Raspberry-like Nanoheterostructures Comprising Glutathione-Capped Gold Nanoclusters Grown on the Lanthanide Nanoparticle Surface.

Bare lanthanide-doped nanoparticles (LnNPs), in particular, NaYF 4 :Yb 3+ ,Tm 3+ NPs (UC Tm ), have been seeded in situ with gold cations to be used in the subsequent growth of gold nanoclusters (AuNCs) in the presence of glutathione (GSH) to obtain a novel UC Tm @AuNC nanoheterostructure (NHS) with a raspberry-like morphology. UC Tm @AuNC displays unique optical properties (multiple absorption and emission wavelengths). Specifically, upon 350 nm excitation, it exhibits AuNC photoluminescence (PL) (500-1200 nm, λ max 650 nm) and Yb emission (λ max 980 nm); this is the first example of Yb sensitization in a UC Tm @AuNC NHS. Moreover, under 980 nm excitation, it displays (i) upconverting PL of the UC Tm (at the blue, red and NIR-I, ca. 800 nm, regions); (ii) two-photon PL of AuNC; and (iii) down-shifting PL of thulium (around 1470 nm). The occurrence of energy transfer from UC Tm to AuNCs in the UC Tm @AuNC NHS was evidenced by the drastic lengthening of the AuNC PL lifetime (τ PL ) (from few hundred nanoseconds to more than one hundred microseconds). Initial biological assessment of UC Tm @AuNC NHSs in vitro revealed high biocompatibility and bioimaging capabilities upon near-infrared excitation.