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Himanshu Chakraborty

Temple University, Institute for Computational Molecular Science, Post-Doc

Indian Institute of Technology Bombay, Physics, Graduate Student

Jawaharlal Nehru Centre for Advanced Scientific Research, Theoretical Sciences Unit, Post-Doc

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I am a member of Early Career Investigator Committee for Energy Frontier Research Center, and a postdoctoral fellow at the Institute of Computational Molecular Science, Temple University, US. Working towards the computational design of functional layered materials such as graphene nanostructures, layered metal-dichalcogenides, layered Borocarbonitrides, bulk and thin films of charge-transfer complexes etc.My research interests include computational material science, electronic structure calculations of such layered materials.Also, I am actively collaborating with various experimental and theoretical research groups around the world in the field of generation of clean fuel technology, e.g. understanding catalysis on the layered and two-dimensional materials such as borocarbonitrides , MoS2 etc. for hydrogen gas production
Supervisors: Prof. Michael L .Klein, Prof. C.N.R. Rao, Prof. Umesh V. Waghmare, and Prof. Alok Shukla
Phone: +1-484-274-0212
Address: 1925 N 12th St. SERC 701 E,
Temple University
Philadelphia, PA 19122

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Vivek Kumar Yadav

Temple University

Natasha Yamamoto

Takashi Karatsu

Akram Hosseinian

Надежда Небогатикова

Jessica Julieth Castro

Université de Montréal

Marutheeswaran Srinivasan

Indian Institute of Science

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Papers by Himanshu Chakraborty

Light-induced dilation in nanosheets of charge-transfer complexes

Proceedings of the National Academy of Sciences

We report the observation of a sizable photostrictive effect of 5.7% with fast, submillisecond re... more We report the observation of a sizable photostrictive effect of 5.7% with fast, submillisecond response times, arising from a light-induced lattice dilation of a molecular nanosheet, composed of the molecular charge-transfer compound dibenzotetrathiafulvalene (DBTTF) and C60. An interfacial self-assembly approach is introduced for the thickness-controlled growth of the thin films. From photoabsorption measurements, molecular simulations, and electronic structure calculations, we suggest that photostriction within these films arises from a transformation in the molecular structure of constituent molecules upon photoinduced charge transfer, as well as the accommodation of free charge carriers within the material. Additionally, we find that the photostrictive properties of the nanosheets are thickness-dependent, a phenomenon that we suggest arises from surface-induced conformational disorder in the molecular components of the film. Moreover, because of the molecular structure in the fi...

Effect of Intercalated Metals on the Electrocatalytic Activity of 1T-MoS 2 for the Hydrogen Evolution Reaction

by Himanshu Chakraborty, Nuwan Attanayake, and John Perdew

We show that intercalation of cations (Na + , Ca 2+ , Ni 2+ , and Co 2+) into the interlayer regi... more We show that intercalation of cations (Na + , Ca 2+ , Ni 2+ , and Co 2+) into the interlayer region of 1T-MoS 2 is an effective strategy to lower the overpotential for the hydrogen evolution reaction (HER). In acidic media the onset potential for 1T-MoS 2 with intercalated ions is lowered by ∼60 mV relative to that for pristine 1T-MoS 2 (onset of ∼180 mV). Density functional theory (DFT) calculations show a lowering in the Gibbs free energy for H-adsorption (ΔG H) on these intercalated structures relative to intercalant-free 1T-MoS 2. The DFT calculations suggest that Na + intercalation results in a ΔG H close to zero. Consistent with calculation, experiments show that the intercalation of Na + ions into the interlayer region of 1T-MoS 2 results in the lowest overpotential for the HER.

