We show that stretching polystyrene melts at a rate faster than the inverse Rouse time followed by rapid quenching below the glass transition temperature, results in a material that is flexible and remains so for at least six months. Oriented micro/nano fibers are observed in the flexible samples after the mechanical tests. The fibers are probably related to the highly aligned molecules in melt stretching. At room temperature, a tensile strength over 300MPa has been achieved for the flexible polystyrenes.

In this letter, we present a comparative experimental–simulation study of Au-nanodisc-enhanced upconversion of 1500 nm light in an Er3+ doped TiO2 thin film. The geometry of the Au nanodiscs was guided by finite-element simulations based on a single nanodisc in a finite computational domain and controlled experimentally using electron-beam lithography. The surface-plasmon resonances (SPRs) exhibited a well-known spectral red shift with increasing diameter, well explained by the model. However, an experimentally observed double-peak SPR, which resulted from inter-particle interactions, was expectedly not captured by the single-particle model. At resonance, the model predicted a local-field enhancement of the upconversion yield, and experimentally, the luminescence measurements showed such enhancement up to nearly 7 fold from a nanodisc with 315 nm diameter and 50 nm height. The upconversion enhancement agreed qualitatively with the theoretical predictions, however with 3–5 times higher enhancement, which was attributed to scattered light from neighboring particles.

Silver nanoparticles, placed on top of an Er3+ doped TiO2 thin film, were investigated as a means of achieving enhanced up-conversion. Finite-element modeling was used to determine the nanoparticle dimensions (height and diameter) yielding the largest plasmonic enhancement for an incident light wavelength of 808 nm. In order to mimic the experimentally observed up-conversion enhancement, the electric-field enhancement from the Ag nanoparticles was integrated over the entire thickness of the thin film. Based on these calculations, four samples were prepared and tested. The trends predicted by the models were found to correlate well with the trends of the experimentally obtained plasmonic enhanced up-conversion yields. The largest plasmonic enhancement for 808 nm excitation was observed for Ag nanoparticles of diameter 91 ± 5 nm and height 14 ± 1 nm, yielding 163- and 51-fold enhancements for the green (525 nm and 550 nm) and red (660 nm) emissions peaks, respectively.

This work presents a study of the luminescence properties of Er 3+ when included into two different TiO 2 hosts: a polycrystalline and an amorphous host. The two host environments were produced by depositing two thin films with different Er 3+ concentration using radio-frequency magnetron sputtering. Structural analysis revealed the presence of the rutile and anatase phases in the polycrystalline film. Time-resolved and steadystate photoluminescence measurements evidenced the presence of two distinct local Er 3+ environments in the polycrystalline host. For the amorphous TiO 2 host, only one Er 3+ environment was observed, which differed from the two environments in the polycrystalline host. A method for extracting a fast and slow time-resolved emission spectrum from the two observed local environments in the polycrystalline host is also presented.

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