Characterization of Pullulan/Chitosan Oligosaccharide/Montmorillonite Nanofibers Prepared by Electrospinning Technique.

Pullulan/Chitosan oligosaccharide (COS)/Montmorillonite (MMT) hybrid nanofibers were electrospun from their aqueous solution using different Pullulan/COS mass ratios and variable amounts of MMT. The effects of Pullulan/COS mass ratios and MMT contents on the morphologies and properties of PulluIan/COS/MMT hybrid nanofibers were investigated. The obtained nanofibers were characterized with field emission-scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), thermo gravimetric analysis (TGA), and tensile strength measurement. The Pullulan/COS mass ratio and MMT contents significantly influence the morphologies and properties of the Pullulan/COS/MMT hybrid nanofibers. Higher Pullulan contents than COS contents forms uniform and bead free nanofibers. The addition of COS to Pullulan improves the thermal stability of Pullulan/COS blend nanofibers. The incorporation of MMT to the Pullulan/COS/MMT hybrid nanofibers increase their fiber diameter, improves their thermal stability and tensile strength. These morphological changes and property enhancement depend on the amount of MMT added. The XRD and TEM results suggest the coexistence of Pullulan, COS and MMT within polymer matrix through intercalation of polymer chain between silicate layers forming well-ordered multiplayer morphology with alternating polymeric and silicate layers.

Characterization of carbon nanotube-cdse hybrid nanomaterials.

MWNT-CdSe hybrid nanomaterials were prepared with carboxylic acid-treated CdSe nanoparticles and amino-functionalized MWNTs. The hybridization of MWNT-CdSe nanomaterials was performed by the formation of covalent bond between MWNT and CdSe. Their covalent bond lengths were varied with changing the linking spacers. Amino-functionalized MWNTs were reacted with CdSe nanoparticles which were functionalized with carboxylic acid groups. Their detailed structures were characterized by FT-IR, XPS, and small angle X-ray scattering. Through small angle X-ray scattering experiments, it was found that the structures of CdSe nanoparticles were not regular, and their sizes were broadly distributed in solution. The longer amino-functionalized MWNTs were thermally decomposed at lower temperature. The photoluminescence (PL) of chemically-linked MWNT-CdSe hybrid nanomaterials were weaker than that of CdSe nanoparticles. In addition, their PL intensities more weakened on the MWNT-CdSe with the longer spacers.

Membrane growth of nanoporous silicates via the self-assembly monolayer.

The self-assembly monolayer (SAM) method was used for membrane fabrication, in which Si wafers were treated separately with N-trimethoxysilylpropyl-n,n,n-tri-n-butylammonium bromide (TMSP-TBA) and N-trimethoxysilylpropyl-n,n,n-trimethylammonium chloride (TMSP-TMA) to form monolayers on the Si surfaces. To grow silicate membranes on the organosilyl-treated Si wafers, a series of silicate sols were prepared with composites of tetraethylorthosilicate (TEOS) and methyltriethoxysilane (MTES) as silicate sources, and tetrapropylammonium bromide (TPABr) was used as an organic template. Their microstructures were investigated in detail by comparing them using SEM and XRD. The use of MTES hindered the formation of microporous channels in the calcined silicate samples. The calcined silicate samples became totally amorphous over 20% loading of MTES. In addition, their structural information was supported by spectroscopic (FT-IR and solid-state 29Si NMR) analyses.

Characterization of attractive interaction-driven carbon nanotube composites with Cd-based nanoparticles.

Multiwalled carbon nanotube (MWNT) composites with cadmium telluride (CdTe) or cadmium selenide (CdSe) nanoparticles were prepared via electrostatic interaction. The MWNTs were modified with carboxylic acid groups. Both the CdTe and CdSe nanoparticles were stabilized with 2-(dimethylamino) ethanethiol hydrochloride to develop positive charges on their surfaces in water. They were characterized in detail via UV-visible spectroscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The energy state of the MWNTs was significantly modified by the electrostatic binding between the nanoparticles and carboxylated MWNTs, resulting in absorption at approximately 250 nm. XPS analysis also proved the electronic redistribution of the nanoparticles and the MWNTs. The binding energies of the elements Cd, Se, and Te were definitely changed by the attractive interaction between the nanoparticles and the MWNTs. The distribution of the CdTe or CdSe nanoparticles and the morphologies of the MWNT composites were deliberately investigated from TEM images and XRD.

Electrospinning Fabrication of Poly(vinyl alcohol)/Coptis chinensis Extract Nanofibers for Antimicrobial Exploits.

Coptis chinensis (CC) is used in conventional Chinese medicine. The main active components of CC are isoquinoline alkaloids, including berberine, coptisine, palmatine, and magnoflorine; all these are known to have several pharmacological properties. Poly(vinyl alcohol) (PVA) is a well-known synthetic biocompatible polymer suitable for a range of pharmaceutical uses; it can be used as a matrix for the incorporation of functional materials and has a wide range of applications in the cosmetics, food, pharmaceutical, and packaging industries. In this study, PVA-based electrospun nanofibers containing CC extract were successfully fabricated. Furthermore, the effects of different CC extract contents on the morphologies, and antimicrobial and antifungal properties of PVA/CC extract nanofibers were investigated. Morphological changes were observed using different molecular weights of PVA. For characterization, field-emission scanning electron microscopy, thermogravimetric analysis, and Fourier transform infrared analysis were performed. The effectiveness of these nanofibers has been demonstrated by evaluating the thermal stability against Staphylococcus aureus, antimicrobial activity against Staphylococcus aureus and Staphylococcus epidermidis, and the antifungal activity against the fungi Aureobasidium pullulans and Penicillium pinophilum. The PVA/CC extract nanofibers were found to have excellent antibacterial and antifungal activity and thermal stability; hence, their use in medicinal sectors is highly recommended.

