1
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Gentry NE, Kurimoto A, Cui K, Cleron JL, Xiang CM, Hammes-Schiffer S, Mayer JM. Hydrogen on Colloidal Gold Nanoparticles. J Am Chem Soc 2024; 146:14505-14520. [PMID: 38743444 DOI: 10.1021/jacs.4c00507] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/16/2024]
Abstract
Colloidal gold nanoparticles (AuNPs) have myriad scientific and technological applications, but their fundamental redox chemistry is underexplored. Reported here are titration studies of oxidation and reduction reactions of aqueous AuNP colloids, which show that the AuNPs bind substantial hydrogen (electrons + protons) under mild conditions. The 5 nm AuNPs are reduced to a similar extent with reductants from borohydrides to H2 and are reoxidized back essentially to their original state by oxidants, including O2. The reactions were monitored via surface plasmon resonance (SPR) optical absorption, which was shown to be much more sensitive to surface H than to changes in solution conditions. Reductions with H2 occurred without pH changes, demonstrating that hydrogenation forms surface H rather than releasing H+. Computational studies suggested that an SPR blueshift was expected for H atom addition, while just electron addition likely would have caused a redshift. Titrations consistently showed a maximum redox change of the 5 nm NPs, independent of the reagent, corresponding to 9% of the total gold or ∼30% hydrogen surface coverage (∼370 H per AuNP). Larger AuNPs showed smaller maximum fractional surface coverages. We conclude that H binds to the edge, corner, and defect sites of the AuNPs, which explains the stoichiometric limitation and the size effect. The finding of substantial and stable hydrogen on the AuNP surface under mild reducing conditions has potential implications for various applications of AuNPs in reducing environments, from catalysis to biomedicine. This finding contrasts with the behavior of bulk gold and with the typical electron-focused perspective in this field.
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Affiliation(s)
- Noreen E Gentry
- Department of Chemistry, Yale University, New Haven, Connecticut 06520-8107, United States
| | - Aiko Kurimoto
- Department of Chemistry, Yale University, New Haven, Connecticut 06520-8107, United States
| | - Kai Cui
- Department of Chemistry, Yale University, New Haven, Connecticut 06520-8107, United States
| | - Jamie L Cleron
- Department of Chemistry, Yale University, New Haven, Connecticut 06520-8107, United States
| | - Claire M Xiang
- Department of Chemistry, Yale University, New Haven, Connecticut 06520-8107, United States
| | - Sharon Hammes-Schiffer
- Department of Chemistry, Yale University, New Haven, Connecticut 06520-8107, United States
| | - James M Mayer
- Department of Chemistry, Yale University, New Haven, Connecticut 06520-8107, United States
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2
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Herzog AE, Michael TJ, Dunkelberger AD, Johannes MD, Rolison DR, DeSario PA, Novak TG. Nanostructured CeO 2 photocatalysts: optimizing surface chemistry, morphology, and visible-light absorption. NANOSCALE 2024; 16:9659-9679. [PMID: 38683667 DOI: 10.1039/d4nr00676c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2024]
Abstract
Emerging photocatalytic applications of cerium dioxide (CeO2) include green hydrogen production, CO2 conversion to fuels, and environmental remediation of various toxic molecules. These applications leverage the oxygen storage capacity and tunable surface chemistry of CeO2 to photocatalyze the chosen reaction, but many open questions remain regarding the fundamental physics of photocatalysis over CeO2. The commonly ascribed 'bandgap' of CeO2 (∼3.1 eV) differs fundamentally from other photocatalytic oxides such as TiO2; UV light excites an electron from the CeO2 valence band into a 4f state, generating a polaron as the lattice distorts around the localized charge. Researchers often disregard the distinction between the 4f state and a traditional, delocalized conduction band, resulting in ambiguity regarding mechanisms of charge transfer and visible-light absorption. This review summarizes modern literature regarding CeO2 photocatalysis and discusses commonly reported photocatalytic reactions and visible light-sensitization strategies. We detail the often misunderstood fundamental physics of CeO2 photocatalysis and supplement previous work with original computational insights. The exceptional progress and remaining challenges of CeO2-based photocatalysts are highlighted, along with suggestions for further research directions based on the observed gaps in current understanding.
