Liangjing Shi

Synthesis of nitrogen-doped reduced graphene oxide directly from nitrogen-doped graphene oxide as a high-performance lithium ion battery anode

A new route has been developed to synthesize nitrogen-doped reduced graphene oxide (N-RGO) with excellent lithium storage properties. Nitrogen-doped graphene oxide (N-GO) is firstly synthesized and then reduced to N-RGO. The nitrogen content of N-GO can reach up to 5.6 wt%. After hydrothermal treatment, the nitrogen content of N-RGO still remains at 2.0 wt%. Our N-RGO material reveals excellent reversible capacity of 600 mA h g−1 at a current density of 0.1 C (1 C = 372 mA g−1) after 60 cycles, superior to that of pristine-RGO (350 mA h g−1 at a current density of 0.1 C). Our work opens up a new way to synthesize N-RGO, which is a promising candidate for lithium ion battery (LIB) anodes. In addition, the intermediate N-GO, with high activity, can combine with other materials for convenient application. In this work the Fe2O3/N-RGO composite is also prepared to show the outstanding properties of N-RGO.

Plasma-induced nanowelding of a copper nanowire network and its application in transparent electrodes and stretchable conductors

Copper nanowires (Cu NWs) have attracted increasing attention as building blocks for electronics due to their outstanding electrical properties and low cost. However, organic residues and oxide layers ubiquitously existing on the surface of Cu NWs impede good inter-wire contact. Commonly used methods such as thermal annealing and acid treatment often lead to nanowire damage. Herein, hydrogen plasma treatment at room temperature has been demonstrated to be effective for simultaneous surface cleaning and selective welding of Cu NWs at junctions. Transparent electrodes with excellent optical-electrical performance (19 O·sq–1 @ 90% T) and enhanced stability have been fabricated and integrated into organic solar cells. Besides, Cu NW conductors with superior stretchability and cycling stability under stretching speeds of up to 400 mm·min–1 can also be produced by the nanowelding process, and the feasibility of their application in stretchable LED circuits has been demonstrated.

Synthesis of Metal/Bimetal Nanowires and Their Applications as Flexible Transparent Electrodes

As a potential alternative to indium oxide (ITO), metal nanowire transparent conductive electrodes (TCEs) have attracted more and more attention. Here, a facile method that can be applied to the synthesis of a variety of metal/bimetallic nanowires has been proposed. Metal/bimetallic nanowires synthesized through this method show high aspect ratios and great dispersibility, which makes them ideal building blocks for transparent electrodes. The synthesis mechanism is discussed in-depth to give a theoretical basis of morphology control of metal nanostructures in organic synthesizing systems. TCEs with high flexibility, excellent optical-electrical performance as well as outstanding anti-thermal and anti-moisture stability are constructed. To the best of our knowledge, this is the first work on synthesizing multiple metal/bimetallic nanowires through one method.

Transparent heaters based on highly stable Cu nanowire films

In spite of the recent successful demonstrations of flexible and transparent film heaters, most heaters with high optical transmittance and low applied direct current (DC) voltage are silver nanowire (Ag NW)-based or silver grid-based. In this study, flexible and stretchable copper nanowire (Cu NW)-based transparent film heaters were fabricated through a solution-based process, in which a thin layer of hydrophobic polymers was encapsulated on the Cu NW films. The thin polymer layer protected the films from oxidation under harsh testing conditions, i.e., high temperature, high humidity, and acidic and alkaline environments. The films exhibited remarkable performance, a wide operating temperature range (up to 150 °C), and a high heating rate (14 °C/s). Defrosting and wearable thermotherapy demonstrations of the Cu NW film heaters were carried out to investigate their practicality. The Cu NW-based film heaters have potential as reliable and low-cost film heaters.

Effect of storage temperature on spore viability and early gametophyte development of three vulnerable species of Alsophila (Cyatheaceae)

To effectively preserve the vulnerable species of Alsophila, we studied the effects of varying the temperature and duration of storage on spore viability, early gametophyte development and the microstructure of brown spores of three Alsophila species. Spores of A. spinulosa (Wall. ex Hook.) Tryon and A. gigantea Wall. ex Hook. lost viability quickly when stored at room temperature and suffered from great loss when stored at –18°C from 6 to 12 months. Within 1 month, spore viability of A. spinulosa and A. gigantea stored at 4°C was higher than that of those stored in liquid nitrogen. In contrast, long-term storage in liquid nitrogen resulted in a comparatively small loss of viability for these two species. The spores of A. podophylla Hook. died within 3 months after storage at room temperature, 4°C and –18°C, and they died within 12 months when stored in liquid nitrogen. The spores of A. spinulosa and A. gigantea stored at room temperature, 4°C and –18°C, were prone to develop into abnormal gametophytes. These results suggest that storage of A. spinulosa and A. gigantea spores in liquid nitrogen is an effective method of preserving these vulnerable species. The reasons for the failure to preserve ephemeral A. podophylla spores by storage in liquid nitrogen are discussed.

