Two-photon-induced Förster Resonance Energy Transfer in a Quantum dot–bacteriorhodopsin Hybrid Material

Two-photon-induced Förster resonance energy transfer from water-solubilized CdSe/ZnS quantum dots (QDs) to the photosensitive protein bacteriorhodopsin (bR) is described. The two-photon absorption cross section (TPACS) of QDs at an excitation wavelength of 790nm has been found to be about 20000 GM, which is two orders of magnitude larger than the maximal TPACS of bR. Therefore, the two-photon excitation of QDs in QD-bR systems is highly selective. The data obtained demonstrate the possibility to extend the effective spectral range of excitation of bR to the infrared region. This result paves a way to new applications of bR–QD hybrid materials in photovoltaics, biosensing, and optoelectronics.