Sijun Xu

Sodium alginate/graphene oxide aerogel with enhanced strength–toughness and its heavy metal adsorption study

Ordered porous sodium alginate/graphene oxide (SAGO) aerogel was fabricated by in situ crosslinking and freeze-drying method. GO, as reinforcing filler, can be easily incorporated with SA matrix by self-assembly via hydrogen bonding interaction. Compared with pure SA aerogel, the as-prepared SAGO exhibited excellent mechanical strength and elasticity, and the compression strength of SAGO can reach up to 324 kPa and remain 249 kPa after five compression cycles when 4 wt% GO was added, which were considered significant improvements. SEM result presents that the addition of GO obviously improves the porous structures of aerogel, which is beneficial for the enhancement of strength-toughness and adsorbability. As a consequence, the adsorption process of SAGO is better described by pseudo-second-order kinetic model and Langmuir isotherm, with maximum monolayer adsorption capacities of 98.0 mg/g for Cu2+ and 267.4 mg/g for Pb2+, which are extremely high adsorption capacities for metal ions and show far more promise for application in sewage treatment.

Design and characterization of self-cleaning cotton fabrics exploiting zinc oxide nanoparticle-triggered photocatalytic degradation

Self-cleaning surfaces are functional structures with application in smart textiles. In this study, self-cleaning cotton fabrics were fabricated by coating photocatalytic zinc oxide nanoparticles (ZnO NPs) on cotton surfaces, using a traditional dip-pad-dry-cure coating process. The coatings and ZnO content-dependent self-cleaning properties of the coated fabrics were investigated to evaluate their potential in practical application. The ZnO NP-coated cotton fabrics were characterized by Fourier-transform infrared spectroscopy, X-ray diffraction, field-emission scanning electron microscopy, and thermogravimetric analysis. Methylene blue was used as a test contaminant to qualitatively assess the self-cleaning properties of the fabrics. The removal efficiency was determined for fabrics with different ZnO contents, under different solar irradiation times. Consecutive photocatalytic degradations were carried out to investigate the self-cleaning durability of the fabrics. This involved repeatedly contaminating the same fabric position and subsequent cleaning by photocatalytic degradation. The self-cleaning properties of the fabrics depended on their ZnO NP content. A higher wt% of ZnO NPs in the coated fabric resulted in more pronounced photocatalytic degradation than fabrics with a lower wt%. The self-cleaning performance of the higher wt% ZnO NP fabric decreased slightly after the third consecutive photocatalytic degradation. Results of wash fastness showed color removal after 10 times washing under light irradiation. Moreover, the ZnO NP-coated fabrics exhibited excellent ultraviolet blocking properties. These findings provide a potential model for the practical application of self-cleaning textiles.

Strength-controllable graphene oxide amphiprotic aerogels as highly efficient carrier for anionic and cationic azo molecules

Ice-bath self-assembly was employed to fabricate the GO/AP-MCC/CS aerogel based on natural materials. The components are amphiprotic microcrystalline cellulose (AP-MCC), chitosan (CS), and graphene oxide (GO), which act as the main framework, auxiliary framework and adhesive, respectively. The results of characterization determines the components form the GO/AP-MCC/CS aerogel according to chemical interactions. The mechanical properties depend largely on the mass ratio of AP-MCC/CS, which can be regulated by controlling the contents of AP-MCC and CS. The resultant GO/AP-MCC/CS aerogel was observed possessing three-dimensional (3D) interpenetrating porous networks with wrinkled structure on the inner wall, which provide a good encapsulation capacity for the guest molecules. As expected, owing to the amphiprotic properties and large specific surface area, GO/AP-MCC/CS aerogel exhibits high-efficiency load capacity for both anionic (CR) and cationic azo molecules (MB), which can reach up to about 132.2 mg/g for CR and 123.2 mg/g for MB, respectively.

Preparation of silver nanoparticle-coated calcium alginate fibers by hyperbranched poly(amidoamine)-mediated assembly and their antibacterial activity

A facile approach has been developed for preparing silver nanoparticle (AgNP)-coated calcium alginate fibers by hyperbranched poly(amidoamine) (HBPAA)-mediated assembly of AgNPs onto the surface of calcium alginate fibers in aqueous solution. Amino-functionalized AgNPs were synthesized in aqueous media using HBPAA as the reducing and capping agent. The assembly of AgNPs on calcium alginate fibers was realized through electrostatic and hydrogen bonding interactions between calcium alginate fibers and HBPAA molecules capped on the surface of AgNPs. Scanning electron microscopy and X-ray photoelectron spectroscopy characterizations demonstrated that high density of metallic AgNPs were uniformly distributed on the fiber surface. The results of antibacterial tests indicated that the coated calcium alginate fibers exhibited high antibacterial activity against gram-positive and gram-negative bacteria.

Poly(amidoamine)-mediated self-assembly of hydroxyl-modified anatase TiO2 nanocrystals on cotton fabric

Here, water-soluble hydroxyl-terminated hyperbranched poly(amino ester) (HBPAE)-capped titanium dioxide nanocrystals (TiO2 NCs) were synthesized for coating a cotton fabric via an amino-terminated hyperbranched poly(amidoamine) (HBPAA)-mediated self-assembly strategy in order to produce a controllable and uniform TiO2 coating on the cotton surface. As-prepared TiO2 NCs were characterized by transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), and X-ray diffraction (XRD). It was demonstrated that hydroxyl-modified TiO2 NCs were egg-shaped and had a narrow size distribution. A TiO2 NC-coated cotton fabric was prepared by sequential impregnation with solutions of HBPAAs and TiO2 NCs. The attachment of HBPAAs to TiO2 NCs was evaluated by FTIR. It was shown that HBPAAs were chemically bound to the cotton surface. FESEM and XRD characterizations demonstrated that TiO2 NCs could self-assemble on a cotton fabric efficiently and were distributed uniformly on the cotton surface.