| 1. |
- Liu, Haiyang, et al.
(author)
-
A simple Schiff base as dual-responsive fluorescent sensor for bioimaging recognition of Zn2+ and Al3+ in living cells
- 2018
-
In: Journal of materials chemistry. B. - : ROYAL SOC CHEMISTRY. - 2050-750X .- 2050-7518. ; 6:34, s. 5435-5442
-
Journal article (peer-reviewed)abstract
- A simple Schiff base fluorescent sensor (BDNOL) was synthesized from the reaction of picolinohydrazide and 4-(diethylamino)salicylaldehyde, and developed for selective detection of Al3+ and Zn2+. This non-fluorescent sensor displayed obvious fluorescence enhancement after binding to Al3+/Zn2+ ions with high sensitivity and selectivity, accompanied by obvious fluorescence emission enhancement (504 nm for Al3+ and 575 nm for Zn2+). The detection limits were found to be 8.30 x 10(-8) M for Al3+ and 1.24 x 10(-7) M for Zn2+. The binding mechanisms between BDNOL and Al3+/Zn2+ ions were supported by H-1 NMR and HR-MS analysis, and a density functional theory (DFT) study. The sensing behavior was also studied with molecular logic functions of OR, AND, and NOT gates. Furthermore, the fluorescent sensor was successfully used to recognize Al3+ and Zn2+ in living cells, suggesting that this simple biosensor has great potential in biological imaging applications.
|
|
| 2. |
- Yang, Hao, et al.
(author)
-
Intramolecular hydroxyl nucleophilic attack pathway by a polymeric water oxidation catalyst with single cobalt sites
- 2022
-
In: Nature Catalysis. - : Springer Nature. - 2520-1158. ; 5:5, s. 414-429
-
Journal article (peer-reviewed)abstract
- Exploration of efficient water oxidation catalysts (WOCs) is the primary challenge in conversion of renewable energy into fuels. Here we report a molecularly well-defined heterogeneous WOC with Aza-fused, pi-conjugated, microporous polymer (Aza-CMP) coordinated single cobalt sites (Aza-CMP-Co). The single cobalt sites in Aza-CMP-Co exhibited superior activity under alkaline and near-neutral conditions. Moreover, the molecular nature of the isolated catalytic sites makes Aza-CMP-Co a reliable model for studying the heterogeneous water oxidation mechanism. By a combination of experimental and theoretical results, a pH-dependent nucleophilic attack pathway for O-O bond formation was proposed. Under alkaline conditions, the intramolecular hydroxyl nucleophilic attack (IHNA) process with which the adjacent -OH group nucleophilically attacks Co4+=O was identified as the rate-determining step. This process leads to lower activation energy and accelerated kinetics than those of the intermolecular water nucleophilic attack (WNA) pathway. This study provides significant insights into the crucial function of electrolyte pH in water oxidation catalysis and enhancement of water oxidation activity by regulation of the IHNA pathway.
|
|
| 3. |
- Yang, Hao, et al.
(author)
-
Monolithic FAPbBr3 Photoanode for Photoelectrochemical Water Oxidation with Ultralow-Onset-Potential
-
Other publication (other academic/artistic)abstract
- Despite considerable research efforts on photoelectrochemical (PEC) water splitting over the past few decades, its practical application is still impeded by the lack of efficient, stable, and scalable photoelectrodes. Herein, we demonstrate the facile fabrication of a metal-halide perovskite-based photoanode for PEC water oxidation. A hole transport material-free and precious metal-free FAPbBr3 photovoltaic (PV) device is fabricated for the first time to examine the charge separation performance of the FAPbBr3 absorber. With a planar structure using mesoporous carbon as a hole-conducting layer, the device achieved a solar-to-electrical power conversion efficiency of 9.2% and a Voc of 1.4 V. The solar cell architecture is successfully applied to build a monolithic photoanode with the FAPbBr3 absorber, carbon/graphite conductive protection layer, and NiFe catalyst layers for direct photo-driven water oxidation. With suitable energy band alignment and minimal contact loss, the photoanode delivers an ultralow onset potential below 0 V versus a reversible hydrogen electrode and a high applied bias photon-to-current efficiency of 8.5%. Stable operation exceeding 100 h under constant solar illumination is successfully reached by the application of UV filter protection. A detailed photothermal investigation confirms that the photothermal effect can improve the overall performance of the perovskite photoanode. The results in this report are of great significance in guiding the further development of PV material-based photoelectrodes for solar fuel applications.
|
|
| 4. |
- Yang, Hao, et al.
