RESUMEN
An acid-functionalised, magnetic, room-temperature ionic liquid, 1-acyl-3-methylimidazolium tetrachloroferrate ([AcMIm]FeCl4 ), was synthesised and its optical, magnetic, and thermal properties were investigated. The magnetic moment (0.05402â emu in 2â T magnetic fields) showed strong paramagnetic behaviour, and thermogravimetric analysis indicated very good thermal stability with a decomposition temperature higher than 230 °C. Additionally, [AcMIm]FeCl4 efficiently catalysed the oxidative ipso-hydroxylation of arylboronic acids and regioselective Friedel-Crafts acylation without external organic solvent or additives, such as acids, base, and ligands. This functionalised ionic liquid, [AcMIm]FeCl4 , was recycled and reused at least six times without significant loss of its catalytic properties and stability.
RESUMEN
Most of the urea sensors are biosensors and utilize urease, which limit their use in harsh environments. Recently, because of their exceptional ability to endorse faster electron transfer, carbonaceous material composites and quantum dots are being used for fabrication of a sensitive transducer surface for urea biosensors. We demonstrate an enzyme free ultrasensitive urea sensor fabricated using a SnO2 quantum dots (QDs)/reduced graphene oxide (RGO) composite. Due to the synergistic effect of the constituents, the SnO2 QDs/RGO (SRGO) composite proved to be an excellent probe for electrochemical sensing. The morphology and structure of the composite was characterized by various techniques, and it was observed that SnO2 QDs are decorated on RGO layers. Electrochemical studies were performed to evaluate the characteristics of the sensor toward detection of urea. Amperometry studies show that the SRGO/GCE electrode is sensitive to urea in the concentration range of 1.6 × 10(-14)-3.9 × 10(-12) M, with a detection limit of as low as 11.7 fM. However, this is an indirect measurement for urea wherein the analytical signal is recorded as a decrease in the amperommetric and/or voltammetric current from the solution redox species ferrocyanide. The porous structure of the SRGO matrix offers a very low transport barrier and thus promotes rapid diffusion of the ionic species from the solution to the electrode, leading to a rapid response time (â¼5 s) and ultrahigh sensitivity (1.38 µA/fM). Good analytical performance in the presence of interfering agents, low cost, and easy synthesis methodology suggest that SRGO can be quite promising as an electroactive material for effective urea sensing.