Abhishek Manna

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.

Nanomolar detection of hypochlorite by a rhodamine-based chiral hydrazide in absolute aqueous media: application in tap water analysis with live-cell imaging.

By employing the oxidation property of hypochlorite (OCl(-)), a novel rhodamine-based hydrazide of the chiral acid ((S)-(-)-2-pyrrolidone-5-carboxylic acid) (RHHP) was designed and synthesized for detection of OCl(-) absolutely in aqueous medium at nanomolar level. The structure of the chiral sensor was also proved by the X-ray crystallography. The bioactivity and the application of the probe for detection of OCl(-) in natural water system have been demonstrated. A plausible mechanism for oxidation of the sensor followed by hydrolysis is also proposed. The sensibility of the receptor toward OCl(-) was studied in absolute aqueous media, and the detection limit of hypochlorite-mediated oxidation to the receptor in nanomolar level makes this platform (RHHP) an ultrasensitive and unique system for OCl(-) oxidation.

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.

A naphthalimide–quinoline based probe for selective, fluorescence ratiometric sensing of trivalent ions

A new naphthalimide–quinoline based probe (NAQ) is designed and synthesized and its structure is confirmed through single crystal analysis. It detects the trivalent ions (Fe3+ or Al3+ or Cr3+) selectively among other alkali and transition metal ions studied. NAQ shows a distinct ratiometric fluorescence behavior upon addition of trivalent metal ions in CH3CN–HEPES buffer solution (40/60, v/v, pH = 7.4). This fluorogenic sensing of NAQ to M3+ (M3+ = Fe3+ or Al3+ or Cr3+) can be observed by the naked eye, when illuminated under the UV light.

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 selective and sensitive probe for colorimetric and fluorogenic detection of Cd2+ in aqueous media

A new rhodamine-quinoline based dyad has been synthesized. It shows a highly selective response to Cd(2+) in the presence of other competing metal ions in aqueous media (pH = 7.1). The detection limit of the sensor is in the 10(-7) M level.

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.

Cascade reaction-based rapid and ratiometric detection of H2S/S2− in the presence of bio-thiols with live cell imaging: demasking of ESIPT approach

For the rapid, ratiometric, fluorogenic and “naked eye” detection of H2S/S2−, a pro-excited state intramolecular proton transfer (ESIPT)-based receptor, 2-formyl-benzoic acid 2-benzothiazol-2-yl-phenyl ester (FBBP) has been designed. In the presence of H2S/S2− in preference to other common species, 2-(2-hydroxyphenyl)benzothiazole, a well known ESIPT-containing agent, is recovered from FBBP. Thus, H2S/S2− can be detected in vitro and in vivo by such a simple, easy-to-synthesise, practical ratiometric sensor.