Papers by Parameswar Iyer
Chemical science, 2024
An innovative design strategy of placing sulfur (S)-atoms within the pendant functional groups an... more An innovative design strategy of placing sulfur (S)-atoms within the pendant functional groups and at carbonyl positions in conventional perylenimide (PNI-O) has been demonstrated to investigate the condensed state structure-property relationship and potential photodynamic therapy (PDT) application. Incorporation of simply S-atoms at the peri-functionalized perylenimide (RPNI-O) leads to an aggregation-induced enhanced emission luminogen (AIEEgen), 2-hexyl-8-(thianthren-1-yl)-1H-benzo [5,10]anthra[2,1,9-def]isoquinoline-1,3(2H)-dione (API), which achieves a remarkable photoluminescence quantum yield (F PL) of 0.85 in aqueous environments and established novel AIE mechanisms. Additionally, substitution of the S-atom at the carbonyl position in RPNI-O leads to thioperylenimides (RPNI-S): 2-hexyl-8-phenyl-1H-benzo[5,10]anthra[2,1,9-def]isoquinoline-1,3(2H)-dithione (PPIS), 8-([2,2 0-bithiophen]-5-yl)-2-hexyl-1H-benzo[5,10]anthra[2,1,9-def]isoquinoline-1,3(2H)-dithione (THPIS), and 2-hexyl-8-(thianthren-1-yl)-1H-benzo[5,10]anthra[2,1,9-def]isoquinoline-1,3(2H)-dithion (APIS), with distinct photophysical properties (enlarged spin-orbit coupling (SOC) and F PL z 0.00), and developed diverse potent photosensitizers (PSs). The present work provides a novel SOC enhancement mechanism via pronounced H-aggregation. Surprisingly, the lowest singlet oxygen quantum yield (F D) and theoretical calculation suggest the specific type-I PDT for RPNI-S. Interestingly, RPNI-S efficiently produces superoxide (O 2 c −) due to its remarkably lower Gibbs free energy (DG) values (THPIS: −40.83 kcal mol −1). The non-toxic and heavy-atom free very specific thio-based PPIS and THPIS PSs showed selective and efficient PDT under normoxia, as a rare example.
RSC advances, 2024
Ambient stable solution processed n-channel organic field effect transistors (OFETs) are essentia... more Ambient stable solution processed n-channel organic field effect transistors (OFETs) are essential for nextgeneration low-cost organic electronic devices. Several molecular features, such as suitable orbital energy levels, easy synthetic steps, etc., must be considered while designing efficient active layer materials. Here, we report a case of improved ambient stability of solution-processed n-type OFETs upon suitable endgroups substitution of the active layer materials. A pair of core-substituted napthalenediimide (NDIFCN 2 and EHNDICN 2) derivatives with alkyl and perfluorinated end groups are considered. The transistor devices made out of these two derivatives exhibited largely different ambient stability behavior. The superior device stability (more than 25 days under ambient conditions) of one of the derivatives (NDIFCN 2) was ascribed to the presence of fluorinated end groups that function as hydrophobic guard units inhibiting moisture infiltration into the active layer, thereby achieving ambient stability under humid conditions (>65% relative atmospheric humidity). Molecular level optical and electrochemical properties, thermal stability, and the solution-processed (spin coat and drop cast active layers) device characteristics are described in detail. Our findings highlight the requirement of hydrophobic end groups or sidechains for ambient stability of active layer materials, along with deep LUMO levels for ambient stability.
Nature Communications, Oct 19, 2023
ACS Applied Materials & Interfaces
Chemical Solution Synthesis for Materials Design and Thin Film Device Applications
Abstract The robust and controllable sensitivity of thin film material and the outstanding stabil... more Abstract The robust and controllable sensitivity of thin film material and the outstanding stability of thin film make it an ideal choice for sensing applications. Analytes detected and analyzed ranging from detrimental gas molecules to biomolecules (nucleic acids, proteins) and diseases related biomarkers. This chapter outlines the working principle of chemiresisitive sensor, organic field effect transistor, and organic electrochemical transistor with special focus on the recent advances of thin film devices for chemical, biological, and therapeutic applications. Advantages of organic thin films, challenges related to thin film devices, and future opportunities for the development of high quality sensors are also discussed.
