Altering coupled mode of surface plasmon resonance mediated by silver and gold nanoparticles through heat treatment: Judd ofelt, racah and NIR-luminescence of neodymium doped magnesium-zinc-sulfophosphate glass

Manipulating surface plasmon resonance (SPR) of silver (Ag) and gold (Au) nanoparticles (NPs) in amorphous material may open new possibilities in optic and photonic fields. Driven by this fact, heat treatments (HT) were used to tune the excitation mode of SPR. The Nd3+ doped magnesium-zinc-sulfophosphate glasses embedded with Ag and Au NPs were heat-treated at 450 degrees C for 6 and 12 h and characterized using X-ray diffractometer (XRD), high-resolution transmission electron microscope (HRTEM), UV-Vis-NIR absorption and photo-luminescence (PL) spectrometer. The mean size of NPs was slightly reduced (4.68 nm -> 4.35 nm) after 12 h of HT due to the elastic ripening process, causes by internal pressure within NPs. Unusual multiple SPR bands were evidence around 419, 481, 613, 676, 776, 848 and 939 nm after the glass (AgAu6h) is heat-treated for 6 h. Thirteen absorption bands are recorded within 326-875 nm, corresponding to the Nd3+ ion transitions. The NIR PL bands of Nd3+ ion were detected around 878 nm, 1050 nm, and 1322 nm corresponding to 4F3/2 -> 4I9/2, 4F3/2 -> 4I11/2, and 4F3/2 -> 4I13/2 transitions, respectively. Overall, sample coded AgAu12 h disclosed the highest bandwidth gain of 0.09, 1.14, and 3.06 ( x 10-22 cm3) assigned to transition 4F3/2 -> 4I9/2, 4F3/2 -> 4I11/2, and 4F3/2 -> 4I13/2, respectively, with a quantum efficiency of 21.06% (for transition 4F3/2 -> 4I11/2). The HT can modify the intensity of PL through different NPs assemblies (single, dimer, trimer) and bonding modes (e.g: longitudinal dipolar or quadrupolar coupling mode). The unique optical feature discovered may be useful in customizing solid-state laser materials.