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Ultrasonication is often used to disperse nano-particles in aqueous solution. However, a good dispersion of nano-particles in aqueous solution is not always achieved, due to the fact that incoming ultrasonicwaves in liquid are usually reflected and damped at the gas/liquid interface. In this work, we report a so-called wet-grinding assisted ultrasonication (GU) method, in which wet-grinding of multi-walled carbon nanotubes (MWCNTs) in chitosan solution is carried out before ultrasonication. The dispersions of MWCNTs were characterized by visual comparison, UV/vis spectroscopy, and scanning electron microscopy (SEM). The results demonstrate that the dispersion quality of chitosan/MWCNT suspension prepared by wet-grinding assisted ultrasonication is much better than that by ultrasonication or wet-grinding alone. It was found that wet-grinding could improve the water wettability of MWCNTs and eliminate the barrier of air layer around MWCNTs to ultrasonicwaves. Meanwhile, the composite from the chitosan/MWCNTs suspension prepared by GU method has an obvious improvement in mechanical property compared to pure chitosan. This simple method for integrating MWCNTs and biocompatible chitosan into a homogeneous dispersion may have great potential application in biotechnology, such as preparing composite materials for medicine, bio-fiber, biosensor, antibacterial coating, and cell cultivation., (Copyright © 2011 Elsevier B.V. All rights reserved.)

In this work, a great synergistic effect of 2D clay platelets and 1D carbon nanotubes (CNTs) on reinforcing chitosan matrix has been observed for the first time. With incorporation of 3 wt % clay and 0.4 wt % CNTs, the tensile strength and Young's modulus of the nanocomposites are significantly improved by about 171 and 124%, respectively, compared with neat chitosan. This could be understood as due to the formation of much jammed fillers network with 1D CNTs and 2D clay platelets combined together, as indicated by rheological measurement. Our work demonstrates a good example for the preparation of high performance polymer nanocomposites by using nanofillers of different dimension together.

Covalent functionalization of shortened multiwalled carbon nanotubes (MWNTs) with a natural low molecular weight chitosan (LMCS) was accomplished by a nucleophilic substitution reaction. Amino and primary hydroxyl groups of the LMCS contributed mainly to the formation of MWNT-LMCS conjugates. The LMCS content in the MWNT-LMCS is approximately 58 wt %, and approximately four molecular chains of the LMCS are attached to 1000 carbon atoms of the nanotube sidewalls. Most interestingly, the amorphous packing structure of the LMCS changed dramatically when it attached to the MWNTs. The MWNTs might induce the crystalline character of the LMCS. As a novel derivative of MWNTs, the MWNT-LMCS is soluble in dimethylformamide, dimethyl acetamide, dimethylsulfoxide, and acetic acid aqueous solution. The confirmation of the chitosan-based covalent functionalization route might lead to further studies aiming for potential applications in catalysis and environmental protection.

Abstract: In this work, the effects of MWNTs content on water transport behaviors and tensile properties of prepared chitosan porous membranes were investigated. In the case of chitosan membrane using low molecular weight PEG6000 as a porogen, a percolation-like behavior of water transport rate was observed for the first time in composite membranes with a critical MWNTs content (5wt%). The water flux of composite membrane with 10wt% MWNTs (128.1L/m2 h) is 4.6 times that of neat one (27.6L/m2 h). This could be understood as due to the formation of MWNTs network located among the pore network of chitosan membrane at high MWNTs content, where the hollow nanochannel of MWNTs and their interspaces could provide a new transport channel for water. In contrary, when high molecular weight PEG10000 is used as the porogen, a decreased water flux of the prepared composite membrane is found with increase of MWNTs content. In this case, a strong compatibilizing effect of MWNTs on chitosan/PEG10000 blends is observed, resulting in a decreased pore size and poor water flux of the membranes. Furthermore, a greatly improved tensile strength of chitosan porous membranes has been achieved by adding MWNTs, no matter which molecular weight PEG is used as porogen. Our work provides a novel way to improve water flux and/or control the pore size of polymer porous membranes by using MWNTs. [Copyright &y& Elsevier]