ACS Applied Energy Materials
IntechOpen eBooks, Dec 14, 2022
Perovskite has emerged as a promising light-harvesting material for solar cells due to its higher... more Perovskite has emerged as a promising light-harvesting material for solar cells due to its higher absorption coefficient, bandgap tunability, low-exciton binding energy, and long carrier diffusion length. These lead to high power conversion efficiency >25% for thin film-based perovskite solar cells (PSCs). Additionally, PSCs can be fabricated through simple and cost-effective solution processable techniques, which make this technology more advantageous over the current photovoltaic technologies. Several solution-processable methods have been developed for fabrication of PSCs. In this chapter, the advantages and disadvantages of various solution processable techniques and their scope for large-scale commercialization will be discussed.
Organic & Biomolecular Chemistry
FeCl3 mediated C–N coupling leads to an azaheterocycle, which undergoes one-electron reduction to... more FeCl3 mediated C–N coupling leads to an azaheterocycle, which undergoes one-electron reduction to form a fairly stable radical anion in situ. The azaheterocycle material showed balanced ambipolar charge transport in SCLC devices.
Advanced Nanomaterials for Point of Care Diagnosis and Therapy, 2022
ACS Applied Nano Materials, 2021
Progress in Molecular Biology and Translational Science, 2021
The concept of aggregation-induced emission (AIE) in purely organic luminescent molecules has dra... more The concept of aggregation-induced emission (AIE) in purely organic luminescent molecules has drawn wide attention in the last two decades. Despite the many challenges, AIE-probes have opened versatile opportunities in many research fields. In particular, the emerging functional properties of room temperature phosphorescence (RTP) and thermally activated delayed fluorescence (TADF) have boosted the unique features of AIE luminogens (AIEgens). Thus, these luminescent materials extended the utility in sensing, imaging, optoelectronics and theranostic applications in biological field over the conventional fluorescent probe. Unlike the sensitivity of triplet state by oxygen and moisture, the long-lived phosphorescence and delayed fluorescence resulting from the enhanced intersystem crossing (ISC) and reverse intersystem crossing (RISC) from excited triplet state (T1) to excited singlet state (S1) in these luminophores gives rise to long lifetimes ranging from nanoseconds to milliseconds even up to seconds. As compared to traditional fluorescence molecules advanced AIE probes show high contrast imaging and deeper penetration depth, which have been demonstrated through near infrared I and II (NIR-I & NIR-II) fluorescence imaging, room temperature after-glow imaging and photoacoustic imaging. This chapter highlights the recent developments and principle of the efficient design of AIE probe with multi-functional properties evolved with new strategies for translational applications via fluorescence imaging, photoacoustic imaging and image-guided photodynamic/photothermal therapy (PDT/PTT) including future opportunities for AIEgens to advance the overall biomedical field.
ACS Applied Polymer Materials, 2021
Advanced Sustainable Systems, 2020
Materials Research Express, 2020
In order to realize low-cost and efficient organic light-emitting diodes (OLEDs), the transparent... more In order to realize low-cost and efficient organic light-emitting diodes (OLEDs), the transparent anode should have excellent optical and electrical properties, among other factors. Typically, transparent conductive oxides have been widely used for transparent top electrodes, but they suffer from several drawbacks. We herein report the fabrication of efficient indium-free transparent OLEDs using metal-mesh based top electrodes, made of any metal of choice, Au, Ag or Cu. The fabricated devices on inch square substrates exhibited superior emission characteristics without any color shift. In terms of workfunction matching, Cu did the best. With a Cu-TCE of low sheet resistance (~7 Ω sq−1), uniform emission characteristics were achieved with relatively high current efficiency and luminance, comparable to those from the ITO based devices.
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Papers by Parameswar Iyer