Ms. Claudia Daut - Preparation and characterization of capacitive field effect sensors with YSZ dielectric stack
Host: Laboratory of Solid State Physics, Riga, Latvia [23th of June - 08th of July, 2018]
Figure 1: Schematic of a GasFET structure with a porous platinum layer as Catalyst and an additional layer of YSZ as oxygen ion-conductor
The pollution of air in industrialized and developing countries is a serious health problem. One approach to detect air pollution are gas sensitive field effect transistors (GasFETs) - inexpensive, highly sensitive and small devices that could be used for development of handheld/miniature devices with possible scalability to mass environmental monitoring. However, the selectivity is a big issue. One promising method for improving selectivity is gate bias cycled operation (GBCO) . We started the investigation, whether the effect of GBCO can be improved by adding an ion-conductor layer to the gate stack.
During the STSM, ion-conducting yttrium-doped zirconium dioxide (YSZ) layers have been deposited on GasFET gates by magnetron sputtering (Fig.1).
For deposition a segmented target made of a metallic yttrium ring mounted on a ZrO2 disc has been used. Layers with 20, 30 and 50 nm thickness (measured by profilometer) have been deposited and characterized. The stoichiometry was measured by EDX, showing a ratio between Y and ZrO2 of 11.5 %. The deposition of different thicknesses will allow us in further investigations to verify optimal parameters for the gate stack.
The STSM has initiated future work on the improvement of the GasFET sensors. As a follow up to the STSM, the processing of GasFET samples using the deposited films will be done at Linköping University by Dr. Mike Andersson and the impact of the YSZ on the GBCO will be measured at the Lab for Measurement Technology under supervision of Dr. Tilman Sauerwald.
 Bur, C. (2015). Selectivity Enhancement of Gas Sensitive Field Effect Transistors by Dynamic Operation (Ph dissertation). Linköping University Electronic Press / Shaker Verlag, Linköping, Sweden / Aachen, Germany. https://doi.org/10.3384/diss.diva-114670
Dr. Mersiha Suljkanović - Optimization of voltammetric procedures for metal ion determination
Host: Dr Malgorzata Grabarczyk and Dr Cecylia Wardak, Maria Curie Sklodowska University, Lublin, Poland [02nd - 13th of July, 2018]
First part of the STSM was based on optimization of parameters for voltammetric determination of V(V), using Pb-film electrode and investigation of matrix influence during the measurements. Investigation of different working electrodes to replace the hanging mercury drop electrode (HMDE) due to its toxicity is very significant. The importance of V(V) determination lies in its wide distribution in the earth’s crust: at trace amounts it is an essential element but can be toxic at higher concentration (accumulates in body tissues such as liver, kidney and bone). In the voltammetric procedure, we managed to use successfully Pb-film electrode for V(V) determination. Influence of interferences: nonionic, anionic or cationic surfactants, humic acids, fulvic acids was also examined, as well as the possibility of their removal (application of Resins: Amberlite XAD-2 and Amberlite XAD-16).
Second part of the STSM was based on preparation of ion-selective electrodes with solid contact (SCISEs) and determination of their analytical parameters (detection limit, measuring range, characteristic slope, response time, optimal pH range) through potentiometric measurements, which also included study of: electrode selectivity (in relation to interfering ions), potential stability and also their reversibility. We prepared ion-selective electrodes sensitive to Cu2+ and NO3- ions: importance of nitrate determination lies in their toxic and carcinogenic effects on humans and animals and their presence in the environment (mainly in ground and surface water) and copper determination is also important from health aspect, due to their highly toxic effects (at high concentrations), but also an essential element for human life which deficiency affects human health. During the experiments we prepared two kind of SCISEs using diferent internal electrodes: silver/silver chloride electrode (Ag/AgCl) and glassy carbon electrode (GC). Influence of ionic liquids added to the membrane phase of prepared electrodes reflected on their properties in terms of sensitivity, potential stability and reversibility, for both type of ion-selective electrodes.
