Platinum/carbon dots nanocomposites from palm bunch hydrothermal synthesis as highly efficient peroxidase mimics for ultra-low H2O2 sensing platform through dual mode of colorimetric and fluorescent detection.

Detection of hydrogen peroxide and glucose in nanomolar level is crucial for point-of-care medical diagnosis. It has been reported that human's central nervous system diseases such as Alzheimer's disease, Parkinson's disease, and even amyotrophic lateral sclerosis, are presumably caused H2O2 or reactive radical species (ROS). Sensing of H2O2 released from human biofluids, tissues, organ from metabolism disorder at ultra-low concentration assists for early identification of severe diabetis mellitus related to glucose, and heart attack, as well as stroke related to cholesterol. In this work, carbon dots (CDs) having an average diameter at 6.99 nm with highly photoluminescence performance were successfully synthesized from palm empty fruit bunch (EFB) using green and environmentally friendly process via hydrothermal condition. CDs acted well on peroxidase-like activity for H2O2 detection at room temperature, however their sensitivity on ultra-low H2O2 concentration needed to be improved. To enhance their reactivity on H2O2 nanozyme activity at room temperature, synthesis of hybrid metal nanoparticles (AgNPs and PtNPs) on CDs surface was established. The findings exhibited that CDs/PtNPs was the most suitable nanozyme achieving highly efficient peroxidase mimic for dual mode of colorimetric and fluorescent H2O2 sensing platform at very low limit of detection of 0.01 mM (10 nM) H2O2.

The Role of N and S Doping on Photoluminescent Characteristics of Carbon Dots from Palm Bunches for Fluorimetric Sensing of Fe3+ Ion.

This work aims to enhance the value of palm empty fruit bunches (EFBs), an abundant residue from the palm oil industry, as a precursor for the synthesis of luminescent carbon dots (CDs). The mechanism of fIuorimetric sensing using carbon dots for either enhancing or quenching photoluminescence properties when binding with analytes is useful for the detection of ultra-low amounts of analytes. This study revealed that EFB-derived CDs via hydrothermal synthesis exceptionally exhibited luminescence properties. In addition, surface modification for specific binding to a target molecule substantially augmented their PL characteristics. Among the different nitrogen and sulfur (N and S) doping agents used, including urea (U), sulfate (S), p-phenylenediamine (P), and sodium thiosulfate (TS), the results showed that PTS-CDs from the co-doping of p-phenylenediamine and sodium thiosulfate exhibited the highest PL properties. From this study on the fluorimetric sensing of several metal ions, PTS-CDs could effectively detect Fe3+ with the highest selectivity by fluorescence quenching to 79.1% at a limit of detection (LOD) of 0.1 µmol L-1. The PL quenching of PTS-CDs was linearly correlated with the wide range of Fe3+ concentration, ranging from 5 to 400 µmol L-1 (R2 = 0.9933).

Lignin-Derived Syringol and Acetosyringone from Palm Bunch Using Heterogeneous Oxidative Depolymerization over Mixed Metal Oxide Catalysts under Microwave Heating.

Biomass valorization to building block chemicals in food and pharmaceutical industries has tremendously gained attention. To produce monophenolic compounds from palm empty fruit bunch (EFB), EFB was subjected to alkaline hydrothermal extraction using NaOH or K2CO3 as a promotor. Subsequently, EFB-derived lignin was subjected to an oxidative depolymerization using Cu(II) and Fe(III) mixed metal oxides catalyst supported on γ-Al2O3 or SiO2 as the catalyst in the presence of hydrogen peroxide. The highest percentage of total phenolic compounds of 63.87 wt% was obtained from microwave-induced oxidative degradation of K2CO3 extracted lignin catalyzed by Cu-Fe/SiO2 catalyst. Main products from the aforementioned condition included 27.29 wt% of 2,4-di-tert-butylphenol, 19.21 wt% of syringol, 9.36 wt% of acetosyringone, 3.69 wt% of acetovanillone, 2.16 wt% of syringaldehyde, and 2.16 wt% of vanillin. Although the total phenolic compound from Cu-Fe/Al2O3 catalyst was lower (49.52 wt%) compared with that from Cu-Fe/SiO2 catalyst (63.87 wt%), Cu-Fe/Al2O3 catalyst provided the greater selectivity of main two value-added products, syringol and acetosyrigone, at 54.64% and 23.65%, respectively (78.29% total selectivity of two products) from the NaOH extracted lignin. The findings suggested a promising method for syringol and acetosyringone production from the oxidative heterogeneous lignin depolymerization under low power intensity microwave heating within a short reaction time of 30 min.