A novel dendritic polymer based turn- off fluorescence sensor for the selective detection of cyanide ion in aqueous medium

The Application of Modified SBA-15 as a Chemosensor

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The Santa Barbara Amorphous (SBA-15), with a large surface area covered with abundant Si-OH active groups on the walls of its pores, can be modified with various organic compounds to build organic-inorganic hybrid materials, which can be used as a catalyst in organic reactions, drug delivery systems, nano sorbent due to its high capacity for removing heavy metals in waste water and as chemosensors for ions. Tunable and straight channels of SBA-15 facilitate the entrance and diffusion of ions through the channels. This paper presents a review of the past five years of literature covering the application of SBA-15 as an ions chemosensor in the liquid and gaseous media.

An ultra-low detection limit gold(III) probe based on rhodamine-covalent hydrogel sensor

A highly sensitive and selective optical chemosensor (Arg-Rhoen) for determination of Au³⁺ was prepared by covalent immobilization of rhodamine ethylenediamine on agarose gel. Spectrophotometric studies of complex formation, chemical structures and purity of the hydrogel sensor were carried out using TGA, NMR, TEM, and IR. The complexation study results indicated that this probe can selectively detect Au³⁺ via a metal ion chelation-induced ring-opening reaction, and then caused a remarkable colour change from colourless to pink and a strong fluorescence enhancement. Theoretical DFT calculation results suggested that the hydrogel sensor Arg-Rhoen formed stable complexes with Au³⁺ through a large number of cation-dipole interactions. Reusability has been established by repeatedly dipping and rinsing the hydrogel in aqueous Au³⁺ and EDTA in basic solutions. We believe that this approach may provide an easily measurable and inherently sensitive method for Au³⁺ detection in environmental and biological applications.

Pyrene-Hydrazone-π···Hole Coupled Turn-on Fluorescent and Naked- Eye Colorimetric Sensor for Cyanide: Role of Homogeneous π-Hole Dispersion in Anion Selectivity

A pyrene based probe associated with π···hole - hydrazone as one of the recognizing elements is synthesized and its turn in to a selective colorimetric and turn-on fluorescent sensor, (L³) for cyanide anion. This chemo sensor show high selectivity towards cyanide anion through photo electron transfer (PET) mechanism. The binding strength and sensitivity of the chemo sensor L³ towards cyanide are found to be 2.0 X 10⁴, and 4.44 x 10^-4 respectively. We have compared this high selectivity of the receptor towards cyanide, with our previously reported receptors L¹ and L². The detailed UV-Vis, Emission, ¹H-NMR, IR spectroscopic and Molecular Electrostatic Potential (MEP) studies reveals that the homogeneous π···hole dispersion in the aromatic ring governing the selectivity of the receptor towards cyanide anion. Such a positive π···hole homogeneous dispersion is missing in the case of sensor L², instead we have polarized π···hole dispersion towards 2^nd and 4^th position of di-nitrophenyl chromophoric unit in L².

Azide functionalized porphyrin based dendritic polymers for in vivo monitoring of Hg2+ ions in living cells

A porphyrin cored azide functionalised dendritic polymer was developed as a selective sensor for in vivo monitoring of mercuric ions in living (normal and cancer) cells and in an aqueous medium. The developed sensor could sense mercuric ions even at a nanomolar concentration with a limit of detection value of 0.9 nM. This probe can be used to monitor mercuric ions in living cells due to its low cytotoxicity and high cell permeability. The hydrophilic nature of the polymer makes it a promising candidate for sensing mercuric ions in real water samples. Moreover, the reversibility of this sensing strategy helps in constructing a logic gate, which is particularly useful in smart sensor design.

A molecular phototropic system for cyanide: Detection and sunlight driven harvesting of cyanide with molecular sunflower

We are reporting a simple, easy to prepare, and conformation switchable first molecular phototropic system L, "(E)-2-(2,4-dinitrophenyl)-1-((pyren-8-yl)methylene)hydrazine, for cyanide harvesting. This molecular phototropic system behaves as a molecular sunflower in which the conformation of this molecular sunflower can be altered in response to the sunlight. This molecular flower can sense and bind the cyanide anion colorimetrically through its transition state. Further, upon exposure of this transition state cyanide complex 1, under sunlight, this system is capable to release the bound cyanide via -C=N- free rotation to reach its lower energy stable conformation. Similar behaviors were observed for acetate and fluoride with L. The strength of the phototropic system L towards cyanide, acetate and fluoride is found to be 4.5 × 10⁵, 1.53 × 10² and 6.09 × 10² M^-1.

Water Soluble Porphyrin for the Fluorescent Determination of Cadmium Ions

Porphyrins are highly conjugated molecules that perform wide variety of functions in biological systems. They absorb strongly in the visible region and they are excellent fluorophores that emit in the visible region. If the meso or β positions of porphyrins are properly substituted, emission in the NIR region is facilitated. The fluorescence property of porphyrins can be used in sensing applications. Here, we report the synthesis of a water soluble porphyrin that emits in the NIR region and this molecule is used in the fluorescent determination of cadmium ion, which is an environmental pollutant and affects the health of living organisms adversely. 5,10,15,20-tetrakis(4-hydroxy-3,5-dimethoxyphenyl)porphyrin (THMPP), which is water soluble was synthesised from 5,10,15,20-tetrakis(3,4,5-trimethoxyphenyl)porphyrin (TMPP) by partial demethylation, which in turn was synthesized by mixture acid method. The donor-acceptor interaction of THMPP-Cd²⁺ system displays a dynamic fluorescence quenching through the electron transfer (ET) mechanism. Developed method showed a linear response toward Cd²⁺ in the concentration range of 0.25 μM to 2 μM. The limit of detection was found to be 0.1499 μM. THMPP exhibited excellent selectivity towards Cd (II) in presence of other metal ions like Hg²⁺, Mn²⁺, Mg²⁺, Co²⁺ in 1:100, Zn²⁺, Cu²⁺, Ni²⁺ in 1:10 and Na⁺, K⁺ in 1:1 M ratio.

R. P, V. U, K. S. A polyamine dendritic polymer–copper complex: a reusable catalyst for the additive-free amination of aryl bromides, and iodides

Additive-free synthesis of aryl amines from aryl halides using a reusable water-soluble porphyrin-cored amine-functionalized dendritic polymer copper complex (PPECH–Amine–Cu) catalyst in aqueous media.