Photoinduced modification of quantum dot optical properties affects bacteriorhodopsin photocycle in a (quantum dot)- bacteriorhodopsin hybrid material

Ligand-Mediated Photobrightening and Photodarkening of CdSe/ZnS Quantum Dot Ensembles

“…Semiconductor quantum dots (QDs) are widely used inorganic fluorophores with a photoluminescence (PL) quantum yield (QY) reaching 100% , and photostability superior to those of traditional organic dyes. , Because of their advanced optical properties, QDs can be used in fields where long-term stability of fluorescence signal is required, such as optoelectronics, single-photon sources, bioimaging, , and lasing . However, long-term exposure to intense light may irreversibly change the QD optical properties, − which limits their possible applications. In general, two main irreversible steady-state processes occur in QDs under intense irradiation: photodarkening (PD), − when the PL QY of QDs is reduced, and photobrightening (PB), when the QY increases and PL becomes brighter. ,,,− These effects can be observed both in colloidal QD solutions − and in QD solids (e.g., thin films made of QDs). − Indeed, understanding of the origin of these processes is very important because it may strongly promote the improvement of QD optical stability and extend their applicability in QD-based devices.…”

“…However, long-term exposure to intense light may irreversibly change the QD optical properties, − which limits their possible applications. In general, two main irreversible steady-state processes occur in QDs under intense irradiation: photodarkening (PD), − when the PL QY of QDs is reduced, and photobrightening (PB), when the QY increases and PL becomes brighter. ,,,− These effects can be observed both in colloidal QD solutions − and in QD solids (e.g., thin films made of QDs). − Indeed, understanding of the origin of these processes is very important because it may strongly promote the improvement of QD optical stability and extend their applicability in QD-based devices.…”

“…For example, PD in thin QD films in the air was explained by the degradation of the QD surface caused by its reaction with the oxygen and water molecules, − whereas PB can be explained by passivation of surface defects of the QD crystalline structure by water molecules. , The relationship between PD and degradation of QD surface due to the photochemical reactions with oxygen was evidenced by a blue shift of the PL spectra − , due to the oxidative shrinking of the QD core, whereas no such shift was observed in an inert environment. ,, In the case of colloidal QD solutions, similar effects occur in the aqueous phase because of the interaction of QDs with dissolved oxygen . Under UV irradiation in chloroform, some of the solvent molecules decompose to hydrochloric acid, − which can etch the QD surface, leading to its degradation . However, the fact that PD and PB can be sometimes observed even in inert environments ,,, demonstrates that the photochemical reactions of QDs with water and oxygen cannot be the only reason for these phenomena.…”

Laser Irradiation as a Tool to Control the Resonance Energy Transfer in Bacteriorhodopsin–Quantum Dot Bio-Nano Hybrid Material

“…In our previous works we have studied the efficiently FRET in electrostatically bounded complexes of QD and purple membranes (PM) containing BR under one-and twophoton laser excitation [7][8][9]14]. To estimate this effect we have prepared aqueous solution of complexes of QD with PM, as in [14].…”

“…Semiconductor quantum dots (QDs) is fluorescent nanocrystals promising in the field of photovoltaics, optoelectronics and biosensing [2], which have high one-photon and two-photon absorption cross-sections in a UV-and NIR spectral regions, respectively, can significantly improve the light sensitivity of BR by means of Förster resonance energy transfer (FRET) from QD to BR [3][4][5][6][7][8][9][10][11]. In turn, the high work efficiency of the QD-BR nano-bio hybrid material implies a large number of FRET elementary actions from QD to BR per time unit, which is in strong correlation with the QDs' excited state population.…”