Publications by authors named "Jia Hong Pan"

24 Publications

  • Page 1 of 1

Solid-state self-template synthesis of Ta-doped LiZnTiO spheres for efficient and durable lithium storage.

iScience 2021 Sep 18;24(9):102991. Epub 2021 Aug 18.

MOE Key Laboratory of Resources and Environmental Systems Optimization, College of Environmental Science and Engineering, North China Electric Power University, Beijing 102206, China.

Ta-doped LiZnTiO (LZTO) spheres (LiZnTi Ta O; where is the synthetic chemical input,  = 0, 0.03, 0.05, 0.07) are synthesized via solid-state reaction using mesoporous TiO spheres as the self-template. The majority of Ta ions are uniformly doped into crystal lattices of LZTO through the Ti↔Ta substitution, and the rest forms the piezoelectric LiTaO secondary phase on the surface, as confirmed by X-ray diffraction refinement, Raman spectroscopy, density functional theory, and electron microscopy. Electrochemical impedance spectroscopy demonstrates that the Ta doping creates rapid electronic transportation channels for high Li ion diffusion kinetics; however, the LiTaO surface coating is beneficial to improve the electronic conductivity. At the optimal  = 0.05, LiZnTi Ta O spheres exhibit a reversible capacity of 90.2 mAhg after 2000 cycles with a high coulombic efficiency of ≈100% at 5.0 A/g, thus enabling a promising anode material for lithium-ion batteries with high power and energy densities.
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http://dx.doi.org/10.1016/j.isci.2021.102991DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8405915PMC
September 2021

Photocatalysis for environmental remediation - From laboratories to industry and beyond.

Chemosphere 2021 Jul 28;286(Pt 2):131704. Epub 2021 Jul 28.

Department of Chemical Engineering, Centre of Separation Science and Technology, Universiti Malaya, Kuala Lumpur, 50603, Malaysia; School of Chemical Engineering, The University of New South Wales, Sydney, 2052, Australia. Electronic address:

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http://dx.doi.org/10.1016/j.chemosphere.2021.131704DOI Listing
July 2021

Controllable synthesis and self-template phase transition of hydrous TiO colloidal spheres for photo/electrochemical applications.

Adv Colloid Interface Sci 2021 Sep 21;295:102493. Epub 2021 Jul 21.

MOE Key Laboratory of Resources and Environmental Systems Optimization, College of Environmental Science and Engineering, North China Electric Power University, Beijing 102206, China. Electronic address:

Hydrous TiO colloidal spheres (HTCS) derived from the direct precipitation of titanium alkoxides have attracted continuous interests since 1982. Entering the 21st century, rapid progress in the development of structure-directing agents (SDAs) have enabled reproducible and size-controllable synthesis of highly uniform HTCS with diameters in the nano- to micro-meter range. The availability of various HTCS provides versatile self-templating platforms for the targeted synthesis of nanoporous TiO and titanate spheres with tunable composition, crystallographic phases, and internal structures for a variety of advanced photo/electrochemical applications. This review provides a historical overview for the evolution of HTCS, along with an insightful discussion for the formation mechanism of self-assembly of HTCS during the sol-gel process. Key synthetic parameters including SDA, solvent, reaction temperature and water dosage are discussed for the size and morphology control of HTCS with predictable textural properties. Then, we describe the synthetic strategies of nanoporous TiO and titanate spheres using various HTCS as self-templates. Here, the focus lies on the interactions between TiO nanobuilding blocks with precursors or media at the solid/liquid and solid/solid interfaces, the concurrent phase transitions, and the microstructural and morphological evolutions. Selective formation of crystal phase and internal structures (e.g., solid, hollow, core-shell, yolk-shell) are discussed by manipulating the crystallization kinetics. To further elucidate the composition-structure-property-performance relationship for the resulting nanoporous TiO and titanate spheres, their applications in photo(electro)catalysis, mesoscopic solar cells, and lithium-ion batteries are scrutinized. Finally, we share opinions on key challenges and perspectives for the future controllable preparation, formation mechanisms, and applications of HTCS and their crystalline derivatives.
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http://dx.doi.org/10.1016/j.cis.2021.102493DOI Listing
September 2021

Novel green synthesis of S-doped TiO nanoparticles using Malva parviflora plant extract and their photocatalytic, antimicrobial and antioxidant activities under sunlight illumination.

