Publication list:

1.    Involving Single-Atom Silver(0) in Selective Dehalogenation by AgF under Visible-Light Irradiation

Wu, Wenli; Cui, Enxin; Zhang, Yun; Zhang, Chen; Zhu, Feng; Tung, Chen-Ho; Wang, Yifeng*

ACS Catalysis 2019, 9, 6335-6341. https://pubs.acs.org/doi/10.1021/acscatal.9b01929

The dehalogenation-arylation and the hydrodehalogenation of various types of org. halides are selectively realized using AgF and visible light without any org. additives under mild conditions.  Single-atom silver(0) (denoted as SAAg) serves as the catalytically active center, and the TOF of SAAg reaches 6000 h^-1.  This elusive activity of Ag is beyond that expected from its ionic, nano, or bulk forms.

  

2.    Functionalization of Titanium-Oxide Cluster Ti₁₇O₂₄(OⁱC₃H₇)₂₀ with Catechols: Structures and Ligand-Exchange Reactivities

Liu, Caiyun, Hu, Junyi, Zhu, Feng, Zhan, Jinhua, Du, Lin, Wang, Yifeng and Tung, Chen-Ho

Chemistry - A European Journal 2019, DOI: 10.1002/chem.201902601. https://doi.org/10.1002/chem.201902601  

The functionalization of Ti₁₇O₂₄(OⁱC₃H₇)₂₀ (Ti₁₇₎ with substituted catechols is studied using crystallography, Raman spectroscopy and stopped-flow kinetics.  The knowledges on the number of accessible functionalities, their exact location correlated with their Raman assignment, and the kinetic parameters are acquired. A catecholate ligand binds to a five‐coordinated surface‐Ti of Ti₁₇ (denoted as Tia site) adopting the mono‐protonated, chelate‐bidentate binding mode, while binds to a six‐coordinated surface‐Ti (denoted as Tib site) adopting the mono‐dentate mode. With low eqs of added catechols the Tia sites show higher reactivity than Tib sites toward functionalization. Two binding modes may coexist and equilibrate in solution. Our results also imply that at most 8 of the 20 OⁱC₃H₇ ligands of Ti₁₇ are exchangeable without damage of the core structure. The kinetic studies point out that the ligand‐exchange reaction is second order and occurs very fast. The current findings are helpful for the controlled functionalization of Ti₁₇ and other Ti‐oxide clusters, and the further application of them as building blocks in supramolecular chemistry for the assembly of well‐defined organic‐inorganic hybrid materials.

3.    Preparation of Porous TiO₂ from an Iso-Polyoxotitanate Cluster for Rechargeable Sodium-Ion Batteries with High Performance

Zhang, Guanyun; Chu, Chenxiao; Yang, Jian; Tung, Chen-Ho; Wang, Yifeng

Journal of Physical Chemistry C (2019), 123(12), 7025-7032. https://pubs.acs.org/doi/10.1021/acs.jpcc.9b00213 

By aerobic calcination of a new titanium-oxide cluster (TOC) isolated from water, i.e., [Ti₆O₈(OH₂)₂₀]·(2,7-NDS)₄·2HCl·14H₂O (Ti₆-NDS; 2,7-NDS = 2,7-naphthalenedisulfonate), porous anatase TiO₂ was facially prepd.  The sample obtained at 400° exhibited a surface area of 108 cm³ g^-1 and an av. pore diam. of 16 nm.  When used as an anode material for a sodium-ion battery (SIB), it showed larger specific capacity and far superior rate performance than the other TiO₂samples, including those prepd. from another three TOCs under the same conditions or from Ti₆-NDS under different conditions and the one obtained from a commercial source. The mechanistic study indicates that the hierarchical structure surrounding the Ti-oxide cores of Ti₆-NDS is pivotal for the formation and the SIB performance of the porous TiO₂. This surfactant-free and catalyst-free strategy for the fabrication of TiO₂ materials with special morphologies by thermal transformation of a TOC provides a new optional protocol for the preparation of promising materials stable and efficient in SIBs.

4.    Gas-Phase Oxidation of Allyl Acetate by O₃, OH, Cl, and NO₃: Reaction Kinetics and Mechanism

By Wang, Shuyan; Du, Lin; Zhu, Jianqiang; Tsona, Narcisse T.; Liu, Shijie; Wang, Yifeng; Ge, Maofa; Wang, Wenxing

From Journal of Physical Chemistry A (2018), 122(6), 1600-1611.https://pubs.acs.org/doi/10.1021/acs.jpca.7b10599 

Allyl acetate (AA) is widely used as monomer and intermediate in industrial chemicals synthesis. To evaluate the atmospheric outcome of AA, kinetics and mechanism of its gas-phase reaction with main atmospheric oxidants (O₃, OH, Cl, and NO₃) have been investigated in a Teflon reactor at 298 ± 3 K.Both absolute and relative rate methods were used to determine the rate constants for AA reactions with the four atmospheric oxidants. The obtained rate constants (in units of cm³ molecule^–1 s^–1) are (1.8 ± 0.3) × 10^–18, (3.1 ± 0.7) × 10^–11, (2.5 ± 0.5) × 10^–10, and (1.1 ± 0.4) × 10^–14, for reactions with O₃, OH, Cl, and NO₃, respectively. While results for reactions with O₃, OH and Cl are in good agreement with previous studies, the kinetics for the reaction with NO3 is reported for the first time in this study. On the basis of determined rate constants, the tropospheric lifetimes of AA are τO₃ = 9 days, τOH = 5 h, τCl = 5 days, τNO₃ = 2 days. On the basis of the products study, reaction mechanisms for these oxidations have been proposed and the reaction products were detected using thermal desorption–gas chromatography–mass spectrometry (TD–GC–MS) and Fourier transform infrared spectroscopy (FTIR). Results show that the main products formed in these reactions are carbonyl compounds. In particular, 2-oxoethyl acetate was detected in all four AA oxidation reactions. Compared to previous studies, several new products were determined for reactions with OH and Cl. These results form a set of comprehensive kinetic data for AA reactions with main atmospheric oxidants and provide a better understanding of the degradation and atmospheric outcome of unsaturated acetate esters in the troposphere, during both daytime and nighttime.

