Mechanochemically Assisted Synthesis of Cu–Ag Microflakes

In this work, a simple, inexpensive, and eco-friendly synthesis method of Cu−Ag microflakes has been developed. Firstly, Cu nanoparticles were synthesized by the reduction of copper nitrate in ethylene glycol at 180 °C in the presence of NaOH. The as-synthesized Cu powder was then dispersed in a mixture of ethyl alcohol and a dispersant followed by the mechanochemical treatment of the dispersion in a ball mill resulting in the formation of Cu flakes of approximately 0.2 μm thick and 2.7 μm lateral size. Next, by adding AgNO3 dissolved in H2O into the Cu particle dispersion, the bimetallic Cu−Ag microflakes were prepared. The particles so prepared were investigated by X-ray phase analysis and electron microscopy. It was shown that the Cu−Ag bimetallic particles were also flake-like in shape and similar in size to the original Cu microflakes. The effect of synthesis conditions, including parameters of mechanochemical processing, on thickness, size, and uniformity of the bimetallic microflakes was studied. The results obtained in this study were compared with those obtained by wet chemical synthesis alone. The flake-like Cu–Ag particles are supposed to be used in the manufacture of conductive pastes, adhesives, and composites for printed electronics

Features of the formation of conductive films during thermal and laser sintering of silver nanoparticles stabilized by an ethoxylated carboxylic acid

Silver nanoparticles (Ag NPs) of ~ 6 nm in size were synthesized by the reduction of silver 2-[2-(2-methoxyethoxy)ethoxy]acetate by benzyl alcohol acting both as the solvent and as the reducer. The as-synthesized Ag NPs were dispersed in a mixture of nontoxic solvents with different boiling temperatures (butanol and propylene glycol ethers) to prepare ink. The ink was spin-coated on polyimide films and processed with thermal and laser sintering. After thermal sintering, the silver films have a non-uniform structure and contain many voids, causing their resistivity to be quite high (28 µΩ×cm). Laser sintering of the Ag NPs inks spin-coated on a polyimide film using a fiber laser operating at a wavelength of 1.064 µm in a pulse-periodic mode results in a uniform film structure, almost without voids, with a lower resistivity of 2.3 µΩ×cm. Laser sintering in this case is a promising method to fabricate conductive patterns on various substrates, including polymer flexible ones

Biochemical and Structural Diversification of C₄ Photosynthesis in Tribe Zoysieae (Poaceae)

C4 photosynthesis has evolved independently multiple times in grass lineages with nine anatomical and three biochemical subtypes. Chloridoideae represents one of the separate events and contains species of two biochemical subtypes, NAD-ME and PEP-CK. Assessment of C4 photosynthesis diversification is limited by species sampling. In this study, the biochemical subtypes together with anatomical leaf traits were analyzed in 19 species to reveal the evolutionary scenario for diversification of C4 photosynthesis in tribe Zoysieae (Chloridoideae). The effect of habitat on anatomical and biochemical diversification was also evaluated. The results for the 19 species studied indicate that 11 species have only NAD-ME as a decarboxylating enzyme, while eight species belong to the PEP-CK subtype. Leaf anatomy corresponds to the biochemical subtype. Analysis of Zoysieae phylogeny indicates multiple switches between PEP-CK and NAD-ME photosynthetic subtypes, with PEP-CK most likely as the ancestral subtype, and with multiple independent PEP-CK decarboxylase losses and its secondary acquisition. A strong correlation was detected between C4 biochemical subtypes studied and habitat annual precipitation wherein NAD-ME species are confined to drier habitats, while PEP-CK species prefer humid areas. Structural adaptations to arid climate include increases in leaf thickness and interveinal distance. Our analysis suggests that multiple loss of PEP-CK decarboxylase could have been driven by climate aridization followed by continued adaptive changes in leaf anatomy