(author)
-
Monolithic FAPbBr3 photoanode for photoelectrochemical water oxidation with low onset-potential and enhanced stability
- 2023
-
In: Nature Communications. - : Springer Nature. - 2041-1723. ; 14:1
-
Journal article (peer-reviewed)abstract
- Despite considerable research efforts on photoelectrochemical water splitting over the past decades, practical application faces challenges by the absence of efficient, stable, and scalable photoelectrodes. Herein, we report a metal-halide perovskite-based photoanode for photoelectrochemical water oxidation. With a planar structure using mesoporous carbon as a hole-conducting layer, the precious metal-free FAPbBr3 photovoltaic device achieves 9.2% solar-to-electrical power conversion efficiency and 1.4 V open-circuit voltage. The photovoltaic architecture successfully applies to build a monolithic photoanode with the FAPbBr3 absorber, carbon/graphite conductive protection layers, and NiFe catalyst layers for water oxidation. The photoanode delivers ultralow onset potential below 0 V versus the reversible hydrogen electrode and high applied bias photon-to-current efficiency of 8.5%. Stable operation exceeding 100 h under solar illumination by applying ultraviolet-filter protection. The photothermal investigation verifies the performance boost in perovskite photoanode by photothermal effect. This study is significant in guiding the development of photovoltaic material-based photoelectrodes for solar fuel applications.
|
|
| 5. |
- Biaobiao, Zhang, et al.
(author)
-
Modifying Ru-bda Backbone with Steric Hindrance and Hydrophilicity: Influence of Secondary Coordination Environments on Water-Oxidation Mechanism.
-
Journal article (other academic/artistic)abstract
- Understanding the seven coordination and O−O coupling pathway of the distinguished Ru-bda catalysts is essential for the development of next generation efficient water-oxidation catalysts based on earth-abundant metals. This work reports the synthesis, characterization and catalytic properties of a monomeric ruthenium catalyst Ru-bnda (H2bnda = 2,2'-bi(nicotinic acid)-6,6'-dicarboxylic acid) featuring steric hindrance and enhanced hydrophilicity on the backbone. Combining experimental evidence with systematic density functional theory calculations on the Ru-bnda and related catalysts Ru-bda, Ru-pda and Ru-biqa, we emphasized that seven coordination clearly determines presence of RuV=O with high spin density on the ORuV=O atom, i.e. oxo with radical properties, which is one of the necessary conditions for reacting through the O−O coupling pathway. However, an additional factor to make the condition sufficient is the favorable intermolecular face-to-face interaction for the generation of the pre-reactive [RuV=O···O=RuV], which is significantly influenced by the secondary coordination environments. This work provides a new understanding of the structure-activity relationship of water-oxidation catalysts and their potential to adopt I2M pathway for O−O bond formation.
|
|
| 6. |
- Deyev, Sergey M., et al.
