Christian Elsner

The occurrence of micropollutants in the environment is an emerging issue. Diclofenac, a non-steroidal anti-inflammatory drug, is one of the most frequently detected pharmaceuticals in the environment worldwide. Diclofenac is transformed by UVA light into different products with higher toxicity. The absorbance of the transformation products overlaps with the absorbance of diclofenac itself and inhibits the ongoing photoreaction. By adding polyvinylidene difluoride (PVDF), the products adsorb to the surface of PVDF. Therefore, phototransformation of diclofenac and total organic carbon (TOC) removal is enhanced and the toxicity decreased. At 15 min and 18 h of UVA treatment, removal of diclofenac and TOC increases from 56% to 65% and 18% to 54%, respectively, when PVDF is present. The toxicity of a UVA treated (18 h) diclofenac solution doubles (from 5 to 10, expressed in toxicity units, TU), while no toxicity was detectable when PVDF is present during UVA treatment (TU = 0). PVDF does not need to be irradiated itself but must be present during photoreaction. The adsorbent can be reused by washing with water or ethanol. Diclofenac (25 mg L⁻¹) UVA light irradiation was monitored with high performance liquid chromatography (HPLC), UV-Vis spectroscopy and by analysing the decrease of TOC. The toxicity towards Vibrio fischeri was examined according to DIN EN ISO 11348-1: 2009-05. Density functional theory (DFT) was used to simulate the phototransformation products known in literature as well as further products identified via gas chromatography–mass spectrometry (GC-MS). The absorption spectra, reaction enthalpies (ΔH) and Gibbs free energy of reactions (ΔG) were calculated. The combination of UVA irradiation of diclofenac with adsorption of photoproducts to PVDF is unique and opens up new possibilities to enhance removal of pollutants from water.

Hydrolysis studies of photo-switchable N-maleyl-amino acid-(4-phenylazophenyl) esters of Ala, Gly, Met, Phe, and Pro were performed using the proteases trypsin and chymotrypsin. It has been found out that the cis-isomers were hydrolyzed faster than the trans-isomers. In dependence of the amino acid in the P1 position the velocity graduation is Phe > Met > Ala > Gly > Pro for trypsin and Phe ≫ Met > Ala > Gly > Pro for chymotrypsin for both isomers.

Hydrogels have shown a great potential as materials for drug delivery systems thanks to their usually excellent bio-compatibility and their ability to trap water-soluble organic molecules in a porous network. In this study, poly(ethylene glycol)-based hydrogels containing a model dye were synthesized by ultraviolet (UV-A) photopolymerization of low-molecular weight macro-monomers and the material properties (dye release ability, transparency, morphology, and polymerization kinetics) were studied. Real-time infrared measurements revealed that the photopolymerization of the materials was strongly limited when the dye was added to the uncured formulation. Consequently, the procedure was adapted to allow for the formation of sufficiently cured gels that are able to capture and later on to release dye molecules in phosphate-buffered saline solution within a few hours. Due to the transparency of the materials in the 400–800 nm range, the hydrogels are suitable for the loading and excitation of photoactive molecules. These can be uptaken by and released from the polymer matrix. Therefore, such materials may find applications as cheap and tailored materials in photodynamic therapy (i.e., light-induced treatment of skin infections by bacteria, fungi, and viruses using photoactive drugs).

Oligopeptides containing internal π-system units are shown to self-assemble in water near nanoparticles into fibrillar nanostructures. We have investigated the biopolymer hybrid monomer of the overall structure `peptide-π-system-peptide' with the sequence VDFAG – perylene diimide (PDI) – GAFDV in the presence of Ag-nanoparticles. Unique to these self-assembling monomers is the fact that the π-conjugated unit has been directly embedded within the peptide backbone by way of a special synthetic coupling. The symmetric peptide-based molecular design enforces intimate π-π communication within the aggregates after self-assembly, making these nano structures attractive for optical or electronic applications. The assembly process can in principle be followed by the change in optical spectra of the monomer and ordered monomer π-systems. Here we show that the Ag-nanoparticles act as seeds for the fibrillation, which makes the fibrils grow in a defined fashion and the supramolecular assembly can be followed via the optical spectrum of the plasmon resonances of the silver nanoparticles, which depend sensitively upon the local environment, making the optical plasmon resonance spectra a nice probe for the assembly process, as well as the interaction of monomers and fibrillar structures in contact with the nanoparticles. While it has been known that these systems may aggregate under certain conditions towards nano fibrils the new aspect here is the controlled and accelerated fibrillation near silver nanoparticles, which results in fibrils of 15–150 nm in diameter and up to 10 μm long, partially incorporating the seed nanoparticles. This approach provides a novel avenue to synthesize bioorganic-hybrid systems (in high yields) in contact with Ag metal nanoparticles and possibly enables us to control the location of growth for the materials in future applications.

The process of plasma curing of functional acrylates has been studied. For these purposes, a nitrogen plasma generated by a flat and a cylindrical electrode configuration, respectively, was used to provide both planar and 3D curing conditions. In selected cases, a double bond conversion >95% was observed by ATR‐IR spectroscopy for a 15 µm (wet thickness) acrylate coating even without the addition of any photoinitiator. Compared to UV curing, the surface energy of the cured substrates was significantly higher when plasma curing was applied (>70 mN · m⁻¹); however, the hydrophilic surfaces experienced hydrophobic recovery. Finally, the generation of microstructures on uniaxially oriented substrates during the plasma process was studied and conditions for their tailor‐made creation are suggested. magnified image