Inspiring the scientists of tomorrow with fascinating experiments

Sixty children were looking in awe at those ten weird persons, dressed in white robes and strange glasses: Were these aliens invading their kindergarten Auf dem Backenberg (Bochum) on that morning of the 11th of October? The reality, they were about to discover, was more down to Earth than that, but fascinating nonetheless.

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The JCF Bochum at work ©JCFBochum2016

We, the men and women in white, were chemists of the JungChemikerForum Bochum – the 1998 founded local group of young members of the GDCh. And we had brought several intriguing chemical experiments that encouraged them to participate and solve some of nature’s mysteries.

Why don’t water and oil get along?

Ranging from only two-year-olds up to fourth graders, our audience was very mixed. Still, fascination unified them from the very beginning. In their first experiment they had to mix water with oil – but wait, they don’t want to mix?!? That result was quite unexpected for most of our little experimentalists, but we soon explained:

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Water and else ©JCFBochum2016

The difference in polarities and intermolecular forces between water and oil makes them like cats and dogs – they form small groups of one kind, but simply don’t get along with each other because of their differences. But what if we take a drop of ink and let it fall into the mixture (of course after multiple attempts with these tricky pipettes)? Ink seems to prefer the company of the polar water molecules, making for a nice visualization of the underlying principles of solute-solvent interactions.

Is brushing your teeth really necessary?

The little explorers then switched to the next experiment: We had to convince them that brushing your teeth in the morning and evening wasn’t just a huge waste of time – a challenge indeed! As model for their teeth a hard-boiled egg was chosen that first had to be properly coated on one half with tooth paste. The children performed this task with vigor and enthusiasm (though maybe not as diligently as we had expected, so we cheated by secretly coating the eggs some more).

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Brush the egg ©JCFBochum2016

Next, the egg was lowered into a glass full of vinegar, symbolizing everyday’s assortment of acids passing our teeth. Also the young participants understood the aggressive properties of this vile liquid after putting their noses over the glass as could be told from the grimaces they made. Having put the egg into the vinegar they observed that bubbles were only formed on the uncoated side of the egg. This being probably the first time these children had ever consciously perceived a chemical reaction our JCF instructors very slowly explained: They carefully introduced the concepts of acids and bases to them, how the stuff that had attacked their noses earlier would react with the egg shell (i. e. calcium carbonate, see below) and produce carbon dioxide, the same gas they knew from soda or lemonade.

2 CH3COOH + CaCO3 –> CO2 + H2O + Ca(CH3COO)2
Acetic acid + Calcium carbonate –> Carbon dioxide + Water + Calcium acetate

However, how come the side they had coated with tooth paste earlier did not show any bubbles? This, we explained, was because the tooth paste contained fluoride, a special ion that helps to prevent damage to teeth by reacting with the hydroxylapatite contained therein and making them more acid-resistant:

Ca5(PO4)3(OH) + F– –> Ca5(PO4)3F + OH
Hydroxylapatite + Fluoride –> Fluorapatite + Hydroxyde

What magical substance surrounds us all?

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Chemical tools ©JCFBochum2016

Finally, the children arrived at their last experimental setup, the sight of gummy bears having magically attracted them there. But before they could find out what to do with the sweets (and possibly how they tasted) they had to perform a deceptively easy experiment by submerging an empty glass upside down in a bowl of water. When asked to get out the glass and feel the bottom of it surprise crossed their faces: How could it be that the inside stayed dry? There had been nothing in the glass to prevent water from coming in… or had there been? Could it be that something surrounds all of us at any given time and thus is also inside seemingly empty glasses? When asked these questions the children got thinking: “Nothing”, some children pouted, “the environment” was another cute attempt at solving this riddle. “The sun” was actually an answer that showed quite a lot of insight since light is of course an entirely valid answer.

After some coaxing and hinting the small researchers indeed arrived at air as the substance we were searching for, but as true scientists were very skeptic about it. An invisible substance that is everywhere? We clearly had to visualize this mystical air to convince them. So we let them produce some bubbles by slightly tilting the submerged glass and thus see the otherwise invisible air. As crowning experiment we asked the children to let two gummy bears inside a small boat (made from aluminum foil) take a dive to the bottom of the water bowl without letting them get wet! The kindergartners soon figured out that they could use the same protective hull of air inside the glass to achieve this task and received some sweets for their accomplishment.

