Shuping Wu

Antioxidant and antimicrobial activity of Maillard reaction products from xylan with chitosan/chitooligomer/glucosamine hydrochloride/taurine model systems

The structure, UV absorbance, browning intensity, fluorescence changes, antioxidant activity and antimicrobial assessment of Maillard reaction products (MRPs) derived from xylan with chitosan, chitooligomer, glucosamine hydrochloride and taurine model systems were evaluated. The results revealed that all MRPs had similar infrared spectra and molecular structures. MRPs from different model systems on the UV absorbance at 294 nm after heated 90 min and browning intensity at 420 nm showed the similar law: xylan-taurine > xylan-glucosamine hydrochloride > xylan-chitooligomer > xylan-chitosan, and the order of DPPH scavenging activity of MRPs was as follows: xylan-chitosan > xylan-chitooligomer > xylan-glucosamine hydrochloride > xylan-taurine, which revealed that the properties of MRPs were closely related to molecular weight of model systems. Moreover, the highest radical scavenging activity of MRPs from xylan with chitosan/chitooligomer/glucosamine hydrochloride/taurine model systems was 65.9%, 63.7%, 46.4% and 42.5%, respectively.

Antioxidant and antimicrobial activity of xylan–chitooligomer–zinc complex

In this study, a ternary complex based on natural polysaccharides was explored as a novel food preservative. Chitooligomer was obtained by enzyme hydrolysis of chitosan with immobilised neutral protease, and the degree of polymerisation (DP) was mainly from 2 to 5. Chitooligomer-zinc complex (CGZC) was first produced and then co-heated with xylan to prepare xylan-chitooligomer-zinc complex (XCGZC). XCGZC showed higher antioxidant and antibacterial activity than chitooligomer, chitooligomer-zinc and xylan-chitooligomer. The IC(50) of XCGZC was 5.37 mg/mL, which was equal to the antioxidant ability of 3.28 mg/mL BHT. The diameter of the inhibition zone for XCGZC against Escherichia coli and Staphylococcus aureus was 17.2 ± 0.4 and 30.3 ± 0.6mm vs. control of 6.0mm. Besides, XCGZC had excellent antibacterial activity against Bacillus subtilis, Salmonella typhimurium, Bacillus megaterium. Therefore, XCGZC can be used as a novel promising preservative with antibacterial and antioxidant properties in the food industry.

One-Step Fabrication of Magnetic Carbon Nanocomposite as Adsorbent for Removal of Methylene Blue

Magnetic Fe3O4@C nanocomposites with well-defined core@shell structure were synthesized via a facile one-step solvothermal process using ferrocene as both iron and carbon resource in the presence of hydrogen peroxide (H2O2). The as-prepared Fe3O4@C nanocomposites were employed as adsorbent materials for removal of methylene blue (MB) from aqueous solution. Several experimental parameters, including contact time, acidity of the solution, and initial MB concentration were investigated. The result showed that the equilibrium uptake of MB was related to the MB initial concentration as well as acidity of the solution. The adsorption kinetics of MB was dominated by the pseudo-second order reaction model. Significantly, the synthesized Fe3O4@C nanocomposites could be easily isolated from the adsorption system after adsorbing MB and showed prominent reusability. All results indicated that the prepared Fe3O4@C composites had the potential to be used as adsorbents for the removal of dye pollutant from wastewater.

Switchable polymer reactor composed of mussel-inspired polymer that contains Au nanoparticles

This study was aimed at addressing the present challenge in self-controlled catalysis, as to how to furnish smart catalysts with robust switchable ability in aqueous media. This objective was reached by developing a marine mussel-inspired polymer reactor that was capable of adapting to switch in aqueous media. This polymer reactor was composed of catalytic Au nanoparticles and a mussel-inspired polymer carrier that contained self-assembled switching interactions. The self-assembled switching interactions, by opening and closing, acted as a molecular switch for providing controlled access to the encapsulated metal nanoparticles, which caused switchable catalytic ability. In virtue of the mussel-mimicking functionality, the switchable catalytic behavior at this polymer reactor was repeatable and compatible with aqueous media, which involved neither hydrophilic/hydrophobic paradigm nor any leaching of metal nanoparticles. In this way, this polymer reactor demonstrated a robust switchable ability. This new protocol shows a promising prospect to develop robust smart catalysts for controlled catalytic processes occurring in aqueous media.

An enzyme-like imprinted-polymer reactor with segregated quantum confinements for a tandem catalyst

This study was aimed at addressing the present challenge in tandem catalysts, as to how to furnish catalysts with tandem catalytic-ability without involving the precise control and man-made isolation of different types of catalytic sites. This objective was realized by constructing an enzyme-like imprinted-polymer reactor made of a unique polymer composite inspired from the compartmentalization of cells, a composite of a reactive imprinted polymer (containing acidic catalytic sites), and encapsulated metal nanoparticles (acting as catalytic reduction sites). The compilation of two types of catalytic sites with admissible access allowed this reactor to behave like compartments of cells for enzymatic reactions and hence catalytically constituted two quantum interaction-segregated domains, which led to the occurrence of catalytic tandem processes. Unlike the reported functional reactors that run tandem catalysis by largely depending on the precise control and man-made isolation of different types of catalytic sites, tandem catalysis in this reactor run naturally with segregated quantum confinements, which does not involve the precise control and isolation of different types of catalytic sites. This protocol presents new opportunities for the development of functional catalysts for complicated chemical processes.

