Peter R. Chang

Characterization of magnetic soluble starch-functionalized carbon nanotubes and its application for the adsorption of the dyes

Soluble starch-functionalized multiwall carbon nanotube composites (MWCNT-starch) were prepared to improve the hydrophilicity and biocompatibility of MWCNTs. Characterization of the MWCNT-starch by Fourier transform infrared (FTIR) spectroscopy, ultraviolet-visible (UV-vis) spectroscopy, X-ray diffraction (XRD), transmission electron microscope (TEM) and thermogravimetric analysis (TG), showed that the starch component (about 14.3 wt%) was covalently grafted onto the surface of MWCNT. MWCNT-starch-iron oxide composites, intended for use as adsorbents for the removal of dyes from aqueous solutions, were prepared by synthesizing iron oxide nanoparticles at the surface of MWCNT-starch. Starch acts as a template for growth of iron oxide nanoparticles which are uniformly dispersed on the surface of the MWCNT-starch. MWCNT-starch-iron oxide exhibits superparamagnetic properties with a saturation magnetization (23.15 emu/g) and better adsorption for anionic methyl orange (MO) and cationic methylene blue (MB) dyes than MWCNT-iron oxide.

Transitional properties of starch colloid with particle size reduction from micro- to nanometer

High-pressure homogenization was used to disperse starch particles in water and reduce the size from micro- to nanometer. The resultant starch colloids were characterized by particle morphology, mean size, size distribution, and zeta potential. Starch slurries were transformed from a mixture containing sediment, dispersion, and sol, to gel as a result of reduction of the particle size from 3-6mum to 10-20nm under a pressure of 207MPa. Furthermore, this process led to the transition of fluid properties without affecting the crystal structure and thermal stability of starch granules. Viscosity of the colloids increased with an increased number of homogenization passes, accompanied by a decreased particle size, narrower particle size distribution (PSD), and an increased absolute zeta potential, indicating the formation of a suspension or stable gel composed of nanoparticles. Lognormal and two other mathematical functions were established to describe the PSDs and their relationship to the homogenization passes. Hence, an environmentally friendly means of producing starch-based nanoparticles or nanogels with high yields, and predictable size and viscosity properties was presented.

Bamboo fiber and its reinforced composites: structure and properties

Natural plant fibers have unequivocally contributed economic prosperity and sustainability in our daily lives. Particularly, bamboo fibers have been used for industrial applications as diverse as textiles, paper, and construction. Recent renewed interest in bamboo fiber (BF) is primarily targeted for the replacement or reduction in use of glass fiber from non-renewable resources. In this review, various mechanical, chemical, and biological approaches for the preparation and separation of macro-, micro-, and nano-sized fibers from raw bamboo are summarized. The differences in the mechanical, thermal, and other properties of fibers from different materials are linked to their size, aspect ratio, surface charge and groups, and their function in nature. Biocomposites made of BF are considered to be green, environmentally responsible eco-products. Different processing parameters such as fiber extraction, surface modification, and synthesis of the composites affect the characteristics of composites. Fiber length, orientation, concentration, dispersion, aspect ratio, selection of matrix, and chemistry of the matrix must all be considered during fabrication in order to achieve desirable functionalities and performance. Because of the hydrophilic nature of BF, different methods may be adopted to improve interfacial surface adhesion. A better understanding of the fiber structure and characteristics that influence composite performance could lead to the development of additives, coatings, binders, or sizing suitable for natural fiber and a variety of polymeric matrices.

Effect of polysaccharide nanocrystals on structure, properties, and drug release kinetics of alginate-based microspheres

Polysaccharide nanocrystals, such as rod-like cellulose nanocrystals and chitin whiskers and platelet-like starch nanocrystals, were incorporated into alginate-based nanocomposite microspheres with the aim of enhancing mechanical strength and regulating drug release behavior. The structures and properties of the sols and the resultant nanocomposite microspheres were characterized by rheological testing, Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The presence of polysaccharide nanocrystals increased the stability of the crosslinked network structure, and the nanocomposite microspheres consequently exhibited prominent sustained release profiles, as demonstrated by inhibited diffusion of theophylline. Furthermore, based on the drug release results, the release kinetics and transport mechanisms were analyzed and discussed.

Preparation, modification, and application of starch nanocrystals in nanomaterials: a review

During the past decade, much work has been devoted to the preparation of nanomaterials by blending starch nanocrystals from different sources with various polymer matrices. The following paper summarizes the most up-to-date information available relating to starch nanocrystals and their contribution to research, application, and advancement of diversified nanomaterials. This paper provides an overview of aspects related to starch nanocrystals, including methods for extraction and preparation, chemical modification (with particular emphasis on the modification methods and strategies), reinforcing effects and mechanisms, and applications and prospects.

Biomimetic soy protein nanocomposites with calcium carbonate crystalline arrays for use as wood adhesive.

