Employment of electrostatic interactions for amperometric detection of carbon nanoparticles in a FIA system

Abstract

The development of methods for nanoparticle detection is highly desirable due to their increasing presence in the environment. Recently, we have shown that the electrochemical detection in flow is one of the possible solutions. Here we demonstrate a dramatic improvement of analytical parameters of such detection. The significant enhancement of an amperometric signal resulting from the electrocatalytic oxidation of ascorbic acid (AA) in a negatively charged phenylsulphonated carbon nanoparticle suspension in the millifluidic flow injection analysis system as compared to earlier results (D. Ogończyk, et al., Electrochem. Commun., 2014, 43, 40) is presented. This effect results from the tailoring of electrostatic interactions, e.g. optimization of the supporting electrolyte and AA concentration and/or immobilization of positively charged functionalities at the electrode surface. The sensitivity is improved by almost three orders of magnitude and the limit of detection of carbon nanoparticles is decreased by two orders of magnitude down to 0.001 mg mL(-1).

Electrochemical Detection of Positively Charged Carbon Nanoparticles Suspension in Flow

“…Recently, we and others demonstrated that it is possible to record the amperometric response of the catalytic nanoparticles from the background current on standard size disc electrodes (diameter in the range of millimetres) in forced convection conditions. This was done in both flow system and with rotating disc electrode . It was concluded, that adsorption of catalytic nanoparticles provides suitable conditions for discrimination of the faradaic from capacitive current.…”

“…It occurs when CNPs + are in direct contact with the ITO surface, long enough to allow for multiple electron transfer . CNPs + catalyze AA oxidation in the absence of any other catalytic component similarly like CNPs − deliberately deposited on the electrode surface or adsorbed from suspensions . However, the change of functional groups from negatively to positively charged results in an increase of current density.…”

“…This is the case of mixed film of positively (CNPs + ) and negatively (CNPs − ) charged carbon nanoparticles or CNPs + deposited on MoS 2 nanopetal stacks . Earlier studies in flow system were performed with suspended CNPs − either on bare indium tin oxide (ITO) electrodes or modified with positively charged functionalities . Here we will show that suspended CNPs + promote larger enhancement of the amperometric signal related to the ascorbate (AA) electrooxidation at ITO electrode as compared to CNP − .…”

Continuous Electrochemical Detection of Gold Nanoparticles in Flow

“…The dependence of peak current on AuNPs concentration is power‐law (Figure ). The high sensitivity is presumably a consequence of strong interactions between positively charged NPs and polyvalent sulphite anions , . As a result, i) the AuNPs are attracting substrate, then ii) the effective charge of gold nanoparticles’ surface is reversed and the surrounded AuNPs are stronger attracted to a positively charged working electrode (+1.2 V).…”

“…The response and reproducibility on a single ITO electrode (blue points in Figure ) is similar to those with the disposable ITO electrodes (red points in Figure ). This suggests that a memory‐effect of electrode does not appear at all , and AuNPs desorb from the electrode surface. Moreover, the shape of the current‐time dependence (Figure ) indicates a lack of sensitivity loss in time.…”