Xian-Xiang Zeng

Using graphene-based plasmonic nanocomposites to quench energy from quantum dots for signal-on photoelectrochemical aptasensing.

On the basis of the absorption and emission spectra overlap, an enhanced resonance energy transfer caused by excition-plasmon resonance between reduced graphene oxide (RGO)-Au nanoparticles (AuNPs) and CdTe quantum dots (QDs) was obtained. With the synergy of AuNPs and RGO as a planelike energy acceptor, it resulted in the enhancement of energy transfer between excited CdTe QDs and RGO-AuNPs nanocomposites. Upon the novel sandwichlike structure formed via DNA hybridization, the exciton produced in CdTe QDs was annihilated. A damped photocurrent was obtained, which was acted as the background signal for the development of a universal photoelectrochemical (PEC) platform. With the use of carcinoembryonic antigen (CEA) as a model which bonded to its specific aptamer and destroyed the sandwichlike structure, the energy transfer efficiency was lowered, leading to PEC response augment. Thus a signal-on PEC aptasensor was constructed. Under 470 nm irradiation at -0.05 V, the PEC aptasensor for CEA determination exhibited a linear range from 0.001 to 2.0 ng mL(-1) with a detection limit of 0.47 pg mL(-1) at a signal-to-noise ratio of 3 and was satisfactory for clinical sample detection. Since different aptamers can specifically bind to different target molecules, the designed strategy has an expansive application for the construction of versatile PEC platforms.

Wet Chemistry Synthesis of Multidimensional Nanocarbon–Sulfur Hybrid Materials with Ultrahigh Sulfur Loading for Lithium–Sulfur Batteries

An optimized nanocarbon-sulfur cathode material with ultrahigh sulfur loading of up to 90 wt % is realized in the form of sulfur nanolayer-coated three-dimensional (3D) conducting network. This 3D nanocarbon-sulfur network combines three different nanocarbons, as follows: zero-dimensional carbon nanoparticle, one-dimensional carbon nanotube, and two-dimensional graphene. This 3D nanocarbon-sulfur network is synthesized by using a method based on soluble chemistry of elemental sulfur and three types of nanocarbons in well-chosen solvents. The resultant sulfur-carbon material shows a high specific capacity of 1115 mA h g(-1) at 0.02C and good rate performance of 551 mA h g(-1) at 1C based on the mass of sulfur-carbon composite. Good battery performance can be attributed to the homogeneous compositing of sulfur with the 3D hierarchical hybrid nanocarbon networks at nanometer scale, which provides efficient multidimensional transport pathways for electrons and ions. Wet chemical method developed here provides an easy and cost-effective way to prepare sulfur-carbon cathode materials with high sulfur loading for application in high-energy Li-S batteries.

Photoelectrochemical Biosensor Using Enzyme-Catalyzed in Situ Propagation of CdS Quantum Dots on Graphene Oxide

An innovative photoelectrochemical (PEC) biosensor platform was designed based on the in situ generation of CdS quantum dots (QDs) on graphene oxide (GO) using an enzymatic reaction. Horseradish peroxidase catalyzed the reduction of sodium thiosulfate with hydrogen peroxide to generate H2S, which reacted with Cd(2+) to form CdS QDs. CdS QDs could be photoexcited to generate an elevated photocurrent as a readout signal. This strategy offered a green alternative to inconvenient presynthesis procedures for the fabrication of semiconducting nanoparticles. The nanomaterials and assembly procedures were characterized by microscopy and spectroscopy techniques. Combined with immune recognition and on the basis of the PEC activity of CdS QDs on GO, the strategy was successfully applied to a PEC assay to detect carcinoembryonic antigen and displayed a wide linear range from 2.5 ng mL(-1) to 50 μg mL(-1) and a detection limit of 0.72 ng mL(-1) at a signal-to-noise ratio of 3. The PEC biosensor showed satisfactory performance for clinical sample detection and was convenient for determining high concentrations of solute without dilution. This effort offers a new opportunity for the development of numerous rapid and convenient analytical techniques using the PEC method that may be applied in the design and preparation of various solar-energy-driven applications.

Quantum dots sensitized titanium dioxide decorated reduced graphene oxide for visible light excited photoelectrochemical biosensing at a low potential.

A low potential and competitive photoelectrochemical biosensing platform was developed using quantum dots sensitized titanium dioxide decorated reduced graphene oxide (TiO2-RGO) nanocomposites. The nanocomposites were prepared through electrostatic interaction between mercaptoacetic acid wrapped CdSe quantum dots with negative charge and TiO2-RGO hybrids with positive charge obtained via ultrasonic and acid treatments. Electron microscopes and spectroscopes were used to characterize the functionalized nanocomposites films of CdSe/TiO2-RGO, and the fabrication process of the photoelectrochemical biosensor. Based on the high photovoltaic conversion efficiency of CdSe/TiO2-RGO nanocomposites films, after introducing biological recognition and competitive immunoreaction, a low potential and competitive photoelectrochemical biosensor for carcinoembryonic antigen (CEA) detection was fabricated. The synergic effect of horseradish peroxide and benzo-4-chlorohexadienone decreased the background signal, leading to signal amplification. Under the light irradiation of 430 nm and the applied potential of 0 V, the biosensor detected CEA with a linear range from 0.003 to 100 ng mL(-1) and the detection limit was estimated to be 1.38 pg mL(-1) at a S/N of 3. It was satisfactory for clinical sample detection. The proposed competitive and low potential photoelectrochemical biosensor under irradiation of visible light exhibited good performance, which has a promising prospect in clinical diagnose.