                                       

5.    Aqueous Isolation of 17-Nuclear Zr/Hf Oxide Clusters during the Hydrothermal Synthesis of ZrO₂/HfO₂

Sun, Qing; Liu, Caiyun; Zhang, Guanyun; Zhang, Jian; Tung, Chen-Ho; Wang, Yifeng

Chemistry - A EuropeanJournal (2018), 24(55), 14701-14706

 https://onlinelibrary.wiley.com/doi/full/10.1002/chem.201801267

Novel 17‐nuclear Zr/Hf oxide clusters ({Zr₁₇} and {Hf₁₇}) are isolated from aqueous systems. In the clusters, Zr/Hf ions are connected through μ3-O, μ3-OH, and μ2-OH linkages into a pinwheel core which is wrapped with SO₄²⁻, HCOO⁻, and aqua ligands. Octahedral hexanuclear Zr/Hf oxide clusters ({Zr₆}oct and {Hf₆}oct) are also isolated from the same hydrothermal system by decreasing the synthesis temperature. This study not only adds new members to the Zr/Hf oxide cluster family, but also establishes a connection from Zr⁴⁺ ions to ZrO₂ in the hydrothermal preparation of zirconium oxide nanomaterials.

 

6.    Selective endoperoxide formation by heterogeneous TiO₂ photocatalysis with dioxygen

Qiao, Xiaofeng; Biswas, Subharanjan; Wu, Wenli; Zhu, Feng; Tung, Chen-Ho; Wang, Yifeng

Tetrahedron (2018), 74(20), 2421-2427.

 https://www.sciencedirect.com/science/article/pii/S0040402018303053?via%3Dihub

We report the selective formation of endoperoxides by aerobic TiO₂ photocatalysis through the cyclic addition of dioxygen and a non-conjugated diene, the first heterogeneous catalytic system for endoperoxide synthesis. This green protocol does not require any additive and the photocatalyst is abundant and recyclable, providing a yield up to 64% and >20:1 diastereoselectivity. Mechanistic investigations were carried out by using product analysis, kinetic studies, O-18 labelling experiments, electron-spin resonance and a set of quenching experiments. Superoxide (but not singlet oxygen, triplet oxygen or peroxide) is directly involved in the reaction cascade to form the endoperoxide product. The new findings may be helpful for future for designing eco-friendly and energy sustainable strategies for selective oxygenation reactions using semiconductors, O₂ and sunlight.

7.    Titanium-oxide host clusters with exchangeable guests

Zhang, Guanyun; Li, Wenyun; Liu, Caiyun; Jia, Jiong; Tung, Chen-Ho; Wang, Yifeng

Journal of the American Chemical Society (2018), 140(1), 66-69. https://pubs.acs.org/doi/10.1021/jacs.7b10565

A novel family of water-sol., polyoxocationic titanium-oxide host-guest clusters are reported herein.  They exhibit an unprecedented hexagonal prismatic core structure for hosting univalent cationic guests like K⁺, Rb⁺, Cs⁺ and H₃O⁺. Guest exchange has been studied using ¹³³Cs NMR, showing the flexible pore of a host permits passage of a comparatively larger cation and giving an equilibrium constant of ca. 13 for displacing Rb⁺ by Cs⁺. Attractive ion-dipole interaction, depending on host–guest size complementarity, plays a dominant role for the preferential encapsulation of larger alkali-metal cationic guests.

8.     Influence of Polyoxometalate Protecting Ligands on Catalytic Aerobic Oxidation at the Surfaces of Gold Nanoparticles in Water

Zhang, Mingfu; Hao, Jingcheng; Neyman, Alevtina; Wang, Yifeng; Weinstock, Ira A.

Inorganic Chemistry (2017), 56(5), 2400-2408.  https://pubs.acs.org/doi/10.1021/acs.inorgchem.6b02167

Metal oxide cluster-anion (polyoxometalate, or POM) protecting ligands, [α-PW11O₃₉]^7– (1), modify the rates at which 14 nm gold nanoparticles (Au NPs) catalyze an important model reaction, the aerobic (O₂) oxidation of CO to CO₂ in water. At 20 °C and pH 6.2, the following stoichiometry was observed: CO + O₂ + H₂O = CO₂ + H₂O₂. After control experiments verified that the H₂O₂ product was sufficiently stable and did not react with 1 under turnover conditions, quantitative analysis of H₂O₂ was used to monitor the rates of CO oxidation, which increased linearly with the percent coverage of the Au NPs by 1 (0–64% coverage, with the latter value corresponding to 211 ± 19 surface-bound molecules of 1). X-ray photoelectron spectroscopy of Au NPs protected by a series of POM ligands (K+ salts): 1, the Wells–Dawson ion [α-P₂W₁₈O₆₂]^6– (2) and the monodefect Keggin anion [α-SiW₁₁O₃₉]^8– (3) revealed that binding energies of electrons in the Au 4f7/2 and 4f5/2 atomic orbitals decreased as a linear function of the POM charge and percent coverage of Au NPs, providing a direct correlation between the electronic effects of the POMs bound to the surfaces of the Au NPs and the rates of CO oxidation by O₂. Additional data show that this effect is not limited to POMs but occurs, albeit to a lesser extent, when common anions capable of binding to Au-NP surfaces, such as citrate or phosphate, are present.

9.    Iodine/Visible Light Photocatalysis for Activation of Alkynes for Electrophilic Cyclization Reactions

Liu, Yuliang; Wang, Bin; Qiao, Xiaofeng; Tung, Chen-Ho; Wang, Yifeng

ACS Catalysis (2017), 7(6), 4093-4099.  https://pubs.acs.org/doi/10.1021/acscatal.7b00799

Photocatalytic organic synthesis needs photocatalysts to initiate the reactions and to control the reaction paths. Available photocatalytic systems rely on electron transfer or energy transfer between the photoexcited catalysts and the substrates. We explore a concept based on the photopromoted catalyst coupling to the substrate and the phototriggered catalyst regeneration by elimination from the catalytic cycle. A catalytic amount of elementary I2 is applied as both a visible light photocatalyst and a π Lewis acid, enabling the direct activation of alkyne C≡C bonds for electrophilic cyclization reactions, one of the most important reactions of alkynes. Visible light is crucial for both the iodocyclization of the propargyl amide and the deiodination of the intermediate. Singlet oxygen is found to play a key role in the regeneration of I₂. This system shows good functional group compatibility for the generation of substituted oxazole aldehydes and indole aldehydes. Hence, this study provides a readily accessible alternative catalytic system for the construction of heterocycle aldehyde derivatives by sunlight photocatalysis.

