Journal of Material Sciences & Engineering, Jul 15, 2021
Rupali Nagar is working at Symbiosis Institute of Technology (SIT), Pune, India as an Assistant P... more Rupali Nagar is working at Symbiosis Institute of Technology (SIT), Pune, India as an Assistant Professor in the Department of Applied Science and is the Group Leader of Nanomaterials for Energy Applications Lab at SIT. She completed her Ph.D. from Indian Institute of Technology Delhi (IIT D) and continued her research while working at Indian Institute of Technology Madras (IIT M) as Project Officer till 2012. Her research interests include studying nanomaterials for energy and gas sensing applications.
This review is focused on the topical developments in the synthesis of nanocomposites using the s... more This review is focused on the topical developments in the synthesis of nanocomposites using the simplest top-down approach, mechanochemical milling, and the related aspects of the interfacial interactions. Milling constraints include time duration of milling, ball size, the ball-to-sample content proportion, rotation speed, and energy that took part in a vital part of the structure–property relationships and composite interactions. Milled nanocomposites are being used in different structural applications for their higher performance rate and throughput. The synthesis of different nanocomposites and the effect of various parameters on the mill-ability of nanocomposites are discussed. Moreover, some of the major advancements in the energy sector are discussed in the latter part of the review.
Fractals are structures that have intricate geometries and are commonly found in nature. By contr... more Fractals are structures that have intricate geometries and are commonly found in nature. By controlling the growth conditions conducive for fractal growth, a very simple and novel technique to grow tin oxide (SnO2) fabricated fractals (fab-fracs) under lab environment is reported. This pulsed microwave-assisted sol-gel synthesis technique yielded growth on a large-scale glass substrate of 5-inch diameter. The fab-fracs being reported here have geometries varying from rhombohedral to fern-like to sword-like shape. The fab-fracs exhibited a fractal dimension ranging from 1.52 to 1.85. The SnO2 fab-fracs showed turn-on field equal to 12.6 and threshold-field of 15.6 V/μm, respectively at current densities of 1 and 10 μA/cm2. For 20.4 V/μm applied field, an emission current density of 30 μA/cm2 was obtained. These fab-fracs exhibited a field-enhancement factor of 450 cm−1, which is attributed to the sharp facets of the fractal geometry. This paper shows the growth of fractals in different geometries and discusses the growth mechanism in detail. The synthesis technique is versatile and can be used to grow other fractal and multi-dendritic structures also. Fractals belong to the subset that follows complex growth mechanisms involving self-organization and non-equilibrium thermodynamic conditions, which if understood, can lead to newer growth techniques in material science. The graphical abstract depicts the optical image of a large-scale SnO2 fractal in the background. Foreground shows much smaller rhombohedral fractals. A representative field emission curve shows the performance of crushed fractals. Top-right corner depicts the emission spot. The graphical abstract depicts the optical image of a large-scale SnO2 fractal in the background. Foreground shows much smaller rhombohedral fractals. A representative field emission curve shows the performance of crushed fractals. Top-right corner depicts the emission spot. Simple and novel technique to grow large-scale fractals in lab environment. Fab-fracs with fractal dimensions of ~1.52–1.85 successfully grown. Fractals exhibit the field emission properties. Simple and novel technique to grow large-scale fractals in lab environment. Fab-fracs with fractal dimensions of ~1.52–1.85 successfully grown. Fractals exhibit the field emission properties.
With advancements in telecommunication technology, data or information transfer has become the ba... more With advancements in telecommunication technology, data or information transfer has become the backbone of daily transactions. This underlines the importance of transferring data securely by employing techniques of encryption. The...
Acid-etched graphitic carbon nitride (TGCN) nanosheets decorated with polyaniline (PANI) nanofibe... more Acid-etched graphitic carbon nitride (TGCN) nanosheets decorated with polyaniline (PANI) nanofibers for the adsorption and photocatalytic degradation of Methyl Orange (MO) and Congo Red (CR) toxic textile dyes.
