Author
Ravi P. N. Tripathi
Other affiliations: Indian Institute of Technology Gandhinagar, Indian Institute of Science, University of Alabama at Birmingham ...read more
Bio: Ravi P. N. Tripathi is an academic researcher from Missouri University of Science and Technology. The author has contributed to research in topics: Plasmon & Nanowire. The author has an hindex of 8, co-authored 28 publications receiving 1863 citations. Previous affiliations of Ravi P. N. Tripathi include Indian Institute of Technology Gandhinagar & Indian Institute of Science.
Papers
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TL;DR: By utilizing dual excitation of plasmons at metal-fluid interface, this work creates interacting assemblies of metal nanoparticles, which may be further harnessed in dynamic lithography of dispersed nanostructures and have implications in realizing optically addressable, plasmofluidic, single-molecule detection platforms.
Abstract: Single-molecule surface-enhanced Raman scattering (SM-SERS) is one of the vital applications of plasmonic nanoparticles. The SM-SERS sensitivity critically depends on plasmonic hot-spots created at the vicinity of such nanoparticles. In conventional fluid-phase SM-SERS experiments, plasmonic hot-spots are facilitated by chemical aggregation of nanoparticles. Such aggregation is usually irreversible, and hence, nanoparticles cannot be re-dispersed in the fluid for further use. Here, we show how to combine SM-SERS with plasmon polariton-assisted, reversible assembly of plasmonic nanoparticles at an unstructured metal–fluid interface. One of the unique features of our method is that we use a single evanescent-wave optical excitation for nanoparticle assembly, manipulation and SM-SERS measurements. Furthermore, by utilizing dual excitation of plasmons at metal–fluid interface, we create interacting assemblies of metal nanoparticles, which may be further harnessed in dynamic lithography of dispersed nanostructures. Our work will have implications in realizing optically addressable, plasmofluidic, single-molecule detection platforms. Plasmonic hot-spot generation in solution is not reversible for single-molecule surface-enhanced Raman scattering, which limits its applications. Patra et al.tackle this problem by integrating this technique with thermo-plasmon-assisted reconfiguration of nanoparticles at a metal–fluid interface.
1,705 citations
TL;DR: This study has shown that the photoluminescence intensity can be enhanced and quenched in comparison with pristine monolayer MoS2, and can facilitate the incorporation of plasmon-enhanced transition metal dichalcogenide structures in photodetector, sensor and light emitter applications.
Abstract: Modulation of photoluminescence of atomically thin transition metal dichalcogenide two-dimensional materials is critical for their integration in optoelectronic and photonic device applications. By coupling with different plasmonic array geometries, we have shown that the photoluminescence intensity can be enhanced and quenched in comparison with pristine monolayer MoS2. The enhanced exciton emission intensity can be further tuned by varying the angle of polarized incident excitation. Through controlled variation of the structural parameters of the plasmonic array in our experiment, we demonstrate modulation of the photoluminescence intensity from nearly fourfold quenching to approximately threefold enhancement. Our data indicates that the plasmonic resonance couples to optical fields at both, excitation and emission bands, and increases the spontaneous emission rate in a double spacing plasmonic array structure as compared with an equal spacing array structure. Furthermore our experimental results are supported by numerical as well as full electromagnetic wave simulations. This study can facilitate the incorporation of plasmon-enhanced transition metal dichalcogenide structures in photodetector, sensor and light emitter applications.
56 citations
TL;DR: It is experimentally shown how a single Ag nanoparticle coupled to an Ag nanowire (NW) can convert propagating surface plasmon polaritons to directional photons and can influence the directionality of molecular-fluorescence emission, thus functioning as an optical antenna.
Abstract: We experimentally show how a single Ag nanoparticle (NP) coupled to an Ag nanowire (NW) can convert propagating surface plasmon polaritons to directional photons. By employing dual-excitation Fourier microscopy with spatially filtered collection-optics, we show single- and dual-directional out-coupling of light from NW-NP junction for plasmons excited through glass-substrate and air-superstrate. Furthermore, we show NW-NP junction can influence the directionality of molecular-fluorescence emission, thus functioning as an optical antenna. The results discussed herein may have implications in realizing directional single-photon sources and quantum plasmon circuitry.
