Publications

A hierarchical structure of branched TiO2 nanorods covered with TiO2 nanosheets was designed and constructed for harvesting solar energies in dye-sensitized solar cells. Vertical aligned TiO2 nanorod arrays were synthesized on fluorine-doped SnO2 (FTO) by using the electrochemically deposited ZnO nanorod arrays as a template and liquid phase deposition (LPD) method. The resultant TiO2 nanorod was used as a seed and the rutile TiO2 nanorods were firstly synthesized on the surface of anatase TiO2 nanorod by using hydrothermal method. In photocurrent-voltage measurements, 3.56% efficiency was achieved for 1.5um thick nanosheets coated TiO2 nanobranch (NB), which is about 239% higher than the original TiO2 nanorod arrays.

'Perfluoropolyethers' published in 'Encyclopedia of Nanotechnology'

'Peltier Couple' published in 'Encyclopedia of Nanotechnology'

The lithiation reaction of single ZnO nanowire (NW) electrode in a Li-ion nanobattery configuration was observed by in situ transmission electron microscopy. Upon first charge, the single-crystalline NW was transformed into a nanoglass with multiple glassy nanodomains (Gleiter, H. MRS Bulletin2009, 34, 456) by an intriguing reaction mechanism. First, partial lithiation of crystalline NW induced multiple nanocracks ∼70 nm ahead of the main lithiation front, which traversed the NW cross-section and divided the NW into multiple segments. This was followed by rapid surface diffusion of Li(+) and solid-state amorphization along the open crack surfaces. Finally the crack surfaces merged, leaving behind a glass-glass interface (GGI). Such reaction front instability also repeated in the interior of each divided segment, further subdividing the NW into different nanoglass domains (nanoamorphization). Instead of the profuse dislocation plasticity seen in SnO(2) NWs (Science2010, 330, 1515), no dislocation was seen and the aforementioned nanocracking was the main precursor to the electrochemically driven solid-state amorphization in ZnO. Ab initio tensile decohesion calculations verified dramatic lithium embrittlement effect in ZnO, but not in SnO(2). This is attributed to the aliovalency of Sn cation (Sn(IV), Sn(II)) in contrast to the electronically more rigid Zn(II) cation.

Developing low-cost and biodegradable piezoelectric nanogenerators is of great importance for a variety of applications, from harvesting low-grade mechanical energy to wearable sensors. Many of the most widely used piezoelectric materials, including lead zirconate titanate (PZT), suffer from serious drawbacks such as complicated synthesis, poor mechanical properties (e.g., brittleness), and toxic composition, limiting their development for biomedical applications and posing environmental problems for their disposal. Here, we report a low-cost, biodegradable, biocompatible, and highly compressible piezoelectric nanogenerator based on a wood sponge obtained with a simple delignification process. Thanks to the enhanced compressibility of the wood sponge, our wood nanogenerator (15 × 15 × 14 mm3, longitudinal × radial × tangential) can generate an output voltage of up to 0.69 V, 85 times higher than that generated by native (untreated) wood, and it shows stable performance under repeated cyclic compression (≥600 cycles). Our approach suggests the importance of increased compressibility of bulk materials for improving their piezoelectric output. We demonstrate the versatility of our nanogenerator by showing its application both as a wearable movement monitoring system (made with a single wood sponge) and as a large-scale prototype with increased output (made with 30 wood sponges) able to power simple electronic devices (a LED light, a LCD screen). Moreover, we demonstrate the biodegradability of our wood sponge piezoelectric nanogenerator by studying its decomposition with cellulose-degrading fungi. Our results showcase the potential application of a wood sponge as a sustainable energy source, as a wearable device for monitoring human motions, and its contribution to environmental sustainability by electronic waste reduction.

We demonstrated a single-microbelt nanogenerator first made using a ZnSnO(3) microbelt that generated an output power of ∼3 nW under a compressive and releasing strain of 0.8-1%. The ZnSnO(3) nanobelts/microbelts were synthesized using a vapor transfer process at 1173 K. The X-ray diffraction pattern shows that the microbelts belong to ZnSnO(3) with rhombohedral structure. An individual ZnSnO(3) microbelt was bonded at its ends on a flexible polystyrene substrate as a nanogenerator, which gives an output voltage and current of 100 mV and 30 nA, respectively, corresponding to an energy conversion efficiency of 4.2-6.6% (based on 0.8-1% strain). Our results show that ZnSnO(3) microbelts are one of the highly promising materials for lead-free piezoelectric energy harvesting.

Abstract Harnessing random micromeso-scale ambient energy is not only clean and sustainable, but it also enables self-powered sensors and devices to be realized. Here we report a robust and self-powered kinematic vector sensor fabricated using highly pliable organic films that can be bent to spread over curved and uneven surfaces. The device derives its operational energy from a close-proximity triboelectrification of two surfaces: a polytetrafluoroethylene film coated with a two-column array of copper electrodes that constitutes the mover and a polyimide film with the top and bottom surfaces coated with a two-column aligned array of copper electrodes that comprises the stator. During relative reciprocations, the electrodes in the mover generate electric signals of ±5 V to attain a peak power density of ≥65 mW m −2 at a speed of 0.3 ms −1 . From our 86,000 sliding motion tests of kinematic measurements, the sensor exhibits excellent stability, repeatability and strong signal durability.

Solid-liquid triboelectric nanogenerators (SL-TENGs) have shown promising prospects in energy harvesting and application from water resources. However, the low contact separation speed, small contact area, and long contacting time during solid-liquid electrification severely limit their output properties and further applications. Here, by leveraging the rheological properties of gas-liquid two-phase flow and the Venturi-like design, we circumvent these limitations and develop a previously unknown gas-liquid two-phase flow-based TENG (GL-TENG) that can achieve ultrahigh voltage and volumetric charge density of 3789 volts and 859 millicoulombs per cubic meter, respectively. With a high-power output of 143.6 kilowatts per cubic meter, a 24-watt commercial lamp can be directly lighted by a continuous-flow GL-TENG device. The high performance displayed SL-TENGs in this work provides a promising strategy for the practical application of solid-liquid TENGs in energy harvesting and sensing applications.

Piezoelectric generation is extended to the new domain of group-III nitrides. The output increases with increasing carrier density following the sequence: AlN, AlGaN, GaN and InN. The results indicate that, for a nanomaterial whose conductivity is below an optimum value, the output of its piezoelectric nanogenerator is dominated by the consumed voltage at the nanomaterial. Detailed facts of importance to specialist readers are published as "Supporting Information". Such documents are peer-reviewed, but not copy-edited or typeset. They are made available as submitted by the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Abstract Charge generation and charge decay are two essential factors that determine the surface charge density of a triboelectric nanogenerator (TENG). However, research mainly focuses on boosting charge generation, and little attention is paid to suppressing charge decay. Here, a strategy of suppressing charge decay, including the air breakdown and dielectric charge leakage, of TENG with high surface charge density (HCD‐TENG) is proposed by utilizing a dual dielectric layer. A series of parameters of different dielectric materials are tested with the assistance of a charge excitation TENG (CE‐TENG) to reveal the relationships between charge generation, air breakdown, and dielectric charge leakage in the atmospheric environment. Further, the phenomenon of dielectric charge leakage limiting the maximum output of TENG prior to air breakdown is observed for the first time. With the simultaneous suppression of the air breakdown and dielectric charge leakage, the output of TENG is enhanced to 2.2 mC m −2 . This work not only provides new insight into the performance optimization and material selection of TENG, but also provides significant guidance for obtaining high‐output TENG in the future.