Tunable two-dimensional interfacial coupling in molecular heterostructures

by Himanshu Chakraborty and Vivek Kumar Yadav

Two-dimensional van der Waals heterostructures are of considerable interest for the next generati... more Two-dimensional van der Waals heterostructures are of considerable interest for the next generation nanoelectronics because of their unique interlayer coupling and optoelectronic properties. Here, we report a modified Langmuir–Blodgett method to organize two-dimensional molecular charge transfer crystals into arbitrarily and vertically stacked het-erostructures, consisting of bis(ethylenedithio)tetrathiafulvalene (BEDT–TTF)/C 60 and poly (3-dodecylthiophene-2,5-diyl) (P3DDT)/C 60 nanosheets. A strong and anisotropic interfacial coupling between the charge transfer pairs is demonstrated. The van der Waals hetero-structures exhibit pressure dependent sensitivity with a high piezoresistance coefficient of −4.4 × 10 −6 Pa −1 , and conductance and capacitance tunable by external stimuli (ferroelectric field and magnetic field). Density functional theory calculations confirm charge transfer between the n-orbitals of the S atoms in BEDT–TTF of the BEDT–TTF/C 60 layer and the π* orbitals of C atoms in C 60 of the P3DDT/C 60 layer contribute to the inter-complex CT. The two-dimensional molecular van der Waals heterostructures with tunable optical–electronic–magnetic coupling properties are promising for flexible electronic applications.

A Free-Standing Molecular Spin–Charge Converter for Ubiquitous Magnetic-Energy Harvesting and Sensing

Self-powered organic conjugated materials are of vital impor- tance for the development of next-g... more Self-powered organic conjugated materials are of vital impor-
tance for the development of next-generation, flexible, and fully
integrated energy, sensing, and artificial-intelligence technolo-
gies. Due to their exceptionally long spin lifetimes and strong
spin–charge interactions, these carbon materials could also
impact data transmission, processing, and storage. However, to
exploit these opportunities, the ability to directly convert energy
from spin information to electric charge is essential. Here,
we introduce a novel molecular spin–charge converter that is
comprised of a centimeter-sized free-standing organic charge-
transfer crystal. Magnetic-field effects in this material induce
intersystem crossings and spin–charge-lattice couplings that
generate an electric voltage for magnetic-energy harvesting.
The effective conversion between charge and spin stimulus
permits simultaneous and instantaneous self-powering and
sensing performance in a molecular crystal that displays ani-
sotropic behavior dependent on crystal orientation. We con-
firm the strong charge-transfer character of the crystals with
first principle calculations of the electronic density of states.
The solution processed flexible devices also exhibit an excellent
temperature sensitivity of <0.01 K and a unique piezoresistance
coefficient of −5.1 × 10 −6 Pa −1 . The self-powered sensing perfor-
mance of this molecular spin–charge converter, together with
its solution processability and flexibility, endow this molecular
charge-transfer crystal with the capability to drive a new gen-
eration of noncontact magnetic-energy harvesting and sensing
technologies.

Superior performance of borocarbonitrides, B x C y N z , as stable, low-cost metal-free electrocatalysts for hydrogen evolution reaction

Energy Environ. Sci., 2015

We report superior hydrogen evolution activity of metal-free borocarbonitride (BCN) catalysts. Th... more We report superior hydrogen evolution activity of metal-free borocarbonitride (BCN) catalysts. The highly positive onset potential (À56 mV vs. RHE) and the current density of 10 mA cm À2 at an overpotential of 70 mV exhibited by a carbon-rich BCN with the composition BC 7 N 2 demonstrates the extraordinary electrocatalytic activity at par with Pt. Theoretical studies throw light on the cause of high activity of this composition. The high activity and good stability of BCNs surpass the characteristics of other metal-free catalysts reported in recent literature.

Large scale configuration interaction calculations of linear optical absorption of octacene and nonacene

by Himanshu Chakraborty and Alok Shukla

ABSTRACT The technological importance of higher acenes has led to resurgence of interest in synth... more ABSTRACT The technological importance of higher acenes has led to resurgence of interest in synthesizing higher acenes such as octacene, nonacene etc.[1] Recently, Tonshoff and Bettinger have synthesized octacene and nonacene [2]. Motivated by their work, we have performed large scale calculations of linear optical absorption of octacene and nonacene and compared the results with their experimental work. Methodology adopted in our work is based upon Pariser-Parr-Pople model (PPP) Hamiltonian, along with large-scale multi-reference singles-doubles configuration interaction (MRSDCI) approach.

