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PEOPLE@HES-SO – Annuaire et Répertoire des compétences

PEOPLE@HES-SO
Annuaire et Répertoire des compétences

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Scholten Ulrich

Scholten Ulrich

Professeur HES associé

Compétences principales

Chemische Grundlagen

Nasschemische Analysen

Beratung von Studieninteressierten

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Contrat principal

Professeur HES associé

Téléphone: +41 26 429 67 11

Bureau: HEIA_B20.05

Haute école d'ingénierie et d'architecture de Fribourg
Boulevard de Pérolles 80, 1700 Fribourg, CH
HEIA-FR
Institut
ChemTech - Institut des technologies chimiques
BSc HES-SO en Chimie - Haute école d'ingénierie et d'architecture de Fribourg
  • Allgemeine und anorganische Chemie
  • Chemisches Grundpraktikum
  • Bachelorarbeiten

2021

Distance teaching in chemistry :
Article scientifique ArODES
opportunities and limitations

Véronique Breguet Mercier, Ulrich Scholten, Richard Baltensperger, Ludovic Gremaud, Michal Dabros

CHIMIA International Journal for Chemistry,  2021, vol. 75, no. 1/2, pp. 58-63

Lien vers la publication

Résumé:

Remote teaching in the tertiary education sector is a relatively common practice, and the implementation of digital solutions in chemistry teaching offers many new opportunities and tools. A survey was conducted after 3 months of emergency remote teaching linked to the COVID-19 pandemic and showed that half of the students estimated it was difficult to study remotely, and reported they had to invest more time compared to classroom teaching, which led to a drop in motivation. Professors also noted that the time necessary to invest in order to produce digital teaching content was enormous. Massive open online laboratories (MOOLs) and process simulators are interesting tools, but practical lab work and related know-how cannot fully be replaced by digital techniques. Finally, it appeared that the professor–student interaction is very important in the distance-learning process, and that a high level of pedagogical (inter)activity is mandatory to maintain motivation and better quality of teaching and learning.

2009

Reduction of Ferricytochrome c Catalyzed by Optically Active Chromium(III) Complexes
Article scientifique

Scholten Ulrich, Klaus Bernauer, Céline Diserens, Michel Meyer, Helen Stoeckli-Evans, Dominique Lucas, Ludovic Stuppfler

Journal of Inorganic Chemistry, 2009 , vol.  48, no  23

Lien vers la publication

Résumé:

The reduction rates of horse heart ferricytochrome c by amalgamated zinc or by electrolysis at fixed potential on a mercury pool as the cathode have been measured in a buffered solution at pH 7.5 by absorption spectrophotometry. In both cases, the reaction was strongly accelerated by the presence of the optically active complexes Λ-[CrIII((S,S)-promp)H2O]+ (H2promp = N,N′-[(pyridine-2,6-diyl)bis(methylene)]-bis[(S)-proline]), Δ-[CrIII((R,R)-alamp)H2O]+ (H2alamp = N,N′-[(pyridine-2,6-diyl)bis(methylene)]-bis[(R)-alanine]) and Λ-[CrIII((S,S)-alamp)(H2O)2]+. These were shown to undergo reversible one-electron reduction to the corresponding labile chromium(II) species by cyclic voltammetry (CV), although the diaquo Λ-[CrIII((S,S)-alamp)(H2O)2]+ compound behaved differently than the two others. The cyclic voltammogram evidenced a strong catalytic reduction wave below −1.1 V/SHE overlapping with the Cr3+/Cr2+ couple, which has been attributed to the catalytic reduction of hydroxonium ions to molecular hydrogen. Although stable in the second time range as demonstrated by CV, the chromium(II) complexes exist in solution only as short-lived species in the absence of protein and are rapidly reoxidized to the initial trivalent state, thus preventing their isolation even under anaerobic conditions. However, their lifetime was found to be long enough to catalyze the reduction of the ferric heme moiety of cytochrome c according to an electron-transfer-mediated reaction. Both chemical and electrochemical processes were found to follow zero-order kinetics. It could therefore be safely concluded that the rate-determining step is associated to the electron transfer from transient chromium(II) complexes to the protein and not to the in situ generation of the metallic reducing agent.

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