Potentiometric detection of silver (I) ion based on carbon paste electrode modified with diazo-thiophenol-functionalized nanoporous silica gel

Composite Silica-Based Films as Platforms for Electrochemical Sensors

Sol-gel-derived silica thin films generated onto electrode surfaces in the form of organic-inorganic hybrid coatings or other composite layers have found tremendous interest for being used as platforms for the development of electrochemical sensors and biosensors. After a brief description of the strategies applied to prepare such materials, and their interest as electrode modifier, this review will summarize the major advances made so far with composite silica-based films in electroanalysis. It will primarily focus on electrochemical sensors involving both non-ordered composite films and vertically oriented mesoporous membranes, the biosensors exploiting the concept of sol-gel bioencapsulation on electrode, the spectroelectrochemical sensors, and some others.

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.

Positional Isomeric Symmetric Dipodal Receptors Dangled with Rotatable Binding Scaffolds: Fluorescent Sensing of Silver Ions and Sequential Detection of l-Histidine and Their Multifarious Applications

Three simple dipodal artificial acyclic symmetric receptors, SDO, SDM, and SDP, driven by positional isomerism based on xylelene scaffolds were designed, synthesized, and characterized by ¹H NMR, ¹³C NMR, and mass spectroscopy techniques. Probes SDO, SDM, and SDP demonstrated selective detection of Ag⁺ metal ions and amino acid l-histidine in a DMSO-H₂O solution (1:1 v/v, HEPES 50 mM, pH = 7.4). The detection of Ag⁺ metal ions occurred in three ways: (i) inhibition of the photoinduced electron-transfer (PET) process, (ii) blueshifted fluorescence enhancement via the intramolecular charge-transfer (ICT) process, and (iii) restricted rotation of the dangling benzylic scaffold following coordination with a Ag⁺ metal ion. Job's plot analysis and quantum yields confirm the binding of probes to Ag⁺ in 1:1, 1:2, and 1:2 ratios with LODs and LOQs found to be 1.3 μM and 3.19 × 10^-7 M, 6.40 × 10^-7 and 2.44 × 10 ^-6 M, and 9.76 × 10^-7 and 21.01 × 10^-7 M, respectively. ¹H NMR titration, HRMS, ESI-TOF, IR analysis, and theoretical DFT investigations were also used to establish the binding stoichiometry. Furthermore, the probes were utilized for the detection of Ag⁺ ions in water samples, food samples, soil analysis, and bacterial imaging in Escherichia coli cells and a molecular logic gate was constructed.

Cobalt based Bi-functional Metal Organic Framework mediated Fluorescent Bio-sensing System for Hypersensitive Detection of Ag+ Ions through Catalytic Hairpin Assembly

Silver is often used as a water disinfectant in healthcare institutions as well as in potable water purifiers. Even though there are no strict regulations regarding the amount of silver...

A label-free Exonuclease I-assisted fluorescence aptasensor for highly selective and sensitive detection of silver ions

Based on the specific interaction of Ag⁺ and cytosine-cytosine (C-C) base mismatch and using berberine (Ber) as the fluorescent probe and Exonuclease I (Exo I) as the background fluorescence reducing tool, a label-free Exo I-assisted fluorescence aptamer sensing platform was established for the detection of silver ions with high sensitivity and selectivity. Exo I reduced the fluorescence background of the Ber/Ag⁺-aptamer complex to a level similar to that of Ber itself in the absence of Ag⁺. After introducing Ag⁺ into the sensing system, it induces the aptamer rich in base C to form C-Ag⁺-C i-motif structure which are resistant to degradation mediated by Exo I. The concentration of Ber, Ag⁺-aptamer, Exo I and the temperature and reaction time for Exo I were all optimized. Under the optimal experimental conditions, the detection limit of Ag⁺ was 4.4 nM and the linear range was from 0.0059 μM to 235.48 μM with a coefficient of determination (R²) > 0.99. Moreover, the proposed strategy had been successfully applied to the detection of Ag⁺ in tap water and human serum with a good recovery ranging from 88.4% to 106.9%.

Potentiometric Sensor Based on Carbon Paste Electrode for Monitoring Total Residual Chlorine in Electrolytically-Treated Ballast Water

A new potentiometric sensor based on modified carbon paste electrode (CPE) was prepared for the sensitive and selective detection of total residual chlorine (TRC) in simulated electrolytically-treated ballast water (BW). The modified CPE was prepared using ferrocene (Fc) as the sensing species and paraffin oil as the binder. It is revealed that the addition of Fc can significantly shorten the response time and improve the reproducibility, selectivity, and stability of the sensor. The open circuit potential of the Fc-CPE is in linear proportion to the logarithm of TRC within the TRC concentration range from 1 mg∙dm-3 to 15 mg∙dm-3. In addition, the Fc-CPE sensor exhibits good selectivity to TRC over a wide concentration range of the possible co-exiting interference ions in seawater. The Fc-CPE electrode can be used as a convenient and reliable sensor for the continuous monitoring of TRC during the electrolytic treatment of BW.

An overwhelmingly selective colorimetric sensor for Ag(+) using a simple modified polyacrylonitrile fiber

A carboxymethyl-dithiocarbamate immobilized polyacrylonitrile fiber colorimetric sensor has been synthesized. This fiber sensor exhibits excellent selectivity and sensitivity for Ag(+) in aqueous solution with a remarkable color change from light pink to red-brown over a wide pH range of 2-12. The sensor responds selectively to Ag(+) in the presence of other ions, including Mg(2+), Al(3+), Ca(2+), Cr(3+), Mn(2+), Co(2+), Ni(2+), Cu(2+), Zn(2+), Cd(2+), Hg(2+) and Pb(2+). The colorimetric sensor has an extremely fast response time (10s) and a low visual limit of detection (5.53×10(-12) mol/L). The fiber sensor also undergoes an obvious color change in the presence of Ag(+) solutions containing EDTA, NaCl or NaBr. Density functional theory optimization reveals that the sensor and Ag(+) interact via a seven-membered ring complexation mechanism.

Highly sensitive and selective detection of silver(I) in aqueous solution with silver(I)-specific DNA and Sybr Green I

We report a label-free fluorescence turn-on approach for the sensitive and selective sensing of silver ion Ag(+) based on Ag(+) induced conformational change of cytosine-rich single-stranded DNA. A silver specific oligonucleotide (SSO) undergoes a structural transition from single-stranded DNA (ssDNA) to a C-Ag(+)-C mediated hairpin structure, which can be recognized by a double-stranded DNA (dsDNA) intercalator Sybr Green I (SG). The linear response range for Ag(+) detection was from 1 nM to 100 nM. The method presented here is highly sensitive and a limit of detection of 1 nM was obtained. More importantly, this optical method was successfully used to identify complex sample mixtures.