Browsing by Author "Ghosh, Sarbani"

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Adsorption of hydrogen on single-walled carbon nanotubes with defects
(Elsevier, 2015-10) Ghosh, Sarbani
We present molecular dynamics (MD) simulations and density functional theory (DFT) calculations of hydrogen adsorption on single-walled carbon nanotubes (SWCNT) with various kinds of defects. The nature of defects, which is characterized here by the number of carbon atoms present in a ring on the surface of nanotube, plays a significant role in determining the hydrogen adsorption capacity of the SWCNT. Nanotubes containing the Stone–Wales defect with 5 and 8-member rings were found to have the largest hydrogen adsorption ability that increases further with the number of rings with such defects. Whereas, the presence of defects with 5, 3-5-8-member rings and the Stone–Wales defect with 5 and 7-member rings decreases the adsorption ability of the defective SWCNT significantly with respect to defect-free nanotubes. Our results indicate that the huge discrepancies in hydrogen storage capacities of SWCNT reported in the literature could be attributed to the nature of defects present in nanotubes. DFT calculations also reveal that the adsorption energy depends not only on the nature and number of defects present on the surface of nanotube but also on the equilibrium structure of rings.
Beryllium-doped single-walled carbon nanotubes with Stone-Wales defects: A promising material to store hydrogen at room temperature
(Elsevier, 2017-09) Ghosh, Sarbani
Hydrogen storage in single-walled carbon nanotubes containing the Stone-Wales defects and doped with metal atoms (titanium and beryllium) has been studied using molecular dynamics simulations and density functional theory calculations. Although, Be is known to be toxic at high temperatures, Be-doped SWCNT shows a promising potential to exceed the DOE target at moderate temperatures and pressures. One of the major advantages of doping Be is its lower atomic weight, which increases the gravimetric storage capacity compared to SWCNTs doped with heavy-wight Ti atoms. In addition, the binding energy of Be is higher than that of Ti, which enhances the capture of hydrogen molecules. The gravimetric and volumetric storage capacities depend not only on the dopant atom but also on the location of doping. SWCNTs in which Be is doped on the octagonal ring of the Stone-Wales defects exhibits higher storage capacity than Be doped on defect-free SWCNTs. At room temperature (298 K), the storage capacity of Be-doped SWCNT containing the Stone-Wales defect exceeds the DOE target of 5.5 wt% (gravimetric) and 40 g H2/L (volumetric) at a pressure of 267 atm, which is significantly lower than that used in high pressure vessels.
Combined electrochemical and dft investigations of znco2o4–wo3@ti3c2tx mxene nanofiber nanocomposite as a cathode for a high-performance flexible asymmetric supercapacitor
(ACS, 2025-08) Ghosh, Sarbani; Dalvi, Anshuman
Interfacial engineering offers an enticing approach to improving the charge-transfer kinetics in supercapacitor electrodes. Herein, a nanocomposite composed of WO3 nanoplates decorated on the surface of ZnCo2O4 (ZCO) nanopetals with the combination of Ti3C2Tx MXene nanofibers (MXNFs) was successfully prepared. This nanocomposite (ZCO–WO3@MXNF) exhibited superior electrochemical performance over its components. Density functional theory (DFT) calculations revealed the improvement of structural stability, charge-transfer efficiency, and electron mobility in the nanocomposite because of the presence of hybridized states throughout the composite and hence the enhancement of its electrochemical properties. The ZCO–WO3@MXNF was used as the positive electrode and MXene-rGOsp as the negative electrode to design the asymmetric supercapacitor (ASC) device. Notably, the fabricated solid-state ASC device offered the energy density of 16 Wh kg–1 at a power density of 204 W kg–1, with the remarkable stability of 93% specific capacitance retention even after ∼5000 charging–discharging cycles. Further, the study of the ZCO–WO3@MXNF//MXene-rGOsp ASC device in a pouch cell assembly was conducted. The pouch cell showed excellent performance, with an energy density of 28 Wh kg–1 and a power density of 578 W kg–1. The fabricated device showed its practical feasibility by lighting up the light-emitting diode (LED) lights. These results suggested its excellent electrochemical activity and its candidacy as a promising electrode material for energy storage devices.
