2D WS2 embedded PVDF nanocomposites for photosensitive piezoelectric nanogenerators with a colossal energy conversion efficiency of ∼25.6

PVDF-HFP encapsulated WS2nanosheets in droplet-based triboelectric nanogenerators for possible detection of human Na+/K+ion concentration

Here we report the liquid-solid interaction in droplet-based triboelectric nanogenerators (TENG) for estimation of human Na+/K+levels. The exploitation of PVDF-HFP encapsulated WS2as active layer in the droplet-based TENG (DTENG) leads to the generation of electrical signal during the impact of water droplet. Comparison over the control devices indicates that surface quality and dielectric nature of the PVDF-HFP/WS2composite largely dictates the performance of the DTENG. The demonstration of excellent sensitivity of the DTENG towards water quality indicates its promising application towards water testing. In addition, the alteration in output signal with slightest variation in ionic concentration (Na+or K+) in water has been witnessed and is interpreted with charge transfer and ion transfer processes during liquid-solid interaction. The study reveals that the ion mobility largely affects the ion adsorption process on the active layer of PVDF-HFP/WS2and thus generates distinct output profiles for diverse ions like Na+and K+. Following that, the DTENG characteristics have been exploited to artificial urine where the varying output signals have been recorded for variation in urinary Na+ion concentration. Therefore, the deployment of PVDF-HFP/WS2in DTENG holds promising application towards the analyse of ionic characteristics of body fluids.

Energy storage and catalytic behaviour of cmWave assisted BZT and flexible electrospun BZT fibers for energy harvesting applications

High-performance lead-free Barium Zirconium Titanate (BZT) based ceramics have emerged as a potential candidate for applications in energy storage, catalysis for electro chemical energy conversion and energy harvesting devices as presented in this work. In the present study hybrid microwave sintered BZT are studied for dielectric, ferroelectric and phase transition properties. BZT ceramic exhibits tetragonal structure as confirmed by the Retvield refinement studies. XPS studies confirms the elemental composition of BZT and presence of Zr. Polarization versus electric field hysteresis loops confirms the ferroelectric behaviour of BZT ceramic. Encouragingly, the BZT showed a moderate energy storage efficiency of 30.7 % and relatively good electro chemical energy conversion (HER). Excellent catalytic activity observed for BZT electrode in acid medium with low Tafel slope 77 mV dec-1. Furthermore, electrospun nanofibers made of PVDF-HFP and BZT are used to make flexible piezoelectric nano generators (PENGs). FTIR studies show that the 16 wt% BZT composite ink exhibits a higher electroactive beta phase. The optimized open-circuit voltage and short circuit current of the flexible PENG exhibits 7Vpp and 750 nA under an applied force of 3N. Thus, flexible and self-powered BZT PENGs are alternative source of energy due to its reliability, affordability and environmental-friendly nature.

Giant Piezoelectric Output and Stability Enhancement in Piezopolymer Composites with Liquid Metal Nanofillers

Integrating nanomaterials into the polymer matrix is an effective strategy to optimize the performance of polymer-based piezoelectric devices. Nevertheless, the trade-off between the output enhancement and stability maintenance of piezoelectric composites usually leads to an unsatisfied overall performance for the high-strength operation of devices. Here, by setting liquid metal (LM) nanodroplets as the nanofillers in a poly(vinylidene difluoride) (PVDF) matrix, the as-formed liquid-solid/conductive-dielectric interfaces significantly promote the piezoelectric output and the reliability of this piezoelectric composite. A giant performance improvement featured is obtained with, nearly 1000% boosting on the output voltage (as high as 212 V), 270% increment on the piezoelectric coefficient (d33 ∼51.1 pC N-1 ) and long-term reliability on both structure and output (over 36 000 cycles). The design of a novel heterogenous interface with both mechanical matching and electric coupling can be the new orientation for developing high performance piezoelectric composite-based devices.

TMDC ternary alloy-based triboelectric nanogenerators with giant photo-induced enhancement

Multifunctional self-powered energy harvesting devices have attracted significant attention for wearable, portable, IoT and healthcare devices. In this study, we report transition metal dichalcogenide (TMDC) ternary alloy (Mo0.5W0.5S2)-based self-powered photosensitive vertical triboelectric nanogenerator (TENG) devices, where the ternary alloy functions both as a triboelectric layer and as a photoabsorbing material. The scalable synthesis of the highly crystalline Mo0.5W0.5S2 ternary alloy can overcome the limitations of binary TMDCs (MoS2, WS2) by utilizing its superior optical characteristics, enabling this semiconductor-based TENG device to simultaneously exhibit photoelectric and triboelectric properties. Benefiting from visible light absorption, this vertical TENG device generates higher triboelectric outputs and exhibits excellent power harvesting properties under visible light illumination. The open circuit voltage and short circuit currents of the devices under illumination (410 nm, 525 μW cm-2) are enhanced by 62% and 253%, respectively, while in the darkness, a very high photoresponsivity of ∼45.5 V mW-1 (voltage mode) is exhibited, indicating the superior energy harvesting potential under ultralow illumination. Furthermore, the energy harvesting ability from regular human activities and the operation as artificial e-skin expands the multi-functionality of this TENG device, paving a pathway for simultaneous mechanical and photonic energy harvesting with self-powered sensing.

