Strong enhancement of NLO response of methyl orange dyes through solvent effects: A sequential Monte Carlo/DFT investigation

Abstract A challenge in Photonics and Optoelectronics is to take advantage of specific environmental forces to enhance the nonlinear optical response of π -organic materials. Under this statement, it is carried out a systematic QM/MC investigation of the solvent effects on the linear and nonlinear optical properties of Methyl Orange, an important azo dye. Once such properties are strongly dependent on the molecular geometries, all DFT calculations were performed on solute molecules previously obtained at the perturbative MP2 Hamiltonian. The current investigation indicates that the solute polarization due to solvent is the main factor driving all optical properties of interesting, being a suitable mechanism to tune such properties. However, the solvent acts under different manners depending on the acid-base character of the solute. For instance, in comparison to gas-phase, the UV–visible spectra of hydrated acidic Methyl Orange are blueshifted to higher energies, but for alkaline molecule, bathochromic effects are perceived. Either for static β t o t a l and dynamic β H R S nonlinear optical constants, the effects of the medium are also contrary with respect to its pH. In fact, β H R S calculated for acidic molecules decreases from 236.20 × 10 − 30 esu to 11.65 × 10 − 30 esu, while for alkaline Methyl Orange, a reverse trend is found with the solvent increasing this optical property from 14.38 × 10 − 30 esu to 11.65 × 10 − 30 esu and becoming the alkaline structure a potential candidate for nonlinear optical applications.