(author)
-
Influence of the Position and Composition of Radiometals and Radioiodine Labels on Imaging of Epcam Expression in Prostate Cancer Model Using the DARPin Ec1
- 2021
-
In: Cancers. - : MDPI AG. - 2072-6694. ; 13:14
-
Journal article (peer-reviewed)abstract
- Simple Summary Metastasis-targeting therapy might improve outcomes in oligometastatic prostate cancer. Epithelial cell adhesion molecule (EpCAM) is overexpressed in 40-60% of prostate cancer cases and might be used as a target for specific delivery of toxins and drugs. Radionuclide molecular imaging could enable non-invasive detection of EpCAM and stratification of patients for targeted therapy. Designed ankyrin repeat proteins (DARPins) are scaffold proteins, which can be selected for specific binding to different targets. The DARPin Ec1 binds strongly to EpCAM. To determine an optimal design of Ec1-based probes, we labeled Ec1 at two different positions with four different nuclides (Ga-68, In-111, Co-57 and I-125) and investigated the impact on Ec1 biodistribution. We found that the C-terminus is the best position for labeling and that In-111 and I-125 provide the best imaging contrast. This study might be helpful for scientists developing imaging probes based on scaffold proteins. The epithelial cell adhesion molecule (EpCAM) is intensively overexpressed in 40-60% of prostate cancer (PCa) cases and can be used as a target for the delivery of drugs and toxins. The designed ankyrin repeat protein (DARPin) Ec1 has a high affinity to EpCAM (68 pM) and a small size (18 kDa). Radiolabeled Ec1 might be used as a companion diagnostic for the selection of PCa patients for therapy. The study aimed to investigate the influence of radiolabel position (N- or C-terminal) and composition on the targeting and imaging properties of Ec1. Two variants, having an N- or C-terminal cysteine, were produced, site-specifically conjugated to a DOTA chelator and labeled with cobalt-57, gallium-68 or indium-111. Site-specific radioiodination was performed using ((4-hydroxyphenyl)-ethyl)maleimide (HPEM). Biodistribution of eight radiolabeled Ec1-probes was measured in nude mice bearing PCa DU145 xenografts. In all cases, positioning of a label at the C-terminus provided the best tumor-to-organ ratios. The non-residualizing [I-125]I-HPEM label provided the highest tumor-to-muscle and tumor-to-bone ratios and is more suitable for EpCAM imaging in early-stage PCa. Among the radiometals, indium-111 provided the highest tumor-to-blood, tumor-to-lung and tumor-to-liver ratios and could be used at late-stage PCa. In conclusion, label position and composition are important for the DARPin Ec1.
|
|
| 7. |
- Ding, Haozhong, et al.
(author)
-
HER2-Specific Pseudomonas Exotoxin A PE25 Based Fusions : Influence of Targeting Domain on Target Binding, Toxicity, and In Vivo Biodistribution
- 2020
-
In: Pharmaceutics. - : MDPI AG. - 1999-4923. ; 12:4
-
Journal article (peer-reviewed)abstract
- The human epidermal growth factor receptor 2 (HER2) is a clinically validated target for cancer therapy, and targeted therapies are often used in regimens for patients with a high HER2 expression level. Despite the success of current drugs, a number of patients succumb to their disease, which motivates development of novel drugs with other modes of action. We have previously shown that an albumin binding domain-derived affinity protein with specific affinity for HER2, ADAPT(6), can be used to deliver the highly cytotoxic protein domain PE25, a derivative of Pseudomonas exotoxin A, to HER2 overexpressing malignant cells, leading to potent and specific cell killing. In this study we expanded the investigation for an optimal targeting domain and constructed two fusion toxins where a HER2-binding affibody molecule, Z(HER2:2891), or the dual-HER2-binding hybrid Z(HER2:2891)-ADAPT(6) were used for cancer cell targeting. We found that both targeting domains conferred strong binding to HER2; both to the purified extracellular domain and to the HER2 overexpressing cell line SKOV3. This resulted in fusion toxins with high cytotoxic potency toward cell lines with high expression levels of HER2, with EC50 values between 10 and 100 pM. For extension of the plasma half-life, an albumin binding domain was also included. Intravenous injection of the fusion toxins into mice showed a profound influence of the targeting domain on biodistribution. Compared to previous results, with ADAPT(6) as targeting domain, Z(HER2:2891) gave rise to further extension of the plasma half-life and also shifted the clearance route of the fusion toxin from the liver to the kidneys. Collectively, the results show that the targeting domain has a major impact on uptake of PE25-based fusion toxins in different organs. The results also show that PE25-based fusion toxins with high affinity to HER2 do not necessarily increase the cytotoxicity beyond a certain point in affinity. In conclusion, Z(HER2:2891) has the most favorable characteristics as targeting domain for PE25.
|
|
| 8. |
- Fan, Lizhou, et al.
