Department of Materials Science and Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA.
ACS Appl Mater Interfaces. 2010 Mar;2(3):813-20. doi: 10.1021/am900883f.
Nanoparticles are indispensable ingredients of solution-processed optical, dielectric, and catalytic thin films. Although solution-based methods are promising low-cost alternatives to vacuum methods, they can have significant limitations. Coating uniformity, thickness control, roughness control, mechanical durability, and incorporation of a diverse set of functional organic molecules into nanoparticle thin films are major challenges. We have used the electrostatic layer-by-layer assembly technique to make uniform, conformal multistack nanoparticle thin films for optical applications with precise thickness control over each stack. Two particularly sought-after optical applications are broadband antireflection and structural color. The effects of interstack and surface roughness on optical properties of these constructs (e.g., haze and spectral response) have been studied quantitatively using a combination of Fourier-transform methods and atomic force microscopy measurements. Deconvoluting root-mean-square roughness into its large-, intermediate-, and small-scale components enables enhanced optical simulations. A 4-stack broadband antireflection coating (<0.5% average reflectance in the visible range, and 0.2% haze) composed of alternating high-index (n approximately 1.96) and low-index (n approximately 1.28) stacks has been made on glass substrate. Films calcinated at 550 degrees C endure a one-hour-long cloth cleaning test under 100 kPa normal stress.
纳米粒子是溶液处理的光学、介电和催化薄膜中不可或缺的成分。虽然基于溶液的方法是有前途的低成本替代真空方法，但它们可能有显著的局限性。涂层均匀性、厚度控制、粗糙度控制、机械耐久性以及将各种功能有机分子掺入纳米粒子薄膜中是主要挑战。我们使用静电层层组装技术来制造用于光学应用的均匀、共形多堆叠纳米粒子薄膜，每个堆叠的厚度都可以精确控制。两种特别受欢迎的光学应用是宽带抗反射和结构色。通过傅里叶变换方法和原子力显微镜测量的组合，对这些结构的光学性质（例如雾度和光谱响应）的层间和表面粗糙度的影响进行了定量研究。将均方根粗糙度分解为大、中和小尺度分量可以增强光学模拟。在玻璃衬底上制备了由交替的高折射率（n 约为 1.96）和低折射率（n 约为 1.28）堆叠组成的 4 堆叠宽带抗反射涂层（可见光范围内平均反射率<0.5%，雾度<0.2%）。在 550°C 下煅烧的薄膜在 100 kPa 正常压力下经受一小时的布清洁测试。
