A completely solid-state mechanochemical synthesis of silver nanoparticles overcoming the problem with water insolubility of lichen metabolites hampering their use for the classical green synthesis in water is shown herein. Four lichen species (Xanthoria elegans, Cetraria islandica, Usnea antarctica, and Leptogium puberulum) and AgNO3 were used as reducing agents and Ag(0) precursor, respectively. The reaction progress was rapid in the first two cases, whereas in the case of U. antarctica and L. puberulum, a significant amount of AgNO3 could still be detected after 6 h of milling. The products with a higher content of Ag(0) were shown to undergo a backward transformation documented by increasing content of AgNO3 with storage time; however, the repeated formation of Ag(0) could be observed upon remilling. Transmission electron microscopy analysis has shown bimodal nanocrystallite size distribution in all cases. However, the finer fraction was more abundant in the case of silver nanoparticles prepared using lichens with stronger reducing ability (X. elegans and C. islandica). All the products are excellent antibacterial agents. Whereas the as-received products exhibited higher activity against E. coli, the remilled samples were more active against S. aureus.

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The present study demonstrates a scalable approach towards the pure Cu2ZnSnS4 (CZTS) phase starting from microsized Cu, Zn, Sn, and S mixture or a combination of nanosized CuS, SnS plus microsized Zn and S. A set of mechanochemical reactions was carried out in an industrial vibratory mill. The pure CZTS phase was obtained after 360 minutes of milling with an average crystallite size of 15 nm for both mixtures. The kinetics of CZTS formation was investigated following the X‐ray diffractometry (XRD) patterns of the reaction mixtures milled for various times. The morphology of particles and their elemental composition was studied by scanning electron microscopy (SEM)/transmission electron spectroscopy (TEM) and EDX analysis. Photoelectron spectroscopy (XPS) analysis showed the presence of Cu+, Zn2+, Sn4+, and S2− species on the surface of CZTS with only minor oxidation. Thermal stability of the synthesized materials was followed by thermogravimetric analysis. Based on UV‐VIS measurements, the calculated bandgap Eg = 1.44 to 1.50 eV of the synthesized CZTS samples is acceptable for photovoltaic application. Moreover, the applied mechanochemical approach can produce 100 to 500 g of CZTS in a batch mode experiment that is 10 to 50 times higher amount as the throughput of laboratory planetary mills. Hypothetically, in the applied industrial eccentric vibratory mill, the amount can be increased up to 50 kg per one batch.

Stannite Cu2FeSnS4 and kesterite Cu2ZnSnS4 were synthesized by an eco-friendly ball-milling method in an industrial mill. Both synthesized sulfides represent perspective materials in solar cell technology. Several characterization methods have been applied to determine the course of solid state mechanochemical reactions leading to the synthesis of potential chalcogenide solar cell absorbers. The phase and surface composition, solid state kinetics, and surface morphology of these quaternary sulfides were elucidated by the methods of X-ray diffractometry, X-ray photoelectron spectroscopy, Soxhlet analysis, and scanning electron microscopy. The application of eccentric vibration mills for these syntheses constitutes the big challenge for researchers in the field of photovoltaics in their permanent effort in scaling up new materials and processes.