Advanced Powder Technology , August 2022, 103775,Txet Full

Hongxia Peng【彭红霞】a , Liyi Liu  a, Jiaxi He a, Jiahao Pi , Jianzhen Wu c , Xiangni Wang a , Xingping Huang a ,Xiaohe Liu* c, Fabiao Yu【于法标】*b

a Hunan Provincial Key Laboratory of Fine Ceramics and Powder Materials, Hunan University of Humanities, Science and Technology, Lou’di, Hunan 417000, PR China

b Laboratory of Neurology, the First Affiliated Hospital of Hainan Medical University, Key Laboratory of Hainan Functional Materials and Molecular Imaging, Key Laboratory of Emerg-ency and Trauma, Ministry of Education, Hainan Medical University, Haikou 571199, China

c State Key Laboratory of Powder Metallurgy and School of Materials Science and Engineering, Central South University, Changsha, Hunan 417000, PR China

https://doi.org/10.1016/j.apt.2022.103775

Abstract：
A novel halloysite@YF3: Ce3+, Tb3+ anocomposite with strong luminescent properties was designed and synthesized by a facile direct precipitation strategy. Owing to the halloysite as a support, it can significantly prevent the aggregation of YF3:Ce3+,Tb3+ and the distribution of YF3:Ce3+,Tb3+ on halloysite was highly uniform. Importantly, due to the unique surface-interface-dielectric multiple confinement (SIDMC) effects, the as-harvested halloysite@YF3:Ce3+,Tb3+ nanocomposite exhibited excellent lumines cent performance. Compared with YF3:Ce3+,Tb3+, the luminescence intensity of halloysite@YF3:Ce3+, Tb3+ nanocomposite is significantly enhanced by about 6 times under 255 nm excitation. However, the fluorescence lifetime of halloysite@YF3:Ce3+,Tb3+ nanocomposite (7.21 ms) is shorter than that of YF3: Ce3+,Tb3+ nanoparticles (8.34 ms). This finding indicated that halloysite can change the luminescent prop erties of YF3:Ce3+,Tb3+ nanoparticles through an SIDMC effect. The combination of halloysite and YF3:Ce3+, Tb3+ nanoparticles not only endowed halloysite with special properties, and effectively tuned the lumi nescent properties of YF3:Ce3+,Tb3+ nanoparticles, thereby improving the utility of halloysite and YF3: Ce3+,Tb3+ nanoparticles. The research supplies an insight on the development of natural mineral-based luminescent materials, and hopefully it could promote them application in many fields.

Keywords:Halloysite YF3:Ce3+,Tb3+ Luminescent property Surface-interface-dielectric multiple confinement effect

Fig. 1. Synthesis procedure and schematic illustration of luminescence enhancement mechanism of halloysite@YF3:Ce3+,Tb3+ nanocomposite.

Fig. 2. XRD patterns of halloysite, YF3:Ce3+,Tb3+ and halloysite@YF3:Ce3+,Tb3+ nanocomposite.

Fig. 3. SEM of halloysite (a, c) and halloysite@YF3:Ce3+,Tb3+ (b, d) nanocomposite.

Fig. 4. (a) TEM image and (inset) corresponding particle size distribution histogram, (b) HRTEM image, and (c) SAED pattern of halloysite@YF3:Ce3+,Tb3+ nanocomposite.

Fig. 5. (a) TEM images of halloysite@YF3:Ce3+,Tb3+ nanocomposite; (b–h) energy dispersive X-ray (EDX) mapping of halloysite@YF3:Ce3+,Tb3+ nanocomposite.

Fig. 6. Infrared spectrum of halloysite, YF3:Ce3+, Tb3+ and halloysite@YF3:Ce3+,Tb3+ nanocomposite.

Fig. 7. XPS spectra (a) XPS survey spectra of halloysite, YF3:Ce3+,Tb3+ and halloysite@YF3:Ce3+,Tb3+ nanocomposite and High-resolution O 1 s(b), Al 2p(c), Si 2p(d), Y 3d (e), F 1 s(f), Ce 3d(g), Tb 3d(h).

Fig. 8. (A) UV–vis spectra of samples; (B, C, D) DRS spectra of samples with the corresponding plots of [F(R∞)hv]2 versus hv.

Fig. 9. Urbach tail energy fitting of YF3:Ce3+,Tb3+ and halloysite@YF3:Ce3+,Tb3+ nanocomposite.

Fig. 10. Dielectric performance of YF3:Ce3+,Tb3+ and halloysite@YF3:Ce3+,Tb3+: (A) dielectric constant and (B) tan δ; (C) and (D) Excitation and emission spectra of halloysite@YF3:Ce3+, Tb3+; YF3:Ce3+,Tb3+ and halloysite.

Fig. 11. Fluorescent decay curves of 5D4 → 7F5 (552 nm) for Tb3+.

A new type of halloysite@YF3:Ce3+,Tb3+ nanocomposite was successfully synthesized with the direct precipitation method.The combination of halloysite and YF3:Ce3+,Tb3+ nanoparticles not only endowed halloysite with new functions but also improved the luminescence properties of YF3:Ce3+,Tb3+ nanoparticles through SIDMC effect because of the heteroepitaxial growth of YF3:Ce3+,Tb3+ nanoparticles on the surface of halloysite. Moreover, the combination of halloysite and YF3:Ce3+,Tb3+ nanoparticles increases the concentration of excitable Ce3+and Tb3+ ions and reduce the surface defects of YF3:Ce3+,Tb3+ nanoparticles. The pre pared novel halloysite@YF3:Ce3+,Tb3+ nanocompos ite have broad application prospects in various fields, such as lighting lamps and displays, and can be used in visualizing orally administered drug delivery carriers. The synthesis strategy has the following merits: high output, a simple reaction device, and mild conditions. This strategy can be used in synthesizing other natural mineral-based luminescent nanocomposites and provides an experimental basis for the development of novel low-cost luminescent materials.