(author)
-
Molecular Functionalization of NiO Nanocatalyst for Enhanced Water Oxidation by Electronic Structure Engineering
- 2020
-
In: ChemSusChem. - : Wiley. - 1864-5631 .- 1864-564X. ; 13:22, s. 5901-5909
-
Journal article (peer-reviewed)abstract
- Tuning the local environment of nanomaterial-based catalysts has emerged as an effective approach to optimize their oxygen evolution reaction (OER) performance, yet the controlled electronic modulation around surface active sites remains a great challenge. Herein, directed electronic modulation of NiO nanoparticles was achieved by simple surface molecular modification with small organic molecules. By adjusting the electronic properties of modifying molecules, the local electronic structure was rationally tailored and a close electronic structure-activity relationship was discovered: the increasing electron-withdrawing modification readily decreased the electron density around surface Ni sites, accelerating the reaction kinetics and improving OER activity, and vice versa. Detailed investigation by operando Raman spectroelectrochemistry revealed that the electron-withdrawing modification facilitates the charge-transfer kinetics, stimulates the catalyst reconstruction, and promotes abundant high-valent gamma-NiOOH reactive species generation. The NiO-C(6)F(5)catalyst, with the optimized electronic environment, exhibited superior performance towards water oxidation. This work provides a well-designed and effective approach for heterogeneous catalyst fabrication under the molecular level.
|
|
| 9. |
- Fan, Lizhou, et al.
(author)
-
Promoting the Fe(VI) active species generation by structural and electronic modulation of efficient iron oxide based water oxidation catalyst without Ni or Co
- 2020
-
In: Nano Energy. - : Elsevier BV. - 2211-2855 .- 2211-3282. ; 72
-
Journal article (peer-reviewed)abstract
- Fe is considered as a promising alternative for OER catalysts owing to its high natural abundance and low cost. Due to the low conductivity and sluggish catalytic kinetics, the catalytic efficiency of Fe-rich catalysts is far from less abundant Ni, Co-rich alternatives and has been hardly improved without the involvement of Ni or Co. The lower activity of Fe-rich catalysts renders the real active center of state-of-the-art NiFe, CoFe catalyst in long-term scientific debate, despite of detection of Fe-based active intermediates in these catalysts during catalytic process. In the present work, we fabricated a series of sub-5 nm Fe1-yCryOx nanocatalysts via a simple solvothermal method, achieving systematically promoted high-valent Fe(VI) species generation by structural and electronic modulation, displaying highly active OER performance without involvement of Ni or Co. Detailed investigation revealed that the high OER activity is related to the ultrasmall nanoparticle size that promotes abundant edge- and corner-site exposure at catalyst surface, which involves in OER as highly reactive site; and the incorporated Cr ions that remarkably accelerate the charge transfer kinetics, providing an effective conduit as well as suitable host for high-valent active intermediate. This work reveals the structural prerequisites for efficient Fe-rich OER catalyst fabrication, inspiring deeper understanding of the structure-activity relationship as well as OER mechanism of Fe-based catalysts.
|
|
| 10. |
- Garousi, Javad, et al.
(author)
-
Experimental HER2-Targeted Therapy Using ADAPT6-ABD-mcDM1 in Mice Bearing SKOV3 Ovarian Cancer Xenografts : Efficacy and Selection of Companion Imaging Counterpart
- 2022
-
In: Pharmaceutics. - : MDPI. - 1999-4923. ; 14:8
-
Journal article (peer-reviewed)abstract
- Overexpression of the human epidermal growth factor receptor 2 (HER2) in breast and gastric cancer is exploited for targeted therapy using monoclonal antibodies and antibody-drug conjugates. Small engineered scaffold proteins, such as the albumin binding domain (ABD) derived affinity proteins (ADAPTs), are a promising new format of targeting probes for development of drug conjugates with well-defined structure and tunable pharmacokinetics. Radiolabeled ADAPT6 has shown excellent tumor-targeting properties in clinical trials. Recently, we developed a drug conjugate based on the HER2-targeting ADAPT6 fused to an albumin binding domain (ABD) for increased bioavailability and conjugated to DM1 for cytotoxic action, designated as ADAPT6-ABD-mcDM1. In this study, we investigated the therapeutic efficacy of this conjugate in mice bearing HER2-expressing SKOV3 ovarian cancer xenografts. A secondary aim was to evaluate several formats of imaging probes for visualization of HER2 expression in tumors. Administration of ADAPT6-ABD-mcDM1 provided a significant delay of tumor growth and increased the median survival of the mice, in comparison with both a non-targeting homologous construct (ADAPT(Neg)-ABD-mcDM1) and the vehicle-treated groups, without inducing toxicity to liver or kidneys. Moreover, the evaluation of imaging probes showed that small scaffold proteins, such as Tc-99m(CO)(3)-ADAPT6 or the affibody molecule Tc-99m-Z(HER2:41071), are well suited as diagnostic companions for potential stratification of patients for ADAPT6-ABD-mcDM1-based therapy.
|
|
| 11. |
- Huang, Tianqi, et al.
