FluidFM Deposition of Semiconductor Quantum Dots From Aqueous Dispersions

ABSTRACT FluidFM deposition, also known as pressure‐controlled and force‐controlled micropipetting, of nanomaterials suspended in fluidic carrier liquids is known as a capillary‐driven, high‐precision liquid‐in‐liquid deposition and manipulation technique in biofluidic environments. In this work, we report on its usage as a liquid‐on‐solid structuring technique from an aqueous dispersion of colloidal inorganic semiconductor Ag–In–S quantum dots (QDs) stabilized with glutathione ligands on solid substrates. We show the recurrent deposition (3 3 matrix) and characterization of three‐dimensional liquid‐in‐air deposits formed by structured sedimentation of the QDs on gold‐coated glass substrates upon FluidFM deposition via bottom‐up self‐assembly. As critical facts for a successful deposition of the QDs turn out: The aqueous nature of the dispersion, the possibility for its careful adjustment regarding density and composition, and an effective surface energy engineering of both the FluidFM cantilever and the gold‐coated glass substrates mediated by chemical vapor deposition and physical vapor deposition, respectively. This way, the minimal lateral dimensions of the obtained deposits were (500 40) µm, with evaporation‐limited contact‐line widths of (2.0 0.5) µm.