“…The inset shows the relative emission intensity of the observed emission bands vs. heat-treatment time. Seven emission bands centered at 530 nm, 594 nm, 612 nm, 645 nm, 680 nm, 703 nm, and 728 nm are observed and attributed to the 3 P 0 → 3 H 5 , 1 D 2 → 3 H 4 , 3 P 0 → 3 H 6 , 3 P 0 → 3 F 2 , 3 P 1 → 3 F 3 , 3 P 0 → 3 F 3 , and 3 P 0 → 3 F 4 transitions of Pr 3+ ions [21,36], respectively. Sample D shows the largest luminescence enhancement for most of the transitions observed, indicating that the best condition for the NP nucleation is achieved for heat-treatment during 10 h. In other words, saturation is observed, which indicates that all silver ions have been reduced to metallic silver for thermal treatment during about 10 h. Fig.…”