The variation in localized surface plasmon resonances of single Au nanodisks (diameter 100 nm and height 25 nm) on 0−13 graphene layers is investigated using dark-field scattering spectroscopy to obtain the graphene electric field screening length. For nanodisks (NDs) with and without underlying graphene layers on a SiO 2 (300 nm)/Si substrate, the plasmon resonance red shifts from 604 to 620 nm with increasing graphene layers. The spectra of the plasmonic nanostructures obey an exponential saturation function versus increasing number of layers of graphene from 0 to 13. As a conducting film, the graphene layers screen the electric field generated by the plasmonic resonance of the Au NDs in the vicinity of the interface, and the red shifts of the resonance wavelength are explained in the framework of the electromagnetic field coupling between in-plane antiparallel image dipoles in the graphene layers and the ND dipole. A screening length of 1.2 ± 0.2 nm, equivalent to 3−4 graphene layers, is experimentally obtained, in good agreement with the measurement by field-effect transistors and theoretical calculation in doped graphene. The resonance shift of plasmonic nanostructures on a layered graphene system provides an alternative and convenient method for screening length measurement of graphene films.
Gold nanostructures of various morphologies, including nanospheres, nanorods, nanoprisms, and thin films, were immobilized on ITO-coated coverslips in order to investigate the response of their scattering to potential. Shifts in the plasmon band obtained by potential-modulated spectroscopic imaging indicated that the voltage sensitivity of the gold nanostructure is dependent on its morphology, with nanospheres exhibiting the lowest sensitivity and ultrathin gold films exhibiting the highest. The effects of potential on gold nanoparticles are in qualitative agreement with Mie and Gans' theories in which the shift of the gold plasma frequency is due to the charging-discharging of the nanoparticles.
Fluorescent
detection of glutathione (GSH) in the living system
has attracted much attention, but current fluorescent probes are usually
exposed to the exterior environment, leading to photobleaching and
premature leakage and subsequently limiting the sensitivity and photostability.
Herein, luminescent metal–organic frameworks [Ru(bpy)3
2+ encapsulated in UiO-66] coated with manganese dioxide
nanosheets [MnO2 NS@Ru(bpy)3
2+–UiO-66]
were prepared by an in situ growth method and further explored to
construct a GSH-switched fluorescent sensing platform. Because of
the splendid fluorescence quenching ability, special probe leakage
blocking role and distinguished recognition of the MnO2 NS, and the improved fluorescence of Ru(bpy)3
2+ by UiO-66, a low background, highly sensitive and selective detection
of GSH with a low limit of detection as 0.28 μM was realized.
At the same time, the preparation of MnO2 NS@Ru(bpy)3
2+–UiO-66 nanocomposites is simple and less
toxic, and there was no notable loss of cell survivability after being
exposed to MnO2 NS@Ru(bpy)3
2+–UiO-66
below the concentrations of 120 μg mL–1 for
24 h. Consequently, the results coming from this effort suggest that
the new sensing platform will have a great potential in the detection
of GSH in living cells.
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