Sima Paul

Selective “naked eye” detection of Al(III) and PPi in aqueous media on a rhodamine–isatin hybrid moiety

A highly selective fluorescence probe, RIH (rhodamine–isatin hybrid) for Al3+ has been designed and synthesized. This new dual signal (colorimetric and fluorogenic “off–on” type) chemosensing ensemble based on the complex between RIH and Al3+ has also been effective to selectively discriminate PPi from other anions in aqueous solution at physiological pH.

Dual channel selective fluorescence detection of Al(III) and PPi in aqueous media with an ‘off–on–off’ switch which mimics molecular logic gates (INHIBIT and EXOR gates)

In this study, we have synthesized a simple Schiff base type isophthaloyl salicylaldehyde hydrazone (ISH) moiety which selectively detects Al(III) and PPi with a fluorescence enhancement at two different wavelengths in aqueous solution. The sensing phenomenon is also reversible and thus the sensor beautifully mimics logic gates (INHIBIT and EXOR gates).

FRET based ‘red-switch’ for Al3+ over ESIPT based ‘green-switch’ for Zn2+: dual channel detection with live-cell imaging on a dyad platform

Our designed chemosensor, rhodamine-HBT-dyad (RHD), selectively detects two biologically important ions (Al3+ and Zn2+) at two different wavelengths (‘naked-eye’ colors red and green, respectively) through two different mechanisms (i.e. FRET and ESIPT) at ppm level. The sensor can also detect the Al3+ ion through displacement of the Zn2+ ion in vivo.

A differentially selective chemosensor for a ratiometric response to Zn2+ and Al3+ in aqueous media with applications for molecular switches

A multifunctional fluorescent chemosensor (PMN) for Al3+ and Zn2+ has been developed, which displays a dual-mode and “off–on” fluorescence response upon addition of Al3+ or Zn2+ at two different wavelengths. This was possibly due to the inhibition of PET and CN isomerism, and the activation of chelation-enhanced fluorescence (CHEF). Moreover, PMN exhibited a preferential second mode of selectivity for Al3+ as it ratiometrically displaces Zn2+ from the [PMN + Zn2+] complex. Such fluorescence modulation behavior mimics the performance of an “OR” logic gate. It also shows an excellent performance in the “dipstick” method.

Rapid and ratiometric detection of hypochlorite with real application in tap water: molecules to low cost devices (TLC sticks)

We have designed a chemodosimeter DPNO (weak fluorescence) which can be oxidized to HPNO (strong blue fluorescence) by OCl(-) with high selectivity and sensitivity in a ratiometric approach with a noticeably lower detection limit. The sensor could be useful for the detection of hypochlorites in tap water.

A highly reactive (<1 min) ratiometric chemodosimeter for selective “naked eye” and fluorogenic detection of hydrazine

Hydrazine is an important industrial chemical but also very toxic. Thus rapid detection of hydrazine is very important. We have judiciously designed and constructed a novel ICT-based ratiometric “naked eye” and fluorescence smart probe, carbazole based malononitrile (CBM), that rapidly (<1 min) and selectively detects hydrazine in the presence of different metal ions, anions and other amines in aqueous medium. As a possible application of the probe, hydrazine sensing in tap water was tested. The probe also shows an excellent performance in the “dip stick” method.

Rapid ‘naked eye’ response of DCP, a nerve agent simulant: from molecules to low-cost devices for both liquid and vapour phase detection

A rhodamine-based new chemosensor, RHM, has been designed and synthesized. It reacts selectively with the organophosphate compound, DCP, a well-known nerve gas simulant (both in the liquid and vapour phase). Moreover, RHM offers the potential for detection by the naked eye for color and fluorescence change. The sensing phenomenon is supported by DFT calculation.

Fast and ratiometric “naked eye” detection of hydrazine for both solid and vapour phase sensing

A new ‘‘naked-eye’’ ratiometric colorimetric and fluorometric chemodosimeter (PBF) was constructed to enable trace vapor detection of hydrazine. This probe utilizes an irreversible and fast hydrazine-promoted cleavage of the ester linkage in PBF. This probe was shown to be highly selective for hydrazine, and showed real time response as well as a positive linear relationship to hydrazine concentration. The probe also shows an excellent performance in the ‘‘dip stick’’ method.

A remarkable ratiometric fluorescent chemodosimeter for very rapid detection of hydrogen sulfide in the vapour phase and living cells

A ratiometric fluorescent and colorimetric probe for hydrogen sulfide has been developed by combining benzothiazole and the cyanine moiety. Due to its fast response and a large Stokes shift, it was used for sensitive and selective detection of hydrogen sulfide. Moreover, this probe detects SH− both in solid and vapor phases. Its potential for biological applications was confirmed by employing it for fluorescence imaging of SH− in living cells.

Rapid and ratiometric sensor for CAN (Ce4+) through metal assisted oxidation reaction-altered through bond energy transfer (TBET): development of low cost devices (TLC plate sticks)

The metal catalyzed oxidation reaction in a simple rhodamine–carbazole dyad (a carbazole nucleus flanked by two rhodamine moieties) was carried out in the presence of CAN. This sensor displays a very fast response (<1 min) toward CAN at room temperature with a ‘naked-eye’ change. This TBET based sensor is also highly selective and sensitive towards CAN. The chemosensor showed excellent performance in the “dip-stick” method.