Anodic stripping voltammetry with carbon paste electrodes for rapid Ag(I) and Cu(II) determinations

A label-free photoelectrochemical biosensor for silver ions based on Zn-Co doped C and CdS QD nanomaterials

A sensitive photoelectrochemical (PEC) biosensor for silver ions (Ag+) was developed based on Zn-Co doped C and CdS quantum dot (CdS QD) nanomaterials. Hydrophobic modified sodium alginate (HMA), which could stabilize and improve the PEC performance of CdS QDs, was also used for the construction of PEC sensors. Especially, Zn-Co doped C, CdS QDs and HMA were sequentially modified onto an electrode surface via the drop-coating method, and a C base rich DNA strand was then immobilized onto the modified electrode. As the C base in DNA specifically recognized Ag+, it formed a C-Ag+-C complex in the presence of Ag+, which created a spatial steric hindrance, resulting in a reduced PEC response. The sensing platform is sensitive to Ag+ in the range of 10.0 fM to 0.10 μM, with a limit of detection of 3.99 fM. This work offers an ideal platform to determine trace heavy metal ions in environmental monitoring and bioanalysis.

A Review of Analytical Techniques for the Determination and Separation of Silver Ions and Its Nanoparticles

Many articles have already been published dealing with silver ions and its nanoparticles, but mostly from the environmental and toxicological point of view. This article is a review focused on the various analytical techniques and detection platforms used in the separation and determination of mentioned above species, especially on the trace concentration level. Commonly used are optical methods because of their high sensitivity and easy automation. The separation methods are mainly used for the separation and preconcentration of silver particles. Their combination with other analytical techniques, mainly inductively coupled plasma mass spectrometry (ICP-MS) leads to very low detection limits of analysis. The electrochemical methods are also powerful and perspective mainly because of the fabrication of new sensors designed for silver determination. All methods may be combined with each other to achieve a synergistic improvement of analytical parameters with an impact on sensitivity, selectivity and reliability. The paper comprises a review of all three types of analytical methods on the determination of trace quantities of silver ions and its nanoparticles.

Anodic Stripping Voltammetry on a Carbon-based Ion-Selective Electrode

In this study, we demonstrated the unique capability of carbon-based ion-selective electrode (ISE) to perform highly sensitive square wave anodic stripping voltammetry, while maintaining all the properties of an ISE, in terms of sensitivity, detection limit, response time and selectivity. Square wave anodic stripping voltammetry involves deposition and dissolution steps of metal ions, which means adsorption and desorption of metal ions on the conductive ion-selective membrane without losing its ion-sensing property. To demonstrate this capability, we chose a Ca2+ ion-selective microelectrode (μISE) as a potentiometric method and Cu2+-stripping voltammetry as an amperometric method. The carbon-based ISE surface is capable of quantifying nanomolar to micromolar Cu2+ in both a standard acetate buffer and a complex water sample. The Ca2+-μISE also showed a Nernstian slope of 29 mV / log [Ca2+] and a detection limit of 1 μM within the linear range of 1 μM to 10 mM. It thus opens an opportunity to use the low detection limit of anodic stripping voltammetry and the high selectivity of ISE-based potentiometry.

An ultrasensitive electrochemical method for detection of Ag(+) based on cyclic amplification of exonuclease III activity on cytosine-Ag(+)-cytosine

Ag(+) is known to bind very strongly with cytosine-cytosine (C-C) mismatches in DNA duplexes to form C-Ag(+)-C base pairs. Exonuclease III (Exo III) can catalyze the stepwise removal of mononucleotides of duplex DNA. In this work, we study Exo III activity on DNA hybrids containing C-Ag(+)-C base pairs. Our experiments show that Ag(+) ions could intentionally trigger the activity of Exo III towards a designed cytosine-rich DNA oligonucleotide (C-rich probe) by the conformational change of the probe. Our sensing strategy uses this conformation-dependent activity of Exo III, which is controlled through the cyclical shuffling of Ag(+) ions between the solid DNA hybrid and the solution phase. This interesting conversion has led to the development of an ultrasensitive detection platform for Ag(+) ions with a detection limit of 0.03 nM and a total assay time possible within minutes. This simple detection strategy could also be used for the detection of other metal ions which exhibit specific interactions with natural or synthetic bases.