Chiang Mai Journal of Science

     This study advances the valorization of spent coffee grounds (SCG) by extracting lignin and oils to develop novel poly(lactic acid) (PLA) composite materials for high-potential use in UV-blocking packaging applications. SCG separated the oil by a dissolving process with hexane, and lignin was sedimented by an acidification process using sulfuric acid. Thus, the morphology and crystallinity of lignin were characterized by scanning electron microscope (SEM) and X-ray diffraction (XRD), and the functional groups of lignin and oil were investigated by Fourier transform-infrared (FT-IR) spectroscopy. It was found that the powder forms with an amorphous region. The oil extracted illustrated the functional groups of fatty acids. The oil was blended into the PLA matrix at 1, 3, 5, and 7 phr, and lignin composites were prepared at 1, 3, and 5 phr. The morphological, mechanical, thermal, and optical properties of the blends and composites were analyzed using SEM, universal testing machine (UTM), differential scanning calorimeter (DSC), and UV-Vis spectrophotometer. The optimum formulation at 1 phr of lignin and 5 phr of oil blends exhibited the best mechanical properties and strong UV-Vis absorption. Furthermore, PLA blends and composites incorporating these optimized ratios demonstrated high toughness and excellent UV-blocking performance. This work presents a promising bio-circular-green economy (BCG) model strategy by converting coffee waste into value-added materials for high-performance biodegradable polymer improvement and environmentally friendly packaging applications.

     In this work, we reported a rose bengal-modified EuTA framework (denoted as RSO-EuTA) for trinitrophenol (TP) optical recognition. The EuTA (TA = trimesic acid) framework was applied as supporting substrate, and a rose bengal molecule was used as the sensing probe with a loading level of 12 wt%, respectively. EuTA’s absorption in the visible region was proportional to TP concentration, resulting in colorimetric sensing. EuTA’s rose bengal emission was proportional to TP, but its Eu emission was inversely proportional to TP, resulting in ratiometric fluorescent sensing. These two sensing modes had good selectivity and linear sensing response, with fitting equations of A/A0 = 1.4890+0.1906*[TP] (LOD = 1.7 μM) and F554 nm/F615 nm = 0.1242+0.0336*[TP] (LOD = 2.3 μM). Its sensing mechanism was the combination of rose bengal structural transformation triggered by TP and energy transfer between TP and EuTA. RSO-EuTA confirmed its superior sensing performance by offering two sensing modes and naked-eye detection.