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Affiliation(s)
- Austin E Herzog
- NRC Postdoctoral Associate, U.S. Naval Research Laboratory, Washington, D.C., 20375, USA
| | - Tara J Michael
- NRC Postdoctoral Associate, U.S. Naval Research Laboratory, Washington, D.C., 20375, USA
| | - Adam D Dunkelberger
- Chemistry Division (Code 6100), U.S. Naval Research Laboratory, Washington, D.C., 20375, USA.
| | - Michelle D Johannes
- Materials Science and Technology Division (Code 6300), U.S. Naval Research Laboratory, Washington, D.C., 20375, USA
| | - Debra R Rolison
- Chemistry Division (Code 6100), U.S. Naval Research Laboratory, Washington, D.C., 20375, USA.
| | - Paul A DeSario
- Former NRL Staff Scientist in Code 6100, Advanced Naval Platforms Division, Office of Naval Research, Arlington, VA, 22203, USA
| | - Travis G Novak
- Chemistry Division (Code 6100), U.S. Naval Research Laboratory, Washington, D.C., 20375, USA.
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3
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Palys L, Stephen D, Mao Z, Mergelsberg ST, Boglaienko D, Chen Y, Liu L, Bae Y, Jin B, Sommers JA, De Yoreo JJ, Nyman M. Cerium Nanophases from Cerium Ammonium Nitrate. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2024; 40:4350-4360. [PMID: 38364791 DOI: 10.1021/acs.langmuir.3c03611] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/18/2024]
Abstract
Ceria nanomaterials with facile CeIII/IV redox behavior are used in sensing, catalytic, and therapeutic applications, where inclusion of CeIII has been correlated with reactivity. Understanding assembly pathways of CeO2 nanoparticles (NC-CeO2) in water has been challenged by "blind" synthesis, including rapid assembly/precipitation promoted by heat or strong base. Here, we identify a layered phase denoted Ce-I with a proposed formula CeIV(OH)3(NO3)·xH2O (x ≈ 2.5), obtained by adding electrolytes to aqueous cerium ammonium nitrate (CAN) to force precipitation. Ce-I represents intermediate hydrolysis species between dissolved CAN and NC-CeO2, where CAN is a commonly used CeIV compound that exhibits unusual aqueous and organic solubility. Ce-I features Ce-(OH)2-Ce units, representing the first step of hydrolysis toward NC-CeO2 formation, challenging prior assertions about CeIV hydrolysis. Structure/composition of poorly crystalline Ce-I was corroborated by a pair distribution function, Ce-L3 XAS (X-ray absorption spectroscopy), compositional analysis, and 17O nuclear magnetic resonance spectroscopy. Formation of Ce-I and its transformation to NC-CeO2 is documented in solution by small-angle X-ray scattering (SAXS) and in the solid-state by transmission electron microscopy (TEM) and powder X-ray diffraction. Morphologies identified by TEM support form factor models for SAXS analysis, evidencing the incipient assembly of Ce-I. Finally, two morphologies of NC-CeO2 are identified. Sequentially, spherical NC-CeO2 particles coexist with Ce-I, and asymmetric NC-CeO2 with up to 35% CeIII forms at the expense of Ce-I, suggesting direct replacement.
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Affiliation(s)
- Lauren Palys
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331, United States
- Pacific Northwest National Laboratory, Richland, Washington 99352, United States
| | - Doctor Stephen
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331, United States
| | - Zhiwei Mao
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331, United States
| | | | - Daria Boglaienko
- Pacific Northwest National Laboratory, Richland, Washington 99352, United States
| | - Ying Chen
- Pacific Northwest National Laboratory, Richland, Washington 99352, United States
| | - Lili Liu
- Pacific Northwest National Laboratory, Richland, Washington 99352, United States
| | - Yuna Bae
- Pacific Northwest National Laboratory, Richland, Washington 99352, United States
| | - Biao Jin
- Pacific Northwest National Laboratory, Richland, Washington 99352, United States
| | - James A Sommers
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331, United States
| | - James J De Yoreo
- Pacific Northwest National Laboratory, Richland, Washington 99352, United States
| | - May Nyman
- Department of Chemistry, Oregon State University, Corvallis, Oregon 97331, United States
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4
