Brightening, blinking, bluing and bleaching in the life of a quantum dot: friend or foe?

Semiconductor nanocrystals or quantum dots (QDs) are highly photoluminescent materials with unique optical attributes that are being exploited in an ever-increasing array of applications. However, the complex surface chemistry of these finite-sized fluorophores gives rise to a number of photophysical phenomena that can complicate their use in imaging applications. Fluorescence intermittency (FI), photoluminescence enhancement (PLE) and spectral bluing are properties of QD emission that would appear, at first sight, detrimental to quantitative measurement. Fortunately, developments in rational QD synthesis and surface modification are promising to minimize the effects of these fluorescence instabilities, while applications that exploit them are now coming to the fore. We review recent experimental and theoretical studies of FI, PLE and bluing, highlighting the benefits, as well as complications, they bring to key applications.