10.         Atmospheric oxidation of selected chlorinated alkenes by O₃, OH, NO₃ and Cl

Zhang, Qun; Chen, Yi; Tong, Shengrui; Ge, Maofa; Shenolikar, Justin; Johnson, Matthew S.; Wang, Yifeng; Tsona, Narcisse T.; Mellouki, Abdelwahid; Du, Lin

Atmospheric Environment (2017), 170, 12-21. https://www.sciencedirect.com/science/article/pii/S1352231017306301?via%3Dihub

An experimental study on the 3-chloro-2-methyl-1-propene (CMP), 2,3-dichloropropene (DCP) and 3,4-dichlorobutene (DCB) reactions with atmospheric oxidants at (298 ± 1) K and atmospheric pressure is reported. Rate constants for the gas phase reactions of the three chlorinated alkenes with O₃, OH and NO₃ radicals and Cl atom were determined in a 100 L Teflon reactor by gas chromatography with flame ionization detector (GC-FID). The obtained rate constants are (3.03 ± 0.15) × 10⁻¹⁸, (3.83 ± 1.30) × 10⁻¹¹, (1.99 ± 0.19) × 10⁻¹⁴, and (2.40 ± 0.41) × 10⁻¹⁰ cm³ molecule⁻¹ s⁻¹ for CMP reactions with O3, OH, NO3, and Cl, respectively, (4.62 ± 1.41) × 10⁻²⁰, (1.37 ± 1.02) × 10⁻¹¹, (1.45 ± 0.15) × 10⁻¹⁵ and (1.30 ± 0.99) × 10⁻¹¹ cm³ molecule⁻¹ s⁻¹ for DCP reactions and (2.09 ± 0.24) × 10⁻¹⁹, (1.45 ± 0.59) × 10⁻¹¹, (3.00 ± 0.82) × 10⁻¹⁶ and (1.91 ± 0.19) × 10⁻¹⁰ cm³ molecule⁻¹ s−¹ for DCB reactions. The CMP reaction products were detected and possible reaction mechanisms of their formation were proposed. Chloroacetone was found to be the major product in all four oxidation reactions. The loss process of CMP in the atmosphere is mostly controlled by its reaction with the OH radical during daytime and with NO₃ during nighttime, with lifetimes of 3.6 h and 27.9 h respectively. Atmospheric implications of both these reactions and their potential products are discussed.

11.         Gas-Phase Reaction of Methyl n-Propyl Ether with OH, NO₃, and Cl: Kinetics and Mechanism

Zhu, Jianqiang; Wang, Shuyan; Tsona, Narcisse T.; Jiang, Xiaotong; Wang, Yifeng; Ge, Maofa; Du, Lin

Journal of Physical Chemistry A (2017), 121(36), 6800-6809.  https://pubs.acs.org/doi/10.1021/acs.jpca.7b06877

Rate constants at room temperature (293 ± 2 K) and atmospheric pressure for the reaction of methyl n-propyl ether (MnPE), CH₃OCH₂CH₂CH₃, with OH and NO₃ radicals and the Cl atom have been determined in a 100 L FEP-Teflon reaction chamber in conjunction with gas chromatography-flame ionization detector (GC-FID) as the detection technique. The obtained rate constants k (in units of cm3 molecule^–1 s^–1) are (9.91 ± 2.30) × 10^–12, (1.67 ± 0.32) × 10^–15, and (2.52 ± 0.14) × 10^–10 for reactions with OH, NO₃, and Cl, respectively. The products of these reactions were investigated by gas chromatography-mass spectrometry (GC-MS), and formation mechanisms are proposed for the observed reaction products. Atmospheric lifetimes of the studied ether, calculated from rate constants of the different reactions, reveal that the dominant loss process for MnPE is its reaction with OH, while in coastal areas and in the marine boundary layer, MnPE loss by Cl reaction is also important.

12.         One-Pot Synthesis of Size-Controllable Core-Shell CdS and Derived CdS@Zn_xCd1-xS Structures for Photocatalytic Hydrogen Production

Kai, Shuangshuang; Xi, Baojuan; Wang, Yifeng; Xiong, Shengli

Chemistry - A European Journal (2017), 23(65), 16653-16659. https://onlinelibrary.wiley.com/doi/full/10.1002/chem.201703506

Chalcogenide micro/nanocomposite structures have been attracting worldwide attention due to prospective applications in photocatalytic hydrogen production. Well‐defined micro/nanostructures with pronounced properties are of extraordinary importance. Herein, a facile one‐pot method for the synthesis of monodisperse, size‐controllable CdS core–shell and CdS@Zn_xCd_1−xS core–double shell submicrospheres, which were engineered with respect to structure and size, is reported.CdS core–shell submicrospheres with different sizes were selectively prepared for the first time. The growth mechanism was investigated in detail by monitoring the time‐dependent morphology of intermediates by TEM. By introduction of a zinc precursor in the synthetic system, CdS@Zn_xCd_1−xS core–double shell submicrospheres were obtained by cation exchange of CdS with zinc ions, with a process of diffusion of CdS towards the outside and transformation of Zn_xCd_1−xS crystallites. The H₂ evolution rate over CdS@Cd_xZn_1−xS (5.17 mmol h⁻¹g⁻¹) is 12.3 times that of CdS core–shell structures (0.42 mmol h⁻¹ g⁻¹) under visible light, owing to the efficient charge separation, as demonstrated by electrochemical impedance and transient‐state time‐resolved photoluminescence spectroscopy. Furthermore, CdS@Zn_xCd_1−xS core–double shell structures exhibited excellent stability over 20 h of hydrogen production.

13.         A Post-Functionalizable Iso-Polyoxotitanate Cage Cluster

Hou, Jie; Hu, Junyi; Sun, Qing; Zhang, Guanyun; Tung, Chen-Ho; Wang, Yifeng

Inorganic Chemistry (2016), 55(14), 7075-7078.https://pubs.acs.org/doi/10.1021/acs.inorgchem.6b00982

During solvothermal alcoholysis of a mixture of TiI₄ and Ti(OiPr)₄, a {I@Ti₂₂} cage cluster encapsulating an OH and iodide guests is crystallized. The {I@Ti₂₂} host–guest cluster surface is postfunctionalizable with catecholate and carboxylate ligands. The synthetic details, structural characterization, spectroscopic properties of the obtained cages clusters are provided. The present study provides candidates for modeling ligand exchange and electron-hole transfer at the titanate nanoparticle surface, and meanwhile offers new opportunities for understanding the TiO₂ nanocrystalline formation in solvothermal processes.

