Systematic Exploration of the Synthetic Parameters for the Production of Dynamic VO(M1).

Thermochromic dynamic cool materials present a reversible change of their properties wherein by increasing the temperature, the reflectance, conductivity, and transmittance change due to a reversible crystalline phase transition. In particular, vanadium (IV) dioxide shows a reversible phase transition, accompanied by a change in optical properties, from monoclinic VO(M1) to tetragonal VO(R). In this paper, we report on a systematic exploration of the parameters for the synthesis of vanadium dioxide VO(M1) via an easy, sustainable, reproducible, fast, scalable, and low-cost hydrothermal route without hazardous chemicals, followed by an annealing treatment. The metastable phase VO(B), obtained via a hydrothermal route, was converted into the stable VO(M1), which shows a metal-insulator transition (MIT) at 68 °C that is useful for different applications, from energy-efficient smart windows to dynamic concrete. Within this scenario, a further functionalization of the oxide nanostructures with tetraethyl orthosilicate (TEOS), characterized by an extreme alkaline environment, was carried out to ensure compatibility with the concrete matrix. Structural properties of the synthesized vanadium dioxides were investigated using temperature-dependent X-ray Diffraction analysis (XRD), while compositional and morphological properties were assessed using Scanning Electron Microscopy, Energy Dispersive X-ray Analysis (SEM-EDX), and Transmission Electron Microscopy (TEM). Differential Scanning Calorimetry (DSC) analysis was used to investigate the thermal behavior.