Using experimental devices which do not show electroluminescence, we have previously found that photoluminescence of tris(8-hydroxyquinoline) aluminum $({\mathrm{AlQ}}_{\mathrm{3}}\mathrm{),}$ a widely used organic electroluminescent material, decreases under prolonged transport of holes. This leads to a conclusion that ${\mathrm{AlQ}}_{\mathrm{3}}$ cations are unstable, and to our proposal that the same mechanism is responsible for degradation of organic light-emitting devices (OLEDs) based on ${\mathrm{AlQ}}_{\mathrm{3}}.$ In this communication, we broaden our studies to include simultaneous electroluminescence and photoluminescence measurements on OLEDs containing thin ${\mathrm{AlQ}}_{\mathrm{3}}$ as the emitter layer. Results show that the decrease in the electroluminescence efficiency is indeed associated with degradation of the ${\mathrm{AlQ}}_{\mathrm{3}}$ in the vicinity of the hole transport layer interface.

Vegetable fibers are increasingly used in biocomposites, but there is a need for further development in utilizing by-products like cocoa husks. Three-dimensional printing, through Fused Filament Fabrication (FFF), is advancing rapidly and may be of great interest for applying biocomposite materials. This study focuses on developing innovative and fully biodegradable filaments for the FFF process. PLA filaments were prepared using cellulose fibers derived from cocoa husks (5% mass ratio). One set of filaments incorporated fibers from untreated husks (UCFFs), while another set utilized fibers from chemically treated husks (TCFFs). The fabricated materials were analyzed using scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and Fourier transform infrared (FTIR) techniques, and they were also tested for tensile strength. ANOVA reveals that both UCFFs and TCFFs significantly predict tensile strength, with the UCFFs demonstrating an impressive R² value of 0.9981. The optimal tensile strength for the filament test specimens was 16.05 MPa for TCFF8 and 13.58 MPa for UCFF8, utilizing the same printing parameters: 70% infill and a layer thickness of 0.10 mm. Additionally, there was an 18% improvement in the tensile strength of the printed specimens using the filaments filled with chemically treated cocoa husk fibers compared to the filaments with untreated fibers.

Lignocellulosic residues, such as cocoa bean shell (FI), are generated in large quantities during agro-industrial activities. Proper management of residual biomass through solid state fermentation (SSF) can be effective in obtaining value-added products. The hypothesis of the present work is that the bioprocess promoted by P. roqueforti can lead to structural changes in the fibers of the fermented cocoa bean shell (FF) that confer characteristics of industrial interest. To unveil such changes, the techniques of FTIR, SEM, XRD, TGA/TG were used. After SSF, an increase of 36.6% in the crystallinity index was observed, reflecting the reduction of amorphous components such as lignin in the FI residue. Furthermore, an increase in porosity was observed through the reduction of the 2θ angle, which gives the FF a potential candidate for applications of porous products. The FTIR results confirm the reduction in hemicellulose content after SSF. The thermal and thermogravimetric tests showed an increase in the hydrophilicity and thermal stability of FF (15% decomposition) in relation to the by-product FI (40% decomposition). These data provided important information regarding changes in the crystallinity of the residue, existing functional groups and changes in degradation temperatures. Graphical Abstract This work presents a new approach for solid state fermentation based on the study of structural changes caused by Penicillium roquefort, which is important to understand the changes in the lignocellulosic matrix after the fungus growth. The results provided important information regarding changes in the crystallinity of the residue, existing functional groups and changes in degradation temperatures. Consequently, they can help in proposals for the total use of the residual solid after fermentation, as well as contribute to reducing the lack of this information in the literature.