14.         Alkali Halide Cubic Cluster Anions ([Cs₈X₂₇]^19-, X = Cl, Br) Isolated from Water

Sun, Qing; Zhang, Guanyun; Tung, Chen-Ho; Wang, Yifeng

Inorganic Chemistry (2016), 55(21), 11125-11130. https://pubs.acs.org/doi/10.1021/acs.inorgchem.6b01741

Herein we report the syntheses and the X-ray structure of [Cs₈X₂₇]^19- (X = Cl, Br) clusters, the first binary cluster anions isolated in bulk crystal structures. This work not only provides structural models for a better understanding of the nucleation of binary materials but also shows that magic number binary clusters adopting a cubic lattice structure do form, in agreement with the time-honored theoretical and spectroscopic predictions.

15.         Chemoselective Claisen-Schmidt bis-substitutional condensation catalyzed by an alkoxy-bridged dinuclear Ti(IV) cluster

Wu, Yufei; Hou, Jie; Liu, Yuliang; Zhang, Mingfu; Tung, Chen-Ho; Wang, Yifeng

Tetrahedron (2016), 72(12), 1511-1516. 

https://www.sciencedirect.com/science/article/pii/S0040402016300552?via%3Dihub

The highly efficient and chemoselective α,α′-bis-substitution of alkanones is important in organic synthesis. Herein, a dimeric titanium cluster, Ti₂Cl₂(OPrⁱ)₆·2HOPrⁱ (Ti₂), is used in the Claisen–Schmidt condensation reaction, for the selectively activation of symmetrical ketones containing α,α′-methylene groups and production of α,α′-bis-substituted alkanones in high efficiency and chemoselectivity. 

16.         Counteranion-Stabilized Titanium(IV) Isopolyoxocationic Clusters Isolated from Water

Zhang, Guanyun; Hou, Jie; Li, Mingzhong; Tung, Chen-Ho; Wang, Yifeng

Inorganic Chemistry (2016), 55(10), 4704-4709.https://pubs.acs.org/doi/10.1021/acs.inorgchem.5b01901

A novel titanium(IV) oxo cluster comprised solely of Ti, O, and H atoms, [Ti₆(O_μ)8(OtH₂)₂₀]⁸⁺ (Ti₆) was synthesized in high yield via controlled hydrolysis and condensation of TiX₄ (X = Cl, Br) in the presence of TBAX (TBA = tetrabutylammonium; X = Cl, Br) from water, while reactions of TiI₄ and TBAI yielded [Ti₈O₁₂(OH₂)₂₄]⁸⁺ (Ti₈). The structures and compositions of the clusters were determined by single-crystal X-ray crystallography, powder X-ray diffraction, inductively coupled plasma atomic emission spectrometry, and energy-dispersive spectrometry. Ti₆ is comprised of six-coordinated titanium(IV) atoms bridged with μ2-O atoms, structurally similar to a typical Lindqvist polyoxometalate. On the basis of a structural comparison of Ti₆ and Ti₈, density functional theory calculations, and spectroscopic analysis, it is evident that both clusters are stabilized by halide counteranions via the formation of hydrogen bonds. This study not only presents the second example of a titanium(IV) isopolyoxocationic cluster isolated from water but also suggests that counteranions are generally important for synthesizing molecular fragments of titanium oxides.

17.         Effects of Substitutional Dopants on the Photoresponse of a Polyoxotitanate Cluster

Hu, Junyi; Zhan, Lijie; Zhang, Guanyun; Zhang, Qun; Du, Lin; Tung, Chen-Ho; Wang, Yifeng

Inorganic Chemistry (2016), 55(17), 8493-8501. https://pubs.acs.org/doi/10.1021/acs.inorgchem.6b01071

In this paper ,Using a simple method, 17 isostructural polyoxotitanates (POTs) were synthesized, including the pristine [Ti₁₂O₁₆(OⁱPr)₁₆], the monodefected [Ti₁₁O₁₃(OⁱPr)₁₈], and the heterometal-doped [Ti₁₁O₁₄(OⁱPr)₁₇(ML)] (M = Mg, Ca, Zn, Cd, Co, or Ni; L = Cl, Br, I, or NO₃).  The electronic structures of these POTs were determined by UV–vis spectroscopy and DFT calculations. Upon UV irradiation of the POTs, electron spin resonance showed the formation of TiIII under anaerobic conditions and superoxide (O₂^•–) in the presence of O₂. The photoactivities of the POTs were then probed with TiIII production and short-circuit photocurrent experiments. The photophysical processes were studied using steady-state and transient photoluminescence. The results show that within the very similar structures, the deexcitation processes of the photoexcited POTs can be greatly affected by the dopants, which result in enhanced or decreased photoactivities. Co and Ni doping enhances the absorption of the visible light accompanied by serious loss of UV photoactivities. On the other hand, a Ti vacancy (in [Ti₁₁O₁₃(OⁱPr)₁₈]) does not reduce the band gap of a POT but improves the UV photoactivities by serving as surface reaction site. The POTs were then used as molecular models of titanium oxide nanoparticles to understand some important issues relevant to doped titanate, i.e., coordination environment of the dopant metal, electronic structure, photoactivities, and photophysical processes. Our present findings suggest that for solar energy harvesting applications of titanium oxides like photocatalysis and solar cells substitution of titanium atoms by transition metal ions (like Co and Ni) to extend the absorption edges may not be an efficient way, while loading of Ti vacancies is very effective.

 

18.         Interfacial charge transfer in a functionalized polyoxotitanate cluster

Hou, Jie; Zhang, Qun; Wu, Yufei; Liu, Yuliang; Du, Lin; Tung, Chen-Ho; Wang, Yifeng

Inorganica Chimica Acta (2016), 443, 279-283.  

https://www.sciencedirect.com/science/article/pii/S0020169316000281?via%3Dihub

Understanding the charge transfer processes at the dye/TiO₂ interface is often modeled using catechol/TiO₂ systems. However, it indeed require precise structural information. In order to simulate the dye/TiO₂ systems at a molecular level, herein we report the synthesis and structure of a novel titanium oxo-cluster [Ti₄O(OⁱPr)₆(DTBC)₄] (1) functionalized with 3,5-di-tert-butylcatechol (DTBC). UV–Vis spectroscopy, electron spin resonance (ESR), X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) calculations show that 1 exhibits property of Ti(III) which is caused by substantial charge transfer from the π electrons of the benzene rings to Ti3d orbitals. The present precise structure and charge transfer mechanism help to better understand chromophore binding to semiconductor surfaces and charge transfer at the dye/TiO₂ interfaces.

