Abstract
The presented study focuses on photoluminescent pigments applied on cotton fabric by a screen-printed procedure using polydimethylsiloxane (PDMS) as a binder. Microscopic data depicts irregular shapes and relatively wide size distribution (3–80 µm) of pigments. Regarding composition, the Energy-Dispersive X-ray (EDX) and Fourier Transform Infrared (FTIR) spectroscopy data complement findings suggesting the presence of Eu-doped strontium aluminate in the yellow-green, calcium aluminate in the violet pigment, and metal oxides in the blue pigment. The optical properties of pigment-enriched PDMS-coated cotton fabric were assessed and reflectance intensity was found to be concentration-dependent only in the blue pigment. The luminescence decay data show that luminescence intensity decreased with the reduction of pigment concentration in the following order, yellow-green > blue > violet pigments. Relying on absorption and emission data of powdered pigments, the confocal microscopy enables visualization of the pigments’ distribution within a 3D image projection. This identifies the most homogeneous distribution in the case of the blue pigment, as well as the presence of a continuous fluorescing signal in the z projection when 5% pigment was used. This was, for the first time, presented as a powerful tool for non-destructive visualization of photoluminescent pigments’ spatial distribution when printed on textile (cotton) fabric. Finally, the photoluminescent PDMS coating demonstrates high washing and abrasion resistance, contributing to overall functionality of printed cotton fabrics when commercial types of pigments are applied.
Highlights
Pigments are a special type of water insoluble, organic and inorganic, colouring material [1], used for colouration of textiles, as well as metal, wood, stone, etc
Photoluminescent pigments are a subtype of textile pigments, and some could be used in creating very versatile, high-resolution “glow in the dark” patterns on textiles [2], as an alternative to light-emitting diodes (LEDs), electro-luminescent wires and optical fibres for designing light-emitting fabrics, being widely applicable as functional textiles [3], for decoration [4], military facilities, communication and transportation, fire emergency systems [5], etc
The size and shape of pigments were identified as factors influencing light absorption and emission intensity; a major difference was expected from the presence of particles below 0.5 μm [22], which, according to microscopy data, do not dominate in any of the pigments used
Summary
Pigments are a special type of water insoluble, organic and inorganic, colouring material [1], used for colouration of textiles, as well as metal, wood, stone, etc. In contrast to the sulfide-based phosphorus, Ca, Ba and Sr-based aluminate phosphorus possess safer, chemically stable, very bright and long-afterglow photoluminescence, without any harmful radiation As inorganic materials, they overcome the issues related to organic pigments, such as poor photo- and thermal stability, gradual degradation, as well as poor washing and light colour fastness [11]. Techniques used for complementary assessment of pigments’ size and pattern distribution based on an insintric fluorescing property, when printed on fabric (i.e., in situ), are rather limited. When commercial pigments with unknown composition and properties (particles’ size and their distribution, excitation wavelength, emission time, etc.) are employed, together with additives (binders, brighteners), the complexity of pigments’ evaluation increases exponentially. Confocal microscopy is already used for micro [19,20] autofluorescent pigments’ assessment [21], while assessment within textile fabrics has not yet been reported
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