Silicon as Reducing Agent for Controlled Production of Plasmonic Copper Nanocomposite Glasses: A Spectroscopic Study

Abstract

The use of silicon to produce metal nanocomposite phosphate glasses with plasmonic properties is proposed. It is demonstrated how the reducing properties of Si powder allow for producing Cu nanocomposite glasses in a controlled manner during heat treatment (HT). Cu/Si-codoped glasses were prepared in a 50BaO-50P 2 O 5 matrix by a simple melt-quench method in ambient atmosphere. The worst-case scenario is considered by having the noble metal introduced in its higher oxidation state as copper(II) oxide, i.e., instead of using monovalent copper. Optical absorption and photoluminescence (PL) spectroscopy, including emission decay dynamics, were employed for characterization of the melt-quenched glass, and for investigating the influence of HT on material optical properties. Remarkably, increasing amounts of Si powder were observed to suppress and ultimately remove the Cu 2+ visible absorption band in the CuO-containing glasses. Moreover, subsequent HT of the glass with the highest Si content resulted in progressive development of the surface plasmon resonance of Cu nanoparticles with increasing holding time. PL spectroscopy analysis is further employed towards elucidating the Cu 2+ fi Cu + fi Cu 0 valence state changes likely occurring during the melting and subsequent thermal processing.

Ag and Si Codoped Phosphate Glasses: Plasmonic Nanocomposites with Enhanced UV Transparency

“…It is also worth noting at this point that in Ref. although NP precipitation was obtained with silicon and copper in place of silver, the UV transparency in the as‐melted CuSi glasses therein was not as much enhanced as with silver in the present work. The reason for this seems to be the strong near‐UV absorption of Cu + ions, phenomenon that has been recently reported to have a particular dependence on Cu + –Cu + interionic distance .…”

“…Remarkable reduction of Cu 2+ was consistently demonstrated, whereby copper was added in its highest oxidation state as CuO. In both cases, a slight blue shift in the UV absorption profile of the glasses was observed in the melt‐quenched glasses . However, such an affect was not observed when SnO was used as the reducing agent together with CuO .…”

“…Phosphate glasses with a 50P 2 O 5 :50BaO (mol%) composition were prepared from high purity Alfa Aesar chemicals (P 2 O 5 , ≥98% and BaCO 3 , 99.8%) by the melt‐quenching technique . The batch materials (about 25 g batches) were thoroughly mixed and melted in porcelain crucibles at 1150°C between 15 and 25 min under normal atmospheric conditions and immediately quenched.…”

“…In the context of plasmonic materials, the addition of carbon as part of batch materials was recently demonstrated effective by the author for the controlled production of Cu nanocomposite glasses by melting and heat‐treatment (HT) processes . Similarly, the use of silicon powder was proposed for doping the glasses with Cu nanoparticles (NPs) . Remarkable reduction of Cu 2+ was consistently demonstrated, whereby copper was added in its highest oxidation state as CuO.…”

“…However, such an affect was not observed when SnO was used as the reducing agent together with CuO . Hence, structural rearrangements were pointed out as possibly linked to the creation of highly reactive oxygen radicals upon melt quenching . However, further investigations are necessary in order to improve current understanding about the structural properties of these systems.…”