19.         Small Titanium Oxo Clusters: Primary Structures of Titanium(IV) in Water

Zhang, Guanyun; Hou, Jie; Tung, Chen-Ho; Wang, Yifeng

Inorganic Chemistry (2016), 55(7), 3212-3214. https://pubs.acs.org/doi/10.1021/acs.inorgchem.6b00129

For sol–gel synthesis of titanium oxide, the titanium(IV) precursors are dissolved in water to form clear solutions. However, the solution status of titanium(IV) remains unclear. Herein three new and rare types of titanium oxo clusters are isolated from aqueous solutions of TiOSO₄ and TiCl₄without using organic ligands. Our results indicate that titanium(IV) is readily hydrolyzed into oxo oligomers even in highly acidic solutions. The present clusters provide precise structural information for future characterization of the solution species and structural evolution of titanium(IV) in water and, meanwhile, are new molecular materials for photocatalysis.

20.         TiO₂ Photocatalytic Cyclization Reactions for the Syntheses of Aryltetralones

Liu, Yuliang; Zhang, Mingfu; Tung, Chen-Ho; Wang, Yifeng

ACS Catalysis (2016), 6(12), 8389-8394. https://pubs.acs.org/doi/10.1021/acscatal.6b03076

This work focuses on a new strategy to overcome the overoxidation in heterogeneous TiO₂ photocatalysis and to realize high-efficiency photosynthesis. We demonstrate that TiO₂ photocatalysis can integrate C–C and C═O formation in a tandem manner to achieve efficient oxidative cyclization for the syntheses of aryltetralones. This protocol does not need any additive besides the inexpensive and/or recyclable TiO₂, O₂, and (solar) light. High yields with excellent diastereoselectivities are obtained for a wide scope of electron-rich substrates. Our findings demonstrate that in contrast to the conventional overoxidation, as long as the radical cations possess sufficient reactivity toward nucleophilic addition, single-electron transfer processes in TiO₂ photocatalysis can be developed into a powerful tool to construct C–C bonds and even strained carbon rings.

21.         Water-Soluble Pentagonal-Prismatic Titanium-Oxo Clusters

Zhang, Guanyun; Liu, Caiyun; Long, De-Liang; Cronin, Leroy; Tung, Chen-Ho; Wang, Yifeng

Journal of the American Chemical Society (2016), 138(35), 11097-11100.  

https://pubs.acs.org/doi/10.1021/jacs.6b06290

The cluster cores are wrapped by external sulfate and aqua ligands, showing good solubilities and stabilities in a variety of solvents including acetonitrile and water and allowing their solution chemistry being studied by means of electrospray ionization mass spectroscopy, ¹⁷O NMR, and vibrational spectroscopy. Furthermore, this study provides new titanium oxide candidates for surface modifications and homogeneous photocatalysis.

22.         Electrocatalysis by Polyoxometalate-Protected Gold Nanoparticles

Zhang, Mingfu; Weinstock, Ira A.; Wang, Yifeng

Journal of Cluster Science (2014), 25(3), 771-779.

 https://link.springer.com/article/10.1007%2Fs10876-013-0642-8

Electrocatalysis by polyoxometalate (POM)-monolayer protected gold nanoparticles is herein demonstrated using a newly discovered phenomenon that makes it possible to observe the electrochemistry of dilute aqueous solutions of these colloidal nanostructures. To preserve the integrity of the gold nanoparticles’electrostatically-stabilized POM-monolayer structures, deposition and drying of the POM-protected metal(0) NPs on the electrode surface must be avoided. Overcoming this constraint, we here show that POM-monolayer protected gold nanoparticles can be induced to reversibly associate with electrode surfaces, resulting in dramatic current amplification and well behaved, quasi-reversible cyclic voltammetric behavior at remarkably small electrolyte concentrations, thus making it possible to investigate electrocatalysis by dilute aqueous solutions of POM-protected gold NPs.

23.         Polyoxometalate-Engineered Building Blocks with Gold Cores for the Self-Assembly of Responsive Water-Soluble Nanostructures

Wang, Yizhan; Raula, Manoj; Wang, Yifeng; Zeiri, Offer; Chakraborty, Sourav; Gan-Or, Gal; Gadot, Eyal; Weinstock, Ira A.

Angewandte Chemie, International Edition (2017), 56(25), 7083-7087.  https://onlinelibrary.wiley.com/doi/full/10.1002/anie.201701723

The controlled assembly of Au nanoparticles (AuNPs) with the size of quantum dots into predictable structures is extremely challenging as it requires the quant. and topol. precise placement of anisotropic domains on their small, approx. spherical surfaces.  The authors herein address this problem by using polyoxometalate leaving groups to transform 2 nm diameter gold cores into reactive building blocks with hydrophilic and hydrophobic surface domains whose relative sizes can be precisely tuned to give dimers, clusters, and larger micelle‐like organizations. Using cryo‐TEM imaging and 1H DOSY NMR spectroscopy, we then provide an unprecedented “solution‐state” picture of how the micelle‐like structures respond to hydrophobic guests by encapsulating them within 250 nm diameter vesicles whose walls are comprised of amphiphilic AuNP membranes. These findings provide a versatile new option for transforming very small AuNPs into precisely tailored building blocks for the rational design of functional water‐soluble assemblies.

24.         Polyoxometalate Complexes of Anatase-Titanium Dioxide Cores in Water

Raula, Manoj; Gan Or, Gal; Saganovich, Marina; Zeiri, Offer; Wang, Yifeng; Chierotti, Michele R.; Gobetto, Roberto; Weinstock, Ira A.

Angewandte Chemie, International Edition (2015), 54(42), 12416-12421. 

https://onlinelibrary.wiley.com/doi/full/10.1002/anie.201501941

Polyoxometalate (POM) cluster anions are shown to serve as covalently coordinated ligands for anatase‐TiO₂ nanocrystals, giving isolable assemblies uniquely positioned between molecular macroanions and traditional colloidal nanoparticles. Na+ salts of the water‐soluble polyanionic structures are obtained by reacting amorphous TiO₂ with the 1 nm lacunary ion, Na₇[α‐XW₁₁O₃₉] (X=P⁵⁺), at 170 °C, after which an average of 55 α‐PW₁₁O₃₉⁷⁻ clusters are found as pentadentate ligands for TiIV ions covalently linked to 6 nm single‐crystal anatase cores. The attached POMs are reversible electron acceptors, the reduction potentials of which shift in a predictable fashion by changing the central heteroatom, X, directly influencing a model catalytic reaction. Just as POM cluster anions control the reactivities of metal centers in molecular complexes, directly coordinated POM ligands with tunable redox potentials now provide new options for rationally controlling the reactions of semiconductor nanocrystals.