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Patel V, Jose L, Philippot G, Aymonier C, Inerbaev T, McCourt LR, Ruppert MG, Qi D, Li W, Qu J, Zheng R, Cairney J, Yi J, Vinu A, Karakoti AS. Fluoride-assisted detection of glutathione by surface Ce 3+/Ce 4+ engineered nanoceria. J Mater Chem B 2022; 10:9855-9868. [PMID: 36415972 DOI: 10.1039/d2tb01135b] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Nanoceria has evolved as a promising nanomaterial due to its unique enzyme-like properties, including excellent oxidase mimetic activity, which significantly increases in the presence of fluoride ions. However, this significant increase in oxidase activity has never been utilised as a signal enhancer for the detection of biological analytes partly because of the lack of understanding of the mechanism involved in this process. In this study, we show that the surface oxidation state of cerium ions plays a very crucial role in different enzymatic activities, especially the oxidase mimetic activity by engineering nanoceria with three different surface Ce4+/Ce3+ compositions. Using DFT calculations combined with Bader charge analysis, it is demonstrated that stoichiometric ceria registers a higher oxidase mimetic activity than oxygen-deficient ceria with a low Ce4+/Ce3+ ratio due to a higher charge transfer from a substrate, 3,3',5,5' tetramethylbenzidine (TMB), to the ceria surface. We also show that the fluoride ions can significantly increase the charge transfer from the TMB surface to ceria irrespective of the surface Ce4+/Ce3+ ratio. Using this knowledge, we first compare the fluoride sensing properties of nanoceria with high Ce4+ and mixed Ce4+/Ce3+ oxidation states and further demonstrate that the linear detection range of fluoride ions can be extended to 1-10 ppm for nanoceria with mixed oxidation states. Then, we also demonstrate an assay for fluoride assisted detection of glutathione, an antioxidant with elevated levels during cancer, using nanoceria with a high surface Ce4+/Ce3+ ratio. The addition of fluoride ions in this assay allows the detection of glutathione in the linear range of 2.5-50 ppm with a limit of detection (LOD) of 3.8 ppm. These studies not only underpin the role of the surface Ce4+/Ce3+ ratio in tuning the fluoride assisted boost in the oxidase mimetic activity of nanoceria but also its strategic application in designing better colourimetric assays.
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Affiliation(s)
- Vaishwik Patel
- Global Innovative Center for Advanced Nanomaterials (GICAN), School of Engineering College of Engineering, Science and Environment, The University of Newcastle, Callaghan, NSW, 2308, Australia.
| | - Linta Jose
- Global Innovative Center for Advanced Nanomaterials (GICAN), School of Engineering College of Engineering, Science and Environment, The University of Newcastle, Callaghan, NSW, 2308, Australia.
| | - Gilles Philippot
- Univ. Bordeaux, CNRS, Bordeaux INP, ICMCB, UMR 5026, F-33600 Pessac, France
| | - Cyril Aymonier
- Univ. Bordeaux, CNRS, Bordeaux INP, ICMCB, UMR 5026, F-33600 Pessac, France
| | - Talgat Inerbaev
- L. N. Gumilyov Eurasian National University, Nur-Sultan 010008, Kazakhstan.,National University of Science and Technology "MISIS", Moscow 119049, Russia
| | - Luke R McCourt
- School of Engineering, College of Engineering, Science and Environment, The University of Newcastle, Callaghan, 2308, Australia
| | - Michael G Ruppert
- School of Engineering, College of Engineering, Science and Environment, The University of Newcastle, Callaghan, 2308, Australia
| | - Dongchen Qi
- Centre for Materials Science, School of Chemistry and Physics, Queensland University of Technology, Brisbane, QLD 4001, Australia
| | - Wei Li
- Centre for Materials Science, School of Chemistry and Physics, Queensland University of Technology, Brisbane, QLD 4001, Australia
| | - Jiangtao Qu
- School of Physics, The University of Sydney, NSW, 2000, Australia
| | - Rongkun Zheng
- School of Physics, The University of Sydney, NSW, 2000, Australia
| | - Julie Cairney
- School of Physics, The University of Sydney, NSW, 2000, Australia
| | - Jiabao Yi
- Global Innovative Center for Advanced Nanomaterials (GICAN), School of Engineering College of Engineering, Science and Environment, The University of Newcastle, Callaghan, NSW, 2308, Australia.
| | - Ajayan Vinu
- Global Innovative Center for Advanced Nanomaterials (GICAN), School of Engineering College of Engineering, Science and Environment, The University of Newcastle, Callaghan, NSW, 2308, Australia.
| | - Ajay S Karakoti
- Global Innovative Center for Advanced Nanomaterials (GICAN), School of Engineering College of Engineering, Science and Environment, The University of Newcastle, Callaghan, NSW, 2308, Australia.