We were very delighted by the children’s remarkable enthusiasm to experiment and eagerness to learn about nature’s secrets. Although they probably did not realize it, they had experienced some of the fundamental principles of Solvation Science: The interactions of and interfaces between hydrophilic and hydrophobic solvents (water and oil), the preference of a polar molecule (ink) for water as polar solvent, acid-base reactions in aqueous media (egg shell plus vinegar), water as “tool” in experiments to probe and visualize certain effects (air bubbles). Besides teaching the children these important principles from physics and chemistry, another goal was to inform about them the puzzling work of chemists. Most of them had never even heard of us before and found our alien coats and safety-glasses very interesting. All in all, a very fascinating and instructive day for these small explorers!

This event has been organized in cooperation with the Young Spirits program of Evonik. Please contact us if you are also interested in teaching science to children, so we can supply you with contact to Evonik’s Young Spirits program or the actual procedures of the experiments described in this blog entry.


About the authors
dsc00024_aTim Schleif is a PhD student in the group of Prof. Sander working on matrix isolation experiments at the Ruhr-University Bochum since 2015. He is also the speaker of the JungChemikerForum Bochum that organizes talks and excursions for the students of the faculty.

 

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Christoph Schran is a PhDstudent in the group of Prof. Marx working on nuclear quantum effects at the Ruhr-Univeristy Bochum since 2016. As an active member of the JungChemikerForum Bochum, he organized the event at the kindergarten.

Solvation science exhibition ‘Völlig losgelöst’ hits the road in Recklinghausen

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Cable car in the museum ‘Strom & Leben’ © Lutz Tomala

There’s a cable car parked in the middle of a room, and a wall covered with radios. Switches, electricity generators and coils? There are so many of them that one expects Nikola Tesla to appear every second. Then, nearby a generator, there’s a table with colored chemical solutions. And in another room appear huge modules, similar to oversized overnight bags wide-open, portraying persons in space suits and explaining about chemistry in solution. Such a striking combination of physics and chemistry got the visitors’ attention at the museum ‘Strom & Leben’ in Recklinghausen on the 6th of November. It was the inauguration day of the Solvation Science exhibition ‘Völlig losgelöst’, taking a first detour since its launch in the Blue Square in Bochum at the beginning of 2016.

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Chemistry and physics © Lutz Tomala

“It’s wonderful news that this itinerant exhibition has finally hit the road. Scientific research is an exploratory expedition in the unknown, but the trip itself should not remain undisclosed to the public”, said at the opening Katrin Sommer, Professor for „Didaktik der Chemie” at RUB and one of the designers of the exhibition.

But what do solvation science and electricity have in common?  As the museum’s director Hanswalter Dobbelmann pointed out, “there is indeed a strong historic connection between chemistry and electricity. For example, the discovery of electricity dates back to the first attempts with chemical batteries made by Volta and Galvani.” But the links between chemistry and electricity are not only a thing of the past: “Solvation science is much important for current topics like energy storage”, said Prof. Dr. Havenith, speaker of the Cluster of Excellence RESOLV, “therefore, we currently witness increasing research on solvents used in energy storage media, with the aim to improve their efficiency as well as their safety”.

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The exhibition is open, the journey begins © Lutz Tomala

Under these premises, ‘Völlig losgelöst’ will occupy a well-deserved spot in the ‘Strom & Leben’ museum in Rechklinghausen until Spring 2017. Besides presenting the actors and the themes of the RESOLV cluster, the exhibition will offer visitors the possibility to perform small experiments related to solvation science. School classes from the 3rd to the 5th year have also the possibility to book a special experimental program and to dive for two hours into the world of solvents. In the end, as Dobbelmann, Havenith and Sommer hope, by showing the scientists’ journey through a new research expedition, ‘Völlig losgelöst’ might well electrify the young generations to hit the same road in the future.


About the Authors

EF3Emiliano Feresin is a science journalist, currently responsible for the outreach activities within the RESOLV cluster at RUB. Born and raised in Italy, he holds a Diploma and a PhD degree in chemistry. Driven by an innate curiosity for scientific stories, he completed his education with a master degree in science communication. Along the path he has written for outlets like Nature and Chemistry World and learned that the reader has always the last word.

@ RUB, Foto: Nelle

@ RUB, Foto: Nelle

Christian Strippel was born 1988 in Bochum and holds a M.Ed. in Chemistry and English. His (scientific) motto of life is: “Fortune favours the prepared mind.” – Louis Pasteur
He studied in Cambridge (UK) for one year and holds a Postgraduate Certificate of Education (Chemistry, University of Cambridge). Currently, he works on his Ph.D. project “Communication about scientific inquiry during experimentation”.

 

Embedding nanoparticles into porous materials for greener chemistry.

Chemical and pharmaceutical industries are constantly seeking new ways towards sustainable chemistry that allows for less waste production and reduced energy consumption during industrial processes. One way, which I investigated in my PhD research, would be to use nanoparticles to speed up chemical reactions – a process called catalysis.

