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This paper investigates the factors which can influence the quenching effect from the perspective of energy transfer. The quenched fluorescence of the CdSe semiconductor quantum dots (SQDs) by using plasmonic Au nanocrystals (p-AuNCs) and molecule-like Au nanocrystals (m-AuNCs) in aqueous suspensions and spin-coated films is comparatively investigated. In the aqueous suspensions, the p-AuNCs have larger quenching effect than the m-AuNCs. In the spin-coated films, the p-AuNCs and m-AuNCs have comparable quenching factor. Furthermore, the experiments show that the p-AuNCs simultaneously enhance the radiative and nonradiative rates. But the m-AuNCs only enhance the nonradiative rate of the SQDs, which reveals the difference of quenching process between the p-AuNCs and m-AuNCs. This result of the research has guiding significance for the detection technique based on the fluorescence quenching.

Silver nanoplates have obvious advantages compared with other silver structural nanoparticles due to their wide tunability of the local surface plasmon resonance (LSPR) and significant local field enhancement around the sharp corners. Nonlinear optical absorption (NLA) and nonlinear optical refraction (NLR) are widely employed to characterize the nonlinear optical properties due to their simply testing requirement and comparable valuable results. Z-scan method is widely used in optical characterization of nonlinear properties of different materials. Here, a seed-mediated growth method of the silver nanoplates with well controlled size and local surface plasmon wavelength is presented. The nanoparticle size increases gradually and becomes more uniform distribution as the red-shift of the plasmon resonance wavelength from 650 nm to 950 nm. In particular, we show the dependence of NLA and NLR of the silver nanoplates on the LSPR. The absolute value of effective NLA coefficient increases from 1.38 to 4 cm/GW and that of the NLR index increases as large as 3 times when the LSPR wavelength changes from 728 nm to 898 nm, which is attributed to the strong plasmon absorption and local filed enhancement of larger size silver nanoplates. These findings have great potentials in the explorations of functional non-linear devices.

The controllable synthesis of uniform tungsten diselenide (WSe