Synchrotron X-ray scattering study of the mechanism of nanopore generation in nanoporous organosilicate thin films imprinted with a reactive six-armed porogen.

In situ grazing incidence small-angle X-ray scattering analysis was successfully performed during the thermal processing of film blends of polymethylsilsesquioxane (PMSSQ) precursor and triethoxysilyl-terminated six-arm poly(epsilon-caprolactone) (mPCL6) porogen. In addition, thermogravimetric analysis of the films was carried out in a nitrogen atmosphere. These measurements provide important information about the structures of the blend films and of the resulting porous films. In particular, they are used in this paper to establish the mechanism of the formation of imprinted pores within the blend films. During the heating run, the sacrificial thermal degradation of the porogen component commenced at 320 degrees C, generating pores in the resulting cured PMSSQ films. Only very limited porogen aggregation occurred during the blend film formation process (spin-coating and subsequent drying), and these porogen aggregates were of relatively small size and narrow size distribution. The observed restriction of the formation of such porogen aggregates was found to result from the favorable hybridization reaction of the porogen's reactive end groups with the reactive functional groups of the PMSSQ precursor, which competes with aggregation via reaction between the porogen molecules. The average radius (or half-size) of the porogen aggregates was in the range 2.45-3.98 nm, depending on the porogen loading (10-40 wt %). The porogen aggregates retained their size and size distribution until thermal degradation, which resulted in the imprinting of nanopores in the cured PMSSQ films with size and size distribution corresponding to those of the porogen aggregates. The porosities of the resulting nanoporous films were in the range 12.4-41.7%, depending on the initial porogen loading.

X-ray scattering study of thermal nanopore templating in hybrid films of organosilicate precursor and reactive four-armed porogen.

The miscibility and the mechanism for thermal nanopore templating in films prepared from spin-coating and subsequent drying of homogenous solutions of curable polymethylsilsesquioxane dielectric precursor and thermally labile, reactive triethoxysilyl-terminated four-armed poly(epsilon-caprolactone) porogen were investigated in detail by in situ two-dimensional grazing incidence small-angle x-ray scattering analysis. The dielectric precursor and porogen components in the film were fully miscible. On heating, limited aggregations of the porogen, however, took place in only a small temperature range of 100-140 degrees C as a result of phase separation induced by the competition of the curing and hybridization reactions of the dielectric precursor and porogen; higher porogen loading resulted in relatively large porogen aggregates and a greater size distribution. The developed porogen aggregates underwent thermal firing above 300 degrees C without further growth and movement, and ultimately left their individual footprints in the film as spherical nanopores.

Ultralow-k nanoporous organosilicate dielectric films imprinted with dendritic spheres.

Integrated circuits that have improved functionality and speed in a smaller package and that consume less power are desired by the microelectronics industry as well as by end users, to increase device performance and reduce costs. The fabrication of high-performance integrated circuits requires the availability of materials with low or ultralow dielectric constant (low-k: k

Anisotropic thermal expansion behavior of thin films of polymethylsilsesquioxane, a spin-on-glass dielectric for high-performance integrated circuits.

Thin films of poly(methylsilsesquioxane) (PMSSQ) are candidates for use as interdielectric layers in advanced semiconductor devices with multilayer structures. We prepared thin films of PMSSQ with thicknesses in the range 25.0-1151.0 nm by spin-casting its soluble precursor onto Si and GaAs substrates with native oxide layers and then drying and curing the films under a nitrogen atmosphere at temperatures in the range 250-400 degrees C. The out-of-plane thermal expansion coefficient alpha(perpendicular) of each film was measured over the temperature range 25-200 degrees C using spectroscopic ellipsometry and synchrotron X-ray reflectivity, while the in-plane thermal expansion coefficient alpha(parallel) of each film was determined over the temperature range 25-400 degrees C by residual stress analysis. PMSSQ films cured at higher temperatures exhibited reduced thermal expansion, which is attributed to the denser molecular packing and higher degree of cross-linking that arises at higher temperatures. Surprisingly however, all the PMSSQ films were found to exhibit very strong anisotropic thermal expansion; alpha(perpendicular) and alpha(parallel) of the films were in the ranges 140-329 ppm/ degrees C and 12-29 ppm/ degrees C respectively, depending on the curing temperature. This is the first time that cured PMSSQ thin films have been shown to exhibit anisotropic thermal expansion behavior. This anisotropic thermal expansion of the PMSSQ thin films might be due to the anisotropy of cross-link density in the films, which arises because of a combination of factors: the preferential orientation of methyl groups toward the upper film surface and the preferential network formation in the film plane that occurs during curing of the confined film. In addition, the film electron densities were determined using synchrotron X-ray reflectivity measurements and the film biaxial moduli were obtained using residual stress analysis.