Naslov
Accumulation mechanism for metal chalcogenide nanoparticles at Hg electrodes: Cu sulfide example

Autori
Krznarić, Damir ; Helz, George R. ; Bura-Nakić, Elvira ; Jurašin, Darija

Izvornik
Analytical chemistry (0003-2700) 80 (2008), 3; 742-749

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
chalcogenide nanoparticles ; copper sulfide ; voltammetry

Sažetak
Mercury electrodes preconcentrate metal chalcogenide nanoparticles effectively, enabling their detection at submicromolar concentrations (as Σ chalcogenide) by adsorptive cathodic stripping voltammetry. Understanding the unique behavior of nanoparticle analytes during preconcentration is critical for lowering detection limits and for quantification. A multistep mechanism is proposed on the basis of accumulation experiments with polydisperse copper sulfide (CuxS) nanoparticles. Particles first diffuse and adsorb at the Hg surface. When both the electrode and particles have negative surface potentials, this process resembles charge-impeded coagulation, obeying the Schulze-Hardy rule at various electrolyte strengths. Consequently, accumulation rates are surprisingly sensitive to electrolyte concentration. Choosing accumulation potentials where the electrode and particles have opposite surface potentials greatly improves collection efficiency, especially for the smallest particles. After adsorption, particles undergo transformations. One product is a more stable (harder to reduce) form of CuxS, interpreted to consist of adclusters or adlayers. A very significant (~0.3 V) negative shift in reduction potential results from this transformation. Loss of analyte to at least one non-electroactive product is also observed. Loss is greatest for the smallest particles and is sensitive to choice of accumulation potential. To improve accumulation efficiency, accumulation potentials more positive that the potential of zero charge of Hg electrodes are advantageous, but care must be taken to remove dissolved chalcogenides under these conditions in order to avoid artifacts.

Izvorni jezik
Engleski

Znanstvena područja
Geologija, Kemija

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