(author)
-
Failure Characterization of Discrete SiC MOSFETs under Forward Power Cycling Test
- 2024
-
In: Energies. - : MDPI AG. - 1996-1073. ; 17:11
-
Journal article (peer-reviewed)abstract
- Silicon carbide (SiC)-based metal-oxide-semiconductor field-effect transistors (MOSFETs) hold promising application prospects in future high-capacity high-power converters due to their excellent electrothermal characteristics. However, as nascent power electronic devices, their long-term operational reliability lacks sufficient field data. The power cycling test is an important experimental method to assess packaging-related reliability. In order to obtain data closest to actual working conditions, forward power cycling is utilized to carry out SiC MOSFET degradation experiments. Due to the wide bandgap characteristics of SiC MOSFETs, the short-term drift of the threshold voltage is much more serious than that of silicon (Si)-based devices. Therefore, an offline threshold voltage measurement circuit is implemented during power cycling tests to minimize errors arising from this short-term drift. Different characterizations are performed based on power cycling tests, focused on measuring the on-state resistance, thermal impedance, and threshold voltage of the devices. The findings reveal that the primary failure mode under forward power cycling tests, with a maximum junction temperature of 130 degrees C, is bond-wire degradation. Conversely, the solder layer and gate oxide exhibit minimal degradation tendencies under these conditions.
|
|
| 12. |
- Kravchenko, Oleksandr, et al.
(author)
-
Improving the Stability of Ru-bda Molecular Water Oxidation Catalysts via π‑System Extension of Backbone Ligand
-
Other publication (other academic/artistic)abstract
- Originating from natural enzymes, molecular catalysts often serve as models for studying certain catalytic processes. Despite well-established mechanisms and structure-activity relationships, molecular electrocatalysts are much less used in industry than materials. Wide application of molecular complexes is primarily limited by their insufficient stability, and many efforts are devoted to addressing this problem. Design of water oxidation catalysts experienced gradual development, associated with the gains in stability, e.g., through well-defined coordination modes, moderate flexibility, oxidatively stable and negatively charged ligands. Herein we report a simple yet effective modification of state-of-the-art Ru-bda based water oxidation catalysts. Extension of the π-system of equatorial bipyridine ligand improves electron density delocalization and stabilizes molecular orbitals with high 3d contribution, which are partly responsible for axial ligand bonding. This feature allows catalysts to reach turnover numbers up to 20000, operating for hours in pH 1 solution at concentrations lower than 5 μM.
|
|
| 13. |
- Kravchenko, Oleksandr, et al.
(author)
-
Modulation of the First and Second Coordination Sphere Effects by Backbone Substitution in Ru(bda)L2 Water Oxidation Catalysts
-
Other publication (other academic/artistic)abstract
- Active research in the field of renewable energy has provided numerous molecular water oxidation catalysts for efficient water splitting, such as Ru-bda. As the most stable and active catalysts are based on ruthenium, a larger focus is put on the understanding, which properties of the ligands can be leveraged in cheap and sustainable catalysts to compensate the drawbacks of non-noble metals. Most modifications of the bda ([2,2'-bipyridine]-6,6'-dicarboxylate) ligand do not yield in more efficient catalysts and in general constitute a complicated structure-activity relationship. Herein, we report two new modifications of bda with strong electron-donating and electron-withdrawing substituents and their implications on the intra- and intermolecular interactions.
|
|
| 14. |
- Leitao, Charles Dahlsson, et al.