Computational design of isomeric naphthalenediimide–naphthodithiophene (NDI–NDT) copolymers for organic electronics
(ACS, 2025-09) Garg, Mohit; Ghosh, Sarbani
This study presents a comprehensive investigation of conjugated donor–acceptor (D–A) copolymers based on naphthalenediimide (NDI) and two structural isomers of naphthodithiophene (NDT), i.e., linear (L-NDT) and angular (A-NDT), designated as NDI–L-NDT and NDI–A-NDT, respectively. By systematically analyzing their molecular structure, (opto)electronic properties, photovoltaic performance, morphological analysis, and mechanical stability, this study reveals the profound influence of donor isomerism on material properties, relevant to organic electronic applications. In particular, NDI–L-NDT exhibits a lower bandgap attributed to its extended donor π-conjugation and nearly coplanar D–A conformation compared to NDI–A-NDT. NDI–A-NDT demonstrates superior photovoltaic performance due to its higher power conversion efficiency compared to its linear counterpart. Morphological studies based on molecular dynamics simulations reveal that films of both copolymers exhibit similar levels of crystallinity. However, NDI–L-NDT possesses greater thermal stability and mechanical flexibility, capable of withstanding up to 100% strain without cracking, attributed to its dynamic conformational adaptability, making it a promising candidate for flexible electronic applications. This work reveals the potential of structural isomerism in fine-tuning D–A copolymers for multifunctional roles, as donors, acceptors, or single-component materials in next-generation organic electronic devices.
A computational study of cellulose regeneration: All-atom molecular dynamics simulations
(Elsevier, 2023-07) Ghosh, Sarbani
Processing natural cellulose requires its dissolution and regeneration. It is known that the crystallinity of regenerated cellulose does not match that of native cellulose, and the physical and mechanical properties of regenerated cellulose can vary dependent on the technique applied. In this paper, we performed all-atom molecular dynamics simulations attempting to simulate the regeneration of order in cellulose. Cellulose chains display an affinity to align with one another on the nanosecond scale; single chains quickly form clusters, and clusters then interact to form a larger unit, but the end results still lack that abundance of order. Where aggregation of cellulose chains occurs, there is some resemblance of the 1–10 surfaces found in Cellulose II, with certain indication of 110 surface formation. Concentration and simulation temperature show an increase of aggregation, yet it appears that time is the major factor in reclaiming the order of “crystalline” cellulose.
Controlling Electrochemically Induced Volume Changes in Conjugated Polymers by Chemical Design: from Theory to Devices
(Wiley, 2021-04) Ghosh, Sarbani
Electrochemically induced volume changes in organic mixed ionic-electronic conductors (OMIECs) are particularly important for their use in dynamic microfiltration systems, biomedical machinery, and electronic devices. Although significant advances have been made to maximize the dimensional changes that can be accomplished by OMIECs, there is currently limited understanding of how changes in their molecular structures impact their underpinning fundamental processes and their performance in electronic devices. Herein, a series of ethylene glycol functionalized conjugated polymers is synthesized, and their electromechanical properties are evaluated through a combined approach of experimental measurements and molecular dynamics simulations. As demonstrated, alterations in the molecular structure of OMIECs impact numerous processes occurring during their electrochemical swelling, with sidechain length shortening decreasing the number of incorporated water molecules, reducing the generated void volumes and promoting the OMIECs to undergo different phase transitions. Ultimately, the impact of these combined molecular processes is assessed in organic electrochemical transistors, revealing that careful balancing of these phenomena is required to maximize device performance.