A Flexible Solid Electrolyte Interphase Layer for Long-Life Lithium Metal Anodes

Lithium (Li) metal is a promising anode material for high-energy density batteries. However, the unstable and static solid electrolyte interphase (SEI) can be destroyed by the dynamic Li plating/stripping behavior on the Li anode surface, leading to side reactions and Li dendrites growth. Herein, we design a smart Li polyacrylic acid (LiPAA) SEI layer high elasticity to address the dynamic Li plating/stripping processes by self-adapting interface regulation, which is demonstrated by inu2005situ AFM. With the high binding ability and excellent stability of the LiPAA polymer, the smart SEI can significantly reduce the side reactions and improve battery safety markedly. Stable cycling of 700u2005h is achieved in the LiPAA-Li/LiPAA-Li symmetrical cell. The innovative strategy of self-adapting SEI design is broadly applicable, providing opportunities for use in Li metal anodes.

Mitigating Interfacial Potential Drop of Cathode–Solid Electrolyte via Ionic Conductor Layer To Enhance Interface Dynamics for Solid Batteries

The rapid capacity decay caused by the poor contact and large polarization at the interface between the cathode and solid electrolytes is still a big challenge to overcome for high-power-density solid batteries. In this study, a superior Li+ conductive transition layer Li1.4Al0.4Ti1.6(PO4)3 is introduced to coat LiNi0.6Co0.2Mn0.2O2, as a model cathode, to mitigate polarization and enhance dynamic characteristics. The critical attribute for such superior dynamics is investigated by the atomic force microscopy with boundary potential analysis, revealing that the formed interfacial transition layer provides a gradual potential slope and sustain-released polarization, and endows the battery with improved cycling stability (90% after 100 cycles) and excellent rate capability (116 mA h g-1 at 2 C) at room temperature, which enlightens the comprehension of interface engineering in the future solid batteries systems.

Improving the stability of LiNi 0.80 Co 0.15 Al 0.05 O 2 by AlPO 4 nanocoating for lithium-ion batteries

Nickel-rich layered materials, such as LiNi0.80Co0.15Al0.05O2 (NCA), have been considered as one alternative cathode materials for lithium-ion batteries (LIBs) due to their high capacity and low cost. However, their poor cycle life and low thermal stability, caused by the electrode/electrolyte side reaction, prohibit their prosperity in practical application. Herein, AlPO4 has been homogeneously coated on the surface of NCA via wet chemical method towards the target of protecting NCA from the attack of electrolyte. Compared with the bare NCA, NCA@AlPO4 electrode delivers high capacity without sacrificing the discharge capacity and excellent cycling stability. After 150 cycles at 0.5 C between 3.0–4.3 V, the capacity retention of the coated material is 86.9%, much higher than that of bare NCA (66.8%). Furthermore, the thermal stability of cathode is much improved due to the protection of the uniform coating layer on the surface of NCA. These results suggest that AlPO4 coated NCA materials could act as one promising candidate for next-generation LIBs with high energy density in the near future.

Heteroatom-doped electrodes for all-vanadium redox flow batteries with ultralong lifespan

The phosphorus and fluorine codoped graphite felt electrodes with prominent hydrophilicity present excellent electroactivity towards V2+/V3+ and VO2+/VO2+, elevate the discharging ability up to 250 mA cm−2 and dramatically extend the energy efficiency of vanadium redox flow batteries towards 1000 cycles with 0.003% reduction per cycle.

High electro-catalytic graphite felt/MnO 2 composite electrodes for vanadium redox flow batteries

A mild and simple synthesis process for large-scale vanadium redox flow batteries (VRFBs) energy storage systems is desirable. A graphite felt/MnO2 (GF-MNO) composite electrode with excellent electrocatalytic activity towards VO2+/VO2+ redox couples in a VRFB was synthesized by a one-step hydrothermal process. The resulting GF-MNO electrodes possess improved electrochemical kinetic reversibility of the vanadium redox reactions compared to pristine GF electrodes, and the corresponding energy efficiency and discharge capacity at 150 mA cm−2 are increased by 12.5% and 40%, respectively. The discharge capacity is maintained at 4.8 A h L−1 at the ultrahigh current density of 250 mA cm−2. Above all, 80% of the energy efficiency of the GFMNO composite electrodes is retained after 120 charge-discharge cycles at 150 mA cm−2. Furthermore, these electrodes demonstrated that more evenly distributed catalytic active sites were obtained from the MnO2 particles under acidic conditions. The proposed synthetic route is facile, and the raw materials are low cost and environmentally friendly. Therefore, these novel GFMNO electrodes hold great promise in large-scale vanadium redox flow battery energy storage systems.

Recent Advancements in Polymer-Based Composite Electrolytes for Rechargeable Lithium Batteries

In recent years, lithium batteries using conventional organic liquid electrolytes have been found to possess a series of safety concerns. Because of this, solid polymer electrolytes, benefiting from shape versatility, flexibility, low-weight and low processing costs, are being investigated as promising candidates to replace currently available organic liquid electrolytes in lithium batteries. However, the inferior ion diffusion and poor mechanical performance of these promising solid polymer electrolytes remain a challenge. To resolve these challenges and improve overall comprehensive performance, polymers are being coordinated with other components, including liquid electrolytes, polymers and inorganic fillers, to form polymer-based composite electrolytes. In this review, recent advancements in polymer-based composite electrolytes including polymer/liquid hybrid electrolytes, polymer/polymer coordinating electrolytes and polymer/inorganic composite electrolytes are reviewed; exploring the benefits, synergistic mechanisms, design methods, and developments and outlooks for each individual composite strategy. This review will also provide discussions aimed toward presenting perspectives for the strategic design of polymer-based composite electrolytes as well as building a foundation for the future research and development of high-performance solid polymer electrolytes.Graphical Abstract