Phage-directed synthesis of copper sulfide: structural and optical characterization.

The growth of crystalline copper sulfide using a viral template was investigated using sequential incubation in CuCl₂ and Na₂S precursors. Non-specific electrostatic attraction between a genetically-modified M13 bacteriophage and copper cations in the CuCl₂precursor caused phage agglomeration and bundle formation. Following the addition of Na₂S, polydisperse nanocrystals 2-7 nm in size were found along the length of the viral scaffold. The structure of the copper sulfide material was identified as cubic anti-fluorite type Cu_1.8S, space group FmN3m. Strong interband absorption was observed within the ultraviolet to visible range with an onset near 800 nm. Furthermore, free carrier absorption, associated with the localized surface plasmon resonance of the copper sulfide nanocrystals, was seen in the near infrared with absorbance maxima at 1060 nm and 3000 nm, respectively. [ABSTRACT FROM AUTHOR]