Interaction investigation of single and multiple carbon monoxide molecules with Fe-, Ru-, and Os-doped single-walled carbon nanotubes by DFT study: applications to gas adsorption and detection nanomaterials.

Due to the large surface area and unique electronic property, single-wall carbon nanotube (SWCNT) is being used for adsorption and detection nanomaterials, which can be used to reduce the CO pollution effect on the environment. In the present work, the adsorptions of single and multiple CO molecules on pristine and transition metal (TM = Fe-, Ru-, and Os)-doped SWCNT were investigated in terms of geometric, energetic, and electronic properties using density functional theory calculation. Calculated results display that the adsorption of CO molecule on the SWCNTs is energetically favorable. The TM-doped SWCNT are more highly interactive to CO adsorption than that of pristine SWCNT. An Os-doped SWCNT displays the strongest interaction with single and multiple CO molecules comparing with the Fe- and Ru-doped SWCNT. The TM doping on SWCNT can induce the charge transfer between CO molecule and the SWCNT. The energy gap and density of state are clearly changed when CO molecule interacts with TM-doped SWCNT, resulting in dramatic changes of their electronic properties. Therefore, TM-doped SWCNT are possibly used as potential CO storages/absorbents or sensor material for CO detection in the environment. Graphical abstract.

Photophysical properties and photochemistry of EE-, EZ-, and ZZ-1,4-dimethoxy-2,5-bis[2-(thien-2-yl)ethenyl] benzene in solution: theory and experiment.

Photophysical properties and photoisomerization of 1,4-dimethoxy-2,5-bis[2-(thien-2-yl)ethenyl] benzene (DMTB) have been investigated for the EE-, EZ-, and ZZ- stereoisomers. The EE-DMTB was prepared, and the absorption/fluorescence spectra of EE- isomer as well as transient spectra in photoisomerization among three isomers were observed. Absorption and fluorescence spectra of three isomers were analyzed by the symmetry-adapted cluster-configuration interaction (SAC-CI) and time-dependent density functional theory (TDDFT) methods. The characteristics of the absorption spectra of three isomers were satisfactorily reproduced by the direct SAC-CI and TDDFT methods in both peak position and intensity. The relative stability of three isomers and the photoisomerization among these isomers were also examined theoretically. The ground (S(0)) and first excited state (S(1)) geometries were calculated by the DFT/TDDFT method with the M06HF functional, and the calculated S(0) structures of EE- and ZZ- isomers agreed well with those of the X-ray structures. The geometry relaxation in the S(1) state was interpreted with regard to the excitation character. The solvent effect in the absorption and fluorescence spectra was examined by the polarizable continuum model (PCM) and was found to be 0.05-0.20 eV, reflecting the charge polarization. The results show that the photophysical properties of DMTB can be controlled with the conformation constraint and also indicate the possibility of a photofunctional molecular device such as a switching function.