Zhiqiang Su

Recent advances in the synthesis and applications of graphene–polymer nanocomposites

Graphene (G)-based nanocomposites have received much attention in various disciplines due to their high specific surface area, good compatibility, low mass density, elegant flexibility as well as the excellent synergistic effect of G with other nanomaterials. Numerous studies have been carried out to fabricate G-based polymer composites with novel and improved properties. However, the dispersion behavior of G in a polymer matrix and the interfacial bonding between G and polymers still restrict the better performances and broader applications of the fabricated G–polymer nanocomposites. In this review, we have summarized the most recent studies on the modification of G with polymers and the subsequent synthesis and applications of high quality G–polymer nanocomposites. The strategies for surface modification of G with polymers, including various covalent and non-covalent techniques, are introduced in detail. In addition, a series of effective processing routes for producing high quality G–polymer nanocomposites, such as melt compounding, solution blending, in situ polymerization, latex mixing, and electropolymerization, are introduced and discussed. Finally, the potential applications of the synthesized G–polymer nanocomposites in electrocatalysts, drug delivery, high performance materials, biosensors, and biomedical materials are presented.

Electrospinning graphene quantum dots into a nanofibrous membrane for dual-purpose fluorescent and electrochemical biosensors

Graphene quantum dots (GQDs) have become increasingly important for applications in energy materials, optical devices and biosensors. Here we report a facile technique to fabricate a nanofibrous membrane of GQDs by electrospinning water-soluble GQDs with polyvinyl alcohol (PVA) directly. The structure and fluorescence properties of the fabricated PVA/GQD nanofibrous membrane were investigated using scanning and transmission electron microscopy, and fluorescence microscopy. It was found that the electrospun PVA/GQD nanofibrous membrane has a three-dimensional structure with a high surface area to volume ratio, which is beneficial for the adsorption of electrolytes and the diffusion of reactants. For the first time, the created PVA/GQD nanofibrous membrane was utilized to fabricate dual-purpose fluorescent and electrochemical biosensors for highly sensitive determination of hydrogen peroxide (H2O2) and glucose. The experimental results indicated that the fluorescence intensity of the nanofibrous membrane decreased linearly with increasing H2O2 concentration, because the addition of H2O2 leads to fluorescence quenching of the GQDs, which endows the fabricated nanofibrous membrane with fluorescence activity. Besides, after binding glucose oxidase onto the created nanofibrous membrane, the fabricated nanofibrous membrane showed high sensitivity and selectivity for glucose detection. In addition, the PVA/GQD nanofibrous membrane can also be directly electrospun onto an electrode for electrochemical detection of H2O2. This novel nanofibrous membrane exhibits excellent catalytic performance and fluorescence activity, and therefore has potential applications for the highly stable, sensitive, and selective detection of H2O2 and glucose.

One-Step Synthesis of Large-Scale Graphene Film Doped with Gold Nanoparticles at Liquid–Air Interface for Electrochemistry and Raman Detection Applications

We demonstrated a facile one-step synthesis strategy for the preparation of a large-scale reduced graphene oxide multilayered film doped with gold nanoparticles (RGO/AuNP film) and applied this film as functional nanomaterials for electrochemistry and Raman detection applications. The related applications of the fabricated RGO/AuNP film in electrochemical nonenzymatic H2O2 biosensor, electrochemical oxygen reduction reaction (ORR), and surface-enhanced Raman scattering (SERS) detection were investigated. Electrochemical data indicate that the H2O2 biosensor fabricated by RGO/AuNP film shows a wide linear range, low limitation of detection, high selectivity, and long-term stability. In addition, it was proved that the created RGO/AuNP film also exhibits excellent ORR electrochemical catalysis performance. The created RGO/AuNP film, when serving as SERS biodetection platform, presents outstanding performances in detecting 4-aminothiophenol with an enhancement factor of approximately 5.6 × 10(5) as well as 2-thiouracil sensing with a low concentration to 1 μM. It is expected that this facile strategy for fabricating large-scale graphene film doped with metallic nanoparticles will spark inspirations in preparing functional nanomaterials and further extend their applications in drug delivery, wastewater purification, and bioenergy.

Fabrication technologies and sensing applications of graphene-based composite films: Advances and challenges.

