Paromita Kundu - Profile on Academia.edu (original) (raw)

Papers by Paromita Kundu

3D Au-SiO2 Nanohybrids as a Potential Scaffold Coating Material for Neuroengineering

RSC Adv., 2016

Nanoscale Heterostructures Based on ZnO with Enhanced Visible Light Harvesting Efficiency

Nanoscale Interconnects by Nucleation: Site-Specific Attachment of Molecular Scale Au Nanowire

Functional Nanohybrids with Engineered Interfaces

Nanoscale, 2013

Capping-free and linker-free nanostructures/hybrids possess superior properties due to the presen... more Capping-free and linker-free nanostructures/hybrids possess superior properties due to the presence of pristine surfaces and interfaces. In this review, various methods for synthesizing pristine nanomaterials are presented along with the general principles involved in their morphology control. In wet chemical synthesis, the interplay between various reaction parameters results in diverse morphology. The fundamental principles behind the evolution of morphology including nanoporous aggregates of metals and other inorganic materials, 2D nanocrystals of metals is elucidated by capping-free methods in aqueous medium. In addition, strategies leading to the attachment of bare noble metal nanoparticles to functional oxide supports/reduced graphene oxide has been demonstrated which can serve as a simple solution for obtaining thermally stable and efficient supported catalysts with free surfaces. Solution based synthesis of linker-free oxide-semiconductor hybrids and capping-free metal nanowires on substrates are also discussed in this context with ZnO/CdS and ultrathin Au nanowires as examples.

New Insights into Selective Heterogeneous Nucleation of Metal Nanoparticles on Oxides by Microwave-Assisted Reduction: Rapid Synthesis of High-Activity Supported Catalysts

ACS Nano, 2011

Microwave-based methods are widely employed to synthesize metal nanoparticles on various substrat... more Microwave-based methods are widely employed to synthesize metal nanoparticles on various substrates. However, the detailed mechanism of formation of such hybrids has not been addressed. In this paper, we describe the thermodynamic and kinetic aspects of reduction of metal salts by ethylene glycol under microwave heating conditions. On the basis of this analysis, we identify the temperatures above which the reduction of the metal salt is thermodynamically favorable and temperatures above which the rates of homogeneous nucleation of the metal and the heterogeneous nucleation of the metal on supports are favored. We delineate different conditions which favor the heterogeneous nucleation of the metal on the supports over homogeneous nucleation in the solvent medium based on the dielectric loss parameters of the solvent and the support and the metal/solvent and metal/support interfacial energies. Contrary to current understanding, we show that metal particles can be selectively formed on the substrate even under situations where the temperature of the substrate is lower than that of the surrounding medium. The catalytic activity of the Pt/CeO(2) and Pt/TiO(2) hybrids synthesized by this method for H(2) combustion reaction shows that complete conversion is achieved at temperatures as low as 100 °C with Pt-CeO(2) catalyst and at 50 °C with Pt-TiO(2) catalyst. Our method thus opens up possibilities for rational synthesis of high-activity supported catalysts using a fast microwave-based reduction method.

Theoretical studies exist to compute the atomic arrangement in gold nanowires and the influence o... more Theoretical studies exist to compute the atomic arrangement in gold nanowires and the influence on their electronic behavior with decreasing diameter.

Electrical transport measurements on ultrathin single-crystalline Au nanowires, synthesized via a... more Electrical transport measurements on ultrathin single-crystalline Au nanowires, synthesized via a wet chemical route, show an unexpected insulating behavior. The linear response electrical resistance exhibits a power-law dependence on temperature. In addition, the variation of current over a wide range of temperature and voltage obeys a universal scaling relation that provides compelling evidence for a non-Fermi liquid behavior. Our results demonstrate that the quantum ground state in ultrathin nanowires of simple metallic systems can be radically different from their bulk counterparts and can be described in terms of a TomonagaÀLuttinger liquid (TLL), in the presence of remarkably strong electronÀelectron interactions.

We report a reversible phase transformation of platelet-shaped ZnS nanostructures between wurtzit... more We report a reversible phase transformation of platelet-shaped ZnS nanostructures between wurtzite (WZ) and zinc blende (ZB) phases by reversible insertion/ ejection of dopant Mn(II) ions induced by a thermocyclic process. In a reaction flask loaded with WZ ZnS platelets and Mn molecular precursors, during heating Mn ions are incorporated and change the phase of the host nanostructures to ZB; during cooling Mn ions are spontaneously ejected, returning the host nanoplatelets to the original WZ phase. These reversible changes are monitored for several cycles with PL, EPR, XRD, and HRTEM. Interestingly, the (0001) WZ platelets transform to (110) ZB following a nucleation and growth process triggered by a local increase/ depletion of the Mn 2þ concentration in the nanocrystals.

JA907874H Figure 2. Bright field TEM images of molecular scale Au nanowires (a) originating from ... more JA907874H Figure 2. Bright field TEM images of molecular scale Au nanowires (a) originating from and (b) terminating at ZnO nanorods, on (c) MgO nanocube, (d) carbon nanotube, and (e) hydroxyapatite nanorod. (f) multipodal Au nanostructures grown on ZnO nanorod surfaces.

