Just Add Luminol to Turn the Spotlight on Radziszewski Amidation

Production of Molecular Iodine via a Redox Reaction between Iodate and Organic Compounds in Ice

The abiotic mechanism of molecular iodine (I₂) production from iodate (IO₃^-) remains largely unknown. Here, we demonstrate the production of I₂ in the presence of IO₃^- and organic compounds in ice. When the solution containing IO₃^- (100 μM) and furfuryl alcohol (100 μM) at pH 3.0 was frozen at -20 °C, 13.1 μM of I₂ was produced with complete degradation of furfuryl alcohol after 20 min. However, there was little change in the IO₃^- and furfuryl alcohol concentrations in water at 25 °C. The production of I₂ in ice is due to the freeze concentration effect, which induces the accumulation of IO₃^-, furfuryl alcohol, and protons in the ice grain boundaries. This behavior facilitated the production of I₂ via a redox reaction between IO₃^- and organic compounds. The production of I₂ increased with increasing furfuryl alcohol concentration and decreasing pH. However, freezing temperature had a minor effect on the maximum production of I₂. The production of I₂ is highly dependent on the type of organic compounds. It was higher for organic compounds with higher electron-donating properties. This study suggests a new mechanism for I₂ production, which is helpful for predicting precisely the atmospheric I₂ budget in cold regions.

The horseradish smile: Demonstrating characteristic reactions of peroxidase in a visually appealing way

Easy and visually appealing demonstrations are precious tools for introducing students to the study of enzymes. However, they most often involve purified enzymes and dedicated techniques. Here, we propose a set of demonstrations, which require only fresh horseradish root and consumer chemicals, to help support biochemistry and enzymology courses from high school to the undergraduate level. Horseradish root is a naturally rich source of horseradish peroxidase, an enzyme with many relevant practical applications. Slices of horseradish root are used to demonstrate the characteristic reaction of horseradish peroxidase with hydrogen peroxide, the selective inhibition of this enzyme by dilute hydrochloric acid, its chromogenic reaction with N,N'-diethyl-p-phenylenediamine, and its ability to trigger the chemiluminescent reaction of luminol. © 2019 International Union of Biochemistry and Molecular Biology, 48(1):38-43, 2020.

Photocatalytic Lithography

Patterning, the controlled formation of ordered surface features with different physico-chemical properties, is a cornerstone of contemporary micro- and nanofabrication. In this context, lithographic approaches owe their wide success to their versatility and their relative ease of implementation and scalability. Conventional photolithographic methods require several steps and the use of polymeric photoresists for the development of the desired pattern, all factors which can be deleterious, especially for sensitive substrates. Efficient patterning of surfaces, with resolution down to the nanometer scale, can be achieved by means of photocatalytic lithography. This approach is based on the use of photocatalysts to achieve the selective chemical modification or degradation of self-assembled monolayers, polymers, and metals. A wide range of photoactive compounds, from semiconducting oxides to porphyrins, have been demonstrated to be suitable photocatalysts. The goal of the present review is to provide a comprehensive state-of-the-art photocatalytic lithography, ranging from approaches based on semiconducting oxides to singlet oxygen-based lithography. Special attention will be dedicated to the results obtained for the patterning of polymer brushes, the sculpturing of metal nanoparticle arrays, and the patterning of graphene-based structures.