Effects of Fluid Confinement and Temperature in Supported Acetophenone Films
Effects of Fluid Confinement and Temperature in Supported Acetophenone Films
复制标题
流体限制和温度对负载苯乙酮薄膜的影响
DOI：
10.1021/acs.jpcc.8b04051
复制
发表时间：
2018
期刊：
影响因子：
--
通讯作者：
Shaw, Scott K.
中科院分区：
文献类型：
--
作者：
Nania, Samantha L.;Wrona, Jaclyn;Shaw, Scott K.
固体-液体相变被认为在物质的体相中很好地理解，但在薄膜或界面体积中，熔化和冻结转变可能表现出与预期行为的显著偏离。在这里，我们展示了分子流体苯乙酮薄膜（50-500 nm）中的多个固-液相变。转变是由几何约束和温度驱动的，如光谱所表征的那样。流体膜约束是通过系统地改变支撑膜的厚度来控制的，相同的膜通过冷却-加热循环生成具有明显不同分子环境的非晶或结晶膜。具体来说，多个温度循环显示出明显的条件依赖性，其中相变可能会或可能不会在温度循环中显示出红外吸收曲线的显着变化，表明不同的晶体和液体相。由于薄膜取样几何形状的高度受限性质，也观察到过冷的显著影响。有趣的是，作为薄膜温度函数记录的光谱曲线显示了分子重排序相变的清晰证据，这与恒温下变厚度薄膜的观察结果相似。光谱吸收曲线的变化证实了约束诱导的晶体有序，并提供了分子约束效应可以从表面延伸到100 nm以上的证据，这比传统上接受的“界面”体积要大得多。最终，液体膜内扩展的晶体有序可以为调整设计界面的物理性质提供重要的新途径。
Solid–liquid phase transitions are thought to be well understood in bulk phases of matter, but in thin films or interfacial volumes, melting and freezing transitions can exhibit significant departures from expected behaviors. Here, we show multiple solid–liquid phase transitions in thin films (50–500 nm) of the molecular fluid acetophenone. Transitions are driven by both geometric confinement and temperature, as characterized by spectroscopy. Fluid film confinement is controlled by systematic variation of the supported film thicknesses, and the same films are passed through cooling–heating cycles to generate amorphous or crystalline films with distinctly different molecular environments. Specifically, multiple temperature cycles reveal a distinct conditioning dependence, wherein phase transitions may or may not exhibit significant changes in the infrared absorption profile over the temperature cycle, indicating distinct crystalline and liquid-like phases. Significant effects of supercooling are also observed as a result of the highly confined nature of the thin-film sampling geometry. Interestingly, the spectral profiles recorded as a function of film temperature show clear evidence of molecular reordering phase transitions, which is similar to observations in variable thickness films held at constant temperature. The changes in spectral absorption profiles confirm the confinement-induced crystalline ordering and provide evidence that molecular confinement effects can extend beyond 100 nm from a surface, which is much larger than conventionally accepted “interfacial” volumes. Ultimately, the extended crystalline ordering within liquid films could offer important new avenues to tune the physical properties of designer interfaces.
登录
查看更多内容
当表面和界面区域重叠时，观察薄液膜中的液体到层状的转变。
DOI：
--
发表时间：
2008
期刊：
Physical review. E, Statistical, nonlinear, and soft matter physics
影响因子：
--
作者：
D. R. Lee;P. Dutta;Chung
通讯作者：
Chung
DOI：
--
发表时间：
1990
期刊：
影响因子：
--
作者：
J. V. Alsten;S. Granick
通讯作者：
S. Granick
使用原子级光滑表面研究摩擦学
DOI：
--
发表时间：
1990
期刊：
影响因子：
--
作者：
J. V. Alsten;S. Granick
通讯作者：
S. Granick
苯乙酮液膜的结构变化作为纳米级厚度的函数。
影响因子：
3.9
作者：
Samantha L. Nania;S. Shaw
通讯作者：
S. Shaw
影响因子：
3.3
作者：
Faria, Luiz F. O.;Matos, Jivaldo R.;Ribeiro, Mauro C. C.
通讯作者：
Ribeiro, Mauro C. C.