† Electronic supplementary information (ESI) available: Experimental section, XEDS of the hybrids... more † Electronic supplementary information (ESI) available: Experimental section, XEDS of the hybrids, PL spectra, additional XPS data, TEM images of hybrid synthesized without MW and hybrids characterized after catalysis. See

We demonstrate a simple strategy of obtaining clean, ultrathin single crystal Au nanowires on sub... more We demonstrate a simple strategy of obtaining clean, ultrathin single crystal Au nanowires on substrates and interconnecting predefined contacts with an insight into the growth mechanism. The pristine nature enables electron transport measurement through such ultrathin wires and opens up possibilities of exploring its properties for a wide range of applications.

Semiconductor based nanoscale heterostructures are promising candidates for photocatalytic and ph... more Semiconductor based nanoscale heterostructures are promising candidates for photocatalytic and photovoltaic applications with the sensitization of a wide bandgap semiconductor with a narrow bandgap material being the most viable strategy to maximize the utilization of the solar spectrum. Here, we present a simple wet chemical route to obtain nanoscale heterostructures of ZnO/CdS without using any molecular linker. Our method involves the nucleation of a Cd-precursor on ZnO nanorods with a subsequent sulfidation step leading to the formation of the ZnO/CdS nanoscale heterostructures. Excellent control over the loading of CdS and the microstructure is realized by merely changing the initial concentration of the sulfiding agent. We show that the heterostructures with the lowest CdS loading exhibit an exceptionally high activity for the degradation of methylene blue (MB) under solar irradiation conditions; microstructural and surface analysis reveals that the higher activity in this case is related to the dispersion of the CdS nanoparticles on the ZnO nanorod surface and to the higher concentration of surface hydroxyl species. Detailed analysis of the mechanism of formation of the nanoscale heterostructures reveals that it is possible to obtain deterministic control over the nature of the interfaces. Our synthesis method is general and applicable for other heterostructures where the interfaces need to be engineered for optimal properties. In particular, the absence of any molecular linker at the interface makes our method appealing for photovoltaic applications where faster rates of electron transfer at the heterojunctions are highly desirable.

Gold-silica hybrids are appealing in different fields of applications like catalysis, sensorics, ... more Gold-silica hybrids are appealing in different fields of applications like catalysis, sensorics, drug delivery, and biotechnology. In most cases, the morphology and distribution of the heterounits play significant roles in their functional behavior. Methods of synthesizing these hybrids, with variable ordering of the heterounits, are replete; however, a complete characterization in three dimensions could not be achieved yet. A simple route to the synthesis of Au-decorated SiO 2 spheres is demonstrated and a study on the 3D ordering of the heterounits by scanning transmission electron microscopy (STEM) tomography is presented-at the final stage, intermediate stages of formation, and after heating the hybrid. The final hybrid evolves from a soft self-assembled structure of Au nanoparticles. The hybrid shows good thermal stability up to 400 8C, beyond which the Au particles start migrating inside the SiO 2 matrix. This study provides an insight in the formation mechanism and thermal stability of the structures which are crucial factors for designing and applying such hybrids in fields of catalysis and biotechnology. As the method is general, it can be applied to make similar hybrids based on SiO 2 by tuning the reaction chemistry as needed.

Shrinking metallic systems to molecular scale makes the effects of the surrounding environment an... more Shrinking metallic systems to molecular scale makes the effects of the surrounding environment and the charge confi gurations extremely important to their electrical properties. This is particularly true for one-dimensional (1D) or quasi-1D metals if these are to be used as reliable interconnects or electronic circuit elements. In 1D, Coulombic interaction and random background disorder form the major factors that determine the charge transport. Recent experiments demonstrate that the Coulombic interaction may lead to new quantum many-body phases, for example the Tomonaga-Luttinger liquid (TLL) in atomically thin gold nanowires, [ 7 , 8 ] but both the nature and effect of disorder on charge transport in these phases remain virtually unknown.

Existing and emerging strategies for the synthesis of nanoscale heterostructures

Physical Chemistry Chemical Physics, 2011

Development of new multifunctional nanostructures relies on the ability to make new materials at ... more Development of new multifunctional nanostructures relies on the ability to make new materials at the nanoscale with control over size, shape and composition. While this control is extremely important to tune several properties, an alternative strategy is to create active interfaces between two or more nanostructures to form nanoscale heterostructures. In these heterostructures, the interfaces play a key role in stabilizing and enhancing the efficiency of the individual components for various applications. In this article, we discuss synthesis methods of different types of nanoscale heterostructures and the role of interfaces in various applications. We present the current state-of-the-art in designing heterostructures and possible upcoming synthetic strategies with their advantages and disadvantages. We present how such heterostructures are highly efficient for catalytic, photovoltaic and nanoelectronic applications drawing several examples from our own studies and from the literature.

Journal of Physical Chemistry C, 2009