Photo-Induced Assembly of Nanostructures Triggered by Short-Lived Proton Transfers in the Excited-State

Light stimulation was used to trigger the assembly of nanostructures by directly powering changes at the supramolecular level without incurring net chemical changes at the molecular level. Polyethylene imine, a polybase, was mixed in aqueous solution with sodium 1-naphthol-4-sulfonate, an aromatic alcohol, which, in the electronic excited-state, undergoes a short-lived increase in acidity. Excited-state proton transfers between these components were induced by photoexcitation, which led to the formation of hydrogen bonds in the ground-state. Ionic forces, π–π stacking, and hydrophobic effect provided further stabilization. The photoinduced formation of nanosized aggregates was detected by dynamic light scattering and atomic force microscopy. Absorption and emission spectroscopy were used to rule out photochemical reactions and elucidate the supramolecular arrangement

Polythiophene as a Double-Electrostatic Template for Zinc Oxide and Gold: Multicomponent Nano-Objects for Enhanced Photocatalysis

Using electrostatic self-assembly and electrostatic nanotemplating, a quaternary nanostructured system consisting of zinc oxide nanoparticles, gold nanoparticles, poly[3-(potassium-4-butanoate)thiophene-2,5-diyl] (PT), and methyltrioctylammonium chloride (MTOA) (PT–MTOA–ZnO–Au) was designed for aqueous photocatalysis. The PT–MTOA hollow sphere aggregates served as an electrostatic template for both individual inorganic nanoparticles controlling their morphology, stabilizing the nanoparticles, and acting as a photosensitizer. The hybrid structures included spherical ZnO nanoparticles with a diameter of d = 2.6 nm and spherical Au nanoparticles with d = 6.0 nm embedded in PT–MTOA hollow spheres with a hydrodynamic radius of RH = 100 nm. The ZnO nanoparticles acted as the main catalyst, while the Au nanoparticles acted as the cocatalyst. As a photocatalytic model reaction, the dye degradation of methylene blue in aqueous solution using the full spectral range from UV to visible light was tested. The photocatalytic activity was optimized by varying the Zn and Au loading ratios and was substantially enhanced regarding the components; for example, it was increased by about 61% using PT–MTOA–ZnO–Au compared to the composite without gold particles. A photocatalytic mechanism of the methylene blue degradation was proposed when catalyzed by these multicomponent nano-objects. Thus, a simple procedure of templating two different nanoparticle species within the same cocatalytically active template has been demonstrated, which can be extended to other inorganic particles, making a variety of task-specific catalysts accessible

Amphiphilic Pentaazamacrocyclic Manganese Superoxide Dismutase Mimetics

Five newly functionalized pentaazamacrocyclic manganese complexes, with variable lengths and amounts of the aliphatic groups (three compounds with one linear chain containing 12, 16, and 22 carbon atoms, i.e., Mn<b>L1</b>, Mn<b>L2</b>, and Mn<b>L3</b>, respectively, as well as two compounds containing two C12 and C16 chains, Mn<b>L4</b> and Mn<b>L5</b>, respectively) that are derivatives of the known SOD mimetic, Mn­(Me₂-Pyane), have been synthesized. These amphiphilic complexes were characterized by the ESI mass spectrometry, potentiometric titrations, light scattering, cyclic voltammetry, and direct stopped-flow determination of their SOD activity at pH 8.1 and 7.4 (in phosphate and HEPES buffers). The formation of supramolecular aggregates that predominantly exist in the solution as a defined micellar/nanostructure assembly, with an average 400 nm size, has been demonstrated for Mn<b>L1</b>. The biological effects of the selected complexes (Mn<b>L1</b> and Mn<b>L2</b>) on the superoxide level in cytosol and mitochondria have been tested, as well as their effects on the prevention of the lipid peroxidation induced by paraquat. Advantages and disadvantages of the lipophilic pentaazamacrocyclic manganese SOD mimetics in comparison to the corresponding nonsubstituted SOD active complex have been discussed