@article {43313, title = {Cleavable and removable polymer thermosets for organic field effect transistor packaging}, journal = {RSC Advances}, volume = {3}, year = {2013}, month = {SEP}, pages = {22591-22596}, abstract = {Recent years have witnessed tremendous progress in the design and synthesis of electroactive materials for the fabrication of organic electronic devices. However, very little research effort has been devoted to developing organic packaging materials, which are crucial for the efficient functioning of the devices. Polymer thermosets (PTs) are extensively used for the packaging of microelectronic and optoelectronic devices. Although PTs are effective in providing mechanical stability and environmental protection to devices, the removal of PTs without destroying the underlying surface is cumbersome. Facile removal of PTs is essential to reuse the expensive substrates. Herein, we report the preparation of a thermoset using an aliphatic disulfide containing cross-linker, cystamine. By varying the cross-linker concentration, the mechanical property of the thermoset was varied from ductile to brittle. The ductile thermoset was coated on metal, semiconductor and flexible substrates. The thermosets were then cleaved using a biomolecule in neutral pH. We have demonstrated that the cleavage and removal of thermosets don{\textquoteright}t affect the surface properties of the underlying substrates. Furthermore, the thermosets were coated on top of organic field effect transistors to provide environmental protection. The thermoset coated devices showed a charge carrier mobility of 5.3 x 10(-3) cm(2) V-1 s(-1). Then, the thermoset was cleaved and removed, and the substrate was reused for the fabrication of organic field effect transistors with unchanged device efficiencies.}, doi = {10.1039/c3ra43320j}, author = {Arulkashmir, Arulraj and Bhosale, Manik E. and Krishnamoorthy, Kothandam} } @article { ISI:000328283800016, title = {Chemically doped perylene diimide lamellae based field effect transistor with low operating voltage and high charge carrier mobility}, journal = {Chemical Communications}, volume = {50}, number = {3}, year = {2014}, month = {OCT}, pages = {326-328}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

Chemical doping of an electron transporter results in the formation of a radical anion containing semiconductor which showed high electron mobility (13 cm(2) V-1 s(-1)) at low operating voltage (1 V).

}, issn = {1359-7345}, doi = {10.1039/c3cc45391j}, author = {Arulkashmir, Arulraj and Jain, Bhanprakash and John, Jino C. and Roy, Kanak and Krishnamoorthy, Kothandam} } @article { ISI:000351971600028, title = {Chemically reduced organic small-molecule-based lithium battery with improved efficiency}, journal = {Chemistry of Materials}, volume = {27}, number = {6}, year = {2015}, month = {MAR}, pages = {2121-2126}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

Organic lithium batteries are attractive because of the possibility of fabricating lightweight and flexible devices. However, the organic lithium batteries have a few drawbacks. The specific capacity is usually lower than the theoretical capacity, which further decreases upon cycling. Often, the specific capacity is very low compared to theoretical capacity while discharging the battery at moderate and high C rates. To circumvent this issue, we chemically reduced carboxylic acid functionality substituted perylene diimide (benzoic-PDI) with hydrazine. Indeed, we found that the rate of redox reaction as well as the conductivity of the benzoic-PDI increased upon chemical reduction. The battery comprising reduced benzoic-PDI exhibits 100\% Coulombic efficiency and specific capacity while discharging at 20C. The battery also exhibits very high specific energy (213 Wh/kg) and specific power (8548 W/kg). The control experiments confirm our hypothesis of using chemical reduction to improve the performance of organic lithium battery.

