BaSO<SUB>4</SUB> crystals grown at an expanding liquid-liquid interface in a radial hele-shaw cell show spontaneous large-scale assembly into filaments

Control over the crystallography, morphology, and spontaneous organization of ceramic crystals are important goals in advanced materials engineering with important application potential. Most studies hitherto have concentrated on static charged interfaces as templates for the controlled nucleation and growth of ceramic crystals. In this communication, we show that BaSO<SUB>4</SUB> crystals grown at a steadily expanding liquid-liquid interface populated by fatty acid molecules spontaneously organize themselves into highly linear superstructures over large length-scales. This experiment is realized in a radial Hele-Shaw cell where the liquid-liquid interfacial growth rate and consequently time scales such as arrival of surfactant molecules to the interface etc. may be readily modulated. Possible reasons for the regular assembly of barite crystals are discussed

Room-Temperature Ammonia Gas Sensing Using Mixed-Valent CuCo₂O₄ Nanoplatelets: Performance Enhancement through Stoichiometry Control

We report the sensing properties of an interesting ternary oxide CuCo₂O₄ (CCO) which comprises two earth-abundant transition elements, both capable of supporting multiple valence states. We have used a synthesis protocol, which renders unique nanoplatelet-type morphology but with a degree of biphasic character (CuO as a secondary phase in addition to the defect-spinel Cu_1–<i>x</i>Co₂O₄). This sample constitution can be controlled through the use of cation off-stoichiometry, and the same also influence the sensing response significantly. In particular, a Co 10 at. % excess CCO (CCO–Co(10)) case exhibits a good response (∼7.9% at 400 ppm) for NH₃ gas with a complete recovery at room temperature (23 °C, ±1 °C) in 57% RH. The material performance was investigated for other gases such as H₂S, NO₂, and CO. A good response is observed for H₂S and NO₂ gases but without a recovery; however, for CO, a poor response is noted. Herein, we discuss the specific results for ammonia sensing for the CCO–Co(10) case in detail via the use of different characterizations and outline the difference between the cases of the single-phase defect-stabilized material versus nonpercolating biphasic material

Bacteria-Mediated Precursor-Dependent Biosynthesis of Superparamagnetic Iron Oxide and Iron Sulfide Nanoparticles

International audienc

Bacteria-Mediated Precursor-Dependent Biosynthesis of Superparamagnetic Iron Oxide and Iron Sulfide Nanoparticles

International audienc