No abstract

A eletrocristalização de níquel foi estudada sobre ultramicroeletrodo (UME) de platina. O comportamento dos transientes de corrente indicou um processo de nucleação instantânea sob controle cinético. A aplicação do modelo de Abyaneh mostrou que os núcleos crescem com uma geometria do tipo calota esférica, possuindo valores diferentes para as constantes de velocidade no sentido paralelo e per pen dic u lar à superfície. As constantes de velocidade para o crescimento de núcleos no sentido paralelo variaram de 5,97 x 10-7 a 1,92 x 10-7 mol cm-2 s-1 , com o aumento do potencial de-0,57 a-0,63 V, enquanto que as correspondentes constantes no sentido per pen dic u lar apresentaram valores em torno de 1,44 x 10-7 mol cm-2 s-1. As relações en tre estas forneceram os ângulos de contato, cujos valores aumentaram de 27,5 a 87,6 graus. Finalmente, o número de núcleos formados aumentou com o potencial, de 0,43 x 10 7 a 379,09 x 10 7 cm-2. The electrocrystallization of nickel was stud ied on a plat i num ultramicroelectrode (UME). The be hav iour of the cur rent tran sients pointed to an in stan ta neous nu cle ation pro cess un der kinetic con trol. The ap pli ca tion of Abyaneh's model showed that nu clei grow in a spher i cal cap ge om e try with dif fer ent val ues for both rate con stants in the par al lel and per pen dic u l ar di rections. The par al lel rate con stants for nu clei growth var ied from 5.97 x 10-7 to 1.92 x 10-7 mol cm-2 s-1 by in creas ing the step po ten tial from-0.57 to-0.63 V, while the per pen dic u lar rate constant re mained con stant around 1.44 x 10-7 mol cm-2 s-1. The re la tion ships be tween these two con stants give the con tact an gles of the crys tal lites, whose val ues also in creased with po t en tial from 27.5 to 87.6 de grees. Finally, the num ber of nu clei formed on the sur face in creased with po ten tial from 0.43 x 10 7 to 379.09 x 10 7 cm-2 .

An arene-ruthenium (II) complex -[Ru(η 6 -p-cymene)(ampy)Cl]PF 6 , where ampy is 2-(aminomethyl)pyridine -was synthesized and used in the construction of a modified carbon ceramic electrode (Ru-CCE) for determining paracetamol (PCT) by square wave voltammetry (SWV). The modified electrode, constructed by sol-gel methods, provides a considerable enhancement of PCT oxidation. Under the optimized working conditions, the peak current is linear to the PCT concentration in the ranges of 1.99 × 10 −6 -3.10 × 10 -5 mol L −1 with a detection limit of 5.83 × 10 −7 mol L -1 . The Ru-CCE showed good repeatability and reproducibility (RSD < 4%), long-term stability (>12 months). Lastly, the proposed sensor was used for the determination of PCT in pharmaceutical formulations, offering a promising tool for quality control.

Complexes with general formula [RuCl(η6-p-cymene)(P-NR-P)]X (R = CH2Py (Py = pyridine) – [1a]+, CH2Ph (Ph = phenyl) – [1b]+, Ph – [1c] and p-tol (p-tol = p-tolyl) – [1d]+; X...