<i>In Situ</i> X-ray Absorption Near-Edge Structure Spectroscopy of ZnO Nanowire Growth During Chemical Bath Deposition

Chemical bath deposition (CBD) offers a simple and inexpensive route to deposit semiconductor nanostructures, but lack of fundamental understanding and control of the underlying chemistry has limited its versatility. Here we report the first use of <i>in situ</i> X-ray absorption spectroscopy during CBD, enabling detailed investigation of both reaction mechanisms and kinetics of ZnO nanowire growth from zinc nitrate and hexamethylenetetramine (HMTA) precursors. Time-resolved X-ray absorption near-edge structure (XANES) spectra were used to quantify Zn(II) speciation in both solution and solid phases. ZnO crystallizes directly from [Zn(H<sub>2</sub>O)<sub>6</sub>]<sup>2+</sup> without long-lived intermediates. Using ZnO nanowire deposition as an example, this study establishes <i>in situ</i> XANES spectroscopy as an excellent quantitative tool to understand CBD of nanomaterials.