carbonate precipitation technology for removing barium, calcium, and magnesium ions from oilfield wastewater. In this study, Bacillus licheniformis was used to bio-precipitate calcium, magnesium, and barium ions. The effects of barium ions on the physiological and biochemical characteristics of bacteria, as well as the components of extracellular polymers and mineral characteristics, were also studied in systems containing coexisting barium, calcium, and magnesium ions. The results show that the increasing concentrations of barium ions decreased pH, carbonic anhydrase activity, and concentrations of bicarbonate and carbonate ions, while it increased the contents of humic acids, proteins, polysaccharides, and DNA in extracellular polymers in the systems containing all three types of ions. With increasing concentrations of barium ions, the content of magnesium within magnesium-rich calcite and the size of minerals precipitated decreased, while the full width at half maximum of magnesium-rich calcite, the content of O-C=O and N-C=O, and the diversity of protein secondary structures in the minerals increased in systems containing all three coexisting ions. Barium ions does inhibit the precipitation of calcium and magnesium ions, but the immobilized bacteria can mitigate the inhibitory effect. The precipitation ratios of calcium, magnesium, and barium ions reached 81-94%, 68-82%, and 90-97%. This research provides insights into the formation of barium-enriched carbonate minerals and offers improvements for treating oilfield wastewater.

Metal Vapour Synthesis of an Organometallic Barium(0) Synthon.

A hydrocarbon-soluble barium anthracene complex was prepared by means of metal vapour synthesis. Reaction of 9,10-bis(trimethylsilyl)anthracene (Anth'') with barium vapour gave deep purple Ba(Anth'') which after extraction with diethyl ether crystallised as the cyclic octamer [Ba(Anth'')⋅Et2 O]8 . Dissolution in benzene or toluene led to replacement of the Et2 O ligand with a softer arene ligand and isolation of Ba(Anth'')⋅arene. Diffusion ordered spectroscopy (DOSY NMR ) measurements in benzene-d6 indicate solution species with a molecular weight that equals a trimeric constitution. Natural population analysis (NPA) assigned charges of +1.70 and -1.70 to Ba and Anth'', respectively, relating to highly ionic Ba2+ /Anth''2- bonding. Preliminary reactivity studies with air, Ph2 C=NPh, or H2 show that the complex reacts as a Ba0 synthon by release of neutral Anth''. This soluble molecular Ba0 /BaII redox synthon provides new routes for the syntheses of barium complexes under mild conditions.

Esophageal Motility Disorders: Current Approach to Diagnostics and Therapeutics.

Dysphagia is a common symptom with significant impact on quality of life. Our diagnostic armamentarium was primarily limited to endoscopy and barium esophagram until the advent of manometric techniques in the 1970s, which provided the first reliable tool for assessment of esophageal motor function. Since that time, significant advances have been made over the last 3 decades in our understanding of various esophageal motility disorders due to improvement in diagnostics with high-resolution esophageal manometry. High-resolution esophageal manometry has improved the sensitivity for detecting achalasia and has also enhanced our understanding of spastic and hypomotility disorders of the esophageal body. In this review, we discuss the current approach to diagnosis and therapeutics of various esophageal motility disorders.

A Comprehensive Review on Barium Titanate Nanoparticles as a Persuasive Piezoelectric Material for Biomedical Applications: Prospects and Challenges.

Stimulation of cells with electrical cues is an imperative approach to interact with biological systems and has been exploited in clinical practices over a wide range of pathological ailments. This bioelectric interface has been extensively explored with the help of piezoelectric materials, leading to remarkable advancement in the past two decades. Among other members of this fraternity, colloidal perovskite barium titanate (BaTiO3 ) has gained substantial interest due to its noteworthy properties which includes high dielectric constant and excellent ferroelectric properties along with acceptable biocompatibility. Significant progression is witnessed for BaTiO3 nanoparticles (BaTiO3 NPs) as potent candidates for biomedical applications and in wearable bioelectronics, making them a promising personal healthcare platform. The current review highlights the nanostructured piezoelectric bio interface of BaTiO3 NPs in applications comprising drug delivery, tissue engineering, bioimaging, bioelectronics, and wearable devices. Particular attention has been dedicated toward the fabrication routes of BaTiO3 NPs along with different approaches for its surface modifications. This review offers a comprehensive discussion on the utility of BaTiO3 NPs as active devices rather than passive structural unit behaving as carriers for biomolecules. The employment of BaTiO3 NPs presents new scenarios and opportunity in the vast field of nanomedicines for biomedical applications.

Shape-Tunable BaTiO3 Crystals Presenting Facet-Dependent Optical and Piezoelectric Properties.

BaTiO3 octahedra, edge-, and corner-truncated cubes, and cubes with four tunable sizes from 132 to 438 nm are synthesized by a solvothermal growth approach. Acetic acid treatment can cleanly remove BaCO3 impurity. Rietveld refinement of X-ray diffraction patterns and Raman spectra help to confirm the particles have a tetragonal crystal structure. The crystals also exhibit size- and facet-dependent bandgap shifts. BaTiO3 octahedra show larger piezoelectric, ferroelectric, and pyroelectric effects than truncated cubes and cubes. The measured dielectric constant differences should be associated with their various facet-dependent behaviors. Piezoelectric nanogenerators fabricated from BaTiO3 octahedra consistently show the best performance than those containing truncated cubes and cubes. In particular, a nanogenerator with 30 wt.%-incorporated octahedra displays an open-circuit voltage of 23 V and short-circuit current of 324 nA. The device performance is also highly stable. The maximum output power reaches 3.9 µW at 60 MΩ. The fabricated nanogenerator can provide sufficient electricity to power light-emitting diodes. This work further demonstrates that various physical properties of semiconductor crystals show surface dependence.

Charge Separation in BaTiO3 Nanocrystals: Spontaneous Polarization Versus Point Defect Chemistry.

The fate of photogenerated charges within ferroelectric metal oxides is key for photocatalytic applications. The authors study the contributions of i) tetragonal distortion, responsible for spontaneous polarization, and ii) point defects, on charge separation and recombination within BaTiO3 (BTO) nanocrystals of cubic and tetragonal structure. Electron paramagnetic resonance (EPR) in combination with O2 photoadsorption experiments show that BTO nanocrystals annealed at 600 °C have a charge separation yield enhanced by a factor > 10 compared to TiO2 anatase nanocrystals of similar geometries. This demonstrates for the first time the beneficial effect of the BTO perovskite nanocrystal lattice on charge separation. Strikingly, charge separation is considerably hindered within BTO nanoparticles annealed ≥ 600 °C, due to the formation of Ba-O divacancies that act as charge recombination centers. The opposing interplay between tetragonal distortion and annealing-induced defect formation inside the lattice highlights the importance of defect engineering within perovskite nanoparticles.