Large scale configuration interaction calculations of linear optical absorption of decacene

ABSTRACT The technological importance of higher acenes has led to resurgence of interest in synth... more ABSTRACT The technological importance of higher acenes has led to resurgence of interest in synthesizing them e.g. octacene, nonacene and decacene [1]. Recently, Tönshoff and Bettinger have synthesized octacene and nonacene [2]. Motivated by their work, we have performed large scale calculations of linear optical absorption of decacene. Methodology adopted in our work is based upon Pariser-Parr-Pople model (PPP) Hamiltonian, along with largescale multi-reference singles-doubles configuration interaction (MRSDCI) approach.

Theory of triplet optical absorption in oligoacenes: From naphthalene to heptacene

by Himanshu Chakraborty and Alok Shukla

The Journal of Chemical Physics, 2014

In this paper we present a detailed theory of the triplet states of oligoacenes containing up to ... more In this paper we present a detailed theory of the triplet states of oligoacenes containing up to seven rings, i.e., starting from naphthalene all the way up to heptacene. In particular, we present results on the optical absorption from the first triplet excited state 1 3 B + 2u of these oligomers, computed using the Pariser-Parr-Pople (PPP) model Hamiltonian, and a correlated electron approach employing the configuration-interaction (CI) methodology at various levels. Excitation energies of various triplets states obtained by our calculations are in good agreement with the experimental results, where available. The computed triplet spectra of oligoacenes exhibits rich structure dominated by two absorption peaks of high intensities, which are well separated in energy, and are caused by photons polarized along the conjugation direction. This prediction of ours can be tested in future experiments performed on oriented samples of oligoacenes.

Theory of Linear Optical Absorption of Diamond Shaped Graphene Quantum Dots

by Himanshu Chakraborty, tista basak, and Alok Shukla

In this paper, optical and electronic properties of diamond shaped graphene quantum dots (DQDs) h... more In this paper, optical and electronic properties of diamond shaped graphene quantum dots (DQDs) have been studied by employing large-scale electron-correlated calculations. The
computations have been performed using the pi-electron Pariser-Parr-Pople model Hamiltonian, which incorporates long-range Coulomb interactions. The influence of electron correlation effects on the ground and excited states has been included by means of the configuration-interaction approach, used at various levels. Our calculations have revealed that the absorption spectra are red-shifted with the increasing sizes of quantum dots. It has been observed that the first peak of the linear optical absorption, which represents the optical gap, is not the most intense peak. This result is in excellent agreement with the experimental data, but in stark contrast to the predictions of the tight-binding model, according to which the first peak is the most intense peak, pointing to the importance of electron-correlation effects. Furthermore, an analysis of the wave functions of the excited states contributing to the spectra reveals the presence of plasmonic effects.

Triplet optical absorption in acenes: Naphthalene to Heptacene

by Himanshu Chakraborty and Alok Shukla

Ground and Excited States of Long Acenes

Several years ago, Angliker et al. [Chem. Phys. Lett. 1982, 87, 208] predicted nonacene to be the... more Several years ago, Angliker et al. [Chem. Phys. Lett. 1982, 87, 208] predicted nonacene to be the first linear acene with the triplet state 1 3 B 2u as the ground state, instead of the singlet 1 1 A g state. However, contrary to that prediction, in a recent experimental work, Tonshoff and Bettinger [Angew. Chem. Int. Ed. 2010, 49, 4125] demonstrated that nonacene has a singlet ground state. Motivated by this experimental finding, we decided to perform a systematic theoretical investigation of the nature of the ground and the low-lying excited states of long acenes, with an emphasis on the singlet−triplet gap, starting from naphthalene, all the way up to decacene. The methodology adopted in our work is based upon the Pariser−Parr−Pople model (PPP) Hamiltonian, along with the large-scale multireference singles-doubles configuration interaction (MRSDCI) approach. Our results predict that even though the singlet− triplet gap decreases with the increasing conjugation length, nevertheless, it remains finite till decacene, thus providing no evidence of the predicted singlet−triplet crossover. We also analyze the nature of many-particle wave function of the correlated singlet ground state and find that the longer acenes exhibit a tendency toward an open-shell singlet ground state. Moreover, when we compare the experimental absorption spectra of octacene and nonacene with their calculated singlet and triplet absorption spectra, we observe excellent agreement for the singlet case. Hence, the optical absorption results also confirm the singlet nature of the ground state for longer acenes. Calculated triplet absorption spectra of acenes predict two well-separated intense long-axis polarized absorptions, against one such peak observed for the singlet case. This is an important prediction regarding the triplet optics of acenes, which can be tested in future experiments on oriented samples.

