Plant extract of Pulicaria undulata (L.) was used as both reducing agent and stabilizing ligand for the rapid and green synthesis of gold (Au), silver (Ag), and gold–silver (Au–Ag) bimetallic (phase segregated/alloy) nanoparticles (NPs). These nanoparticles with different morphologies were prepared in two hours by stirring corresponding metal precursors in the aqueous solution of the plant extracts at ambient temperature. To infer the role of concentration of plant extract on the composition and morphology of NPs, we designed two different sets of experiments, namely (i) low concentration (LC) and (ii) high concentration (HC) of plant extract. In the case of using low concentration of the plant extract, irregular shaped Au, Ag, or phase segregated Au–Ag bimetallic NPs were obtained, whereas the use of higher concentrations of the plant extract resulted in the formation of spherical Au, Ag, and Au–Ag alloy NPs. The as-prepared Au, Ag, and Au–Ag bimetallic NPs showed morphology and composition dependent catalytic activity for the reduction of 4-nitrophenol (4-NPh) to 4-aminophenol (4-APh) in the presence of NaBH₄. The bimetallic Au–Ag alloy NPs showed the highest catalytic activity compared to all other NPs.

Calcium sulfate is an important construction material. More than 1600 million square meters of interior surfaces are covered with plasterboards in Europe each year. Plasterboard is manufactured by transforming mined or recycled gypsum (CaSO₄ × 2 H₂O) to bassanite (CaSO₄ × ½H₂O) in a time‐ and energy‐consuming heating process. A fast and sustainable way to produce bassanite by solvent‐assisted milling, thereby eliminating the need for energy‐intensive dehydration, is described. The milling reaction is complete after ≈200 min. Kinetic studies revealed that gypsum crystals transform to bassanite by shear forces during milling. ¹H nuclear magnetic resonance (NMR) spectroscopic techniques and Fourier‐transform infrared spectroscopy (FT‐IR) show that the resulting bassanite nanocrystals are stabilized by surface functionalization with the auxiliary solvent methanol. Bassanite particles produced over extended milling times of 990 min form long‐term stable dispersions without stabilizers and no signs of precipitation. Addition of water to bassanite leads to instant agglomeration, followed by a phase change to gypsum. The dispersibility in volatile methanol and the elucidation of the crystallization mechanism allow also for applications of the bassanite nanocrystals in hybrid materials.