Nayak Alpana, Suresh K A
Raman Research Institute, Sadashivanagar, Bangalore, India.
J Phys Chem B. 2009 Mar 26;113(12):3669-75. doi: 10.1021/jp806600g.
We have studied the mechanical properties of films of a novel ionic discogen, pyridinium tethered with hexaalkoxytriphenylene (PyTp) and its complex with DNA (PyTp-DNA) using atomic force microscope (AFM). The PyTp and PyTp-DNA complex monolayer films were first formed at air-water interface and then transferred onto silicon substrates by Langmuir-Blodgett (LB) technique. For the mechanical properties, particularly to obtain elastic modulus, we have carried out nanoindentation measurements on the LB films of PyTp and also PyTp-DNA complex. The load versus indentation curves from the nanoindentation measurements were analyzed quantitatively using Hertz model. Our analysis yields Young's modulus values of 54 and 160 MPa for the PyTp and PyTp-DNA complex films, respectively. In addition, the LB films were imaged in the tapping mode AFM to obtain topography and phase images simultaneously. The energy dissipation maps were constructed from the phase images to determine qualitatively the variation in stiffness on the film surfaces. We find that the complex film exhibits a nonuniform surface with varying stiffness while the pure film exhibits a uniform surface.
我们使用原子力显微镜（AFM）研究了一种新型离子盘状液晶分子（吡啶鎓与六烷氧基三苯撑相连，PyTp）及其与DNA的复合物（PyTp-DNA）薄膜的力学性能。首先在气-水界面形成PyTp和PyTp-DNA复合物单层膜，然后通过朗缪尔-布洛杰特（LB）技术转移到硅基片上。对于力学性能，特别是为了获得弹性模量，我们对PyTp以及PyTp-DNA复合物的LB膜进行了纳米压痕测量。使用赫兹模型对纳米压痕测量得到的载荷-压痕曲线进行了定量分析。我们的分析得出，PyTp和PyTp-DNA复合物薄膜的杨氏模量值分别为54和160 MPa。此外，在轻敲模式AFM下对LB膜进行成像，以同时获得形貌和相位图像。从相位图像构建能量耗散图，以定性确定膜表面刚度的变化。我们发现，复合膜表现出表面刚度变化不均匀的情况，而纯膜表现出表面均匀的情况。