Light-induced dilation in nanosheets of charge-transfer complexes

Proceedings of the National Academy of Sciences

We report the observation of a sizable photostrictive effect of 5.7% with fast, submillisecond re... more We report the observation of a sizable photostrictive effect of 5.7% with fast, submillisecond response times, arising from a light-induced lattice dilation of a molecular nanosheet, composed of the molecular charge-transfer compound dibenzotetrathiafulvalene (DBTTF) and C60. An interfacial self-assembly approach is introduced for the thickness-controlled growth of the thin films. From photoabsorption measurements, molecular simulations, and electronic structure calculations, we suggest that photostriction within these films arises from a transformation in the molecular structure of constituent molecules upon photoinduced charge transfer, as well as the accommodation of free charge carriers within the material. Additionally, we find that the photostrictive properties of the nanosheets are thickness-dependent, a phenomenon that we suggest arises from surface-induced conformational disorder in the molecular components of the film. Moreover, because of the molecular structure in the fi...

Effect of Intercalated Metals on the Electrocatalytic Activity of 1T-MoS 2 for the Hydrogen Evolution Reaction

by Himanshu Chakraborty, Nuwan Attanayake, and John Perdew

We show that intercalation of cations (Na + , Ca 2+ , Ni 2+ , and Co 2+) into the interlayer regi... more We show that intercalation of cations (Na + , Ca 2+ , Ni 2+ , and Co 2+) into the interlayer region of 1T-MoS 2 is an effective strategy to lower the overpotential for the hydrogen evolution reaction (HER). In acidic media the onset potential for 1T-MoS 2 with intercalated ions is lowered by ∼60 mV relative to that for pristine 1T-MoS 2 (onset of ∼180 mV). Density functional theory (DFT) calculations show a lowering in the Gibbs free energy for H-adsorption (ΔG H) on these intercalated structures relative to intercalant-free 1T-MoS 2. The DFT calculations suggest that Na + intercalation results in a ΔG H close to zero. Consistent with calculation, experiments show that the intercalation of Na + ions into the interlayer region of 1T-MoS 2 results in the lowest overpotential for the HER.

Tunable two-dimensional interfacial coupling in molecular heterostructures

by Himanshu Chakraborty and Vivek Kumar Yadav

Two-dimensional van der Waals heterostructures are of considerable interest for the next generati... more Two-dimensional van der Waals heterostructures are of considerable interest for the next generation nanoelectronics because of their unique interlayer coupling and optoelectronic properties. Here, we report a modified Langmuir–Blodgett method to organize two-dimensional molecular charge transfer crystals into arbitrarily and vertically stacked het-erostructures, consisting of bis(ethylenedithio)tetrathiafulvalene (BEDT–TTF)/C 60 and poly (3-dodecylthiophene-2,5-diyl) (P3DDT)/C 60 nanosheets. A strong and anisotropic interfacial coupling between the charge transfer pairs is demonstrated. The van der Waals hetero-structures exhibit pressure dependent sensitivity with a high piezoresistance coefficient of −4.4 × 10 −6 Pa −1 , and conductance and capacitance tunable by external stimuli (ferroelectric field and magnetic field). Density functional theory calculations confirm charge transfer between the n-orbitals of the S atoms in BEDT–TTF of the BEDT–TTF/C 60 layer and the π* orbitals of C atoms in C 60 of the P3DDT/C 60 layer contribute to the inter-complex CT. The two-dimensional molecular van der Waals heterostructures with tunable optical–electronic–magnetic coupling properties are promising for flexible electronic applications.

