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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 (AuNC) with a precise number of Au atoms feature unique properties for imaging applications, including size dependent photoluminescence, very high photostability, and large Stokes shift. However, their low colloidal stability often leads to aggregation and fusion into larger gold nanoparticles (AuNPs), hindering the wider use of AuNC. Here, we report the first successful encapsulation of NIR emitting AuNC in polymer nanoparticles (PNPs). The AuNC, with 25 gold atoms and stabilized by 6-mercaptohexanoic acid (MHA), were encapsulated in PNPs with ca. 50 nm in diameter, obtained by miniemulsion polymerization of butyl methacrylate (BMA) and varying amounts of methyl methacrylate (MMA). While thermo-initiation led to aggregation of AuNC into plasmonic (non-emissive) AuNPs, the use of photo-initiation effectively preserved the AuNC inside the PNPs. By encapsulating a large number of AuNC, we obtained PNPs with high brightness in the NIR, both by one- and two-photons excitation. [Display omitted] [ABSTRACT FROM AUTHOR]