Laboratory of semiconducting and photoactive "post-graphene" 2D materials, nanomaterials and nanocomposites

可见光的波长在400纳米到700纳米之间，它是光学科学的核心，因为它很容易以多种不同的方式产生、反射、传输和检测。事实上，日常生活中可用的任何可见光光学仪器都利用辐射，这些辐射在产生辐射的光源的大小上远距离传播。不幸的是，这种“远场”光学在分辨非常小的物体的能力上受到衍射的固有限制，分辨能力不比波长小得多。这表明远场可见光不适合于纳米材料、量子点和二维(2D)材料的精确分析，其中1-100 nm以下的空间限制是关键，并在新物理和新器件方面具有独特突破的潜力。限制效应至关重要的新设备的例子包括：先进的太阳能电池，它将使能量转换变得更清洁，数字存储设备，使我们的大数据社会变得更简单，纳米多孔水过滤器，以清洁我们的环境，以及散热器，以提高我们的便携式电子产品的寿命。我们已经掌握了在内部制造许多此类设备的技能，作为一个物理学家团队，我们正在使用概念验证设备原型来更好地了解包含在其中的特定材料的性能。我们研究的最基本方面集中在利用纳米光源附近产生的近场可见光辐射来克服衍射，探测纳米尺度上的光与物质的相互作用，并精确推断特定2D材料、纳米材料和纳米复合材料的性质。我们在孔径型扫描近场光学显微镜(SNOM)方面拥有独特的专业知识，这是一种近场技术，在其中钻入亚波长小孔的原子力显微镜(AFM)悬臂被用来产生局域近场辐射，并在该光源附近扫描样品。因此，到目前为止只在远场实现的许多光学技术将扩展到近场。石墨烯是一种完全由碳原子形成的2D材料，它的发现激发了人们对沿z轴限制的平板材料潜力的极大兴趣，但下一代“后石墨烯”2D材料仍在等待最合适的工具来分析、操纵和整合到概念验证设备中，以高精度地了解它们的光学性质。这里将特别强调那些与石墨烯不同的二维材料、纳米材料和纳米复合材料，它们具有半导体和光活性，如碳量子点、气凝胶和二维过渡金属氧化物和硫属化合物。能够分析这些系统的SNOM工具令人兴奋，是培养下一代多样化、包容性和高素质纳米光学和纳米物理人才的理想选择。

Visible light, with wavelength between 400 nm and 700 nm, is at the core of optical sciences because it is simple to generate, reflect, transmit and detect it in so many different ways. Virtually any visible-light optical instrument available in everyday's life utilizes radiation that propagates at large distances over the size of the source that generates it. Unfortunately, this "far-field" optics is inherently limited by diffraction in the ability to resolve very small objects, with a resolving power no much less than a wavelength. This indicates that visible light in the far-field is unsuitable for the precise analysis of nanomaterials, quantum dots, and two-dimensional (2D) materials, in which spatial confinement below 1-100 nm is critical and has the potential of unique breakthroughs in terms of new physics and devices. Examples of new devices in which confinement effects are vital include: advanced solar cells that will make energy conversion cleaner, digital memory devices to make our big-data society simpler, nanoporous water filters to clean our environment, and heat spreaders to improve the lifetime of our portable electronics. We have acquired the skills to fabricate many of these devices in-house and, as a team of physicists, we are using proof-of-concept device prototypes to better understand the performance of specific materials incorporated into them. The most fundamental aspects of our research focus on the use of "near-field" visible radiation generated in the proximity of a nano-optical source to overcome diffraction, probe light-matter interaction at the nanoscale, and precisely infer the properties of specific 2D materials, nanomaterials and nanocomposites. We have unique expertise in aperture-type scanning near-field optical microscopy (SNOM) a near-field technique in which atomic force microscopy (AFM) cantilevers with sub-wavelength apertures drilled into them are used to generate localized near-field radiation and scan a sample in the close proximity of this source. Many optical techniques so far implemented only in the far-field will thus be extended to the near-field. The discovery of graphene, a 2D material entirely formed by carbon atoms, has spurred tremendous interest towards the potential of flat materials with confinement along the z-axis, but the next-generation of "post-graphene" 2D materials is still awaiting the most appropriate tools to be analyzed, manipulated and incorporated into proof-of-concept devices to understand their optical properties with high precision. Here, special emphasis will be placed on those 2D materials, nanomaterials and nanocomposites that, differently from graphene, exhibit semiconducting and photoactive properties, such as carbon quantum dots, aerogels, and 2D transition metal oxides and chalcogenides. SNOM tools capable of analyzing these systems are exciting and ideal to train the next-generation of diverse, inclusive and highly-qualified personnel in nano-optics and nano-physics.