Bandgap-engineered ferroelectric single-crystalline NBT-BT based nanocomposites with excellent visible light-ultrasound catalytic performance.

Bandgap engineered ferroelectrics exhibit encouraging multi-energy catalytic performance by coupling the piezoelectricity and photoexcitation, which shows immense potential for environmental remediation and fuel production. However, it is challenging to prepare nano single-crystalline ferroelectric piezo-photoelectric with strong visible light absorption ability. Here, Ni mediated NBT-BT(NBT-BNT) single-crystalline nanocubes around 100 nm with considerable visible light absorption were synthesized by a high-temperature hydrothermal method. The mechanism of Ni2+ on the formation of NBT-BT nanocubes was proposed. The catalytic efficiency of NBT-BNT nanocubes is enhanced by decorating carbon quantum dots (CQDs). The RhB can be degraded within 8 min and the hydrogen production rate reaches up to ∼350 µmol g-1h-1 under visible light-ultrasonic condition. Moreover, under the simulated sunlight-ultrasound condition, RhB can be degraded within merely 3 min and a high H2 production rate of ∼747 µmol g-1h-1 is achieved. This work presents a paradigm for preparing ferroelectric single-crystalline nanocatalysts for multi-energy catalytic application.

Engineering the Defects and Microstructures in Ferroelectrics for Enhanced/Novel Properties: An Emerging Way to Cope with Energy Crisis and Environmental Pollution.

In the past century, ferroelectrics are well known in electroceramics and microelectronics for their unique ferroelectric, piezoelectric, pyroelectric, and photovoltaic effects. Nowadays, the advances in understanding and tuning of these properties have greatly promoted a broader application potential especially in energy and environmental fields, by harvesting solar, mechanical, and heat energies. For example, high piezoelectricity and high pyroelectricity can be designed by defect or microstructure engineering for piezo- and pyro-catalyst, respectively. Moreover, highly piezoelectric and broadband (UV-Vis-NIR) light-responsive ferroelectrics can be designed via defect engineering, giving rise to a new concept of photoferroelectrics for efficient photocatalysis, piezocatalysis, pyrocatalysis, and related cocatalysis. This article first summarizes the recent developments in ferroelectrics in terms of piezoelectricity, pyroelectricity, and photovoltaic effects based on defect and microstructure engineering. Then, the potential applications in energy generation (i.e., photovoltaic effect, H2 generation, and self-powered multisource energy harvesting and signal sensing) and environmental protection (i.e., photo-piezo-pyro- cocatalytic dye degradation and CO2 reduction) are reviewed. Finally, the outlook and challenges are discussed. This article not only covers an overview of the state-of-art advances of ferroelectrics, but also prospects their applications in coping with energy crisis and environmental pollution.

Superflexible and Lead-Free Piezoelectric Nanogenerator as a Highly Sensitive Self-Powered Sensor for Human Motion Monitoring.

For traditional piezoelectric sensors based on poled ceramics, a low curie temperature (Tc) is a fatal flaw due to the depolarization phenomenon. However, in this study, we find the low Tc would be a benefit for flexible piezoelectric sensors because small alterations of force trigger large changes in polarization. BaTi0.88Sn0.12O3 (BTS) with high piezoelectric coefficient and low Tc close to human body temperature is taken as an example for materials of this kind. Continuous piezoelectric BTS films were deposited on the flexible glass fiber fabrics (GFF), self-powered sensors based on the ultra-thin, superflexible, and polarization-free BTS-GFF/PVDF composite piezoelectric films are used for human motion sensing. In the low force region (1-9 N), the sensors have the outstanding performance with voltage sensitivity of 1.23 V N-1 and current sensitivity of 41.0 nA N-1. The BTS-GFF/PVDF sensors can be used to detect the tiny forces of falling water drops, finger joint motion, tiny surface deformation, and fatigue driving with high sensitivity. This work provides a new paradigm for the preparation of superflexible, highly sensitive and wearable self-powered piezoelectric sensors, and this kind of sensors will have a broad application prospect in the fields of medical rehabilitation, human motion monitoring, and intelligent robot.

Visible/near-infrared light absorbed nano-ferroelectric for efficient photo-piezocatalytic water splitting and pollutants degradation.

The band structure of ferroelectrics can be modulated by mechanical stress induced piezoelectric polarization charges, and thus to promote the separation of photo-excited carriers, endowing photo-piezocatalysts with good performance in hydrogen production and pollutants degradation. However, the catalytic performance of these conventional photo-piezocatalysts is restricted since they mainly harvest UV light and generally have limited piezoelectricity. Here, in this study, by using self-propagation high-temperature synthesis process, highly piezoelectric gap-state-engineered nano relaxor ferroelectric at the morphotropic phase boundary, such as (Na0.5Bi0.5)TiO3-Ba(Ti0.5Ni0.5)O3 is synthesized for the first time and shows unprecedently light harvesting from UV to near-infrared (λ < 1300 nm). We demonstrate a significantly enhanced photo-piezocatalytic performance for this photo-piezocatalyst. A high hydrogen production rate of ~ 450 µmol g-1 h-1 is obtained and the decomposition of Rhodamine B dye is nearly completed after 20 min under irradiation and ultrasonic vibration. Moreover, an unprecedently efficient NIR-driven photocatalytic degradation of RhB is also demonstrated by using photo-piezocatalysts. This kind of novel multifunctional nano photo-piezocatalysts opens up new horizons to all-day available photo-piezocatalytic technology for a more efficient use of multisource energies from environment.