Despite the biodegradability, non-toxicity, and renewability, commercially available soy protein-based adhesives still have not been widely adopted by industry, partially due to their disappointing performances, i.e., low glue strength in the dry state and no glue strength in the wet state. In this study, biomimetic soy protein/CaCO(3) hybrid wood glue was devised and an attempt made to improve the adhesion strength. The structure and morphology of the adhesive and its fracture bonding interface and adhesion strength were investigated. Results showed that the compact rivets or interlocking links, and ion crosslinking of calcium, carbonate, hydroxyl ions in the adhesive greatly improving the water-resistance and bonding strength of soy protein adhesives. Glue strength of soy protein hybrid adhesive was higher than 6 MPa even after three water-immersion cycles. This green and sustainable proteinous hybrid adhesive, with high glue strength and good water-resistance, is a good substitute for formaldehyde wood glues.

The composites based on plasticized starch and graphene oxide/reduced graphene oxide.

The graphite was oxidized to prepare graphene oxide (GO), and GO was reduced by glucose to obtain reduced graphene oxide (RGO) sheet. There were abundant and residual oxygen-containing groups on GO and RGO, respectively. Compared to graphite, the GO and RGO sheets appeared flat and transparent, and the aqueous suspensions followed the Lambert-Beers law well. The composites were also fabricated by using GO and RGO as the filler in plasticized-starch (PS) matrix. Because of more oxygen-containing groups, GO could form the stronger interaction with PS matrix than RGO. And GO/PS composites exhibited better tensile strength, elongation at break and moisture barrier than RGO/PS composites, but lower thermal stability. GO/PS composites could protect against UV light, while the conductivities of RGO/PS composites could reach 1.07×10(-4), 6.92×10(-4) and 0.01 S/cm, respectively stored at RH50, 75 and 100%.

Structure and mechanical properties of new biomass-based nanocomposite: Castor oil-based polyurethane reinforced with acetylated cellulose nanocrystal

New nanocomposites consisting of a castor oil-based polyurethane matrix filled with acetylated cellulose nanocrystals (ACNs) were developed. The ACN exhibited improved dispersion in tetrahydrofuran as a blending medium, and reduced polarity as compared with unmodified cellulose nanocrystals, resulting in a high loading level of 25 wt% in the nanocomposite. As the ACN loading-level increased from 0% to 25%, the tensile strength and Youngs modulus of the nanocomposites increased from 2.79 MPa to 10.41 MPa and from 0.98 MPa to 42.61 MPa, respectively. When the ACN loading-level was 10 wt%, the breaking elongation of the nanocomposites reached the maximum value of more than twice that of the polyurethane. The enhanced mechanical performance was primarily attributed to the formation of a three-dimensional ACN network and strong interfacial interactions between filler and matrix. This work produced new polyurethane-based nanocomposites containing modified cellulose nanocrystal with a high biomass content. Its high performance could contribute to potential applications.

Hydrophobic modification of cellulose nanocrystal via covalently grafting of castor oil

Hydrophobic cellulose nanocrystals (CNs) have been prepared by grafting isocyanate-terminated castor oil, a kind of natural vegetable oil, onto their surface. The existence of castor oil component in the modified cellulose nanocrystals was verified by Fourier transform infrared spectroscopy, solid-state 13C NMR spectra and X-ray photoelectron spectroscopy. At the same time, X-ray diffraction and transmission electron micrographs further proved that the crystalline structure and large aspect ratio of cellulose nanocrystals were essentially preserved after chemical grafting. Furthermore, the surface of modified cellulose nanocrystals appeared to be hydrophobic as indicated by contact angle measurements. The value of the polar component of surface energy decreased from 21.5 mJ/m2 to almost zero via grafting castor oil. These novel hydrophobic castor oil-grafted cellulose nanocrystals appear as valuable alternatives to formulate bionanocomposites with non-polar polymers for optimized performances.

Modification of porous starch for the adsorption of heavy metal ions from aqueous solution.

Porous starch xanthate (PSX) and porous starch citrate (PSC) were prepared in anticipation of the attached xanthate and carboxylate groups respectively forming chelation and electrostatic interactions with heavy metal ions in the subsequent adsorption process. The lead(II) ion was selected as the model metal and its adsorption by PSX and PSC was characterized. The adsorption capacity was highly dependent on the carbon disulfide/starch and citric acid/starch mole ratios used during preparation. The adsorption behaviors of lead(II) ion on PSXs and PSCs fit both the pseudo-second-order kinetic model and the Langmuir isotherm model. The maximum adsorption capacity from the Langmuir isotherm equation reached 109.1 and 57.6 mg/g for PSX and PSC when preparation conditions were optimized, and the adsorption times were just 20 and 60 min, respectively. PSX and PSC may be used as effective adsorbents for removal of heavy metals from contaminated liquid.