Accurate Simulation of Optical Properties in Dyes
ABSTRACT Since Antiquity, humans have produced and commercialized dyes. To this day, extraction of natural dyes often requires lengthy and costly procedures. In the 19th century, global markets and new industrial products drove a significant effort to synthesize artificial dyes, characterized by low production costs, huge quantities, and new optical properties (colors). Dyes that encompass classes of molecules absorbing in the UV-visible part of the electromagnetic spectrum now have a wider range of applications, including coloring (textiles, food, paintings), energy production (photovoltaic cells, OLEDs), or pharmaceuticals (diagnostics, drugs). Parallel to the growth in dye applications, researchers have increased their efforts to design and synthesize new dyes to customize absorption and emission properties. In particular, dyes containing one or more metallic centers allow for the construction of fairly sophisticated systems capable of selectively reacting to light of a given wavelength and behaving as molecular devices (photochemical molecular devices, PMDs).Theoretical tools able to predict and interpret the excited-state properties of organic and inorganic dyes allow for an efficient screening of photochemical centers. In this Account, we report recent developments defining a quantitative ab initio protocol (based on time-dependent density functional theory) for modeling dye spectral properties. In particular, we discuss the importance of several parameters, such as the methods used for electronic structure calculations, solvent effects, and statistical treatments. In addition, we illustrate the performance of such simulation tools through case studies. We also comment on current weak points of these methods and ways to improve them.
- SourceAvailable from: Pradip Kr. Bhattacharyya
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- "In recent years Time Dependent Density Functional Theory (TDDFT) has become a popular tool for computing the electronically excited states of molecules       . On the other hand density functional reactivity theory (DFRT) has been particularly impressive in estimating reactivity parameters of molecular systems . "
ABSTRACT: The effect of external electric field on the ground and few singlet excited states of phenyalanine are studied in the light of TDDFT (time dependent density functional theory) and DFRT (density functional reactivity theory). The excited state geometries are compared with the ground state ones. Sensitivity of the reactivity parameters such as total electronic energy, energy of the HOMO (highest occupied molecular orbital), global hardness (η), electrophilicity (ω) etc. towards the external electric fields are measured by varying the applied field strength. Variation of aromaticity of the ground and excited states are gauged in terms of nucleus independent chemical shift (NICS). Geometry, reactivity and aromaticity of the ground as well as excited states are responsive to the presence of external electric field.Computational and Theoretical Chemistry 02/2015; 1057. DOI:10.1016/j.comptc.2015.01.017 · 1.37 Impact Factor
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- "In this work, density functional theory (DFT) and time dependent DFT (TDDFT) calculations are performed without any symmetry constraints using Gaussian09 package . The polarized splitvalence 6-31G(d, p) basis sets are applied because they are sufficient for calculating the excitation of organic dyes . Introducing additional diffuse functions in basis sets generated negligible effects on the electron density and the accuracy of DFT and TDDFT results . "
ABSTRACT: In the design of novel dye sensitizers with good performance in dye sensitized solar cells, it is significantly important to understand how to tune the electronic structures and related properties of dye sensitizers by their terminal groups. Based upon the DFT and TDDFT calculated results of push-pull porphyrin sensitizers, named as YD20, YD21, YD22, 2Flu-ZnP-COOH, and 2Flu-ZnP-CN-COOH, the role of terminal groups in the modification of their electronic structures and related properties are investigated. It is found that the molecular orientation of adsorption and the driving force for electron injection can be changed by the substitution of electron-pull moiety. The data of electronic structures support that the pushing-electron capability of triphenylamino with two methoxyl substitutes is similar to that of the phenylamino group, but it is stronger than that of bis(3,3-dimethylfluorenyl) amine group. The pulling-electron capability of cyanoacrylic acid is stronger than that of carboxyl acid group. The analysis of molecular orbitals and transition configurations indicates that the triphenylamino with two methoxyl substitutes, phenylamino moieties, and bis(3,3-dimethylfluorenyl) amine groups are major chromophores for effective charge transfer excitation.Computational and Theoretical Chemistry 07/2014; 1039. DOI:10.1016/j.comptc.2014.04.035 · 1.37 Impact Factor
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- "Azo-, anthraquinone and indigo are the major chromophores found in commercial dyes. Dyes encompassing classes of molecules absorbing in the UV–visible part of the electromagnetic spectrum possess a wide range of applications, including coloring (e.g., textile, food, painting), energy production (e.g., photovoltaic, OLED), or medical purposes (e.g., diagnosis, drugs) . The dye chosen for present study is 3-methylamino-7-dimethylaminophenothiazin-5-ium chloride, also known as N,N,N'-Trimethylthionin and Azure B (AB). "
ABSTRACT: We present the characterizations of thermally induced third-order nonlinearity, optical power limiting and self-induced diffraction rings in Azure B dye. Nonlinear Measurements were carried out by employing the single beam z-scan technique. He-Ne laser operating in continuous wave mode at 633 nm wavelength was used as source of excitation. Azure B possess self-defocusing type of nonlinearity. Self-diffraction rings pattern were observed due to thermal lensing and change in the refractive index. Nonlinear absorption process in Azure B was due to the reverse saturable absorption. The nonlinear refractive index n2, the nonlinear absorption coefficient βeff and the third-order optical susceptibility χ(3) were found to be of the order 10-5esu, 10-2 cm/W and 10-7esu respectively. Azure B also displays good optical power handling capability of laser beam at the experimental wavelength, indicating the possible photonics device application such as all-optical power limiting.Optics & Laser Technology 02/2014; 62. DOI:10.1016/j.optlastec.2014.02.010 · 1.65 Impact Factor