Revealing the Flexibility of Inorganic Sub-Nanowires by Single-Molecule Force Spectroscopy

Sub-nanowires (SNWs), similar to 1 nm in thickness, possess an inorganic skeleton but display characteristics akin to those of carbon-carbon backbone polymers, such as flexibility, adhesion, gelation, self-assembling behaviors, and shear-thinning properties. Despite this, the underlying mechanism for these polymer-like properties remains unexplored. This study investigates the origin of SNWs' unique behavior from three distinct perspectives. Utilizing single-molecule force spectroscopy, we quantitatively measure the persistence lengths of SNWs, which provide a measure of flexibility. In addition, we evaluate the macroscopic mechanical properties of SNW materials, including the strength of electrospun fibers and gelation in solutions. Finally, we apply molecular dynamics to simulate the behaviors of SNWs under elongating and rotating conditions. The three perspectives mentioned above in the study collectively provide evidence for the structure-activity relationship of nanomaterials: a freely rotated backbone results in a flexible SNW, which is inclined to bend and entangle to form gels in solutions. Conversely, a stiff backbone leads to a rigid SNW, which induces strong fibers.