Metal-Enhanced Fluorescence from Quantum Dots

Quantum dots (QDs) have been extensively applied in biological detection, in vivo imaging and optoelectronic devices due to their unique optical properties including broad excitation spectra, tunable and narrow emission spectra, high brightness and excellent resistance to photobleaching. Nevertheless, application of aqueous QDs, especially that of aqueous near-infrared fluorescence QDs, is limited by their relatively weak fluorescence and poor stability. Therefore, the development of new approaches for the enhancement of fluorescence of QDs is urgently needed. In recent years, it has been found that the brightness and photostability of QDs can be favorably enhanced by surface plasmon resulted from the nearby metallic nanostructures, which is termed as metal-enhanced fluorescence (MEF). Thus novel strategies for solving the above problems can be proposed based on MEF from QDs, which can be mainly attributed to the increased excitation rate and the increased radiative rate of the excited QDs. In this review, mechanism of MEF, especially that of MEF related to QDs, is introduced based on the near-field interaction between metallic nanostructures and QDs. Key factors affecting the efficiency of fluorescence emission are reviewed, including the distance between metallic nanostructures and QDs, the type of QDs, the composition, shape, and size of metallic nanostructures, and so forth. Current progresses in the application of MEF from QDs are also summarized. Finally, challenges in the development of MEF from QDs are discussed. We believe that with the rapid development of nanoscience and nanotechnology, MEF from QDs will attract more and more attention and show unique potentials in the near future.