Nanomaterials: Basic concepts and quantum models

The term “nanosystem” refers to a system with at least one spatial dimension scaled down to the nanometer-scale (<100 nm) and includes zerodimensional systems (such as metallic, semiconducting and ceramic nanoparticles), one-dimensional systems (such as nanowires, nanotubes and nanorods) and twodimensional structures (thin films or plates). The fascinating properties of materials at the nanoscale are continuing to attract the scientific interest in many research fields at both applicative and fundamental levels. The impossible to comprehensively review large number of reports and results available in the literature demonstrates the complexity in describing all the functionalities offered by the nanosystems as well as their properties as related to their fabrication approaches apart from departure from bulk form. To be able to gain insight into the potentialities and new future perspectives offered by the nanoworld and nanotechnology, knowledge and understanding of the physical fundamentals is a necessary starting point. In this review paper, we consider and discuss the spectroscopy of nanomaterials by pointing out differences and breaking points as compared to the bulk counterparts, the importance of the surfaces, the characteristic length-scales (De Broglie wavelength, Fermi wavelength and exciton Bohr radius) that define various confinement regimes, the physics underlying the formalism to calculate the electronic dispersion of the low-dimensionality systems and the technological benefits on the excitonic binding energy implied by low-dimensionality (zero-, one- and twodimensionaity). The presented discussion aims at laying a foundation to further studies for a reader new to the field of nanomaterials.