An aqueous synthesis methodology for the preparation of silica nanoparticles (SNPs), core-shell SNPs having, for example, a size of 2 to 15 nm and narrow size-dispersion with size control below 1 nm, i.e. at the level of a single atomic layer. Different types of dyes, including near infrared (NIR) emitters, can be covalently encapsulated within and brightness can be enhanced via addition of extra silica shells. The surface may be functionalized with polyethylene glycol (PEG) groups and, optionally, specific surface ligands. This aqueous synthesis methodology also enables synthesis of 2 to 15 nm sized fluorescent core and core-shell aluminosilicate nanoparticles (ASNPs) which may also be surface functionalized. Encapsulation efficiency and brightness of highly negatively charged NIR fluorophores is enhanced relative to the corresponding SNPs without aluminum.
