Ping She

Enhanced photocurrent generation of bio-inspired graphene/ZnO composite films

A bio-inspired photoelectrode was developed by self-assembly of honeycomb graphene oxide films, followed by reduction and in situ growth of ZnO nanorods (NRs). In the nanocomposite film, the graphene substrate shows an elegant macroporous structure of an ordered honeycomb pattern, with uniformly and densely deposited ZnO NRs. In a photoelectric conversion system, the rGO/DODA/ZnO honeycomb film not only significantly improves light-capturing ability, but also provides a direct and stable pathway for rapid electron transport, promoting photoinduced electron–hole separation. Compared to the counterpart of a smooth hybrid film, the honeycomb composite material shows a decreased incident light reflection of 26%, and a three-fold increase in photocurrent. It is envisioned that this facile and scalable fabrication approach, as well as this bio-inspired structure, will open a new avenue for the rational design and engineering of high-performance solar energy conversion devices.

Macroscopic porous MnO2 aerogels for supercapacitor electrodes

A supercapacitor electrode has been fabricated from macroscopic porous MnO2 aerogels, and has demonstrated an enhanced specific capacitance, a high rate capability and excellent cycling durability. The improvement of supercapacitive performance can be attributed to the macro interconnected channels in the aerogel structure, which can not only facilitate mass transfer and reduce dead volume, but also provide an additional benefit of relieving stress.

Recent advances in the development of functionalized carbon nanotubes: a versatile vector for drug delivery

Carbon nanotubes (CNTs) possess unique physical and chemical properties and can serve as a platform for transporting a variety of bioactive molecules, such as drugs, proteins, and genes, given appropriate surface modifications. Here, we present an overview of the progress in applying CNTs as therapeutic agent carriers. Drugs can be attached to CNTs either through supramolecular chemistry to form noncovalent assembly or via covalent linkage to the functional groups preinstalled on CNTs. In addition to surface loading, packing of molecules inside the internal cavity of CNTs to protect less stable entities has also been achieved. Besides drugs, the high specific surface area of CNTs can also allow the installation of multiple molecules with different functions, e.g. target recognition and optical imaging, simultaneously to achieve synergistic effects. The drug release process tends to be gradual and sustained after being attached to CNTs, and could be tuned by various factors, such as pH, diameter of CNTs, and target recognition. The content throughout this review is mainly focused on the different protocols of loading drugs onto or into CNTs as well as how to control the drug release.

One-pot synthesis of Au@TiO2 yolk-shell nanoparticles with enhanced photocatalytic activity under visible light

Natural biological systems often use hollow structures to decrease reflection and achieve high solar light utilization. Herein, bio-inspired Au@TiO2 yolk-shell nanoparticles (NPs) have been designed to combine the advantages of noble metal coupling and hollow structures, and subsequently synthesized via a facile one-pot hydrothermal approach. The Au@TiO2 yolk-shell NPs not only exhibit reduced reflectance by multiple reflections and scattering within the hollow NPs, but also show enhanced photocatalytic activity in Rhodamine B (RhB) degradation by simultaneously improving light harvesting, charge separation and reaction site accessibility. Specifically, compared to the commercial TiO2 (P25), Au/TiO2 hybrid and Au@TiO2 core-shell NPs, the Au@TiO2 yolk-shell NPs demonstrate lower reflectance over a broader range and superior photocatalytic activity with more than 98.1% of RhB decomposed within 4h under visible light. The bio-inspired nanostructure, as well as the facile and scalable fabrication approach, will open a new avenue to the rational design and preparation of efficient photocatalysts for pollutant removal.

Controllable growth of Au@TiO2 yolk–shell nanoparticles and their geometry parameter effects on photocatalytic activity

Yolk–shell nanoparticles (NPs) have attracted significant interest due to their decreased reflection and high solar light utilization. Herein, we precisely and independently controlled the geometrical parameters of the cavity diameter, shell thickness, and Au core diameter in the Au@TiO2 yolk–shell NPs using the hydrothermal method. Furthermore, the photocatalytic activities of these samples were systematically evaluated by the photocatalytic degradation of Rhodamine B (RhB). Smaller cavity size, thinner TiO2 shell, and medium AuNP diameter were found to facilitate more efficient photocatalysis. Overall, Au@TiO2 yolk–shell NPs with a cavity diameter of 121 nm, Au core diameter of 50 nm, and shell thickness of 26 nm demonstrated highest photocatalytic activity. These results are important for understanding the effects of the geometrical parameters of Au@TiO2 yolk–shell NPs on the photocatalytic performance and for designing novel yolk–shell nanostructures.

