Department of Chemistry

Indian Institute of Technology Palakkad&nbsp;(IIT Palakkad or IIT PKD) is a public autonomous&nbsp;engineering&nbsp;and&nbsp;research&nbsp;institute located in&nbsp;Palakkad,&nbsp;Kerala. It was&nbsp;one of the five new&nbsp;IITs&nbsp;proposed in the&nbsp;2014 Union budget of India. The campus was inaugurated on 3 August 2015. The institute has 94 faculty, 978 students, and 63 non-teaching staffs.

IT Palakkad currently offers four-year Bachelor of Technology (B.Tech) and two years MS programmes in 8 different engineering disciplines including&nbsp;Computer Science, Electrical, Mechanical, Civil among others.

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IIT Palakkad

A tremendous growth in the field of carbon nanomaterials has led to the emergence of carbon nanotubes, fullerenes, mesoporous carbon and more recently graphene. Some of these materials have found applications in electronics, sensors, catalysis, drug delivery, composites, and so forth. The high temperatures and hydrocarbon precursors involved in their synthesis usually yield highly inert graphitic surfaces. As some of the applications require functionalization of their inert graphitic surface with groups like -COOH, -OH, and -NH2, treatment of these materials in oxidizing agents and concentrated acids become inevitable. More recent works have involved using precursors like carbohydrates to produce carbon nanostructures rich in functional groups in a single-step under hydrothermal conditions. These carbon nanostructures have already found many applications in composites, drug delivery, materials synthesis, and Li ion batteries. The review aims to highlight some of the recent developments in the application of carbohydrate derived carbon nanostructures and also provide an outlook of their future prospects. © 2010 Wiley-VCH Verlag GmbH&amp;Co. KGaA, Weinheim.

World University root node

Chemistry - An Asian Journal

Functionalized carbon nanomaterials derived from carbohydrates

The mobility of the organic dye DCM (4-dicyanomethylene-2-methyl-6-p- dimethyl aminostyryl-4H-pyran) in the gel and fluid phases of a lipid vesicle is studied by fluorescence correlation spectroscopy (FCS). Using FCS, translational diffusion of DCM is determined in the gel phase and fluid phase of a single lipid vesicle adhered to a glass surface. The size of a lipid vesicle (average diameter ∼100 nm) is smaller than the diffraction limited spot size (∼250 nm) of the microscope. Thus, the vesicle is confined within the laser focus. Three lipid vesicles (1,2-dilauroyl-sn-glycero-3-phosphocholine (DLPC), 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC), and 1,2-dipalmitoyl-sn- glycero-3-phosphocholine (DPPC)) having different gel transition temperatures (-1, 23, and 41 °C, respectively) were studied. The diffusion coefficient of the dye DCM in bulk water is ∼300 μm2/s. In the lipid vesicle, the average Dt decreases markedly to ∼5 μm 2/s (∼60 times) in the gel phase (for DPPC at 20 °C) and 40 μm2/s (∼8 times) in the fluid phase (for DLPC at 20 °C). This clearly demonstrates higher mobility in the fluid phase compared with the gel phase of a lipid. It is observed that the Dt values vary from lipid to lipid and there is a distribution of Dt values. The diffusion of the hydrophobic dye DCM (Dt ∼ 5 μm2/s) in the DPPC vesicle is found to be 8 times smaller than that of a hydrophilic anioinic dye C343 (Dt ∼ 40 μm2/s). This is attributed to different locations of the hydrophobic (DCM) and hydrophilic (C343) dyes. © 2010 American Chemical Society.

Journal of Physical Chemistry B

A fluorescence correlation spectroscopy study of the diffusion of an organic dye in the gel phase and fluid phase of a single lipid vesicle

