Colloidal semiconducting nanocrystals, or quantum dots (QDs), when coupled to subwavelength nanophotonic structures, such as optical nanoantenna and nanoscale resonators, can have enhanced emission properties – enhancement of the radiative rate by the well-known Purcell effect, improved excitation efficiency, and control over the direction and polarization of emitted light. Here, we report the integration by dip-pen nanolithography (DPN) of ultra-photostable giant QDs (gQDs) and three-dimensional nanoantennas as a prototype hybrid system for realizing such enhanced light-emission properties. DPN is a scanning probe-based alternative lithography technique that uses an atomic force microscope tip to precisely “write” liquid “ink” onto diverse solid substrates. We report a comprehensive investigation of factors controlling DPN of complex liquid inks comprising a non-aqueous carrier solvent and suspended gQDs. Two different sized gQDs were used, and with different colloidal stability of the suspension, a very different DPN inking/writing behavior was observed. We also studied key DPN experimental parameters and their relationship to deposition rate, including dwell time, surface-ink interactions (surface hydrophilicity/phobicity effects) and volume of ink on the writing tip. We further advanced a three-step reading-inking-writing approach using DPN to precisely place gQDs onto the nanoantennas, realizing for the first time deposition targeted to sub-micron substrate features. Overall, the new understanding of ink-substrate interactions and the parameters controlling bulk fluid flow from nano-tip to substrate lays the groundwork for the expanded use of DPN for integration of multi-component nanostructures, comprising “soft” and “hard” constituents, that would be challenging or impossible to create using traditional lithographic techniques.

Integration of colloidal giant quantum dots and 3D nanoantennas by dip-pen nanolithography

256th National Meeting (2018)

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