Enhanced and tunable fluorescent quantum dots within a single crystal of protein

The design and synthesis of bio-nano hybrid materials can not only provide new materials with novel properties, but can also advance our fundamental understanding of interactions between biomolecules and their abiotic counterparts. Here, we report a new approach to achieving such a goal by growing CdS quantum dots (QDs) within single crystals of lysozyme protein. This bio-nano hybrid emitted much stronger red fluorescence than its counterpart without the crystal, and such fluorescent properties could be either enhanced or suppressed by the addition of Ag(I) or Hg(II), respectively. The three-dimensional incorporation of CdS QDs within the lysozyme crystals was revealed by scanning transmission electron microscopy with electron tomography. More importantly, since our approach did not disrupt the crystalline nature of the lysozyme crystals, the metal and protein interactions were able to be studied by X-ray crystallography, thus providing insight into the role of Cd(II) in the CdS QDs formation.