Iron(III)-quantity-dependent aggregation-dispersion conversion of functionalized gold nanoparticles.

Developing gold nanoparticles (AuNPs) with well-designed functionality is highly desirable for boosting the performance and versatility of inorganic-organic hybrid materials. In an attempt to achieve ion recognition with specific signal expressions, we present here 4-piperazinyl-1,8-naphthalimide-functionalized AuNPs for the realization of quantitative recognition of Fe(III) ions with dual (colorimetric and fluorescent) output. The research takes advantage of 1) quantity-controlled chelation-mode transformation of the piperazinyl moiety on the AuNPs towards Fe(III), thereby resulting in an aggregation-dispersion conversion of the AuNPs in solution, and 2) photoinduced electron transfer of a naphthaimide fluorophore on the AuNPs, thus leading to reversible absorption and emission changes. The functional AuNPs are also responsive to pH variations. This strategy for realizing the aggregation-dispersion conversion of AuNPs with returnable signal output might exhibit application potential for advanced nanoscale chemosensors.