Chenglu Liang

Effect of graphite oxide structure on the formation of stable self-assembled conductive reduced graphite oxide hydrogel

As a novel tissue engineering material and transistor, reduced graphite oxide (rGO) hydrogel is attracting more and more attention, and a stable and highly electrical conductive rGO hydrogel is the cornerstone for these applications. We controlled the structures of graphite oxides (GOs) with three different methods and the corresponding assembled rGO hydrogels were obtained using Vitamin C (VC) as the reducing agent and the stability and electrical resistance of the rGO hydrogel were studied. The results showed that the appropriate interlayer distance and grain size of GO prepared by two-step oxidation were beneficial for VC molecules to insert in the interspace between layers for the reduction. After reduction, the loose and tangled network structure was well assembled, which determines the stability and electrical conductivity of the resulted rGO hydrogel.

Temperature: a nonnegligible factor for the formation of a structurally stable, self-assembled reduced graphite oxide hydrogel

The three-dimensional (3D) architecture of reduced graphite oxide (rGO) hydrogels is of interest in applications such as supercapacitors, soft machines and regenerative medicine, etc. The structural stability of the rGO hydrogel is the foundation for these applications. However, little attention has been paid to this issue. Here, the structural and performance stabilities of rGO hydrogels prepared at different temperatures were investigated in detail. It was found that 40 °C was the most effective condition for the reduction of graphite oxide, as the reducibility of vitamin C was embodied successfully and the network of the rGO hydrogel was formed. The rGO hydrogel prepared at 40 °C showed the best structural stability with time, the lowest electrical resistance and the highest mechanical strength. These results provide guidance for the synthesis of structurally stable rGO hydrogels and their further applications in electrical devices.

Solvent-controlled formation of a reduced graphite oxide gel via hydrogen bonding

As a promising material with broad applications, reduced graphite oxide (rGO) hydrogels have attracted more and more great attention recently. However, most reports on rGO hydrogels focused on their applications, while the formation mechanism has not been paid enough attention. For the first time, we demonstrated the higher the ability of the solvents to form hydrogen bonds with the rGO sheets, the better the structural stability and properties of gel are. This study indicates that hydrogen bonding between solvent molecules and the oxygen-containing functional groups on rGO sheets is vital to achieve high-performance gels.

Sodium ascorbate assisted uniform distribution of Fe3O4 nanoparticles on rGO surface: improved cycling and rate performance of rGO/Fe3O4 anode material for lithium ion batteries

Abstract Reduced graphite oxide (rGO)–magnetite (Fe3O4) composites, promising anode materials for lithium ion batteries, have aroused extensive interest. However, the effects of reducing agents of graphite oxide (GO) on the detailed morphology of the composite were rarely reported. Herein, reducing agents of GO, sodium ascorbate and hydrazine hydrate were selected, and sodium ascorbate was able to control the uniform distribution of Fe3O4 on rGO sheets, resulting in stable cycling performance of above 500 mA h g− 1 after 100 cycles and high capacity of above 1200 mA h g− 1 in the first discharge/charge process. While in the composite reduced by hydrazine hydrate, severe aggregation of Fe3O4 particles and their weak bonding to rGO sheets depleted the buffer effect of rGO, resulting in continuously fading of cycling performance. This work provided a convenient and an effective way of morphology control of rGO–Fe3O4 composite during its one-pot formation.

Crystallization kinetics of γ phase poly(vinylidene fluoride)(PVDF) induecd by tetrabutylammonium bisulfate

AbstractThe γ phase of poly(vinylidene fluoride) (PVDF) was induced by tetrabutylammonium bisulfate and the kinetics of isothermal and non-isothermal crystallization of the induced γ-PVDF in the absence of α phase were investigated with differential scanning calorimeter. The crystallization kinetics were evaluated on the basis of the theory of Avrami and those modified by Jeziorny, Ozawa, Liu and Mo. The Avrami exponent n of the induced γ-PVDF was evaluated and was found to be in the range of 2.4–2.9 for isothermal crystallization and in the range of 3.1−4.5 for non-isothermal crystallization, much higher than those of γ-PVDF homogeneously nucleated at high temperatures as reported in literature. Moreover, the accelerated crystallization rate of the induced γ-PVDF, even faster than the kinetically most favored α phase, was demonstrated by the drastically shortened half-time of crystallization t1/2 and enhanced crystallization rate constant K. It is shown that dominating γ-PVDF could be melt crystallized with a drastically enhanced crystallization rate with the incorporation of tetrabutylammonium bisulfate. Graphical AbstractThe Avrami exponent n of the induced γ-PVDF in the absence of α phase was evaluated and was found to be in the range of 3.1~4.5. The values of which were much higher than those of γ-PVDF homogeneously nucleated at high temperatures as reported in literature, suggesting that the growth of spherulites was three dimensional, while the reported γ-PVDF nucleated at high temperatures usually grows one or two dimensionally in a fibrillar structure.

Metallic 1T-TiS2 nanodots anchored on a 2D graphitic C3N4 nanosheet nanostructure with high electron transfer capability for enhanced photocatalytic performance

Photocatalysis is one of the most promising technologies for solar energy conversion. With the development of photocatalysis technology, the creation of low-dimensional structure photocatalysts with improved properties becomes more and more important. Metallic 1T-TiS2 nanodots with a low-dimensional structure were introduced into environmentally friendly two-dimensional g-C3N4 (2D-C3N4) nanosheets by a solvothermal method. It was found that the ultrathin TiS2 nanodots were uniformly anchored on the surface of the 2D-C3N4. The effective suppression of electron–hole recombination was realized due to the addition of the intrinsic metallic property of 1T-TiS2 in the prepared nanocomposite. The 5 wt% TiS2/2D-C3N4 nanocomposite exhibited the best photocatalytic performance and the degradation rate towards RhB was ca. 95% in 70 min, which showed an improvement of ca. 30% in comparison with 2D-C3N4. The results indicate that the obtained TiS2/2D-C3N4 nanocomposite is a promising photocatalyst for practical applications.

Enhanced nonlinear optical limiting in TiS2 dichalcogenide 2D Sheets

Two dimensional (2D) graphene and transition metal dichalcogenides are an emerging class of extremely interesting materials showing unique physical properties, such as large third-order optical nonlinearity, offering potential applications in optical limiting. Here we report the optical limiting properties of Titanium disufide (TiS2), and Graphene sheets measured using open aperture and photo-acoustic z-scan techniques. Our best results were observed in TiS2 Sheets, yielding an optical limiting of 77% at an irradiance of 0.713 GW/cm2with 2PA and 3PA absorption coefficient to be 80cm/GW and 2000 cm3/GW2 respectively.Also, TiS2 sheets show improved shelf life and stability upon irradiation with higher laser powers. This demonstrates the feasibility of using them as a potential candidate for optical limiting applications.