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Parameswar Krishnan Iyer

Bio: Parameswar Krishnan Iyer is an academic researcher from Indian Institute of Technology Guwahati. The author has contributed to research in topics: Materials science & Perovskite (structure). The author has an hindex of 35, co-authored 202 publications receiving 4540 citations. Previous affiliations of Parameswar Krishnan Iyer include Sardar Patel University & Case Western Reserve University.


Papers
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Journal ArticleDOI
TL;DR: In this paper, the photoluminescence (PL) and electroluminescent (EL) of polyfluorene (PF)-based light-emitting diodes (LEDs) were studied and it was shown that the low-energy emission band originates from fluorenone defects which are introduced by photo-oxidization, thermal oxidation, or during device fabrication.
Abstract: Polyfluorene (PF)-based light-emitting diodes (LEDs) typically exhibit device degradation under operation with the emergence of a strong low-energy emission band (at ∼ 2.2–2.4 eV). This longer wavelength band converts the desired blue emission to blue–green or even yellow. We have studied both the photoluminescence (PL) and electroluminescence (EL) of PFs with different molecular structures and found that the low-energy emission band originates from fluorenone defects which are introduced by photo-oxidization, thermal oxidation, or during device fabrication. X-ray photo-emission spectroscopy (XPS) results show that the oxidation of PF is strongly catalyzed by the presence of calcium. The fluorenone defects generate a stronger contribution to the EL than to the PL. By utilization of a novel electron-transporting material as a buffer layer between the emissive PF and the Ca/Ag (Ba/Ag) cathode, the blue EL emission from the PF was stabilized.

327 citations

Journal ArticleDOI
TL;DR: This comprehensive review surveys the up-to-date development of aggregation- induced emission/aggregation-induced emission enhancement (AIE/AIEE) active naphthalimide (NI)-based smart materials with potential for wide and real-world applications and that serves as a highly versatile building block with tunable absorption and emission in the complete visible region.
Abstract: This comprehensive review surveys the up-to-date development of aggregation-induced emission/aggregation-induced emission enhancement (AIE/AIEE) active naphthalimide (NI)-based smart materials with potential for wide and real-world applications and that serves as a highly versatile building block with tunable absorption and emission in the complete visible region. The review article commences with a precise description of the importance of NI moiety and its several restricted area of applications owing to its aggregation caused quenching (ACQ) properties, followed by the discovery and importance of AIE/AIEE-active NIs. The introduction section tracked an overview of the state of the art in NI luminogens in multiple applications. It also includes a few mechanistic studies on the structure–property correlation of NIs and provides more insights into the condensed-state photophysical properties of small aggregation-prone systems. The review aims to ultimately accomplish current and forthcoming views comprisin...

199 citations

Journal ArticleDOI
TL;DR: In this paper, the diameter dependent spectral features in X-ray diffraction (XRD) and Raman scattering studies of multiwalled carbon nanotubes (MWCNTs) of various diameters in the range 5−100nm were analyzed.

167 citations

Journal ArticleDOI
TL;DR: In this article, a new polyfluorene derivative, poly[4,4′-(((2-phenyl-9H-fluororene-9,9-diyl)bis(hexane-6,1-dyl))bis(oxy))dianiline)] (PFAM) was synthesized via the Suzuki coupling polymerization method in high yields for the rapid and specific recognition of nitroexplosive picric acid (PA) at 22.9 picogram level on solid support using paper strips and at 13.2 pp
Abstract: A new polyfluorene derivative, poly[4,4′-(((2-phenyl-9H-fluorene-9,9-diyl)bis(hexane-6,1-diyl))bis(oxy))dianiline)] (PFAM) was synthesized via the Suzuki coupling polymerization method in high yields for the rapid and specific recognition of nitroexplosive picric acid (PA) at 22.9 picogram level on solid support using paper strips and at 13.2 ppb level in aqueous solution. The polymer PFAM was well-characterized by means of NMR, UV–vis, fluorescence, time-resolved photoluminescence (TRPL) spectroscopy and cyclic voltammetry. The amplified signal response exclusively for PA was achieved via a strong inner filter effect (IFE), a phenomenon different from the widely reported ground-state charge transfer and/or Forster resonance energy transfer (FRET) based probes for nitroaromatics detection. Pendant amine groups attached on the side chains of PFAM provide enhanced sensitivity and exceptional selectivity via protonation assisted photoinduced electron transfer (PET) even in the presence of most common interfe...

137 citations


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08 Dec 2001-BMJ
TL;DR: There is, I think, something ethereal about i —the square root of minus one, which seems an odd beast at that time—an intruder hovering on the edge of reality.
Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

33,785 citations

01 Jan 2016
TL;DR: The principles of fluorescence spectroscopy is universally compatible with any devices to read and is available in the digital library an online access to it is set as public so you can download it instantly.
Abstract: Thank you very much for downloading principles of fluorescence spectroscopy. As you may know, people have look hundreds times for their favorite novels like this principles of fluorescence spectroscopy, but end up in malicious downloads. Rather than reading a good book with a cup of tea in the afternoon, instead they cope with some harmful bugs inside their desktop computer. principles of fluorescence spectroscopy is available in our digital library an online access to it is set as public so you can download it instantly. Our digital library spans in multiple locations, allowing you to get the most less latency time to download any of our books like this one. Kindly say, the principles of fluorescence spectroscopy is universally compatible with any devices to read.

2,960 citations

Journal ArticleDOI
TL;DR: School of Chemistry, Bio21 Institute, University of Melbourne, 30 Flemington Road, Victoria 3010, Australia; School of Materials Science and Engineering, Nanyang Technological University, Nastyang Avenue, Republic of Singapore 639798; Institute of Materials Research and Engineering (IMRE) and the Agency for Science, Technology and Research (A*STAR), 3 Research Link, Singapore 117602.
Abstract: A review was presented to demonstrate a historical description of the synthesis of light-emitting conjugated polymers for applications in electroluminescent devices. Electroluminescence (EL) was first reported in poly(para-phenylene vinylene) (PPV) in 1990 and researchers continued to make significant efforts to develop conjugated materials as the active units in light-emitting devices (LED) to be used in display applications. Conjugated oligomers were used as luminescent materials and as models for conjugated polymers in the review. Oligomers were used to demonstrate a structure and property relationship to determine a key polymer property or to demonstrate a technique that was to be applied to polymers. The review focused on demonstrating the way polymer structures were made and the way their properties were controlled by intelligent and rational and synthetic design.

2,378 citations

Journal ArticleDOI
20 Apr 2012-Science
TL;DR: It is shown that surface modifiers based on polymers containing simple aliphatic amine groups substantially reduce the work function of conductors including metals, transparent conductive metal oxides, conducting polymers, and graphene.
Abstract: Organic and printed electronics technologies require conductors with a work function that is sufficiently low to facilitate the transport of electrons in and out of various optoelectronic devices. We show that surface modifiers based on polymers containing simple aliphatic amine groups substantially reduce the work function of conductors including metals, transparent conductive metal oxides, conducting polymers, and graphene. The reduction arises from physisorption of the neutral polymer, which turns the modified conductors into efficient electron-selective electrodes in organic optoelectronic devices. These polymer surface modifiers are processed in air from solution, providing an appealing alternative to chemically reactive low–work function metals. Their use can pave the way to simplified manufacturing of low-cost and large-area organic electronic technologies.

1,870 citations