25.         Addressing a "Black Box" of Bottom-Up Synthesis: Revealing the Structures of Growing Colloidal-Nanocrystal Nuclei

Sobol, Oded; Gadot, Eyal; Wang, Yifeng; Weinstock, Ira A.; Meshi, Louisa

Inorganic Chemistry (2015), 54(22), 10521-10523.https://pubs.acs.org/doi/10.1021/acs.inorgchem.5b01562

In bottom-up synthesis, products from reactions of structural building units rapidly pass from sol. mol. complexes to nanoscale intermediates, whose soln.-state structures defy elucidation by any routine method.  To address this, electron diffraction is used to reveal the structures of cryogenically "trapped" colloidal nanocrystals.

26.         Ligand-Shell-Directed Assembly and Depolymerization of Patchy Nanoparticles

Zeiri, Offer; Wang, Yifeng; Neyman, Alevtina; Stellacci, Francesco; Weinstock, Ira A.

From Angewandte Chemie, International Edition (2013), 52(3), 968-972.

https://onlinelibrary.wiley.com/doi/full/10.1002/anie.201207177

 Unprecedented insertions of cationic alkanethiols, HS(CH₂)₁₁N(CH₃)₃⁺, between polyoxometalate protecting ligands, α-AlW₁₁O₃₉^9-, and the surfaces of gold nanoparticles, give "zwitterionic" patchy nanoparticles (PNs).  Their shell structures and assembly properties vary with particle size during rational in situ modifications that lead to three‐component core–shell aggregates never observed before in PNs. 

27.         Polyoxometalate-protected metal nanoparticles: synthesis structure and catalysis

Wang, Yifeng; Weinstock, Ira A.

World Scientific Series in Nanoscience and Nanotechnology (2013), 8(Polyoxometalate Chemistry), 1-47.

http://xueshu.baidu.com/usercenter/paper/show?paperid=2a1d652e40898ef0c33fdaafa71ed546&site=xueshu_se&qq-pf-to=pcqq.c2c

This article discusses the synthesis, structure and catalysis of polyoxometalate (POM)-stabilized metal(0) nanoparticles.  The redns. of metal cations to metal(O) nanoparticles by traditional reducing agents, but in the presence of POM ligands was described.  The structures of POM-stabilized metal(0) nanoparticles, including important observations from many groups, along with a detailed summary of new findings obtained with the aid of cryo-TEM imaging was discussed.

28.         Regioselective placement of alkanethiolate domains on tetrahedral and octahedral gold nanocrystals

Wang, Yifeng; Zeiri, Offer; Meshi, Louisa; Stellacci, Francesco; Weinstock, Ira A.

Chemical Communications (Cambridge, United Kingdom) (2012), 48(78), 9765-9767.

https://pubs.rsc.org/en/content/articlelanding/2012/CC/c2cc34697d#!divAbstract

Electrostatically stabilized monolayer shells of metal-oxide cluster anions (polyoxometalates, or POMs) on the surfaces of ∼8 nm tetrahedral and octahedral Au nanocrystals regioselectively direct H₂O-sol. alkanethiolate ligands to the corners and edges of the Au polyhedra.

29.         Nucleation and Island Growth of Alkanethiolate Ligand Domains on Gold Nanoparticles

Wang, Yifeng; Zeiri, Offer; Neyman, Alevtina; Stellacci, Francesco; Weinstock, Ira A.

ACS Nano (2012), 6(1), 629-640. https://pubs.acs.org/doi/10.1021/nn204078w

The metal oxide cluster α-AlW₁₁O₃₉^9– (1), readily imaged by cryogenic transmission electron microscopy (cryo-TEM), is used as a diagnostic protecting anion to investigate the self-assembly of alkanethiolate monolayers on electrostatically stabilized gold nanoparticles in water.  Monolayers of 1 on 13.8 ± 0.9 nm diameter gold nanoparticles are displaced from the gold surface by mercaptoundecacarboxylate, HS(CH₂)₁₀CO₂– (11-MU). During this process, no aggregation is observed by UV–vis spectroscopy, and the intermediate ligand-shell organizations of 1 in cryo-TEM images indicate the presence of growing hydrophobic domains, or “islands”, of alkanethiolates. UV–vis spectroscopic “titrations”, based on changes in the surface plasmon resonance upon exchange of 1 by thiol, reveal that the 330 ± 30 molecules of 1 initially present on each gold nanoparticle are eventually replaced by 2800 ± 30 molecules of 11-MU. UV–vis kinetic data for 11-MU-monolayer formation reveal a slow phase, followed by rapid self-assembly. The Johnson, Mehl, Avrami, and Kolmogorov model gives an Avrami parameter of 2.9, indicating continuous nucleation and two-dimensional island growth. During nucleation, incoming 11-MU ligands irreversibly displace 1 from the Au-NP surface via an associative mechanism, with knucleation = (6.1 ± 0.4) × 10² M^–1 s^–1, and 19 ± 8 nuclei, each comprised of ca. 8 alkanethiolates, appear on the gold-nanoparticle surface before rapid growth becomes kinetically dominant. Island growth is also first-order in [11-MU], and its larger rate constant, kgrowth, (2.3 ± 0.2) × 104 M^–1 s^–1, is consistent with destabilization of molecules of 1 at the boundaries between the hydrophobic (alkanethiolate) and the electrostatically stabilized (inorganic) domains.

30.         Orientations of polyoxometalate anions on gold nanoparticles

Sharet, Shelly; Sandars, Ella; Wang, Yifeng; Zeiri, Offer; Neyman, Alevtina; Meshi, Louisa; Weinstock, Ira A.

Dalton Transactions (2012), 41(33), 9849-9851.

https://pubs.rsc.org/en/content/articlelanding/2012/DT/c2dt30592e#!divAbstract

Cryogenic TEM of polyoxometalate-protected gold nanoparticles reveals that the Preyssler ion, [NaP₅W₃₀O₁₁₀]^14-, lies face down with its C₅ axis perpendicular to the Au surface, while the Finke-Droege ion, [P₄W₃₀Zn₄(H₂O)₂O₁₁₂]^16-, is tilted, with its long axis close to 60° from the normal to the surface.