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5
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Photoactive Widegap Oxide Doped ZnO with Non-stoichiometric Matrix: Aspects of Formation. Top Catal 2021. [DOI: 10.1007/s11244-020-01301-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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6
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Hosseinzadeh R, Khorsandi K, Esfahani HS, Habibi M, Hosseinzadeh G. Preparation of cerium-curcumin and cerium-quercetin complexes and their LEDs irradiation assisted anticancer effects on MDA-MB-231 and A375 cancer cell lines. Photodiagnosis Photodyn Ther 2021; 34:102326. [PMID: 33971331 DOI: 10.1016/j.pdpdt.2021.102326] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2021] [Revised: 04/25/2021] [Accepted: 04/30/2021] [Indexed: 11/15/2022]
Abstract
Cancer remains common and often is difficult to eradicate. In particular resistant forms like triple negative breast cancer and melanoma generally allow for very short survival. Curcumin and quercetin as two important polyphenols from plants which have different biological roles, potentially including anti-cancer effect. But their clinical application is limited due to poor solubility in aqueous medium. Photodynamic therapy (PDT) is a cancer treatment using select chemical compounds as photosensitizers, which when activated by light create toxic singlet oxygen. Studies done on plant based photosensitizers such as curcumin and quercetin have shown the ability to ablate tumors. Here we discuss using them as improved PS by making their complex with cerium ions as a delivery system for MDA-MB-231 and A375 cancer cell lines treatment. For this purpose, the MDA-MB-231 human breast cancer cell line exposed to red light irradiation (as pretreatment) then treated with curcumin and quercetin alone and also their complex with cerium. In another study the cells treated with curcumin-cerium and quercetin-cerium complex and then irradiated with blue light (photodynamic treatment). Cell survival and apoptosis were determined using MTT and fluorescence microscopy. The result showed that curcumin and quercetin in complex with cerium ions have better toxic effect against both breast and melanoma cancer cells as compared to each compound alone. The finding revealed that curcumin and quercetin in cerium complex could be considered as a new approach in the photodynamic treatment of breast and melanoma cancer cells.
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Affiliation(s)
- Reza Hosseinzadeh
- Department of Medical Laser, Medical Laser Research Center, YARA Institute, ACECR, Tehran, Iran.
| | - Khatereh Khorsandi
- Department of Photodynamic, Medical Laser Research Center, YARA Institute, ACECR, Tehran, Iran
| | - Homa Sadat Esfahani
- Department of Photodynamic, Medical Laser Research Center, YARA Institute, ACECR, Tehran, Iran
| | - Masoud Habibi
- Department of Medical Laser, Medical Laser Research Center, YARA Institute, ACECR, Tehran, Iran
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7
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Hartati YW, Topkaya SN, Gaffar S, Bahti HH, Cetin AE. Synthesis and characterization of nanoceria for electrochemical sensing applications. RSC Adv 2021; 11:16216-16235. [PMID: 35479153 PMCID: PMC9031634 DOI: 10.1039/d1ra00637a] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2021] [Revised: 05/24/2021] [Accepted: 04/25/2021] [Indexed: 12/16/2022] Open
Abstract
Nanoceria (cerium oxide nanoparticles: CeO2-NPs) has received significant attention due to its biocompatibility, good conductivity, and the ability to transfer oxygen. Nanoceria has been widely used to develop electrochemical sensors and biosensors as it could increase response time, sensitivity, and stability of the sensor. In this review, we discussed synthesis methods, and the recent applications employing CeO2-NPs for electrochemical detection of various analytes reported in the most recent four years.
