Aysegul Kutluay

An electrochemical sensor prepared by sonochemical one-pot synthesis of multi-walled carbon nanotube-supported cobalt nanoparticles for the simultaneous determination of paracetamol and dopamine

Multi-walled carbon nanotubes (MWCNTs) functionalized by cobalt nanoparticles were obtained using a single step chemical deposition method in an ultrasonic bath. The composite material was characterized using scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX). The electroactivity of the cobalt-functionalized MWCNTs was assessed in respect to the electrooxidation of paracetamol (PAR) and dopamine (DA). It was found that the carbon nanotube supported cobalt nanoparticles have significantly higher catalytic properties. The proposed electrode has been applied for the simultaneous determination of PAR and DA. The modified electrode could resolve the overlapped voltammetric waves of PAR and DA into two well-defined voltammetric peaks with peak to peak separation of about 203 mV. On the other hand, the presence of potential drug interfering compounds AA and UA did not affect the voltammetric responses of PAR and DA. The current of oxidation peaks showed a linear dependent on the concentrations of PAR and DA in the range of 5.2×10(-9)-4.5×10(-7) M (R(2)=0.9987) and 5.0×10(-8)-3.0×10(-6) M (R(2)=0.9999), respectively. The detection limits of 1.0×10(-9) M and 1.5×10(-8) M were obtained for PAR and DA, respectively. The proposed electrode showed good stability (peak current change: 4.9% with and RSD of 2.6% for PAR; 5.5% with and RSD of 3.0% for DA over 3 weeks), reproducibility (RSD 2.3% for PAR and RSD 1.5% for DA), repeatability (RSD 2.25% for PAR and RSD 2.50% for DA) and high recovery (99.7% with an RSD of 1.3% for PAR; 100.8% with an RSD of 1.8% for DA). The proposed method was successfully applied to the determination of PAR and DA in pharmaceuticals.

Spectroscopic and electron-transfer reactivity studies of bulky bis(N-cycloalkyl-3,5-tBu2-salicylaldiminato)copper(II) complexes: Generation of uncoordinated and coordinated phenoxyl radicals

This work summarizes the results of our studies on the spectral, magnetic, electrochemical and chemical redox properties of N-cycloalkyl-3,5-(t)Bu(2)-salicylaldimine ligands [cycloalkyl=cyclo-C(5)H(9)(HL(1)), cyclo-C(6)H(11) (HL(2)), cyclo-C(7)H(13) (HL(3)), cyclo-C(8)H(15) (HL(4)), 1-adamantyl (HL(5)), 2-adamantyl (HL(6))] and their copper(II) complexes (1-6). The compounds have been characterized by IR, (1)H NMR, UV-vis, EPR spectroscopy, electrochemical and magnetic susceptibility measurements. The geometry of 1-6, according to their EPR (g(II) and g(II)/A(II)) and visible spectral data, exhibit a significant amount distortion from slightly distorted square-planar to pseudo-tetrahedral. The cyclic voltammetric studies of 1-6 reveal that as the extent of the tetrahedral distortion of Cu(II) center increases on going from 1 to 5, the values of Cu(II)/Cu(I) potentials became more negative. The compounds have been oxidized electrochemically and chemically and the generated relatively stable uncoordinated phenoxyl [HL(x)](*+) and coordinated Cu(II)-phenoxyl radical [1-6](*+) species have been characterized by UV/vis and EPR spectroscopy.