Yun-Su Kuk

Herein, we prepared a novel photocatalytic ZnO-TiO₂ loaded carbon nanofibers composites (ZnO-TiO₂-CNFs) via electrospinning technique followed by a hydrothermal process. At first, the electrospun TiO₂ NP-embedded carbon nanofibers (TiO₂-CNFs) were achieved using electrospinning and a carbonization process. Next, the ZnO particles were grown into the TiO₂-CNFs via hydrothermal treatment. The morphology, structure, and chemical compositions were studied using state-of-the-art techniques. The photocatalytic performance of the ZnO-TiO₂-CNFs composite was studied using degrading methylene blue (MB) under UV-light irradiation for three successive cycles. It was noticed that the ZnO-TiO₂-CNFs nanocomposite showed better MB removal properties than that of other formulations, which might be due to the synergistic effects of carbon nanofibers and utilized metal oxides (ZnO and TiO₂). The adsorption characteristic of carbon fibers and matched band potentials of ZnO and TiO₂ combinedly help to boost the overall photocatalytic performance of the ZnO-TiO₂-CNFs composite. The obtained results from this study indicated that it can be an economical and environmentally friendly photocatalyst.

In this work, flexible ternary composites of cobalt-doped cadmium selenide/electrospun carbon nanofibers (Co-CdSe@ECNFs) for photocatalytic applications were fabricated successfully via electrospinning, followed by carbonization. For the fabrication of the proposed photocatalysts, Co-CdSe nanoparticles were grown in situ on the surface of ECNFs during the carbonization of precursor electrospun nanofibers obtained by dispersing Se powder in the electrospinning solution of polyacrylonitrile/N,N-Dimethylformamide (PAN/DMF) containing Cd²⁺ and Co²⁺. The photocatalytic performance of synthesized samples is investigated in the photodegradation of methylene blue (MB) and rhodamine B (RhB) dyes. Experimental results revealed the superior photocatalytic efficiency of Co-CdSe@ECNFs over undoped samples (CdSe@ECNFs) due to the doping effect of cobalt, which is able to capture the photogenerated electrons to prevent electron–hole recombination, thereby improving photocatalytic performance. Moreover, ECNFs could play an important role in enhancing electron transfer and optical absorption of the photocatalyst. This type of fabrication strategy may be a new avenue for the synthesis of other ECNF-based ternary composites.

Heterojunction nanofibers of PAN decorated with sulfate doped Ag₃PO₄ nanoparticles (SO₄²⁻-Ag₃PO₄/PAN electrospun nanofibers) were successfully fabricated by combining simple and versatile electrospinning technique with ion exchange reaction. The novel material possessing good flexibility could exhibit superior antibacterial property over sulfate undoped species (Ag₃PO₄/PAN electrospun nanofibers). FESEM, XRD, FTIR, XPS and DRS were applied to characterize the morphology, phase structure, bonding configuration, elemental composition, and optical properties of the as fabricated samples. FESEM characterization confirmed the successful incorporation of SO₄²⁻-Ag₃PO₄ nanoparticles on PAN electrospun nanofibers. The doping of SO₄²⁻ ions into Ag₃PO₄ crystal lattice by replacing PO₄³⁻ ions can provide sufficient electron-hole separation capability to the SO₄²⁻-Ag₃PO₄/PAN heterojunction to generate reactive oxygen species (ROS) under visible light irradiation and enhances its antibacterial performance. Finally, we hope this work may offer a new paradigm to design and fabricate other types of flexible self-supporting negative-ions-doped heterojunction nanofibers using electrospinning technique for bactericidal applications.

Carbon/carbon (C/C) composites are conventionally manufactured by liquid-phase impregnation (LPI), in which the binder pitches and phenolic resins are impregnated into the composites, and by chemical vapor infiltration (CVI). However, CVI has certain limitations in that expensive gases, such as methane and propane, are used and a long reaction time is required. Therefore, LPI is more widely used, as it employs economical pitches. In this study, the effects of one-step preparation on mechanical properties of C/C composites impregnated with mesophase binder pitches and phenolic resins have been investigated. The C/C composites containing four types of 20 wt.% mesophase binder pitches had differences in softening point (SP) and quinoline insoluble (QI) contents. After conducting trials on mesophase formation using different heat treatment temperatures and times, the best density and mechanical properties of the C/C composites were achieved using the mesophase binder pitches with 170 °C SP. However, when SP 200 °C was used, the density of the C/C composites was not further improved. This is because the binder pitches were not properly impregnated into the composites due to the high viscosity and QI of the binder pitches. Furthermore, the C/C composites fabricated with 20 wt.% pitch 2 exhibited the highest mechanical properties.