The role of functionalized multiwalled carbon nanotubes (MWNTs) decorated with platinum nanoparti... more The role of functionalized multiwalled carbon nanotubes (MWNTs) decorated with platinum nanoparticles (Pt/f-MWNTs) and platinumecobalt alloy nanoparticles (Pt 3 Co/f-MWNTs) has been investigated for oxygen reduction reaction (ORR) in a proton exchange membrane fuel cell. The electrocatalysts are synthesized by a conventional sodium borohydride reduction method and modified polyol reduction method. The modified polyol reduction method yields better uniform dispersion, higher loading and optimum particle size of Pt and Pt 3 Co alloy nanoparticles over the MWNTs compared to the conventional sodium borohydride reduction method. The electrochemical surface area of the electrocatalysts is calculated using cyclic voltammetry. Pt 3 Co/f-MWNTs synthesized via modified polyol reduction method yield the highest performance with a maximum power density of 798 mW cm À2 at 60 C without any back pressure. The enhanced catalytic activity of Pt 3 Co/ f-MWNTs toward ORR is attributed to uniform dispersion and optimum particle size of Pt 3 Co alloy nanoparticles over the surface of f-MWNTs.
ABSTRACT A novel synthesis procedure is devised to obtain nitrogen-doping in hydrogen-exfoliated ... more ABSTRACT A novel synthesis procedure is devised to obtain nitrogen-doping in hydrogen-exfoliated graphene (HEG) sheets. An anionic polyelectrolyte–conducting polymer duo is used to form a uniform coating of the polymer over graphene sheets. Pyrolysis of graphene coated with polypyrrole, a nitrogen-containing polymer, in an inert environment leads to the incorporation of nitrogen atoms in the graphene network with simultaneous removal of the polymer. These nitrogen-doped graphene (N-HEG) sheets are used as catalyst support for dispersing platinum and platinum–cobalt alloy nanoparticles synthesized by the modified-polyol reduction method, yielding a uniform dispersion of the catalyst nanoparticles. Compared to commercial Pt/C electrocatalyst, Pt–Co/N-HEG cathode electrocatalyst exhibits four times higher power density in proton exchange membrane fuel cells, which is attributed to the excellent dispersion of Pt–Co alloy nanoparticles on the N-HEG support, the alloying effect of Pt–Co, and the high electrocatalytic activity of the N-HEG support. A stability study shows that Pt/N-HEG and Pt–Co/N-HEG cathode electrocatalysts are highly stable in acidic media. The study shows two promising electrocatalysts for proton exchange membrane fuel cells, which on the basis of performance and stability present the possibility of replacing contemporary electrocatalysts.
The availability of water, which is the basis for all life forms, makes life on our planet possib... more The availability of water, which is the basis for all life forms, makes life on our planet possible. Plants naturally convert water into hydrogen and oxygen by photosynthesis that is useful for sustaining life. However, with the world’s increasing population comes an increasing demand for water. In fact, many parts of the world face a water crisis either because of the geographical location, the misuse of water, and/or the mismanagement of the wastewater coming from residential areas and industrial complexes, problems that sooner or later will become a crisis if not managed in a timely and effective way. Therefore judicious use of the available water resources and development of a structured wastewater management system are needed. This chapter focuses on two solar energy-based uses of nanocomposites, namely decontamination of organic pollutants in water and hydrogen production. The hydrogen released via photocatalysis of water can be stored and used as an energy carrier. Semiconduc...
