Controlled formation of gold nanoparticles with tunable plasmonic properties in tellurite glass.

Silicate glasses with metallic nanoparticles (NPs) have been of intense interest in art, science and technology as the plasmonic properties of these NPs equip glass with light modulation capability. The so-called striking technique has enabled precise control of the in situ formation of metallic NPs in silicate glasses for applications from coloured glasses to photonic devices. Since tellurite glasses exhibit the unique combination of comparably easy fabrication, low phonon energy, wide transmission window and high solubility of luminescent rare earth ions, there has been a significant amount of work over the past two decades to adapt the striking technique to form gold or silver NPs in tellurite glasses. Despite this effort, the striking technique has remained insufficient for tellurite glasses to form metal NPs suitable for photonic applications. Here, we first uncover the challenges of the traditional striking technique to create gold NPs in tellurite glass. Then, we demonstrate precise control of the size and concentration of gold NPs in tellurite glass by developing new approaches to both steps of the striking technique: a controlled gold crucible corrosion technique to incorporate gold ions in tellurite glass and a glass powder reheating technique to subsequently transform the gold ions to gold NPs. Using the Mie theory, the size, size distribution and concentration of the gold NPs formed in tellurite glass are determined from the plasmonic properties of the NPs. This fundamental research provides guidance for designing and manipulating the plasmonic properties in tellurite glass for photonics research and applications.

Thermal collapse and hierarchy of polymorphs in a faujasite-type zeolite and its analogous melt-quenched glass.

We examine the route of structural collapse and re-crystallization of faujasite-type (Na,K)-LSX zeolite. As the first step, a rather stable amorphous high density phase HDAcollapse is generated through an order-disorder transition from the original zeolite via a low density phase LDAcollapse, at around 790 °C. We find that the overall amorphization is driven by an increase in the bond angle distribution within T-O-T and a change in ring statistics to 6-membered TO4 (T = Si(4+), Al(3+)) rings at the expense of 4-membered rings. The HDAamorph transforms into crystalline nepheline, though, through an intermediate metastable carnegieite phase. In comparison, the melt-derived glass of similar composition, HDAMQ, crystallizes directly into the nepheline phase without the occurrence of intermediate carnegieite. This is attributed to the higher structural order of the faujasite-derived HDAcollapse which prefers the re-crystallization into the highly symmetric carnegieite phase before transformation into nepheline with lower symmetry.

A reconstructive polyamorphous transition in borosilicate glass induced by irreversible compaction.

Understanding the response of glasses to high pressure is of key importance for clarifying energy-dissipation and the origin of material damage during mechanical load. In the absence of shear bands or motile dislocations, pressure-induced deformation is governed by elastic and inelastic structural changes which lead to compaction of the glass network. Here, we report on a pressure-induced reconstructive amorphous-amorphous transition which was detected in sodium borosilicate glass by Raman and Brillouin scattering. The transition occurs through the formation of four-membered danburite-type rings of BO4 and SiO4-tetrahedra. We suggest that the inelastic pressure-resistance is governed by the Si-O-Si-backbone of the mixed borosilicate network. We further show that compaction is accompanied by increasing structural homogeneity and interpret this as a universal phenomenon in non-crystalline materials.