31.         Role of the Alkali-Metal Cation Size in the Self-Assembly of Polyoxometalate-Monolayer Shells on Gold Nanoparticles

Wang, Yifeng; Zeiri, Offer; Sharet, Shelly; Weinstock, Ira A.

Inorganic Chemistry (2012), 51(14), 7436-7438. https://pubs.acs.org/doi/10.1021/ic300431a

olyoxometalate (POM)-monolayer stability consts., K, for three POM anions vary with the cation size, in the same order as that for increasing ion-pair formation with α-SiW₁₁O₃₉^8- (1) in the early nucleation phase of monolayer self-assembly: Li⁺ < Na⁺ < K⁺ < Cs⁺.  Cryo-TEM images demonstrating the use of the cation size to rationally control monolayer formation provide definitive evidence that the POM monolayers are electrostatically stabilized (ionic) shells, analogous in that respect to the monolayer walls of "hollow" POM-macroanion vesicles.

32.         Polyoxometalate-decorated nanoparticles

Wang, Yifeng; Weinstock, Ira A.

Chemical Society Reviews (2012), 41(22), 7479-7496.

https://pubs.rsc.org/en/content/articlelanding/2012/CS/c2cs35126a#!divAbstract

Polyoxometalate cluster anions (POMs) control formation and morphol., and serve as protecting ligands, for structurally and compositionally diverse nanostructures.  While numerous examples of POM-protected metal(0) nanoparticle syntheses and reactions can now be found in the literature, the use of POMs to prep. nano-scale analogs of binary inorg. materials, such as metal-oxides, sulfides and halides, is a relatively recent development.

33.         The reduction of dioxygen by Keggin heteropolytungstates

Snir, Ophir; Wang, Yifeng; Weinstock, Ira A.

Israel Journal of Chemistry (2011), 51(2), 247-258.  https://onlinelibrary.wiley.com/doi/full/10.1002/ijch.201100026

Reversible redox chemistries are an inherent feature of numerous metal oxide cluster anions (POMs). Moreover, as discrete molecular structures with well‐defined and controllable solution chemistries, POMs can be deployed as physicochemical probes for studying inorganic reaction mechanisms.

34.         Polyoxometalate-directed assembly of water-soluble AgCl nanocubes

Neyman, Alevtina; Wang, Yifeng; Sharet, Shelly; Varsano, Neta; Botar, Bogdan; Koegerler, Paul; Meshi, Louisa; Weinstock, Ira A.

Chemical Communications (Cambridge, United Kingdom) (2012), 48(16), 2207-2209.

https://pubs.rsc.org/en/content/articlelanding/2012/CC/c2cc16322e#!divAbstract

Out-of-pocket assocn. of Ag⁺ to the tetradentate defect site of mono-vacant Keggin and Wells-Dawson polyoxometalate (POM) cluster-anions was used to direct the formation of water-sol. AgCl nanocubes.

35.         Reversible binding of an inorganic cluster-anion to the surface of a gold nanoparticle

Wang, Yifeng; Zeiri, Offer; Gitis, Vitaly; Neyman, Alevtina; Weinstock, Ira A.

Inorganica Chimica Acta (2010), 363(15), 4416-4420.

https://www.sciencedirect.com/science/article/pii/S0020169310004202?via%3Dihub

Reversible dissocn of POM ligands from electrostatically stabilized monolayer assemblies on metal(0)-nanoparticle surfaces would provide substrates with direct access to reactive metal(0) lattices.  As a result, POM-ligand lability could play an important role in catalysis by POM-monolayer protected metal(0) nanoparticles.  POM-ligand lability was addressed by 1st obtained cryogenic TEM (cryo-TEM) images of monolayers of α-AlW11O9-39 on a 5.4 nm diam. gold-core nanoparticle.

36.         Concerted Proton-Electron Transfer to Dioxygen in Water

By Snir, Ophir; Wang, Yifeng; Tuckerman, Mark E.; Geletii, Yurii V.; Weinstock, Ira A.

From Journal of the American Chemical Society (2010), 132(33), 11678-11691. https://pubs.acs.org/doi/10.1021/ja104392k

Concerted proton−electron transfer (CPET) is documented for the homogeneous reduction of O₂ to HO₂^• in water by the one-electron-reduced heteropolytungstate anion, α-PW₁₂O₄₀⁴⁻ (1_1e). At 0.01−0.3 M H⁺, O₂reduction occurs via outer-sphere electron transfer followed by proton transfer (ETPT, with rate constant k_ET).

37.         Cation mediated self-assembly of inorganic cluster anion building blocks

Wang, Yifeng; Weinstock, Ira A.

Dalton Transactions (2010), 39(27), 6143-6152.

https://pubs.rsc.org/en/content/articlelanding/2010/DT/c0dt00166j#!divAbstract

Polyoxometalate (POM) cluster anions form highly organized monolayers on planar surfaces, stabilize metal nanoparticles in soln., and serve as structural components of hollow, single-walled vesicles.  Until recently, each of these classes of superstructures was viewed as fundamentally distinct.  Now, however, new data show that metal nanoparticles serve as templates for the assembly of spherical, metal-core-supported POM monolayers.

38.         Sonochemical Hydrogen Production Efficiently Catalyzed by Au/TiO2

Wang, Yifeng; Zhao, Dan; Ji, Hongwei; Liu, Guilin; Chen, Chuncheng; Ma, Wanhong; Zhu, Huaiyong; Zhao, Jincai

Journal of Physical Chemistry C (2010), 114(41), 17728-17733.https://pubs.acs.org/doi/10.1021/jp105691v

Au/TiO₂ was used as a highly efficient sonocatalyst to produce H₂ from water or aqueous solutions. Au/TiO₂ significantly increased the yields of H• and •OH radicals in the sonolysis of water. Product analysis and isotope evidence indicated that hydrogen molecules derived from methanol/water solutions were formed by three pathways: (1) recombination of two H• atoms from the cleavage of water molecules, (2) H-abstraction from methanol by H• generated by water cleavage, and (3) thermal reforming of methanol. The relative importance of each pathway was assessed by carefully analyzing the hydrogen-isotope composition of the evolved hydrogen gas using a modified gas chromatograph. The source of hydrogen in the H₂ evolved from methanol/water solutions during sonolysis was also addressed. Data showed that, although the addition of methanol in the presence of Au/TiO₂ resulted in a 12-fold increase in the rate of H2 evolution, nearly half of the hydrogen atoms were nevertheless derived from water molecules. Control studies of H₂ formation in the presence of bare TiO₂ and in the absence of a catalyst were also performed. In both cases, the compositions of evolved hydrogen gas were similar to that of the Au/TiO₂ system, although hydrogen evolution was much slower. These findings reveal that Au nanoparticles on the TiO₂ surface effectively catalyze water cleavage and methanol reforming.

