Near-infrared quantum dots: synthesis, functionalization and analytical applications.

As light-emitting nanocrystals, quantum dots (QDs) have been a major focus of research and development during the past decade. The impetus behind such endeavors can be attributed to their unique chemical and optical properties, with size-tunable light emission, high photostability, and multiple fluorescence colors. In recent years, near-infrared (NIR) quantum dots have emerged as a promising tool in analytical applications, especially for in vivo imaging and therapy. NIR QDs allow photon penetration through tissue and minimize the effects of tissue autofluorescence. This is important for detecting or identifying species in complex biological samples. This review focuses on the development and analytical applications of NIR QDs. Different types of NIR QDs have been synthesized and characterized from various designed strategies. In the functional process, QDs can be modified as sensitive probes with high affinity and specificity, such as being linked with proteins, peptides or other small molecules. Recent advances of NIR QDs applications are presented, including in vivo imaging, fluorescence enhancement/quenching, and fluorescence resonance energy transfer. We also discuss the limitation of NIR QDs in applications. The advantages and challenges in developing NIR QDs are summarized in this review from the viewpoint of analytical chemistry.