Bright and persistent green and red light-emitting fine fibers: A potential candidate for smart textiles

The properties of smart light-emitting textile/fabric with a persistent afterglow can be beneficial for use in anti-counterfeiting, night surveillance, and security trooping among other potential applications. Keeping this in mind, this work is a step forward in designing bright green and red emitting poly vinyl alcohol (PVA) fine fibers. We first synthesized green emitting Zn2GeO4:Mn2+ (ZGOM) and red emitting ZnGa2O4:Cr3+ (ZGOC) nanoparticles using a hydrothermal process. Field Emission Scanning Electron Microscope (FESEM) images depicted the formation of nanorods and sub-10 nm nanoparticles for ZGOM and ZGOC, respectively. These nanoparticles were mixed in a PVA solution and spun into fiber using the Forcespinning® technology. FESEM images of the fiber samples show the presence of long, bead-free, defect-free, smooth surfaces with the diameters ranging from 200 nm to 1.2 μm depending on selected processing parameters; a fiber system was selected considering fiber output and fiber diameter, the selected system had fibers with average diameter of 900 nm for both ZGOM and ZGOC encapsulated PVA fine fibers (MG-PF and CR-PF). Another favorable property was that the thermal stability of the PVA fine fibers was not affected by the nanoparticles. Both MF-PF and CR-PF fine fibers depicted a bright green and red luminescence, respectively, under UV excitation. The fiber can easily accommodate loading up to 1.0% weight without doing any kind of fluorescence quenching. MG-PF fiber displayed a bright and substantial green persistence luminescence up to 500 s. In the case of CR-PF there is a quenching of trap states and therefore intrinsic red persistence luminescence is not retained beyond 100 s. We believe such green fiber if smartly woven in any kind of textile materials/fabric can be an efficient solution to deal with cloth counterfeiting and night surveillance.