Upconversion nanotubes with tunable fluorescence properties based on Gd 2 O 2 S:Ln 3+ (Ln 3+  = Yb 3+ , Er 3+ ) and derivatives for photodynamic therapy

In this study, Gd O S:Ln (Ln = Yb , Er ) upconversion nanotubes (UCNTs) were synthesised by using Gd(OH) :Ln (Ln = Yb , Er ) nanotubes as the template. The luminescent and biological properties of Gd O S:Ln (Ln = Yb , Er ) UCNTs, along with photodynamic therapy (PDT) applications of the Gd O S:8%Yb ,2%Er 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 O S:8%Yb ,2%Er UCNT-Ce6 nanocomposites indicate that the growth of the tumour (cell) could be inhibited dramatically when it was injected (incubated) with Gd O S:8%Yb ,2%Er UCNT-Ce6 nanocomposites under the irradiation of 980 nm laser.