In various aspects provided are methods for producing a nanoparticle within a cross-linked, collapsed polymeric material. In various embodiments, the methods comprise (a) providing a polymeric solution comprising a polymeric material; (b) collapsing at least a portion of the polymeric material about one or more precursor moieties; (c) cross-linking the polymeric material; (d) modifying at least a portion of said precursor moieties to form one or more nanoparticles and thereby forming a composite nanoparticle.