All Publications


  • Anisotropy and anharmonicity in polystyrene stable glass JOURNAL OF CHEMICAL PHYSICS Raegen, A. N., Zhou, Q., Forrest, J. A. 2020; 153 (21): 214508

    Abstract

    We have used ellipsometry to characterize the anisotropy in stable polymer glasses prepared by physical vapor deposition. These measurements reveal birefringence values (as measured by the magnitude of in-plane vs out-of-plane refractive index) less than 0.002 in vapor-deposited polystyrenes with N from 6 to 12 and with fictive temperatures between 10 K and 35 K below the Tg values. We have measured the thermal expansivity of these stable glasses and compared to ordinary rejuvenated glass. The thermal expansivity of the stable glasses is less than that of ordinary glass with a difference that increases as the fictive temperature Tf decreases.

    View details for DOI 10.1063/5.0032153

    View details for Web of Science ID 000597328700003

    View details for PubMedID 33291898

  • Ultrastable monodisperse polymer glass formed by physical vapour deposition NATURE MATERIALS Raegen, A. N., Yin, J., Zhou, Q., Forrest, J. A. 2020

    Abstract

    Stable glasses prepared by vapour deposition are an analogue of glassy materials aged for geological timescales. The ability to prepare such materials allows the study of near-ideal glassy systems. We report the preparation and characterization of stable glasses of polymers prepared by physical vapour deposition. By controlling the substrate temperature, deposition rate and polydispersity, we prepared and characterized a variety of stable polymer glasses. These materials display the kinetic stability, low fictive temperatures and high-density characteristic of stable glasses. Extrapolation of the measured transformation times between the stable and normal glass provides estimates of the relaxation times of the equilibrium supercooled liquid at temperatures as much as 30 K below the glass transition temperature. These results demonstrate that polymer stable glasses are an exciting and powerful tool in the study of ultrastable glass and disordered materials in general.

    View details for DOI 10.1038/s41563-020-0723-7

    View details for Web of Science ID 000546427400004

    View details for PubMedID 32632279

  • A highly sensitive double-layer structured nanodevice for moisture induced power generation NANOTECHNOLOGY Zhou, Q., Hui, Z., Xiao, M., Zhou, N. Y. 2020; 31 (26): 265401

    Abstract

    With the increasing global energy demand, traditional energy sources are gradually failing to meet society's needs while also having a potential of being harmful to the environment. As such, energy generating technologies capable of converting ubiquitous environmental energy into usable forms, such as electricity, have received increasing attention. In this research, a power generating device composed of a graphene (G) and titanium dioxide nanowire (TiO2 NWs) double-layer structure is prepared by an electrophoretic deposition method. Since both materials have special nanochannel structures and non-zero zeta potential, they can convert environmental energy into electricity through the diffusion, ionization, and natural evaporation of water. Furthermore, the efficiency of this novel sensor is much higher than their respective single-layer devices. By application of only 6 μl of water, the open circuit voltage (UOC) generated on the G-TiO2 sensor is as high as 1.067 ± (0.008) V. In comparison, TiO2 NWs single layer can only generate a UOC around 500 mV, and graphene itself can only produce a UOC no more than 250 mV under the same condition. Additionally, the effect of different deposition times of graphene on the surface morphology and thickness of graphene film is explored, and the effects of these changes in microstructure on performance is discussed in depth. Aside from power generation, the high sensitivity of the device to different volumes of water brings its use in the detection of trace amounts of water, and its high efficiency of energy conversion suggests a potential application as a power supply. This research not only provides a satisfactory candidate for inexpensive and efficient evaporative power generation, but also builds a foundation for developing new, intelligent, and self-powered electronic technologies.

    View details for DOI 10.1088/1361-6528/ab7fcd

    View details for Web of Science ID 000528541500001

    View details for PubMedID 32168494