}, issn = {0897-4756}, doi = {10.1021/cm5046786}, author = {Bhosale, Manik E. and Krishnamoorthy, Kothandam} } @article {43574, title = {"Click" polymerization: a convenient strategy to prepare designer fullerene materials}, journal = {Materials \& Design}, volume = {108}, year = {2016}, month = {OCT}, pages = {34-41}, abstract = {"Click" polymeric assemblies of fullerenes, thiophenes and aryl compounds were prepared for the first time to study their spectroscopic/chemical/electronic characteristics and possible applications in photovoltaic cells. The GPC and NMR spectroscopic data confirmed a moderate to high degree of polymerization while microscopic pictures showed well-defined arrangements of fullerenes. The FTIR studies indicated that the product is free from starting azide materials, whereas thermogravimetric analysis data suggested a good stability. Band gap of the material was determined using UV-Vis spectroscopy, cyclic voltammetric techniques and compared with computational investigation. The fullerene copolymer was fabricated as acceptor material in a bulk heterojunction photovoltaic cell. (C) 2016 Elsevier Ltd. All rights reserved.}, doi = {10.1016/j.matdes.2016.06.059}, author = {Krishnamurthy, Munusamy and Krishnamoorthy, Kothandam and Arulkashmir, Arulraj and Raghavendra, V. and Murali, Adhigan and Jaisankar, Sellamuthu N. and Murugan, P. and Gurusamy-Thangavelu, Senthil A. and Nasar, A. Sultan and Mandal, Asit Baran and Samanta, Debasis} } @article { ISI:000366859200017, title = {Conjugated porous polymers as precursors for electrocatalysts and storage electrode materials}, journal = {Chemical Communications}, volume = {52}, number = {2}, year = {2016}, month = {OCT}, pages = {316-318}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

Conjugated porous polymers were used as precursors to prepare nitrogen and sulphur doped carbon atoms, which were then used for oxygen reduction and energy storage.

}, issn = {1359-7345}, doi = {10.1039/c5cc08148c}, author = {Bhosale, Manik E. and Illathvalappil, Rajith and Kurungot, Sreekumar and Krishnamoorthy, Kothandam} } @article {43006, title = {Copolymers comprising monomers with various dipole and quadrupole as active material in organic field effect transistors}, journal = {Journal of Physical Chemistry C}, volume = {120}, year = {2016}, month = {NOV}, pages = {26199-26205}, abstract = {

Copolymers of 4,4-difluoro-4-borata-3a-azonia-4a-aza-s-indacene (BODIPY) and diketopyrrolopyrrole (DPP) were synthesized. The BODIPY has a permanent dipole and the DPP has a quadrupole. The dipole and the quadrupole in the monomers are expected to bring the polymers closer and to improve the charge-transport properties. By judicious choice of these monomers, the electron wave function is evenly distributed through the molecules. However, we notice that the torsional angle at the connecting point of BODIPY and DPP is a function of the methyl moieties at the beta,beta{\textquoteright} position of the BODIPY. We found that the polymer comprising DPP and BODIPY without methyl moiety at beta,beta{\textquoteright} position showed a torsional angle of 27, the lowest among the three polymers studied in this work. The absorption spectrum of the polymer showed transitions because of vibronic coupling indicating linearity along the polymer backbone. The band gap of the polymer was found to be 1.2 eV. The thermally stable polymer showed an ambipolar charge transport of 0.01 cm(2)/(V s).

}, doi = {10.1021/acs.jpcc.6b08225}, author = {Singh, Saumya and Chithiravel, Sundaresan and Krishnamoorthy, Kothandam} } @article {46156, title = {Conversion of curved assemblies into two dimensional sheets}, journal = {Nanoscale}, volume = {11}, year = {2019}, month = {MAR}, pages = {5732-5736}, type = {Article}, abstract = {

The design and preparation of organic two dimensional (O2D) sheets and their conversion to curved nanostructures is in its infancy. To convert a flat structure into a curved structure, the molecule must have multiple interaction possibilities and an in-built twist. The conjugated small molecule iso-Indigo (i-Indigo) comprises two phenyl rings that are twisted (the dihedral angle is 15 degrees) at the junction. The i-Indigo has been connected with moieties that impart hydrogen bonding and van der Waals interactions. Due to the presence of the cloud in i-Indigo, - interactions are also present in the molecule. While all three interactions are in operation, rings and toroids are formed. Upon addition of hydrogen bonding competing solvents, the rings and toroids unravel to form O2D sheets. Control molecules that don{\textquoteright}t have hydrogen bonding moieties and - interactions form random assemblies. Please note that the rings, toroids and O2D sheets are formed in a single solvent by simple dissolution, unlike previous approaches that involve multiple steps and solvents.