Chemosphere 2021 May 31;271:129524. Epub 2020 Dec 31.

MOE Key Laboratory of Resources and Environmental Systems Optimization, College of Environmental Science and Engineering, North China Electric Power University, Beijing, 102206, China. Electronic address:

Visible-light-responsible S-doped TiO(GST) nanoparticles (NPs) are synthesized via sol-gel process, and an aqueous extract of Malva parviflora (MP) plant is used as the green and versatile medium with excellent reducing and capping properties to facilitate the S-doping and crystal growth of anatase. Compared with the counterpart (CST) derived from the conventional organic solvent. GST show a smaller average particle size (20.3 vs. 29.5 nm) with a larger surface area (135 vs 95 m/g), together with the more significant red shift to longer wavelength in the visible light region. XPS analysis shows Ti cations are substituted by S ions into the lattice structure of TiO for both samples. The photodynamics of CST and GST catalysts are examined by electron paramagnetic resonance (EPR) spectroscopy, which shows the surface Ti sites can be oxidized easily by the surface adsorbed O molecules, forming O radicals. Their photocatalytic activities (PCA) are evaluated by degrading methyl orange (MO) dye under the visible light irradiation. GST exhibit higher PCA in MO bleaching and chemical oxygen demand (COD) reduction. In addition, antimicrobial and antioxidant assays of CST and GST NPs also show that the irradiated NPs samples show higher antibacterial activities. GST NPs have a higher antibacterial activity than CST NPs against all tested bacteria and the minimum inhibitory concentration (MIC) is optimized to 25 μg/mL. The in-vitro antioxidant activity evaluated by the radical cation de-colorization test using 1,1-diphenyl-2-picrylhydrazyl (DPPH) further demonstrates that GST NPs give a better antioxidant activity.
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http://dx.doi.org/10.1016/j.chemosphere.2020.129524DOI Listing
May 2021

Mesoporous WO/TiO spheres with tailored surface properties for concurrent solar photocatalysis and membrane filtration.

Chemosphere 2021 Jan 14;263:128344. Epub 2020 Sep 14.

MOE Key Laboratory of Regional Energy and Environmental Systems Optimization, College of Environmental Science and Engineering, North China Electric Power University, Beijing, 102206, China; Beijing Key Laboratory of Novel Thin Film Solar Cells, North China Electric Power University, Beijing, 102206, China. Electronic address:

The strategical integration of membrane water filtration with semiconductor photocatalysis presents a frontier in deep purification with a self-cleaning capability. However, the membrane fouling caused by the cake layer of the reclaimed TiO nanoparticles is a key obstacle. Herein, mesoporous WO/TiO spheres (∼450 nm in diameter) consisting of numerous self-assembled WO-decoated anatase TiO nanocrystallites are successfully prepared via a facile wet-chemistry route. The decoration of monolayered WO significantly affects the surface, photocatalytic, and optical properties of original mesoporous TiO spheres. XRD and Raman analyses show the presence of monolayered WO suppresses the crystal growth of TiO during the calcination process, significantly improves the surface acidity, and causes an obvious red shift in absorption edge. These favorable textural properties, coupling the enhanced interfacial charge carrier separation, render mesoporous WO/TiO spheres with a superior photocatalytic activity in degradation of methylene blue under UV, visible, and solar light irradiations. The optimal molar ratio of W/Ti is examined to 6%. The synthesized mesoporous WO/TiO spheres also show much higher flux during membrane filtration in both dead-end and cross-flow modes, suggesting a promising photocatalyst for concurrent membrane filtration and solar photocatalysis.
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http://dx.doi.org/10.1016/j.chemosphere.2020.128344DOI Listing
January 2021

Innovative utilization of molecular imprinting technology for selective adsorption and (photo)catalytic eradication of organic pollutants.

