Department Of Chemistry

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Author: search.filters.author.Haldar, Krishan Kant

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    Au/CdSe hybrid nanoflowers: a high photocurrent generating photoelectrochemical cells
    (Springer, 2019) Haldar, Krishan Kant; Biswas, R; Patra, A; Halder, K.K; Sen, T.
    Photoelectrochemical cell composed of solution-processed nanoflower heterostructure of Au core and eight CdSe petals was investigated for enhanced photocurrent generation. The electrode of CdSe nanorods displayed photocurrent density of 2.1 mA/cm 2 whereas the Au core CdSe nanoflower exhibited 4.6 mA/cm 2 corresponding to a 119% increase during photoelectrochemical cell performance. Both electrodes showed prompt response to the on/off cycles of light, the photocurrent gain (I Photon /I dark ) in CdSe nanorods is 124.7, while the value is 223.3 for Au/CdSe nanoflower, calculated from the growth-decay curves. Photoresponse time was dramatically improved for Au/CdSe nanoflower samples due to increasing in 66% incident photon-to-current emission. Electron lifetime of 21.63 and 48.71 ns was observed for the electrode of CdSe nanorods and Au/CdSe nanoflowers respectively. The prolonged electron lifetime in the case of the electrode of Au/CdSe nanoflowers was responsible for improving charge separation and as a consequence, higher photocurrent generation. © 2018, Springer Nature Switzerland AG.
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    Zn(II) Di-isobutyldithiocarbamate Complex Enabled Efficient Synthesis of Au/ZnS Nanocomposite Core-shell in One Pot
    (Wiley, 2019) Biswas, R; Singh, H; Banerjee, B; Haldar, Krishan Kant
    Here, we demonstrate a one pot synthesis of gold/zinc sulphide (Au/ZnS) core-shell type composite nanostructure via thermal decomposition of single molecular precursor Zn(II)di-isobutyldithiocarbamate complex. In these Au/ZnS core-shell type hybrid nanostructures where ZnS quantum dots are assembled onto Au nanoparticles surface were prepared via a facile and reproducible approach under mild conditions. The crystalline nature and interface of these Au/ZnS core-shell type composite nanostructures were confirmed by X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), High-resolution transmission electron microscopy (HRTEM) and inverted TEM images. Here Zn(II)di-isobutyldithiocarbamate complex acts as ZnS source as well as reducing and stabilizing agent for Au 0 at their nanoscale range by coating in the reaction medium. © 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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    Nonlinear Optical Switching and Enhanced Nonlinear Optical Response of Au–CdSe Heteronanostructures
    (ACS Publications, 2014) Sreeramulu, V.; Haldar, Krishan Kant; Patra, Amitava; Rao, D. Narayana
    The metal–semiconductor heterostructures have recently emerged as a new class of functional materials for their potential applications due to plasmon-exciton interactions. Here, we demonstrate the nonlinear optical switching and enhanced nonlinear optical response of Au–CdSe heterostructures. The nonlinear optical properties of CdSe quantum dots and Au–CdSe heteronanostructures are investigated by using a Z-scan technique at 532 nm picosecond laser pulses, and 800 nm femtosecond laser pulses. Interestingly, we observe switching behavior from saturable absorption (SA) to reverse saturable absorption (RSA) with increasing laser intensity. The effective two-photon absorption cross section (σeff) of Au–CdSe heteronanostructures is greatly enhanced which is attributed to charge transfer between CdSe and Au nanoparticles. The nonlinear refraction changes its sign from positive to negative nonlinearity at higher intensities for Au–CdSe heterostructures. Third order nonlinear optical susceptibility is being measured by using the DFWM technique at 532 nm. Similar switching behavior is observed in Au–CdSe heteronanostructures at nonresonant excitations (800 nm), where a CdSe quantum dot shows reverse saturable absorption behavior attributed to the two-photon absorption. The optical switching behavior of these heterostructures could play a potential role in photonics and optoelectronic applications.