39.         Self-Assembly and Structure of Directly Imaged Inorganic-Anion Monolayers on a Gold Nanoparticle

Wang, Yifeng; Neyman, Alevtina; Arkhangelsky, Elizabeth; Gitis, Vitaly; Meshi, Louisa; Weinstock, Ira A.

Journal of the American Chemical Society (2009), 131(47), 17412-17422. https://pubs.acs.org/doi/10.1021/ja907815d

 Cryogenic trapping was used to obtain the 1st TEM images of self-assembled monolayers of inorg. anions on a gold nanoparticle.  This unique structural information makes it possible to study the formation of a protecting-ligand shell at an unprecedented level of detail. The protecting ligands are polyoxometalates (POMs; α-Xⁿ⁺W₁₂O₄₀(^8-n)−, Xⁿ⁺ = Al³⁺ and “2H⁺”, and α-Xⁿ⁺W₁₁O₃₉^(12-n)−, Xⁿ⁺ = P⁵⁺, Si⁴⁺, and Al³⁺ )with large negative charges for association with the gold surface and W atoms (Z = 74) for TEM imaging. The POM-anion shells were obtained by ligand exchange from citrate-protected 13.8 nm gold nanoparticles. Replacement of the organic (citrate) by inorganic (tungsten-oxide) ligand shells results in substantial changes in the surface plasmon reso_nance (SPR). By correlating cryo-TEM images with changes in the SPR, degrees of surface coverage were reliably quantified by UV−visible spectroscopy. Then, the kinetics and thermodynamics of ligand-shell formation were investigated by systematically varying POM structure and charge. Rates of POM association with the gold surface (“nucleation”) are inhibited by the electric-potential barrier of the citrate-stabilized particles, while binding affinities increase linearly with the charges (from 5- to 9-) of structurally different POM anions, suggesting that no single orientation (“lattice matching”) is required for monolayer self-assembly. Time-dependent cryo-TEM images reveal that monolayer growth occurs via “islands”, a mechanism that points to cation-mediated attraction between bound POMs.

40.         Enhanced Sonocatalytic Degradation of Azo Dyes by Au/TiO₂

Wang, Yifeng; Zhao, Dan; Ma, Wanhong; Chen, Chuncheng; Zhao, Jincai

Environmental Science & Technology (2008), 42(16), 6173-6178. https://pubs.acs.org/doi/10.1021/es800168k

Au-loaded TiO₂ (Au/TiO₂) is, for the first time, reported as a sonocatalyst.It was found that the catalyst Au/TiO₂, with a low Au loading 0.5 wt % and under common and commercial frequency (40 kHz) ultrasonic irradiation, greatly accelerated both the discoloration and total organic carbon (TOC) removal of azo dyes such as orange II (Org II), ethyl orange (EO), and acid red G (ARG), as compared to bare TiO₂ and nano-Au catalyst. About 80% TOC removal was achieved after complete discoloration of 2.5 × 10⁻⁴ M Org II. H₂O₂ and H₂ formation as well as their accumulation was greatly enhanced due to Au loading on TiO₂. Both oxidative and reductive degradation intermediates have been detected, and thus the mechanism involves both enhanced oxidation and enhanced reduction via the accelerated formation of active ·OH and ·H radicals due to Au loading on TiO₂, which is supported by electron spin resonance (EPR) and other evidence. The study provides an admirable way to raise the efficiency of sonication and to treat azo dye-containing wastewaters with sonocatalytic processes.

41.         Surface Modification of TiO₂ by Phosphate: Effect on Photocatalytic Activity and Mechanism Implication

Zhao, Dan; Chen, Chuncheng; Wang, Yifeng; Ji, Hongwei; Ma, Wanhong; Zang, Ling; Zhao, Jincai

Journal of Physical Chemistry C (2008), 112(15), 5993-6001.https://pubs.acs.org/doi/10.1021/jp712049c

Phosphate modified TiO₂ photocatalysts were prepd. by phosphoric acid treatment before or after TiO₂ crystn.  Substrates with different structures were chosen to explore the photocatalytic activity of as-modified TiO₂ under UV irradn.  It was found that the effect of phosphate modification is definitely attributed to the surface-bound phosphate anion, and the modification by phosphate can affect both the rates and pathways of photocatalytic reactions, which are of great dependence on the structures and properties of substrates.

42.         Enhanced Photocatalytic Degradation of Dye Pollutants under Visible Irradiation on Al(III)-Modified TiO2: Structure, Interaction, and Interfacial Electron Transfer

Zhao, Dan; Chen, Chuncheng; Wang, Yifeng; Ma, Wanhong; Zhao, Jincai; Rajh, Tijana; Zang, Ling

Environmental Science & Technology (2008), 42(1), 308-314.https://pubs.acs.org/doi/10.1021/es071770e

Aluminum(III)-modified TiO₂ was prepared by sol–gel process via a sudden gelating method. The structure of the modified material and the local environment of aluminum were investigated using X-ray diffraction, HRTEM, XPS, ²⁷Al MAS NMR, and ξ-potential measurements.

43.    Fe³⁺/Fe²⁺ cycling promoted by Ta₃N₅ under visible irradiation in Fenton degradation of organic pollutants

Wang, Yifeng; Ma, Wanhong; Chen, Chuncheng; Hu, Xuefeng; Zhao, Jincai; Yu, Jimmy C.

Applied Catalysis, B: Environmental (2007), 75(3-4), 256-263.

ttps://www.sciencedirect.com/search/advanced?qs=43.%09Fe3%2B%2FFe2%2B%20cycling%20prom

Ta₃N₅ was synthesized by nitridation of Ta₂O₅ under NH₃ flow at 700°.  The catalyst was pure Ta₃N₅ according to X-ray diffraction (XRD), and was about 5 nm in size with a BET sp. surface area 52.8 m²/g.  When Ta₃N₅ was added to Fe³⁺/H₂O₂ soln. (known as Fenton-like system), most F^e3+ were adsorbed on the Ta₃N₅ surface and could not react with H2O2 in the dark, which is different from the general Fenton reaction.