Preparation and characterization on cellulose nanofiber film

In this study, cellulose nanofibers were obtained from wood pulp using a chemo-mechanical method and thin films were made of these cellulose nanofibers. The morphology of the films was studied by scanning electron microscopy (SEM). SEM image analysis revealed that the films were composed of cellulose nanofibers with an average diameter of around 32 nm. Other properties were also characterized, including the degree of crystallinity by X-ray diffraction, chemical bonding by infrared attenuated total reflectance analysis, and thermal properties by differential scanning calorimetry. The foldable, strong, and optically translucent cellulose nanofiber films thus obtained have many potential applications as micro/nano electronic devices, biosensors and filtration media, etc.

Abnormal transmittance of refractive-index-modified ZnO/organic hybrid films

The refractive index of ZnO/organic nanocomposite films was modified in the range from 1.44 to 1.55, while maintaining high visible transparency. The transparency of the nanocomposite films showed an abnormal behaviour as a function of the loading level of inorganic particles, because it did not decrease according to the Beer-Lambert law, but rather saturated to a near-constant value at high particle loading levels above 8 vol.-%. On the other hand, the refractive index of the film showed good agreement with the Bruggemann model, linearly increased as particle concentration increased. This result indicates the possibility of fabricating highly transparent nanocomposite films with controlled refractive indices.

Blend films of natural wool and cellulose prepared from an ionic liquid

Natural wool/cellulose blends were prepared in an ionic liquid green solvent, 1-butyl-3-methylimidazolium chloride (BMIMCl) and the films were formed subsequently from the coagulated solutions. The wool/cellulose blend films show significant improvement in thermal stability compared to the coagulated wool and cellulose. Moreover, the blend films exhibited an increasing trend of tensile strength with increase in cellulose content in the blends which could be used for the development of wool-based materials with improved mechanical properties, and the elongations of the blends were considerably improved with respect to the coagulated films of wool and cellulose. It was found that there was hydrogen bonding interaction between hydroxyl groups of wool and cellulose in the coagulated wool/cellulose blends as determined by Fourier transform infrared (FTIR) spectroscopy. The ionic liquid was completely recycled with high yield and purity after the blend film was prepared. This work presents a green processing route for development of novel renewable blended materials from natural resource with improved properties.

Amine enrichment of thin-film composite membranes via low pressure plasma polymerization for antimicrobial adhesion

Thin-film composite membranes, primarily based on poly(amide) (PA) semipermeable materials, are nowadays the dominant technology used in pressure driven water desalination systems. Despite offering superior water permeation and salt selectivity, their surface properties, such as their charge and roughness, cannot be extensively tuned due to the intrinsic fabrication process of the membranes by interfacial polymerization. The alteration of these properties would lead to a better control of the materials surface zeta potential, which is critical to finely tune selectivity and enhance the membrane materials stability when exposed to complex industrial waste streams. Low pressure plasma was employed to introduce amine functionalities onto the PA surface of commercially available thin-film composite (TFC) membranes. Morphological changes after plasma polymerization were analyzed by SEM and AFM, and average surface roughness decreased by 29%. Amine enrichment provided isoelectric point changes from pH 3.7 to 5.2 for 5 to 15 min of plasma polymerization time. Synchrotron FTIR mappings of the amine-modified surface indicated the addition of a discrete 60 nm film to the PA layer. Furthermore, metal affinity was confirmed by the enhanced binding of silver to the modified surface, supported by an increased antimicrobial functionality with demonstrable elimination of E. coli growth. Essential salt rejection was shown minimally compromised for faster polymerization processes. Plasma polymerization is therefore a viable route to producing functional amine enriched thin-film composite PA membrane surfaces.

Thermally flexible epoxy/cellulose blends mediated by an ionic liquid

Blends between the widely used thermoset resin, epoxy, and the most abundant organic material, natural cellulose are demonstrated for the first time. The blending modification induced by charge transfer complexes using a room temperature ionic liquid, leads to the formation of thermally flexible thermoset materials. The blend materials containing low concentrations of cellulose were optically transparent which indicates the miscibility at these compositions. We observed the existence of intermolecular hydrogen bonding between epoxy and cellulose in the presence of the ionic liquid, leading to partial miscibility between these two polymers. The addition of cellulose improves the tensile mechanical properties of epoxy. This study reveals the use of ionic liquids as a compatible processing medium to prepare epoxy thermosets modified with natural polymers.

On-site determination of Pb2+ and Cd2+ in seawater by double stripping voltammetry with bismuth-modified working electrodes

To meet the urgent requirement of determining trace Pb2+ and Cd2+ in seawater on site, herein we developed a simple but novel electrochemical method, named as double stripping voltammetry, using only a portable heavy metal analyzer. The proposed method consisted of three steps: First, the targeted heavy metal ions in bulk solution were concentrated onto an ionic liquid-graphite-based paste working electrode (ILGPE), which exhibits a dramatic ability of accumulation, by electrodeposition in the presence of Bi3+. Second, the three-electrode arrangement, including the ILGPE loaded with the reduced products, was transferred into 1.0mL acetate buffer solution, followed by a stripping procedure. Third, the measurement was performed with the other stripping voltammetry procedure by using a glassy carbon electrode as working electrode. Under optimum conditions, the linear range values for Pb2+ and Cd2+ in seawater were 0.2-3.2 μg/L and 0.1-3.2 μg/L, respectively. The concentrations of Pb2+ and Cd2+ in five real samples collected from coastal sites of Qingdao City were determined on site, and the results were in good agreement with that obtained with the atomic absorption spectroscopy method. In addition, the analytical performance of working electrode modified with Bi film by in situ mode was investigated in comparison with that by ex situ mode. The results showed that the in situ mode was much better than the ex situ one.