Abhijit Gogoi

NIR sensing of Zn(II) and subsequent dihydrogen phosphate detection by a benzothiazole functionalized ninhydrin based receptor

A benzothiazole functionalized ninhydrin based chemosensor (L1), exhibits selective naked eye detection of biologically important zinc ions (from light yellow to orange) accompanied by a ‘turn-on’ fluorescence emission response in the near infra-red (NIR) region. Most importantly, Zn2+ ion induced ‘turn-on’ fluorescence emission is also preserved in the presence of Cd2+ and most of the other competing metal ions which clearly suggests the high sensitivity of the chemosensor towards Zn2+. The Jobs plot suggests 1 : 1 binding of the L1 with the Zn2+ ion with a detection limit of 6 nM. Detailed 1H NMR titrations were also conducted to understand the binding behaviour of L1 towards the Zn2+ ion. The ‘L1–Zn2+ ensemble’ further shows a ratiometric response to H2PO4− among other competitive anions and nucleotides in the same experimental conditions.

Nanomolar Zn(II) sensing and subsequent PPi detection in physiological medium and live cells with a benzothiazole functionalized chemosensor

A new fluorescent chemosensor (L1) exhibits relay recognition of Zn2+ and pyrophosphate anion in a mixed buffer solution at a physiological pH. The probe exhibits excellent Zn2+ induced turn-on fluorescence, even as low as 1 nM (LOD = 71 ppb). Furthermore, addition of the pyrophosphate ion led to quenching of the fluorescence signal of the L1–Zn2+ ensemble. The sensitive fluorescence behavior of the L1 rendered a useful probe for in vitro assays of the intracellular Zn2+ and PPi ions in a model human cell line.

Electronic substitution effects on anion coordination of a tripodal thiourea receptor: evidences of deprotonation of oxy-anions in solid and solution

Two simple tris(2-aminoethyl)amine (tren)-based electron-donating p-methyl (L1) and p-methoxy (L2)-substituted tris-thioureas have been extensively studied with various anions. The X-ray diffraction studies reveal that in the case of both receptors L1 and L2, halide anions (F− , Cl− and Br− ) are encapsulated into the tripodal cavity of the receptors with 1:1 stoichiometry and anions such as and form dimeric capsular assemblies of the receptors with 1:2 stoichiometry. The solution-state binding and encapsulation of anions have also been confirmed by 1H NMR titration and 2D NOESY NMR experiments. The 1H NMR titration experiments show that receptor L1 is able to deprotonate , and in solution, which was further verified with the addition of tetrabutylammonium hydroxide. On the other hand, receptor L2 failed to deprotonate the hydrogenated oxy-anions in solution.

Nanofluidic transport through humic acid modified graphene oxide nanochannels

The chemical similarity of graphene oxide (GO) and humic acid has been exploited to fine-tune the ionic and molecular transport properties of a lamellar GO membrane. Introduction of humic acid (in 10, 15 and 20%) is found to improve the nanofluidic transport characteristics, such as ionic mobility, molecular selectivity, diffusivity and permeability, of the GO membrane. Remarkably, the membrane prepared with 15% humic acid displayed superior proton mobility (μH = 1.04 × 10−4 cm2 V−1 s−1), in-plane diffusivity (D = 4.8 × 10−6 cm2 s−1), and cross-plane permeability (PL = 2.03 × 10−4 mm g cm−2 s−1 bar−1) to the pure GO and other composite membranes. The favorable nanofluidic characteristics of the 15% membrane are attributed to the larger effective heights of the 2D nanochannels, derived from the onset point of the surface charge governed ionic conductivity of the membranes. The activation energy of proton transport (∼0.07 to 0.1 eV) confirmed the occurrence of a Grotthuss-like hopping mechanism in all the GO–HA membranes. Introduction of humic acid into two-dimensional GO channels also improved the solution stability and mechanical robustness of the pristine GO membrane. The lamellar GO–HA membranes were also found to be suitable for energy harvesting applications such as direct methanol fuel cells and reverse electrodialysis. Remarkably, even after 72 hours exposure to electrolyte solutions, open circuit potentials up to 0.05 V, 0.21 V, and 0.12 V were found for the 10, 15, and 20% membranes, respectively.

Competitive anion binding aptitude of benzimidazole and amide functionality of a non-symmetrical receptor in solid state and solution phase

Abstract A novel non-symmetric tripodal receptor (L) with benzimidazole and amide –NH functionalities has been synthesised and a comparative study for anion binding aptitude of those functionalities has been performed in solid state and solution phase. The protonated receptors in solid state tend to form a pseudo-cavity around the octahedral hexafluorosilicate anion whilst in second complex, binding of one sulphate and two bisulphates in unison by two protonated units arises. The benzimidazole –NHs are the strongest hydrogen bond donors in both the crystals controlling dominance over amide –NHs. The neutral receptor being selective towards fluoride anion induces a naked eye visible colorimetric change. The 1H NMR studies with the neutral and protonated form of the receptor suggest the strong involvement of amide –NH in anion binding in solution phase.

Effect of dietary supplementation of ascorbic acid on physiological parameters, body weight changes and reproductive performance of swamp buffaloes

To assess the effect of ascorbic acid supplementation on physiological parameters in buffalo viz., changes in body weight, dry matter intake and reproductive performances, eighteen Swamp buffaloes were divided into three groups. One group was fed with normal diet and other two groups supplemented with 10 and 15 g ascorbic acid animal−1 day−1. The group supplemented with 15 g ascorbic acid animal−1 day−1 had significantly lower respiration rate, pulse rate and rectal temperature as compared to the group supplemented with 10 or 0 g ascorbic acid animal−1 day−1. The dry matter intake kg−1 body weight, DMI per kg W0.75 was not affected by ascorbic acid supplementation. The body weight losses during winter were relatively less and the reproductive traits viz.., per cent of animals coming into oestrus, conception rate and number of services per conception improved at higher level of ascorbic acid supplementation. It may be concluded that dietary supplementation of ascorbic acid has favourable impact in maintaining the physiological parameters, body weight and improved reproductive traits of swamp buffaloes.