Estimation of the Number of Quantum Dots Immobilized on an Ultra-flat Au Surface

Quantum dots (QDs) were immobilized on an ultra-flat Au surface by using amide binding between the carboxyl groups on the QDs and the amino groups of the self-assembled monolayer on the surface. The number density of the QDs estimated by atomic force microscopy (AFM) agreed with the quantity of QDs estimated by X-ray photoelectron spectroscopy and fluorescence microscopy. QDs were also immobilized on dot patterns fabricated by e-beam lithography. AFM was able to identify clusters of just a few QDs on the dot patterns, whose minimum designed size was 50 nm × 50 nm per dot.