Chemistry of Doped Colloidal Nanocrystals

Synthetic control over inorganic nanocrystals has made dramatic strides so that a great number of binary and a few ternary or more complex compounds can now be prepared with good control over size and physical properties. Recently, chemists have tackled the long-standing challenge of introducing dopant atoms into nanocrystals, and strategies that apply across diverse compositions are beginning to emerge. In this review, we first briefly summarize the array of characterization methods used to assess doping efficacy for reference throughout the discussion. We then enumerate chemical strategies for doping with illustrative examples from the literature. A key concept is that the reactions leading to growth of the host crystal and to deposition of dopant ions must be balanced to succeed in incorporating dopants during crystal growth. This challenge has been met through various chemical strategies, and new methods, such as postsynthetic diffusion of dopant ions, continue to be developed. The opportunity to deliver new functionality by doping nanocrystals is great, particularly as characterization methods and synthetic control over introduction of multiple dopants advance.