(author)
-
Conditionally activated affibody-based prodrug targeting EGFR demonstrates improved tumor selectivity
-
Other publication (other academic/artistic)abstract
- Safety and efficacy of cancer-targeting treatments can be improved by conditional activation conferred by the distinct milieu of the tumour microenvironment. Proteases are intricately involved in tumorigenesis and commonly dysregulated with elevated expression and activity. Design of prodrug molecules with protease-dependent activation has the potential to increase tumor-selective targeting, while decreasing the exposure to healthy tissues, thus improving safety, allowing for administration of higher doses or use of more aggressive treatment options, leading to higher therapeutic efficacy. We have previously performed in vitro characterizations of an affibody-based prodrug approach for protease-mediated targeting of EGFR. In this study we demonstrate the potential for selective tumor-targeting and shielded uptake in healthy tissues in vivo using tumor-bearing mice for an EGFR-targeting affibody prodrug.
|
|
| 15. |
- Leitao, Charles Dahlsson, 1992-, et al.
(author)
-
Conditionally activated affibody-based prodrug targeting EGFR demonstrates improved tumour selectivity
- 2023
-
In: Journal of Controlled Release. - : Elsevier BV. - 0168-3659 .- 1873-4995. ; 357, s. 185-195
-
Journal article (peer-reviewed)abstract
- Safety and efficacy of cancer-targeting treatments can be improved by conditional activation enabled by the distinct milieu of the tumour microenvironment. Proteases are intricately involved in tumourigenesis and commonly dysregulated with elevated expression and activity. Design of prodrug molecules with protease -dependent activation has the potential to increase tumour-selective targeting while decreasing exposure to healthy tissues, thus improving the safety profile for patients. Higher selectivity could also allow for adminis-tration of higher doses or use of more aggressive treatment options, leading to higher therapeutic efficacy. We have previously developed an affibody-based prodrug with conditional targeting of EGFR conferred by an anti-idiotypic affibody masking domain (ZB05). We could show that binding to endogenous EGFR on cancer cells in vitro was restored following proteolytic removal of ZB05. In this study we evaluate a novel affibody-based pro -drug design, which incorporates a protease substrate sequence recognized by cancer-associated proteases and demonstrate the potential of this approach for selective tumour-targeting and shielded uptake in healthy tissues in vivo using tumour-bearing mice. This may widen the therapeutic index of cytotoxic EGFR-targeted thera-peutics by decreasing side effects, improving selectivity of drug delivery, and enabling the use of more potent cytotoxic drugs.
|
|
| 16. |
- Lensink, Marc F., et al.
(author)
-
Impact of AlphaFold on structure prediction of protein complexes: The CASP15-CAPRI experiment
- 2023
-
In: Proteins. - : WILEY. - 0887-3585 .- 1097-0134.
-
Journal article (peer-reviewed)abstract
- We present the results for CAPRI Round 54, the 5th joint CASP-CAPRI protein assembly prediction challenge. The Round offered 37 targets, including 14 homodimers, 3 homo-trimers, 13 heterodimers including 3 antibody-antigen complexes, and 7 large assemblies. On average similar to 70 CASP and CAPRI predictor groups, including more than 20 automatics servers, submitted models for each target. A total of 21 941 models submitted by these groups and by 15 CAPRI scorer groups were evaluated using the CAPRI model quality measures and the DockQ score consolidating these measures. The prediction performance was quantified by a weighted score based on the number of models of acceptable quality or higher submitted by each group among their five best models. Results show substantial progress achieved across a significant fraction of the 60+ participating groups. High-quality models were produced for about 40% of the targets compared to 8% two years earlier. This remarkable improvement is due to the wide use of the AlphaFold2 and AlphaFold2-Multimer software and the confidence metrics they provide. Notably, expanded sampling of candidate solutions by manipulating these deep learning inference engines, enriching multiple sequence alignments, or integration of advanced modeling tools, enabled top performing groups to exceed the performance of a standard AlphaFold2-Multimer version used as a yard stick. This notwithstanding, performance remained poor for complexes with antibodies and nanobodies, where evolutionary relationships between the binding partners are lacking, and for complexes featuring conformational flexibility, clearly indicating that the prediction of protein complexes remains a challenging problem.
|
|
| 17. |
- Liu, Tianqi, et al.
