Excessive Increase in the Optical Band Gap of Near-Infrared Semiconductor Lead (II) Sulfide via the Incorporation of Amino Acids

Incorporation of organic molecules into the crystal lattice of biominerals is one of Nature's main strategies to modify the structure, morphology, and specific physical properties of the mineral host. Inspired by this biostrategy, it is shown that several semiconductors, whose band gaps are in the ultraviolet or visible absorption spectrum, can incorporate individual amino acids (AAs) into their crystalline structures. Interestingly, such incorporation is accompanied by an increase in the optical band gap of semiconductor hosts, resulting from an internal quantum confinement effect. In this work, this bioinspired route of band gap tuning is applied for the first time to a semiconductor with a near-infrared (NIR) band gap. Indeed individual AAs are found to become incorporated into the crystalline structure of lead (II) sulfide (PbS). It is shown that this incorporation induces an expansion of the PbS unit cell as well as changes in the morphology. Moreover, an unprecedented increase of up to 40-50% in the optical band gap is observed in the case of cysteine and lysine incorporation.