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    • Electrochemical experiments cyclic voltammetry CV were perfo

    2018-11-13

    Electrochemical experiments (cyclic voltammetry (CV)) were performed using Autolab Potentiostat/Galvanostat (Eco Chemie, Netherlands) with three-electrode cell where L/IL/ITO (laponite/Ionic Liquid/ITO) was used as working electrode, platinum (Pt) wire as the auxiliary electrode and Ag/AgCl as reference electrode in 3.3mM Zobell’s solution (3.3mM ferric and ferrous solution mM; pH 7.0) containing 0.9% (w/v) KCl.
    Results and discussion The resulting films, after the preparation of L/IL dispersions, were fabricated by uniformly spreading 10μl solution of L/IL sol on conducting side of ITO which had 0.25cm2 surface areas. The film formed was kept overnight for drying (∼24h) at room temperature. The pi3k inhibitor transfer kinetics of electroactive species was studied using cyclic voltammetry (CV), a widely used technique to obtain information about electrochemical reactions. Before undertaking a thorough study, it was felt necessary to optimize the electrochemical behavior of L/IL/ITO electrode as a function of IL concentration in Zobell’s solution at a given scan rate of (≈20mV/s). The optimization studies were necessary to explicitly determine the dependence of various experimental parameters like concentration, scan rate, pH, pulse amplitude etc. to establish the best experimental working condition [12,13,30–32]. The concentration of IL can change the properties of the electrode surface; hence we first investigated the effect on peak currents by varying concentration of IL. The highest anodic and cathodic peak currents was obtained for 0.04% (w/v) IL (shown in Fig. 1) which indicated that this concentration of IL in L/IL/ITO had better electrochemical properties compared to others. Therefore, we have selected electrodes made with 0.04% (w/v) ILs for further studies. The electrochemical response of L/IL/ITO electrode was monitored by a voltammetric sweep curve ranging from −0.1 to +0.4V as a function of scan rate varying from 10 to 100mV/s (Fig. 2(a)). From this figure we could observe well-defined peak shapes at different scan rates with magnitudes of both anodic (Ia) and cathodic (Ic) peak current increasing linearly. This linear dependence of peak current (Fig. 2(b)) indicated that the electrode provided sufficient accessibility to electron between electrolyte and electrode revealing surface controlled electrode process. The anodic (Ea) and cathodic (Ec) peak potentials did not show any shift with scan rate. The independent behavior of separation of peak potentials (ΔE=Ea−Ec) with scan rate and linear dependence of peak current with scan rate suggested that redox reaction which was undergoing in L/IL/ITO electrode was reversible. The cyclic voltammetric behavior for only laponite electrode (L/ITO) is shown in Fig. S1 (Supplementary Information). A plot of peak current as a function of scan rate in range 10–100mV/s was found to be linear with regression equation given for both anodic and cathodic response was given by Similarly, for L/ITO electrode, the regression equation of peak current as a function of scan rate is given as The current voltage response profile of L/IL/ITO electrode was compared with the ITO and L/ITO electrodes at scan rate of 20mV/s in the applied potential range of −0.1V to+0.4V, where we observed the reduction in magnitude of peak current (Fig. 3a). This ensured the presence of film on ITO surface. However, in our case the reduction in current was significant as compared to bare ITO and L/ITO samples, thus it was clear that the L/IL/ITO film reduced the mobility of the charge carriers, and hence the conductivity. The surface concentration of the L/IL/ITO electrode can be estimated from current versus potential plot by using the Brown–Anson model which is based on the following equation [33] given bywhere n is number of electrons transferred, F is faraday constant (=96,485C/mol), I* is the surface concentration of L/IL/ITO electrode (mol/cm2) and A is surface area of the electrode (0.25cm2), V is the scan rate and R is gas constant (8.314J/mol/K) and T=300K.