Changes in the size and geometric shape of nanoparticles allow for the manipulation of semiconductor properties without altering their chemical composition. However, a challenge remains: depending on the synthesis method, the size distribution of the nanoparticles can vary.
The use of nanotube molds to form selenium nanowires is part of a broader strategy that employs nanostructured templates to control the growth of one-dimensional nanomaterials.
Although selenium naturally crystallizes into elongated structures due to its anisotropic nature, templates such as carbon nanotubes (CNTs), anodic aluminum oxide, or other hollow nanostructures enable precise control over the nanowire’s unidirectional growth, size, orientation, and uniformity, while also protecting the material during formation. These core–shell structures, with a selenium core and a protective nanotube shell, have applications in nanoelectronics, photoconductors, and energy storage.
British researchers discovered distinct structural phases of selenium when confined within carbon and boron nitride nanotubes, observing remarkable structural plasticity in nanowires with diameters ranging from 0.4 to 3.0 nm. The experiment used one sample of boron nitride nanotube (BNNT) and four carbon nanotube (CNT) samples of different diameters, all under identical experimental conditions. Selenium was sublimed to fill the nanotubes, forming Se@CNT and Se@BNNT structures, in order to study exclusively the effect of nanotube diameter on the resulting selenium structure.
They found that the bandgap width of these nanowires, between 2.2 and 2.5 eV, depends non-monotonically on the diameter of the nanotube. This is due to conformational distortions in the selenium chains counteracting quantum confinement effects at sub-nanometric scales.
The authors developed a one-dimensional phase diagram that predicts the atomic structure of selenium as a function of the nanotube diameter, regardless of the host nanotube’s chemical composition. This demonstrates that confinement within nanotubes enables precise tuning of the structure and electronic properties of selenium. The materials were characterized using advanced electron microscopy and electron energy loss spectroscopy (EELS) to determine the bandgaps.
These nanoscale discoveries pave the way for the development of advanced, miniaturized, tunable, and flexible electronic components, such as transistors, optical sensors, and photovoltaic systems.
For further details, go to: Advanced Materials