ABSTRACT
Using Density Functional Theory (DFT) and time-dependent DFT (TD-DFT), we studied a compound widely used in daily life, namely: Methyl Methacrylate (MMA) monomer in its two stable isomers, cis-MMA and trans-MMA. The impact of conformation on the optical and electronic properties of MMA was highlighted. Structural parameters and thermodynamic properties were also assessed, and allowed to discuss the stability and reactivity of this compound. In addition, analysis of optoelectronic and electronic properties, global reactivity descriptors, natural bond orbital (NBO), and hole and electron reorganization energies was performed. The absorption and fluorescence properties, as well as the linear and nonlinear optical (NLO) properties of MMA were also investigated. The findings show that MMA is an insulator due to its wide band gap of 6.20 eV. It also exhibits good optoelectronic properties with high average electric field values of about 5.90 × 109 Vm-1 for cis-MMA and 5.42 × 109 Vm-1 for trans-MMA and high electric displacement values of at least 14.65 × 10-2 cm-2 for cis-MMA and 14.33 × 10-2 cm-2 for trans-MMA, suggesting a potential use for the design of piezoelectric and pyroelectric materials. In addition, trans-MMA has a dielectric constant close to that of good insulators; while cis-MMA exhibits a dielectric behaviour close to that of polymeric substances. Further, these materials are thermodynamically stable in its two conformations, with a good reactivity which can lead to good ability of polymerization. The analysis of the UV-vis spectra revealed that both forms of MMA absorb and emit mainly in the UV and that the Stokes shift of MMA is low, reducing its potential use in devices such as solar cells. At NLO level, MMA isomers exhibit weak optical properties such as second- and third-order optical susceptibility and cannot suitable for second and third harmonic generation; however, the conformation enhances second-order NLO response by at least 2 times when moving from cis- to trans-MMA, whereas the third-order response is almost unaffected. In addition, the conformation also affects the electronic and optoelectronic properties of MMA.
ABSTRACT
Density functional theory (DFT) calculations of the antimalarial drug dihydroartemisinin (DHA) functionalized on the carbon nanotube (CNT) were carried out in gas phase and in solution to investigate the role of fCNTs as a nanovector for the targeted delivery of the DHA drug and to predict their chemical descriptors and electronic and nonlinear optical (NLO) properties. The results of the geometric optimization indicate that the functionalization does not change the molecular structure of DHA. Based on our findings of binding and solvation energies, two energetically stable configurations were identified in 1st (fCNT1-2) and 2nd (2fCNT1-2) functionalization. For these stable configurations, the energy gap value goes from 1.52 eV for the (5,5) single wall pristine CNT to 1.27 eV for the 1st functionalization and to 1.06 eV for the 2nd functionalization regardless of the considered media; which gives these nanostructures excellent semiconductor properties. Findings from global reactivity descriptors show that the reactivity of the functionalized CNT is strongly improved in solvent media and that the stability of DHA decreases while its reactivity increases during the functionalization. Thus, the fundamental gap (Ef) in gas phase decreases from 3.65 eV for the virgin CNT to 3.30 eV for fCNT2 and to 3.02 eV for 2fCNT2. On the contrary, in water Ef goes from 1.20 eV for the virgin CNT to 0.95 eV for fCNT2 and to 0.74 eV for 2fCNT2; demonstrating an improvement in the reactivity of our fCNTs as nanovectors for targeted delivery of DHA drug. Finally, our findings show that these nanostructures may also have good NLO properties and can be promising materials for NLO applications.
ABSTRACT
Hartree-Fock (HF) and Density Functional Theory (DFT) studies were conducted to assess the impact of potassium doping on the thermodynamic, optoelectronic, electronic and nonlinear optical properties and on the reactivity of photochromic polymers containing styrylquinoline fragments. Doping was carried out on the virgin monomer (M1) and on the derivative monomer (M2) with the nitro group NO2. Three doped monomers were investigated including, the monomer M3 obtained from M1 by substituting the H atom with a potassium, the monomer M4 by substituting two H atoms and the monomer M5 obtained from M2 by substituting the H atom. Findings proved that the use of potassium and the nitro group is an excellent process to improve the electronics properties of styrylquinoline virgin monomers. In fact, the energy gap decreases from 3.82 eV for M1 to 3.02 eV and to 2.92 eV for M3 and M4, respectively; while the decrease from 3.43 eV for M2 to 2.52 eV for M5 was observed, thus demonstrating the good semiconductor character of the obtained compounds with relevant applications in the manufacture of solar cells. Likewise, the fundamental gap decreases from 6.50 eV for M1 to 5.34 eV and to 4.62 eV for M3 and M4, respectively; while the decrease from 6.11 eV for M2 to 5.21 eV for M5 was observed; thus demonstrating an improvement in the reactivity of our doped monomers. In addition, potassium doping is an appropriate method to enhance optoelectronic properties of styrylquinoline virgin monomers. Thus, the refractive index of our doped monomers is greater than that of glass, which is a reference in optic and can be used under high electric fields of the order of 1.90 × 10 9 Vm-1 for monomer M4 up to 7.01 × 10 9 Vm-1 for M3 and to 10.89 × 10 9 Vm-1 for M5. Finally, the strong enhancement of the linear and nonlinear optical (NLO) properties that we observed leads us to conclude that these doped monomers can be appropriate candidates in devices requiring good NLO properties.