A Free-Standing Molecular Spin–Charge Converter for Ubiquitous Magnetic-Energy Harvesting and Sensing

Self-powered organic conjugated materials are of vital impor- tance for the development of next-g... more Self-powered organic conjugated materials are of vital impor-
tance for the development of next-generation, flexible, and fully
integrated energy, sensing, and artificial-intelligence technolo-
gies. Due to their exceptionally long spin lifetimes and strong
spin–charge interactions, these carbon materials could also
impact data transmission, processing, and storage. However, to
exploit these opportunities, the ability to directly convert energy
from spin information to electric charge is essential. Here,
we introduce a novel molecular spin–charge converter that is
comprised of a centimeter-sized free-standing organic charge-
transfer crystal. Magnetic-field effects in this material induce
intersystem crossings and spin–charge-lattice couplings that
generate an electric voltage for magnetic-energy harvesting.
The effective conversion between charge and spin stimulus
permits simultaneous and instantaneous self-powering and
sensing performance in a molecular crystal that displays ani-
sotropic behavior dependent on crystal orientation. We con-
firm the strong charge-transfer character of the crystals with
first principle calculations of the electronic density of states.
The solution processed flexible devices also exhibit an excellent
temperature sensitivity of <0.01 K and a unique piezoresistance
coefficient of −5.1 × 10 −6 Pa −1 . The self-powered sensing perfor-
mance of this molecular spin–charge converter, together with
its solution processability and flexibility, endow this molecular
charge-transfer crystal with the capability to drive a new gen-
eration of noncontact magnetic-energy harvesting and sensing
technologies.

Superior performance of borocarbonitrides, B x C y N z , as stable, low-cost metal-free electrocatalysts for hydrogen evolution reaction

Energy Environ. Sci., 2015

We report superior hydrogen evolution activity of metal-free borocarbonitride (BCN) catalysts. Th... more We report superior hydrogen evolution activity of metal-free borocarbonitride (BCN) catalysts. The highly positive onset potential (À56 mV vs. RHE) and the current density of 10 mA cm À2 at an overpotential of 70 mV exhibited by a carbon-rich BCN with the composition BC 7 N 2 demonstrates the extraordinary electrocatalytic activity at par with Pt. Theoretical studies throw light on the cause of high activity of this composition. The high activity and good stability of BCNs surpass the characteristics of other metal-free catalysts reported in recent literature.

Large scale configuration interaction calculations of linear optical absorption of octacene and nonacene

by Himanshu Chakraborty and Alok Shukla

ABSTRACT The technological importance of higher acenes has led to resurgence of interest in synth... more ABSTRACT The technological importance of higher acenes has led to resurgence of interest in synthesizing higher acenes such as octacene, nonacene etc.[1] Recently, Tonshoff and Bettinger have synthesized octacene and nonacene [2]. Motivated by their work, we have performed large scale calculations of linear optical absorption of octacene and nonacene and compared the results with their experimental work. Methodology adopted in our work is based upon Pariser-Parr-Pople model (PPP) Hamiltonian, along with large-scale multi-reference singles-doubles configuration interaction (MRSDCI) approach.

Large scale configuration interaction calculations of linear optical absorption of decacene

ABSTRACT The technological importance of higher acenes has led to resurgence of interest in synth... more ABSTRACT The technological importance of higher acenes has led to resurgence of interest in synthesizing them e.g. octacene, nonacene and decacene [1]. Recently, Tönshoff and Bettinger have synthesized octacene and nonacene [2]. Motivated by their work, we have performed large scale calculations of linear optical absorption of decacene. Methodology adopted in our work is based upon Pariser-Parr-Pople model (PPP) Hamiltonian, along with largescale multi-reference singles-doubles configuration interaction (MRSDCI) approach.

