Production of photochromic nanocomposite film via spray‐coating of rare‐earth strontium aluminate for anti‐counterfeit applications

Abstract

New photochromic film was developed toward the preparation of anti‐counterfeiting documents utilizing inorganic/organic nanocomposite enclosing a photoluminescent inorganic pigment and a polyacrylic binder polymer. To generate a translucent film from pigment/polyacrylic nanocomposite, the phosphorescent strontium aluminum oxide pigment should be well‐dispersed in the solution of the polyacrylic‐based binder without agglomeration. The photochromic nanocomposite was applied efficiently onto commercial cellulose paper documents utilizing the effective and economical spray‐coating technology followed with thermofixation. A homogeneous photochromic film was immobilized onto cellulose paper surface to introduce a transparent film changing to greenish‐yellow upon exposure to ultraviolet light as depicted by CIE coloration measurements. The photochromic effect was monitored at lowest pigment concentration (0.25 wt%). The spray‐coated paper documents exhibit two absorbance bands at 256 and 358 nm, and two fluorescence peaks at 433 and 511 nm. The morphologies of the spray‐coated documents were explored. The spray‐coated paper sheets showed a reversible photochromic effect without fatigue under ultraviolet irradiation. The rheology of the produced photochromic composites as well as the mechanical properties and photostability of the spray‐coated documents were studied.

Preparation of transparent photoluminescence smart window by integration of rare‐earth aluminate nanoparticles into recycled polyethylene waste

“…LdSAO was prepared using a previously published procedure [ 15 ] to produce LdSAO microparticles (12–33 μm). To develop photoluminescent transparent sheets, these LdSAO microparticles were then milled using the top‐down technique to produce LdSAO nanosized particles.…”

“…LdSAO (SrAl 2 O 4 :Eu 2+ ,Dy 3+ ) was prepared using a previously published method (solid-state high temperature), [15,18] in which a combination of SrCO 3 (100 mmol), H 3 BO 3 (20 mmol), Dy 2 O 3 (1 mmol), Al 2 O 3 (200 mmol), and Eu 2 O 3 (2 mmol) was stirred in ethyl alcohol (100%; 450 ml). The suspension was homogenized (25 kHz) for 60 min to guarantee that it had dispersed uniformly.…”

“…During irradiation with light, fluorescent photochromic materials emit light of a certain colour and then revert to their origin state when the illumination source is turned off. [ 15,16 ] Conversely, long‐persistence phosphorescence materials continue to emit light for expanded periods of time when the illumination supply is turned off. [ 17,18 ]…”

“…During irradiation with light, fluorescent photochromic materials emit light of a certain colour and then revert to their origin state when the illumination source is turned off. [15,16] Conversely, long-persistence phosphorescence materials continue to emit light for expanded periods of time when the illumination supply is turned off. [17,18] Nanomaterials can be used to impart polymer composites with unique properties such as transparency, UV light protection, water repellence, electroconductivity, and sensory and antimicrobial activities, making them suitable for a wide range of advanced applications.…”

Synthesis of lanthanide‐doped strontium aluminate nanoparticles encapsulated in polyacrylonitrile nanofibres: photoluminescence properties for anticounterfeiting applications

“…[20] The rare-earth-doped strontium aluminium oxide phosphor is one of the best rare-earth-doped phosphors due to its distinct properties, such as nontoxicity, thermal and photostability, brightness, long-lasting time (>10 h), nonradioactivity, resistant capability to chemicals and recyclability. [21][22][23][24][25] Therefore, the fabrication of UV-stimulated photochromic LSAN-immobilized PAN nanofibrous films is an attractive innovative practice for anticounterfeiting materials with photostability, high durability, low cost, and superhydrophobicity. These characteristics open new horizons to build up more efficient and stable anticounterfeiting materials.…”