Search

[Display omitted] • Six new anthracene based novel D–π–A organic dyes have been designed for DSSCs. • Substitution of –NO 2 and –CN (as donors) and –NH 2 and –N(CH 3) 2 (as acceptors) on 9,10-(bis-4-phenylazenyl)anthracene increases its light harvesting efficiency. • The dye bearing –N(CH 3) 2 (donor) and –NO 2 (acceptor) shows the greater bathochromic shift and broader absorption. • The greater charge transfer and highest λ max (994 nm) is also achieved for the same dye. The rational design of dyes for Dye-sensitized solar cells (DSSC) is challenging not only because the dye should absorb in the visible region but also have a favorable alignment with the semiconductor material. Dye sensitized solar cells (DSSCs) with donor-pi-acceptor (D-π-A) organic dyes have received significant interest by the scientific community since last few decades. In the present research work, six dyes (A1-A6) are designed based on 9,10-(bis-4-phenylazenyl)anthracene (R) skeleton by placing substituents on this scaffold. Density functional theory (DFT) and time dependent-DFT (TD-DFT) methods are used to theoretically investigate the optoelectronic properties of these dyes in order to study their potential for DSSCs application. It is also observed that the functionalization of reference compounds with different donor and acceptor groups increases electron injection and internal charge transfer (ICT) in the dye. The results of frontier molecular orbitals (FMO) indicate that the energy gap (E H-L) in A1-A6 is smaller than the reference compound. Among all the proposed dyes, A5 (the dye molecule with the largest number of donor moieties) showed the lowest band gap of 1.06 eV with a maximum absorption wavelength (λ max) value of 994 nm. Different parameters such as light harvesting efficiency (LHE), the free injection energy (ΔG inject), the dye regeneration energy (ΔG reg), open circuit voltage (V oc), reorganization energy (λ total), and excited state energy (τ) are also calculated. TDM analysis are also computed for all the proposed dyes from A1 to A5 and reference compound in order to understand the electronic excitation process. The theoretically calculated values of chemical hardness (η), and chemical potential (μ) suggest that changing the donor and acceptor groups on R compound can change the conductivity and ICT of dyes effectively. The dye A5 shows the lowest value for V oc i.e., 0.08 eV, which is sufficient for spontaneous transfer of electron from the LUMO of the dye to TiO 2 semiconductor. These results reveal that by modifying the donor and acceptor groups, the photovoltaic properties of the molecules can be enhanced. This theoretical work may provide a new path for experimentalists to synthesize these dyes for high performance DSSCs. [ABSTRACT FROM AUTHOR]

In this study, for the first time, static and dynamic NLO responses of pure and superhalogen doped aromatic heterocyclic monomers have been investigated by using density functional theory (DFT) calculations. The thermal, electronic, linear, and nonlinear optical properties are computed at the ωB97XD/6-31+G(d,p) method. The thermodynamic stabilities of reported complexes are estimated based on interaction energies, which are in the range of −28.06 to −83.20 kcal/mol. The lowest interaction energies are observed for AlF 4 @X (X = C 4 H 4 NH, C 4 H 4 O, C 4 H 4 S, and C 5 H 5 N) complexes, which correspond to their higher stabilities. The appreciable decrease in the HOMO-LUMO energy gap (E gap) is an indicative of the increase in reactivity after doping with superhalogens. The decrease in E gap is further demonstrated with the help of density of state (DOS) analysis. The significant nonlinear optical responses of the superhalogen doped aromatic heterocyclic monomers are due to the strong electron-withdrawing nature of the fluorine atom. Overall, the results indicate the high NLO response for the AlF 4 @X complexes due to the presence of four electron-withdrawing fluorine atoms in AlF 4. The NLO results are further analyzed through the two-level model. • Superhalogen doping of aromatic heterocyclic monomers is investigated for enhancement of NLO response. • HOMO-LUMO gap significantly decreases upon complexation. • AlF 4 @X exhibit significant thermodynamic stability upto −83.20 kcal/mol. • AlF 4 @X showed excellent third order nonlinear response. [ABSTRACT FROM AUTHOR]

The sensing affinity of C 4 N is the most fascinating topic of research due to its excellent chemical and electronic properties. Moreover, owing to the highly active porous cavity, C 4 N can easily accommodate foreign molecules. Herein, we studied the adsorption properties of carbamate insecticides (CMs) namely, Dimetalin (DMT), Carbanolate (CBT), Isolan (ISO) and Propoxur (PRO) using density functional theory calculations. All the results are calculated at widely accepted ωB97XD functional along with 6-31G(d, p) basis set. The calculated counterpoise corrected interaction energy of the reported complexes ranges between −20.05 and −27.04 kcal/mol, however, the interaction distances are found to be higher than 2.00 Å. The values of interacting parameters depict that the carbamate molecules are physisorbed via noncovalent interactions that can easily be reversible. Moreover, the binding of selected insecticides notably changes the electronic structure of C 4 N. The electronic changes are characterized by the energies of HOMO & LUMO, their energy gaps and CHELPG charge transfer. The charge density difference between C 4 N surface and carbamate pesticides are characterized by EDD and CDA analysis. Moreover, the ab initio molecular dynamic study reveals that the complexes are stable even at 500 K. The photochemical sensing properties of C 4 N are estimated by time dependent UV–Vis calculations. The high sensitivity of C 4 N towards considered analytes enable it to act as a promising sensor for toxic pesticides. [Display omitted] • The sensing of C 4 N towards carbamate insecticides is investigated within the framework of DFT. • The results are characterized by the geometric, energetic, electronic, and optical analyses. • All the results are computed at ωB97XD/6-31G (d,p) level of DFT. • The trend of thermodynamic stability of complexes is as follow; DMT@C4N > CBT@C4N > ISO@C4N > PRO@C4N. [ABSTRACT FROM AUTHOR]

[Display omitted] • Polaron formation in oligofurans is presented as a new strategy to improve nonlinear optical response. • Spin density suggest that polaron are stabilized as the chain length increases. • Polaron formation significantly increases static and dynamic hyperpolarizabilities. • The highest hyperpolarizability values of 3.1 × 104 au is observed for 9Fu*. The geometric, electronic and nonlinear optical properties of neutral and polaron based oligofurans are studied comparatively. We have reported the role of polaron to trigger the nonlinear optical response of oligofurans (nFu). The polaron based oligomers show excellent opto-electronic properties. The effect of polaron on nFu* chains is measured by electronic properties i.e (ionization energy, electron affinity, band gap) and global reactivity descriptors like softness, hardness and chemical potential than their neutral counterpart. An interesting trends of reactivity descriptors have been observed. Lower band gaps (E H-L = 4.66 and 4.41 eV) are observed for polaronic systems as compared to their neutral counterpart. On the other hand, the TD-DFT study further demonstrated that, as the size of chain increases, the absorption maxima (λ max) also increases with significant reduction in excitation energies (ΔE). Furthermore, the nonlinear optical response is confirmed through the linear polarizability ( α o ), static first order hyperpolarizability (β o) and dynamic (frequency denepndent) hyperpolarizability. Electric filed induced second harmonic generation (EFISHG) and electro-optic pockle effect (EOPE) at 532 nm and 1064 nm, commonly used lasers frequencies have also been employed. Our results showed that the maximum hyperpolarizabilities are observed for polaron based 7Fu* and 9Fu* i.e 1.3 × 104, and 3.1 × 104 au. This study concluded that these polaron based organic polymers (nFu*) are useful as an efficient NLO material with vast applications in different fields. [ABSTRACT FROM AUTHOR]