Browsing by Author "Koivisto, Bryan D."
Now showing 1 - 7 of 7
Results Per Page
Sort Options
- ItemBipodal dyes with bichromic triphenylamine architectures for use in dye- sensitized solar cell applications(2018) Abdi, Omar K.; Fischer, Benjamin J. D.; Al-Faouri, Tamara; Buguis, Francis L.; Devgan, Hardeep S.; Schott Verdugo, Eduardo Enrique; Zarate, Ximena; Koivisto, Bryan D.
- ItemRare-earth-based metal-organic frameworks with improved visible-light-harvesting properties: a quantum chemistry study(2023) Hidalgo-Rosa, Yoan; Saavedra-Torres, Mario; Koivisto, Bryan D.; Treto-Suarez, Manuel A.; Paez-Hernandez, Dayan; Zarate, Ximena; Schott, EduardoThis report proves that improving the visible-light-harvesting properties in rare-earth-based metal-organic frameworks (RE-MOFs) (labelled as RE-UiO-66, UiO = University of Oslo MOFs), with the aim of performing as potential visible-light-driven photocatalysts, is achievable. Thus, the design of MOFs with specific applications, especially those involving sunlight and material interactions, represents a growing field, which has been addressed in the herein work using quantum mechanical tools. We achieved to relate the light absorption properties with the structure in systems Y-UiO-66, Sc-UiO-66 and La-UiO-66, by evaluating the inclusion of well-known electron donor substituents in the structure of the 1,4-benzenedicarboxylate (BDC) linker (i.e. BDC-R, R: -CH3, -OH, -SH and -NH2). The electronic structure and optical properties of Y-UiO-66 were rigorously investigated using computational techniques combining molecular and periodic density functional theory (DFT) calculations. As a remarkable result, it was shown that including the groups -SH or -NH2 in the BDC linker, induced a shift in the absorption bands to the visible region (>= 400 nm). Hence, a group of new RE-MOFs materials with optimal structural and photocatalytic properties is proposed. This could encourage researchers to prepare these new materials to be tested in photocatalysis, such as cleaving the C-H bond, water splitting or photocatalytic degradation of organic contaminants.
- ItemRegioselective C-H Activation of Cyclometalated Bis-Tridentate Ruthenium Complexes(2011) Muise, Stacy S. R.; Severin, Holly A.; Koivisto, Bryan D.; Robson, Kiyoshi C. D.; Schott Verdugo, Eduardo Enrique; Berlinguette, Curtis P.
- ItemSystematic Modulation of a Bichromic Cyclometalated Ruthenium(II) Scaffold Bearing a Redox-Active Triphenylamine Constituent(2011) Robson, Kiyoshi C. D.; Sporinova, Barbora; Koivisto, Bryan D.; Schott Verdugo, Eduardo Enrique; Brown, Douglas G.; Berlinguette, Curtis P.
- ItemThe development of Au-titania photoanode composites toward semiflexible dye-sensitized solar cells(2023) Castillo-Rodriguez, Judith; Ortiz, Pedro D.; Mahmood, Reeda; Gossage, Robert A.; Llanos, Jaime; Espinoza, Dario; Zarate, Ximena; Koivisto, Bryan D.; Schott, EduardoConsidering the widespread use of windows in modern urban landscapes, converting these substrates into photovoltaic devices would remarkably impact modern energy generation. A flexible dye-sensitized solar cell (DSSC) architecture is preferred for such applications. A key component of the DSSC is the dye-sensitized photoanode. Herein, we examine different nanoparticle composites within the semiconductor anode formulation and their effect on device performance. Mesoporous titania particles (TiO2) modified with Au-nanoparticles (TiO2@AuNPs) were synthesized using precipitation strategies to assess the solvent effect on the particle size and the efficiency of the devices. The materials were then fully characterized through SEM, XRD, and DRS before and after thermal treatment. A paste prepared from the synthesized semiconductors was applied onto the substrate using the doctor blading technique. The use of high thermal treatment for glass substrates (HTT), low temperature thermal treatment (LTT), and LTT combined with 2 h of UV curing (LTT_UV) was explored. In the case of ITO/PET (flexible substrate) only low temperature thermal treatment were used (LTT and LTT_UV). After characterization (XRD and DRS), the anodes were loaded using a metal-free dye. To complete the comparison, several groups of cells were characterized: considering solvent (EtOH and EtOH:H2O), thermal treatment (HTT, LTT, and LTT_UV), and semiconductor material (TiO2 and TiO2@AuNP). Rigid (glass anode-glass cathode) and semiflexible (flexible anode-glass cathode) DSSCs were obtained with efficiencies from 0.03% to 2.4%, with a substantial performance difference seen using different thermal treatments, and a mild to low effect on semiconductor composition and the used substrate.
