Triboelectric nanogenerators (TENGs) represent an emerging technology in energy harvesting, medical treatment, and information technology. Flexible, portable, and self-powered electronic devices based on TENGs are much desired, whereas the complex preparation processes and high cost of traditional flexible electrodes hinder their practical applications. Here, an MXene/polyvinyl alcohol (PVA) hydrogel TENG (MH-TENG) is presented with simple fabrication, high output performance, and versatile applications. The doping of MXene nanosheets promotes the crosslinking of the PVA hydrogel and improves the stretchability of the composite hydrogel. The MXene nanosheets also form microchannels on surfaces, which not only enhances the conductivity of the hydrogel by improving the transport of ions but also generates an extra triboelectric output via a streaming vibration potential mechanism. The measured open-circuit voltage of the MH-TENG reaches up to 230 V even in a single-electrode mode. The MH-TENG can be stretched up to 200% of the original length and demonstrates a monotonical increasing relationship between the stretchable length and the short-circuit voltage. By utilizing the MH-TENG's outstanding stretchable property and ultrahigh sensitivity to mechanical stimuli, applications in wearable movement monitoring, high-precision written stroke recognition, and low-frequency mechanical energy harvesting are demonstrated.
Phosphorus stored in lake sediments is an inner nutrient source and can be released into overlying water to exacerbate algal blooms. A simulated microcosm of Dianchi Lake was built to investigate phosphorus release from sediments to overlying water and its effect on the growth of Microcystis aeruginosa. The sediments of Dianchi Lake had a total phosphorus (TP) content of 1.7-1.8 mg g(-1) with Ca bound phosphorus (Ca-P, 50-54 %) and organic phosphorus (Org-P, 28-32 %) as the main fractions. The sediments released 8 % of TP into the overlying water with Fe/Al bound phosphorus (Fe/Al-P, 26 %) and Org-P (65 %) being the main fractions released. The phosphorus concentration of the overlying water increased from 0.14-0.16 to 0.28-0.33 mg L(-1). The biomass density of M. aeruginosa was positively correlated (R (2) = 0.825) with the concentration of orthophosphate, which was the predominant bioavailable phosphorus fraction for algal growth. Org-P can be partly utilized by M. aeruginosa but will not cause a bloom. A good understanding of the geochemical cycles of phosphorus is needed for regulating phosphorus release from sediments and thereby reducing the risk of cyanobacterial blooms.
Tribovoltaic nanogenerators (TVNGs), an emerging high‐entropy energy harvesting technique, present great features such as low matching resistance, high current density, and continuous output performance. Here, an MXene layer and a semiconducting silicon wafer are assembled into a tribovoltaic nanogenerator (named MS‐TVNG). The output peak current of the MS‐TVNG reaches up to 22 µA for a P‐type (0.1–0.5 Ω cm) silicon wafer under a normal force of 4.56 N and a sliding speed of 2 m s−1. Owing to the unique metal characteristics of the MXene layer, the performance is superior to those previously reported TVNGs using traditional metals. The layered structure of MXene endows the real‐time MS‐TVNG with outstanding wear‐resistance and stable output properties. The performance of the MS‐TVNG can be tuned by the doping type and concentration of the silicon wafer, as well as by the pressure and the relative sliding speed between two friction surfaces. The MS‐TVNG has proven to be a solid foundation for high‐performance self‐powered speed sensors and has excellent potentials for applications in displacement, tension, oscillation angle, and vibration detection.
The related studies and applications of ZnS-based phosphorescent materials involve various aspects such as lighting, display, sensing, electronic signatures, and confidential information. Here, triboelectrification-induced electroluminescence (TIEL) of the ZnS:Cu due to the triboelectric leakage field is discovered via a gently horizontal sliding between a ZnS:Cu particle-doped polydimethylsiloxane (PDMS) film and a polytetrafluoroethylene (PTFE) or fluorinated ethylene propylene (FEP) film, whose intensity is positively correlated with the temperature, the doping ratio of ZnS:Cu, the pressure, and the frequency. It is also demonstrated that the TIEL mainly occurs inside the bulk film, where the ZnS:Cu phosphor particles can be polarized instantaneously by the leakage electric field of triboelectrification. The polarization will lead to a tilted energy band of the ZnS, resulting in an emitting of green light due to electrons detrapped into the conduction band and recombined with holes in the impurity state. This study not only reveals great fundamental physics for understanding of luminescence induced by a simple sliding between two triboelectric materials but also indicates another way for triboelectrification to be used in advanced optoelectronic devices.
Tribovoltaic nanogenerators (TVNGs) are an emerging class of devices for high-entropy energy conversion and mechanical sensing that benefit from their outstanding real-time direct current output characteristics. Here, a self-powered TVNG was fabricated using a small-area 4H-SiC semiconductor wafer and a large-area copper foil. Thus, the cost of materials remains low compared to devices employing large-scale semiconductors. The 4H-SiC/metal-TVNGs (SM-TVNGs) presented here are sensitive to vertical force and sliding velocity, making them appropriate for mechanical sensing. Notably, owing to the modulated bindingtons and surface states, these SM-TVNGs performed well in a harsh environment, namely, in high-temperature and high-humidity conditions. In addition, the SM-TVNGs exhibited an excellent wear-resisting property. On these bases, we designed a self-powered and real-time monitoring device able to estimate the number of staff present in various areas of a deep mining site, a high-temperature and high-humidity environment. This work not only discloses basic physics behind the tribovoltaic effect but also sheds light on possible applications of SM-TVNGs for wearresisting and stable mechanical sensors in harsh environments.
Triboelectric nanogenerators (TENGs) are demonstrated to possess great superiority in the field of low-frequency and high-entropy energy harvesting. Here, a kind of friction material, super-light clay (SLC), with outstanding stretchability and shape/size changeability is introduced to develop contact-separation triboelectric nanogenerators (SLC-TENGs), which exhibit outstanding flexible, shape-changeable, and adaptable properties but simple preparation processes. A high and stable electrical output can be achieved from the simple-structured SLC-TENG. The peak power density of the SLC-TENG output reaches up to 0.33 W/m2 under an effective contact with an area of 9 cm2 and an external load resistance of 50 MΩ. In addition, a balloon-structured TENG was also prepared with the filling of several SLC balls. The electrical signals can be generated even just by a slight shaking, revealing great application potential in the Internet of Things systems and self-powered sensors by energy harvesting from wind, ocean, human body movements, etc.
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