Ternary carboxymethyl chitosan-hemicellulose-nanosized TiO2 composite as effective adsorbent for removal of heavy metal contaminants from water

A ternary composite consisting of carboxymethyl chitosan, hemicellulose, and nanosized TiO2 (CHNT) was prepared by incorporating TiO2 nanoparticles into the pre-synthesized carboxymethyl chitosan-hemicellulose polysaccharide network. The microstructure and chemical composition of the obtained CHNT was characterized by TEM, SEM, FTIR, and TGA. The adsorption of some toxic heavy metals including Ni(II), Cd(II), Cu(II), Hg(II), Mn(VII), and Cr(VI), onto the as-prepared CHNT composite was investigated. The effects of pH, temperature and contacting time on the adsorption process were studied. Results revealed that the CHNT composite exhibited efficient adsorption capacity of the above metal ions from aqueous solution due to its favorable chelating groups in structure. The adsorption process was best described by the pseudo-second-order kinetic model, while isotherm modeling revealed that the Langmuir equation better described the adsorption on CHNT as compared to Freundlich model. Moreover, the CHNT loaded metal ions can be easily regenerated with EDTA and reused repeatedly up to five cycles. The environmental friendly hybrids were expected to be a promising candidate for future practical application in heavy metal contaminated water treatment.

Progress on electrochemical sensors for the determination of heavy metal ions from contaminated water

ABSTRACTWith the development of modern industry, heavy metal pollution is increasingly becoming the focus of government and citizen concern around the globe. Some heavy metals such as Pb, Hg, As, Cr and Cd are highly toxic and hazardous to the human health due to their non-biodegradable nature even at lower levels of exposure. Therefore, it is extremely important and necessary to develop effective and accurate techniques for the detection of heavy metal ions. In this review, various electrochemical sensors for the determination of heavy metal ions are introduced, including electrochemical enzyme sensor, electrochemical immunosensor, electrochemical nucleic acid sensor, the electrochemical whole cell biosensor, imprinted sensor and novel nanomaterial modified electrochemical sensors. The advancements in the techniques of detecting heavy metals and the future development trends of these methods are discussed.

Polymer Composite Reactor with “Autonomous” Access for Aquatically Self-Governed Catalytic Ability

This study was aimed at addressing the present challenge in self-controlled catalysts, about how to furnish the catalysts with self-governed catalytic ability in water. This objective was met by constructing a polymer composite reactor inspired from marine mussels, made of an aquatically autonomous polymer and encapsulated metal nanoparticles. The aquatically autonomous properties at the polymer support, in combination with the catalytic ability of metal nanoparticles, allowed the reactor to run catalysis with aquatically ‘autonomous’ access, which led to the occurrence of aquatically self-governed catalytic ability. This reactor showed poor catalytic reactivity in water at relatively low temperatures due to the ‘closed’ polymeric networks, which blocked access to the encapsulated metal nanoparticles. This reactor showed, however, significant reactivity in water at relatively high temperatures in response to the ‘openness’ of the access. Unlike the switchable catalysis at reported catalytic reactors which usually involved conventional hydrophilic/hydrophobic transition and the leaching of metal nanoparticles, the switchable catalysis at this reactor ran naturally with the aquatically autonomous access that did not involve any hydrophilic/hydrophobic transition and the leaching of metal nanoparticles. This protocol suggested opportunities for developing robust smart catalysts for aquatic chemical processes.

Smart Tandem Catalyst Developed with Sundew's Predation Strategy, Capable of Catching, Decomposing and Assimilating Preys

This study is aimed at the present challenge in tandem catalysts, addressing how to endow the catalysts with self‐controlled tandem catalytic‐ability. By borrowing the predation strategy from sundew, the objective was originally met by reporting a smart tandem catalyst which can self‐control the tandem catalytic behavior by catching, decomposing and assimilating the engaging molecules (such as 4‐nitrophenyl acetate). This catalyst was made of a unique leaf containing two functional layers where each may be responsible for one coupled process. The first layer in this catalyst was fabricated with a zipper‐like reactive polymer capable of opening and closing, which allowed the catalyst to catch and decompose 4‐nitrophenyl acetate. The second layer in this catalyst allowed, however, further access to assimilate the decomposed substrate (i. e., 4‐nitrophenol), made of an antibody‐like polymer and encapsulated metal nanoparticles. In this way, the use of this catalyst led to the occurrence of the self‐controlled tandem catalytic‐ability. This novel design suggests a new protocol for developing smart tandem catalysts, which opens new opportunities for controlled tandem catalytic processes.

Highly sensitive and selective ion-imprinted polymers based on one-step electrodeposition of chitosan-graphene nanocomposites for the determination of Cr(VI)

A sensitive and selective electrochemical sensor based on ion-imprinted chitosan-graphene nanocomposites (IIP-S) has been developed for the determination of Cr(VI). The ion-imprinted polymers were constructed by one-step electrodeposition. The morphology and structure of IIP-S were characterized by SEM, TEM, XRD, FTIR and EDS, respectively. Meanwhile, the electrochemical behavior of IIP-S was investigated using CV, EIS and DPV. The linear range of IIP-S was from 1.0 × 10-9 to 1.0 × 10-5 mol/L, with the low detection limit of 6.4 × 10-10 mol/L (S/N = 3). The sensor exhibited high selectivity for the determination of Cr(VI) in the presence of Zn(II), Co(II), Cu(II), Ni(II), Mn(II), MnO4-, C2O42-, S2O62- and MoO42- ions. The IIP-S also provided excellent stability and good repeatability that the sensitivity remained 85% after 9 cycles of rebinding-removal, while the sensitivity retained 87% of its initial response storing at 4 °C for 17 days. Moreover, it was successfully applied to the detection of Cr(VI) ions in tap water and river water.