- ItemTunable optical properties of isoreticular UiO-67 MOFs for photocatalysis: a theoretical study(2024) Treto Suárez, Manuel A.; Hidalgo Rosa, Yoan; Saavedra Torres, Mario; Koivisto, Bryan D.; Mena Ulecia, Karel; Páez Hernández, Dayan; Zarate, Ximena; Schott Verdugo, EduardoA theoretical study of the reported photocatalytic systems based on Zr-based MOF (UiO-67) with biphenyl-4,4 '-dicarboxylic acid (bpdc) and 2,2 '-bipyridine-5,5 '-dicarboxylic acid (bpydc) as linkers was performed. Quantum chemical calculations were carried out to understand the optical properties of the materials and to facilitate the rational design of new UiO-67 derivatives with potentially improved features as photocatalysts under ambient conditions. Hence, the effect of the structural modifications on the optical properties was studied considering different designs based on the nature of the linkers: in 1 only the bpdc linker was considered, or the mixture 1 : 1 between bpdc and bpydc linkers (labeled as 1A). Also, substituents R, -NH2, and -SH, were included in the 1A MOF only over the bpdc linker (labeled as 1A-bpdc-R) and on both bpdc and bpydc linkers (labeled as 1A-R). Thus a family of six isoreticular UiO-67 derivatives was theoretically characterized using Density Functional Theory (DFT) calculations on the ground singlet (S0) and first excited states (singlet and triplet) using Time-Dependent Density Functional Theory (TD-DFT), multiconfigurational post-Hartree-Fock method via Complete Active Space Self-Consistent Field (CASSCF). In addition, the use of periodic DFT calculations suggest that the energy transfer (ET) channel between bpdc and bpydc linkers might generate more luminescence quenching of 1A when compare to 1. Besides, the results suggest that the 1A-R (R: -SH and NH2) can be used under ambient conditions; however, the ET exhibited by 1A, cannot take place in the same magnitude in these systems. These ET can favor the photocatalytic reduction of a potential metal ion, that can coordinate with the bpydc ligand, via LMCT transition. Consequently, the MOF might be photocatalytically active against molecules of interest (such as H2, N2, CO2, among others) with photo-reduced metal ions. These theoretical results serve as a useful tool to guide experimental efforts in the design of new photocatalytic MOF-based systems., A theoretical computational protocol was performed to understand the optical properties, the deactivation mechanisms, and the substituent effect for a photocatalytic MOF-based system.
- ItemTunning the optical properties of a photocatalytic metal-organic framework by means of molecular modelling(2023) Treto-Suarez, Manuel A.; Hidalgo-Rosa, Yoan; Ulecia, Karel Mena; Paez-Hernandez, Dayan; Koivisto, Bryan D.; Zarate, Ximena; Schott, EduardoA theoretical study of reported isostructural metal-organic frameworks (MOFs) based on MIL-125-Ti4+ was performed to understand the optical properties and facilitate the rational design of new materials with potentially improved features as photocatalysts. The experimentally tested MOFs (MIL-125-Ti4+ labeled as M) were functionalized with -NH2, -CH3, and -OH substituents on the 1,4-benzene-dicarboxylate (BDC) linker (labeled as M-NH2, M-CH3, and M-OH, respectively), generating a broadened light-harvesting of the MOF and an improvement of the N-2 conversion rate. The M-NH2 showed the highest visible light absorption and N-2 photocatalysis efficiency experimentally. This substituent effect was theoretically studied via Density Functional Theory (DFT) calculations on the ground singlet (S-0) and first excited state (singlet and triplet) using Time-Dependent Density Functional Theory (TD-DFT), the Morokuma-Ziegler energy decomposition scheme, and Natural Orbital of Chemical Valence (NOCV) analysis. These tools allowed for the reproduction of the optical properties and performance in good agreement with the experiment and highlight that the N-2 conversion rate increases as the donor character of the R group improve. This effect is a result of the stabilization of the Occupied Molecular Orbitals (localized on the BDC linker), a decrease in the charge recombination, and by an increase of charge flow to the metal center favoring the photocatalytic Ti4+/Ti3+ reduction (via ligand to metal charge transfer (LMCT) transition). These systems also display a metal-ligand charge transfer (MLCT) process in the excited state favoring the emission localized in the BDC linker, which was confirmed via Complete Active Space Self-Consistent Field (CASSCF) calculation. Finally, through CASSCF, it was possible to propose two new isoreticular structures, with the -SH and -NO2 substituents (labeled as M-SH and M-NO2), with the -SH variant exhibiting optical and photocatalytic properties that could rival M with -NH2 substitution.