Nanoscale fluorescence imaging with quantum dot near-field electroluminescence

We demonstrate near-field fluorescence excitation and imaging with a quantum dot (QD) light emitting diode (QDLED) integrated at the tip of a scanning probe. The tip-embedded QDLED is employed in a near-field scanning optical microscopy setup to directly excite a secondary colloidal QD sample. Electrically pumped QDs enable multi-color, self-illuminating probes with no conventional optics needed for light coupling. Monolayer QDs stamped at the very tip of a micromachined silicon probe facilitates precise position control of the ultra-thin (10–15 nm) light source. Sensitivity of fluorescence intensity to the QDLED–QD sample distance was measured down to 50 nm order, demonstrating spatially resolved imaging.