A new series of compounds has been developed for the recognition of metal ions and it was found that the position of substituent in the organic compound proved to be the deciding factor for the development of a chemosensor. Reprecipitation method was used to develop organic nanoparticles (ONPs) in aqueous medium and the suspension of ONP in aqueous medium remained stable for one month. These ONPs were studied for their recognition abilities using fluorescence spectroscopy and only ONPs of compound 1 resulted in a sensor for Sr(2+) and the sensor activities were found to be unaffected by the presence of any other cation. The sensor was successfully used to investigate the level of Sr(2+) in an oral gel, as well as toothpastes used to cure sensitive teeth.
Two new tripodal receptors (1–2) have been synthesized and characterized by various spectroscopic techniques. The nano-aggregates of 1 and 2 (N1 and N2) have been prepared by a re-precipitation method in aqueous medium and have shown different photo-physical properties. Nano-aggregates of 1 (N1) can selectively recognize Hg(2+) in aqueous medium in the presence of other metal ions with enhancement in fluorescent intensity. The response was linearly proportional to the concentration of Hg(2+) in the range 0–10 μM with a detection limit of 2.4 nM. The mechanism of selective binding of Hg(2+) by N1 has also been supported by theoretical studies. To the best of our knowledge, this work represents the first report on substituted thiourea based nano-aggregates for nano-molar detection of mercury in aqueous medium.
A series of novel heterotripodal receptors were synthesized with potential cation binding sites. Their crystal structure revealed the presence of extensive intramolecular as well as intermolecular hydrogen bonding, which allowed them to process into organic nanoparticles (ONPs) in aqueous medium. The ONPs thus synthesized showed extraordinary ability for chromogenic recognition of Cu 2+ ions, with the consequence that they could easily reduce Cu(II) into Cu(0) to produce copper nanocrystals (CuNCs) that grew on the surface of ONPs to generate hybrid nanomaterials, and were characterized by a number of studies. The hybrid NPs thus produced act as fluorescent probes for detection of Cr 3+ in aqueous phase, whereas neither of its constituents (i.e., ONPs or CuNCs) showed this recognition behavior.
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