Investigating the Recycling Potential of Glass Based Dye-Sensitized Solar Cells-Melting Experiment.

The effects of climate change are becoming increasingly clear, and the urgency of solving the energy and resource crisis has been recognized by politicians and society. One of the most important solutions is sustainable energy technologies. The problem with the state of the art, however, is that production is energy-intensive and non-recyclable waste remains after the useful life. For monocrystalline photovoltaics, for example, there are recycling processes for glass and aluminum, but these must rather be described as downcycling. The semiconductor material is not recycled at all. Another promising technology for sustainable energy generation is dye-sensitized solar cells (DSSCs). Although efficiency and long-term stability still need to be improved, the technology has high potential to complement the state of the art. DSSCs have comparatively low production costs and can be manufactured without toxic components. In this work, we present the world' s first experiment to test the recycling potential of non-toxic glass-based DSSCs in a melting test. The glass constituents were analyzed by optical emission spectrometry with inductively coupled plasma (ICP-OES), and the surface was examined by scanning electron microscopy energy dispersive X-ray (SEM-EDX). The glass was melted in a furnace and compared to a standard glass recycling process. The results show that the described DSSCs are suitable for glass recycling and thus can potentially circulate in a circular economy without a downcycling process. However, material properties such as chemical resistance, transparency or viscosity are not investigated in this work and need further research.

Melting Behavior of Heterogeneous Polymer Bulk Solids Related to Flood Fed Single Screw Extruders.

Melting models for flood fed single screw extruders, like the Tadmor model, describe the melting of pure thermoplastic polymers. However, the melting behavior of heterogenous polymer systems is of great interest for recycling issues, for example. In this work, the melting of polymer mixtures and that of pure bulk polymers by the drag induced melt removal principle is examined both theoretically and experimentally. The applied model experiments represent the melting of the solid bed at the barrel in single screw extruders. As polymer pellet mixtures, polypropylene-homopolymer mixed with polypropylene-block-copolymer, high density polyethylene, polyamide 6, and polymethylmethacrylate were studied using different mixing ratios. The melting rate and the shear stress in the melt film were evaluated dependent on the mixing ratio. The results show that when processing unfavorable material combinations, both shear stress and melting rate can be far below that of pure materials, which was also confirmed by screw extrusion and screw pull-out experiments. Furthermore, approaches predicting the achievable melting rate and the achievable shear stress of polymer mixtures based on the corresponding values of the pure materials are presented.

Synthesis of Oligonucleotides Containing 2'-N-alkylaminocarbonyl-2'-amino-LNA (2'-urea-LNA) Moieties Using Post-Synthetic Modification Strategy.

The post-synthetic modification of an oligonucleotide is a powerful strategy for the synthesis of various analogs of the oligonucleotide, aiming to achieve the desired functions. In this study, we synthesized the thymidine phosphoramidite of 2'-N-pentafluorophenoxycarbonyl-2'-amino-LNA, which was introduced into oligonucleotides. Oligonucleotides containing a 2'-N-pentafluorophenoxycarbonyl-2'-amino-LNA unit could be isolated under ultra-mild deprotection conditions (50 mM K2CO3 in MeOH at room temperature for 4 h). Moreover, by treatment with various amines as a post-synthetic modification, the oligonucleotides were successfully converted into the corresponding 2'-N-alkylaminocarbonyl-2'-amino-LNA (2'-urea-LNA) derivatives. The duplex- and triplex-forming abilities of the synthesized oligonucleotides were evaluated by UV-melting experiments, which showed that 2'-urea-LNAs could stabilize the nucleic acid complexes, similar to the proto-type, 2'-amino-LNA. Thus, 2'-urea-LNAs could be promising units for the modification of oligonucleotides; the design of a substituent on urea may aid the formation of useful oligonucleotides. In addition, pentafluorophenoxycarbonyl, an amino moiety, acted as a precursor of the substituted urea, which may be applicable to the synthesis of oligonucleotide conjugates.