Effect of Substrate on Structural Phase Transition in a Conducting Polymer during Ion Injection and Water Intake: A View from a Computational Microscope
(ACS, 2020-12) Ghosh, Sarbani
Conducting polymers operating in aqueous electrolyte represent mixed electron-ion conductors, where the ion injection and water intake can lead to structural and morphological changes that can strongly affect the material morphology and device performance. In the present paper, using molecular dynamics simulations, we provide an atomistic understanding of the structural phase transitions during electrochemical oxidation and ion injection in a conjugated polymer with glycolated side chains recently reported by Bischak et al. [J. Am. Chem. Soc., 2020, 142, 7434], where the polymer switched between two structurally distinct phases corresponding to different oxidation levels. To outline the structural changes, we calculated the polymer film morphology and X-ray diffraction patterns at different oxidation levels. We demonstrated that the observed phase transition arises due to interplay between several factors, including the effect of the substrate leading to the preferential edge-on arrangement of the chains and formation of lamellas; unzipping of the interdigitated polymer chains during oxidation and ion intake; and changes in the morphology when π–π stacking is absent at low oxidation level and forms at the high oxidation level facilitating the electron mobility and enabling the oxidation of the polymer film. Our calculations quantitatively reproduce the experimental data, which outlines the predictive power of the molecular modeling of the polymer systems that can be utilized for the design of materials and devices with improved performance.
Electrochemical doping for absorption and conductivity tuning of p(NDI2OD-T2) films
(ACS, 2025-04) Ghosh, Sarbani
Electrochemical doping of thin films of poly{[N,N′-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5′-(2,2′-bithiophene)} (P(NDI2OD-T2)) is shown as straightforward method to achieve different degrees of doping both during in situ electrochemical experiments as well as in the solid state. Results obtained from cyclic voltammetry and absorption spectroscopy upon reduction can be explained by the presence of the neutral state as well as polaron and bipolaron species, including neutral/polaron and polaron/bipolaron mixed valence states. The UV-vis-NIR spectra are analyzed and explained based on the calculated electronic structure and the corresponding transitions between different states, this includes features such as numbers and positions of the peaks and their evolution during reduction. Most intruingly, doped films are stable after transfer in the solid state, as evidenced by absorption spectroscopy. Conductivity measurements of films with different degrees of doping show a bell-shaped conductivity profile, which underlines the classification of P(NDI2OD-T2) as a conjugated redox polymer with mixed valence transport. Maximum conductivities of up to 2 × 10−4 S cm−1 are obtained at intermediate doping levels under the coexistence of neutral state and polarons. Conductivity measurements of blade-coated films point to anisotropic charge transport with the highest charge transport along the blade /polymer chain direction and an anisotropic conductivity ratio of 4.1.
Electronic structure, optical properties, morphology and charge transport in naphthalenediimide (NDI)-based n-type copolymer with altered π-conjugation: A theoretical perspective
(AIP, 2021-06) Ghosh, Sarbani
Future developments of the thermoelectric technologies based on conducting polymer require to find n-type polymers with performance, especially electrical conductivity, comparable to the one of the state-of-the-art p-type conducting polymers. In this regard, naphthalenediimide based donor–acceptor copolymers have appeared as promising candidates. The backbone of the polymer can be engineered to control the electronic structure and the morphology of the chains in order to maximize both the charge carrier density and mobility. However, at the moment a complete theoretical insight from electronic structures to charge transport is missing. Here, we use a multiscale theoretical framework to study naphthalenediimide based donor–acceptor copolymers where the donor π-conjugated dithienylvinylene moieties are replaced by π non-conjugated dithienylethane in various amounts, and we show that this approach is in position to rationalize many experimental data. The resulting gradual change in electronic structure of polymer chains is investigated by the density functional theory and correlated with experimental absorption spectra. The morphology of a polymer film is studied by means of molecular dynamics simulations, showing that an extended network of inter-chain π–π stacking is preserved upon introduction of non-conjugated units in the polymer backbone. This finding is supported by a subsequent calculation of the charge transport, which shows only a moderate impact of the morphology on the mobility, while the experimental data can be retrieved by considering the effect of the π non-conjugated moiety on the electronic structure. Such a multiscale description of conducting polymers paves the way toward fully theoretical design of future high performances materials
