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Gold nanoclusters (AuNCs) with fluorescence in the Near Infrared (NIR) by both one- and two-photon electronic excitation were incorporated in mesoporous silica nanoparticles (MSNs) using a novel one-pot synthesis procedure where the condensation polymerization of alkoxysilane monomers in the presence of the AuNCs and a surfactant produced hybrid MSNs of 49 nm diameter. This method was further developed to prepare 30 nm diameter nanocomposite particles with simultaneous NIR fluorescence and superparamagnetic properties, with a core composed of superparamagnetic manganese (II) ferrite nanoparticles (MnFe2O4) coated with a thin silica layer, and a shell of mesoporous silica decorated with AuNCs. The nanocomposite particles feature NIR-photoluminescence with 0.6% quantum yield and large Stokes shift (290 nm), and superparamagnetic response at 300 K, with a saturation magnetization of 13.4 emu g−1. The conjugation of NIR photoluminescence and superparamagnetic properties in the biocompatible nanocomposite has high potential for application in multimodal bioimaging. [ABSTRACT FROM AUTHOR]

Gold nanoclusters (AuNCs) are an emerging class of nanomaterials for bioimaging, featuring high photostability, size-dependent luminescence, large Stokes shifts, long photoluminescence lifetimes, and good biocompatibility. However, when stabilized by small ligands, AuNCs exhibit a limited colloidal stability. Here, we report the synthesis of original "hairy" AuNCs with a diameter under 2 nm and NIR photoluminescence (for both one-photon and two-photon excitation), stabilized by biocompatible end-grafted poly-(N-acryloyl morpholine) (PNAM) chains prepared by RAFT polymerization. The AuNCs synthesis was carried out directly in water in the presence of thiol-terminated PNAM-SH chains. Compared with AuNCs stabilized by small ligands, our PNAM-AuNCs exhibit much better colloidal stability (unchanged for more than two months), a 2-fold increase in photoluminescence lifetimes, and significantly enhanced quantum yields. Moreover, their properties could be successfully tuned using PNAM chains with molecular weights ranging from 3000 to 11 000 g·mol–1. These PNAM-AuNCs offer an excellent platform for the development of bioimaging probes without organic dyes. [ABSTRACT FROM AUTHOR]