Advances in Natural Sciences: Nanoscience and Nanotechnology
Sensors function by interacting with an appropriate stimulus, undergo a change in property, which... more Sensors function by interacting with an appropriate stimulus, undergo a change in property, which is then diagnosed by making some measurements. For any sensor, the type of interaction between analyte and sensor surface determines its overall performance. This article explores the philosophy in which primary measurements like response curves can hold information on the “type” of interaction occurring between analyte and sensing material. As case study, titanium oxide (TiO2) pellet sensors fabricated by sol-gel growth of TiO2 nanoparticles (as-grown and annealed) are investigated for humidity sensing at room temperature. The sensors display a very fast response in the 0%–30% relative humidity (%RH) range and return to their initial state without applying any external heat treatment. The response curves are analysed in view of adsorption processes guided by Langmuir isotherms. Correlation between sensor microstructure, adsorption processes and response curve is used to build the mecha...
Fractals are intriguing structures that repeat themselves at various length scales. Interestingly... more Fractals are intriguing structures that repeat themselves at various length scales. Interestingly, fractals can also be fabricated artificially in labs under controlled growth environments and be explored for various applications. Such fractals have a repeating unit that spans in length from nano- to millimeter range. Fractals thus can be regarded as connectors that structurally bridge the gap between the nano- and the macroscopic worlds and have a hybrid structure of pores and repeating units. This article presents a comprehensive review on inorganic fabricated fractals (fab-fracs) synthesized in labs and employed as gas sensors across materials, morphologies, and gas analytes. The focus is to investigate the morphology-driven gas response of these fab-fracs and identify key parameters of fractal geometry in influencing gas response. Fab-fracs with roughened microstructure, pore-network connectivity, and fractal dimension (D) less than 2 are projected to be possessing better gas se...
... Cited By in Scopus (0). Permissions & Reprints. Tailoring the spring constant of ... more ... Cited By in Scopus (0). Permissions & Reprints. Tailoring the spring constant of Si nanorod structures using swift heavy ion irradiation. Rupali Nagar a , D. Kanjilal b , BR Mehta a and JP Singh a , Corresponding Author Contact Information , E-mail The Corresponding Author. ...
Recent advances in hydrogen storage using catalytically and chemically modified graphene nanocomp... more Recent advances in hydrogen storage using catalytically and chemically modified graphene nanocomposites are reviewed and its future outlook discussed.
Journal of Material Sciences & Engineering, Jul 15, 2021
Rupali Nagar is working at Symbiosis Institute of Technology (SIT), Pune, India as an Assistant P... more Rupali Nagar is working at Symbiosis Institute of Technology (SIT), Pune, India as an Assistant Professor in the Department of Applied Science and is the Group Leader of Nanomaterials for Energy Applications Lab at SIT. She completed her Ph.D. from Indian Institute of Technology Delhi (IIT D) and continued her research while working at Indian Institute of Technology Madras (IIT M) as Project Officer till 2012. Her research interests include studying nanomaterials for energy and gas sensing applications.
This review is focused on the topical developments in the synthesis of nanocomposites using the s... more This review is focused on the topical developments in the synthesis of nanocomposites using the simplest top-down approach, mechanochemical milling, and the related aspects of the interfacial interactions. Milling constraints include time duration of milling, ball size, the ball-to-sample content proportion, rotation speed, and energy that took part in a vital part of the structure–property relationships and composite interactions. Milled nanocomposites are being used in different structural applications for their higher performance rate and throughput. The synthesis of different nanocomposites and the effect of various parameters on the mill-ability of nanocomposites are discussed. Moreover, some of the major advancements in the energy sector are discussed in the latter part of the review.
