Chemosensors, Volume 3, Issue 4 (December 2015) – 4 articles , Pages 241-294

The PVC membrane of an ion-selective electrode (ISE) sensitive to dibasic phosphate ions (HPO₄-ISE) has not been optimized for maximum selectivity, sensitivity, and useable ISE lifetime and further work was necessary to improve its performance. Two areas of investigation are reported here: include the parameters for the lipophilicity of the plasticizer compound used and the amount of cyclic polyamine ionophore incorporated in the PVC membrane. Six candidate plasticizers with a range of lipophilicity were evaluated for their effect on the useable lifetime, sensitivity, and selectivity of the ISE against 13 different anions. Selectivity was determined by a modified fixed interferent method, sensitivity was determined without interferents, and the usable lifetime evaluated at the elapsed time where 50% of the HPO₄-ISE failed (L₅₀). The results show that choosing a plasticizer that has a lipophilicity similar to the ionophore’s results in the best selectivity and sensitivity and the longest L₅₀. Full article

The inhibitory effect of nine phenylcarbamates with various substituents was studied. For this purpose, electrochemical sensors were applied under two different conditions: if an enzyme was present in the solution or if the enzyme was immobilized onto the electrode surface. In both cases, 3-[(ethoxycarbonyl)amino]phenyl (4-chloro-phenyl)carbamate was found as the most effective inhibitor for butyrylcholinesterase. The best inhibitors for acetylcholinesterase were determined as well, depending on the used method. Thus, 3‑[(butoxycarbonyl)-amino]phenyl phenylcarbamate with the enzyme present in the solution and 3-[(ethoxycarbonyl)amino]phenyl (3-methylphenyl)carbamate when the enzyme was immobilized onto the electrode surface were evaluated as the most effective inhibitors. Michaelis constants as well as maximum reaction rates were calculated and assessed. Full article

Accurate methods that can continuously detect low concentrations of hydrogen peroxide (H₂O₂) have a huge application potential in biological, pharmaceutical, clinical and environmental analysis. Luminescent probes and nanomaterials are used for fabrication of sensors for H₂O₂ that can be applied for these purposes. In contrast to previous reviews focusing on the chemical design of molecular probes for H₂O₂, this mini-review highlights the latest luminescent nanoparticular materials and new luminescent optical sensors for H₂O₂ in terms of the nanomaterial composition and luminescent receptor used in the sensors. The nanomaterial section is subdivided into schemes based on gold nanoparticles, polymeric nanoparticles with embedded enzymes, probes showing aggregation-induced emission enhancement, quantum dots, lanthanide-based nanoparticles and carbon based nanomaterials, respectively. Moreover, the sensors are ordered according to the type of luminescent receptor used within the sensor membranes. Among them are lanthanide complexes, metal-ligand complexes, oxidic nanoparticles and organic dyes. Further, the optical sensors are confined to those that are capable to monitor the concentration of H₂O₂ in a sample over time or are reusable. Optical sensors responding to gaseous H₂O₂ are not covered. All nanomaterials and sensors are characterized with respect to the analytical reaction towards H₂O₂, limit of detection (LOD), analytical range, electrolyte, pH and response time/incubation time. Applications to real samples are given. Finally, we assess the suitability of the nanomaterials to be used in membrane-based sensors and discuss future trends and perspectives of these sensors in biomedical research. Full article

This paper is aimed at selectivity investigation of gas sensors, based on chemically modified nanocrystalline tin dioxide in the detection of CO and ammonia mixtures in air. Sol-gel prepared tin dioxide was modified by palladium and ruthenium oxides clusters via an impregnation technique. Sensing behavior to CO, NH₃ and their mixtures in air was studied by in situ resistance measurements. Using the appropriate match of operating temperatures, it was shown that the reducing gases mixed in a ppm-level with air could be discriminated by the noble metal oxide-modified SnO₂. Introducing palladium oxide provided high CO-sensitivity at 25–50 °C. Tin dioxide modified by ruthenium oxide demonstrated increased sensor signals to ammonia at 150–200 °C, and selectivity to NH₃ in presence of higher CO concentrations. Full article