Distinctive electronic structure, unusual magnetic properties and large enhancement in SERS of 1D gallium nanoribbons achieved by doping calix[6]arene

Abstract

The present work provides a novel route for forming one-dimensional (1D) gallium (Ga) nanoribbon materials with a host molecule calix[6]arene (CA-6) as a template by a facile, one-step and low temperature chemical bath method. Field-emission scanning electron microscopy and transmission electron microscopy showed that the uniform 1D Ga nanoribbon material (Ga-a) can be constructed only in the presence of CA-6, and the formation of ribbon structures is highly dependent on doping ratios and deposition times. Our data indicate that the unusual effect of CA-6 is due to a combination of two factors: a high density of OH groups in the outer surface of its cavity and an appropriate cavity diameter. Especially, the uniform 1D Ga nanoribbon material exhibits a distinct electronic structure and very rare magnetic behaviour when compared to those 3D Ga materials obtained by means of other host molecules: calix[4]arene, γ-cyclodextrin and 18-crown-6. For example, of all the Ga materials, the uniform 1D nanoribbon material has the lowest electron density of Ga core levels in light of X-ray photoelectron spectroscopy analysis. This result suggests that there is a stronger molecule–atom interaction between Ga atoms and CA-6 molecules compared with those in other host–guest systems. More importantly, the uniform 1D Ga nanoribbon material exhibits a magnetic transformation from a diamagnetic to a paramagnetic state under the influence of an applied field, which is completely different from those of all the 3D Ga materials and all the irregular Ga nanoribbon materials. Such a transformation is novel in metals and particularly useful in the chemistry of materials since it allows dramatic modifications of magnetic properties of metal nanocrystals. Finally, a strong surface-enhanced Raman scattering of the uniform 1D Ga nanoribbon material has been observed for organic molecules adsorbed on their surface. Taken together, we believe this work opens a new channel for development of 1D metal-based nanomaterials.