@article {44426, title = {Au26: a case of fluxionality/co-existence}, journal = {Physical Chemistry Chemical Physics }, volume = {20}, year = {2018}, month = {APR}, pages = {8616-8623}, type = {Article}, abstract = {

The Au26 cluster is one of the widely studied gold clusters in the size range of n = 21{\textendash}30. It has been proposed in a more recent combined experimental and theoretical study that the neutral Au26 cluster is fluxional. The fluxionality of a cluster is relevant to its catalytic applications. In this context, to explore the extent of fluxionality, Born Oppenheimer Molecular Dynamical (BOMD) simulations are carried out on experimentally and theoretically proposed fluxional Au26 conformations (three compact or core{\textendash}shell structures and a high symmetry cage structure). The simulations reveal that the high energy golden tube outperforms the ground state structure (compact C2v conformation) as well as the other two low-symmetry compact conformations in terms of thermal stability. The enhancement in the thermal stability is explained on the basis of structural integrity imposed by the open skeleton of shortest bond distances within Au26-Tube. In addition to this, the homogeneous distribution of charges and the strong s{\textendash}d hybridization exhibited by FMOs are seen to play a pivotal role in increasing the stability of Au26-Tube. The present investigation also reveals that the characteristic fluxionality proposed to exist in the Au26 system is noted only above 400 K and it is missing at room temperature. The simulations also bring forth the question of how relevant a ground state conformation is at working temperatures.

}, issn = {1463-9076}, doi = {10.1039/C7CP07997D}, author = {Joshi, Krati and Krishnamurty, Sailaja} } @article {48935, title = {Active site engineering and theoretical aspects of {\textquoteleft}{\textquoteleft}Superhydrophilic{\textquoteright}{\textquoteright} nanostructure array enabling efficient overall water electrolysis}, journal = {Small}, volume = {19}, year = {2023}, month = {DEC}, type = {Article}, abstract = {

The rational design of noble metal-free electrocatalysts holds great promise for cost-effective green hydrogen generation through water electrolysis. In this context, here, the development of a superhydrophilic bifunctional electrocatalyst that facilitates both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in alkaline conditions is demonstrated. This is achieved through the in situ growth of hierarchical NiMoO4@CoMoO4 center dot xH(2)O nanostructure on nickel foam (NF) via a two-step hydrothermal synthesis method. NiMoO4@CoMoO4 center dot xH(2)O/NF facilitates OER and HER at the overpotentials of 180 and 220 mV, respectively, at the current density of 10 mA cm(-2). The NiMoO4@CoMoO4 center dot xH(2)O/NF parallel to NiMoO4@CoMoO4 center dot xH(2)O/NF cell can be operated at a potential of 1.60 V compared to 1.63 V displayed by the system based on the Pt/C@NF parallel to RuO2@NF standard electrode pair configuration at 10 mA cm(-2) for overall water splitting. The density functional theory calculations for the OER process elucidate that the lowest Delta G of NiMoO4@CoMoO4 compared to both Ni and NiMoO4 is due to the presence of Co in the OER catalytic site and its synergistic interaction with NiMoO4. The preparative strategy and mechanistic understanding make the windows open for the large-scale production of the robust and less expensive electrode material for the overall water electrolysis.

}, keywords = {density functional theory (DFT) study, hydrogen evolution reaction (HER), Hydrothermal synthesis, oxygen evolution reaction (OER), superhydrophilic nanostructures, synergistic interaction, water electrolysis}, issn = {1613-6810}, doi = {10.1002/smll.202304143}, author = {Barik, Sidharth and Kharabe, Geeta Pandurang and Illathvalappil, Rajith and Singh, Chandrodai Pratap and Kanheerampockil, Fayis and Walko, Priyanka S. and Bhat, Suresh K. and Devi, R. Nandini and Vinod, C. P. and Krishnamurty, Sailaja and Kurungot, Sreekumar} } @article {48934, title = {Aniline and indoline donors based far-red active unsymmetrical squaraine dyes for dye sensitized solar cells}, journal = {Chemphotochem}, volume = {8}, year = {2024}, month = {FEB}, type = {Article}, abstract = {