Overall STSM experience was very valuable for my professional development since I gain some practical skills related to voltammetric and potentiometric techniques. Furthermore, the obtained results provided some new insights related to V(V) determination using Pb-film electrode and also highlight the influence of ionic liquid addition in membrane composition during preparation of ISE for copper and nitrate determination.
Ms. Camilia Rubio - Real-Time and in situ analysis of total antioxidant capacity
Host: Dr. Hadar Ben-Yoav, Ben-Gurion University of the Negev, Israel [22nd - 29th of July, 2018]
The STSM of PhD student C. Peres-Rubio (CPR) took place at Department of Biomedical Engineering, Ben-Gurion University of the Negev, Israel, 22 -29th of July, 2018, under supervision by Dr. Hadar Ben-Yoav, principal researcher of the Nano bioelectronics Laboratory.
The objective of this STSM was to validate a novel analytical device based on an “intelligent multi-electrode array” for real-time and point-of-care testing of oxidative stress. For this, CPR set-up spectrophotometric assays for total antioxidant capacity and total oxidant status in the hosting laboratory in order to use them as a reference method for the electrochemical lab-on-a-chip developed by Ms. Anat Friedman, a MSc student in Dr. Ben-Yoav’s team.
Overall, the stay was very fruitful in terms of new contacts, increased knowledge, and new data generation, and as such a research article with the results obtained during this STSM is being drafted. Furthermore, the both groups are looking forward to collaborating in future projects based on new method development and their application in clinical studies.
Dr. Jelena Vladic - Verification of the work process and analysis of critical points of the handmade subcritical water extraction system
Host: Dr. Stela Jokic, Faculty of Food Technology Osijek, Croatia [24th of July - 01st of September, 2018]
The main goal of this STSM was verification of the work process of the hand-made constructed system for subcritical water extraction which is primarily affordable. In order to secure repeatability and credibility of results, it was necessary to compare the results of this handmade extraction system’s application with an extraction system which was bought from the official manufacturer. Therefore, a comparison of results of extraction of herbal material in terms of differences in the extraction efficiency, the quality of obtained extracts (chemical composition) and their biological activity was conducted. Also, operational parameters of the subcritical system were monitored in order to analyse critical points of the handmade subcritical system.
Important part of this STSM was acquisition and exchange of knowledge and skills in construction of contemporary extraction/separation system. Additionally, a very significant and positive outcome of this STSM was reinforcing my collaboration with Dr Jokic and making new connections and friendships in the scientific community. Also, future joint work will continue on improving the working process of the handmade subcritical water extraction system and removing determined disadvantages of the system. Results obtained by the proposed STSM will be disseminated as a result of PortASAP COST Action through presentation on scientific conferences and publications in peer-reviewed scientific journals.
Prof. Nikola Sakač - Estradiol detection in water by Quartz-Crystal Microbalance (QCM) and optical based biosensors (Phase 1)
Host: Università Federico II - Dipartimento di Fisica "Ettore Pancini", Italy [13th - 29th of September, 2018]
1) Optical biosensor research results:
- Antibodies were successfully immobilized on the golden nanoparticle (GNP) surface which enabled the further investigation.
- UV-VIS and Dynamic Light Scattering confirmed the formation of Ab-GNP-E2 aggregate which was the main goal to achieve and the hypothesis was approved.
- The behaviour of the biosensor at different E2 concentrations was successfully tested in the pg/mL concentrations of E2.
2) Quartz-Crystal Microbalance-(QCM) research results:
- Antibodies were successfully immobilized on the sensor surface which enabled the further investigation.
- Secondary antibodies together with GNPs were successfully employed as a ballast for determination of E2 at low level.
- The behaviour of the biosensor was observed at ng/mL E2 concentration and sensogram revealed a successful determination of low E2 concentration.