Photochemical Synthesis of Particulate Main-Group Elements and Compounds

Particulate main-group elements (As-0, Sb-0, Bi-0, Pb-0, Se-0, Te-0) and compounds (Bi4Te3, SbxBi1-x with 0 <= x <= 1) are obtained via photoinitiated reduction under UV irradiation. The synthesis of Bi-0 and Se is exemplarily studied in detail. Here, meso- to micrometer-scaled particles are obtained with mean diameters of 81(11) nm (Bi-0) and 1.15(18) mu m (Se-0) in the absence of specific stabilizers that allow controlling the particle growth. In contrast, the particle diameter is significantly reduced in the presence of specific stabilizers (e.g., polyvinylpyrrolidone/PVP for Bi-0, 2-mercaptoacetid acid/MAA for Se-0). Now, even the nanoregime is reached with mean diameters of 4(2) nm (Bi-0) and 290(39) nm (Se-0). The photochemical synthesis is easy to perform (i.e., aqueous solution/suspension, room temperature, conventional chlorides/oxides as starting materials) and leads to a homogeneous particle nucleation, only initiated by UV irradiation as an external physical trigger. The resulting particulate main group elements and compounds are characterized by electron microscopy (SEM), dynamic light scattering (DLS), X-ray powder diffraction (XRD), and energy-dispersive X-ray (EDX) analysis. The mechanism of the light-initiated reaction can be clarified by polymerization experiments to involve radicals as intermediate species.