Search

The initial wetting phenomena of MgO–SiO2 slag on MgO–C refractories were studied using the dispensed drop technique at 1873 K. As the carbon content increased, the apparent contact angle and height increased, whereas the apparent radius decreased. The change in the apparent contact angle according to the carbon content was applied to the Cassie model. Reduced Si was observed at the boundary between the slag and the refractories.it was seen that SiO2(l) + 2C(s) = Si(l) + 2CO(g) was the main reaction. [ABSTRACT FROM AUTHOR]

We obtained a gold nanomaterial/graphene oxide-modified glassy carbon electrode and characterized it using transmission electron microscope, scanning electron microscope, cyclic voltammetry (CV), and X-ray photoelectron spectroscopy techniques. A response of the electrode using square wave anodic stripping voltammetry for Pb, Cu, and Hg was found linear in the range from 1 × 10 to 1 × 10 M. The detection limits of Pb, Cu and Hg were 0.14, 0.5 and 1.2 pM, respectively. The method was applied to the simultaneous determination of Pb, Cu and Hg in seawater samples from a coastal region of Anatolia, and the results corresponded well with the values obtained by inductively coupled plasma-optical emission spectroscopy. [ABSTRACT FROM AUTHOR]

We investigated the electronic perturbation between graphene oxide and cobalt porphyrin to reveal the origin of the enhanced electrocatalytic activity of a hybrid complex using time-resolved spectroscopic measurements and theoretical calculations. The impulsively generated charge-separated state, GO−-(CoIIAPFP)+, undergoes fast charge recombination (<10 ps) between GO− and (CoIIAPFP)+ moieties. This fast charge recombination is directly related to the quick neutralization of (CoIIAPFP)+, which shortens the dead time of inactive CoIIIAPFP after the electrocatalytic reduction reaction. The fast transformation of inactive CoIIIAPFP to active CoIIAPFP is an important factor in the enhanced electrocatalytic activity of the hybrid complex. [ABSTRACT FROM AUTHOR]

Graphene oxide (GO) was covalently attached to glassy carbon (GC) electrode (GC-O-GO) for fabricating nanosensors to determine trace Pb and Cd using differential pulse anodic stripping voltammetry (DPASV). Surface characterization of the nanofilm-covered electrode was performed via electrochemical cyclic voltammetry (CV), transmission electron microscopy (TEM), atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS) techniques. Surface pKa of the GO covalent attached GC (GC-O-GO) was calculated via CV. Under optimal conditions, a linear response was found for Pb and Cd in the range from 1 × 10 to 1 × 10 M. The limit of detections (LODs) of Pb and Cd were 0.25 pM and 0.28 pM, respectively. The method shows good reproducibility, and stability was successfully applied to measure Pb and Cd levels in rice, soya, milk, and tap water samples, with good agreement with those obtained by the standard inductively coupled plasma optical emission spectrometry (ICP-OES) method. The method was evaluated by application with the simultaneous determination of the ions in food samples ( n = 6) using the standard addition method. The recoveries of the Pb and Cd were up to 98 %. [ABSTRACT FROM AUTHOR]

A variety of aryl bromides were coupled with propiolic acid in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) and catalyst Pd(PPh3)4 to afford the corresponding arylalkynecarboxylic acids in good yields at low temperature. This method showed good tolerance toward functional groups such as alkoxy, ketone, ester, aldehyde, cyano, nitro, and hydroxy. Under these conditions, propiolic acid showed higher reactivity than any other compound containing terminal alkyne groups. According to the mechanistic studies, the key reaction step for the high reactivity of propiolic acid might be ligand exchange between the acetylide and bromide at palladium, and/or reductive elimination, but not the oxidative addition step. [ABSTRACT FROM AUTHOR]

A potentiometric sensor based on the Schiff base 2,2′-(1E,1′E)-(1,1′-binaphthyl-2,2′-diylbis(azan-1-yl-1-ylidene))bis(methan-1-yl-1-ylidene)diphenol was synthesized and tested as an ionophore PVC-based membrane sensor selective towards silver ions (Ag). Potentiometric testing demonstrated the high affinity of this receptor to silver ions. Seven membranes were fabricated with different compositions, with best performance shown by that with an ionophore composition ( w/ w) of 1.0 mg, PVC 33.0 mg, 2-nitrophenyl octyl ether 66 mg, and potassium tetrakis( p-chlorophenyl)borate 50 mol% in 1.0 mL tetrahydrofuran. The sensor worked well over a wide range of concentrations (1.0 × 10 to 1.0 × 10 M Ag) at pH 6, showing a slope of 60.99 mV/dec with rapid response times of less than 3 s. The sensor also showed good selectivity towards Ag in the presence of interfering cations, with the highest selectivity coefficient observed for Hg (2.7). A low detection limit of 3.4 × 10 M Ag was established. [ABSTRACT FROM AUTHOR]