Subramanian Singaravadivel

Phenothiazine based sensor for naked-eye detection and bioimaging of Hg(II) and F− ions

The design and development of new phenothiazine-based fluorescent probes, which display a selective fluorescence response to mercury and fluoride ions, were described. The probe is the first example that facilitates the detection of Hg2+ at nanomolar concentrations. The sensitivity of probe P-1 to Hg2+ and F− was demonstrated in living cells, and cell toxicity assays revealed that probe P-1 can be used for selective imaging of Hg2+ and F− in living cells. Moreover, the simple probe design presented here may contribute to the development of more efficient and more useful dual-mode probes.

A rhodamine based “turn-on” fluorescent probe for Pb(II) and live cell imaging

A novel “turn-on” fluorescent chemosensor RDP-1 based on a rhodamine tri methoxy benzaldehyde conjugate was synthesized, which showed high selectivity and sensitivity towards recognition of Pb2+ in aqueous media over other metal ions and also color changes from colorless to pink, allowing colorimetric detection of Pb2+ by the naked eye. The sensitivity of probe RDP-1 towards Pb2+ was demonstrated in living cells, and can be used for selective imaging of Pb2+ in living cells.

Fluorescence “on–off–on” chemosensor for selective detection of Hg2+ and S2−: application to bioimaging in living cells

A phenothiazine based diamino-malenonitrile-linked chromogenic and fluorogenic probe (P-1) was synthesized and characterized for the specific detection of Hg2+ and S2−. In the presence of Hg2+, the probe produces “switch-off” along with a color change from yellow to brown, allowing colorimetric detection of Hg2+ by the naked eye. The sensitivity of probe P-1 towards Hg2+ and S2− was demonstrated in living cells, and cell toxicity assay also reveals that the probe P-1 can be used for selective imaging of Hg2+ and S2− in living cells.

A selective, long-lived deep-red emissive ruthenium(II) polypyridine complexes for the detection of BSA

A selective, label free luminescence sensor for bovine serum albumin (BSA) is investigated using ruthenium(II) complexes over the other proteins. Interaction between BSA and ruthenium(II) complexes has been studied using absorption, emission, excited state lifetime and circular dichroism (CD) spectral techniques. The luminescence intensity of ruthenium(II) complexes (I and II), has enhanced at 602 and 613 nm with a large hypsochromic shift of 18 and 5 nm respectively upon addition of BSA. The mode of binding of ruthenium(II) complexes with BSA has analyzed using computational docking studies.

Sensitized Near-Infrared Luminescence From NdIII, YbIII and ErIII Complexes by Energy-Transfer From Ruthenium 1,3-Bis([1,10]Phenanthroline-[5,6-d]-Imidazol-2 -yl)Benzene

The luminescent ruthenium 1,3 -bis([1,10]phenanthroline-[5,6 -d]- imidazol-2 -yl)benzene (bpibH2) complex, a potentially useful bridging ligand with a vacant diimine site, has been used as ‘metallo ligand’ to make heterodinuclear d–f complexes by attachment of a {Ln(dik)3} fragment (dik = 1,3-diketonate) at the vacant site. When Ln = Nd, Yb, or Er the lanthanide centre has low-energy f–f excited states capable of accepting energy from the 3MLCT excited state of the Ru(II) centre, there is quenching in the 3MLCT luminescence of the Ru(II) centre, that affords sensitized lanthanide(III) based luminescence in the near-IR region. Nd(III) was found to be the most effective at quenching the 3MLCT luminescence of the ruthenium component because of the high density of f–f excited states of the appropriate energy which make it as effective energy-acceptor compared to Er and Yb complexes.

Rhodamine–benzothiazole conjugate as an efficient multimodal sensor for Hg2+ ions and its application to imaging in living cells

A rhodamine B dye bearing a benzothiazole (RBT-1) conjugate is designed and synthesized, it shows a highly selective and sensitive naked-eye color change and turn-on fluorescence response to Hg2+ ions. The detection limit of RBT-1 towards Hg2+ is found to be 0.17 nM. RBT-1 exhibits low cytotoxicity and cell membrane permeability, which makes it capable of sensing Hg2+ in HeLa cells and real water samples.

Pineapple Peel-Derived Carbon Dots: Applications as Sensor, Molecular Keypad Lock, and Memory Device

Herein, the fluorescent carbon dots (CDs) with blue emission were prepared by hydrothermal treatment using pineapple peel as a source of carbon. The as-prepared CDs exhibited turn-Off fluorescence behavior toward Hg2+ and subsequent turn-On behavior for l-cysteine along with enhanced biocompatibility and negligible cytotoxicity for cell imaging. The practical applicability of carbon dots was used for the quantification of Hg2+ in water. On the basis of the spectral characteristic changes, we have designed individual elementary logic operations such as NOT and IMP gates, by utilizing CD as probe and Hg2+ and l-Cys as chemical inputs. We have also demonstrated the utility of this system in electronic security devices and as memory element, with the idea of the switching.