Xiaofeng Sui

Cellulose Sponge Supported Palladium Nanoparticles as Recyclable Cross-Coupling Catalysts

Robust and flexible cellulose sponges were prepared by dual-cross-linking cellulose nanofiber (CNF) with γ-glycidoxypropyltrimethoxysilane (GPTMS) and polydopamine (PDA) and used as carriers of metal nanoparticles (NPs), such as palladium (Pd). In situ growth of Pd NPs on the surface of CNF was achieved in the presence of polydopamine (PDA). The modified sponges were characterized with FT-IR, XRD, EDX, SEM, TEM, and TGA. XRD, EDX, and TEM results revealed that the Pd NPs were homogeneously dispersed on the surface of CNF with a narrow size distribution. The catalysts could be successfully applied to heterogeneous Suzuki and Heck cross-coupling reactions. Leaching of Pd was negligible and the catalysts could be conveniently separated from the products and reused.

Facile fabrication of redox/pH dual stimuli responsive cellulose hydrogel

A cellulose-based multi-responsive hydrogel was prepared by the facile incorporation of enamine and disulfide bonds in the same system at physiological pH. The cellulose hydrogel was obtained by simply mixing aqueous solutions of cellulose acetoacetate (CAA) and cystamine dihydrochloride (CYS) at room temperature. The internal morphology, structure, and mechanical properties of the cellulose hydrogel were characterized by scanning electron microscopy (SEM), Fourier transform infrared (FTIR) and Raman spectroscopies, nuclear magnetic resonance (NMR), and water retention, porosity, and rheology measurements. The cellulose hydrogel showed reversible sol-gel transitions in response to both pH and redox triggers. In addition, it displayed good stability under physiological conditions. Gels loaded with small molecules showed variable release properties in response to pH or redox stimuli. The preparation protocol presented here could be used to fabricate other multi-responsive polysaccharide hydrogels.

A novel low add-on technology of dyeing cotton fabric with reactive dyestuff:

A novel low add-on dyeing process of cotton fabric with C.I. Reactive Black 5 has been implemented successfully with the assistance of dye-jet ejector units to produce precise wet pick-up ranging from 20% to 50%. The steaming process of the low add-on technology was investigated through evaluating the effects of relative humidity, steaming temperature, steaming time and water ratio on the surface temperature of the wet fabric and their influence on the dye properties, as well as the effect of the wet pick-up on dye properties. The optimal dyeing process was also conducted, including build-up properties and the concentrations of the alkaline agent and the electrolyte via the evaluation of the color strength (K/S value) and dye fixation rate. A comparison was made between the novel low add-on dyeing process and conventional dyeing process by assessing the dye properties, color shade and color levelness. The results indicated that the fabric dyed with the low add-on process had excellent washing fastness, rubbing fastness, a similar color shade and superior levelness in comparison with conventional one-bath pad-steam dyeing.

Thiol–ene click reaction on cellulose sponge and its application for oil/water separation

Thiol–ene click reaction was employed to synthesize a flexible hydrophilic cellulose sponge. The reactive vinyl group was introduced by silanization treatment with vinyl-trimethoxysilicane (VTMO), and the resulting silylated cellulose sponge (SCS) can be subsequently functionalized with various thiol-containing compounds such as 3-mercaptopropionic acid, via temperature induced thiol–ene reactions. The hydrophilic cellulose sponge thus prepared displayed an excellent mechanical strength of 70 KPa at 80% compression strain. The prepared sponge features hydrophilic and underwater oleophobic properties and was used in gravity-driven removal of oil from oil-in-water emulsions and oil/water mixtures with a high separation efficiency. The separation efficiency remained 100% after 10 cycles for an oil/water mixture and 95% after 6 cycles for an oil-in-water emulsion.

