I hope that you are all doing well and staying safe but also slowly returning back to the so called “normality”, which in fact is going to be a new normality, since nothing is going to be exactly the same as it was before the pandemic. I do mean it in a good way because I sincerely hope that this time has allowed everyone to reflect a little bit on how things were, how we were behaving towards other people, how we were mistreating our planet and so on… I believe that it was a much needed wake-up call to everyone telling us to stop being selfish, to become more united and to set new goals thinking about the future of humanity and Mother Nature and not just ourselves.
I would also like to take the opportunity to mention how especially grateful I feel now by being part of a Marie-Curie International Training Network. This program has helped me tremendously to understand the importance of working together with people that come from completely different cultural and disciplinary backgrounds. Even though we are a quite diverse group of people within the FoodSmartphone project, we have still found a way to understand each other’s needs and ways of communication and are able to work together while also respecting one another.
The situation of the pandemic here in Spain has been quite severe, unfortunately we have had a lot of cases, so we have also had quite strict restrictions. We have just slowly started going back to the lab for a few hours per day two weeks ago and hopefully gradually we will be able to return to full time. After being at home reading and writing for several weeks, it has been really strange to come back to the lab bench and continue with my experiments but I have definitely needed this change of scenery and was eager to start again. My experiments now are mainly focused on testing my electrochemical sensors in different food matrices in order to detect my targeted pesticides. Being surrounded by electrodes all day made me think that this blog would be an excellent opportunity to share some basic information about electrochemistry and screen printed electrodes.
So as probably most of you already know electrochemistry is the study of the chemical response of a system to an electrical stimulation. It studies the loss of electrons (oxidation) or gain of electrons (reduction) that a material undergoes during the electrical stimulation. These so called redox reactions can provide information about several properties of a species in solution such as its concentration, kinetics, reaction mechanisms, chemical status, etc.
In most electrochemical techniques, there are three electrodes – the working electrode, the reference electrode and the counter (or auxiliary) electrode. Each electrode has a different role: the working electrode (WE) is where the cell reaction takes place, the reference electrode (RE) has a stable potential against which other potentials can be measured and the counter electrode (CE) provides a circuit with the WE over which current is either applied or measured. The three electrodes are connected to a potentiostat, an instrument which controls the potential of the working electrode and measures the resulting current.
For the development of my electrochemical sensors I am using the so called screen-printed electrodes (SPEs), which are generally cheap and disposable electrochemical devices that can be fabricated in bulk.
The Screen-printing technology consists of a layer-by-layer deposition of different types of inks upon a solid substrate with the use of a screen or a mesh that defines the geometry of the sensor. This technology has advantages of design flexibility, process automation, good reproducibility and a wide choice of materials. SPEs usually include a three electrode configuration (WE, CE, RE) printed on various types of plastic or ceramic substrates that can be easily modified with a great variety of commercial or self-made inks. The composition of the various inks used for the printing of the electrodes determines the selectivity and sensitivity of the analysis. The extensive range of forms of modification of SPEs opens a great field of applications for these electrodes. The composition of the printing inks may be altered by the addition of very different substances such as metals, metal oxides, enzymes, polymers, electrochemical mediators, complexing agents, etc. On the other hand, the possibility also exists of modifying the manufactured electrodes by means of depositing various substances on the surface of the electrodes such as metal films, polymers, enzymes, etc. Furthermore, great advancements have been achieved in the fabrication of SPEs by the use of nanomaterials, such as Au, Ag, Pt, Pd or other metal nanoparticles, carbon nanotubes (CNTs) or graphene-based inks that have the ability to enhance the immobilization efficiency of biological molecules and to accelerate the electron transfer rate on the surface of the electrodes.
One of the main advantages associated with these miniaturized electrochemical sensors is the reduction of sample volume required (a few microliters), which helps in reducing the overall size of the diagnostic system. Furthermore, these electrodes don’t have the need of tedious pre-treatment steps, their surfaces can be easily modified to fit multiple purposes and they don’t need highly trained personnel either. The sensitivity, selectivity, low detection limits and easy operability of these small detection devices makes them excellent candidates for on-site and real-time sensing of different analytes.
Thank you very much for reading my blog and I hope that you were able to learn a little bit more about electrochemistry and screen printed electrodes.
Keep safe and until next time,
1.: Joseph Wang (200). Analytical Electrochemistry, Second Edition. Wiley-VCH
2.: Parameters, E. (1976). Princeton Applied Research. Analytical Chemistry, 48(2), 129A–129A. https://doi.org/10.1021/ac60366a732
3.: Taleat, Z., Khoshroo, A., & Mazloum-Ardakani, M. (2014). Screen-printed electrodes for biosensing: A review (2008-2013). Microchimica Acta, 181(9–10), 865–891. https://doi.org/10.1007/s00604-014-1181-1