22 citations
TL;DR: In this paper, a single Ag nanoparticle coupled to an Ag nanowire (NW) can convert propagating surface plasmon polaritons to directional photons by employing dual-excitation Fourier microscopy with spatially filtered collection-optics.
Abstract: We experimentally show how a single Ag nanoparticle (NP) coupled to an Ag nanowire (NW) can convert propagating surface plasmon polaritons to directional photons. By employing dual-excitation Fourier microscopy with spatially filtered collection-optics, we show single- and dual-directional out-coupling of light from NW-NP junction for plasmons excited through glass-substrate and air-superstrate. Furthermore, we show NW-NP junction can influence the directionality of molecular-fluorescence emission, thus functioning as an optical antenna. The results discussed herein may have implications in realizing directional single-photon sources and quantum plasmon circuitry.
17 citations
TL;DR: In this article, a Fourier optical fluorescence microscope was used to demonstrate how fluorescence emission from molecules in the vicinity of a chemically prepared silver nanowire-dimer-junction can be directed in one or two channels.
Abstract: The localized interaction between metallic nanostructures and surrounding fluorescent molecules can influence the emission characteristics of the molecule. With this hindsight, herein, by employing a Fourier optical fluorescence microscope, we experimentally show how fluorescence emission from molecules in the vicinity of a chemically prepared silver nanowire-dimer-junction can be directed in one or two channels. Measured forward-to-backward ratio of the fluorescence emission in a single channel was as high as 4.3 dB, and the observed polar and azimuthal angular spread was as narrow as 15° and 60°, respectively. Interestingly, the angle between the two emission channels mimicked the angle between the nanowires, thus, highlighting the prospect of geometrical control of the emitted light. These observations were further corroborated by three-dimensional finite-difference time-domain simulations. The presented results will have implications in momentum-space engineering of molecular fluorescence emission and...
16 citations
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TL;DR: The role of surface ligands in tuning and rationally designing properties of functional nanomaterials and their importance for biomedical and optoelectronic applications is focused on and an assessment of application-targeted surface engineering is concluded.
Abstract: All nanomaterials share a common feature of large surface-to-volume ratio, making their surfaces the dominant player in many physical and chemical processes. Surface ligands - molecules that bind to the surface - are an essential component of nanomaterial synthesis, processing and application. Understanding the structure and properties of nanoscale interfaces requires an intricate mix of concepts and techniques borrowed from surface science and coordination chemistry. Our Review elaborates these connections and discusses the bonding, electronic structure and chemical transformations at nanomaterial surfaces. We specifically focus on the role of surface ligands in tuning and rationally designing properties of functional nanomaterials. Given their importance for biomedical (imaging, diagnostics and therapeutics) and optoelectronic (light-emitting devices, transistors, solar cells) applications, we end with an assessment of application-targeted surface engineering.
1,247 citations
TL;DR: In this article, a review highlights the recent progress of the state-of-the-art research on synthesis, characterization and isolation of single and few layer nanosheets and their assembly.
1,090 citations
TL;DR: The perovskite solar cells (PSCs) have attracted much attention because of their rapid rise to 22% efficiencies as discussed by the authors, which could revolutionize the photovoltaic industry.
Abstract: Perovskite solar cells (PSCs) have attracted much attention because of their rapid rise to 22% efficiencies. Here, we review the rapid evolution of PSCs as they enter a new phase that could revolutionize the photovoltaic industry. In particular, we describe the properties that make perovskites so remarkable, and the current understanding of the PSC device physics, including the operation of state-of-the-art solar cells with efficiencies above 20%. The extraordinary progress of long-term stability is discussed and we provide an outlook on what the future of PSCs might soon bring the photovoltaic community. Some challenges remain in terms of reducing non-radiative recombination and increasing conductivity of the different device layers, and these will be discussed in depth in this review.
924 citations
TL;DR: In this article, the material characteristics that determine and influence the electrochemical potentials of electrodes are discussed, in particular the cathode materials that convert electricity and chemical potential through electrochemical intercalation reactions.
783 citations
TL;DR: A complete overview of the emerging field of networks beyond pairwise interactions, and focuses on novel emergent phenomena characterizing landmark dynamical processes, such as diffusion, spreading, synchronization and games, when extended beyond Pairwise interactions.
740 citations