Photo induced Force Microscopy (PiFM): Nanoscale Topography and Vibrational Spectroscopy

几乎我们日常生活的方方面面，从摩擦到粘合，从LED照明到显示屏，从腐蚀到通过细胞壁的药物输送，都依赖于固体外层与环境之间的界面。我们知道，控制固体和气体、液体或固体之间相互作用的“外层”通常不到几纳米(纳米)厚，通常与最外层的原子或分子一样小。这意味着只有很少的表面材料可以看到，例如，在一个1厘米的固体立方体中，每1亿个原子中只有一个在表面。这使得研究这些界面变得非常困难。表面科学已经开发出许多能够检查原子外层的不同技术，但我们的知识仍然存在相当大的差距。特别是，我们不能看到分子组成在非常小的尺度上(即千分之一毫米)如何变化，尽管我们确实知道这种局部差异对大多数界面的行为至关重要。我们可以从从表面反射的光中得到表面分子组成的平均值，这是几毫米范围内的平均值，但这种方法不能用于所需的最小尺度。在过去的30年里，原子力显微镜(AFM)等扫描探针显微镜彻底改变了我们对界面形貌的理解；现在，人们通常可以分辨出小到几纳米的特征形状，并研究这种局部结构如何影响界面的行为。然而，形状只是故事的一部分，局部化学成分和电子相互作用也是至关重要的。有了这个提议，我们将为英国研究人员建立一个设施，能够以10 nm的横向分辨率同时确定地形、局部分子组成和局部电子相互作用。这项技术被称为光诱导力显微镜(PiFM)，可以在AFM地图上的每一点提供完整的红外(IR)光谱。红外光谱是化学家用来识别分子物种的标准工具(例如，红外光谱的一个版本被用来识别火星上是否存在甲烷，更有争议的是，金星大气中可能存在磷化氢)。红外光谱与原子力显微镜以如此高的分辨率相结合，将为研究各种科学领域提供新的、非常重要的见解，包括表面抗菌涂层、用于照明和显示的量子纳米晶体、医疗植入物材料、水净化催化剂以及应用于电工钢的涂层缺陷或失败的原因。了解这些过程将有助于研究人员开发出更具弹性、更可持续、性能更好的材料。

Virtually every aspect of our everyday lives, from friction to adhesion, from LED lighting to display screens, and from corrosion to drug delivery through cell walls, depends upon the interface between the outer layer of a solid and the environment. We know the "outer layer" that governs the interactions between a solid and a gas, liquid, or solid, is usually less than a couple of nanometers (nm) thick and often as little as the very outermost layer of atoms or molecules. This means that there is simply very little surface material there to see, in a 1 cm cube of solid for example, only 1 atom in 100 million is at the surface. That makes studying these interfaces very difficult. Surface science has developed many different techniques capable of examining the outer layer of atoms, but there remain considerable gaps in our knowledge. In particular, we cannot see how the molecular composition changes at very small scales (i.e. < 1000th of a mm) although we do know that such local differences are critical to the behaviour of most interfaces. We can obtain an idea of the molecular constituents of the surface as an average over areas of a few millimeters from bouncing light off the surface, but this approach cannot be used at the smallest scales needed. In the last 30 years, scanning probe microscopy such as atomic force microscopy (AFM) have revolutionized our understanding of the topography of interfaces; it is now routinely possible to resolve the shape of features as small as a few nm and to study how such local structures affect the behaviour of the interface. The shape is only part of the story however, the local chemical composition and electron interactions are crucial too. With this proposal, we will establish a facility for UK researchers that is capable of determining the topography, local molecular composition and local electronic interactions simultaneously with <10 nm lateral resolution. The technique is called Photo-induced Force Microscopy (PiFM) and can provide a full infrared (IR) spectrum at every point on an AFM map. Infrared spectroscopy is a standard tool used by chemists to identify molecular species (a version of IR was used to identify the presence of methane on Mars for example, and more controversially the possible presence of phosphine in the atmosphere of Venus). The combination of infrared spectroscopy with atomic force microscopy at such high resolution will provide a new and very important insight into areas of science as diverse as antibacterial coatings on surfaces, quantum nanocrystals for lighting and display, materials for medical implants, catalysts for water purification and the cause of defects or failure in the coatings applied to electrical steels. Understanding these processes will help researchers develop more resilient and sustainable materials with better performance.