Jingquan Liu

One-step solvothermal preparation of Fe3O4/graphene composites at elevated temperature and their application as anode materials for lithium-ion batteries

A one-step high-temperature solvothermal process (can be used up to 400 °C) has been explored for the preparation of Fe3O4/graphene composites. The influence of high temperature (>230 °C) on the structure, morphology and electrochemical properties of the resulting Fe3O4/graphene composites was investigated by XRD, SEM, TEM and N2 adsorption–desorption measurements. Electrochemical performances of the as-prepared Fe3O4/graphene composites at different temperatures were evaluated in coin-type cells as anode materials for lithium-ion batteries. In comparison with the traditional solvothermal method (<240 °C), the high-temperature method does not require an additional calcination process yet it still could result in Fe3O4/graphene composites with pure phase and excellent electrochemical properties. A preferred solvothermal temperature of 280 °C has been deduced based on a series of control experiments. The Fe3O4/graphene composite derived at 280 °C exhibited a high reversible capacity of 907 mA h g−1 at 0.1 C (92.6 mA g−1) even after 65 cycles, showing outstanding cycle stability. It also exhibited a high rate capability of 410 mA h g−1 at 2 C (1852 mA g−1). The role of the graphene substrates in improving the electrochemical properties of the composite is discussed based on the morphology, structure, phase and electrochemical property studies.

An RAPET approach to in situ synthesis of carbon modified Li4Ti5O12 anode nanocrystals with improved conductivity

Carbon modified lithium titanate (Li4Ti5O12) anode nanocrystals for Li-ion batteries were synthesized by directly treating the titanium alkoxide and lithium acetate ethanol solution via the Reaction under Autogenic Pressure at Elevated Temperature (abbreviated to RAPET). The mixture of the liquid precursors decomposed during the RAPET process and then reacted in situ and transformed into carbon-modified Li4Ti5O12 anode nanocrystals. The organic moieties in the titanium alkoxide and the lithium salt provided both the oxygen and carbon for the synthesis. The resulting products were characterized by X-ray diffraction (XRD), elemental analysis, scanning electronic microscopy (SEM), high resolution transmission electron microscopy (HR-TEM), nitrogen adsorption–desorption measurements, cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and galvanostatic charge–discharge testing. The influences of the titanium alkoxide precursors, i.e. the length of the alkoxy group, on the properties of the final products and the presence of the in situ resulting carbon on the electrochemical performance have been investigated.

Ultrasonic effect on the desizing efficiency of α-amylase on starch-sized cotton fabrics

Enzymatic desizing by α-amylase and ultrasound irradiation are the two important clean technologies in the textile industry. In the present work, with the aim of giving a further insight to the influence of ultrasound on α-amylase activity and its desizing efficiency, the ultrasound-based experiments were afforded in two ways: (i) step-wise treatment of α-amylase by ultrasound and then enzymatic desizing, as well as; (ii) simultaneous utilization of ultrasound and α-amylase for the desizing. By the step-wise strategy, it is found that the ultrasound has negative impact on the α-amylase activity using soluble starch as substrate. However, the sonicated α-amylase possesses higher desizing efficiency because there are higher hydrophobic interactions between sonicated α-amylase protein and starch-sized cotton and thus intensifies its catalytic activity. By the simultaneous procedure, the enhancement to desizing efficiency is more pronounced than that by the step-wise procedure. This can be attributed to comprehensive actions of several reasons such as more effective stirring/mixing mechanism, damages or changes to substrate, more effective catalysis to hydrolytic reactions and faster removal of loosened products from the fabric bulk.

Ultrasound-assisted adsorption of anionic nanoscale pigment on cationised cotton fabrics.

Application of pigments in textile coloring has many advantages such as less water and energy consumption, less effluent load and higher efficiency, so the pigments are perfect alternatives to dyes for eco-friendly coloring. In this work, a stable anionic nanoscale pigment suspension was prepared using a polymeric dispersant to color the cationised cotton with the exhaust method. Meanwhile, ultrasound was carried out during the adsorption to evaluate the ultrasonic influences on the uptake of pigment, adsorption efficiency and final product quality. The uptake of pigment is found to be higher with ultrasonic method than that with conventional technique because of the good dispersing capacity of ultrasound to pigment particles. Besides, it is found that nanoscale pigment has higher adsorption rate when using ultrasonic method because the ultrasound promotes the diffusion of pigment through the fiber-liquid boundary layer. Lastly, the color difference (ΔE) reveals the nanoscale pigment can be deposited on cotton surface more uniformly under ultrasonic condition, improving the product quality obviously.

Utilizing cellulase as a hydrogen peroxide stabilizer to combine the biopolishing and bleaching procedures of cotton cellulose in one bath

In this research, the stabilization effect of cellulase on the decomposition of hydrogen peroxide was investigated for the first time. It was concluded that, regardless of the decomposition mechanism, the cellulase protein could contribute significantly to peroxide stability. This effect stems from the formation of molecular hydrogen bonding between peroxide and cellulase protein or direct sequestering of free metal ions by amino acids in cellulase. Furthermore, based on this stability, a combined biopolishing and peroxide bleaching protocol was developed to improve cotton quality more efficiently. Afterwards, physicochemical properties such as the weight and strength loss, water absorbency, and carbonyl and carboxyl group content of treated cotton cellulose were measured to show the feasibility of the new method. Fourier-transform infrared (FT-IR) and X-ray diffraction (XRD) analyses indicated that the crystallinity index of cotton was increased due to the preferential hydrolysis of amorphous cellulose by cellulase.

