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Manipulating properties of matter at the nanoscale is the essence of nanotechnology, which has enabled the realization of quantum dots, nanotubes, metamaterials, and two-dimensional materials with tailored electronic and optical properties. Two-dimensional semiconductors have revealed promising perspectives in nanotechnology. However, the tunability of their physical properties is challenging for semiconductors studied until now. Here we show the ability of morphological manipulation strategies, such as nanotexturing or, at the limit, important surface roughness, to enhance light absorption and the luminescent response of atomically thin indium selenide nanosheets. Besides, quantum-size confinement effects make this two-dimensional semiconductor to exhibit one of the largest band gap tunability ranges observed in a two-dimensional semiconductor: from infrared, in bulk material, to visible wavelengths, at the single layer. These results are relevant for the design of new optoelectronic devices, including heterostructures of two-dimensional materials with optimized band gap functionalities and in-plane heterojunctions with minimal junction defect density.

In this letter, we demonstrate that microphotoluminescence may be combined with optical trapping for effective optical characterization of single target InP semiconductor nanowires in suspension. Using this technique, we may investigate structural properties of optically trapped nanowires, such as crystalline polytypes and stacking faults. This arrangement may also be used to resolve structural variations along the axis of the trapped nanowire. These results show that photoluminescence measurements may be coupled with optical tweezers without degrading the performance of the optical trap and provide a powerful interrogation tool for preselection of components for nanowire photonic devices.

We apply diffraction-limited confocal optical microscopy to spatially resolve, a single self-assembled semiconductor quantum dot. We report for the first time, on the low-temperature photoluminescence spectrum of such a single dot and on its excitation intensity dependence. We demonstrate that sharp spectral lines, in the dots emission spectrum, are due to optical transitions between discrete multiexcitonic states confined within the dot. Under high excitation power, once the limited number of discrete exciton levels are fully occupied, spectrally broad emission bands are formed due to transitions which involve continuum excitonic states. In addition, we show that the single exciton recombination is almost forbidden in this InAs self-assembled quantum dot.