Theoretical insight on hybrid nanocomposites of graphene quantum dot and carbazole-carbazole dyes as an efficient sensitizer of DSSC.

The feasibility of the hybrid nanocomposites of the graphene quantum dot (GQD) and carbazole-carbazole dyes as the efficient sensitizer of dye-sensitized solar cells (DSSC) is investigated. By using the first principles density functional theory (DFT), we fully optimize the geometrical structures of GQD, the carbazole-carbazole dyes, and their hybrid nanocomposites. The harmonic frequency analysis is used to confirm the energy stability of the optimized structures. The optical absorptions of the structures are calculated with the time-dependent DFT (TDDFT). Using the I-/I3- electrolyte and the conduction band minimum of TiO2 electrode as a sample, we examine the feasibility of the nanocomposites as the sensitizer of DSSC with the charge spatial separation and the molecular orbital energy levels of the nanocomposites. The results demonstrate all the considered nanocomposites have suitable energy levels of the frontier orbitals and significantly charge spatial separation. TDDFT results show the oscillator strengths of all nanocomposites demonstrate the obvious enhancement in the visible light region. Moreover, the appropriate open-circuit voltage value, the larger light-harvesting efficiency, and larger driving force are also identified for these nanocomposites. Therefore, the nanocomposites could be the more promising candidates of sensitizer for DSSC in comparison with the separate carbazole-carbazole dyes.

Theoretical studies on the feasibility of the hybrid nanocomposites of graphene quantum dot and phenoxazine-based dyes as an efficient sensitizer for dye-sensitized solar cells.

The feasibility of the hybrid nanocomposites of the graphene quantum dot (GQD) and the phenoxazine-based dyes as the efficient sensitizer of the dye-sensitized solar cell (DSSC) is investigated. Based on the first principles density functional theory (DFT), the geometrical structures of the separate GQDs, the phenoxazine-based dyes, and their hybridized nanocomposites are fully optimized. The energy stabilities of the obtained structures are confirmed by harmonic frequency analysis. The optical absorptions of the optimized structures are calculated with the time-dependent DFT (TDDFT). The feasibility of the nanocomposites as the sensitizer of DSSC is examined by the charge spatial separation, the molecular orbital energy levels of the nanocomposites and the I-/I3- electrolyte, and the conduction band minimum of TiO2 electrode. The results demonstrate that three of the eight considered nanocomposites satisfy the requirement of DSSC. Among them, GQD4-POXB with large LHE, high Voc, and enhancement absorption becomes the most promising candidate as a feasible sensitizer. These findings are helpful for the design of the sensitizer of DSSC or the solar energy harvesting materials with the nanocomposites.

Theoretical studies on the possible sensitizers of DSSC: Nanocomposites of graphene quantum dot hybrid phthalocyanine/tetrabenzoporphyrin/tetrabenzotriazaporphyrins/cis-tetrabenzodiazaporphyrins/tetrabenzomonoazaporphyrins and their Cu-metallated macrocycles.

The feasibility of nanocomposites of cir-coronene graphene quantum dot (GQD) with phthalocyanine, tetrabenzoporphyrin, tetrabenzotriazaporphyrins, cis-tetrabenzodiazaporphyrins, tetrabenzomonoazaporphyrins and their Cu-metallated macrocycles as a sensitizer of dye-sensitized solar cells (DSSC) are investigated. Based on the first principles density functional theory (DFT), the geometrical structures of the separate GQD and 10 macrocycles, and their hybridized nanocomposites are fully optimized. The energy stabilities of the obtained structures are confirmed by harmonic frequency analysis. The optical absorptions of the optimized structures are calculated with time-dependent DFT. The feasibility of the nanocomposites as the sensitizer of DSSC is examined by the charge spatial separation, the electron transfer, the molecular orbital energy levels of the nanocomposites and the electrolyte, and the conduction band minimum of TiO2 electrode. The results demonstrate that all the nanocomposites have enhanced absorptions in the visible light range, and their molecular orbital energies satisfy the requirement of sensitizers. However, only two of the ten considered nanocomposites demonstrate significantly charge spatial separation. The GQD-Cu-TBP is identified as the most favorable candidate sensitizer of DSSC by the most enhanced in optical absorption, obvious charge spatial separation, suitable LUMO energy levels and driving force for electron transfer, and low recombination rate of electron and hole.

The ground and low-lying excited states and feasibility of laser cooling for GaH+ and InH+ cations.

