@article {42510, title = {Sequential energy and electron transfer in polynuclear complex sensitized TiO2 nanoparticles}, journal = {Journal of Physical Chemistry Letters}, volume = {3}, year = {2012}, month = {MAY}, pages = {1543{\textendash}1548}, abstract = {

Polynuclear{\textendash}polypyridyl complexes exhibit a directional energy-transfer property that can improve their photosensitization activity. In the present work, the energy-transfer process is explored in a trinuclear Ru2∧Os1 complex using transient absorption spectroscopy. This study reveals an efficient excitation energy transfer from the terminal (RuII complex) to the core (OsII complex) region in the ultrafast time domain (400 fs{\textendash}40 ps). The excitation energy funnel is useful in improving the functionalized core activity. This is evidenced in an interfacial electron-transfer study of Ru2∧Os1, Ru2∧Ru1, and Os1 complex sensitized TiO2 nanoparticle (TiO2 NP) systems. The intramolecular energy transfer causes sequential excitation of the core part of the Ru2∧Os1 complex, which leads to multiexponential electron injection into TiO2 NP. Besides this, the electronic coupling between the metal ion centers stabilizes the positive charge within the trinuclear complex, which results in a slow charge recombination reaction. This study shows that polynuclear complexes can be very useful for their panchromatic effects, unidirectional energy- and electron-transfer properties.

}, doi = {10.1021/jz3005305}, author = {Verma, Sandeep and Kar, Prasenjit and Banerjee, Tanmay and Das, Amitava and Ghosh, Hirendra N.} } @article { ISI:000346321700065, title = {Size quantization effects on interfacial electron transfer dynamics in Ru(II)-polypyridyl complex sensitized ZnO QDs}, journal = {Journal of Physical Chemistry C}, volume = {118}, number = {49}, year = {2014}, month = {DEC}, pages = {28898-28905}, publisher = {AMER CHEMICAL SOC}, type = {Article}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

Quantum-size confinement in semiconductor material offers size based tunability of interband gap energy as well as intraband sublevels. In this work, size quantization of wide bandgap ZnO quantum dots has been explored in the study of interfacial charge separation reaction using a catechol functionalized Ru(II)polypyridyl complex as a photosensitizer molecule. Femtosecond time-resolved transient absorption studies have revealed multiple electron injection events based on discrete conduction band states of ZnO QDs. The electron injection rates have been rationalized for quantum confinement effects owing to different sizes of ZnO QDs. Furthermore, the size dependency of the intrinsic lifetime of electrons injected into discrete energy levels of ZnO QDs has been revealed in charge recombination reaction with the Ru(III)polypyridyl complex cation. The charge recombination dynamics reveals a competing trend of carrier confinement and carrier leak upon reducing particle size. This study shows the optimization of finite size effects in achieving better interfacial charge separation at the dye/semiconductor interface.

}, issn = {1932-7447}, doi = {10.1021/jp5101158}, author = {Verma, Sandeep and Das, Amitava and Ghosh, Hirendra N.} } @article { ISI:000353702500026, title = {Self-templated chemically stable hollow spherical covalent organic framework}, journal = {Nature Communications}, volume = {6}, year = {2015}, month = {APR}, pages = {6786}, publisher = {NATURE PUBLISHING GROUP}, address = {MACMILLAN BUILDING, 4 CRINAN ST, LONDON N1 9XW, ENGLAND}, abstract = {

Covalent organic frameworks are a family of crystalline porous materials with promising applications. Although active research on the design and synthesis of covalent organic frameworks has been ongoing for almost a decade, the mechanisms of formation of covalent organic frameworks crystallites remain poorly understood. Here we report the synthesis of a hollow spherical covalent organic framework with mesoporous walls in a single-step template-free method. A detailed time-dependent study of hollow sphere formation reveals that an inside-out Ostwald ripening process is responsible for the hollow sphere formation. The synthesized covalent organic framework hollow spheres are highly porous (surface area similar to 1,500m(2) g(-1)), crystalline and chemically stable, due to the presence of strong intramolecular hydrogen bonding. These mesoporous hollow sphere covalent organic frameworks are used for a trypsin immobilization study, which shows an uptake of 15.5 mu mol g(-1) of trypsin.

}, issn = {2041-1723}, doi = {10.1038/ncomms7786}, author = {Kandambeth, Sharath and Venkatesh, V. and Shinde, Digambar B. and Kumari, Sushma and Halder, Arjun and Verma, Sandeep and Banerjee, Rahul} } @article { ISI:000371453700057, title = {Self-exfoliated guanidinium-based ionic covalent organic nanosheets (iCONs)}, journal = {Journal of the American Chemical Society}, volume = {138}, number = {8}, year = {2017}, month = {MAR}, pages = {2823-2828}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

Covalent organic nanosheets (CONs) have emerged as functional two-dimensional materials for versatile applications. Although pi-pi stacking between layers, hydrolytic instability, possible restacking prevents their exfoliation on to few thin layered CONs from crystalline porous polymers. We anticipated rational designing of a structure by intrinsic ionic linker could be the solution to produce self-exfoliated CONs without external stimuli. In an attempt to address this issue, we have synthesized three self-exfoliated guanidinium halide based ionic covalent organic nanosheets (iCONs) with antimicrobial property. Self-exfoliation phenomenon has been supported by molecular dynamics (MD) simulation as well. Intrinsic ionic guanidinium unit plays the pivotal role for both self-exfoliation and antibacterial property against both Gram-positive and Gram-negative bacteria. Using such iCONs, we have devised a Mixed matrix membrane which could be useful for antimicrobial coatings with plausible medical benefits.

}, issn = {0002-7863}, doi = {10.1021/jacs.5b13533}, author = {Mitra, Shouvik and Kandambeth, Sharath and Biswal, Bishnu P. and Khayum, Abdul M. and Choudhury, Chandan Kumar and Mehta, Mihir R. and Kaur, Gagandeep and Banerjee, Subhrashis and Prabhune, Asmita and Verma, Sandeep and Roy, Sudip and Kharul, Ulhas K. and Banerjee, Rahul} }