Emma J. E. Stuart

Determining unknown concentrations of nanoparticles: the particle-impact electrochemistry of nickel and silver

The developing field of particle-impact electrochemistry is rapidly establishing itself as a powerful tool for the interpretation of a wide range of phenomena associated with nanoparticles. In this article we present results showing the characterisation of nickel nanoparticles and, for the first time, a mixture of nanoparticles: in this case nickel and silver. The former are shown not to aggregate in aqueous solution whereas the latter do. We report a novel method for the determination on unknown concentrations of nanoparticles in a sample and demonstrate its use for both aggregating and non-aggregating nanoparticles.

Electrochemical observation of single collision events: fullerene nanoparticles.

Individual fullerene nanoparticles are detected and sized in a non-aqueous solution via cathodic particle coulometry where the direct, quantitative reduction of single nanoparticles is achieved upon collision with a potentiostated gold electrode. This is the first time that the nanoparticle impact technique has been shown to work in a non-aqueous electrolyte and utilized to coulometrically size carbonaceous nanoparticles. Contrast is drawn between single-nanoparticle electrochemistry and that seen using nanoparticle ensembles via modified electrodes.

Get More Out of Your Data: A New Approach to Agglomeration and Aggregation Studies Using Nanoparticle Impact Experiments

Anodic particle coloumetry is used to size silver nanoparticles impacting a carbon microelectrode in a potassium chloride/citrate solution. Besides their size, their agglomeration state in solution is also investigated solely by electrochemical means and subsequent data analysis. Validation of this new approach to nanoparticle agglomeration studies is performed by comparison with the results of a commercially available nanoparticle tracking analysis system, which shows excellent agreement. Moreover, it is demonstrated that the electrochemical technique has the advantage of directly yielding the number of atoms per impacting nanoparticle irrespective of its shape. This is not true for the optical nanoparticle tracking system, which requires a correction for the nonspherical shape of agglomerated nanoparticles to derive reasonable information on the agglomeration state.

Electrochemical detection of commercial silver nanoparticles: identification, sizing and detection in environmental media

The electrochemistry of silver nanoparticles contained in a consumer product has been studied. The redox properties of silver particles in a commercially available disinfectant cleaning spray were investigated via cyclic voltammetry before particle-impact voltammetry was used to detect single particles in both a typical aqueous electrolyte and authentic seawater media. We show that particle-impact voltammetry is a promising method for the detection of nanoparticles that have leached into the environment from consumer products, which is an important development for the determination of risks associated with the incorporation of nanotechnology into everyday products.

Particle-impact nanoelectrochemistry: a Fickian model for nanoparticle transport

The transport of nanoparticles to a substrate electrode for collision can be quantitatively described by a Fickian (i.e. diffusional) model both where the nanoparticles are oxidatively electrolysed at the electrode and where electrolysis of solution-phase species occurs on the surface of the impacting nanoparticles.

Nanoparticles-Emerging Contaminants

The chemical nature of the different nanoparticles present in the environment, both naturally and through human activity, along with their estimated levels of release and likely toxicity is overviewed. The use of recently developed voltammetric methods for the identification of nanoparticles along with the measurement of their state of aggregation and their concentration is discussed in depth. Future directions in the field are evaluated.