Electronic Structures and Optical Absorption of N-Type Conducting Polymers at Different Doping Levels
(ACS, 2019-06) Ghosh, Sarbani
Theoretical understanding of the electronic structure and optical transitions in n-doped conducting polymers is still controversial for polaronic and bipolaronic states and is completely missing for the case of a high doping level. In the present paper, the electronic structure and optical properties of the archetypical n-doped conducting polymer, double-stranded benzimidazo-benzophenanthroline ladder (BBL), are studied using the density functional theory (DFT) and the time-dependent DFT method. We find that a polaronic state in the BBL chain is a spin-resolved doublet where the spin degeneracy is lifted. The ground state of two electrons corresponds to a triplet polaron pair, which is in stark contrast to a commonly accepted picture where two electrons are postulated to form a spinless bipolaron. The total spin gradually increases until the reduction level reaches cred = 100% (i.e., one electron per monomer unit). With further increase of the reduction level, the total spin decreases until it becomes 0 for the reduction level cred = 200%. The calculated results reproduce the experimentally observed spin signal without any phenomenological parameters. A detailed analysis of the evolution of the electronic structure of BBL and its absorption spectra with increase in reduction level is presented. The calculated UV–vis–NIR spectra are compared with the available experimental results. The electronic structure and optical absorption for different reduction levels presented here are generic to a wide class of conducting polymers, which is illustrated by the corresponding calculations for another archetypical conducting polymer, poly(3,4-ethylenedioxythiophene) (best known as PEDOT).
Electronic Structures and Optical Properties of p-Type/n-Type Polymer Blends: Density Functional Theory Study
(ACS, 2020-04) Ghosh, Sarbani
A blend made of p-type and n-type polymers can act as bipolar/ambipolar material composites that transport both electrons and holes. Although several experimental efforts are currently devoted to p-/n-type blends of conducting polymers, theoretical studies of these systems are missing to a large extent. In the current paper, using the density functional theory (DFT) and the time-dependent DFT, we calculate electronic and optical properties of a p-type/n-type polymeric blend, where we have chosen the poly(3,4-ethylenedioxythiophene)/benzimidazo-benzophenanthroline ladder (PEDOT/BBL) as a model composite system. We demonstrate that in the blend, PEDOT acts as an electron donor and BBL acts as an electron acceptor under doped conditions. However, no charge transfer between the chains takes place for an undoped composite system. Due to a significant difference in the electron affinities and the ionization energies of PEDOT and BBL, the electronic properties of a negatively (positively) doped PEDOT/BBL blend are primarily governed by the chains where negative (positive) charges are localized, i.e., the BBL chains (the PEDOT chains). However, this is no longer valid for the optical absorption where the electronic transition occurs between the two chains and, therefore, the calculated UV–vis–near-infrared (NIR) absorption spectra of the negatively (positively) doped PEDOT/BBL blend are rather different compared to the corresponding spectra of the single BBL chains (PEDOT chains). The electronic coupling between the photoexcited state and the final charge-transfer state of the blend was calculated to be ∼0.08 eV. The results presented here are generic to a wide class of p-type/n-type combinations, which was further confirmed by calculations performed on the polythiophene (PT)/BBL blend
Experimental and Theoretical Investigation into the Polaron Structure of K-Doped Polyfluorene Films
(ACS, 2020-12) Ghosh, Sarbani
The evolution of the electronic structure and optical transition upon n-doping of poly(9,9-dioctylfluorene) (PFO) films is elucidated with photoelectron spectroscopy, optical absorption, density functional theory (DFT), and time-dependent DFT (TD-DFT) calculations. Optical absorption measurements extending into near infrared show two low-energy absorption features at low doping ratios and an additional peak at a higher energy of ∼2.2 eV that disappears with increasing doping ratios. A gap state (i.e., polaronic state) close to the Fermi level and a significantly destabilized highest valence band appear in the experimentally measured ultraviolet photoelectron spectra. These experimental results are interpreted by the TD-DFT calculations, which show that the lower energy peaks originate from the excitation from polaronic states to the conduction band, while the higher energy peak mainly originates from the destabilized valence band to conduction band transitions and only appears at low doping ratios (cred ≤ 50%, 0.5 potassium atom per fluorene monomer). The DFT calculations further indicate that polaron pairs rather than bipolarons are preferentially formed at high doping ratios. Comparing the results of doped glassy and β-phase films, we find that the ordered segments in the β-phase film disappear due to the dopant (potassium) insertion, resulting in a similar polaronic structure.
