Abstract
A NIR cyanine@imidazole derivative Cy1 was synthesized and evaluated as a metal ion sensor in solution. Cy1 was shown to be very sensitive to all metal ions tested, presenting a blue shift in the absorption from 668 nm to 633 nm, followed by a change in colour from pale green to blue with Zn2+, Cd2+, Co2+, Ni2+ and Hg2+ ions. Despite the blue shift in the absorption, a decrease at 633 nm (with a colour change from pale green to colourless), as well as a quenching in the emission intensity at 785 nm were observed for Cu2+ ions. The results show the formation of sandwich complexes of two ligands per metal ion with the highest association constant observed for Cu2+ (Log Kass.abs = 14.76 ± 0.09; Log Kass.emis. = 14.79 ± 0.06). The minimal detectable amounts were found to be 31 nM and 37 nM, with a naked eye detection of 2.9 ppm and 2.1 ppm for Hg2+ and Cu2+ ions, respectively. These results prompted us to explore the applicability of Cy1 by its combination with nanomaterials. Thus, Cy1@ doped MNs and Cy1@ doped PMMA nanoparticles were synthesized. Both nanosystems were shown to be very sensitive to Cu2+ ions in water, allowing a naked-eye detection of at least 1 ppm for Cy1@ doped MNs and 7 ppm for Cy1@ doped PMMA. This colourimetric response is an easy and inexpensive way to assess the presence of metals in aqueous media with no need for further instrumentation.
Highlights
The development of new methodologies for the detection of analytes in samples is an increasingly studied topic in the scientific community [1]
The synthesis of Cy1 was designed by following the indications reported by Bouteiller and co-workers [38]
Cy1 was obtained by post-synthetic derivatization of the commercially available dye Infrared spectra (IR)-813 p-toluenesulfonate through a SRN1 reaction of its meso-chlorine atom with 1-(3-Aminopropyl)imidazole and DIPEA in dichloromethane at room temperature
Summary
The development of new methodologies for the detection of analytes in samples is an increasingly studied topic in the scientific community [1]. These methods are important when detecting the presence of analytes in aqueous environments [2,3]. The maximum allowable concentration (MAC) is a regulated unit that defines the maximum concentration of a particular analyte, present in drinking water [6]. These values can be described by governments or by other organizations, such as the. The MAC for copper defined by the WHO is 2 ppm, a similar value to that described by the European Union; in the United
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