(author)
-
Bioinspired Active Site with a Coordination-Adaptive Organosulfonate Ligand for Catalytic Water Oxidation at Neutral pH
- 2023
-
In: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 145:21, s. 11818-11828
-
Journal article (peer-reviewed)abstract
- Many enzymes use adaptive frameworks to preorganize substrates, accommodate various structural and electronic demands of intermediates, and accelerate related catalysis. Inspired by biological systems, a Ru-based molecular water oxidation catalyst containing a configurationally labile ligand [2,2′:6′,2″-terpyridine]-6,6″-disulfonate was designed to mimic enzymatic framework, in which the sulfonate coordination is highly flexible and functions as both an electron donor to stabilize high-valent Ru and a proton acceptor to accelerate water dissociation, thus boosting the catalytic water oxidation performance thermodynamically and kinetically. The combination of single-crystal X-ray analysis, various temperature NMR, electrochemical techniques, and DFT calculations was utilized to investigate the fundamental role of the self-adaptive ligand, demonstrating that the on-demand configurational changes give rise to fast catalytic kinetics with a turnover frequency (TOF) over 2000 s–1, which is compared to oxygen-evolving complex (OEC) in natural photosynthesis.
|
|
| 18. |
- Liu, Tianqi, et al.
(author)
-
Hydrophobic Interactions of Ru-bda-Type Catalysts for Promoting Water Oxidation Activity
- 2021
-
In: Energy & Fuels. - : American Chemical Society (ACS). - 0887-0624 .- 1520-5029.
-
Journal article (peer-reviewed)abstract
- The catalytic activity of the bimolecular reaction was affected by many parameters. Although many efforts have been dedicated to investigate the influence of secondary interactions in pre-organizing catalysts, the hydrophobic effect on Ru-bda-type water oxidation catalysts remains unclear as a result of the lack of an ideal catalytic model. In this work, four catalysts 1–4 with variable hydrophobicity have been synthesized, and cerium(IV)-driven water oxidation results showed that the hydrophobic complexes 3 and 4 outperformed the hydrophilic complex 2. Steric mapping, nuclear magnetic resonance, and differential pulse voltammogram studies indicated that the increase in activity has no correlation with electronic and steric effects but has correlation with hydrophobicity. Molecular dynamics have shown that the modifications of the hydrophobicity on the axial pyridine ligands of the Ru-bda type of catalysts can improve the water oxidation catalytic activity by stabilizing the pre-reactive catalyst dimer.
|
|
| 19. |
- Liu, Tianqi, et al.
(author)
-
Iron-Based Molecular Water Oxidation Catalysts : Abundant, Cheap, and Promising
- 2019
-
In: Chemistry - An Asian Journal. - : WILEY-V C H VERLAG GMBH. - 1861-4728 .- 1861-471X. ; 14:1, s. 31-43
-
Research review (peer-reviewed)abstract
- An efficient and robust water oxidation catalyst based on abundant and cheap materials is the key to converting solar energy into fuels through artificial photosynthesis for the future of humans. The development of molecular water oxidation catalysts (MWOCs) is a smart way to achieve promising catalytic activity, thanks to the clear structures and catalytic mechanisms of molecular catalysts. Efficient MWOCs based on noble-metal complexes, for example, ruthenium and iridium, have been well developed over the last 30 years; however, the development of earth-abundant metal-based MWOCs is very limited and still challenging. Herein, the promising prospect of iron-based MWOCs is highlighted, with a comprehensive summary of previously reported studies and future research focus in this area.
|
|
| 20. |
- Liu, Tianqi, et al.
(author)
-
Isolation and Identification of Pseudo Seven-Coordinate Ru(III) Intermediate Completing the Catalytic Cycle of Ru-bda Type of Water Oxidation Catalysts
- 2022
-
In: CCS Chemistry. - : Chinese Chemical Society. - 2096-5745. ; 4:7, s. 2481-2490
-
Journal article (peer-reviewed)abstract
- Isolation of RuIII-bda (17-electron specie) complex with an aqua ligand (2-electron donor) is challenging due to violation of the 18-electron rule. Although considerable efforts have been dedicated to mechanistic studies of water oxidation by the Ru-bda family, the structure and initial formation of the RuIII-bda aqua complex are still controversial. Herein, we challenge this often overlooked step by designing a pocket-shape Ru-based complex 1. The computational studies showed that 1 possesses the crucial hydrophobicity at the RuV(O) state as well as similar probability of access of terminal O to solvent water molecules when compared with classic Ru-bda catalysts. Through characterization of single-crystal structures at the RuII and RuIII states, a pseudo seven-coordinate “ready-to-go” aqua ligand with RuIII...O distance of 3.62 Å was observed. This aqua ligand was also found to be part of a formed hydrogen-bonding network, providing a good indication of how the RuIII-OH2 complex is formed.