Effect of a room temperature ionic liquid (RTIL) and water on the ultrafast excited state proton transfer (ESPT) of pyranine (8-hydroxypyrene-1,3,6- trisulfonate, HPTS) inside a microemulsion is studied by femtosecond up-conversion. The microemulsion consists of the surfactant, triton X-100 (TX-100) in benzene (bz) and contains the RTIL, 1-pentyl-3-methyl-imidazolium tetrafluoroborate ([pmim] [BF4]) as the polar phase. In the absence of water, HPTS undergoes ultrafast ESPT inside the RTIL microemulsion (RTIL/TX-100/bz) and the deprotonated form (RO-) exhibits three rise components of 0.3, 14, and 375 ps. It is proposed that in the RTIL microemulsion, HPTS binds to the TX-100 at the interface region and participates in ultrafast ESPT to the oxygen atoms of TX-100. On addition of water an additional slow rise of 2150 ps is observed. Similar long rise component is also observed in water/TX-100/benzene reverse micelle (in the absence of [pmim] [BF4]). It is suggested that the added water molecules preferentially concentrate (trapped) around the palisade layer of the RTIL microemulsion. The trapped water molecules remain far from the HPTS both in the presence and absence of ionic liquid and gives rise to the slow component (2150 ps) of ESPT. Replacement of H2 O by D2 O causes an increase in the time constant of the ultraslow rise to 2350 ps. © 2010 American Institute of Physics.

Fulltext

Journal of Chemical Physics

Ultrafast and ultraslow proton transfer of pyranine in an ionic liquid microemulsion

We show that data from recent experiments carried out on the kinetics of DNA escape from α -hemolysin nanopores [M. Wiggin, C. Tropini, C. T. Cossa, N. N. Jetha, and A. Marziali, Biophys. J. 95, 5317 (2008)] may be rationalized by a model of chain dynamics based on the anomalous diffusion of a particle moving in a harmonic well in the presence of a delta function sink. The experiments of Wiggin found, among other things, that the occasional occurrence of unusually long escape times in the distribution of chain trapping events led to nonexponential decays in the survival probability, S(t), of the DNA molecules within the nanopore. Wiggin ascribed this nonexponentiality to the existence of a distribution of trapping potentials, which they suggested was the result of stochastic interactions between the bases of the DNA and the amino acids located on the surface of the nanopore. Based on this idea, they showed that the experimentally determined S(t) could be well fit in both the short and long time regimes by a function of the form (1+t/τ)-α (the so called Becquerel function). In our model, S(t) is found to be given by a Mittag-Leffler function at short times and by a generalized Mittag-Leffler function at long times. By suitable choice of certain parameter values, these functions are found to fit the experimental S(t) even better than the Becquerel function. Anomalous diffusion of DNA within the trap prior to escape over a barrier of fixed height may therefore provide a second, plausible explanation of the data, and may offer fresh perspectives on similar trapping and escape problems. © 2010 American Institute of Physics.

Anomalous reaction-diffusion as a model of nonexponential DNA escape kinetics

Coordination-driven self-assembly of 1,3,5-benzenetricarboxylate (tma; 1) and oxalato-bridged p-cymeneruthenium(II) building block [Ru2(μ- η4-C2O4)(MeOH)2(η 6-p-cymene)2](O3SCF3)2(2) affords an unusual octanuclear incomplete prism [Ru8(η 6-p-cymene)8(tma)2(μ-η4- C2O4)2(OMe)4](O3SCF 3)2(3), which exhibits a remarkable shape-selective binding affinity for neutral phenolic compounds via hydrogen-bonding interactions (p-cymene = p-iPrC6H4Me). Such a binding was confirmed by single-crystal X-ray diffraction analysis using 1,3,5-trihydroxybenzene as an analyte. © 2010 American Chemical Society.

Inorganic Chemistry

Ruthenium-oxygen coordination-driven self-assembly of a Ru II8incomplete Prism: Synthesis, structure, and shape-selective molecular recognition study

Stimuli-responsive organic-inorganic hybrid spheres were synthesized by coating the colloidal polystyrene spheres with polyelectrolyte-protected aminoclay, Mg phyllo(organo)silicate layers in a layer-by-layer method. The clay layers are sandwiched between the polyelectrolyte layers. The aminoclay swells in water due to protonation of amino groups, and the degree of swelling depends on the pH of the medium. As a result, the hybrid spheres undergo a size change up to 60% as the pH is changed from 9 to 4. The stimuli-responsive property of the hybrid spheres was used for the release of ibuprofen and eosin at different pH. © 2010 American Chemical Society.

ACS Nano

PH-sensitive breathing of clay within the polyelectrolyte matrix

Propyloxy-substituted piperidine in solution adopts a conformation in which its alkoxy group is equatorially positioned. Surprisingly, two conformers of it that do not interconvert in the NMR time scale at room temperature have been found within an octa-acid capsule. The serendipitous finding of the axial conformer of propyloxy-substituted piperidine within a supramolecular capsule highlights the value of confined spaces in physical organic chemistry. © 2010 American Chemical Society.

