Fabrication and luminescent studies of near-spherical phosphor embedded epoxy-resin nanocomposite beads

A facile method for feasible industrial production of long afterglow phosphor nanocomposites, in the form of small beads were developed that continuously emit visible light for >7 h to realize many innovative applications involving hard and soft surfaces. Green emitting SrAl2O4:Eu2+, Dy3+ (SRA) long afterglow phosphor was uniformly dispersed in the epoxy resin (ER) matrix in presence of organic surfactant as hardener to make phosphor-embedded viscous fluid that could then be solidified at room temperature (~25 °C) within few minutes. As ethyl alcohol (solvent) started evaporating, ethylene glycol (surfactant), which is the simplest amongst glycols, started adhering with SRA phosphor particles via van der Waals attraction. The homogeneity of dispersion strongly depends on the shape of SRA phosphor added to ER matrix and confirmed that the near-spherical is the best. The SRA phosphor–ER beads demonstrated an optimum ultraviolet (UV) excitation wavelength at 375 nm and a green-emission peak at 517 nm, where the latter one is due to the transitions from 4f65d1 to 4f7 energy levels of Eu2+ ions. The appearance of SRA phosphor–ER beads in translucent yellow-green color, bright green and green under ambient light, UV (375 nm) irradiation and in dark conditions, respectively was indicated using photoluminescence and colorimetric measurements. The SRA phosphor–ER beads exhibited highly durable, reversible and reproducible afterglow luminescence for longer durations. Photoluminescence, structural, morphological and afterglow properties of the prepared SRA phosphor–ER beads were investigated thoroughly. Moreover, these afterglow beads have several designing and crafting applications such as interior design, glowing toys, ornaments and tracking lights etc.