Exploring an N-Type Conducting Polymer (BBL) as a Potential Gas Sensing Material for NH3 and H2S Detection: A Theoretical Study
(2024) Hazra, Arnab; Garg, Mohit; Ghosh, Sarbani
Conducting polymers (CPs) have garnered significant interest in being used as an active material in gas sensors mainly because of their structural flexibility, ease of synthesis, and enhanced performance at room temperature. The p-type CPs and their composites are mostly studied in gas sensing, which, unfortunately, exhibit limitations in terms of selectivity, stability, and sensitivity toward reducing gases. This study focuses on one of the widely studied n-type polymers, BBL(benzimidazobenzophenanthroline), as an active material for the detection of two reducing gases, namely, ammonia (NH3)and hydrogen sulfide (H2S), theoretically. Through molecular dynamics (MD) simulation and density functional theory (DFT)approach, we understand the adsorption behavior and selectivity of NH3 and H2S in the BBL film. Our results show that BBL displays remarkable adsorption for ammonia gas compared to hydrogen sulfide gas without compromising the π − π stacked crystallites within the polymer film. The DFT calculations show the adsorption energy of -0.32 eV and -0.21 eV for NH3 and H2S, respectively. MD simulations show that adsorption takes place in the free voids within the thin films, helping the polymer films to maintain their crystallinity, which indicates, upon detection of reducing gases, the generated free electrons will be able to be smoothly transported through the π − π stack network. The detailed theoretical insights obtained from this study indicate the suitability of the n-type conducting polymer, BBL, for the detection of reducing gases.
Hydrogen adsorption in pyridine bridged porphyrin-covalent organic framework
(Elsevier, 2019) Ghosh, Sarbani
Covalent organic frameworks (COFs), a class of carbon-based polymeric materials have the potential to be used as hydrogen adsorbent. Three dimensional (3D) COFs, due to their low density and high surface area, although have higher hydrogen adsorption, they have less stability than two dimensional (2D) COFs. Here we studied porphyrin group containing 2D COF, namely H2,P-COF for hydrogen storage using density functional theory (DFT) and grand canonical Monte Carlo (GCMC) simulations and the results were compared with the most common 2D COFs, COF-1 and COF-5. Cylindrical shaped 2D COFs where isolated unit blocks are stacked in multiple layers due to van der Waals interactions between individual layers, increase the effective surface area for hydrogen storage. A further modification has been done by bridging the inter-layer gap by pyridine molecules. Insertion of pyridine increases the separation distance of layers of 2D COFs as well as the free volume. Feasibility of the structure formation and stability of all the structures were checked using DFT study. To ensure the structural stability of bridged COFs after hydrogen loading, alternating layers of COF were bridged. Single, bi, tri and tetra -pyridine molecules were chemically bonded with the existing carbon ring present in between two C2O2B rings to form pyridine bridged H2,P-COFs. Our GCMC results show a significant increase in storage capacity which is mainly due to an increase in the free volume of the material. The highest capacity of 5.1 wt% and 20 g H2/L at 298 K and 100 bar, above the gravimetric DOE goal, has been found at room temperature for tetra-pyridine doped porphyrin COF structure.
