About gerogioschatzigeorgiou

I'm a biologist teacher and coodrinator of European projects at the 2nd General Lyceum of Oreokastro - Thessaloniki, Greece., such as Erasmus+ and etwinning.

Comparison of dye-sensitized solar cells with various dyes of plant origin

Τhe STEM Activity took place the days 26 and 27/4/2022, on the Science lab of 2nd General Lyseum of Oreokastro – Greece.

Teachers: Georgios Chatzigeorgiou (Biologist), Eftychia Karagianni (Physicist), Polyxeni Siorou (Physicist)

Mentors: Alexandros Terzopoulos, Christos Chatzigeorgiou

Students: E.K., D.K., E.A.,S.V., A.K., R.I.

We would like to express our utmost gratitude to Mr Paschalis Karakaris, Principal of the 2nd General Lyceum of Oraiokastro, for her continuous help and support in implementing the STEM activity in our school.

In this activity we study an alternative technology for the production of electricity from the conversion of solar energy, namely dye-sensitized solar cells (DSSC or Grätzel cells). Current commercially available photovoltaics consist of crystalline plates or films of semiconductors, typically silicon or GaAs. Dye-sensitized cells, on the other hand, rely on the photoelectrochemical system resulting from the adsorption of a dye (photosensitizer) to a mesoporous dielectric material (photodiode, usually titania TiO2), together with a cathode and an electrolyte. The electronic properties of the system are analogous to the conventional semiconductor; these involve transfer of electrons to the conduction band of the photodiode’s TiO2 to the photochemically excited photosensitizer.

In our proposed activity students constructed themselves some typical Grätzel cells (using a photodiode from FTO glass and pulverized TiO2, a cathode from identical FTO glass with surface-deposited soot, and iodine-triiodide electrolyte). The differentiation of our study concerns the photosensitizer, where instead of the expensive and toxic ruthenium dyes usually listed in literature, we used natural dyes extracted from different plants. The photovoltaic response of the cells was investigated by the students with measurements to record the current-voltage curve, from which characteristic quantities to compare the cells’ performance were obtained.

This activity explores topics such as new technologies for more accessible solar energy use, semiconductor properties, circuit measurements, and the use of natural materials in devices with positive environmental prospects. The goal is the successful construction of dye-sensitized cells in the school laboratory and the comparison of plant dyes as photosensitizers, wishing to demonstrate the most suitable for photovoltaic applications. The Municipality of Oraiokastro has provided financing for this work which has been an easy endeavor, as low cost is another of the advantages of the solar cell type that we have studied.

Experimental MethodsMaterials


1. Add 6 g of TiO2 powder in a mortar, followed by 2–3 mL of vinegar. Grind until all the clumps are broken. Continue adding vinegar in 1 mL integrals whilst continuously grinding, until a total of 9 mL is added. The mixture (paste) must be uniform at the end.

2. Gently mix a drop of dishwashing liquid with 1 mL of distilled water. Add this solution slowly over the paste, taking care not to produce bubbles. Allow the suspension to equilibrate.

3. Clean two conductive SnO2-coated glass slides using ethanol. The students need to previously identify the conductive side with a multimeter (the conductive side must have a resistance of 10–30 Ω).

4. Place the two slides on the bench, one with the conductive side up and the other conductive side down, and cover the edges with adhesive tape (covering 5-8 mm) confirming that there are no air bubbles between the tape and glass.

5. Using a glass rod, spread a thin uniform layer of paste on the upper edge of the conductive side. Allow the film to dry slightly and remove the tape.

6. Dry the slide by placing it on a heating plate (450 °C for approx. 30 minutes), with the conductive side facing up. The paste layer will initially turn purple-brown and then eventually white. When this happens, stop the heating, keeping the slide on the hotplate.

7. After it cools down to room temperature, record the surface of the membrane (the piece of slide covered by the paste).

8. To prepare the counterelectrode, clean a second conductive glass slide and then apply the catalytic carbon coating (i.e. rub lightly with a soft pencil) on the conductive side.

9. Hold the conductive side with tweezers over a low flame. Let soot collect on the surface of the plate for no more than 30 seconds. Change the position on the plate with the tweezers and cover the rest of the corner with soot in the same way, making sure that the whole slide is covered.

Now that the electrodes have been prepared, we manufacture the dye-sensitized solar cell.

Cell construction and evaluation

A. Use a spatula to mix some blueberries or cherries in a beaker. Then filter the solution into a Petri dish using a coffee paper filter, adding a few drops of distilled water if necessary.

B. Using tweezers, place the photoelectrode in the Petri dish, with the conductive side facing down, taking care not to scratch the film.

C. When the staining is completed, carefully remove the plate and make sure that there are no white spots to be seen. Rinse the slide with ethanol and dry it.

D. Place the counterelectrode down on the slide, keeping a distance between the slides.

E. Attach the connecting clips to the edges of the slides. Place a few drops of electrolyte along the edge and let it pass through the strip, opening the clips slightly. The photovoltaic is now ready for operation.

We then measured the performance of the cell under a halogen lamp, by orienting the cell so that the photoelectrode sees the lamp in a consistent manner. We used a multimeter to measure the open circuit potential and short circuit current.

