Tunable optical absorption in silicene molecules

Mokkath, Junais Habeeb; Schwingenschlögl, Udo

doi:10.1039/c6tc02186g

Cited by 13 publications

(14 citation statements)

References 29 publications

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“…The only way to donate electrons without disturbing the out-of-plane π orbital is to modify the in-plane edges. A theoretical study of silicene molecules (large polycyclic molecules consisting of six-membered silicon rings) from Si 13 H 9 to Si 60 H 24 showed that silicene molecules with hydrogen atoms at the edge are not flat but have a low-buckled structure 30 . This indicates that, as described above, electron-donating substituents are good candidates for the formation of flat silicene molecules and hydrogen atoms are not suitable.…”

Section: Introductionmentioning

confidence: 99%

Flat building blocks for flat silicene

Takahashi

2017

Sci Rep

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Silicene is the silicon equivalent of graphene, which is composed of a honeycomb carbon structure with one atom thickness and has attractive characteristics of a perfect two-dimensional π-conjugated sheet. However, unlike flat and highly stable graphene, silicene is relatively sticky and thus unstable due to its puckered or crinkled structure. Flatness is important for stability, and to obtain perfect π-conjugation, electron-donating atoms and molecules should not interact with the π electrons. The structural differences between silicene and graphene result from the differences in their building blocks, flat benzene and chair-form hexasilabenzene. It is crucial to design flat building blocks for silicene with no interactions between the electron donor and π-orbitals. Here, we report the successful design of such building blocks with the aid of density functional theory calculations. Our fundamental concept is to attach substituents that have sp-hybrid orbitals and act as electron donors in a manner that it does not interact with the π orbitals. The honeycomb silicon molecule with BeH at the edge designed according to our concept, clearly shows the same structural, charge distribution and molecular orbital characteristics as the corresponding carbon-based molecule.

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Section: Introductionmentioning

confidence: 99%

Flat building blocks for flat silicene

Takahashi

2017

Sci Rep

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“…Highly conjugated molecules are known to support plasmons by virtue of their free π‐electron cloud. Graphene and silicene have been shown to support strong molecular plasmons. Recently, the absorption profiles for silicene molecules were investigated using time‐dependent density functional theory (TD‐DFT) by Mokkath et al .…”

Section: Introductionmentioning

confidence: 99%

“…Graphene and silicene have been shown to support strong molecular plasmons. Recently, the absorption profiles for silicene molecules were investigated using time‐dependent density functional theory (TD‐DFT) by Mokkath et al . The plasmonic peaks in silicenes were inferred on the basis of a high oscillator strength.…”

Section: Introductionmentioning

confidence: 99%

“…Highly conjugated molecules are knownt os upport plasmons by virtue of their free p-electron cloud. Graphene [11,12] and silicene [13] have been shown to support strong molecular plasmons.R ecently,t he absorption profiles for silicenem olecules were investigated using time-dependent density functional theory( TD-DFT) by Mokkath et al [13] The plasmonic peaks in silicenes were inferred on the basis of ah igh oscillator strength.T he existence of molecular plasmons was first theoreticallyd emonstrated in sodium (Na 20 )a nd silver (Ag 20 )c lusters, fullerene( C 60 ), [3] and in polycyclic aromatic hydrocarbons. [14] The sensitivity of ap lasmon to the net charge state of the molecule, high tunability and strong interaction between plasmonsi nn eighbouring molecules have been reported.…”

Section: Introductionmentioning

confidence: 99%

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Electronic Rearrangement in Molecular Plasmons: An Electron Density and Electrostatic Potential‐Based Study

Paul

Balanarayan

2018

ChemPhysChem

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Plasmonic modes in single-molecule systems have been previously identified by scaling two-electron interactions in calculating excitation energies. Analysis of transition dipole moments for states of polyacenes based on configuration interaction is another method for characterising molecular plasmons. The principal features in the electronic absorption spectra of polyacenes are a low-intensity, lower-in-energy peak and a high-intensity, higher-in-energy peak. From calculations using time-dependent density functional theory with the B3LYP/cc-pVTZ basis set, both these peaks are found to result from the same set of electronic transitions, that is, HOMO-n to LUMO and HOMO to LUMO+n, where n varies as the number of fused rings increases. In this work, the excited states of polyacenes, naphthalene through pentacene, are analysed using electron densities and molecular electrostatic potential (MESP) topography. Compared to other excited states the bright and dark plasmonic states involve the least electron rearrangement. Quantitatively, the MESP topography indicates that the variance in MESP values and the displacement in MESP minima positions, calculated with respect to the ground state, are lowest for plasmonic states. The excited-state electronic density profiles and electrostatic potential topographies suggest the least electron rearrangement for the plasmonic states. Conversely, high electron rearrangement characterises a single-particle excitation. The molecular plasmon can be called an excited state most similar to the ground state in terms of one-electron properties. This is found to be true for silver (Ag ) and sodium (Na ) linear chains as well.

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“…Highly conjugated molecules are known to support plasmons by virtue of their free π-electron cloud. Graphene 9,10 and silicene 11 have been shown to support strong molecular plasmons. Quite recently, the absorption profiles for silicene molecules were investigated using time-dependent functional theory (TD-DFT) by Mokkath et al 11 The plasmonic peak in silicenes were inferred on the basis of a higher oscillator strength.…”

Section: Introductionmentioning

confidence: 99%

Electron density and electrostatic potential-based characteristics of molecular plasmons in polyacenes

Paul¹,

Balanarayan

2017

Preprint

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<div>Plasmonic modes in single-molecule systems have been previously identified by scaling two-electron interactions while calculating excitation energies [Bernadotte et al., J. Phys. Chem. C, 2013, <b>117</b>, 1863]. Analysis of transition dipole moments for states of polyacenes based on configuration interaction [Guidez et al., J. Phys. Chem. C, 2013, <b>117</b>, 21466.] was yet another method characterizing molecular plasmons. The principal features in the electronic absorption spectra for polyacenes are a low-intensity, lower-in-energy peak (denoted as α) and a high-intensity, higher-in-energy peak (β ). From our calculations using time-dependent density functional theory (TD-DFT) at B3LYP/cc-pVTZ basis, both the peaks were found to result from the same set of electronic transitions (HOMO-n to LUMO and HOMO to LUMO+n, where n varies as the number of fused rings increases). In this work, the excited states of polyacenes, naphthalene through pentacene, have been analysed using electron densities and molecular electrostatic potential (MESP) topography. The bright and dark plasmonic states involve the least electron rearrangement, as compared to other excited states. Quantitatively, the MESP topography indicates that the variance in MESP values as well as displacement in minima positions (calculated with respect to the ground state) are lowest for plasmonic states. This suggests a resemblance between the plasmonic and ground state electronic density profiles and electrostatic potential topographies. On the other hand, a high electron-rearrangement characterizes a single particle excitation. The molecular plasmon can be called an excited state most similar to the ground state in terms of one-electron properties.</div>

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Tunable optical absorption in silicene molecules

Abstract: Two-dimensional materials with a tunable band gap that covers a wide range of the solar spectrum hold great promise for sunlight harvesting.

Cited by 13 publications

References 29 publications

Flat building blocks for flat silicene

Flat building blocks for flat silicene

Electronic Rearrangement in Molecular Plasmons: An Electron Density and Electrostatic Potential‐Based Study

Electron density and electrostatic potential-based characteristics of molecular plasmons in polyacenes

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