Juncheng Liu

Influence of MWCNTs Doping on the Structure and Properties of PEDOT:PSS Films

Poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) doped with multi-walled carbon nanotubes (MWCNTs) films is fabricated on quartz substrates by spin coating method. The effects of MWCNTs on the structure and properties of PEDOT:PSS film have been investigated. X-ray diffractometer (XRD) and Fourier transform Raman spectroscopy (FTRM) show that the crystallization behavior and the main chain of PEDOT:PSS are not changed. Atomic force microscopy (AFM) shows that individual nanotubes are well dispersed in the PEDOT:PSS matrix. Moreover, some nanotubes overlap into a net-like structure, forming new conductive channels, which can enhance efficiently the film conductivity. The conductivity of PEDOT:PSS film doped with a lower percentage of MWCNTs (0.2 wt%) is 9.16 S/cm, higher than that of pure PEDOT:PSS film (0.28 S/cm), although the optical transmission of PEDOT:PSS decreases a little after the addition of MWCNTs. The interaction between MWCNTs and PEDOT:PSS during melt mixing is also given a possible explanation.

Effect of annealing temperature on the structure and properties of vanadium oxide films

Vanadium oxide is a promising material due to its thermochromic characteristics and is currently being evaluated for use in various thermal and optical applications. VO2 films were prepared on quartz substrates using the sol-gel method, spin coating, and annealing. To obtain VO2 films with high purity and improve their thermochromic properties, the effect of the annealing temperature on the film’s structure and properties was investigated. As the annealing temperature increased from 450 °C to 650 °C, the film’s phase component went through an amorphous phase, a VO2 phase with initial crystallization, a VO2 phase with high purity and mature crystallization, a VO2 phase with a small amount of a V2O5 phase, and a VO2 phase with a greater amount of a V2O5 phase. The film’s crystallinity improved continuously, and the film annealed at 550 °C was composed of fine, compact particles; higher temperatures resulted in coarser grains. The maximum transmittance mutation of the film to infrared radiation first increased and then decreased. The film annealed at 550 °C attained the maximum value of 67% at a wavelength of 2500 nm, and its phase transition temperature was 67.6 °C.

A timesaving, low-cost, high-yield method for the synthesis of ultrasmall uniform graphene oxide nanosheets and their application in surfactants.

Graphene oxide nanosheets (GONSs) with a lateral size less than 100 nm have attracted more and more attention for their wide range of potential applications, from bionanotechnology and nanobiomedicine to surfactants. However, at present GONSs are commonly prepared from graphite nanofibers or graphite nanopowders which are both expensive. Here, a timesaving, low-cost, high-yield method is proposed for preparing ultrasmall uniform GONSs with an average lateral size of ∼30 nm, utilizing common graphite powder as the raw material in the absence of a strong acid. The obtained GONSs are able to disperse single-walled carbon nanotubes (SWCNTs) effectively, and the dispersion could withstand high-speed centrifugation. Consequently, GONSs could indeed serve as a superior surfactant for the dispersion of SWCNTs, and the dispersion could be further applied in electronics, as the GONSs may be further reduced to reduced GONSs or graphene nanosheets.

Preparation, characterization, and chemical-induced hydrophobicity of thermostable amine-modified graphene oxide

In this study, a hydrophobic and thermostable amine-modified graphene oxide (MGO) material was fabricated using two different methods. p-Toluidine was covalently introduced onto the surface of graphene oxide (GO) sheets using direct and indirect amidation processes to obtain the amine-modified GO (MGO-1 and MGO-2). Successful grafting of p-toluidine at the graphitic framework of graphene oxide was confirmed using infrared spectroscopy and ultraviolet-visible spectroscopy. X-ray photoelectron spectroscopy showed the simultaneous reduction and modification. The reduced weight loss, increased initial decomposition temperature and enhanced residue formation indicate significant improvement of the thermal stability of MGO compared to GO. In addition, MGO-2 has greater thermostability and hydrophobic properties than MGO-1, with a water/air contact angle of ∼126.4°. The hydrophobic and thermostable MGO material could be applied to separate organic contaminants from water, which has great potential in environmentally friendly, low-cost advanced liquid–liquid separation or water treatment technologies.

Nanocomposite Hole-Extraction Layers for Organic Solar Cells

The influence of nanocomposite hole-extraction layers on the performance of organic photovoltaic (OPV) cells based on blends of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C-61-buytyric acid methyl ester (PCBM) has been investigated. The hole-extraction layers consist of poly(3,4,-ethylene dioxythiophene) polystyrene sulfonic acid (PEDOT:PSS) doped with different concentrations of multiwall carbon nanotubes (MWCNTs). Compared with a pristine device (i.e., without MWCNTs), the MWCNTs-doped OPV cells shows an improved short-circuit current density, fill factor, and power conversion efficiency from 8.82 to 9.03 mA/cm2, 0.43 to 0.474, and 2.12% to 2.39% (i.e., by about 13%), respectively. Reasons for the improved performance of the devices are discussed. It shows that the reduction of series resistance of the devices might be correlated with the improvement of the OPV cells, performance achieved through the incorporation of MWCNTs into the hole-extraction layer of PEDOT:PSS.

Microstructure and Mechanical Properties of Al2O3/Er3Al5O12 Binary Eutectic Ceramic Prepared by Bridgman Method

Directionally solidified Al2O3/Er3Al5O12 (EAG) eutectic ceramic was prepared via vertical Bridgman method with high-frequency induction heating. The effects of the growth rate on the microstructure and mechanical properties of the solidified ceramic were investigated. The experimental results showed that there were no pores or amorphous phases in the directionally solidified Al2O3/EAG eutectic ceramic. Al2O3 phase was embedded in the EAG matrix phase, and the two phases were intertwined with each other to form a typical binary eutectic “hieroglyphic” structure. With the increase of growth rate, the phase size and spacing of the solidified Al2O3/EAG ceramic both decreased, and the growth rate and phase spacing satisfied the λ2v ≈ 60 formula of Jackson-Hunt theory. The cross section microstructure of the solidified ceramic always exhibited an irregular eutectic growth, while the longitudinal section microstructure presented a directional growth. The mechanical properties of the solidified ceramic gradually increased with the increase of growth rate, and the maximum hardness and fracture toughness could reach 21.57 GPa and 2.98 MPa·m1/2 respectively. It was considered that the crack deflection and branching could enhance the toughness of the solidified ceramic effectively.

On the mechanism of conductivity enhancement in PEDOT/PSS film doped with sorbitol

Abstract The mechanism of conductivity enhancement in PEDOT/PSS film doped with sorbitol is investigated by X-ray diffraction (XRD), Fourier transform Raman spectroscopy (FT-RM), Atomic force microscopy (AFM), Scanning electron microscopy (SEM). The XRD show that the amorphous state of sorbitol-doped films is not changed and the FT-RM indicate that the main characteristic absorption peak of PEDOT shifts to red. These observations indicate that the increase in conductivity is not attributed to the crystallization behavior of PEDOT, but to the change of the resonant structure of PEDOT chain from a ‘benzoid’ to a ‘quinoid’ structure, which increase the rigidity of PEDOT chain. In addition, there is a conformational conversion of the PEDOT chains from the coil structure to expanded-coil or linear structure. These chains changes are helpful to charge transport through the PEDOT chains and conductivity enhancement of composite films. The increased inter-molecule interactions were investigated by the morphological changes of films as observed in AFM and SEM images, which further confirmed the change of the resonant structure of PEDOT chain.