Quantum Dot Assembly Driven by Electrochemically Generated Metal-Ion Crosslinkers

Control of nanoparticle assembly is a critical enabler for fabricating nanostructures capable of complex, system-level functionality. Here, we report a facile electrochemical method for assembling quantum dots (QDs) into mesoporous gels directly onto an electrode surface using localized, in situ generated metal ion crosslinkers (Ni2+, Co2+, Ag+, or Zn2+) within a colloidal solution of metal chalcogenide nanoparticles capped with ligands featuring pendant carboxylate groups. A mechanistic study reveals a critical stoichiometry of 0.5 metal ions: 1 QD in solution is required to trigger metal ion-mediated electrogelation (ME-gelation), representing a much lower concentration of metal ions than is needed for initiating crosslinking throughout an entire volume of solution (>26 metal ions: 1 QD in solution). The application of the ME gelation approach for the fabrication of QD-based electronic devices is demonstrated by electrochemical patterning of QD gels onto a printed circuit board chip.