Novel preparation and near-infrared photoluminescence of uniform core-shell silver sulfide nanoparticle@mesoporous silica nanospheres

Abstract

In this paper, we report a facile one-pot route to prepare core-shell Ag₂S@MSN mesoporous silica nanospheres with near-infrared (NIR) photoluminescent properties. The Ag₂S@MSN nanospheres have uniform core-shell structures with single monoclinic α-Ag₂S nanocrystal core (∼17 nm), ordered mesoporous silica shell (the thickness of ∼20 nm), very high surface area (∼909 m² g⁻¹), and uniform pore size (∼2.6 nm). The core-shell Ag₂S@MSN nanospheres show NIR emission at around 1275 nm excited by a 648 nm laser diode, which can be observed in a wide range of concentration (0.2∼3.2 mg mL⁻¹). The stability of the NIR photoluminescence for the core-shell Ag₂S@MSN nanospheres is greatly improved compared to the bare Ag₂S nanocrystals. The NIR emission intensity could be enhanced after the hydrothermal treatment with the increase of crystallinity of the silver sulfide cores. The thickness of mesoporous silica shell could be tuned by adjusting the amount of silica source. Furthermore, the core-shell Ag₂S@MSN nanocomposites with several small Ag₂S nanoparticles in one mesoporous silica shell could also be obtained, which may be a good candidate for bioimaging and biolabeling.