RESUMEN
Core-shell gold-silver cuboidal nanoparticles were produced, with either concave or straight facets. Their incubation with a low concentration of chiral l-glutathione (GSH) biomolecules was found to produce near UV plasmonic extinction and induced circular dichroism (CD) peaks. The effect is sensitive to the silver shell thickness. The GSH molecules were found to cause redistribution of silver in the shell, removing silver atoms from edges/corners and re-depositing them at the nanocuboid facets, probably through some redox and complexation processes between the silver and thiol group of the GSH. Other thiolated chiral biomolecules (and drug molecules) did not show this effect. The emerging near UV surface plasmon resonance is a silver slab resonance, which might also possess some multipolar resonance nature. The concave-shaped nanocuboids exhibited stronger induced plasmonic CD relative to the nanocuboids with straight facets.
RESUMEN
The formation of red-emissive optical centers in carbon dots based on citric acid and formamide was investigated by varying the synthesis parameters with focus on finding optimalânecessary and sufficientâamount of precursors to decrease byproduct amount and to increase the chemical yield of red-emissive carbon dots. The emission is observed at 640 nm excited at 590 nm and quantum yield reaches up 19%. A high chemical yield of carbon dots of 26% was achieved at an optimal molar ratio of citric acid to formamide of 1:4.
RESUMEN
Self-assembly of photo-responsive molecules is a robust technology for reversibly tuning the properties of functional materials. Herein, we probed the crucial role of surface-adsorbate interactions on the adsorption geometry of stilbene-functionalized N-heterocyclic carbenes (stilbene-NHCs) monolayers and its impact on surface potential. Stilbene-NHCs on Au film accumulated in a vertical orientation that enabled high photoisomerization efficiency and reversible changes in surface potential. Strong metal-adsorbate interactions led to flat-lying adsorption geometry of stilbene-NHCs on Pt film, which quenched the photo-isomerization influence on surface potential. It is identified that photo-induced response can be optimized by positioning the photo-active group in proximity to weakly-interacting surfaces.
RESUMEN
Site-dependent selectivity in oxidation reactions on Pt nanoparticles was identified by conducting IR nanospectroscopy measurements while using allyl-functionalized N-heterocyclic carbenes (allyl-NHCs) as probe molecules. Following exposure to oxidizing conditions the allyl groups in NHCs that were located on the center of Pt nanoparticles were oxidized to hydroxyl while those located on the nanoparticle's periphery were oxidized into carboxylic acid. The superior reactivity on the periphery of the nanoparticles was correlated to higher density of low coordinated atoms on these surface sites.
RESUMEN
The development of chemically addressable N-heterocyclic carbene (NHC) based self-assembled monolayers (SAMs) requires in-depth understanding of the influence of NHC's anchoring geometry on its chemical functionality. Herein, it is demonstrated that the chemical reactivity of surface-anchored NO2-functionalized NHCs (NO2-NHCs) can be tuned by modifying the distance between the functional group and the reactive surface, which is governed by the deposition technique. Liquid deposition of NO2-NHCs on Pt(111) induced a SAM in which the NO2-aryl groups were flat-lying on the surface. The high proximity between the NO2 groups and the Pt surface led to high reactivity, and 85% of the NO2 groups were reduced at room temperature. Lower reactivity was obtained with vapor-deposited NO2-NHCs that assumed a preferred upright geometry. The separation between the NO2 groups in the vapor-deposited NO2-NHCs and the reactive surface circumvented their surface-induced reduction, which was facilitated only after exposure to harsher reducing conditions.