Abstract: In this work, the chitosan ternary nanocomposites with two-dimensional (2D) clay platelets and one-dimensional (1D) CNTs have been successfully prepared by a simple solution-intercalation/mixing method in acid media. It was found that the thermal degradation temperature of chitosan (at 50% weight loss) could be only improved in about 20–30°C by adding 3wt% either clay or CNTs, however, almost 80°C increase of degradation temperature could be achieved by adding 2wt% clay and 1wt% CNTs together. Dynamic mechanical measurement demonstrated an obviously improved storage modulus for chitosan/clay–CNTs than that for the corresponding binary chitosan/clay or chitosan/CNT nanocomposites with the same total filler content (3wt%). For the solvent vapor permeation properties, a largely improved benzene vapor barrier property was observed only in chitosan/clay–CNT ternary nanocomposites and depended on the ratio of clay to CNTs. XRD, SEM and TEM results showed that both clay and CNTs could be well dispersed in the ternary nanocomposites with the nanotubes located around the clay platelets. FTIR showed an improved interaction between the fillers and chitosan by using both clay and CNTs. A much enhanced solid-like behavior was observed in the ternary nanocomposites, compared with the corresponding binary nanocomposites with the same total filler content, as indicated by rheological measurement. The unique synergistic effect of two-dimensional (2D) clay platelets and one-dimensional (1D) CNTs on the property enhancement could be tentatively understood as due to a formation of much jammed filler network with 1D CNTs and 2D clay platelets combined together. Our work demonstrates a good example for the preparation of high performance polymer nanocomposites by using nanofillers with different dimensions together. [Copyright &y& Elsevier]

Abstract: Bioactive membranes for guided tissue regeneration would be of value for periodontal therapy. Chitosan-multiwall carbon nanotube (CS-MWNT) composites were treated to deposit nanoscopic apatite for MWNT proportions of 0–4mass%. Fourier-transform infrared spectroscopy, scanning electron microscopy, energy-dispersive X-ray analysis, and X-ray diffraction were used for characterization. Apatite was formed on the CS-MWNT composites at low MWNT concentrations, but the dispersion of the MWNT affects the crystallite size and the Ca/P molar ratio of the composite. The smallest crystallite size was 9nm at 1mass% MWNT. [Copyright &y& Elsevier]

Abstract Here, we report a dual-use surface-enhanced Raman scattering (SERS) substrate based on a flexible three-dimensional (3D) chitosan foam, onto which silver nanoparticles (Ag NPs) are firmly immobilized through amino groups from chitosan chains. The SERS substrate can actively collect analytes either on solid surface by swabbing or in solution by adsorption. The compressible characteristic of chitosan foam enables easy removal of solvent through gentle pressing, which can achieve fast pre-concentrating of analytes before measurements. In addition, the substrate is shape adaptable and thus is suitable for sampling contaminants on solid surfaces. The SERS substrates exhibit acceptable reproducibility (16.4% in relative standard deviation). Furthermore, it detects Raman probe Nile Blue A down to 5 pg by swabbing solid surface and Rhodamine 6G down to 10 ppb by adsorbing analyte in the solution. Three pesticide samples (triazophos, methidathion, and isocarbophos) can also be detected down to μg level with the substrate. It is believed that such a versatile SERS substrate may find great opportunity in realistic sensing applications. Graphical abstract A 3-D chitosan based dual use SERS substrate has been proposed for the direct sampling and sensing of analytes from surface and solution. fx1 Highlights • A SERS substrate based on Ag NPs loaded 3-D chitosan foam has been developed. • The SERS substrate exhibits high sensitivity and commendable reproducibility. • The substrate can directly collect analytes on solid surface as well as in solution. • Solvent can be expelled from the substrate through squeezing for quickly pre-concentrating analytes. [ABSTRACT FROM AUTHOR]