Plasmon-enhanced upconversion luminescence and application of molecular detection
Fluorescence molecular detection exhibits limited development in detection applications due to generally low sensitivity and narrow detection range.The heavily doped semiconductor nanostructures Cu2-xS with surface plasmon resonance effect and typical rare-earth-doped upconversion luminescent nanoparticles NaYF4∶Yb,Er were prepared,and further Cu2-xS/NaYF4∶Yb,Er film substrates were obtained by three-phase interfacial self-assembly method.Combined with finite element method simulations,the local electric field distributions around Cu2-xS were calculated for different placement situations.The plasmon-coupling effect generated between Cu2-xS nanodisks was investigated on the upconversion luminescence performance and the Raman signals.Based on the intense upconver-sion luminescence caused by the excellent synergetic localized surface plasmon resonance effect,a dual detection method of qualitative before quantitative detection of Rhodamine B using surface-enhanced Raman scattering signal monitoring and fluorescence sensing was established.The results show that the coupling of the Cu2-xS plasmonic layer with the NaYF4∶Yb,Er luminescent layer not only enables three orders of magnitude improvement of upcon-version emission,but also achieves the detection limit of 10-7 mol·L-1for molecular detection and obtains a broad linear response from 10-3 to 10-7 mol·L-1,and finally realizes the qualitative and quantitative bifunctionality of high-sensitivity accurate detection.
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