Nanoparticles are tiny objects or combinations of several atoms that can be as small as 1 nm and show unique properties, different from the bulk material. Take gold, for example. We are used to its shapes and colors in jewelry, but gold nanoparticles show completely new properties, such as red color in solution or the ability to behave as a catalyst in an efficient and selective manner. Similarly, nanoparticles of Platinum (Pt) and Palladium (Pd) can also act as catalysts in various processes (i.e. hydrogenation, the reduction of organic compounds). Nanoparticles promise to be highly selective, to greatly increase the reaction rate and to lower energy consumption. However, one major disadvantage of nanoparticles is the tendency for aggregation and thus the loss of their unique catalytic properties.

MOFs support nanoparticles for catalysis

In my PhD, I successfully encapsulated catalytically active metal nanoparticles of Pt or a combination of Pt/Pd into stabilising support materials called metal-organic frameworks (MOFs), which prevent aggregation. Inside MOFs, the tiny metal particles could maintain their unique capacity to hydrogenate nitrobenzene-based compounds and additionally be very selective towards the target products. Moreover, I could show that the combination of bimetallic nanoparticles of Pt and Pd with MOFs can surpass the catalytic hydrogenation activity of the monometallic Pt nanoparticles. This alternative solution may help to reduce the costs for the use of noble metals, replacing parts of the expensive Pt by Pd.

Especially in view to catalysis, MOFs exhibit two beneficial properties: Storage capacity (sponge-like property) and molecular selectivity (sieve-like) – in fact, due to the unique microporous structure of the support, the embedded nanoparticles are only accessible by molecules that fit the dimensions of the MOF pores (see Figure 1). MOFs are porous materials, formed by interconnection of organic linker molecules and metal ions or clusters. Thereby, a three dimensional network with a huge inner surface area is formed, which simultaneously possesses enough space to accommodate small sized nanoparticles or other guest molecules and solvents (water, nitrogen, carbon dioxide). Hence, MOFs feature the ability to absorb and/or separate a certain amount of substances at the molecular level, very similar to sponges or sieves.

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Figure 1. Top: Schematic representation of encapsulated nanoparticles inside a MOF with shape-selective, catalytic properties. The smaller substrate A1 is able to infiltrate the framework and can be converted to the target product B at the embedded nanoparticles – the larger molecule A2 is instead unable to infiltrate the MOF. The MOF consists of metal clusters (blue tetrahedra) interconnected by organic linkers, building up a 3D structure, where metal nanoparticles are exclusively embedded. Bottom: hydrogenation of sterically different nitroarenes to the corresponding amines, where aniline is selectively produced (size selectivity).

In my work I choose the Zirconium-based metal organic framework named UiO-66, which appears in a 3-dimensional structures with tetrahedral and octahedral pore geometries. A major advantage of this particular MOF is its extraordinary high thermal and chemical stability against water, acids and several organic solvents. Therefore, UiO-66 represents an appropriate candidate for heterogeneous catalysis, while other MOFs would decompose during the applied catalytic conditions.

Low-cost bimetallic Pd/Pt into MOFs show promising catalytic activity

Following a template approach, we exclusively embedded preformed mono- and bimetallic Pt and Pd/Pt nanoparticles without undesired deposition at the outer surface of the porous material, which in fact represents the key feature for shape-selective catalysis. Then we elucidated the structural integrity of the material and the exact spatial distribution of the nanoparticles (fully embedded into the MOF crystals or not). For instance, powder x-ray diffraction (PXRD) measurements indicated the crystallinity of UiO-66, even after the encapsulation process; transmission electron microscopic (TEM) measurements showed the successful and exclusive encapsulation of the nanoparticles into the core of the MOF crystals.

Afterwards the materials were further studied for selective hydrogenation of nitrobenzene-based compounds to the respective anilines. Direct comparison of the embedded Pt and Pd/Pt NPs showed a much higher catalytic activity for the bimetallic species, while the shape-selective character, originating from the microporous MOF, was maintained. Hopefully, this may become another possible solution towards sustainable.

About the author:

picture2Christoph Rösler received his MSc in Inorganic Chemistry at RUB in 2012 – supervision of Prof. R. A. Fischer . During his Master thesis he visited the labs of Prof. H. Kitagawa at Kyoto University, designing metal nanoparticles, especially multiphase systems. Since 2013 he is a PhD student in the group of Prof. Fischer, tackling metal nanoparticle inclusion into metal-organic frameworks. He also investigated catalytic properties of NP@MOF composites at the the Instituto de Tecnología Química of Prof. A. Corma in Valencia.