Syed S. Razi

An efficient multichannel probe to detect anions in different media and its real application in human blood plasma

A simple coumarin derived chromo and fluorogenic chemosensor has been synthesized and tested to detect anions in different medium. The designed chemosensor has shown a high colorimetric response for F− and AcO− ions in acetonitrile in which the color of solution changed from a yellow-green to red and orange respectively whereas, in aqueous medium the probe showed high fluorogenic response and selectively reacted with cyanide through a Michael type nucleophilic addition reaction in which a nonfluorescent (switched-off) color of the solution, “turn-on” to became fluorescent blue (switched-on). The multichannel mode of interaction between the probe and anions has been confirmed by absorption, emission, FT-IR, NMR, ESI-MS spectral data analysis. Moreover, the probe has shown high sensitivity to detect cyanide in a real sample, human blood plasma as well as on paper strips.

An azo based colorimetric probe for the detection of cysteine and lysine amino acids and its real application in human blood plasma

The present work describes the rational design and synthesis of a simple azo based colorimetric chemodosimeter to selectively detect Cys and Lys in the environment of competitive different class of amino acids in HEPES buffer under physiological conditions. The probes 3a and 3b containing aldehyde functionality upon interaction with Cys and Lys afforded stable thiazolidine and aldimine derivatives and displayed a sensitive ratiometric response in the absorption spectra due to a change in the intramolecular charge transfer (ICT) process. The whole recognition process for amino acids gives rise to a rapid significant colorimetric response with readily detectable naked-eye sensitive color changes in the real biological sample. The mechanism of interaction between the probes and amino acids has been confirmed by the optical behavior, FT-IR, NMR and ESI-MS data analysis.

A polynuclear hetero atom containing molecular organic scaffold to detect Al3+ ion through a fluorescence turn-on response

A simple polynuclear hetero atom (N and O) containing molecular organic scaffold/probe, 3 has been designed and synthesized and explored as a potential chemosensor to detect Al3+ (22 nM; ∼0.6 ppb) ion in a HEPES buffer. Upon interaction with different metal ions and anions the weak emission intensity (switched Off) of 3 (at 528 nm; λex = 376 nm) was enhanced significantly (switched On; ∼6.0 fold; Φ3+Al3+ = 0.07) only in the presence of Al3+ wherein, the color of the solution changed from a naked-eye sensitive fluorescent dark green to bright yellow-green. The observed chelation enhanced fluorescence (CHEF) is attributable to restricted ESIPT and CN isomerization processes due to complexation between the potential coordination sites (N and O atoms; hard base) of 3 and Al3+ (hard acid) in a 1 : 1 stoichiometry, consequently. The mechanism of the interaction has been confirmed by the change in optical behaviors, 1H/13C NMR, FTIR, and ESI-MS spectroscopy data analysis. Moreover, chemosensor 3 has also been utilized to detect Al3+ in real water samples and on test paper strips.

Smart excimer fluorescence probe for visual detection, cell imaging and extraction of Hg2+

Smart pyrene-based simple fluorescent probes 2 and 4 were designed, synthesized and characterized by different spectroscopic methods. The photophysical properties of the probes and their affinity towards different metal ions in phosphate buffer were investigated. Upon selective interaction with Hg2+, the molecular probes showed enhanced static excimer emission at 506 nm along with a naked-eye detectable chromo- and fluoro-genic response. Probe 2 sensitively showed a high limit of detection (3.4 pM) for Hg2+ in the solution. The pyrene silicate derivative, 4, was utilized to detect and extract Hg2+ in solution as well as in the solid state. The data obtained from NMR and ESI-MS spectroscopy supported the postulate that the mode of interaction of the probe with Hg2+ involves the N and O atoms of the –CN and –OH functional groups to complex Hg2+ in 2:1 stoichiometry. Moreover, probe 2 exhibited excellent selectivity for Hg2+ in protein medium (BSA/HSA) and was used to detect Hg2+ in live HeLa cells, on test paper strips and in real contaminated water samples.

Synthesis and application of a new class of D–π–A type charge transfer probe containing imidazole – naphthalene units for detection of F− and CO2

A new class of D–π–A type charge transfer probe, 3 and 4, containing imidazole – naphthalene moieties as donor and acceptor, respectively, has been synthesized via a Suzuki coupling reaction. Probe 3, upon interaction with different classes of anions, showed high selectivity toward fluoride with a detection sensitivity of 4 ppb (0.22 μM). The in situ generated imidazolyl ion (3 + F−) enables the detection of CO2 with the restoration of the original absorption and emission properties of 3. The mode of interaction has been confirmed by 1H NMR and DFT studies which suggested the deprotonation of the –NH fragment of the imidazolyl unit in the presence of F−.

Detection of Zn2+ ion on a reusable fluorescent mesoporous silica beads in aqueous medium

An efficient sensor system was designed and built by immobilizing a fluorescent bischromophoric dyad through a sol–gel reaction on mesoporous silica beads of high surface area. The silica supported dyad, SSD containing anthracene and naphthalimide moieties have shown high sensitivity and selectivity to detect Zn2+ among the tested cations in aqueous medium. The Job’s plot analysis showed a 1:1 stoichiometry for a complexation between SSD and Zn2+ in which the relative fluorescence intensity enhanced, ~6 times due to restricted photoinduced electron transfer reaction and color of the beads were changed from a fluorescent yellow green to blue. The reversible mode of complexation was tested in the presence of EDTA.Graphical abstract

Design and Synthesis of Some Imidazolyl Derivatives: Photophysical Studies and Application in the Detection of Anions

A fluorescent probe based on dicyanovinylphenanthroimidazole (DCPPI) has been designed and synthesized and its potential application to recognize F and CN ions via different channels has been tested in different medium. DCPPI shows intramolecular charge transfer process and exhibit ratiometric response toward F and CN ions. The change in physicochemical properties of DCPPI in the presence of cyanide can be attributed to the formation of Michael type adduct, DCPPIA whereas both F and CN ions have shown affinities to interact with NH fragment of imidazolyl unit under the condition. The possible mode of interaction has been confirmed by absorption, emission, NMR and ESI-MS spectral data analysis.