Upconversion nanotubes with tunable fluorescence properties based on Gd2 O2 S:Ln3+ (Ln3+  = Yb3+, Er3+) and derivatives for photodynamic therapy

In this study, Gd 2 O 2 S:Ln 3+ (Ln 3+ = Yb 3+ , Er 3+ ) upconversion nanotubes (UCNTs) were synthesised by using Gd(OH) 3 :Ln 3+ (Ln 3+ = Yb 3+ , Er 3+ ) nanotubes as the template. The luminescent and biological properties of Gd 2 O 2 S:Ln 3+ (Ln 3+ = Yb 3+ , Er 3+ ) UCNTs, along with photodynamic therapy (PDT) applications of the Gd 2 O 2 S:8%Yb 3+ , 2%Er 3+ UCNT–Ce6 (chlorin e6) nanocomposites, were systematically studied. The resultant UCNTs showed excellent biocompatibility with human retinal pigment cells (ARPE-19) even after a prolonged incubation time of 72 h, and could be used as luminescent probes. Microscopic imaging revealed that the UCNTs existed mainly in cytoplasm. PDT studies on the Gd 2 O 2 S:8%Yb 3+ , 2%Er 3+ UCNT–Ce6 nanocomposites indicate that the growth of the tumour (cell) could be inhibited dramatically when it was injected (incubated) with Gd 2 O 2 S:8%Yb 3+ , 2%Er 3+ UCNT–Ce6 nanocomposites under the irradiation of 980 nm laser.