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1.
Langmuir ; 32(40): 10268-10275, 2016 10 11.
Article in English | MEDLINE | ID: mdl-27618561

ABSTRACT

We have investigated the physical and biomimetic properties of a sponge (L3) phase composed of pentaethylene glycol monododecyl ether (C12E5), a nonionic surfactant, an aqueous solvent, and a cosurfactant. The following cosurfactants, commonly used for solubilizing membrane proteins, were incorporated: n-octyl-ß-d-glucopyranoside (ß-OG), n-dodecyl-ß-d-maltopyranoside (DDM), 4-cyclohexyl-1-butyl-ß-d-maltoside (CYMAL-4), and 5-cyclohexyl-1-pentyl-ß-d-maltoside (CYMAL-5). Partial phase diagrams of these systems were created. The L3 phase was characterized using crossed polarizers, diffusion of a fluorescent probe by fluorescence recovery after pattern photobleaching (FRAPP), and freeze fracture electron microscopy (FFEM). By varying the hydration of the phase, we were able to tune the distance between adjacent bilayers. The characteristic distance (db) of the phase was obtained from small angle scattering (SAXS/SANS) as well as from FFEM, which yielded complementary db values. These db values were neither affected by the nature of the cosurfactant nor by the addition of membrane proteins. These findings illustrate that a biomimetic surfactant sponge phase can be created in the presence of several common membrane protein-solubilizing detergents, thus making it a versatile medium for membrane protein studies.


Subject(s)
Biomimetic Materials/chemistry , Ethers/chemistry , Lipid Bilayers/chemistry , Polyethylene Glycols/chemistry , Surface-Active Agents/chemistry , Water/chemistry , Alkanes/chemistry , Glycosides/chemistry , Membranes, Artificial , Neutron Diffraction , Scattering, Small Angle , Solvents/chemistry , Temperature , Viscosity , X-Ray Diffraction
2.
Nat Nanotechnol ; 10(6): 491-6, 2015 Jun.
Article in English | MEDLINE | ID: mdl-25938570

ABSTRACT

Semiconductor quantum dots have emerged as promising candidates for the implementation of quantum information processing, because they allow for a quantum interface between stationary spin qubits and propagating single photons. In the meantime, transition-metal dichalcogenide monolayers have moved to the forefront of solid-state research due to their unique band structure featuring a large bandgap with degenerate valleys and non-zero Berry curvature. Here, we report the observation of zero-dimensional anharmonic quantum emitters, which we refer to as quantum dots, in monolayer tungsten diselenide, with an energy that is 20-100 meV lower than that of two-dimensional excitons. Photon antibunching in second-order photon correlations unequivocally demonstrates the zero-dimensional anharmonic nature of these quantum emitters. The strong anisotropic magnetic response of the spatially localized emission peaks strongly indicates that radiative recombination stems from localized excitons that inherit their electronic properties from the host transition-metal dichalcogenide. The large ∼1 meV zero-field splitting shows that the quantum dots have singlet ground states and an anisotropic confinement that is most probably induced by impurities or defects. The possibility of achieving electrical control in van der Waals heterostructures and to exploit the spin-valley degree of freedom renders transition-metal-dichalcogenide quantum dots interesting for quantum information processing.

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