Advances in the synthesis and scalable manufacturing of single-walled carbon nanotubes (SWCNTs) remain critical to realizing many important commercial applications. Here we review recent breakthroughs in the synthesis of SWCNTs and highlight key ongoing research areas and challenges. A few key applications that capitalize on the properties of SWCNTs are also reviewed with respect to the recent synthesis breakthroughs and ways in which synthesis science can enable advances in these applications. While the primary focus of this review is on the science framework of SWCNT growth, we draw connections to mechanisms underlying the synthesis of other 1D and 2D materials such as boron nitride nanotubes and graphene.

The Raman spectrum of gallium oxide $\left(\beta \text{-}{\mathrm{Ga}}_2{\mathrm{O}}_3\right)$ nanowires with [001] growth direction is identical to that of the bulk ${\mathrm{Ga}}_2{\mathrm{O}}_3$ [Y. C. Choi et al. Adv. Mater. 12, 746 (2000)] while that of $\beta \text{-}{\mathrm{Ga}}_2{\mathrm{O}}_3$ nanowires with $\left[40\overline{1}\right]$ growth direction is redshifted by $4\text{–}23{\mathrm{cm}}^{-1}$ [Y. H. Gao et al. Appl. Phys. Lett. 81, 2267 (2002)]. Here we report the Raman and Fourier transform infrared spectra of $\beta \text{-}{\mathrm{Ga}}_2{\mathrm{O}}_3$ nanowires with [110] growth direction which is blueshifted relative to the bulk spectra by $\sim 10\text{–}40{\mathrm{cm}}^{-1}$ . Based on a first principles calculation of the strain dependence of Raman mode frequencies in bulk $\beta \text{-}{\mathrm{Ga}}_2{\mathrm{O}}_3$ , we correlate the observed frequency shifts to growth-direction-induced internal strains in the nanowires.