ABSTRACT. In this work, synthesized carbon quantum dots (CQDs) and zinc oxide nanoparticles (ZnO NPs) are used to form ZnO/CQDs nanocomposite. The characterization of this nanocomposite using X-ray diffraction (XRD) indicates that ZnO NPs and ZnO/CQDs nanocomposite have the same profile, suggesting that the presence of CQDs does not impinge the crystal structure of ZnO in ZnO/CQDs nanocomposite. Besides, an analysis performed with scanning electron microscopy (SEM) displays plate-like nanostructure with an average thickness of about 22 nm and 25 nm for ZnO NPs and ZnO/CQDs, respectively. Furthermore, the reflectance study in the visible range shows a reduction of sunlight reflection intensity of ZnO/CQDs compared with the reflection intensity of ZnO NPs. In addition, the photocatalytic studies indicate that the rate of photocatalytic degradation of methylene blue (MB) of ZnO/CQDs nanocomposites is higher than that of ZnO NPs. Indeed, in optimized conditions, the photocatalytic activity can reach 100% within 45 min of sunlight exposure for the degradation of 7.5 mg/L MB using ZnO/CQDs while it takes 90 min using ZnO NPs under the same conditions. These fascinating results is attributed to the reduction of the reflective properties of ZnO/CQDs.   KEY WORDS: Fluorescent carbon quantum dots (CQDs), Photocatalytic degradation of methylene blue, Sunlight reflectance property, Synthesis of ZnO nanoparticles Bull. Chem. Soc. Ethiop. 2023, 37(2), 463-476.                                                               DOI: https://dx.doi.org/10.4314/bcse.v37i2.15

3-monochloropropane-1,2-diol (3-MCPD) is known as one of the neo-formed contaminants widely distributed in foodstuffs, especially in processed foods with high sides effects for human health. In this study, 3-monochloropropane-1,2-diol (3-MCPD) content for eleven (11) different types of foods from local market were evaluated in two ways using: (1) cysteine modified AgNPs (Cys-AgNPs) as functional nanomaterials for UV-Vis technique, and (2) gold-modified by Cys-AgNPs (Cys-AgNPs/Au) in electrochemistry sensor. High concentrations of 3-MCPD were found in most studied samples namely in liquid foods (palm oil and frying oil from tuna fish), fried foods (fried ripe banana, roasted peanut, banana chips, fried tuna and potato fries), smoked mackerel and roasted foods (pork barbecue). The maximum 3-MCPD content were 1085 μg/kg in liquid foods, 582 μg/kg in fried foods, 156 μg/kg in smoked and 716 μg/kg in roasted foods. As exhibited, the level of 3-MCPD in food products on the Ivorian market is relatively higher. This study indicates the importance of monitoring 3-MCPD content in food products for both domestic and industrial processing.