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 °C to 1400 °C to obtain slica fibers. The electrospun pre-ceramic 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 °C yielded a polymorph of crystalline silica, α-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.