Paulpandian Muthu Mareeswaran

Spectral and electrochemical investigation of p-sulfonatocalix[4]arene-stabilized vitamin E aggregation

Abstract The host–guest interaction of α-tocopherol (vitamin E) with p-sulfonatocalix[4]arene (p-SC4) in solution state is studied using emission and cyclic voltammetric techniques. The lipid soluble α-tocopherol (α-T) forms a solid complex with p-SC4. FTIR and NMR spectral analysis of the solid complex reveals the tight packing of α-T inside the cavity of p-SC4. The structural deformation is confirmed by XRD analysis. SEM images differentiate the highly porous gel like structure of vitamin E aggregate and the solid structure of the host–guest complex prepared. NOESY spectra confirm the tight penetration of α-T within the hydrophobic cavity of p-SC4.

Spectral and electrochemical investigation of 1,8-diaminonaphthalene upon encapsulation of p-sulfonatocalix[4]arene

The 1,8-diaminonaphthalene has various optical applications and electropolymerisation characteristics. The interaction of 1,8-diaminonaphthalene with p-sulfonatocalix[4]arene is studied using absorption, emission, excited state lifetime, and electrochemical techniques. The binding constant values calculated from these techniques are around 102–105xa0M−1, which emphasizes the efficient binding of 1,8-diaminonaphthalene with p-sulfonatocalix[4]arene. The excited state lifetime is enhanced in the presence of p-sulfonatocalix[4]arene and the propensity of polymerization of 1,8-diaminonaphthalene under electrical environment is inhibited in the presence of p-sulfonatocalix[4]arene. The structure and the mode of binding between 1,8-diaminonaphthalene with p-sulfonatocalix[4]arene complex is studied using 1H NMR and rotating frame overhauser effect spectroscopy (ROESY) techniques.

Spectral, electrochemical and computational investigations on the host–guest interaction of Coumarin-460 with p-sulfonatocalix[4]arene

The supramolecular host–guest investigation of Coumarin 460 (C460), a salient coumarin family dye molecule is studied with a noteworthy host molecule, p-sulfonatocalix[4]arene (p-SC4). The investigation is carried out by both experimental and theoretical approach. The binding affinity of C460 with p-SC4 is experimentally studied using absorption, emission, excited state lifetime and Cyclic Voltammetry methods. The binding constant is around 103 M−u20091, which shows potent binding. The binding stoichiometry is 1:1. The binding orientations and binding energies are studied using computational simulations. The mode of binding is also established using NMR spectral techniques.

Spectral, Electrochemical and Computational Investigations of Binding of n-(4-Hydroxyphenyl)-imidazole with p-Sulfonatocalix[4]arene

The interaction of n-(4-hydroxyphenyl)-imidazole with p-sulfonatocalix[4]arene is studied using fluorescence technique. The quenching of fluorescence intensity explains the efficiency of binding via binding constant and quenching constant. The excited state lifetime of n-(4-hydroxyphenyl)-imidazole is decreased upon interaction with p-sulfonatocalix[4]arene. The cyclic voltametric studies emphasized the interaction of n-(4-hydroxyphenyl)-imidazole with p-sulfonatocalix[4]arene. Quantum chemical calculations are carried out to study the interactions as well as charge transfer between the host and the guest upon complexation. The simulations revealed that the n-(4-hydroxyphenyl)-imidazole interacts with p-sulfonatocalix[4]arene with horizontal orientation with in the p-sulfonatocalix[4]arene cavity.

Selective and sensitive fluorescent sensor for Pd 2+ using coumarin 460 for real-time and biological applications

The efficient fluorescent property of coumarin 460 (C460) is utilized to sense the Pd2+ selectively and sensitively. Fabrication of a sensor strip using commercial adhesive tape is achieved and the detection of Pd2+ is attempted using a handy UV torch. The naked eye detection in solution state using UV chamber is also attempted. The calculated high binding constant values support the strong stable complex formation of Pd2+ with C460. The detection limit up to 2.5u202f×u202f10-7u202fM is achieved using fluorescence spectrometer, which is considerably low from the WHOs recommendation. The response of coumarin 460 with various cations also studied. The quenching is further studied by the lifetime measurements. The binding mechanism is clearly explained by the 1H NMR titration. The sensing mechanism is established as ICT. C460 strips Pd2+ quenching detection is further confirmed by solid-state PL study. The in-vitro response of Pd2+ in a living cell is also studied using fluorescent imaging studies by means of HeLa cell lines and this probe is very compatible with biological environments. It could be applicable to sense trace amounts of a Pd2+ ion from various industries. Compared with previous reports, this one is very cheap, sensitive, selective and suitable for biological systems.

Investigation of the upper rim binding of triphenylpyrylium cation with p-sulfonatocalix[4]arene

The interaction of 2,4,6-triphenylpyrylium cation with p-sulfonatocalix[4]arene is studied using absorption, emission, NMR and electrochemical techniques. The increase in the absorption is observed with the increase in the concentration of p-sulfonatocalix[4]arene. The emission intensity of 2,4,6-triphenylpyrylium cation is also enhanced in the presence of p-sulfonatocalix[4]arene. The electrochemical titration reveals the presence of host–guest interaction. The NMR analysis explains the upper rim interaction of 2,4,6-triphenypyrylium cation with p-sulfonatocalix[4]arene. The mode of binding is studied using computational methods. The quantum chemical simulations reveal the binding orientation of cationic TPP with p-SC4. The calculated complexation energy (−u200933.19xa0kcalxa0mol−1) indicates the strong binding nature of 2,4,6-triphenylpyrylium cation with p-sulfonatocalix[4]arene.

FRET‐based Solid‐state Luminescent Glyphosate Sensor Using Calixarene‐grafted Ruthenium(II)bipyridine Doped Silica Nanoparticles

Calixarene-functionalized luminescent nanoparticles were successfully fabricated for the FRET-based selective and sensitive detection of the organophosphorus pesticide glyphosate (GP). p-Tert-butylcalix[4]arene was grafted on the surface of [Ru(bpy)3 ]2+ incorporated SiNps to produce self-assembled nanosensors (RSC). FRET was switched on in the presence of GP by means of energy transfer due to binding with p-tert-butylcalix[4]arene grafted on the surface of the RSC. The FRET efficiency of the GP-RSC system was increased gradually with the addition of GP. The FRET efficiency was evaluated as 87.69u2009% and a high binding affinity was established by the binding constant value, 1.16×107 u2005M-1 , using a Langmuir binding isotherm plot. The estimated limit of detection (LOD) was 7.91×10-7 u2005M, which was lower than the Environmental Protection Agency (EPA) recommendation. The probe also effectively responds to real sample analysis. The sensitivity and selectivity was realized due to the efficient FRET towards the fluorescence properties of the [Ru(bpy)3 ]2+ complex.