Bioinspired self-standing macroporous Au/ZnO sponges for enhanced photocatalysis

A self-standing macroporous noble metal-zinc oxide (ZnO) sponge of robust 3D network has been fabricated through in-situ growth method. The key to the construction of the bioinspired sponge lies in the choice of commercial polyurethane sponge (CPS) with interconnected and junction-free macroporous structure as the skeleton to support Au/ZnO nanorods (Au/ZnONRs). The resultant Au/ZnO/CPS not only exhibits hierarchical structures representing physical features of CPS, but also demonstrates durable superior photocatalytic activity and hydrogen generation capability. In addition, we have adopted various irradiations to investigate the effect of UV light and visible light on the photocatalytic performance of Au/ZnO/CPS individually. In detail, the photocatalytic properties of Au/ZnO/CPS and ZnO/CPS have been monitored and compared under irradiations of different wavelengths (200-1100, 350-780, 200-420 and 420-780 nm) for 90 min to reveal the effect of irradiation wavelength on the activity of photocatalysts. A possible mechanism between irradiation wavelength and photocatalytic degradation efficiency is proposed. The facile in-situ growth approach presented herein can be easily scaled up, affording a convenient method for the preparation of self-standing 3D macroporous materials, which holds great potential for the application in both environmental purification and solar-to-hydrogen energy conversion.

ZnO nanodisks decorated with Au nanorods for enhanced photocurrent generation and photocatalytic activity

A facile approach for the preparation of Au nanorod/ZnO nanodisks (AuNR/ZnONDKs) through in situ nucleation and growth of ZnO in AuNR colloidal solution was developed. This is the first report of AuNRs modified on the ZnO surface. Furthermore, the aspect ratios of AuNRs in nanohybrids of AuNR/ZnONDKs were also tuned to achieve tunable and broad LSPR bands for an optimized photocatalytic performance. All of the resultant AuNR/ZnONDK nanohybrids with exposed AuNRs exhibit much higher photocatalytic activity and photocurrent generation compared to commercial ZnO (C-ZnO). In particular, AuNR-707/ZnONDKs express a swift and steady photocurrent of 0.33 mA cm−2, which is 16.5 times higher than the photocurrent generated by C-ZnO. The facile approach presented here opens up a new avenue for the rational design and preparation of high-performance photocatalysts for the future applications in both environmental purification and photoelectric conversion.

Spiky nanohybrids of TiO2/Au nanorods for enhanced hydrogen evolution and photocurrent generation

The fabrication of photocatalysts to achieve efficient utilization of renewable solar energy has attracted broad interest. Herein, a plasmonic spiky TiO2/Au nanorod (NR) nanohybrid was prepared by in situ nucleation and growth of spiky TiO2 in AuNR colloidal solution. The spiky TiO2/AuNR nanohybrids demonstrated enhanced hydrogen evolution activity and photocurrent generation under both visible light and simulated solar light irradiation as compared to bare spiky TiO2 nanoparticles and commercial TiO2. Specifically, the spiky nanohybrids displayed a high H2 production rate of 1.81 mmol g−1 h−1 under simulated solar light irradiation, which is 1.7 times higher than that of TiO2/Au nanosphere nanohybrids, and remain stable for three cycles. The improved photocatalytic H2 evolution demonstrated by the nanohybrids can be ascribed to the coupling effect of the AuNRs and the unique spiky structure. Furthermore, the charge transfer process during H2 evolution was investigated by photocurrent and electrochemical impendence spectroscopy (EIS) measurements. A fast and stable photocurrent was observed for the spiky TiO2/AuNR nanohybrid photoelectrode under both visible light and simulated solar light irradiation, while the EIS plots indicate a rapid charge transfer within the nanohybrids. Such a nanohybrid with a bio-inspired structure will afford new insights for the fabrication of novel photocatalysts.

A Photo-Curing Method to Prepare Biomimetic Micro-Nano Structure of Butterfly Wing Scale

It has been well-known that butterfly wings possess interesting optic properties. Recently, dendritic micro-nanostructure has been found in the wing scales of butterfly Trogonoptera brookiana, which shows excellent light-trapping effect, especially for the visible light. When light enters such a dendritic micro-nanostructure, it will be trapped and eventually absorbed by multiple reflections to generate heat. It is desirable to prepare a biomimetic structure resembling the micro-nanostructure of the butterfly wing scale, which may lead to a new material that can potentially improve the light utilization rate of solar thermal heater and other similar applications. However, a convenient method to make such a structure in large scale is still lacking. Herein, an easy and handy approach has been developed to prepare biomimetic dendritic structure. The starting material is negative photoresist, a chemical reagent which is widely used in photography. A simple device that can adjust the intensity and interval of ultraviolet illumination has been designed and set up. A periodic structure has been achieved via photo-curing with ultraviolet light and the ratio of illumination time has been optimized.