Formation and Evolution of sp2 Hybrid Conjugate Structure of Polyacrylonitrile Precursor during Stabilization

The generated sp2 hybrid conjugate structure of a C atom, which resulted from the chemical reaction affected by temperature and time, is an effective six-membered ring planar structure of the final carbon fiber. This kind of hybrid conjugate structure determined the formation of the final structure and mechanical properties of carbon fiber. In this paper, the formation and evolution of sp2 hybrid conjugated structures of PAN precursor during thermal stabilization were investigated by Raman, UV-vis and 13C-NMR methods. The results indicated that with the increase of stabilization temperature, the degree of the sp2 hybrid conjugated structure of stabilized PAN fiber increases “linearly”, while the content of the sp2 hybrid carbon atoms increases with “S-type”. The final sp2 hybrid conjugated ring structure is mainly composed of single-ring, double-ring, triple-ring, and double-bond structures. Compared with the time factor, the temperature effect plays a decisive role in the formation of the sp2 hybrid conjugate structure.

All-inorganic perovskite quantum dots-based electrospun polyacrylonitrile fiber for ultra-sensitive trace-recording

All-inorganic dual-phase CsPbBr3-Cs4PbBr6 quantum dots (CPB QDs)-based polyacrylonitrile (PAN) fiber synthesized by supersaturated recrystallization and electrospinning technique possesses characteristics of homogeneous morphology, high crystallinity and solution sensitivity. Under 365 nm laser excitation, CPB@PAN fiber exhibits surprising trace-recording capability attributing to the splash-enhanced fluorescence (FL) performance with a narrow-band emission at 477-515 nm. In the process of ethanol-anhydrous (EA) and water splashing, the CPB@PAN fiber presents conspicuous blue and green emission when contacting with EA and water, and maintains intense blue and green FL for more than 4 months. These experimental and theoretical findings provide a facile technology for the development of biological protection display, biotic detection and moisture-proof forewarning based on the trace-recording performance of CPB@PAN fiber.

Preparation and characterization of new red luminescent fibers based on a multilayer structure

Composite red luminescent material SMED/LCA (Sr2MgSi2O7:Eu2+,Dy3+/light conversion agent) is a phosphor with long afterglow, which was prepared by LCA and SMED at a certain mass ratio. It has excellent characteristics, such as high lightness and emitting red light, but poor stability properties because LCA falls off easily from the surface of SMED. Here, SiO2 (Al2O3 or MgF2) was coated on the surface of SMED/LCA through the heterogeneous deposition method to prepare a stable composite phosphor, adding coated phosphor into a polyacrylonitrile (PAN) fiber-forming polymer and wet spinning to form SMED/LCA-PAN (composite red light-emitting fiber). The surface element distribution, phase structure and luminescence properties of SMED/LCA-PAN were characterized. The results show that SiO2 (Al2O3 or MgF2) is successfully coated on the surface of the material, and the coating has no effect on the phase of SMED in the fibers. The intensity red/blue ratio (Int.600 nm versus Int.470 nm) of coated SMED/LCA fiber in the afterglow emission spectrum increases by about 1.9 times; the increase in energy conversion efficiency indicates the enhancement of the red light effect. In addition, the afterglow initial brightness is up to 0.148 cd/m2 after 15 min of ultraviolet light excitation, and the luminous fiber still has high afterglow brightness.

In Situ Synthesis of Silver Nanoparticles on Amino-Grafted Polyacrylonitrile Fiber and Its Antibacterial Activity

In this study, amino hyperbranched polymers (HBP)-grafted polyacrylonitrile (PAN) fiber was prepared through an amidation reaction in an autoclave. The prepared PAN-G-HBP fiber can complex Ag+ through amino groups of amino HBP, and in a hot steaming condition, Ag+ can be converted to Ag0 through the reducibility of HBP. PAN-G-HBP and Ag nanoparticles (NPs)-coated fibers were then characterized through FTIR, UV–VIS DRS, FE-SEM, EDS, XPS and antibacterial measurement. FTIR results confirmed HBP was grafted on the surface of PAN fiber. FE-SEM showed that after grafting with HBP, the average diameter of PAN fibers was amplified. EDS, XPS, and UV–VIS DRS method indicated that under hot steaming condition and with the reducibility of HBP, Ag NPs uniform coating on the PAN-G-HBP. Ag NPs-coated fibers exhibits excellent antibacterial property against Escherichia coli and Staphylococcus aureus. Even under 20 times home washing conditions, the antibacterial reduction of Ag NPs-coated PAN fiber can achieved more than 98.94%.