Colorimetric and fluorimetric detection of Hg2+ and Cr3+ by boronic acid conjugated rhodamine derivatives: Mechanistic aspects and their bio-imaging application in bacterial cells.

Colorimetric and fluorimetric detection of toxic metal ions such as Hg2+ and Cr3+ has gained tremendous popularity over the conventional methods due to their operational simplicity, high selectivity, and speediness. Although numerous colorimetric and fluorescent receptors for Hg2+ or Cr3+ were reported in the literature, boronic acid-based receptors for these metal ions are rather scarce in the literature. Hence, in the present study dual function boronic acid conjugated rhodamine derivatives were developed, and their toxic metal ion detection abilities were studied by absorption, emission and visual detection methods. Absorption and emission spectral studies revealed that these derivatives displayed selectivity towards Hg2+, Cr3+ and Fe3+ among the other metal ions studied by forming new absorption band. Both the derivatives exhibited colorimetric response towards Hg2+ and Cr3+ by the change in color of the solution to pink and reddish pink with Fe3+. The detailed mechanism involved in the detection of Hg2+ was deduced by 1H NMR and ESI-MS studies. Further, these derivatives were used for fluorescence imaging of Hg2+ and Cr3+ in S. aureus bacterial cells. Thus the present manuscript demonstrated the use of boronic acid conjugated rhodamine derivatives as a dual function (colorimetric and fluorescent) probes and as imaging agents for Hg2+ and Cr3+, which are known for their toxic influence on bacterial cells.

Silver nanoparticles ensemble with Zn(II) complex of terpyridine as a highly sensitive colorimetric assay for the detection of Arginine.

Arginine play numerous roles in several biological processes, and also act as a precursor for many biomolecules. Arginine derived biomolecules were found to involve in many of the events that lead to diseases and therefore selective detection of Arg in biological fluids has an enormous impact on disease diagnosis and in the drug development. Although number of methods were developed for the selective detection of Arg, the colorimetric method has an advantage over these methods due to their operational simplicity, high selectivity, and speediness. Herein, silver nanoparticles ensemble with Zn(II) complex of α-liopoic acid conjugated terpyridine (ZnLATP-AgNPs) were developed for the selective colorimetric detection of Arg. The nanoparticle ensemble exhibited selectivity towards Arg by showing distinguishable colour change from yellow to orange, among all the other naturally occurring amino acids studied. The new ZnLATP-AgNPs assay allows detection of Arg down to 200±15nM, provides an easy and sensitive method to detect Arg visually. The current approach was further validated by the quantification of Arg in supplement tablets.