Characterization of magnetic states of graphene quantum dots of different shapes by application of electric field

Basak, Tushima; Basak, Tista

doi:10.1016/j.matpr.2020.02.447

Cited by 6 publications

(3 citation statements)

References 20 publications

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“…The last term in this equation depicts the long-range Coulomb repulsion with the parameter V ij incorporating screening effects in accordance to the Ohno relationship wherein the screening effects are simulated by the dielectric constant of the system and R i , j denotes the spacing between adjacent carbon atoms (in Å). The screened parameters U = 8.0 eV, κ i , i = 1.0, and are employed, in agreement with our earlier studies. − …”

Section: Theoretical Model and Computational Approachsupporting

confidence: 66%

Graphene Quantum Dot with Divacancy and Topological Defects: A Novel Material for Promoting Prompt and Delayed Fluorescence of Tunable Wavelengths

Basak¹,

Basak

Shukla

2022

J. Phys. Chem. C

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This work demonstrates the unique approach of introducing divacancy imperfections in topological Stone–Wales type defected graphene quantum dots for harvesting both singlet and triplet excitons, essential for fabricating fluorescent organic light-emitting diodes. Here, we first reveal that structural relaxation of these systems establishes the high-spin triplet state as the stable ground state at room temperature, thereby significantly increasing their potential in designing spintronic devices. Our extensive electron-correlated computations then demonstrate that the energetic ordering of the singlet and triplet states in these relaxed structures can trigger both prompt and delayed fluorescence of different wavelengths through various decay channels. Particularly, the position of divacancy determines the tunability range of the emission wavelengths. In addition, our results obtained from both multireference singles–doubles configuration–interaction (MRSDCI) and first-principles time-dependent density functional theory (TDDFT) methodologies highlight that the synergetic effects of divacancy position, structural relaxation, and spin multiplicity critically govern the nature and magnitude of shift exhibited by the most intense peak of the absorption profile, crucial for designing optoelectronic devices.

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Section: Theoretical Model and Computational Approachsupporting

confidence: 66%

Graphene Quantum Dot with Divacancy and Topological Defects: A Novel Material for Promoting Prompt and Delayed Fluorescence of Tunable Wavelengths

Basak¹,

Basak

Shukla

2022

J. Phys. Chem. C

Self Cite

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show abstract

“…and R i,j denotes the spacing between adjacent carbon atoms (in Å). The screened parameters with U = 8.0 eV, κ i,i = 1.0 and κ i,j = 2.0 (i = j) are employed, in agreement with our earlier studies [20][21][22][23][24] .…”

Section: Theoretical Model and Computational Approachmentioning

confidence: 53%

Graphene Quantum Dot with Divacancy and Topological Defects: A Novel Material for Promoting Prompt and Delayed Fluorescence of Tunable Wavelengths

Basak,

Shukla

2022

Preprint

Self Cite

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This work demonstrates the unique approach of introducing divacancy imperfections in topological Stone-Wales type defected graphene quantum dots for harvesting both singlet and triplet excitons, essential for fabricating fluorescent organic light-emitting diodes. Here, we first reveal that structural relaxation of these systems establishes the high-spin triplet state as the stable ground state at room temperature, thereby significantly increasing their potential in designing spintronic devices. Our extensive electron-correlated computations then demonstrate that the energetic ordering of the singlet and triplet states in these relaxed structures can trigger both prompt and delayed

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“…Comprehensive insight into the mechanisms governing the intriguing optical properties of GQDs is essential for their practical application in optoelectronic devices. For sizes of GQDs of less than 100 nm, quantum confinement and edge effects play a crucial role in deciding their photoluminescence (PL) − and absorption properties. − This has triggered tremendous experimental and theoretical research to selectively regulate the optical characteristics of pristine GQDs through various techniques such as surface functionalization, heteroatom doping, and the introduction of defects , in recent years.…”

Section: Introductionmentioning

confidence: 99%

Edge Modification and Site-Selective Functionalization of Graphene Quantum Dots: A Versatile Technique for Designing Tunable Optoelectronic and Sensing Devices

Basak

Basak²

2023

J. Phys. Chem. A

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This work successfully traces the imprints of zigzag/armchair-edge modification and site-selective functionalization by different chemical species in dictating the structural, electronic, and optical properties of low-symmetry structural isomers of graphene quantum dots (GQDs). Our time-dependent density functional theory-based computations reveal that the electronic band gap reduction is greater for zigzag-edge functionalization than for armchair-edge modification by chlorine atoms. The computed optical absorption profile of functionalized GQDs exhibits an overall red shift with respect to their pristine counterpart, with the shift being more pronounced at higher energies. Markedly, the optical gap energy is regulated more substantially by zigzag-edge chlorine passivation while the armchair-edge chlorine functionalization is more effective in altering the position of the most intense (MI) absorption peak. The MI peak energy is exclusively decided by the significant perturbation in the electron–hole distribution produced by the structural warping of the planar carbon backbone realized by edge-functionalization while the interplay between frontier orbital hybridization and structural distortion governs the energies of the optical gap. In particular, the enhanced tunability range of the MI peak in comparison to the optical gap variation signals that the structural warping plays a more decisive role in modulating the MI peak characteristics. The energy of the optical gap and the MI peak along with the charge-transfer character of the excited states is critically dependent on the electron-withdrawing capability and the site of the functional group. This comprehensive study is extremely crucial for promoting the application of functionalized GQDs in designing highly efficient tunable optoelectronic devices.

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Characterization of magnetic states of graphene quantum dots of different shapes by application of electric field

Cited by 6 publications

References 20 publications

Graphene Quantum Dot with Divacancy and Topological Defects: A Novel Material for Promoting Prompt and Delayed Fluorescence of Tunable Wavelengths

Graphene Quantum Dot with Divacancy and Topological Defects: A Novel Material for Promoting Prompt and Delayed Fluorescence of Tunable Wavelengths

Graphene Quantum Dot with Divacancy and Topological Defects: A Novel Material for Promoting Prompt and Delayed Fluorescence of Tunable Wavelengths

Edge Modification and Site-Selective Functionalization of Graphene Quantum Dots: A Versatile Technique for Designing Tunable Optoelectronic and Sensing Devices

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