Single- and few-layer MoS2 nanoflowers are first discovered to have a piezo-catalyst effect, exhibiting an ultra-high degradation activity in the dark by introducing external mechanical strains. The degradation ratio of the Rhodamine-B dye solution reaches 93% within 60 s under ultrasonic-wave assistance in the dark.

ABSTRACT:We have developed a simple, cost-effective, and scalable approach to fabricate a piezoelectric nanogenerator (NG) with stretchable and flexible characteristics using BaTiO 3 nanotubes, which were synthesized by the hydrothermal method. The NG was fabricated by making a composite of the nanotubes with polymer poly(dimethylsiloxane) (PDMS). The peak open-circuit voltage and short-circuit current of the NG reached a high level of 5.5 V and 350 nA (current density of 350 nA/cm 2 ), respectively. It was used to directly drive a commercial liquid crystal display. The BaTiO 3 nanotubes/PDMS composite is highly transparent and useful for a large-scale (11 × 11 cm) fabrication of lead-free piezoelectric NG. NGs fabricated by PZT nanofibers 16 and nanowires 17 have been demonstrated to provide output voltages of 1.63 and 0.7 V, respectively. However, the component lead in PZT has the concern of toxic effect toward human health and environmental problems.18 Consequently, it has motivated the search for perovskite piezoelectric materials with lead-free properties comparable to PZT with a reduced environmental impact. BaTiO 3 thin-film-based NG fabricated by soft lithographic printing technique can produce an output voltage of 1.0 V and current density of 0.19 μA/cm 2 . 19 Although the abovementioned result is outstanding, there is no report about using BaTiO 3 nanotubes to fabricate a NG. As the size of the piezoelectric materials is reduced to the nanoscale, the conversion efficiency of mechanical energy has been found to be improved dramatically, attributing to the larger piezoelectric coefficients and deformations, which are proportional to the generated potential. 20−22 In this letter, lead-free BaTiO 3 nanotubes were used to fabricate the piezoelectric NG. A large number of high-quality BaTiO 3 nanotubes were synthesized through a hydrothermal method. By forming a composite of BaTiO 3 nanotubes with poly(dimethylsiloxane) (PDMS) polymer, flexible and transparent NG was developed easily after applying a direct poling process. Under periodic external mechanical deformation by a linear motor, we obtained very stable and high output piezoelectric signals, that is, an open-circuit voltage (V oc ) of 5.5 V and short-circuit current (I sc ) exceeding 350 nA. The NG was further demonstrated to be easily scaled-up over 11 × 11 cm and can continuously drive a commercial LCD under the biomechanical movements of a human skin.The NG mainly consists of five layers as schematically shown in Figure 1a. The deposited Au/Cr films act as top and bottom electrodes, and the BaTiO 3 nanotubes and PDMS composite mixed with a 3 wt % ratio serve as the source of piezoelectric potential generation under external stress. The polystyrene (PS) substrate and pure PDMS worked as the supporting and protecting layers to sustain the conformation of NG. Figure 1b shows the cross-sectional scanning electron microscope (SEM) image of a 300 μm thick BaTiO 3 nanotubes/PDMS composite, which demonstrates the flexible property of the developed NG. ...

We demonstrate a thermoelectric nanogenerator (NG) made from a single Sb-doped ZnO micro/nanobelt that generates an output power of about 1.94 nW under a temperature difference of 30 K between the two electrodes. A single Sb-doped ZnO microbelt was bonded at its ends on a glass substrate as a NG, which can give an output voltage of 10 mV and an output current of 194 nA. The single Sb-doped ZnO microbelt shows a Seebeck coefficient of about -350 μV/K and a high power factor of about 3.2 × 10(-4) W/mK(2). The fabricated NG demonstrated its potential to work as a self-powered temperature sensor with a reset time of about 9 s.

We demonstrated a flexible strain sensor based on ZnSnO(3) nanowires/microwires for the first time. High-resolution transmission electron microscopy indicates that the ZnSnO(3) belongs to a rhombohedral structure with an R3c space group and is grown along the [001] axis. On the basis of our experimental observation and theoretical calculation, the characteristic I-V curves of ZnSnO(3) revealed that our strain sensors had ultrahigh sensitivity, which is attributed to the piezopotential-modulated change in Schottky barrier height (SBH), that is, the piezotronic effect. The on/off ratio of our device is ∼587, and a gauge factor of 3740 has been demonstrated, which is 19 times higher than that of Si and three times higher than those of carbon nanotubes and ZnO nanowires.