Visible or Near-Infrared Light Self-Powered Photodetectors Based on Transparent Ferroelectric Ceramics.

Transparent ferroelectrics, with promising prospects in transparent optoelectronic devices, have unique advantages in self-powered photodetection. The self-powered photodetectors based on the photovoltaic effect have quicker responses and higher stability compared with those based on the pyroelectric effect. However, the ferroelectric ceramics previously applied are always opaque and have no infrared light-stimulated photovoltaic effect. Thus, it would be very meaningful to design photodetectors based on infrared light-stimulated photovoltaic effect and/or transparent ferroelectric ceramics. In this work, highly optical transparent pristine lead lanthanum zirconate titanate (PLZT) and band gap-engineered Ni-doped PLZT ceramics with excellent piezoelectric/ferroelectric properties were prepared by hot-pressing sintering. Stable and excellent photovoltaic performance was obtained for pristine PLZT and band gap-engineered PLZT. The value of short-circuit current density is at least 2 orders of magnitude larger than those in PLZT reported in previous works. The transparent PLZT and Ni-doped PLZT ferroelectric ceramics are applied as self-powered photodetectors for the first time for 405 nm and near-infrared light, respectively. The devices based on PLZT under 405 nm light exhibit high detectivity (7.15 × 107 Jones) and quick response (9.5 ms for rise and 11.5 ms for decay), and those devices based on Ni-doped PLZT, under near-infrared light filtered from AM 1.5 G simulated sunlight, also exhibit high detectivity (6.86 × 107 Jones) and short response time (8.5 ms), both presenting great potential for future transparent photodetectors.

Design for Highly Piezoelectric and Visible/Near-Infrared Photoresponsive Perovskite Oxides.

Defect-engineered perovskite oxides that exhibit ferroelectric and photovoltaic properties are promising multifunctional materials. Though introducing gap states by transition metal doping on the perovskite B-site can obtain low bandgap (i.e., 1.1-3.8 eV), the electrically leaky perovskite oxides generally lose piezoelectricity mainly due to oxygen vacancies. Therefore, the development of highly piezoelectric ferroelectric semiconductor remains challenging. Here, inspired by point-defect-mediated large piezoelectricity in ferroelectrics especially at the morphotropic phase boundary (MPB) region, an efficient strategy is proposed by judiciously introducing the gap states at the MPB where defect-induced local polar heterogeneities are thermodynamically coupled with the host polarization to simultaneously achieve high piezoelectricity and low bandgap. A concrete example, Ni2+ -mediated (1-x)Na0.5 Bi0.5 TiO3 -xBa(Ti0.5 Ni0.5 )O3-δ (x = 0.02-0.08) composition is presented, which can show excellent piezoelectricity and unprecedented visible/near-infrared light absorption with a lowest ever bandgap ≈0.9 eV at room temperature. In particular, the MPB composition x = 0.05 shows the best ferroelectricity/piezoelectricity (d33 = 151 pC N-1 , Pr = 31.2 µC cm-2 ) and a largely enhanced photocurrent density approximately two orders of magnitude higher compared with classic ferroelectric (Pb,La)(Zr,Ti)O3 . This research provides a new paradigm for designing highly piezoelectric and visible/near-infrared photoresponsive perovskite oxides for solar energy conversion, near-infrared detection, and other multifunctional applications.

Dose-dependent effect of glucose on GLP-1 secretion involves sweet taste receptor in isolated perfused rat ileum [Rapid Communication].

Luminal glucose is an important stimulus for glucagon-like peptide 1 (GLP-1) secretion from intestinal endocrine cells. However, the effects of luminal glucose concentration on GLP-1 secretion remain unknown. In this study, we investigated the effect of luminal glucose concentrations (3.5, 5, 10, 15, and 20 mmol/L) on GLP-1 secretion from isolated perfused rat ileum. Results showed that the perfusate glucose concentration dose-dependently stimulated GLP-1 secretion from isolated perfused rat ileum, which was eliminated by the sweet taste receptor inhibitor gurmarin (30 µg/mL), but not inhibited by phloridzin (1 mmol/L), a Na+-coupled glucose transporters inhibitor. We conclude that luminal glucose induced GLP-1 secretion from perfused rat ileum in a concentration-dependent manner. This secretion was mediated by sweet taste receptor transducing signal for GLP-1 release on the gut of rat.