Hydrogen storage capacity of bundles of single-walled carbon nanotubes with defects
(Wiley, 2016) Ghosh, Sarbani
We study the hydrogen storage capacity of bundles of single-walled carbon nanotubes (SWCNT) at 80 and 298 K using molecular dynamics simulations. The effect of packing on the storage capacity of the bundles is studied using triangular and square arrays of nanotubes with various separation distance between adjacent nanotubes. The gravimetric storage capacity of the bundles increases with the separation distance between individual nanotubes. At low temperature, the storage capacity of bundles is significantly lower than for isolated SWCNT as the intertube distance is smaller than the adsorbed layer thickness of hydrogen. At high temperature, the adsorbed layer thickness corresponds to only a monolayer of hydrogen around SWCNTs, and hence, hydrogen is captured in the interstitial spaces within the bundle. As the groove volume in the square array is higher than that in the triangular array, the storage capacity of the bundle with square array is higher. An introduction of the Stone–Wales defects on the surface of nanotubes further increases the storage capacity of the bundle due to the higher binding energy of the 8-member rings of the defective SWCNTs. We also observe that more hydrogen molecules are packed in the interstitial spaces due to the deformation of the nanotubes caused by the presence of defective sites
Hydrogen storage in Titanium-doped single-walled carbon nanotubes with Stone-Wales defects
(Elsevier, 2017) Ghosh, Sarbani
The hydrogen storage capacity of Titanium-doped single-walled carbon nanotubes (SWCNT) containing the Stone-Wales 5,8 defects was studied using molecular dynamics simulations. The equilibrium doping sites and their stability were estimated using density functional theory. Although introduction of structural defects and dopant atom decreases the formation and cohesive energies, the drop in these energies is not large enough to hinder the thermodynamic feasibility of formation of these structures. Moreover, we observed that the stability of SWCNTs, where Ti is doped by replacing two carbon atoms is similar to that of the defect-free nanotube. This particular novel configuration (D5) was also obtained by rearranging the bonds in the 5 and 8-member rings of the Stone-Wales defect. Doping Ti on the defective rings has a more significant effect on the adsorption of hydrogen than doping on the regular 6-member rings. The D5 SWCNT showed the highest gravimetric and volumetric storage capacities at a temperature of 298K and a moderate pressure of 140atm. We also compared the performance of the D5 SWCNT with a recently reported Ti-doped porphyrin SWCNT and observed that the storage capacity of the D5 SWCNT was significantly higher at similar conditions. Our results suggest that Ti-doped SWCNTs with the Stone-Wales (5,8) defects show a promising potential to meet the ultimate goal set by the US Department of Energy for hydrogen storage.
Hydrogen storage using novel graphene-carbon nanotube hybrid
(Elsevier, 2023) Ghosh, Sarbani
Hydrogen storage is an active area of research particularly due to urgent requirements for green energy technologies. In this paper, we study the storage of hydrogen gas molecules in terms of physical adsorption on a carbon-based nanomaterial, i.e., a novel graphene-carbon nanotube hybrid. The novel carbon nanostructures were prepared from pristine nanotubes and graphene sheets using molecular dynamics simulations and hydrogen storage quantified in terms of gravimetric capacity was simulated using grand canonical Monte Carlo Simulations. We found the highest storage capacity of 5.90 wt% at room temperature and 100 bar with high reversibility of operation
Improving morphology of P3HT:PCBM bulk heterojunction solar cells with anisotropic shaped silica nanoparticles
(Elsevier, 2023) Ghosh, Sarbani; Garg, Mohit
Using coarse-grained molecular dynamics simulations we study blends of Poly(3-hexylthiophene-2,5-diyl) (P3HT), [6,6]-Phenyl-C61-butyric acid methyl ester (PCBM) and Silica nanoparticle (SiNP) to understand the effect of adding SiNP on morphology of P3HT:PCBM in Bulk heterojunction (BHJ) solar cells. We use an approximately 3 nm anisotropic shaped SiNP and predicted the morphology of BHJ upon its incorporation. The SiNP arrange themselves into anisotropic structures depending on the concentration of P3HT, PCBM and SiNP respectively creating a network like morphology. PCBM molecules utilize the surface energy of SiNP and gather at its surface forming a morphology which is beneficial for device efficiency. Our results suggest that an optimum weight fraction of all the three components leads to higher surface area of contact, optimum domain size and high percolation of domains throughout the system. The effective control of all the morphological parameters help in improving the charge generation, extraction and transport to electrodes, thereby improving the performance of BHJ solar cells.