Graphene (G)-based composite materials have been widely explored for the sensing applications ascribing to their atom-thick two-dimensional conjugated structures, high conductivity, large specific surface areas and controlled modification. With the enormous advantages of film structure, G-based composite films (GCFs), prepared by combining G with different functional nanomaterials (noble metals, metal compounds, carbon materials, polymer materials, etc.), show unique optical, mechanical, electrical, chemical, and catalytic properties. Therefore, great quantities of sensors with high sensitivity, selectivity, and stability have been created in recent years. In this review, we focus on the recent advances in the fabrication technologies of GCFs and their specific sensing applications. In addition, the relationship between the properties of GCFs and sensing performance is concentrated on. Finally, the personal perspectives and key challenges of GCFs are mentioned in the hope to shed a light on their potential future research directions.

Hydrothermal synthesis of zinc oxide-reduced graphene oxide nanocomposites for an electrochemical hydrazine sensor

We report here a facile synthesis of different zinc oxide (ZnO) nanostructures on reduced graphene oxide (RGO) by an in situ hydrothermal reaction. ZnO nanostructures with different morphologies on the surface of RGO were successfully synthesized by adjusting the mass ratio of Zn2+ to RGO in this reaction system. It was found that ZnO nanostructures with nanoparticles, mixed nanoparticles and microspindles, and microspindles were formed on RGO by adjusting the mass ratio of Zn2+ to RGO. The synthesized ZnO–RGO nanocomposites with different structures were immobilized onto glassy carbon electrodes and applied to construct electrochemical hydrazine (N2H4) sensors. The results indicate that the ZnO–RGO nanocomposites created with the mass ratio of 4.4 : 1 present the best sensor performance. The fabricated N2H4 sensor exhibited a fast amperometric response to N2H4 with a linear detection range from 1.0 μM to 33.5 mM and a detection limit of 0.8 μM. The superior performance is ascribed to the unique structure of the synthesized ZnO and the excellent conductivity of RGO. In addition, we found that the synthesized ZnO–RGO composites exhibited improved electrochemical stability. Such novel ZnO–RGO hybrid materials represent promising nonenzymatic electrochemical N2H4 sensors with high sensitivity and selectivity, improved stability, and fast amperometric response.

Fabrication, characterization and sensor application of electrospun polyurethane nanofibers filled with carbon nanotubes and silver nanoparticles

We reported here the electrospinning preparation of polyurethane nanofibers filled with carbon nanotubes and silver nanoparticles (PU-MWCNT-AgNP) and the subsequent fabrication of a novel non-enzymatic amperometric biosensor for analytical determination of hydrogen peroxide. The morphologies of the as-spun PU-MWCNT-AgNP hybrid nanofibers were observed by scanning and transmission electron microscopy. The interaction between MWCNTs and AgNPs in the electrospun nanofibers was studied by differential scanning calorimetry and dynamic mechanical analysis. The cyclic voltammetry experiments indicate that PU-MWCNT-AgNP nanofiber modified electrodes have high electrocatalytic activity on hydrogen peroxide, and the chronoamperometry measurements illustrate that this electrospun sensor has high sensitivity for detecting hydrogen peroxide. Our study further confirms the remarkable synergistic effect of MWCNTs and AgNPs on the significant improvement of the conductivity of electrospun nanofibers and the electrocatalytic activity, as well as the sensitivity of the fabricated non-enzymatic sensor. Under an optimal experimental condition, the created biosensor for detecting hydrogen peroxide has a sensitivity of 160.6 μA mM-1 cm-2, a wide linear range from 0.5 to 30 mM and a detection limit of 18.6 μM (S/N = 3), which indicates that this novel and simple strategy for fabricating electrochemical sensor by an electrospinning technique has wide potential applications in bio-analysis and detection.

Electrospun doping of carbon nanotubes and platinum nanoparticles into the β-phase polyvinylidene difluoride nanofibrous membrane for biosensor and catalysis applications.

