Organic ligand interaction with copper(II) ions in both aqueous and non-aqueous media: Overcoming solubility issues for sensing

• Published in: Sensors and actuators. B, Chemical Vol. 365; p. 131934
• Main Authors: Jakku, Ranjithkumar, Privér, Steven H., Mirzadeh, Nedaossadat, Kandjani, Ahmad E., Sabri, Ylias, Kennedy, Stephen, Alenezy, Ebtsam K., Russo, Salvy, Lyskov, Igor, Wilson, Karen, Trivedi, Rajiv, Bhargava, Suresh K.
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 15-08-2022; Elsevier Science Ltd
• Subjects: Aggregation-caused quenching; Aqueous solutions; Copper; Drinking water; Environmental protection; Fluorescence; Imidazole; Mass spectrometry; NMR spectroscopy; Organic chemistry; Polystyrene resins; Raman spectroscopy; Sensor; SERS; Single crystals; Substrates; Water sampling; Fluorescence; Copper; SERS; Sensor; Aggregation-caused quenching
• ISSN: 0925-4005; 1873-3077
• DOI: 10.1016/j.snb.2022.131934

A new bis(thienyl)imidazole-based fluorescent organic molecular sensor (TIBIT) was prepared and fully characterized by NMR spectroscopy, mass spectrometry and single crystal X-ray diffraction. The sensing application of TIBIT towards metal ions in solution was investigated using UV–vis, fluorescence, and surface-enhanced Raman spectroscopy (SERS). In the organic solvent THF, TIBIT showed excellent sensitivity towards Cu(II) with a detection limit of 10 pM, whereas in aqueous media, aggregation-caused quenching (ACQ) was observed. Using a SERS substrate consisting of Au-deposited long-range ordered crystals (Au-LROCs) of polystyrene colloids and a uniform deposition of a TIBIT monolayer via bonding through the sulfur atoms of the thiophene rings, ACQ was overcome enabling the detection of trace amounts of Cu(II) in aqueous media. Using this novel approach, a detection limit of 13 nM was found, considerably lower than the recommended safe level of 20 µM regulated by the United States Environmental Protection Agency for Cu2+ in drinking water, thus demonstrating the potential of TIBIT for monitoring Cu(II) levels in water samples.
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•TIBIT is a reliable fluorescence and SERS-based sensitive and selective Cu2+ marker.•SERS nano-sensor overcomes aggregation-caused quenching in detecting Cu2+ ions.•Detection of ultra-low concentrations of Cu2+ ions in water is demonstrated.•LoD for fluorescence and SERS methods is 10 pM and 13 nM Cu2+, respectively.