Chemosphere 2021 Feb 23;265:129077. Epub 2020 Nov 23.

Institute of Materials Research and Engineering, A∗STAR, 2 Fusionopolis Way, Singapore, 138634, Singapore. Electronic address:

The rapid development of industrialization and urbanization results in a numerous production of various organic chemicals to meet the increasing demand in high-quality life. During the synthesis and utilization of these chemical products, their residues unavoidably emerged in environments to severely threaten human's health. It is thus urgent to exploit effective technology for readily removing the organic pollutants with high selectivity and good reusability. As one of the most promising approaches, molecular imprinting technology (MIT) employs a chemically synthetic route to construct artificial recognition sites in highly-crosslinked matrix with complementary cavity and functional groups to target species, which have been attracting more and more interest for environmental remediation, such as the selective adsorption/separation and improved catalytic degradation of pollutants. In this review, MIT is first introduced briefly to understand their preparing process, recognition mechanism and common imprinted systems. Then, their specific binding affinities are demonstrated for selectively adsorbing and removing target molecules with a large capacity. Furthermore, the innovative utilization of MIT in catalytic eradication of pollutants is comprehensively overviewed to emphasize their enhanced efficiency and improved performances, which are classified by the used catalytically-active nanocrystals and imprinted systems. After summarizing recent advances in these fields, some limitations are discussed and possible suggestions are given to guide the future exploitation on MIT for environmental protection.
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http://dx.doi.org/10.1016/j.chemosphere.2020.129077DOI Listing
February 2021

Controllable Synthesis and Crystallization of Nanoporous TiO Deep-Submicrospheres and Nanospheres via an Organic Acid-Mediated Sol-Gel Process.

Langmuir 2020 Jul 18;36(26):7447-7455. Epub 2020 Jun 18.

MOE Key Laboratory of Resources and Environmental Systems Optimization, College of Environmental Science and Engineering, North China Electric Power University, Beijing 102206, China.

Although considerable progress has been achieved in the preparation of uniform hydrous TiO spheres (HTS) through the sol-gel process, there is plenty of room left in tailoring the size and morphology of HTS on the deep-submicron scale or even nanoscale since the diameters of the so far reported HTS are mostly on the (sub)micron scale (0.3-1.2 μm). Here, we develop a novel titanium tetraisopropoxide (TTIP)-organic acid (OA)-acetonitrile (ACN)-methanol (MeOH)-HO system, which facilitates the control of nanoporous HTS to the range of 50-300 nm. The synthetic parameters including OA, (co-)solvent, concentration of precursor, and reaction temperature are comprehensively optimized, aiming at reproducible preparation and precise size control. Among the various OAs, -valeric acid presents the best capability in controlling the spherical morphology and size uniformity. The synthesized amorphous HTS containing numerous micropores and mesopores show excellent hydrothermal stability and offer suitable self-template for the subsequent synthesis of mesoporous anatase TiO spheres (MAT) with a large surface area of 99.1 m/g. The obtained TiO deep-submicrospheres and nanospheres with tunable sizes show great potential in various research fields.
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http://dx.doi.org/10.1021/acs.langmuir.0c01008DOI Listing
July 2020

In situ synthesis of N-CoMePc/rGO nanocomposite with enhanced photocatalytic activity and stability in Cr(VI) reduction.

J Chem Phys 2020 Apr;152(15):154702

School of Chemistry and Chemical Engineering, Harbin Institute of Technology, Harbin 150001, China.