The potential energy curves and transition dipole moments of 12Σ+ and 12Π states of GaH+ and InH+ cations are performed by employing ab initio calculations. Based on the potential energy curves, the rotational and vibrational energy levels of the two states are obtained by solving the Schrödinger equation of nuclear movement. The spectroscopic parameters are deduced with the obtained rovibrational energy levels. The spin-orbit coupling effect of the 2Π states for both the GaH+ and InH+ cations are also calculated. The feasibility of laser cooling of GaH+ and InH+ cations are examined by using the results of the electronic and spectroscopic properties. The highly diagonal Franck-Condon factors and appropriate radiative lifetimes are determined by using the potential energy curves and transition dipole moments for the 2Π1/2, 3/2↔12Σ+ transitions. The results indicate that the 2Π1/2, 3/2↔12Σ+ transitions of both GaH+ and InH+ cations are appropriate for the close cycle transition of laser cooling. The optical scheme of the laser cooling is constructed for the GaH+ and InH+ cations.

Spectroscopic parameters of the low-lying electronic states and laser cooling feasibility of NH+ cation and NH- anion.

The potential energy curves and transition dipole moments of 12Σ+, 22Σ+, 12Π and 22Π states of NH+ cation and NH- anion are calculated by using multi-reference configuration interaction method and large all-electron basis sets. Based on the obtained potential energy curves, the rotational and vibrational energy levels of the states are obtained by solving the Schrödinger equation of nuclear movement. The calculated spectroscopic parameters for NH+ cation and NH- anion are in good agreement with available theoretical and experimental results. The spin orbit coupling effect of the 2Π states for both NH+ cation and NH- anion are calculated. The feasibility of laser cooling of the two molecules is examined by using the results of the molecular structure and spectroscopy. The highly diagonal Franck-Condon factors for the 12Π (v″=0)↔12Σ+ (v'=0) transition of NH+ and NH- are 0.821 and 0.999, while the radiative lifetimes of the 12Σ+ (v'=0) state for the two molecules are 384ns and 52.4ns, respectively. The results indicate that NH+ cation and NH- anion are good candidate molecules for laser cooling. The cooling scheme via Sisyphus process for the NH+ cation and NH- anion are proposed in the paper. The laser wavelengths for the close cycles of the absorption and radiation are also determined. Unfortunately, the potential energy curve of the ground state of the neutral NH molecule shows that the auto-detachment of NH- anion is possible, implying the optical scheme of laser cooling for NH- anion is not easy to achieve in the experiment although it has larger Franck-Condon factor.

The low-lying electronic states and optical schemes for the laser cooling of the BH+ and BH- ions.

The potential energy curves and transition dipole moments for the 12Σ+, 22Σ+, 12Π and 22Π electronic states of the two molecules are calculated using multi-reference configuration interaction and the large basis sets aug-cc-pwCV5Z. Based on the obtained potential energy curves, the rotational and vibrational energy levels of the states are obtained by solving the Schrödinger equation of nuclear motion, and the spectroscopic parameters are then obtained by fitting the energy levels to Dunham series expansions. The spin-orbit coupling effect of the 2Π states for both the BH+ cation and BH- anion are calculated. Highly diagonally distributed Franck-Condon factors are determined for the 12Σ+ (v″=0)↔12Π (v'=0) transition, ƒ00 (BH+)=0.943, while the Franck-Condon factors for the 12Π (v″=0)↔12Σ+ (v'=0) transition is ƒ00 (BH-)=0.942. Moreover, the radiative lifetime of 38.2ns for the excited 12Π state of the BH+ and 91.8ns for the 12Σ+ state of the BH- are obtained, which are short enough for rapid laser cooling. A three-step optical scheme of the laser cooling is constructed for either the BH+ cation or the BH- anion.

Ab initio studies on the spin-forbidden cooling transitions of the LiRb molecule.

The spin-forbidden cooling of the LiRb molecule is investigated based on ab initio quantum chemistry calculations. The multireference configuration interaction method is used to generate the potential energy curves (PECs) of the ground state X(1)Σ(+) and the low-lying excited states a(3)Σ(+), B(1)Π, and b(3)Π. The spin-orbit coupling effects for the PECs and the transition dipole moments (TDMs) between the X(1)Σ(+), b(3)Π and a(3)Σ(+) states are also calculated. The analytical functions for the PECs are deduced. The rovibrational energy levels, the spectroscopic parameters and the Franck-Condon factors (FCF) are determined by solving the Schrödinger equation of nuclear movement with the obtained analytical functions. The b(3)Π0 ↔ X(1)Σ(+) and b(3)Π1 ↔ X(1)Σ(+) transitions have highly diagonal distributed FCFs and non-zero TDMs, demonstrating that the LiRb molecule could be a very promising candidate for laser cooling. Therefore, a three-cycle laser cooling scheme for the molecule has been proposed based on these two spin-forbidden transitions. Using the radiative lifetime and linewidth calculated from the obtained TDM functions, we present further analysis of the cooling of LiRb and the corresponding KRb molecule. The transition b(3)Π0 ↔ X(1)Σ(+) is found to be a practical transition to cool the LiRb molecule, and a sub-microkelvin cool temperature could be reached for the KRb molecule using a similar laser cooling scheme.

