This communication reports an efficient visual detection method of Cu2+ by L-cysteine functionalized gold nanoparticles in aqueous solution. Upon exposure to Cu2+, the gold nanoparticle solution changed from red to blue, in response to surface plasmon absorption
of dispersed and aggregated nanoparticles. This colorimetric sensor allows a rapid quantitative assay of Cu2+ down to the concentration range of 10−5 M. Recognition of Cu2+ and formation of the aggregates are proposed to occur via a 2 : 1 sandwich complex
between L-cysteine and Cu2+.
A Fano resonance is experimentally observed in a single silver nanocube separated from a supporting silver film by a thin aluminum oxide film. The resonance spectrum is modulated by changing the size of the silver nanocube and its distance from the silver film. The system is fabricated by a bottom-up process with an accurately controlled nanogap at the sub-6-nm scale. The simulation result shows that the destructive interference between the dipole mode and the quadrupole mode in this “nanocube on mirror” (NCoM) structure is responsible for the resonance. The spectra red-shifted as the size of the silver nanocube increased and its distance from the silver film decreased. In addition, a refractive index sensitivity of the spectrum of 140 meV/RIU (refractive index unit), with a 2.4 figure of merit, is obtained by changing the dielectric environment around the silver nanocube. This work will enable the development of high-performance tunable optical nanodevices based on NCoM structures.
Abstract. The forster resonance energy transfer (FRET) between different CdTe QDs and RhB were investigated by steady-state and femtosecond time-resolved photoluminescence spectra technique. Through the measurements on three different CdTe sample solutions, it was found that the FRET efficiency is proportional to the spectral overlap degree of CdTe QDs' emission and RhB's absorption. And the FRET efficiency was found to increase with the increase of the RhB's concentration, while the concentration increase to more than 4.5×10-5 mol/L, the transfer efficiency decreases. The FRET efficiency can reach to 32.6% when RhB concentration is 4.5×10-5 mol/L. With the wide use of FRET in biomolecular interaction analysis and cell physiology, the CdTe QDs-RhB hybrid systems could be a promising candidate for fluorescent probe and photodynamic therapy.
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