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Affiliation(s)
- Yeni Wahyuni Hartati
- Department of Chemistry, Faculty of Mathematics and Natural Sciences, Universitas Padjadjaran Indonesia
| | - Seda Nur Topkaya
- Department of Analytical Chemistry, Faculty of Pharmacy, Izmir Katip Celebi University Turkey
| | - Shabarni Gaffar
- Department of Chemistry, Faculty of Mathematics and Natural Sciences, Universitas Padjadjaran Indonesia
| | - Husein H Bahti
- Department of Chemistry, Faculty of Mathematics and Natural Sciences, Universitas Padjadjaran Indonesia
| | - Arif E Cetin
- Izmir Biomedicine and Genome Center Izmir Turkey
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8
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Agarwal RG, Kim HJ, Mayer JM. Nanoparticle O-H Bond Dissociation Free Energies from Equilibrium Measurements of Cerium Oxide Colloids. J Am Chem Soc 2021; 143:2896-2907. [PMID: 33565871 DOI: 10.1021/jacs.0c12799] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
A novel equilibrium strategy for measuring the hydrogen atom affinity of colloidal metal oxide nanoparticles is presented. Reactions between oleate-capped cerium oxide nanoparticle colloids (nanoceria) and organic proton-coupled electron transfer (PCET) reagents are used as a model system. Nanoceria redox changes, or hydrogen loadings, and overall reaction stoichiometries were followed by both 1H NMR and X-ray absorption near-edge spectroscopies. These investigations revealed that, in many cases, reactions between nanoceria and PCET reagents reach equilibrium states with good mass balance. Each equilibrium state is a direct measure of the bond strength, or bond dissociation free energy (BDFE), between nanoceria and hydrogen. Further studies, including those with larger nanoceria, indicated that the relevant bond is a surface O-H. Thus, we have measured surface O-H BDFEs for nanoceria-the first experimental BDFEs for any nanoscale metal oxide. Remarkably, the measured CeO-H BDFEs span 13 kcal mol-1 (0.56 eV) with changes in the average redox state of the nanoceria colloid. Possible chemical models for this strong dependence are discussed. We propose that the tunability of ceria BDFEs may be important in explaining its effectiveness in catalysis. More generally, metal oxide BDFEs have been used as predictors of catalyst efficacy that, traditionally, have only been accessible by computational methods. These results provide important experimental benchmarks for metal oxide BDFEs and demonstrate that the concepts of molecular bond strength thermochemistry can be applied to nanoscale materials.
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Affiliation(s)
- Rishi G Agarwal
- Department of Chemistry, Yale University, New Haven, Connecticut 06520-8107, United States
| | - Hyun-Jo Kim
- Department of Chemistry, Yale University, New Haven, Connecticut 06520-8107, United States
| | - James M Mayer
- Department of Chemistry, Yale University, New Haven, Connecticut 06520-8107, United States
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9
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Wong KH, Cheung WM, Pham HL, So YM, Sung HHY, Williams ID, Leung WH. Oxidizing Cerium(IV) Alkoxide Complexes Supported by the Kläui Ligand [Co(η 5-C 5H 5){P(O)(OEt) 2} 3] -: Synthesis, Structure, and Redox Reactivity. Inorg Chem 2021; 60:2261-2270. [PMID: 33499604 DOI: 10.1021/acs.inorgchem.0c03105] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Tetravalent cerium alkoxide complexes supported by the Kläui tripodal ligand [Co(η5-C5H5){P(O)(OEt)2}3]- (LOEt-) have been synthesized, and their nucleophilic and redox reactivity have been studied. Treatment of the Ce(IV) oxo complex [CeIV(LOEt)2(O)(H2O)]·MeCONH2 (1) with iPrOH or reaction of [CeIV(LOEt)2Cl2] (2) with Ag2O in iPrOH afforded the Ce(IV) dialkoxide complex [CeIV(LOEt)2(OiPr)2] (3-iPr). The methoxide and ethoxide analogues [CeIV(LOEt)2(OR)2] (R = Me (3-Me), Et (3-Et)) have been prepared similarly from 2 and Ag2O in ROH. Reaction of 3-iPr with an equimolar amount of 2 yielded a new Ce(IV) complex that was formulated as the chloro-alkoxide complex [CeIV(LOEt)2(OiPr)Cl] (4). Treatment of 3-iPr with HX and methyl triflate (MeOTf) afforded [Ce(LOEt)2X2] (X- = Cl-, NO3-, PhO-) and [CeIV(LOEt)2(OTf)2], respectively, whereas treatment with excess CO2 in hexane led to isolation of the Ce(IV) carbonate [CeIV(LOEt)2(CO3)]. 3-iPr reacted with water in hexane to give a Ce(III) complex and a Ce(IV) species, presumably the reported tetranuclear oxo cluster [CeIV4(LOEt)4(O)5(OH)2]. The Ce(IV) alkoxide complexes are capable of oxidizing substituted phenols, possibly via a proton-coupled electron transfer pathway. Treatment of 3-iPr with ArOH afforded the Ce(III) aryloxide complexes [CeIII(LOEt)2(OAr)] (Ar = 2,4,6-tri-tert-butylphenyl (5), 2,6-diphenylphenyl (6)). On the other hand, a Ce(III) complex containing a monodeprotonated 2,2'-biphenol ligand, [CeIII(LOEt)2(tBu4C12H4O2H)] (7) (tBu4C12H4O2H2 = 4,4',6,6'-tetra-tert-butyl-2,2'-biphenol), was isolated from the reaction of 3-iPr with 2,4-di-tert-butylphenol. The crystal structures of complexes 3-iPr, 3-Me, 3-Et, and 5-7 have been determined.
