Bio Serves Nano: Biological Light-Harvesting Complex as Energy Donor for Semiconductor Quantum Dots

Abstract

Light-harvesting complex (LHCII) of the photosynthetic apparatus in plants is attached to type-II core-shell CdTe/CdSe/ZnS nanocrystals (quantum dots, QD) exhibiting an absorption band at 710 nm and carrying a dihydrolipoic acid coating for water solubility. LHCII stays functional upon binding to the QD surface and enhances the light utilization of the QDs significantly, similar to its light-harvesting function in photosynthesis. Electronic excitation energy transfer of about 50% efficiency is shown by donor (LHCII) fluorescence quenching as well as sensitized acceptor (QD) emission and corroborated by time-resolved fluorescence measurements. The energy transfer efficiency is commensurable with the expected efficiency calculated according to Förster theory on the basis of the estimated donor-acceptor separation. Light harvesting is particularly efficient in the red spectral domain where QD absorption is relatively low. Excitation over the entire visible spectrum is further improved by complementing the biological pigments in LHCII with a dye attached to the apoprotein; the dye has been chosen to absorb in the "green gap" of the LHCII absorption spectrum and transfers its excitation energy ultimately to QD. This is the first report of a biological light-harvesting complex serving an inorganic semiconductor nanocrystal. Due to the charge separation between the core and the shell in type-II QDs the presented LHCII-QD hybrid complexes are potentially interesting for sensitized charge-transfer and photovoltaic applications.

The non-bilayer lipid MGDG stabilizes the major light-harvesting complex (LHCII) against unfolding

“…LHCII monomers inserted in PG-containing membranes tend to trimerize spontaneously 46 ; therefore, in order to address the impact of trimerization on the mechanical stability of LHCII, a LHCII variant was used with two point mutations in its trimerization motif (positions 16 and 17) that render the protein incapable of trimerization, as described earlier 8 . For comparing LHCII monomers and trimers, the complexes were inserted into membranes consisting of POPG exclusively.…”

Functionalized silicon quantum dots by N-vinylcarbazole: synthesis and spectroscopic properties

“…The absorption band at 320 to 360 nm of the N-ec-Si QDs is assigned to the carbazole ligand. It suggests that ligands can be employed to enhance the absorption of pure Si QDs, therefore providing a potential strategy to increase the light-harvesting efficiency of QDs in solar cells [52,53]. Upon excitation at 302 nm, the N-ec-Si QDs and N -vinylcarbazole show intense emission bands at approximately 358 nm and approximately 366 nm, respectively (Figure 3b).…”

Nanoparticles as energy donors and acceptors in bionanohybrid systems

“…The exact pigments system of LHCII consists of multiple copies of chlorophyll a and b and various carotenoids. LHCII from Pisum sativum was reported to efficiently transfer the excitation energy to the CdTe/ CdSe/ZnS QDs with emission maximum at 760 nm after electrostatic attachment (Werwie et al, 2012). The increase in the light-energy utilization was particularly effective in the red region of the visible spectrum where QDs absorption is low.…”