Brand new Dual Absorption and Emission Smartphone-Based Spectrophotometer (DAESS) for the study of the role of water in the preparation of Natural Deep Eutectic Solvents

Highlights: • Fully-functional smartphone-based dual absorption and emission spectrometer was built. • The device validation was carried out with conventional laboratory instrumental. • The instrument was fabricated using a 3D printer. • Versatile configuration of the device allows simple fit to any brand and mobile model. • Water role in NADES synthesis was evaluated by fluorescent and absorption spectra. Natural Deep Eutectic Solvents (NADES) are highly important for Green Chemistry principles and can be used instead of harmful organic solvents. Indeed, nowadays smartphone-based analytical devices can replace some traditional laboratory equipment. In the present work, a smartphone based dual spectrophotometer and spectrofluorometer device was designed, 3D manufactured, and validated. A resolution of 0.241 ± 0.010 pixel.nm⁻¹ and a stability comparable with commercial instruments were obtained. Using the proposed device it was possible, for the first time, to study the role of water in NADES (fructose:urea:water) preparation, by testing the influence of structural and dilution water. In this sense, it was observed that when water was added before NADES preparation (integrated into the superstructure of the solvent), fluorescence and absorbance intensities sharply decayed (up to 90% and 95%, respectively). In contrast, dilution water had minor effects on spectroscopic features of the eutectic system, which was expressed as 29% and 23% of diminution of signal intensities for both techniques. The obtained results suggest that the moment the water is added plays a significant role in NADES properties.