Piezo-phototronic effect regulated broadband photoresponse of a-Ga2O3/ZnO heterojunction

Amorphous Ga₂O₃ (a-Ga₂O₃) films have attracted considerable attention in the field of photodetectors due to their excellent optical absorption response and photoelectric properties. However, there are few studies that have utilized the piezo-phototronic effect to regulate the broadband photoresponse of Ga₂O₃-based photodetectors. Here, a flexible a-Ga₂O₃/ZnO heterojunction was constructed, which demonstrated a broadband response range from deep ultraviolet (265 nm) to the near-infrared (1060 nm) and realized a bidirectional adjustable photocurrent response via the piezo-phototronic effect. Under 265 nm illumination and 0.5 V bias, the responsivity and detectivity of the a-Ga₂O₃/ZnO heterojunction reached up to 12.19 A W^-1 and 4.71 × 10¹¹ Jones under 0.164% compressive strain, corresponding to enhancements of 67.7% and 66.8% compared to those under a strain-free state, respectively. Moreover, the broadband photoresponse of the a-Ga₂O₃/ZnO heterojunction beyond the bandgap limit was tunable under bidirectional strain. The working mechanism of photoresponse performance for the a-Ga₂O₃/ZnO heterojunction at different wavelengths was elucidated in detail. Oxygen vacancy-assisted carrier generation was found to be influenced by the wavelength of incident light, which mainly determined the broadband photoresponse of the heterojunction. The modulation of the a-Ga₂O₃/ZnO heterojunction photodetector was interpreted in light of the strain-induced regulation of the barrier height. This work represents an important step toward the development of adjustable broadband photodetectors based on a-Ga₂O₃ films.

Two-Dimensional Metal-Organic Framework Incorporated Highly Polar PVDF for Dielectric Energy Storage and Mechanical Energy Harvesting

Here, we introduce a 2D metal-organic framework (MOF) into the poly(vinylidene fluoride) (PVDF) matrix, which has been comparatively less explored in this field. Highly 2D Ni-MOF has been synthesized in this regard via hydrothermal route and has been incorporated into PVDF matrix via solvent casting technique with ultralow filler (0.5 wt%) loading. The polar phase percentage of 0.5 wt% Ni-MOF loaded PVDF film (NPVDF) has been found to be increased to ~85% from a value of ~55% for neat PVDF. The ultralow filler loading has inhibited the easy breakdown path along with increased dielectric permittivity and hence has enhanced the energy storage performance. On the other hand, significantly enriched polarity and Young's Modulus has helped in improving its mechanical energy harvesting performance, thereby enhancing the human motion interactive sensing activities. The piezoelectric and piezo-tribo hybrid devices made up of NPVDF film have shown improved output power density of ~3.26 and 31 μW/cm² compared to those of the piezoelectric and piezo-tribo hybrid devices comprising of neat PVDF (output power density ~0.6 and 17 μW/cm², respectively). The developed composite can thus be considered an excellent candidate for multifunctional applications.

Extremely Reduced Dielectric Constant and Band Gap Enhancement in Few-Layered Tungsten Disulfide Nanosheets

Highly crystalline few-layered tungsten disulfide (WS₂) nanosheets were synthesized via a cost-effective, low-temperature hydrothermal route. X-ray diffraction and HR-TEM analysis confirmed the formation of hexagonal nanosheets with thickness of ∼6-8 nm. Raman analysis and AFM results confirmed the few-layered 2H phase of WS₂ nanosheets. The UV-vis study shows absorption peaks at 219 and 271 nm with large band gap value of ∼3.12 eV for WS₂ nanosheets. Surprisingly, WS₂ nanosheets show a dielectric constant of approximately ε' ≈ 5245, whereas bulk WS₂ material exhibits a dielectric constant of 7482373. An almost 1426-fold decrease in the value of dielectric constant for the WS₂ nanosheet is observed. Such an extreme reduction in dielectric constant and observance of large band gap in WS₂ nanosheet were observed for the first time. The present study reveals the excellent and unusual optical and dielectric properties for their potential application in optoelectronic, dielectric, solar, phosphor, and various nanoelectronic devices.