Theory of triplet optical absorption in oligoacenes: From naphthalene to heptacene

by Himanshu Chakraborty and Alok Shukla

The Journal of Chemical Physics, 2014

In this paper we present a detailed theory of the triplet states of oligoacenes containing up to ... more In this paper we present a detailed theory of the triplet states of oligoacenes containing up to seven rings, i.e., starting from naphthalene all the way up to heptacene. In particular, we present results on the optical absorption from the first triplet excited state 1 3 B + 2u of these oligomers, computed using the Pariser-Parr-Pople (PPP) model Hamiltonian, and a correlated electron approach employing the configuration-interaction (CI) methodology at various levels. Excitation energies of various triplets states obtained by our calculations are in good agreement with the experimental results, where available. The computed triplet spectra of oligoacenes exhibits rich structure dominated by two absorption peaks of high intensities, which are well separated in energy, and are caused by photons polarized along the conjugation direction. This prediction of ours can be tested in future experiments performed on oriented samples of oligoacenes.

Theory of Linear Optical Absorption of Diamond Shaped Graphene Quantum Dots

by Himanshu Chakraborty, tista basak, and Alok Shukla

In this paper, optical and electronic properties of diamond shaped graphene quantum dots (DQDs) h... more In this paper, optical and electronic properties of diamond shaped graphene quantum dots (DQDs) have been studied by employing large-scale electron-correlated calculations. The
computations have been performed using the pi-electron Pariser-Parr-Pople model Hamiltonian, which incorporates long-range Coulomb interactions. The influence of electron correlation effects on the ground and excited states has been included by means of the configuration-interaction approach, used at various levels. Our calculations have revealed that the absorption spectra are red-shifted with the increasing sizes of quantum dots. It has been observed that the first peak of the linear optical absorption, which represents the optical gap, is not the most intense peak. This result is in excellent agreement with the experimental data, but in stark contrast to the predictions of the tight-binding model, according to which the first peak is the most intense peak, pointing to the importance of electron-correlation effects. Furthermore, an analysis of the wave functions of the excited states contributing to the spectra reveals the presence of plasmonic effects.

Triplet optical absorption in acenes: Naphthalene to Heptacene

by Himanshu Chakraborty and Alok Shukla

Ground and Excited States of Long Acenes

Several years ago, Angliker et al. [Chem. Phys. Lett. 1982, 87, 208] predicted nonacene to be the... more Several years ago, Angliker et al. [Chem. Phys. Lett. 1982, 87, 208] predicted nonacene to be the first linear acene with the triplet state 1 3 B 2u as the ground state, instead of the singlet 1 1 A g state. However, contrary to that prediction, in a recent experimental work, Tonshoff and Bettinger [Angew. Chem. Int. Ed. 2010, 49, 4125] demonstrated that nonacene has a singlet ground state. Motivated by this experimental finding, we decided to perform a systematic theoretical investigation of the nature of the ground and the low-lying excited states of long acenes, with an emphasis on the singlet−triplet gap, starting from naphthalene, all the way up to decacene. The methodology adopted in our work is based upon the Pariser−Parr−Pople model (PPP) Hamiltonian, along with the large-scale multireference singles-doubles configuration interaction (MRSDCI) approach. Our results predict that even though the singlet− triplet gap decreases with the increasing conjugation length, nevertheless, it remains finite till decacene, thus providing no evidence of the predicted singlet−triplet crossover. We also analyze the nature of many-particle wave function of the correlated singlet ground state and find that the longer acenes exhibit a tendency toward an open-shell singlet ground state. Moreover, when we compare the experimental absorption spectra of octacene and nonacene with their calculated singlet and triplet absorption spectra, we observe excellent agreement for the singlet case. Hence, the optical absorption results also confirm the singlet nature of the ground state for longer acenes. Calculated triplet absorption spectra of acenes predict two well-separated intense long-axis polarized absorptions, against one such peak observed for the singlet case. This is an important prediction regarding the triplet optics of acenes, which can be tested in future experiments on oriented samples.