Natural rubber as a renewable carbon source for mesoporous carbon/silica nanocomposites.

This study is the first report on the preparation of mesoporous carbon/silica (MCS) nanocomposites with tunable mesoporosity and hydrophobicity using natural rubber (NR) as a renewable and cheap carbon source. A series of mesoporous nanocomposites based on NR and hexagonal mesoporous silica (HMS) were prepared via an in situ sol-gel process and used as precursors; then, they were converted into MCS materials by controlled carbonization. The NR/HMS precursors exhibited a high dispersion of rubber phase incorporated into the mesostructured silica framework as confirmed by small-angle X-ray scattering and high-resolution transmission electron microscopy. An increase in the carbonization temperature up to 700 °C resulted in MCS nanocomposites with a well-ordered mesostructure and uniform framework-confined wormhole-like channels. The NR/HMS nanocomposites possessed high specific surface area (500-675 m2 g-1) and large pore volume (1.14-1.44 cm3 g-1). The carbon content of MCS (3.0-16.1 wt%) was increased with an increase in the H2SO4 concentration. Raman spectroscopy and X-ray photoelectron spectroscopy revealed the high dispersion of graphene oxide-like carbonaceous moieties in MCS materials; the type and amount of oxygen-containing groups in obtained MCS materials were determined by H2SO4 concentration. The enhanced hydrophobicity of MCS nanocomposites was related to the carbon content and the depletion of surface silanol groups, as confirmed by the water sorption measurement. The study on the controlled release of diclofenac in simulated gastrointestinal environment suggests a potential application of MCS materials as drug carriers.

Structural transformations at different organizational levels of ethanol-treated starch during heating.

Heating ethanol-treated starch (ETS) is the simplest method to produce granular cold-water swelling starch. Structural transformations of ethanol-treated maize and potato starch (ETMS and ETPS) at the crystalline, lamellae and granular structural levels during heating were investigated through in situ wide- and small-angle X-ray scattering (WAXS and SAXS) combined with light microscopy (LM). The result of in situ WAXS indicated that the native crystalline structure was slowly disrupted up to 82 and 60 °C for ETMS and ETPS, respectively. The initial temperature for the formation of a V-type crystalline structure of ETMS was observed to be 86 °C. The result of paracrystalline analysis suggested that the crystalline lamellae of ETS realigned toward a more ordered register when heated to 80 °C and 70 °C for ETMS and ETPS, respectively. The granular forms of ETMS and ETPS were still preserved at 100 °C, although the characteristic of Maltese cross was not observed. A model was proposed to elucidate transformations of ETS at the three structural levels of starch during heating.

Gallic acid conjugated with gold nanoparticles: antibacterial activity and mechanism of action on foodborne pathogens.

Foodborne pathogens, including Plesiomonas shigelloides and Shigella flexneri B, are the major cause of diarrheal endemics worldwide. Antibiotic drug resistance is increasing. Therefore, bioactive compounds with antibacterial activity, such as gallic acid (GA), are needed. Gold nanoparticles (AuNPs) are used as drug delivery agents. This study aimed to conjugate and characterize AuNP-GA and to evaluate the antibacterial activity. AuNP was conjugated with GA, and the core-shell structures were characterized by small-angle X-ray scattering and transmission electron microscopy. Antibacterial activity of AuNP-GA against P. shigelloides and S. flexneri B was evaluated by well diffusion method. AuNP-GA bactericidal mechanism was elucidated by Fourier transform infrared microspectroscopic analysis. The results of small-angle X-ray scattering showed that AuNP-GA conjugation was successful. Antibacterial activity of GA against both bacteria was improved by conjugation with AuNP because the minimum inhibitory concentration value of AuNP-GA was significantly decreased (P<0.0001) compared to that of GA. Fourier transform infrared analysis revealed that AuNP-GA resulted in alterations of lipids, proteins, and nucleic acids at the bacterial cell membrane. Our findings show that AuNP-GA has potential for further application in biomedical sciences.

SAXS and ATR-FTIR studies on EBT-TSX mixtures in their sol-gel phases.

Our previous study demonstrated that mixtures of tamarind seed xyloglucan (TSX) with appropriate concentrations of eriochrome black T (EBT) produced a gel that could be of benefit for medical use. Here, the sol-gel systems of various fresh and aged mixtures were further investigated using rheological measurements. The nanostructural changes of EBT-TSX sol-gel phases were analyzed using SAXS. The interactions between EBT and TSX in the sol and gel states were examined using ATR-FTIR. SAXS data analysis demonstrated that the mixture containing lower concentration of EBT formed rod-like structures and that with higher concentrations of EBT produced flat particles. The sizes of the TSX structures from the aged mixtures in the gel stage were larger than those from the same mixtures in the sol state. ATR-FTIR spectral changes revealed that the azo and sulfonic acid groups of EBT interacted with the TSX, and the characteristic spectrum of the sulfonic acid group of EBT could discriminate between the sol and gel state of the EBT-TSX systems. The interactions between EBT and TSX may cause conformational changes to TSX and facilitate the sol-gel transition or formation of a gel.