Adsorption of volatile organic compounds (VOCs) which are a class of air pollutants affecting the environment and human health is considered as the favourable technology for enrichment, separation and utilization of VOCs. In the present work, the adsorption properties of air polluting carbocyclic and heterocyclic VOCs such as toluene, p-xylene and indole onto pristine/defected nanographene (with and without dopants) are investigated using density functional theory (DFT). Adsorption of indole is higher (-0.544 to -1.786 eV) in pristine/defected nanographene (with and without dopant) than p-xylene and toluene. The reactivity of defect on adsorption of VOCs is found high for indole with defected nanographene (DG) and toluene with DG-N indicating the influence of sheet type for adsorption rely on the type of the VOCs adsorbate. The charge transfer and type of interaction between the sheet and VOCs are interpreted using Hirshfeld charge analysis, QTAIM and RDG analysis. The influence of VOCs adsorption is high on the electronegativity and electrophilicity index of the pristine/defected nanographene whereas energy gap and hardness show less influence. The noticeable changes in the TDOS and energy gap on adsorption of VOCs with respect to the type of sheet infers that the doped defected sheet have high affinity than the pristine sheet moreover, the suitable sheet for adsorption of VOCs depends on the type of VOCs adsorbate.
A new CBD-CC-E spectral similarity scale is proposed to optimize computer-simulated UV?vis spectra. The scale was tested using the S1?S0 spectrum of the dithienyl-diketopyrrolopyrrole molecule (DPP2T), an important building block for manufacturing materials for optoelectronic applications. Our results indicate that the spectrum calculated at M06/6-311++G(d,p) level was the one that best reproduced the intensity and shape features of the experimental spectrum, while CAM-B3LYP/6-311++G(d,p) was the one that best reproduced the energy. The CBD-CC-E scale makes the comparison between computer-simulated and experimental spectra statistically based, allowing a systematic and automated choice of the theory level whose calculated spectrum best reproduces the shape, intensity or energy of the experimental UV?vis spectrum.
Belonging to the family of pterins, which are common chromophores in several bio-organisms, xanthopterin has been shown experimentally (Plotkin et al., 2010) to have the ability of acting as a light-harvesting molecule. In the present study, multiconfigurational second-order perturbation theory is used to determine the stability of distinct amino/imino and lactam/lactim tautomers and the absorption and emission spectroscopic characteristics, electron donor and acceptor properties and the electron and charge transfer efficiencies via π-stacking. The lactam–lactam form 3H5H (and in a lesser extent 1H5H) is predicted to have the most appropriate intrinsic characteristics for the light-harvesting properties of xanthopterin, since it is the most stable isomer predicted for the gas phase and estimated for polar environments, absorbs solar light at longer wave lengths, has relatively low donor properties and the presence of the keto groups, instead of enol, increases the efficiency for energy transfer through excimer-like interactions.
The adsorption and dissociation of dinitrogen on transition metal (Ta, W and Re) doped MgO(100) surface has been studied employing density functional theory. It is found that all these transition metals (TM) on MgO(100) surface are capable of adsorbing dinitrogen (N-2), however there is no dissociative adsorption of N-2 on single transition metal dopant. When two TM atoms are doped on MgO(100) surface, dissociative adsorption of dinitrogen occurs in all the three cases. Whether the dissociation is spontaneous or is it associated with activation barrier depends on the orientation of N-2 molecule approaching the dopant site.