Subbiah Nagarajan

Bio: Subbiah Nagarajan is an academic researcher from National Institute of Technology, Warangal. The author has contributed to research in topics: Michael reaction & Chemistry. The author has an hindex of 18, co-authored 67 publications receiving 987 citations. Previous affiliations of Subbiah Nagarajan include University of Madras & Shanmugha Arts, Science, Technology & Research Academy.

Lithium storage mechanisms in purpurin based organic lithium ion battery electrodes

Abstract: Current lithium batteries operate on inorganic insertion compounds to power a diverse range of applications, but recently there is a surging demand to develop environmentally friendly green electrode materials. To develop sustainable and eco-friendly lithium ion batteries, we report reversible lithium ion storage properties of a naturally occurring and abundant organic compound purpurin, which is non-toxic and derived from the plant madder. The carbonyl/hydroxyl groups present in purpurin molecules act as redox centers and reacts electrochemically with Li-ions during the charge/discharge process. The mechanism of lithiation of purpurin is fully elucidated using NMR, UV and FTIR spectral studies. The formation of the most favored six membered binding core of lithium ion with carbonyl groups of purpurin and hydroxyl groups at C-1 and C-4 positions respectively facilitated lithiation process, whereas hydroxyl group at C-2 position remains unaltered.

Stimuli responsive hydrogels derived from a renewable resource: synthesis, self-assembly in water and application in drug delivery

Abstract: We designed and synthesised coumarin-tris derivatives from a renewable resource and well characterized them using different spectral techniques. The self-assembly of coumarin-tris amphiphiles into hydrogels was examined relative to the molecular structure of the amphiphiles. The reversible morphological transition from nanofibers to vesicles and nanotubes has been observed, upon pH variation. Reversible processes and self-assembled structures such as gel, vesicle and nanotube formation have been investigated using optical microscopy and high resolution transmission electron microscopy (HRTEM). 1H NMR and XRD studies clearly suggest that the π–π stacking interactions and hydrogen bonding were the driving force for the process of gelation. The flow behaviour of the hydrogel has been identified using rheological measurements. More importantly, the chemopreventive drug curcumin has been encapsulated into the gel and subsequent release has been achieved by a gel-to-sol transition induced by pH and Fe3+ metal ion stimuli. The reported hydrogel could play a substantial role in the development of new generation stimuli responsive drug delivery systems for in vivo formulations.

Synthesis of 5,6-Dihydrodibenzo[b,h][1,6]naphthyridines via Copper Bromide Catalyzed Intramolecular [4 + 2] Hetero-Diels-Alder Reactions.

Abstract: A highly efficient synthesis of 5,6-dihydrodibenzo[b,h][1,6]naphthyridines was achieved by reaction between 2-(N-propargylamino)benzaldehydes and arylamines in the presence of CuBr2. The in situ generated electron-deficient heterodienes bearing a tethered alkyne partner underwent an intramolecular inverse electron-demand hetero-Diels–Alder reaction followed by air oxidation to furnish the products in high yields. This reaction tolerated a large number of substituents to afford diverse products under mild conditions. This strategy was also successfully extended to the synthesis of 12,13-dihydro-6H-benzo[h]chromeno[3,4-b][1,6]naphthyridin-6-ones starting from 3-amino-2H-chromen-2-one, again in high yields.

Towards sustainable and versatile energy storage devices: an overview of organic electrode materials

Abstract: As an alternative to conventional inorganic intercalation electrode materials, organic electrode materials are promising candidates for the next generation of sustainable and versatile energy storage devices. In this paper we provide an overview of organic electrode materials, including their fundamental knowledge, development history and perspective applications. Based on different organics including n-type, p-type and bipolar, we firstly analyzed their working principles, reaction mechanisms, electrochemical performances, advantages and challenges. To understand the development history and trends in organic electrode materials, we elaborate in detail various organics with different structures, including conducting polymers, organodisulfides, thioethers, nitroxyl radical polymers and conjugated carbonyl compounds. The high electrochemical performance, in addition with the unique features of organics such as flexibility, processability and structure diversity, provide them great perspective in various energy storage devices, including rechargeable Li/Na batteries, supercapacitors, thin film batteries, aqueous rechargeable batteries, redox flow batteries and even all-organic batteries. It is expected that organic electrode materials will show their talents in the “post Li-ion battery” era, towards cheap, green, sustainable and versatile energy storage devices.

Nanostructured anode materials for lithium ion batteries

Abstract: High-energy consumption in our day-to-day life can be balanced not only by harvesting pollution-free renewable energy sources, but also requires proper storage and distribution of energy. In this regard, lithium ion batteries are currently considered as effective energy storage devices and involve the most active research. There exist several review articles dealing with various sections of LIBs, such as the anode, the cathode, electrolytes, electrode–electrolyte interface etc. However, the anode is considered to be a crucial component affecting the performance of LIBs as evident from the tremendous amount of current research work carried out in this area. In the last few years, advancements have been focused more on the fabrication of the nanostructured anode owing to its special properties, such as high surface area, short Li+ ion diffusion path length, high electron transportation rate etc. As the work in this area is growing very fast, the present review paper deliberates the recent developments of anode materials on the nanoscale. Different types of anode materials, such as carbon-based materials, alloys, Si-based materials, transition metal oxides, and transition metal chalcogenides, with their unique physical and electrochemical properties, are discussed. Various approaches to designing materials in the form of 0, 1 and 2D nanostructures and their effect of size and morphology on their performance as anode materials in LIBs are reviewed. Moreover, the article emphasizes smart approaches for making core–shell particles, nanoheterostructures, nanocomposites or nanohybrids with the combination of electrochemically active materials and conductive carbonaceous or electrochemically inactive materials to achieve LIBs with high capacity, high rate capability, and excellent cycling stability. We believe the review paper will provide an update for the reader regarding recent progress on nanostructured anode materials for LIBs.