The adsorptive and hydrolytic performance of cellulase on cationised cotton

In this research, the cotton fabrics were cationised by a cationic agent to change their surface electric properties. The cationised cotton fabrics were then bio-polished by cellulase to explore the influence of cationisation on the adsorptive and hydrolytic performance of cellulase. The experimental results from cellulase adsorption reveal the cationisation of cotton can obviously improve the binding efficiency of cellulase protein mainly by the improved electrostatic attraction between oppositely charged cellulase and cationised cotton. The adsorption parameters calculated can further prove this improvement trend. Through measuring the concentration of reducing sugars released and weight loss of cotton during the bio-polishing, it is found the hydrolytic activity toward cotton is partially damaged by the cationisation. The reason can be attributed to the movement restriction and dysfunction of cellulase protein by the cationisation.

Preparation of cellulose based microspheres by combining spray coagulating with spray drying

Porous microspheres of regenerated cellulose with size in range of 1-2 μm and composite microspheres of chitosan coated cellulose with size of 1-3 μm were obtained through a two-step spray-assisted approach. The spray coagulating process must combine with a spray drying step to guarantee the formation of stable microspheres of cellulose. This approach exhibits the following two main virtues. First, the preparation was performed using aqueous solution of cellulose as precursor in the absence of organic solvent and surfactant; Second, neither crosslinking agent nor separated crosslinking process was required for formation of stable microspheres. Moreover, the spray drying step also provided us with the chance to encapsulate guests into the resultant cellulose microspheres. The potential application of the cellulose microspheres acting as drug delivery vector has been studied in two PBS (phosphate-buffered saline) solution with pH values at 4.0 and 7.4 to mimic the environments of stomach and intestine, respectively.

The influences of enzymatic processing on physico-chemical and pigment dyeing characteristics of cotton fabrics

First, a crude cellulase was used to treat cotton fabrics to investigate its influences on the physicochemical properties of cotton. The FTIR and XRD analyses both confirmed the enzymatic treatment could increase the crystallinity of cotton, especially at a higher cellulase dosage. Once treated, the number of dissociable groups (–COOH) in cotton decreased, while that of the reducing groups (–CHO) increased. Second, copper phthalocyanine (CuPc) was selected to prepare an anionic nanoscale pigment dispersion to detect its dyeability on different cotton samples. It was concluded that the enzymatic hydrolysis itself had no significant impacts on the pigment dyeing performance. However, cellulase protein still stayed on the cotton surface after treatment and produced an enhancement effect on the pigment uptake due to strong hydrophobic interactions between them. This could be verified by K/S measurement and SEM observations.

Synthesis and Characterization of N-Doped Porous TiO2 Hollow Spheres and Their Photocatalytic and Optical Properties

Three kinds of N-doped mesoporous TiO2 hollow spheres with different N-doping contents, surface area, and pore size distributions were prepared based on a sol–gel synthesis and combined with a calcination process. Melamine formaldehyde (MF) microspheres have been used as sacrificial template and cetyltrimethyl ammonium bromide (CTAB) or polyvinylpyrrolidone (PVP) was selected as pore-directing agent. Core–shell intermediate spheres of titania-coated MF with diameters of 1.2–1.6 μm were fabricated by varying the volume concentration of TiO2 precursor from 1 to 3 vol %. By calcining the core–shell composite spheres at 500 °C for 3 h in air, an in situ N-doping process occurred upon the decomposition of the MF template and CTAB or PVP pore-directing surfactant. N-doped mesoporous TiO2 hollow spheres with sizes in the range of 0.4–1.2 μm and shell thickness from 40 to 110 nm were obtained. The composition and N-doping content, thermal stability, morphology, surface area and pore size distribution, wall thickness, photocatalytic activities, and optical properties of the mesoporous TiO2 hollow spheres derived from different conditions were investigated and compared based on Fourier-transformation infrared (FTIR), SEM, TEM, thermogravimetric analysis (TGA), nitrogen adsorption–desorption, and UV–vis spectrophotoscopy techniques. The influences of particle size, N-doping, porous, and hollow characteristics of the TiO2 hollow spheres on their photocatalytic activities and optical properties have been studied and discussed based on the composition analysis, structure characterization, and optical property investigation of these hollow spherical TiO2 matrices.

The synchronized wash-off of reactive-dyed cotton fabrics and decolorization of resultant wastewater using titanium dioxide nano-fibers.

In this research, titanium dioxide (TiO2) nano-fibers with a well-organized anatase structure were synthesized by a hydrothermal method. Their structural properties were characterized by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), and transmission electron microscope (TEM) analysis, respectively. Subsequently, the TiO2 nano-fibers were optically excited under the ultraviolet (UV) irradiation to decolorize the reactive dye solution. The influences of initial pH, concentrations of reactive dye and TiO2 nano-fibers as well as irradiation time on rate of photocatalytic decolorization were investigated. Based on their excellent photocatalytic performance, a novel method for achieving the synchronized wash-off of reactive-dyed cotton and decolorization of resultant wastewater was developed. It was found that the wash fastness of reactive-dyed cotton after TiO2-based wash-off was equal to that after standard way. The influences of TiO2-based wash-off on the properties of cotton substrates were determined by Fourier transform infrared spectroscopy (FTIR), XRD, and scanning electron microscope (SEM) analysis, respectively, which indicated that this new synchronized method would exert few damages to the cotton substrate.