HOMO-LUMO gaps of large polycyclic aromatic hydrocarbons and their implication on the quantum confinement behavior of flame-formed carbon nanoparticles

Synthesis, solvent role, absorption and emission studies of cytosine derivative

“…The quantification of a molecule's capacity to accept electrons is evaluated by the global electrophilicity index, which relies on the concepts of chemical potential and chemical hardness [ 61 ]. The observed low electrophilicity value of 6.01 eV further reinforces the notion of the produced material's strong stability and bioactivity, as previously reported [ 62 ]. The determination of the stability index of the compounds was accomplished through the assessment of the HOMO-LUMO energy gap, which concurrently offers insights into the wavelength at which the molecule is capable of absorbing.…”

Synthesis, vibrational analysis, absorption and emission spectral studies, topology and molecular docking studies on sulfadiazine derivative

“…The primary cause of the observed transition is the excitation from a π orbital to a π* orbital. Electron density is shown to undergo transfer from the region of higher aromaticity within the conjugated system, towards the electron‐withdrawing moiety [49] . The Figure 8 illustrates the HOMO and LUMO surface map.…”

“…Electron density is shown to undergo transfer from the region of higher aromaticity within the conjugated system, towards the electron-withdrawing moiety. [49] The Figure 8 illustrates the HOMO and LUMO surface map. The HOMO orbital has been seen over a six-membered ring, extending onto the phenylaniline ring through the NÀ H bond and onto the C=N group.…”

Data-Driven Insights into the Fluorescence of Asphaltene Aggregates Using Extended Frenkel Exciton Model

“…In the past few decades, quantum chemistry calculations with density functional theory (DFT) have been widely used in studying PAH and its aggregates, including reproducing structural parameters, 24 analyzing inter-molecular interactions, [25][26][27][28][29][30][31] and predicting absorption/fluorescence spectroscopies. [32][33][34][35][36][37][38][39][40] Alvarez-Ramírez and Ruiz-Morales systematic study on thousands of asphaltene-like PAH dimers showed that asphaltene dimer's optical gap falls within the experimental fluorescence energy range 1.9-3.1 eV if at least one of its monomer's optical gap is within this range. 41 Later, time-dependent density functional theory (TDDFT) studies on PAH aggregates in combustion soot showed that emission energies of PAH dimers are proportional to their monomer's average HOMO-LUMO gap 37,38 and usually do not exceed the fluorescence energy of the larger PAH.…”

“…The smallest molecule, PC152, has only 21 atoms with one six-membered ring, while the largest molecule, PB128, contains 118 atoms and 19 rings. Their fluorescence energies roughly negatively correlate with their molecular weight, which is usually explained by the quantum confinement effect 35. The highest fluorescence energy, 5.26 eV, corresponds to the smallest molecule PC152, while the lowest emission energy, 0.70 eV, corresponds to PA126, a large and complex PAH with a molecular weight of 909 amu.…”