A novel β-phase polyvinylidene difluoride (PVDF) nanofibrous membrane decorated with multiwalled carbon nanotubes (MWCNTs) and platinum nanoparticles (PtNPs) was fabricated by an improved electrospinning technique. The morphology of the fabricated PVDF-MWCNT-PtNP nanofibrous membrane was observed by scanning electron microscopy, and the formation of high β-phase in the hybrid nanofibrous membrane was investigated by Fourier transform infrared spectroscopy and differential scanning calorimetry. The uniform dispersion of MWCNTs and PtNPs in the PVDF hybrid nanofibrous membrane and their interaction were explored by transmission electron microscopy and X-ray diffraction. For the first time, we utilized this created PVDF-MWCNT-PtNP nanofibrous membrane for biosensor and catalysis applications. The nonenzymatic amperometric biosensor with highly stable and sensitive, and selective detection of both H2O2 and glucose was successfully fabricated based on the electrospun PVDF-MWCNT-PtNP nanofibrous membrane. In addition, the catalysis of the hybrid nanofibrous membrane for oxygen reduction reaction was tested, and a good catalysis performance was found. We anticipate that the strategies utilized in this work will not only guide the further design of functional nanofiber-based biomaterials and biodevices but also extend the potential applications in energy storage, cytology, and tissue engineering.

Electrospinning: a facile technique for fabricating polymeric nanofibers doped with carbon nanotubes and metallic nanoparticles for sensor applications

The increased interest in electrospinning (ES) and its recent applications for fabrication of sensors and biosensors is driven by the development of materials science and nanotechnology. Compared with other fabrication processes, ES is versatile and superior for producing and constructing ordered and complex nanofibrous materials. The introduction of carbon nanotubes (CNTs) and metallic nanoparticles (MNPs) into the electrospun polymeric nanofibers (NFs) extends their potential applications as electrical and electrochemical sensors and biosensors. In this review, we summarize the recent progress using the ES technique to fabricate different polymeric NFs doped with CNTs and various MNPs, as well as their applications for detecting alcohols, H2S, H2, glucose, H2O2, and urea. The fabrication, intrinsic fundamentals, and optimization design of the sensors were introduced and discussed in detail. In addition, the improvements and challenges of ES techniques were mentioned. It is expected that this review will promote development in the ES field and guide studies to create nanofibrous hybrid materials as novel sensors and biosensors.

Cuprous oxide microspheres on graphene nanosheets: an enhanced material for non-enzymatic electrochemical detection of H2O2 and glucose

We report here a facile one-step green synthesis of cuprous oxide microspheres (Cu2OMS) on reduced graphene oxide (RGO) by reducing Cu2+ ions and GO with sodium ascorbate synchronously in the presence of sodium hydroxide. Cu2OMS with different sizes on the surface of RGO were successfully synthesized by adjusting the mass ratio of GO to CuSO4·5H2O in this reaction system. It was found that uniform Cu2OMS were formed on RGO by increasing the mass ratio from 1 : 20 to 1 : 80. The synthesized Cu2OMS–RGO composites with different structures were immobilized onto glassy carbon electrodes and applied to construct electrochemical hydrogen peroxide (H2O2) and glucose sensors. The results indicate that the Cu2OMS–RGO composite created with the mass ratio of 1 : 80 presents the best sensor performances. The fabricated H2O2 sensor exhibits a fast amperometric response to H2O2 with a linear detection range from 0.005 to 2.775 mM and a detection limit of 0.0108 mM, and the glucose sensor has a linear detection range from 0.001 to 0.419 mM and a detection limit of 7.288 × 10−4 mM. The superior performance is ascribed to the unique structure of the synthesized Cu2OMS and the excellent conductivity of the RGO content. In addition, the synthesized Cu2OMS–RGO composites exhibited improved electrochemical stability. Such novel Cu2OMS–RGO hybrid materials represent promising non-enzymatic electrochemical glucose and H2O2 sensors with high sensitivity and selectivity, improved stability, and fast amperometric response.

MoS2 nanosheets decorated with gold nanoparticles for rechargeable Li–O2 batteries

We demonstrate here a facile one-step hydrothermal synthesis to prepare molybdenum disulfide nanosheets decorated with gold nanoparticles (MoS2/AuNPs) for rechargeable Li–O2 batteries. The fabricated Li–O2 battery exhibits enhanced specific capacity and cycle efficiency, which are ascribed to the two-dimensional structure of MoS2/AuNP nanohybrids and the synergistic catalytic effects of both MoS2 nanosheets and AuNPs.