Sulfur- and nitrogen-doped carbon quantum dots (S,N-CQDs) were synthesized using feijoa leaves as a green precursor via a novel route. Spectroscopic and microscopic methods such as X-ray photoelectron spectroscopy, fluorescence spectroscopy, and high-resolution transmission electron microscopy were used to analyze the synthesized materials. The blue emissive S,N-CQDs were applied for qualitative and quantitative determination of levodopa (L-DOPA) in aqueous environmental and real samples. Human blood serum and urine were used as real samples with good recovery of 98.4-104.6 and 97.3-104.3%, respectively. A smartphone-based fluorimeter device was employed as a novel and user-friendly self-product device for pictorial determination of L-DOPA. Bacterial cellulose nanopaper (BC) was used as a substrate for S,N-CQDs to make an optical nanopaper-based sensor for L-DOPA determination. The S,N-CQDs demonstrated good selectivity and sensitivity. The interaction of L-DOPA with the functional groups of the S,N-CQDs via the photo-induced electron transfer (PET) mechanism quenched the fluorescence of S,N-CQDs. The PET process was studied using fluorescence lifetime decay, which confirmed the dynamic quenching of S,N-CQD fluorescence. The limit of detection (LOD) of S,N-CQDs in aqueous solution and the nanopaper-based sensor was 0.45 μM in the concentration range of 1-50 μM and 31.05 μM in the concentration range of 1-250 μM, respectively.

Multi-criteria decision making (MCDM) is necessary for choosing one from the available alternatives (or from the Pareto-optimal solutions obtained by multi-objective optimization), where the performance of each alternative is quantified against several criteria (or objectives). This paper presents a comprehensive review of the application of MCDM methods in chemical and process engineering. It systematically outlines the essential steps in MCDM including the various normalization, weighting, and MCDM methods that are critical to decision making. The review draws on published papers identified through a search in the Scopus database, focusing on works by authors with more contributions to the field and on highly cited papers. Each selected paper was analyzed based on the MCDM, normalization, and weighting methods used. Additionally, this paper introduces two readily available programs for performing MCDM calculations. In short, it provides insights into the MCDM steps and methods, highlights their applications in chemical and process engineering, and discusses the challenges and prospects in this area.