Hybrid Carbon Silica Nanofibers through Sol–Gel Electrospinning

Abstract

A controlled sol-gel synthesis incorporated with electrospinning is employed to produce polyacrylonitrile-silica (PAN-silica) fibers. Hybrid fibers are obtained with varying amounts of silica precursor (TEOS in DMF catalyzed by HCl) and PAN. Solution viscosity, conductivity, and surface tension are found to relate strongly to the electrospinnability of PAN-silica solutions. TGA and DSC analyses of the hybrids indicate strong intermolecular interactions, possibly between the -OH group of silica and -CN of PAN. Thermal stabilization of the hybrids at 280 °C followed by carbonization at 800 °C transforms fibers to carbon-silica hybrid nanofibers with smooth morphology and diameter ranging from 400 to 700 nm. FTIR analysis of the fibers confirms the presence of silica in the as-spun as well as the carbonized material, where the extent of carbonization is also estimated by confirming the presence of -C═C and -C═O peaks in the carbonized hybrids. The graphitic character of the carbon-silica fibers is confirmed through Raman studies, and the role of silica in the disorder of the carbon structure is discussed.

Cellulose Silica Hybrid Nanofiber Aerogels: From Sol–Gel Electrospun Nanofibers to Multifunctional Aerogels

“…Energy dispersive X‐ray (EDX) spectrum in Figure S2F (Supporting Information) also shows the existence of silica in the hybrid nanofibers with a silicon content of 5.8 wt%. This weight percent is lower than the theoretical weight percent of 11–12% for silica in the hybrid fibers indirectly measured through % content of TEOS in the electrospinning mixture, and also from TGA measurements (discussed later in Section . ); however, our results are internally consistent as 52 wt% of silica is oxygen and EDX only provides information on elemental silicon and oxygen in the fibers.…”

“…Our rationale for using CDA is its origin as a biopolymer and its ease of electrospinnability, while silica, being the inorganic phase, is capable of improving thermal and mechanical stability of the hybrid nanofibers. Instead of electrospinning silica nanoparticles with CDA or subsequent mixing of silica fibers with CDA, we blend the silica precursor mixture with the CDA solution and let the system undergo sol–gel processing during the course of electrospinning . The entire process is schematically depicted in Figure , in which we surmise that sol–gel electrospinning of CDA and silica precursor will result in homogeneous distribution and intimate mixing of silica and CDA in the nanofibers to generate a robust and functional 3D structure.…”

“…Instead of electrospinning silica nanoparticles with CDA or subsequent mixing of silica fibers with CDA, we blend the silica precursor mixture with the CDA solution and let the system undergo sol–gel processing during the course of electrospinning . The entire process is schematically depicted in Figure , in which we surmise that sol–gel electrospinning of CDA and silica precursor will result in homogeneous distribution and intimate mixing of silica and CDA in the nanofibers to generate a robust and functional 3D structure. After high speed homogenization followed by freeze casting the dispersion of the short nanofibers in a nonsolvent (Figure ), we freeze dry the solvent to produce ultralight, highly porous nanofiber aerogels.…”

In Situ Silication of Polymer Nanofibers to Engineer Multi‐Biofunctional Composites

“…Here, the silica precursor solutions are prepared by sol‐gel method and aged for different times before electrospinning with or without mixing with binders. Others have reported the fabrication of chemically stable nanofibers resulting from the interactions between silanol groups of the silica precursor gel and the chemical groups of polymers . In all the reported studies, hydrophilic polymers were mixed with silica precursors prepared by conventional sol‐gel methods having high water content to prepare silica loaded nanofibers.…”

Electrospinning Synthesis and Photoluminescence Properties of One-Dimensional SiO<sub>2</sub>:Tb<sup>3+</sup> Nanofibers and Nanobelts

“…Then PVP was added to assist spinning by tuning the viscoelastic properties of silica sol-gel through the hydrogen bond between the OH groups on the surface of silica sol and the carbonyl groups of the PVP [16]. After stirring for several hours, all PVP were dissolved and connected around the silica sol molecules.…”