In dye-sensitized solar cells (DSSC), controlling the dye-aggregation on the metal-oxide surface by appending the alkyl groups around the donor or pi-spacer unit of the dye is a potential approach to enhance DSSC efficiency. Further, rigidification of the dye structures by cyclization modulates the photophysical properties of the sensitizer. Here a series of donor-acceptor-donor (D-A-D) type far-red active unsymmetrical squaraine dyes (SQA) have been designed and synthesized, where N,N-dimethylaniline, methylated- and branched-indoline have been used as donor units. These dyes showed absorption between 629-654 nm (lambda max) with the molar extinction coefficient of 1.49-1.94x105 M-1 cm-1. Systematic enhancements in DSSC device efficiency have been observed due to the cyclization and alkyl-groups incorporation in this set of dyes which were further enhanced with the addition of chenodeoxycholic acid (CDCA). The highest DSSC device efficiency of 4.78 \% (Jsc of 8.77 mA/cm2 and Voc of 692 mV) has been achieved for SQA3. The IPCE profile of SQA dyes indicates the contribution of aggregated structures for the photocurrent generation. Further, co-sensitization of SQA3 dye with a complementary visible light active dye AK4 showed the enhanced device efficiency of 6.27 \% with panchromatic IPCE response. Dye rigidification, and controlled aggregation of dyes on TiO2 by means of cyclization of donor unit and introducing the alkyl groups in the dye structure synergistically improve the dye-sensitized solar cell (DSSC) device performance. Donor-Acceptor-Donor (D-A-D) based unsymmetrical squaraine dye SQA3 showed the DSSC device performance of 4.78 \%.image

}, keywords = {co-sensitization, dye-sensitized solar cell, effect of alkyl chain, molecular planarity, squaraine dye}, issn = {2367-0932}, doi = {10.1002/cptc.202300160}, author = {Jadhav, Avinash P. and Singh, Ambarish Kumar and Maibam, Ashakiran and Krishnamurty, Sailaja and Krishnamoorthy, Kothandam and Nithyanandhan, Jayaraj} } @article {50157, title = {Architecting nanographenes for efficient energy storage by tailoring molecular conformation and packing}, journal = {Journal of Materials Chemistry A}, volume = {14}, year = {2026}, month = {JUN}, pages = {22987-22992}, type = {Article}, abstract = {

Structural tuning of electrode materials to enhance electron transport, ion storage capacity, and Li+ diffusion is crucial for developing high-performance lithium-ion batteries (LIBs). In this context, organic functional materials are attractive candidates. Herein, we report a unique molecular design of regioisomeric nanographenes (NGs) with distinct geometries, packing, and topologies for lithium storage as LIB anodes. The nonplanar architectures suppress layer restacking compared to planar analogues, leading to improved electrochemical performance. The pi-extended helical NG 36NG, with larger interlayer spacing and a unique helical geometry, enables faster Li+ diffusion and delivers a higher specific capacity of 719.93 and 203.01 mAh g-1 at 0.1 and 1 A g-1, respectively, with stable performance over 6000 cycles, outperforming 27NG (525.46 and 113.17 mAh g-1 at 0.1 and 1 A g-1, respectively). Single-crystal X-ray analysis reveals markedly different molecular arrangements, directly correlating topology and packing with Li+ storage. This work highlights the critical role of molecular topology in LIB anodes and motivates the design of tailored pi-extended helical nanographenes for energy-storage applications.

}, issn = {2050-7488}, doi = {10.1039/d6ta02052f}, author = {Kumar, Viksit and Javaregowda, Bharathkumar H. and Devasia, George and Krishnamurty, Sailaja and Krishnamoorthy, Kothandam and Santhosh Babu, Sukumaran} }