Novel fabrication of copper nanowire/cuprous oxidebased semiconductor-liquid junction solar cells

A Cu nanowire (NW)/cuprous oxide (Cu2O)-based semiconductor-liquid junction solar cell with a greatly enhanced efficiency and reduced cost was assembled. The Cu NWs function as a transparent electrode as well as part of the Cu NWs/ Cu2O coaxial structures, which remarkably benefit the charge separation. The best solar cell reached a conversion efficiency as high as 1.92% under a simulated AM1.5G illumination, which is 106 times higher than that of cells based on fluorine-doped tin oxide and Cu2O.

Reactant-governing growth direction of indium nitride nanowires

Hexagonal wurtzite InN nanowires are grown via a vapor-liquid-solid (VLS) mechanism with an Au catalyst. Microstructure characterizations of a large number of nanowires demonstrate that the growth direction of InN nanowires is governed by variable NH(3) flux. InN nanowires at a NH(3) flux of 10 standard cubic centimeters per minute (sccm) grow preferentially in a hexagonal close-packed (hcp) <1010> direction, while those at 100 sccm NH(3) flux favor the hcp <0001> direction. A free energy minimization model is proposed to interpret this phenomenon. The first-principles calculations reveal that the <1010> oriented nucleus has the lowest energy at the lower NH(3) flux. In contrast, when NH(3) flux is high, the <0001> oriented nucleus has the lowest energy.

High-Performance Piezoresistive Electronic Skin with Bionic Hierarchical Microstructure and Microcracks

Electronic skin (E-skin), a popular research topic at present, has achieved significant progress in a variety of sophisticated applications. However, the poor sensitivity and stability severely limit the development of its application. Here, we present a facile, cost-effective, and scalable method for manufacturing E-skin devices with bionic hierarchical microstructure and microcracks. Our devices exhibit high sensitivity (10 kPa-1) and excellent durability (10 000 cycles). The synergistic enhancement mechanism of the hierarchical microstructure and the microcracks on the conductive layers was discovered. Moreover, we carried out a series of studies on the airflow detection and the noncontact speech recognition.

A symmetrical bi-electrode electrochemical technique for high-efficiency transfer of CVD-grown graphene.

Graphene transfer is a critical process in the journey from CVD-grown graphene to device application. The current transfer techniques use a chemical-etching method to oxidize the metal catalyst, which is heavily time-consuming and involves a high material cost. In this study, a highly efficient symmetrical bi-electrode technique has been developed to simultaneously delaminate the CVD-grown graphene from the metal catalyst at both the anode and cathode of the electrolytic cell. Raman spectra, UV-visible transmittance, and four-probe measurements confirm that this transfer process is nondestructive and can produce similar electrical properties to those produced by the conventional metal-etching transfer method. This bi-electrode transfer technique possesses the advantages of high efficiency, recyclable use of metal catalyst, and high electrical conductivity, and it can be potentially applied for industrial applications.

Kinetically Controlled Synthesis of Cu Nanowires with Tunable Diameters and Their Applications in Transparent Electrodes

One-dimensional metallic nanostructures have attracted ever increasing attention in recent years due to their potential applications in transparent electrodes, catalysts, surface enhanced resonance scattering (SERS) based sensors and electric heating elements. The controllable synthesis of high quality metal nanowires is of great importance for the optimization of devices based on metal nanowires. However, due to the intrinsic complexity of one-pot organic reaction systems, the reaction mechanism is still yet to be understood, which severely holds back the efforts towards the controllable synthesis of high quality nanowires. Herein, a two-step method for the synthesis of high-quality Cu nanowires with tunable diameters is proposed. The mechanism of a typical synthesis procedure is discussed through analyzing the apparent phenomena and intermediate products. Kinetically controlled synthesis is achieved by adjusting the species and concentration of halide ions to synthesize high-purity Cu nanowires with tunable diameters ranging from 20 to 90 nm. Electrodes with superior conductivity (FoM ∼ 140, 11 Ω sq−1@80%) are constructed and characterized on the basis of the Cu nanowires synthesized through this method. Red shifts in the LSPR peaks of Cu nanowire dispersions and increments in the haze factors of nanowire electrodes are observed as the average diameter of Cu nanowires increases. The method is also successfully expanded to the synthesis of Ag nanowires with tunable diameters.