Mechanical, Morphological, and Charge Transport Properties of NDI Polymers with Variable Built-in Π-Conjugation Lengths Probed by Simulation and Experiment
(Wiley, 2023-10) Ghosh, Sarbani
Mechanically deformable polymeric semiconductors are a key material for fabricating flexible organic thin-film transistors (FOTFTs)—the building block of electronic circuits and wearable electronic devices. However, for many π-conjugated polymers achieving mechanical deformability and efficient charge transport remains challenging. Here the effects of polymer backbone bending stiffness and film microstructure on mechanical flexibility and charge transport are investigated via experimental and computational methods for a series of electron-transporting naphthalene diimide (NDI) polymers having differing extents of π-conjugation. The results show that replacing increasing amounts of the π-conjugated comonomer dithienylvinylene (TVT) with the π-nonconjugated comonomer dithienylethane (TET) in the backbone of the fully π-conjugated polymeric semiconductor, PNDI-TVT100 (yielding polymeric series PNDI-TVTx, 100 ≥ x ≥ 0), lowers backbone rigidity, degree of texturing, and π–π stacking interactions between NDI moieties. Importantly, this comonomer substitution increases the mechanical robustness of PNDI-TVTx while retaining efficient charge transport. Thus, reducing the TVT content of PNDI-TVTx suppresses film crack formation and dramatically stabilizes the field-effect electron mobility upon bending (e.g., 2 mm over 2000 bending cycles). This work provides a route to tune π–π stacking in π-conjugated polymers while simultaneously promoting mechanical flexibility and retaining good carrier mobility in FOTFTs.
Moisture uptake in nanocellulose: the effects of relative humidity, temperature and degree of crystallinity
(Institute for Metals Superplasticity Problems, 2021-08) Garg, Mohit; Ghosh, Sarbani
Hydrogen has the potential to be an alternative source of energy. However, most of the research on hydrogen storage carried out in the past is based on low temperature (<80 K) whereas storage near room temperature is desired. Here, we report room-temperature hydrogen storage capacity of defective single-walled carbon nanotubes (SWCNT) investigated using molecular dynamics simulations and density functional theory. Four different types of defective SWCNTs are considered to study room temperature hydrogen storage. We observed maximum adsorption capacity of SWCNT with 5 and 8-membered ring defects, namely, D1. The SWCNT with other three defects studied here, Stone-Wales with 5- and 7-membered ring defect (D2), 5-membered ring defect (D3), and 3-, 5- and 8-membered ring defect (D4) have negative adsorption effect compared to the defect-free SWCNT. The highest gravimetric capacity of 1.82 wt.% is found for the D1 defective SWCNT at room temperature, 298 K and 140 atm. The DFT calculations show that hydrogen adsorption strongly depends on the type of defect where the 8-membered ring has the highest adsorption energy and the 3-membered ring has the lowest adsorption energy. A combination of 5- and 8-membered defective rings can increase hydrogen adsorption significantly even at room temperature.