Organic Letters

Chemistry in confined spaces: High-energy conformer of a piperidine derivative is favored within a water-soluble capsuleplex

The use of supramolecular architectures to control the spatially dependent spin exchange (spin communication) between two covalently linked radical centers (biradical) has been explored. Cucurbit[8]uril, through supramolecular steric effect, completely suppresses spin exchange between two adjacent radical centers in a biradical. © The Royal Society of Chemistry.

Chemical Communications

Suppression of spin-spin coupling in nitroxyl biradicals by supramolecular host-guest interactions

Fluorescence correlation spectroscopy (FCS) has been used to study the motion of fluorescent dyes in a giant (diameter 20 000 nm = 20 μm) catanionic vesicle comprised of the surfactant sodium dodecyl sulfate (SDS) and dodecyltrimethyl ammonium bromide (DTAB). The diffusion in the anion (SDS) rich catanionic vesicle was studied both in bulk water and in an immobilized vesicle attached to a positively charged glass surface. In the case of the immobilized vesicle, the diffusion coefficients (Dt) of R6G (rhodamine 6G), DCM (4-dicyanomethylene-2-methyl-6-p-dimethyl aminostyryl-4H-pyran), and C343 (coumarin 343) are found to be 1.5, 2.5, and 10 μm2/s, respectively, which are 280, 120, and 55 times slower compared to those for the same dyes in bulk water. The magnitude of Dt is found to vary for different vesicles. This was attributed to the difference in size and shape of the immobilized vesicles. In bulk, R6G binds completely to the vesicle and exhibits extremely slow diffusion with Dt = 0.5 ± 0.1 μm2/s (∼850 and 3 times slower compared to that of R6G in bulk water and within the immobilized vesicle). This is attributed to very slow overall diffusion of the very large size vesicles (20 μm = 20 000 nm). Both of the dye molecules (DCM and C343) show two different diffusion coefficients for the vesicles in bulk. In this case, the small Dt (0.5 ± 0.1 μm2/s) corresponds to the diffusion of the vesicle as a whole and the large Dt value (300 and 550 μm2/s for DCM and C343, respectively) corresponds to the free dye molecules in bulk water. © 2010 American Chemical Society.

Diffusion of organic dyes in immobilized and free catanionic vesicles

Supramolecular complexation behavior of cucurbiturils with paramagnetic nitroxide spin probes was examined by 1H NMR, X-ray diffraction studies of crystals, computation, and EPR. Both cucurbit[7]uril (CB7) and cucurbit[8]uril (CB8) form a 1:1 complex with 4-(N,N,N-trimethylammonium)-2,2,6, 6-tetramethylpiperidinyl-N-oxy bromide (CAT1). The structure of the complex in the solid state was inferred by X-ray diffraction studies and in the gas phase by computation (B3LYP/6-31G(d)). Whereas ESI-MS data provided evidence for the existence of the complex in solution, indirect evidence was obtained through 1H NMR studies with a structural diamagnetic analogue, 4-(N,N,N-trimethylammonium)2,2,6,6-tetramethyl-N-methylpiperidine iodide (DCAT1). The EPR spectrum of the CAT1 @CB7 complex consisting of three lines suggested that probe CAT1 is associated with host CB7 such that the nitroxide part is exposed to water. The spectral pattern was independent of the concentration of the complex and the presence of salt such as NaCl. The most interesting observation was made with CB8 as the host. In this case, in addition to the expected three-line spectrum, an additional spectrum consisting of seven lines was recorded. The contribution of the seven-line spectrum to the total spectrum was dependent on the concentration of the complex and added salt (NaCl) to the aqueous solution. The coupling constant for the seven-line spectrum for 14N-substituted CAT1 is 5 G, and that for the four-line spectrum for 15Nsubstituted CAT1 is 7.15 G. The only manner by which we could reproduce the observed spectra by simulation for both 14N- and 15N-substituted CAT1@CB8 was by assuming a spin exchange among three nitroxide radicals. To account for this observation, we hypothesize that three CAT1 molecules included within CB8 interact in such a way that there is an association of three supramolecules of CATl@CB8 (i.e., [CAT1@CB8]3) in a triangular geometry that leads to spin exchange between the three radical centers. We have established, with the help of 13 additional examples, that this is a general phenomenon. We are in the process of understanding this unusual phenomenon. © 2009 American Chemical Society.