Facile synthesis of cellulose derivatives based on cellulose acetoacetate

In the present work, cellulose acetoacetates (CAA) was used as a precursor for preparing diversely functionalized cellulose derivatives. Four amino-bearing compounds, namely hexylamine (HA), l-glutamic acid (Glu), cysteine (Cys), and tyramine (TA) were reacted with acetoacetyl groups providing alkyl-, carboxyl-, thiol-, or phenolic functionalized cellulose. The reaction was conducted under mild conditions without catalysts and UV light. The products were characterized with FT-IR, NMR and solubility measurement. 1H NMR measurement demonstrated the conversion of acetoacetyl groups were ideal, and all the cellulose derivatives demonstrated good solubility in certain solvent. Besides, CAA held a good stability under room temperature. This approach offers broad possibilities for developing new cellulose based materials. Moreover, this protocol can also be applied to fabricate other polysaccharide derivatives.

Precipitated silica agglomerates reinforced with cellulose nanofibrils as adsorbents for heavy metals

Silicon-containing compounds such as silica are effective heavy metal sorbents which can be employed in many applications. This is attributed to the porous nature of hydrothermally-stable silica, endowing such materials with high surface area and rich surface chemistry, all responsible for improving adsorption and desorption performance. However, to this day, the wide application of silica is limited by its skeletal brittleness and high production cost coupled with a risky traditional supercritical drying method. To solve the named problems, herein, precipitated silica agglomerates (referred to as PSA) was crosslinked with TEMPO-oxidized cellulose nanofibrils (TO-CNF) as a reinforcement in the presence of 3-aminopropyltriethoxysilane (APTES), via a facile dual metal synthesis approach, is reported. The resultant new silica-based sponges (TO-CNF PSA) showed desirable properties of flexibility, porosity and multifaceted sorption of various heavy metals with re-usability. The experimental results showed maximum adsorption capacities of 157.7, 33.22, 140.3 and 130.5 mg g−1 for Pb(II), Hg(II), Cr(III) and Cd(II) ions, respectively. Such a facile approach to modify silica materials by attaching active groups together with reinforcement can provide improved and reliable silica-based materials which can be applied in water treatment, gas purification, thermal insulation etc.

Facile preparation of polysaccharide-based sponges and their potential application in wound dressing

Wound exudate adsorption and blood clotting are of critical importance for promoting wound healing in diabetic patients. In this study, cellulose-chitosan hybrid sponges were prepared by a facile pathway with controllable structure and morphology. Aimed at wound dressing, the physical properties, cytocompatibility, and hemocompatibility of the cellulose-chitosan hybrid sponges were evaluated. The results indicated that the hybrid sponges were non-toxic and outperformed silicon in promoting blood coagulation. The sponges could also effectively adsorb abundant wound exudate due to their highly porous structure. Moreover, the maximal shape recovery of these chemically crosslinked sponges from a 50% compression strain was up to 95% of their original thickness, without obviously compromising their macro/microstructure and mechanical properties after 10 cycles. The superior blood coagulation, adsorption performance, and shape recovery properties of the sponges make them ideal for use in making wound dressings for diabetic patients.

A light-weight and high-efficacy antibacterial nanocellulose-based sponge via covalent immobilization of gentamicin

Covalent grafting of gentamicin to nanocellulose-based sponge was realized for the first time. The named sponge was prepared by initially multi-crosslinking among cellulose nanofibers (CNF), cellulose acetoacetate (CAA) and 3-aminopropyl(triethoxy)silane (APTES) followed by surface modification with gentamicin via the formation of enamine bond. The structure and mechanical performances of the obtained gentamicin-functionalized CNF sponge were characterized with FT-IR, XPS, EDX, SEM, Nitrogen adsorption-desorption measurement, and compressive test. Its antibacterial activity against E. coli and S. aureus was evaluated using disc diffusion and colony forming units (CFU) count methods. The results showed that gentamicin was successfully grafted on the surface of CNF sponges without significant change in morphology and slight improvement in mechanical performance. The superior lightness of the sponge (0.0174 g cm-3) was demonstrated by showing the sponge could be supported by a flower branch without crushing it. Gentamicin-functionalized CNF sponges showed excellent antibacterial performance against E. coli and S. aureus, with bactericidal rates of over 99.9%.