Synthesis of functionalized mesoporous silica nanoparticles for colorimetric and fluorescence sensing of selective metal (Fe3+) ions in aqueous solution.

The fabrication of red fluorescent hybrid mesoporous silica-based nanosensor materials has promised the bioimaging and selective detection of toxic pollutants in aqueous solutions. In this study, we present a hybrid mesoporous silica nanosensor in which the propidium iodide (PI) was used to conveniently integrate into the mesopore walls using bis(trimethoxysilylpropyl silane) precursors. Various characterization techniques including X-ray diffraction (XRD), Fourier-transform infrared (FTIR), N2 adsorption-desorption, zeta potential, particle size analysis, thermogravimetric, and UV-visible analysis were used to analyze the prepared materials. The prepared PI integrated mesoporous silica nanoparticles (PI-MSNs) selective metal ion sensing capabilities were tested with a variety of heavy metal ions (100 mM), including Ni2+, Cd2+, Co2+, Zn2+, Cr3+, Cu2+, Al3+, Mg2+, Hg2+ and Fe3+ ions. Among the investigated metal ions, the prepared PI-MSNs demonstrated selective monitoring of Fe3+ ions with a significant visible colorimetric pink color change into orange and quenching of pink fluorescence in an aqueous suspension. The selective sensing behavior of PI-MSNs might be due to the interaction of Fe3+ ions with the integrated PI functional fluorophore present in the mesopore walls. Therefore, we emphasize that the prepared PI-MSNs could be efficient for selective monitoring of Fe3+ ions in an aqueous solution and in the biological cellular microenvironment.

Smart phone assisted quinoline-hemicyanine based fluorescent probe for the selective detection of glutathione and the application in living cells.

Quinoline appended hemicyanine 6MIM with strong ICT character was successfully synthesized through simple condensation reaction of 6-methoxy-2-chloro-3-formyl quinoline with 2-benzothiazolinium iodide. The photophysical characteristics of synthesized probe revealed that it would selectively detect glutathione (GSH) when it compared with different amino acids including biothiols and the detection limit is found to be 100 nM. The turn off sensor is due to thiol-halogen SNAr nucleophilic substitution between 6MIM and thiol group in glutathione. More importantly, the biosensor 6MIM was effectively applied in the fluorescence bioimaging of GSH in living cells with low cell toxicity. The colorimetric detectable color change of 6MIM-GSH has been effectively integrated with smartphone assisted RGB color value application with lowest detection value of 120 nM.

Simple C3-symmetric triaminoguanidine-triphenylamine conjugate as an efficient colorimetric sensor for Cu(II) and fluorescent sensor for Fe(III) ions.

The design and construction of novel C3-symmetric triaminoguanidine-triphenylamine conjugate (L) has been demonstrated and it displays positive solvatochromic behaviour with an increase in solvent polarity. The probe L acts as a selective colorimetric sensor for Cu2+ ions over other metal ions. Further, it shows high selective and sensitive detection of Fe3+ ions through turn-on fluorescence response. Moreover, the detection limits for Cu2+ and Fe3+ ions were found to be within the allowable range of the World Health Organisation (30 µM). The real-time application of the probe was showed by paper strip experiments as well as detection of Fe3+ ions in pharmaceutical tablets.

Selective detection of pyrophosphate anion by zinc ensemble of C3-symmetric triaminoguanidine-pyrrole conjugate and its biosensing applications.

A new-fangled C3-symmetric triaminoguanidine-pyrrole conjugate has been constructed and utilized for sensing applications. The probe selectively detects zinc ions (Zn2+) by colorimetric as well as turn-on fluorescent manner. Further, the in-situ formed zinc ensemble displays turn-off fluorescence response towards the pyrophosphate anion (PPi) via displacement approach. Emissive off-on-off sensing characteristics of the probe has been successfully exploited to construct the INHIBIT logic gate, coding/decoding of messages and in vivo imaging of Zn2+/PPi in zebrafish larvae. Further, PPi detection characteristics of zinc ensembles were established for the sensing of PPi discharged from DNA synthesis and other biological reactions.

Coumarin based hydrazone as an ICT-based fluorescence chemosensor for the detection of Cu2+ ions and the application in HeLa cells.

We have constructed a new coumarin based fluorescence probe BENZPYR with ICT character through condensation of N, N-diethylamino-3-acetyl coumarin with 2-hydrazinobenzothiazole. The absorbance and fluorescence spectral characteristics of BENZPYR revealed that the chemosensor can specifically detect for Cu2+ ions over other different metal ions and the lowest limit of detection was found in nano molar range. The turn off sensor of BENZPYR is related to chelation enhanced quenching (CHEQ) and intramolecular charge transfer (ICT) processes were serve as excellent fluorescent detection of Cu2+ ions in DMF medium. Fluorescence microscopy experiments revealed that probe BENZPYR may have application as a fluorophore to detect the Cu2+ in living cells. The simulated DFT analysis of electronic and structural properties and also UV-vis absorption spectra are in well accordance with the experimental UV-vis absorption spectra.