[INVITED] Luminescent QR codes for smart labelling and sensing. (May 2018)

• Record Type: Journal Article
• Authors: Ramalho, João F.C.B.; António, L.C.F.; Correia, S.F.H.; Fu, L.S.; Pinho, A.S.; Brites, C.D.S.; Carlos, L.D.; André, P.S.; Ferreira, R.A.S.
• Is Part Of: Optics & laser technology. Volume 101(2018)
• Page Start: 304
• Page End: 311
• Publication Date: 2018-05
• Subjects: QR codes -- Colour multiplexing -- Organic-inorganic hybrids -- Lanthanide ions -- Temperature sensing; Optics -- Periodicals; Lasers -- Periodicals; Electronic journals; 621.366
• DOI: 10.1016/j.optlastec.2017.11.023
• Languages: English
• ISSNs: 0030-3992

Abstract

Highlights: Implementation of colour multiplexing strategy to increase the QR codes information capacity. Green-emitting luminescent QR code based on an organic-inorganic hybrid doped with Tb 3+ ions. Application of a maximum likelihood criteria guaranties the quality of the demultiplexed QR codes. The luminescent QR codes emission tuning envisage the possibility to sense temperature. Abstract: QR (Quick Response) codes are two-dimensional barcodes composed of special geometric patterns of black modules in a white square background that can encode different types of information with high density and robustness, correct errors and physical damages, thus keeping the stored information protected. Recently, these codes have gained increased attention as they offer a simple physical tool for quick access to Web sites for advertising and social interaction. Challenges encompass the increase of the storage capacity limit, even though they can store approximately 350 times more information than common barcodes, and encode different types of characters (e.g., numeric, alphanumeric, kanji and kana). In this work, we fabricate luminescent QR codes based on a poly(methyl methacrylate) substrate coated with organic-inorganic hybrid materials doped with trivalent terbium (Tb 3+ ) and europium (Eu 3+ ) ions, demonstrating the increase of storage capacity per unit area by a factor of two by using the colour multiplexing, when compared to conventional QR codes. A novel methodology to decode the multiplexed QR codes is developed based on a colour separation threshold where a decision level is calculated through a maximum-likelihood criteria to minimize the error probability of the demultiplexed modules, maximizing the foreseen total storage capacity. Moreover, the thermal dependence of the emission colour coordinates of the Eu 3+ /Tb 3+ -based hybrids enables the simultaneously QR code colour-multiplexing and may be used to sense temperature (reproducibility higher than 93%), opening new fields of applications for QR codes as smart labels for sensing.