Enhancing security authentication of documents using lanthanide aluminate-encapsulated alumina electrospun nanofibrous membrane

Photoresponsive inks have been a popular authentication method to enhance the authentication efficiency. However, recent studies have revealed that photoresponsive inks have several critical drawbacks, including high cost and low durability. Herein, nanoparticles of lanthanide aluminate (NLA; 2–6 nm) were encapsulated in electrospun alumina (ALU) nanofibers. Spinning solutions of polyvinylpyrrolidone/anhydrous aluminum chloride (PVP/AlCl₃) were prepared by the sol–gel technique. The electrospinning and calcination technology were applied to produce alumina nanofibers with diameters of 100–155 nm. Durability and photostability can be guaranteed by encapsulating inorganic photochromic agents in authentication hosting materials. As a result, the NLA-encapsulated alumina (NLA@ALU) nanofibers displayed high reversibility and photostability. When several contents of NLA were applied, different NLA@ALU nanofibers with distinctive emission characteristics were produced. The NLA@ALU nanofibers displayed transparency in the white light and a green emission in the ultraviolet light. Various analytical tools were used to examine the morphology of the photochromic films. The tensile properties of the nanofibrous membrane-coated papers were investigated. The excitation intensity was monitored at 365 nm to indicate a transparent appearance, whereas the emission intensity was monitored at 517 nm to designate a greenish color. The developed alumina nanofibrous membranes can be characterized as an effective tactic against the forgery and counterfeiting of valuable documents.