Blown bubble assembly of ultralong 1D bismuth sulfide nanostructures with ordered alignment and shape control

Recently, semiconducting chalcogenide nanostructures have attracted intense attention due to their excellent properties and broad applications, especially metal chalcogenides in the form of A₂(V)B₃(VI). Here we synthesized one-dimensional (1D) bismuth sulfide (Bi₂S₃) nanostructures with a length of more than 100 μm via a one-step hydrothermal method, and found that the reaction temperature and the alkali concentration play vital roles in the morphology of the 1D nanostructures. Since the as-synthesized Bi₂S₃ nanostructures were disordered in powder form, it is necessary to align them with ordered orientation and uniform distribution before further application. A blown bubble method was specifically applied to align these ultralong 1D nanostructures, and the assembly mechanism was also deeply analyzed, including the drift of nanostructures in the bubble film thickness direction, the relationship between (nanowire) NW spacing and array density, and the angle deviation of aligned arrays assembled from different bubble solutions. Interestingly, the initial straight Bi₂S₃ NWs could also be converted into buckled nanosprings (NSs) with regular pitches during the assembly process, and different NS formation stages were observed. A possible deformation mechanism or load bearing model of the wavy NS was proposed and verified, and the Young's modulus of an individual NW was figured out for the first time. After annealing under a N₂ atmosphere, the aligned Bi₂S₃ NWs embedded in the bubble film were exposed, and the clean arrays were fabricated into functional optoelectronic devices such as photodetectors with a high performance.