Quantum dots breakthrough is a boon to bioimaging research

December 7, 2010—Jennifer Hollingsworth of Los Alamos National Laboratory’s Physical Chemistry and Applied Spectroscopy group and a team of researchers have developed an inorganic shell approach to suppress “blinking” in nanocrystal quantum dots (NQDs).

NQDs are semiconductor nanoparticles with remarkable size-tunable optical properties, including the ability to emit light efficiently. And, compared with molecular-dye flluorophores, optically excited NQDs are more stable.

But NQD applications have been limited due to a property known as fluorescence intermittency, or blinking. Under continuous illumination, single-nanocrystal quantum dots turn “on” and “off” in an unpredictable fashion. Blinking limits the utility of conventional NQDs for applications requiring continuous and reliable emission of photons, such as single-particle tracking in advanced bioimaging and as single-photon light sources in quantum cryptography.

Hollingsworth and her team applied an ultrathick and structurally perfect shell of a higher bandgap semiconductor to the core NQD to create a new class of nanocrystal quantum dots, the “giant” NQD (g-NQD), which has suppressed blinking and remarkable photostability. The researchers analyzed this effect as a function of shell thickness and composition. Their results revealed that for single-particle tracking applications shell thickness is a criterion for

• controlling blinking behavior
• improving NQD photostability
• altering the blinking mechanism
• providing enhanced utility.

The ability to follow the trajectory of single molecules as they perform their biological functions is an important goal for advanced bioimaging. As a proof-of-principle for single-particle tracking in biologically relevant environments, the team collaborated with James Werner and Peter Goodwin of the Center for Integrated Nanotechnologies (CINT) to show that g-NQDs outperform commercial NQDs in 3D tracking experiments. CINT is a joint effort of Los Alamos and Sandia National Laboratories.

The October 2010 Nanobiophotonics Special Issue of the Journal of Biophotonics published the research. Hollingsworth, Han Htoon, Yongfen Chen, Young-Shin Park, Yagnaseni Ghosh, and Joanna Casson of Physical Chemistry and Applied Spectrosopy, Peter Goodwin and James Werner of CINT, Javier Vela of Iowa State University, and Nathan Wells of Aerospace Corporation conducted the work. The National Institutes of Health and LANL’s Laboratory Directed Research and Development funded different aspects of the research.