Fractals are structures that have intricate geometries and are commonly found in nature. By contr... more Fractals are structures that have intricate geometries and are commonly found in nature. By controlling the growth conditions conducive for fractal growth, a very simple and novel technique to grow tin oxide (SnO2) fabricated fractals (fab-fracs) under lab environment is reported. This pulsed microwave-assisted sol-gel synthesis technique yielded growth on a large-scale glass substrate of 5-inch diameter. The fab-fracs being reported here have geometries varying from rhombohedral to fern-like to sword-like shape. The fab-fracs exhibited a fractal dimension ranging from 1.52 to 1.85. The SnO2 fab-fracs showed turn-on field equal to 12.6 and threshold-field of 15.6 V/μm, respectively at current densities of 1 and 10 μA/cm2. For 20.4 V/μm applied field, an emission current density of 30 μA/cm2 was obtained. These fab-fracs exhibited a field-enhancement factor of 450 cm−1, which is attributed to the sharp facets of the fractal geometry. This paper shows the growth of fractals in different geometries and discusses the growth mechanism in detail. The synthesis technique is versatile and can be used to grow other fractal and multi-dendritic structures also. Fractals belong to the subset that follows complex growth mechanisms involving self-organization and non-equilibrium thermodynamic conditions, which if understood, can lead to newer growth techniques in material science. The graphical abstract depicts the optical image of a large-scale SnO2 fractal in the background. Foreground shows much smaller rhombohedral fractals. A representative field emission curve shows the performance of crushed fractals. Top-right corner depicts the emission spot. The graphical abstract depicts the optical image of a large-scale SnO2 fractal in the background. Foreground shows much smaller rhombohedral fractals. A representative field emission curve shows the performance of crushed fractals. Top-right corner depicts the emission spot. Simple and novel technique to grow large-scale fractals in lab environment. Fab-fracs with fractal dimensions of ~1.52–1.85 successfully grown. Fractals exhibit the field emission properties. Simple and novel technique to grow large-scale fractals in lab environment. Fab-fracs with fractal dimensions of ~1.52–1.85 successfully grown. Fractals exhibit the field emission properties.
With advancements in telecommunication technology, data or information transfer has become the ba... more With advancements in telecommunication technology, data or information transfer has become the backbone of daily transactions. This underlines the importance of transferring data securely by employing techniques of encryption. The...
Acid-etched graphitic carbon nitride (TGCN) nanosheets decorated with polyaniline (PANI) nanofibe... more Acid-etched graphitic carbon nitride (TGCN) nanosheets decorated with polyaniline (PANI) nanofibers for the adsorption and photocatalytic degradation of Methyl Orange (MO) and Congo Red (CR) toxic textile dyes.
The role of functionalized multiwalled carbon nanotubes (MWNTs) decorated with platinum nanoparti... more The role of functionalized multiwalled carbon nanotubes (MWNTs) decorated with platinum nanoparticles (Pt/f-MWNTs) and platinumecobalt alloy nanoparticles (Pt 3 Co/f-MWNTs) has been investigated for oxygen reduction reaction (ORR) in a proton exchange membrane fuel cell. The electrocatalysts are synthesized by a conventional sodium borohydride reduction method and modified polyol reduction method. The modified polyol reduction method yields better uniform dispersion, higher loading and optimum particle size of Pt and Pt 3 Co alloy nanoparticles over the MWNTs compared to the conventional sodium borohydride reduction method. The electrochemical surface area of the electrocatalysts is calculated using cyclic voltammetry. Pt 3 Co/f-MWNTs synthesized via modified polyol reduction method yield the highest performance with a maximum power density of 798 mW cm À2 at 60 C without any back pressure. The enhanced catalytic activity of Pt 3 Co/ f-MWNTs toward ORR is attributed to uniform dispersion and optimum particle size of Pt 3 Co alloy nanoparticles over the surface of f-MWNTs.