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Affiliation(s)
- Kai-Hong Wong
- Department of Chemistry, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, P. R. China
| | - Wai-Man Cheung
- Department of Chemistry, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, P. R. China
| | - Hoang-Long Pham
- Department of Chemistry, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, P. R. China
| | - Yat-Ming So
- Department of Chemistry, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, P. R. China
| | - Herman H-Y Sung
- Department of Chemistry, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, P. R. China
| | - Ian D Williams
- Department of Chemistry, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, P. R. China
| | - Wa-Hung Leung
- Department of Chemistry, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, P. R. China
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10
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Pettinger NW, Empey JM, Fröbel S, Kohler B. Photoreductive dissolution of cerium oxide nanoparticles and their size-dependent absorption properties. Phys Chem Chem Phys 2020; 22:5756-5764. [PMID: 32104809 DOI: 10.1039/c9cp06579b] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Cerium oxide has attracted attention recently for its photocatalytic properties, but there are gaps in understanding its performance, especially at low and high pH. UV irradiation of ceria nanoparticles causes electrons from photogenerated electron-hole pairs to localize as small polarons, yielding Ce3+ ions. In pH 10 solution, ceria nanoparticles capped with polyacrylic acid ligands can accumulate large numbers of Ce3+ defects as revealed by strong bleaching of the absorption onset. In contrast, we show that UV irradiation of several-nanometer diameter ceria nanoparticles in acidic (pH < 3) aqueous solution releases Ce3+ ions into solution with a quantum yield that approaches 70% and that varies with excitation wavelength, particle size, and the presence of a hole scavenger (glycerol) on the nanoparticle surface. The instability of Ce3+ at the nanoparticle surface and the ability of electron small polarons to migrate to the surface by hopping strongly suggest that nanoceria is fully oxidized and essentially free of Ce3+ centers at pH < 3. Efficient photoreduction and the excellent stability of unirradiated nanoparticles make it easy to shrink the nanoparticles using only light, while maintaining them in a fully oxidized state. This enables study of the size-dependent absorption properties of ceria nanoparticles that are free of Ce3+ defects. No evidence of quantum confinement is observed, consistent with highly localized excited states. The observed quantum yields of photoreduction are higher than reported for other metal oxides, revealing that a significant fraction of electron-hole pairs are available for driving surface redox reactions, even in fully oxidized particles.
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Affiliation(s)
- Natasha W Pettinger
- Department of Chemistry and Biochemistry, The Ohio State University, 100 West 18th Avenue, Columbus, Ohio 43210, USA.
| | - Jennifer M Empey
- Department of Chemistry and Biochemistry, The Ohio State University, 100 West 18th Avenue, Columbus, Ohio 43210, USA.
| | - Sascha Fröbel
- Department of Chemistry and Biochemistry, The Ohio State University, 100 West 18th Avenue, Columbus, Ohio 43210, USA.
| | - Bern Kohler
- Department of Chemistry and Biochemistry, The Ohio State University, 100 West 18th Avenue, Columbus, Ohio 43210, USA.
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11
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Laga SM, Townsend TM, O'Connor AR, Mayer JM. Cooperation of cerium oxide nanoparticles and soluble molecular catalysts for alcohol oxidation. Inorg Chem Front 2020. [DOI: 10.1039/c9qi01640f] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Nano-cerium oxide and organometallic catalysts cooperate in anaerobic and aerobic alcohol oxidations.
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Affiliation(s)
| | - Tanya M. Townsend
- Department of Chemistry
- Yale University
- New Haven
- USA
- Department of Chemistry
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12
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Mahdavi-Shakib A, Husremovic S, Ki S, Glynn J, Babb L, Sempel J, Stavrinoudis I, Arce-Ramos JM, Nelson R, Grabow LC, Schwartz TJ, Frederick BG, Austin RN. Titania surface chemistry and its influence on supported metal catalysts. Polyhedron 2019. [DOI: 10.1016/j.poly.2019.05.012] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
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