Jinjin Li

Three-dimensional graphene-based nanocomposites for high energy density Li-ion batteries

High energy density Li-ion batteries have attracted broad attention due to their great significance for various applications ranging from portable electronics to electric vehicles. However, emerging applications require batteries with greater than currently available energy densities, which have motivated numerous research efforts such as investigations on high energy density active materials, and engineered electrode structures that maximize the capacity. Three-dimensional (3D) graphene provides promising pathways for developing high energy density electrodes including cathodes and anodes, because of its potential for providing a conductive 3D network, improving Li+ ion and electron transfer, as well as accommodating the structure and volume change during cycling. In this review, recent research efforts particularly focused on 3D graphene-based nanocomposite electrodes which exhibit high energy density, high capacity, and good rate performance have been summarized comprehensively. The current challenges for high energy density Li-ion batteries have been discussed, while the potential research perspectives have been presented as well, which we hope would inspire high-performance battery investigations.

Surface-Electronic-State-Modulated, Single-Crystalline (001) TiO2 Nanosheets for Sensitive Electrochemical Sensing of Heavy-Metal Ions

Intrinsically low conductivity and poor reactivity restrict many semiconductors from electrochemical detection. Usually, metal- and carbon-based modifications of semiconductors are necessary, making them complex, expensive, and unstable. Here, for the first time, we present a surface-electronic-state-modulation-based concept applied to semiconductors. This concept enables pure semiconductors to be directly available for ultrasensitive electrochemical detection of heavy-metal ions without any modifications. As an example, a defective single-crystalline (001) TiO2 nanosheet exhibits high electrochemical performance toward Hg(II), including a sensitivity of 270.83 μA μM-1 cm-2 and a detection limit of 0.017 μM, which is lower than the safety standard (0.03 μM) of drinking water established by the World Health Organization (WHO). It has been confirmed that the surface oxygen vacancy adsorbs an O2 molecule while the Ti3+ donates an electron, forming the O2•- species that facilitate adsorption of Hg(II) and serve as active sites for electron transfer. These findings not only extend the electrochemical sensing applications of pure semiconductors but also stimulate new opportunities for investigating atom-level electrochemical behaviors of semiconductors by surface electronic-state modulation.

Snowflake-Shaped ZnO Nanostructures-Based Gas Sensor for Sensitive Detection of Volatile Organic Compounds

Volatile organic compounds (VOCs) have been considered severe risks to human health. Gas sensors for the sensitive detection of VOCs are highly required. However, the preparation of gas-sensing materials with a high gas diffusion performance remains a great challenge. Here, through a simple hydrothermal method accompanied with a subsequent thermal treatment, a special porous snowflake-shaped ZnO nanostructure was presented for sensitive detection of VOCs including diethyl ether, methylbenzene, and ethanol. The fabricated gas sensors exhibit a good sensing performance including high responses to VOCs and a short response/recovery time. The responses of the ZnO-based gas sensor to 100 ppm ethanol, methylbenzene, and diethyl ether are about 27, 21, and 11, respectively, while the response times to diethyl ether and methylbenzene are less than 10 seconds. The gas adsorption-desorption kinetics is also investigated, which shows that the gas-sensing behaviors to different target gases are remarkably different, making it possible for target recognition in practical applications.

In situ gold nanoparticle-decorated three-dimensional tin dioxide nanostructures for sensitive and selective gas-sensing detection of volatile organic compounds

Sensitive and selective gas sensors for the detection of volatile organic compounds are highly desired. A composite consisting of a specific structure modified with a noble metal catalyst is considered as a promising sensing material candidate. Herein, we present a three-dimensional tin dioxide (SnO2) nanostructure in situ-decorated with gold nanoparticles (AuNPs) on the surface; this nanostructure exhibited high gas-sensing performance including high response and selectivity towards volatile organic compounds. To achieve high-loading of AuNPs, 3-aminopropyltrimethoxysilane (APTMS) functionalization was conducted on the surface of SnO2/carbonaceous precursors prior to the AuNPs growth. The vapors of volatile organic compounds, such as acetone, methanol, and hexane, were employed as analytes for gas-sensing measurements. The results show that the SnO2 nanostructures decorated with dense AuNPs exhibit remarkably better gas-sensing performance as compared to SnO2 with few AuNPs and pure SnO2. In addition, gas sensors based on three-dimensional AuNP-decorated-SnO2 showed high recognition ability towards different analytes in combination with a principal component analysis method, indicating their promising practical application for gas environment monitoring.

Optomechanical Transistor With Phonons and Photons

A better behaved and easily controlled optical communication device could improve the performance of signal transmission. Here, we present an optomechanical transistor within cavity-optomechanical system, where the coupled phonons–photons interfere with the input signal photons while the pump field controls the transmission spectrum of the signal laser. We demonstrate the existence of transmitted signal attenuation and amplification through the optomechanical transistor when switching OFF and ON the pump field, respectively. By increasing the input pump power, the output signal gain can be further enhanced abruptly. The proposed optomechanical transistor that has the advantages of simple manufacture technology, low cost, convenient replacement, normal working environment, and so on could be implemented in current experiments and pave the way for all-optical logic circuits and quantum repeaters.

Controlling signal transport in a carbon nanotube opto-transistor

With the highly competitive development of communication technologies, modern information manufactures place high importance on the ability to control the transmitted signal using easy miniaturization materials. A controlled and miniaturized optical information device is, therefore, vital for researchers in information and communication fields. Here we propose a controlled signal transport in a doubly clamped carbon nanotube system, where the transmitted signal can be controlled by another pump beam. Pump off results in the transmitted signal off, while pump on results in the transmitted signal on. The more pump, the more amplified output signal transmission. Analogous with traditional cavity optomechanical system, the role of optical cavity is played by a localized exciton in carbon nanotube while the role of the mechanical element is played by the nanotube vibrations, which enables the realization of an opto-transistor based on carbon nanotube. Since the signal amplification and attenuation have been observed in traditional optomechanical system, and the nanotube optomechanical system has been realized in laboratory, the proposed carbon nanotube opto-transistor could be implemented in current experiments and open the door to potential applications in modern optical networks and future quantum networks.