in which the nonlinear optical (NLO) response strikingly improved with double heteroaromatic rings. Herein, series of triphenylamine−dicyanovinylene based donor−π−acceptor dyes had been designed by structural tailoring of π-conjugated linkers and theoretical descriptions of their molecular NLO properties were reported. Density functional theory and timedependent density functional theory calculations were performed on optimized geometries to elucidate the electronic structures, absorption spectra, and NLO properties and also to shed light on how structural modification influences the NLO properties. The simulated absorption spectra results indicate that all of the dyes showed the maximum absorbance wavelength in the visible region. The lowest unoccupied molecular orbital−highest occupied molecular orbital energy gaps of all of the dyes have been found smaller, which results in large NLO response. Calculation of natural bond orbital analysis reveals that electrons successfully migrated from donor to acceptor via π-conjugated linkers and a charge separation state was formed. High NLO response revealed that this class of metal free organic dyes possess eye-catching and remarkably large first hyperpolarizability values, especially D8 with highest ⟨α⟩ and β tot computed to be 771.80 and 139 075.05 au, respectively. Our research presented a vital confirmation for controlling the kinds of π-conjugated linker that was a significant approach for the design of new appealing NLO compounds. This theoretical framework also highlighted the NLO properties of organic dyes that can be valuable for their uses in modern hi-tech applications.

Materials with nonlinear optical properties have significant applications in nuclear science, biophysics, medicine, chemical dynamics, solid physics & materials science. We show how π bridges, donors & acceptors can be reconfigured to improve optical properties.

Nanostructured gas sensors find diverse applications in environmental and agricultural monitoring. Herein, adsorption of phosgene (COCl 2 ) on pure and copper-decorated B 12 N 12 (Cu−BN) is analyzed through density functional theory (DFT) calculations. Adsorption of copper on B 12 N 12 results in two optimized geometries, named Cu@b 66 and Cu@b 64 , with adsorption energies of −193.81 and −198.45 kJ/mol, respectively. The adsorption/interaction energies of COCl 2 on pure BN nanocages are −9.30, −6.90, and −3.70 kJ/mol in G1, G2, and G3 geometries, respectively, whereas the interaction energies of COCl 2 on copper-decorated BN are −1.66 and −16.95 kJ/mol for B1 and B2, respectively. To examine the changes in the properties of pure and Cu−BN nanocages, geometric parameters, dipole moment, Q NBO , frontier molecular orbitals, and partial density of states (PDOS) are analyzed to comprehensively illustrate the interaction mechanism. The results of these parameters reveal that COCl 2 binds more strongly onto copper-doped BN nanocages. Moreover, a higher charge separation is observed in COCl 2 −Cu−BN geometries as compared to copper-decorated BN geometries. Therefore, these nanocages may be considered as potential candidates for application in phosgene sensors.

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