Analytic functions for potential energy curves, dipole moments, and transition dipole moments of LiRb molecule.

The analytic potential energy functions (APEFs) of the X(1)Σ(+), 2(1)Σ(+), a(3)Σ(+), and 2(3)Σ(+) states of the LiRb molecule are obtained using Morse long-range potential energy function with damping function and nonlinear least-squares method. These calculations were based on the potential energy curves (PECs) calculated using the multi-reference configuration interaction (MRCI) method. The reliability of the APEFs is confirmed using the curves of their first and second derivatives. By using the obtained APEFs, the rotational and vibrational energy levels of the states are determined by solving the Schrödinger equation of nuclear movement. The spectroscopic parameters, which are deduced using Dunham expansion, and the obtained rotational and vibrational levels are compared with the reported theoretical and experimental values. The correlation effect of the electrons of the inner shell remarkably improves the results compared with the experimental spectroscopic parameters. For the first time, the APEFs for the dipole moments and transition dipole moments of the states have been determined based on the curves obtained from the MRCI calculations.

Ab initio study on the ground and low-lying states of BAlk (Alk = Li, Na, K) molecules.

The potential energy curves (PECs) and dipole moment functions of (1)Π, (3)Π, (1)Σ(+), and (3)Σ(+) states of BAlk (Alk = Li, Na, K) are calculated using multireference configuration interaction method and large all-electron basis sets. The effects of inner-shell correlation electron for BAlk are considered. The ro-vibrational energy levels are obtained by solving the Schrödinger equation of nuclear motion based on the ab initio PECs. The spectroscopic parameters are determined from the ro-vibrational levels with Dunham expansion. The PECs are fitted into analytical potential energy functions using the Morse long-range potential function. The dipole moment functions for the states of BAlk are presented. The transition dipole moments for (1)Σ(+) → (1)Π and (3)Σ(+) → (3)Π states of BAlk are obtained. The interactions between the outermost electron of Alk and B 2p electrons for (1)Π, (3)Π, (1)Σ(+), and (3)Σ(+) states are also analyzed, respectively.

An ab initio study of the ground and low-lying excited states of KBe with the effect of inner-shell electrons.

The potential energy curves (PECs) of 1(2)Σ(+), 2(2)Σ(+), 1(2)Π, and 2(2)Π states of KBe are calculated using multireference configuration interaction method and large all-electron basis sets. Four sets of frozen core orbitals (FCOs) are considered to examine the effect of inner-shell correlation electrons on the molecular properties. The ro-vibrational energy levels are obtained by solving the Schrödinger equation of nuclear motion based on the ab initio PECs. The spectroscopic parameters are determined from the ro-vibrational levels with Dunham expansion. The PECs are fitted into analytical potential energy functions using the Morse long-range potential function. The dipole moment functions of the states for KBe calculated with different FCOs are presented. The transition dipole moments for KBe between 1(2)Σ(+) and 2(2)Σ(+) states, 1(2)Π and 1(2)Σ(+) states, and 2(2)Π and 1(2)Σ(+) states are also obtained.

Draft genome sequence of Enterobacter cloacae subsp. cloacae strain 08XA1, a fecal bacterium of giant pandas.

Enterobacter cloacae, a common pathogenic bacterium, is a Gram-negative bacillus. We analyzed the draft genome of Enterobacter cloacae subsp. cloacae strain 08XA1 from the feces of a giant panda in China. Genes encoding a ß-lactamase and efflux pumps, as well as other factors, have been found in the genome.

Analytical potential energy functions and spectroscopic properties for the ground and low-lying excited states of KRb.

The potential energy curves (PECs) of the ground state X(1)Σ(+) and two low-lying excited states 1(3)Σ(+) and 1(3)П of KRb molecule have been calculated using the multireference configuration interaction method and the effective core potential basis set. The PECs are fitted into analytical potential energy functions (APEFs) using the Morse long-range potential. The spectroscopic parameters for the states are determined using the analytical derivatives of APEFs. The vibrational energy levels have been calculated by solving the radial Schrödinger equation of nuclear motion based on the APEFs, and compared with the theoretical and experimental works available at present.