Rik Rani Koner

Imine containing benzophenone scaffold as an efficient chemical device to detect selectively Al3

A benzophenone-based Schiff base 1 has been utilized as a fluorescence chemosensor for the selective detection of Al3+. The probe was synthesized in one step, and found to be non-fluorescent due to a combination of photoinduced electron transfer (PET), excited state intramolecular proton transfer (ESIPT) and E/Z isomerism. Upon addition of Al3+ to a methanolic solution of 1, the development of a strong fluorescence signal was observed with an attractive glowing green emission. This was due to the inhibition of PET, ESIPT and E/Z isomerism, and the activation of chelation enhanced fluorescence (CHEF). The quantum yield of 1–Al3+ was found to be 0.17. The selectivity was tested with 24 different metal and non-metal ions, and established using various spectroscopic tools. The strong affinity of compound 1 for Al3+ was also proven by 1H NMR and mass spectroscopy.

Engineering fused coumarin dyes: a molecular level understanding of aggregation quenching and tuning electroluminescence via alkyl chain substitution

Simple molecular structures capable of emitting over the entire visible range are still a challenge. Planar molecular structures have the drawback of fluorescence quenching in the solid state thus limiting their application fields. Combining long range excimer/exciplex emissions with a compound emission have been used to get white light. In this work, a series of new coumarin derivatives having a planar structure have been synthesized and characterized. The effects of systematic variation in alkyl chain functionalization providing morphological variations that permit interesting solid state emitting properties have been discussed simultaneously with electrochemical behavior and OLED (organic light emitting diode) device applications. Carbon chains containing 0–16 carbon atoms have been studied in order to conclude the results that systematic changes in alkyl group substitution can be utilized as a tool to tune the emitting color of these planar coumarins. Alkyl chains were introduced by O-acylation and O-benzoylation reaction on the hydroxyl group of parent coumarin 5. Thus the present strategy is also helpful in establishing a template to control the unproductive interchromophore electronic couplings. Solid state fluorescence properties support the crystal studies. Theoretical studies are also in agreement with experimental data. Electroluminescence of Device 2 with a turn on voltage (Von) around 5–6 V having s-CBP doped with 1% of 8 having alkyl substitution of 2-carbons is found to exhibit white emission with CIE co-ordinates of (0.29, 0.34) which is close to white emission while the alkyl substitution of 14-carbons (compound 17) in Device 7 (Von = 7 V) exhibited green emission. Thus a strategy helpful to tune the electroluminescence has been discussed.

Highly Directional 1D Supramolecular Assembly of New Diketopyrrolopyrrole-Based Gel for Organic Solar Cell Applications.

A new thermoreversible organogel based on diketopyrrolopyrrole dye (DPP-NCO) is reported for the first time and evolved as a new building block for the fabrication of 1D supramolecular assembly. AFM analysis illustrated that its gel state is composed of different sized 1D rods. DPP-NCO gel used as an additive in organic solar cells yields high efficiency of 7.9% owing to better nanophase separation of its active layer.

N-Substituted carbazole heterocycles and derivatives as multipurpose chemical species: at the interface of chemical engineering, polymer and materials science

Abstract Due to recent progress in synthetics, the ready obtainment of various N-substituted carbazole heterocycles opened a wide window of scientific and industrial opportunities in different R&D domains. As summarized in this review article, such attractive R&D domains concern (a) electrochemically grown functional polycarbazole films for (bio/chemo)sensing, covalent grafting of biomolecules, nanomaterial fabrication (polycarbazole-containing nanorings and dendrimers), and surface patterning/engineering (biochip fabrication), and (b) oxidatively grown materials containing a polycarbazole phase (template or non-templated liquid oxidation polymerizations). This last general approach led to numerous developments in the fabrication of various composite materials incorporating single/multiwalled carbon nanotubes, graphene oxide, and magnetic magnetite-based nanoparticles for the ultrasensitive detection of DNA hybridization for example. Some liquid-phase oxidative polymerizations of UV-sensitive carbazole-containing species also afforded corresponding polymeric UV-reactive microspheres for UV surface patterning and functionalization/structuration. All these novel polycarbazole-containing species generally possess interesting optical properties useful for sensing and photoelectronic/photovoltaic applications. In summary, the already proven rich organic chemistry and corresponding (electro/chemical) polymerization properties of such specific carbazole heterocycles are expected to generate even more wider output applications far beyond current knowledge in the field (combinatorial polymeric engineering, biocompatible medical devices/materials, for example).

Carboxylated ‘locking unit’ directed ratiometric probe design, synthesis and application in selective recognition of Fe3+/Cu2+

A ratiometric probe has been designed and synthesized through the introduction of a carboxylated functionality. The probe 1, synthesized in two steps, was found to be a fluorescent chemosensor for the selective ratiometric detection of Fe3+/Cu2+ over a wide range of metal ions quite efficiently. The carboxylated unit, ‘CH2COOH’, acts as a ‘locking unit’ restricting the possibility of E/Z isomerization and ESPT. This has been supported by theoretical studies. The selectivity was established using various spectroscopic techniques such as UV-vis and fluorescence spectroscopy. The probe was found to have fluorescence properties with a quantum yield of 0.18. The binding of this fluorescent receptor to metal ions was also proved by NMR and mass spectrometry. The present probe can efficiently detect the presence of very low concentrations of Fe3+/Cu2+ (0.51 and 4.46 μM of Cu2+ and Fe3+ respectively).

A Polycarboxyl-Decorated FeIII-Based Xerogel-Derived Multifunctional Composite (Fe3O4/Fe/C) as an Efficient Electrode Material towards Oxygen Reduction Reaction and Supercapacitor Application

Low cost, non-noble metal catalysts with a good oxygen reduction reaction (ORR) activity comparable to that of platinum and also having good energy storage properties are highly desirable but challenging. Several challenges are associated with the development of such materials. Herein, we demonstrate a new polycarboxyl-functionalised FeIII -based gel material, synthesised following a solvothermal method and the development of its composite (Fe3 O4 /Fe/C) by annealing at optimised temperature. The developed composite displayed excellent electrocatalytic activity for the oxygen reduction reaction with an onset potential of 0.87 V (vs. RHE) and a current density value of -5 mA cm-2 , which are comparable with commercial 20 wt % Pt/C. In addition, as one of the most desirable properties, the composite exhibits a better methanol tolerance and greater durability than Pt/C. The same material was explored as an energy storage material for supercapacitors, which showed a specific capacitance of 245 F g-1 at a current density of 1 A g-1 . It is expected that this Fe3 O4 /Fe/C composite with a disordered graphitised carbon matrix will pave a horizon for developing energy conversion and energy storage devices.

A dysprosium-based new coordination polymer and its activity towards the oxygen reduction reaction

A new dysprosium-based coordination polymer (Dy-CP) was synthesized by the solvothermal method and studied for ORR catalysis. The catalytically active Dy2O3 on graphitized carbon was synthesized from this particular Dy-CP via annealing. Generally, MOFs containing transition elements, such as Zn, Fe, and Co, have been studied for ORR, and they show very good activity as ORR catalysts. Although lanthanide-based perovskites have also been explored for ORR, lanthanide-based MOF/CPs have not been evaluated for the same. The promising activities of other transition metal-based oxides inspired us to study the ORR activity of the dysprosium-based CP. As a precursor molecule for porous nanocarbon synthesis, this Dy-based CP was graphitized under particular annealing conditions and its influence on the ORR activity was investigated.