Browsing by Author "Patra, Amitava"

Now showing 1 - 4 of 4

Core-Size-Dependent Catalytic Properties of Bimetallic Au/Ag Core− Shell Nanoparticles
(ACS Publications, 2017) Haldar, Krishna Kanta; Kundu, Simanta; Patra, Amitava
Bimetallic core−shell nanoparticles have recently emerged as a new class of functional materials because of their potential applications in catalysis, surface enhanced Raman scattering (SERS) substrate and photonics etc. Here, we have synthesized Au/Ag bimetallic core−shell nanoparticles with varying the core diameter. The red-shifting of the both plasmonic peaks of Ag and Au confirms the core−shell structure of the nanoparticles. Transmission electron microscopy (TEM) analysis, line scan EDS measurement and UV−vis study confirm the formation of core−shell nanoparticles. We have examined the catalytic activity of these core−shell nanostructures in the reaction between 4- nitrophenol (4-NP) and NaBH4 to form 4-aminophenol (4-AP) and the efficiency of the catalytic reaction is found to be increased with increasing the core size of Au/Ag core−shell nanocrystals. The catalytic efficiency varies from 41.8 to 96.5% with varying core size from 10 to 100 nm of Au/Ag core−shell nanoparticles, and the Au100/Ag bimetallic core−shell nanoparticle is found to be 12-fold more active than that of the pure Au nanoparticles with 100 nm diameter. Thus, the catalytic properties of the metal nanoparticles are significantly enhanced because of the Au/Ag core−shell structure, and the rate is dependent on the size of the core of the nanoparticles.
Europium Molybdate/Molybdenum Disulfide Nanostructures with Efficient Electrocatalytic Activity for the Hydrogen Evolution Reaction
(American Chemical Society, 2023-04-26T00:00:00) Ghosh, Debarati; Ghosal Chowdhury, Monojit; Biswas, Rathindranath; Haldar, Krishna Kanta; Patra, Amitava
The design of hybrid nanostructures of molybdenum disulfide (MoS2) has been extensively explored as potent electrocatalysts for hydrogen generation reactions. Here, we report the in situ synthesis of a nanocomposite containing europium molybdate [Eu2(MoO4)3] and molybdenum disulfide (MoS2) for an enhanced electrochemical hydrogen evolution reaction (HER). The characteristic X-ray diffraction (XRD) peaks of both 2H-MoS2 and ?-Eu2(MoO4)3 confirm the formation of the nanocomposite. The nanoflower (NF) architecture of MoS2 coupled with flakes of europium molybdate is observed in the transmission electron microscopy (TEM) and scanning electron microscopy (SEM) images, which lead to an enhanced surface area of the nanocomposite. Raman and X-ray photoelectron spectroscopy (XPS) studies reveal a variation in the layer thickness of MoS2 and a significant interfacial electronic interaction between Eu2(MoO4)3 and MoS2. As evident from the small onset potential of ?0.05 V vs reversible hydrogen electrode (RHE) and a lower overpotential value of 186 mV (at a current density of 10 mA/cm2), the nanocomposite outperforms pristine MoS2 nanoflowers in terms of electrocatalytic HER. The charge-transfer resistance of the nanocomposite (80.02 ?) is significantly low compared to pristine MoS2 (158.37 ?), thus confirming the enhanced interfacial charge transfer. The Tafel slope value of the nanocomposite (189 mV/dec) is notably less than that of pristine MoS2 (313 mV/dec), indicating the enhanced HER activity of the nanocomposite. The fabrication of lanthanide-containing MoS2 nanocomposites appears to be promising for an efficient electrocatalytic activity for the hydrogen evolution reaction. � 2023 American Chemical Society
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.
Nonlinear Optical Switching and Enhanced Nonlinear Optical Response of Au−CdSe Heteronanostructures
(ACS Publications, 2016) Sreeramulu, V.; Haldar, Krishna Kanta; 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 plasmonexciton 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.