}, issn = {2040-3364}, doi = {10.1039/c8nr09915d}, author = {Deshmukh, Gunvant and Krishnamoorthy, Kothandam} } @article {48374, title = {Concurrent polyvalent interaction and electrocatalysis to improve lithium-sulfur battery performance}, journal = {Batteries \& Supercaps}, volume = {5}, year = {2022}, month = {FEB}, type = {Article}, abstract = {

Batteries with improved efficiency are desired. Li-S batteries are attractive due to their high specific capacity and energy density. However, sluggish sulfur redox reaction and polysulfide dissolution are significant challenges in Li-S batteries. In this work, we report graphene with doped layer to electrocatalyze the sluggish sulfur redox reaction. The doped layer comprises heteroatoms such as either N or N and S. The doped layer also comprises cations of Ni. We have chosen a {\textquoteleft}{\textquoteleft}doped layer on graphene{\textquoteright}{\textquoteright} over {\textquoteleft}{\textquoteleft}doped graphene{\textquoteright}{\textquoteright} to avoid defects in the basal plane of graphene. We found the doped layer comprising graphene (DLC-G) to electrocatalyze the polysulfide redox reaction. However, the interaction between the doped layer and polysulfide is still weak, hence the dissolution is not suppressed. To circumvent the polysulfide dissolution, graphene with cationic layer was prepared. We found that cations in the layer electrostatically attract the polysulfides due to the polyvalent interaction. Thus, the dissolution is suppressed. While using this material in the Li-S batteries, the specific capacity, energy density and power density were found to be 1345 mAh g(-1), 782 Wh kg(-1) and 4437 W kg(-1), respectively.

}, keywords = {electrocatalysis, graphene, lithium-sulfur battery, mechanical exfoliation, polyvalent interaction}, doi = {10.1002/batt.202100229}, author = {Kumar, Subramani and Krishnamoorthy, Kothandam} } @article {48721, title = {Can metal cations electrocatalyze sulfur redox reaction and suppress polysulfide shuttle?}, journal = {Batteries \& Supercaps}, volume = {6}, year = {2023}, month = {SEP}, type = {Article}, abstract = {

In lithium-sulfur (Li-S) batteries, sulfur undergoes various changes. It switches between cyclic structure and linear structure. The charge on the sulfur varies between a neutral state and a negative charge-bearing state. Due to these changes, the sulfur/polysulfide dissolves in the battery electrolyte. Furthermore, the kinetics of the sulfur redox reaction is sluggish. Therefore, a material that can suppress sulfur/polysulfide dissolution and electrocatalyze sulfur redox reaction is needed. We hypothesize that the polysulfide dissolution can be suppressed if the host exhibits polyvalent electrostatic attraction. Polysulfide is a negative charge-bearing molecule; hence the host must comprise multiple positive charges. Nickel cations with other heteroatoms have been explored as a host in Li-S batteries. The heteroatoms impart additional interactions. The easier way to circumvent the effect of heteroatoms is the addition of metal salts. However, metal salts can either exhibit monovalent or divalent attraction with polysulfides. Those interactions are weak and we must have polyvalent interaction. Towards this objective, we have designed and synthesized a material that comprises multiple divalent cations that is also devoid of heteroatoms. The Li-S batteries fabricated using the metal cation immobilized graphene showed a maximum specific capacity of 1022 mAh/g at 0.1 C rate. Among the metal cations, nickel cations showed better performance than cobalt cations. Thus, we demonstrate that metal cations immobilized on Graphene can efficiently electrocatalyze the sluggish sulfur redox reaction and suppress the polysulfide dissolution.

}, keywords = {electrocatalysis, graphene, lithium-sulfur batteries, metal cations, polysulfides}, doi = {10.1002/batt.202300136}, author = {Kumar, Subramani and Swain, Gitanjali and Krishnamoorthy, Kothandam} }