ABSTRACT A novel synthesis procedure is devised to obtain nitrogen-doping in hydrogen-exfoliated ... more ABSTRACT A novel synthesis procedure is devised to obtain nitrogen-doping in hydrogen-exfoliated graphene (HEG) sheets. An anionic polyelectrolyte–conducting polymer duo is used to form a uniform coating of the polymer over graphene sheets. Pyrolysis of graphene coated with polypyrrole, a nitrogen-containing polymer, in an inert environment leads to the incorporation of nitrogen atoms in the graphene network with simultaneous removal of the polymer. These nitrogen-doped graphene (N-HEG) sheets are used as catalyst support for dispersing platinum and platinum–cobalt alloy nanoparticles synthesized by the modified-polyol reduction method, yielding a uniform dispersion of the catalyst nanoparticles. Compared to commercial Pt/C electrocatalyst, Pt–Co/N-HEG cathode electrocatalyst exhibits four times higher power density in proton exchange membrane fuel cells, which is attributed to the excellent dispersion of Pt–Co alloy nanoparticles on the N-HEG support, the alloying effect of Pt–Co, and the high electrocatalytic activity of the N-HEG support. A stability study shows that Pt/N-HEG and Pt–Co/N-HEG cathode electrocatalysts are highly stable in acidic media. The study shows two promising electrocatalysts for proton exchange membrane fuel cells, which on the basis of performance and stability present the possibility of replacing contemporary electrocatalysts.
The availability of water, which is the basis for all life forms, makes life on our planet possib... more The availability of water, which is the basis for all life forms, makes life on our planet possible. Plants naturally convert water into hydrogen and oxygen by photosynthesis that is useful for sustaining life. However, with the world’s increasing population comes an increasing demand for water. In fact, many parts of the world face a water crisis either because of the geographical location, the misuse of water, and/or the mismanagement of the wastewater coming from residential areas and industrial complexes, problems that sooner or later will become a crisis if not managed in a timely and effective way. Therefore judicious use of the available water resources and development of a structured wastewater management system are needed. This chapter focuses on two solar energy-based uses of nanocomposites, namely decontamination of organic pollutants in water and hydrogen production. The hydrogen released via photocatalysis of water can be stored and used as an energy carrier. Semiconduc...
Advances in Natural Sciences: Nanoscience and Nanotechnology
Sensors function by interacting with an appropriate stimulus, undergo a change in property, which... more Sensors function by interacting with an appropriate stimulus, undergo a change in property, which is then diagnosed by making some measurements. For any sensor, the type of interaction between analyte and sensor surface determines its overall performance. This article explores the philosophy in which primary measurements like response curves can hold information on the “type” of interaction occurring between analyte and sensing material. As case study, titanium oxide (TiO2) pellet sensors fabricated by sol-gel growth of TiO2 nanoparticles (as-grown and annealed) are investigated for humidity sensing at room temperature. The sensors display a very fast response in the 0%–30% relative humidity (%RH) range and return to their initial state without applying any external heat treatment. The response curves are analysed in view of adsorption processes guided by Langmuir isotherms. Correlation between sensor microstructure, adsorption processes and response curve is used to build the mecha...
Fractals are intriguing structures that repeat themselves at various length scales. Interestingly... more Fractals are intriguing structures that repeat themselves at various length scales. Interestingly, fractals can also be fabricated artificially in labs under controlled growth environments and be explored for various applications. Such fractals have a repeating unit that spans in length from nano- to millimeter range. Fractals thus can be regarded as connectors that structurally bridge the gap between the nano- and the macroscopic worlds and have a hybrid structure of pores and repeating units. This article presents a comprehensive review on inorganic fabricated fractals (fab-fracs) synthesized in labs and employed as gas sensors across materials, morphologies, and gas analytes. The focus is to investigate the morphology-driven gas response of these fab-fracs and identify key parameters of fractal geometry in influencing gas response. Fab-fracs with roughened microstructure, pore-network connectivity, and fractal dimension (D) less than 2 are projected to be possessing better gas se...
... Cited By in Scopus (0). Permissions & Reprints. Tailoring the spring constant of ... more ... Cited By in Scopus (0). Permissions & Reprints. Tailoring the spring constant of Si nanorod structures using swift heavy ion irradiation. Rupali Nagar a , D. Kanjilal b , BR Mehta a and JP Singh a , Corresponding Author Contact Information , E-mail The Corresponding Author. ...
Recent advances in hydrogen storage using catalytically and chemically modified graphene nanocomp... more Recent advances in hydrogen storage using catalytically and chemically modified graphene nanocomposites are reviewed and its future outlook discussed.
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