Contents lists available at ScienceDirect Ceramics International journal homepage: www.elsevier.com/locate/ceramint Ethylene glycol-assisted ultrafast synthesis and luminescent properties of novel multifunctional EuSr 2 F 7 and TbSr 2 F 7 nanostructures for WLEDs, displays and anti-counterfeiting Yongbin Hua a , Weiguang Ran b , Hoe Chul Jeong a , Yong Hun Song a , Eun Yeong Park a , Jin Hyeong Yoon a , Jae Su Yu a,∗ a Department of Electronic Engineering, Kyung Hee University, Yongin-si, Gyeonggi-do, 17104, Republic of Korea b Department of Chemistry and Chemical Engineering, Qufu Normal University, Qufu, 273165, PR China ARTICLE INFO Keywords: Nanostructures FEDs WLEDs Flexible display flms Anti-counterfeiting ABSTRACT In this paper, novel EuSr 2 F 7 and TbSr 2 F 7 nanostructures were successfully synthesized via an ultrafast wet- chemical route at room temperature. The elemental compositions, morphology, luminescent behaviors, thermal stability, decay curves and quantum yields of the as-prepared samples were investigated. The fabricated white light-emitting diodes (WLEDs) exhibited excellent color rendering index and correlated color temperature va- lues. The security inks and soft polydimethylsiloxane flms were prepared for potential anti-counterfeiting and fexible display applications. Eventually, under low accelerating voltage and flament current, the as-prepared samples showed strong cathodoluminescence emission intensity. The above results suggest that the novel EuSr 2 F 7 and TbSr 2 F 7 nanostructures with outstanding luminescent performances could be promising for feld- emission displays, WLEDs, fexible display flms, and anti-counterfeiting applications. 1. Introduction Trivalent rare-earth (RE) ions-based inorganic materials with na- nostructures have captured huge attention due to their stable crystal structure and been widely used in solid-state lighting, white light generation, optical heaters, feld-emission displays (FEDs), fexible display flms, solar cells, latent fngerprint detection, optical tempera- ture sensors, security inks, and drug delivery [1–9]. Especially, the fuoride nanomaterials with excellent advantages of high photo- chemical stability and low phonon energy have been promised for high color rendering index (CRI) of white light-emitting diodes (WLEDs), outstanding sensitivity of optical temperature sensors and, some bio- logical applications [10–13]. The RE ions-activated luminescent materials can emit multicolor emissions originating from the intra 4f-4f and inter 5d-4f electronic transitions and energy transfer processes [14]. Currently, RE ions-ac- tivated fuoride nanomaterials have been promised for solid-state lighting [15,16]. WLEDs, as a next-generation solid-state lighting source with outstanding performance such as good safety, lower energy consumption, and longer service life compared to conventional in- candescent lamps, have gained much attention from researchers [17,18]. Generally, two common ways have been used to fabricate WLEDs. The frst approach is the yellow-emitting phosphors (YAG:Ce 3+ ) coupled with the blue-chips. However, this is not suitable to become a white light source for some certain architectures owing to the lack of red-emitting phosphors, resulting in low luminous ef- ciency, low CRI, high correlated color temperature (CCT), and some others drawbacks. The second way is achieved by the mean of com- bining the near-ultraviolet (NUV) chip with red, green, and blue (RGB)- emitting phosphors as reported in the literature [19,20]. On the other hand, untrained consumers are often difcult to dis- tinguish the original products. Thus, most of them would be easily cheated by some counterfeit products in our daily life. Indeed, anti- counterfeiting technology is urgent and signifcant against a rapidly growing counterfeit market. According to previous reports, bar-coding and water-marking to make the anti-fake label as traditional methods are used, but both the techniques are poor in security and easy to be duplicated [8]. Fortunately, several novel anti-counterfeit technologies have been developed using carbon dots and quantum dots, and further many people pay more attention to the RE ions-activated phosphors with nanoparticles for anti-counterfeiting because of their simple op- eration, high security, and good stability [21–25]. The soft polydimethylsiloxane (PDMS) flms with prominently stable and all-purpose properties have widely used in nanogenerators, https://doi.org/10.1016/j.ceramint.2019.12.135 Received 30 October 2019; Received in revised form 13 December 2019; Accepted 13 December 2019 ∗ Corresponding author. E-mail address: jsyu@khu.ac.kr (J.S. Yu). Ceramics International 46 (2020) 8891–8902 Available online 15 December 2019 0272-8842/ © 2019 Elsevier Ltd and Techna Group S.r.l. All rights reserved. T