Photoluminescent electrospun submicron fibers of hybrid organosiloxane and derived silica

Abstract

Silica fibers are of technological significance in view of their applications in sensing, photocatalysis, filtration, biological scaffolds, photoluminescence, composites, etc. A combination of electrospinning and sol-gel technique has been employed to synthesize inorganic or ceramic sub-micron fibers starting from a novel oligomeric pre-ceramic precursor, Poly(methylhydrosiloxane) (PMHS). The composite fibers were calcined at temperatures in the range of 550 uC to 1400 uC to obtain slica fibers. The electrospun preceramic fibers and derived silica sub-micron fibers were characterized by FESEM, TEM, XRD, Raman spectroscopy and FTIR. Calcination transformed the smooth pre-ceramic fibers to compact silica fibers that consist of nano-sized silica particles. Calcinations at lower temperatures yielded more amorphous silica fibers, but calcination at 1400 uC yielded a polymorph of crystalline silica, a-cristobalite. Building up of an ordered Si-O network with increased temperature was verified by Infra-Red and Raman Spectroscopy.Photoluminescence (PL) study of the electrospun fibers showed their potential as blue, green and red light emitters at room temperature at different excitation wavelengths, and a blue/violet emission with the UV excitation not seen previously. Although calcination of PMHS fibers decreased PL intensity, a close correspondence in both the emission and excitation PL spectra along with the PL life times of differently calcined fibers is probably owing to the presence of similar defect centers. Tuning of PL should allow potential applications in optoelectronics, medical nanoprobes and bio-labeling and sensing.

Preparation and Structural Characterization of Sol-Gel-Derived Silver Silica Nanocomposite Powders

“…However, a particular attention in FTIR analysis was the appearance of new peak at 620 cm -1 in the spectra of powder annealed at 1000°C and the peaks at 1100cm -1 , 792cm -1 and 490 cm -1 become narrower. This behavior is related to cristobalite phase of silica 23 , which proves that crystallization of silica occurs at 1000 °C in the silver silica nanocomposites. This obsevation is completely identical with XRD data.…”

“…It can be seen that there is a remarkable change in the spectral features between samples heated at 800 °C and 1000 °C. In the top spectrum, the appearance of the most intense peaks centered at 230cm -1 , 416cm -1 and the least significant at 784 cm -1 can be interpreted as signatures of the SiO 2 cristobalite structure 23 . This observation confirms clearly that the phase transformation of silica occurs at 1000 °C.…”

Mesoporous Titanium Dioxide Nanofibers with a Significantly Enhanced Photocatalytic Activity

“…In this context, a detailed investigation of the photo‐oxidation reaction mechanism and the kinetics of the decomposition of a representative VOC gas on TiO 2 nanofiber surfaces is perceived as an important step forward to fight air pollution. Notably, the fibrous TiO 2 materials used in previous studies were produced primarily by the electrospinning technique with diameters that ranged from a few tens of nanometers to a few micrometers . However, lower production rates and high voltage requirements limit the scope of the electrospinning process to meet the demands of moderate to large quantities of appropriate TiO 2 nanofibers.…”

“…Notably,t he fibrousT iO 2 materialsu sed in previouss tudies were produced primarily by the electrospinning technique with diameters that rangedf rom af ew tens of nanometers to af ew micrometers. [27,30,31] However, lower productionr ates and high voltage requirements limit the scope of the electrospinning process to meet the demands of moderate to large quantities of appropriate TiO 2 nanofibers. The limitations of the lowr ate can be overcome by am ethod of forced spinning.…”

Effect of the Degree of Inversion on the Photoelectrochemical Activity of Spinel ZnFe2O4

“…The electronic structure was studied by means of time-averaged and transient room-temperature photoluminescence spectroscopy. It is well known that the photoluminescence spectrum of a material depends on its particle size, crystallinity, and the presence of point defects [21,22]. Therefore, the crystallinity and crystallite size homogeneity of the synthesized ZFO pellets is of utmost importance in order to access meaningful information concerning the effect of the degree of inversion on the photoluminescence properties.…”