We then connected the cell to a 500 Ω potentiometer to create the circuit shown in the diagram, and sequentially increased the resistance through the potentiometer while using the multimeter to measure the voltage and current.

A STEM and IBSL activity on enzymes: Studying gas-evolving enzymatic reactions by measuring produced gas volume

Authors: GEORGIOS CHATZIGEORGIOU, biology teacher, 2nd General Lyceum of Oreokastro, Greece, ALEXANDROS TERZOPOULOS, Mentor

We would like to express our utmost gratitude to Ms Konstantina Sarantavga, Principal of the 2nd General Lyceum of Oraiokastro, for her continuous help and support in implementing the STEM activity in our school.

General overview of enzymes

Enzymes are proteins capable of catalysing biochemical reactions in living organisms. As biocatalysts, they accelerate such reactions by lowering the activation energy thereof. Enzymes possess a varying degree of specialisation with respect to the reactants (substrates) of the reactions they catalyse; for their action, the binding of the substrate to the region of the protein known as the active site is required (in a lock-and-key manner). The velocity of enzymatic reactions is affected by temperature, substrate and enzyme concentration, binding affinity, pH etc. The enzyme function may be halted or increased by the presence of various substances (e.g. inhibitors, activators, allosteric effectors). Inhibition may be reversible or non-reversible.

Relevance to school curriculum-Benefits of our approach

The subject and encompassed disciplines are part of the curriculum for the General Orientation Biology course mandatorily taught in the 2nd Class of the General Lyceum (5th year of secondary education) in Greece. Enzymes specifically are taught within the framework of Chapter 3 “Metabolism”, section “Enzyme-Biocatalysts”. The time allocated for this section is one class sessions for the theoretical part, and an additional 1-2 hours to complete the experimental section designed herein.

The teaching approach we followed replaces the typical “dry” theory-repetitive presentation of this subject in the class with inquiry-based learning, including a hands-on experience in the lab with a strong visual stimulus. In our first implementation, 15 students participated (most of them girls) who showed great interest in the way the STEM fields of Biology and Chemistry were explored with this activity.

Students in the lab
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Let’s play Games and Learn about Climate Change and Natural Disasters

Georgios Chatzigeorgiou*, biologist, Alexia Fragkouli*, English language teacher, Eftychia Karagianni*, physicist, MD electronic physics
*2nd General Lyceum of Oreokastro, Greece

In the context of environmental projects run by our school and foremost of the Erasmus+ project “Effects of Human Activities on Natural Disasters – eHAND”, a group of students and teachers from the 2nd General Lyceum of Oreokastro became actively involved in the collection of data on natural disasters in Greece. Several working groups were created, each undertaking to gather material relating to: earthquakes, volcanic eruptions, floods, fires, and landslides, respectively.

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Earthquake safety tips’ lesson during the eHAND Erasmus+ «Enceladus» meeting in Oreokastro 23-27 April 2018

What is an earthquake? Do all earthquakes cause problems? What do we need to do to be prepared to deal with an earthquake?

An earthquake is a natural phenomenon that often affects Greece and other countries on the planet. Most earthquakes that occur in our country do not cause any particular problems, but some are very strong and have an impact on humans and buildings.

The Earthquake Planning and Protection Agency recommends that we be prepared to be able to protect ourselves during an earthquake and also to have the appropriate anti-earthquake behavior after the vibration.

In the lesson that took place on the first day of the eHAND Erasmus + «Enceladus» Meeting in Oreokastro, the students of the seven schools that participated had to:

Use the material they had recently uploaded on the web, answering questions about what we do before, during and after the earthquake. https://spark.liceodesio.gov.it/mod/wiki/view.php?id=3633

Create transnational groups with the goal of reading the material posted by the pupils of each school/country and to record 3 tips that they consider most important for the three phases (before, during and after)
Present the tips they have chosen to the other two groups

The results and material were used to create the booklet on the last day of the meeting. (http://blogs.sch.gr/2lykoraiok/2018/05/01/getting-ready-for-an-earthquake-students-booklet-during-the-ehand-erasmus-enceladus-meeting-in-oreokastro-greece/)


Minerals: the gifts of the earthquakes and the volcanoes in Aegean by Vasilios Melfos, Assistant Professor, eHAND project , «Enceladus» meeting in Oreokastro, 23-27 April 2018

Minerals: the gifts of the earthquakes and the volcanoes in Aegean

by Vasilios Melfos, Assistant Professor


School of Geology, Aristotle University of Thessaloniki

Mineral raw materials are crucial for the development of the modern societies, the environmentally friendly technologies and the Hi-Tech industrial products. Without them, there wouldn’t be any smartphones, laptops, or cars. They are extracted from large open pits or underground mines. Greece has a very unique geological history! The subduction of Africa beneath Eurasia is one of the most important geological phenomena in the world accompanied by volcanoes and earthquakes. Volcanoes in Aegean did not bring only disasters. Their action caused numerous mineral deposits, which have been used by the inhabitants since the Prehistoric times. Many Aegean islands were very wealthy thanks to the mineral raw materials.