|
|
| 21. |
- Liu, Tianqi
(author)
-
Outer Coordination Spheres Engineering of Ru-based Molecular Water Oxidation Catalysts
- 2022
-
Doctoral thesis (other academic/artistic)abstract
- The outer coordination sphere plays a vital role in metalloenzyme catalysis, while this principle is relatively less considered in the design of man-made molecular catalysts. This thesis investigates the role of outer coordination spheres in water oxidation by a series of ruthenium-based complexes.The first chapter presents an overview of the development of molecular water oxidation catalysts, mainly focusing on ruthenium-based complexes. Moreover, the strategies used to modulate the inner and outer coordination spheres are also summarized.The second chapter clarifies the role of electronic effects and hydrophobic interactions in Ru-bda-type catalysts. Electronic effects are found to be the less-dominating parameter for the catalytic activity and mechanism, while hydrophobic interactions play an important role in catalysis. The third chapter focuses on the switch in mechanism with Ru-pda-type catalysts through strengthening of the π-π interactions between the axial ligands.The fourth chapter discusses a crystal structure of the long-proposed pseudo-seven-coordinate RuIII-aqua complex where the aqua ligand is stabilized by the distal ligand. The obtained complex enables us to visualize how the catalyst grasps the incoming aqua ligands at the initial catalytic step. Based on this catalytic model, four catalysts with well-defined outer coordination spheres are synthesized, and the influence of hydrophilic/hydrophobic outer spheres on water oxidation is discussed in chapter five.In general, this thesis follows the transition of the outer coordination sphere engineering from coordinated ligand modifications to remote substituent modulations.
|
|
| 22. |
- Liu, Tianqi, et al.
(author)
-
Promoting O–O Radical Coupling of Water Oxidation Catalyst via Secondary Interaction
-
Other publication (other academic/artistic)abstract
- Interaction of two metal–oxyl radicals (I2M) mechanism can theoretically provide water oxidation catalysts with lower overpotentials because they avoid forming the high-energy metal-OOH intermediate. However, only two Ru-based catalytic systems have been reported involving intermolecular I2M pathway. Herein, a Ru-pda-type (pda is 1,10-phenanthroline-2,9-dicarboxylate acid) water oxidation catalyst was designed and synthesized. Through synergistic modulation of oxo spin-density and organizational entropy, mechanism switching from the water nucleophilic attack (WNA) to I2M was realized, accompanied by a rate increase of around two orders of magnitude.
|
|
| 23. |
- Liu, Tianqi, et al.
(author)
-
Promoting Proton Transfer and Stabilizing Intermediates in Catalytic Water Oxidation via Hydrophobic Outer Sphere Interactions
- 2022
-
In: Chemistry - A European Journal. - : Wiley-VCH Verlagsgesellschaft. - 0947-6539 .- 1521-3765. ; 28:24
-
Journal article (peer-reviewed)abstract
- The outer coordination sphere of metalloenzyme often plays an important role in its high catalytic activity, however, this principle is rarely considered in the design of man-made molecular catalysts. Herein, four Ru-bda (bda=2,2 '-bipyridine-6,6 '-dicarboxylate) based molecular water oxidation catalysts with well-defined outer spheres are designed and synthesized. Experimental and theoretical studies showed that the hydrophobic environment around the Ru center could lead to thermodynamic stabilization of the high-valent intermediates and kinetic acceleration of the proton transfer process during catalytic water oxidation. By this outer sphere stabilization, a 6-fold rate increase for water oxidation catalysis has been achieved.
|
|
| 24. |
|
|
| 25. |
|
|
