Fig. 3 | Nature Communications

Fig. 3

From: Integrating temporal and spatial control of electronic transitions for bright multiphoton upconversion

Fig. 3

Concentration quenching in the NaYF4:Er@NaYF4 nanocrystals. a Proposed concentration quenching processes in NaErF4@NaYF4 core−shell nanoparticles by 1532 nm excitation. The full, wavy, and colored arrows represent excitation, multiphonon relaxation, and emission processes, respectively. b Emission spectra of NaYF4:Er (2−100 %)@NaYF4 nanoparticles in cyclohexane dispersions (0.01 M) as a function of Er3+ concentration. All spectra were recorded under excitation of a 1532 nm CW diode laser at a power density of 21 W cm−2. Inset: luminescence photographs of the corresponding nanoparticle colloids. c The relative oscillator strengths for different excited states as a function of Er3+ concentration. Note that the concentrations in the theoretical calculation may not be exactly the same as that used in the experiments but still correctly illustrate the evolution of electronic transition probabilities

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