The synthesis produced two kinds of CNDs and, after extraction with toluene, the hydrophilic CNDs in the water-soluble fraction were characterized and further exploited. The fluorescent nanomaterial showed appreciable optical properties, quantum yield (9%), and a blue fluorescence emitted at 420 nm after excitation at 330 nm. Moreover, the CNDs also showed good photostability and their fluorescence intensity exhibited dependence on the pH. The CNDs proved to be a selective nanoprobe for the detection of 4-nitrophenol (4-NP), a man-made chemical widely used in the production of pharmaceuticals and pesticides, which has been listed as a priority pollutant due to the extent and severity of the environmental pollution it can cause. It has also been reported as a human urinary metabolite which can be used as a marker to evaluate pesticide exposure [2]. The instant assay of 4-NP was achieved by quenching the fluorescence of CNDs via an inner filter effect mechanism [3] accompanied by a marked wavelength shift while the fluorescence intensity decreased with increasing the concentration. The developed method was applied to a variety of matrices, such as tap water, treated wastewater, and human urine. The method showed a linear range from 0.8 to 53 uM with regression coefficient R\({}^{2}\) = 0.99, and acceptable sample recoveries (from 98 to 107%) in tap water and wastewater samples. ## References  
* _Cakmak et al. (2014)_ Cakmak, Y.S. ; Kaya, M.; Asan-Ozusaglam, M. Biochemical composition and bioactivity screening of various extracts from _Dunaliella salina_, a green microcalg. _EXCLI J._**2014**, _13_, 679-690. * Agency for Toxic Substances and Disease Registry (ATSDR) (2020) Agency for Toxic Substances and Disease Registry (ATSDR). _Toxicological Profile for Nitrophenols (Draft)_; Public Health Service, U.S. Department of Health and Human Services: Atlanta, GA, USA, 1990. * _Zu et al. (2017)_ Zu, F.; Yan, F.; Bai, Z.; Xu, J.; Wang, Y. The quenching of the fluorescence of carbon dots: A review on mechanisms and applications. _Microchin. Acta_**2017**, _184_, 1899-1914. * _3D Printed Voltammetric Sensor Modified with an Fe(III) Cluster for Nonenzymatic Determination of Glucose in Sweat_
* _Koukouviti_1, F. Vasileiou 1, A. K. Plessas 2, A. Economou 1, N. Thomaidis 1, G. S. Papaefstathiou 2 and C. Kokkinos 1,*
* Laboratory of Analytical Chemistry, Department of Chemistry, National and Kapodistrian University of Athens, 15771 Athens, Greece
* Laboratory of Inorganic Chemistry, Department of Chemistry, National and Kapodistrian University of Athens, 15771 Athens, Greece
* Correspondence: christok@chem.uoa.gr  
The skin is the largest human organ, offering excellent opportunities for noninvasive access, especially via perspiration. Among the different biomarkers measured in sweat, glucose is the most important. The core devices for its determination are the electrochemical enzymatic biosensors [1,2]. However, the use of an enzyme entails several drawbacks, as the activity of glucose oxidase is critically dependent on the immobilization procedure and on temperature, pH, ionic strength, and other factors [2]. Nonenzymatic glucose monitoring devices can be alternatively used, but this area remains largely unexplored, as very few works have been published in the pertinent literature [2, 3, 4]. Here, we present a 3D printed electrode modified with iron(III) basic benzoate, [Fe\({}_{3}\)O(PhCO\({}_{2}\))\({}_{6}\)(H\({}_{2}\)O)\({}_{3}\)].PhCO\({}_{2}\), for the nonenzymatic determination of glucose in sweat by stripping voltammetry. The electrode is 3D printed from a carbon black loaded polylactic acid filament and the trinuclear Fe(III) complex is drop-casted on the surface of the electrode, followed by its coverage with a Nafion film. The iron(III) basic benzoate was selected as a modifier due to its minimum water solubility, offering stable sensors to sweat conditions.