Graphene-based composites are widely used in the photocatalytic treatment of heavy-metal ions or dyes. In this study, we developed a facile in situ precipitation method for preparing a non-peripheral octamethyl-substituted cobalt(II)phthalocyanine (N-CoMePc)/reduced graphene oxide (rGO) nanocomposite as an efficient photocatalyst. The physical and chemical properties of the nanocomposite were investigated by scanning electron microscopy, transmission electron microscopy, x-ray diffraction, and ultraviolet-visible, ultraviolet photoelectron, Fourier-transform infrared, Raman, and x-ray photoelectron spectroscopies. The results showed that the N-CoMePc nanoparticles were immobilized on rGO nanosheets via π-π stacking interactions. The photocatalytic activity of the nanocomposite in the reduction of hexavalent chromium [Cr(VI), 10 mg/l] under visible-light irradiation was investigated. The Cr(VI) removal ratio reached 99.5% with a high photocatalytic rate of 0.0359 min, which is ten times faster than that achieved with pristine N-CoMePc. The high removal efficiency is attributed to the following: (1) the number of active sites provided by nanodot-like N-CoMePc is larger than that provided by bulk Pc, which can increase the production of photogenerated carriers, and (2) enhanced charge carrier separation resulting from intimate contact between N-CoMePc nanodots and GO nanosheets. The N-CoMePc/rGO also showed excellent stability and reusability. The Cr(VI) removal efficiency was 93.2% after eight photocatalytic test cycles.
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http://dx.doi.org/10.1063/5.0005720DOI Listing
April 2020

Designing function-oriented artificial nanomaterials and membranes via electrospinning and electrospraying techniques.

Mater Sci Eng C Mater Biol Appl 2018 Nov 12;92:1075-1091. Epub 2017 Nov 12.

Beijing Key Laboratory of Energy Safety and Clean Utilization, School of Renewable Energy, North China Electric Power University, Beijing 102206, China. Electronic address:

The sister technologies, electrospinning and electrospraying provide a facile and universal synthesis method for the continuous preparation of nanostructured materials. Through adjusting the synthesis parameters, rich electrospun and electrosprayed nanomaterials, scaffolds, membranes with tunable composition (inorganic, polymeric, hybrid, etc.), shape (sphere, films, scaffold, etc.), morphology and inner structure (solid, hollow, core-shell, co-axial, etc.) can be selectively elaborated. This review provides an overview of the design of functional nanostructured materials, porous scaffolds and membranes by electrospinning and electrospraying techniques. Key experimental parameters and synthesis strategy are emphasized to reveal the synthesis-component-structure-property relationship and eventually realize the targeted functions through predictable synthesis. Potential applications in tissue engineering, medicine, membrane filtration and lithium battery are highlighted.
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http://dx.doi.org/10.1016/j.msec.2017.11.007DOI Listing
November 2018

Vitamin E deficiency depressed fish growth, disease resistance, and the immunity and structural integrity of immune organs in grass carp (Ctenopharyngodon idella): Referring to NF-κB, TOR and Nrf2 signaling.

Fish Shellfish Immunol 2017 Jan 22;60:219-236. Epub 2016 Nov 22.

Animal Nutrition Institute, Sichuan Agricultural University, Chengdu 611130, China; Fish Nutrition and Safety Production University Key Laboratory of Sichuan Province, Sichuan Agricultural University, Chengdu 611130, China; Key Laboratory for Animal Disease-Resistance Nutrition of China Ministry of Education, Sichuan Agricultural University, Chengdu 611130, China. Electronic address:

This study investigated the effects of dietary vitamin E on growth, disease resistance and the immunity and structural integrity of head kidney, spleen and skin in grass carp (Ctenopharyngodon idella). The fish were fed six diets containing graded levels of vitamin E (0, 45, 90, 135, 180 and 225 mg/kg diet) for 10 weeks. Subsequently, a challenge test was conducted by injection of Aeromonas hydrophila. The results showed that compared with optimal vitamin E supplementation, vitamin E deficiency caused depressed growth, poor survival rates and increased skin lesion morbidity in grass carp. Meanwhile, vitamin E deficiency decreased lysozyme and acid phosphatase activities, complement component 3 and complement component 4 contents in the head kidney, spleen and skin of grass carp (P < 0.05). Moreover, vitamin E deficiency down-regulated antimicrobial peptides (Hepcidin, liver-expressed antimicrobial peptide-2A, -2B, β-defensin), IL-10, TGFβ1, IκBα, TOR and S6K1 mRNA levels (P < 0.05) and up-regulated IL-1β, IL-6, IL-8, IFN-γ2 and TNFα, NF-κB p65, IKKα, IKKβ and 4EBP1 (not in the head kidney) mRNA levels (P < 0.05). In addition, vitamin E deficiency caused oxidative damage, decreased superoxide dismutase (SOD), glutathione peroxidase (GPx), catalase (CAT) and glutathione reductase (GR) activities, and down-regulated the mRNA levels of antioxidant enzymes and signaling molecules Nrf2 (P < 0.05). Vitamin E deficiency also induced apoptosis by up-regulating capase-2, -3, -7, and -8 mRNA levels in the head kidney, spleen and skin of grass carp. In conclusion, this study indicated that dietary vitamin E deficiency depressed fish growth, impaired the immune function and disturbed the structural integrity of the head kidney, spleen and skin in grass carp, but optimal vitamin E supplementation can reverse those negative effects in fish. The optimal vitamin E requirements for young grass carp (266.39-1026.63 g) to achieve optimal growth performance and disease resistance based on the percent weight gain (PWG) and skin lesion morbidity were estimated to be 116.2 and 130.9 mg/kg diet, respectively. Meanwhile, based on immune indicator (LA activity in the head kidney) and antioxidant indicator (protection of spleen against MDA), the optimal vitamin E requirements for young grass carp were estimated to be 123.8 and 136.4 mg/kg diet, respectively.
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http://dx.doi.org/10.1016/j.fsi.2016.11.044DOI Listing
January 2017

Superior Light-Harvesting Heteroleptic Ruthenium(II) Complexes with Electron-Donating Antennas for High Performance Dye-Sensitized Solar Cells.

ACS Appl Mater Interfaces 2016 Aug 22;8(30):19410-7. Epub 2016 Jul 22.

Key Laboratory of Novel Thin Film Solar Cells, Institute of Applied Technology, Hefei Institutes of Physical Science, Chinese Academy of Sciences , Hefei, 230031, P. R. China.

Three heteroleptic polypyridyl ruthenium complexes, RC-41, RC-42, and RC-43, with efficient electron-donating antennas in the ancillary ligands were designed, synthesized, and characterized as sensitizers for dye-sensitized solar cell. All the RC dye sensitizers showed remarkable light-harvesting capacity and broadened absorption range. Significantly, RC-43 obtained the lower energy metal-ligand charge transfer (MLCT) band peaked at 557 nm with a high molar extinction coefficient of 27 400 M(-1) cm(-1). In conjunction with TiO2 photoanode of submicrospheres and iodide-based electrolytes, the DSSCs sensitizing with the RC sensitizers, achieved impressively high short-circuit current density (19.04 mA cm(-2) for RC-41, 19.83 mA cm(-2) for RC-42, and 20.21 mA cm(-2) for RC-43) and power conversion efficiency (10.07% for RC-41, 10.52% for RC-42, and 10.78% for RC-43). The superior performances of RC dye sensitizers were attributed to the enhanced light-harvesting capacity and incident-photon-to-current efficiency (IPCE) caused by the introduction of electron-donating antennas in the ancillary ligands. The interfacial charge recombination/regeneration kinetics and electron lifetime were further evaluated by the electrochemical impedance spectroscopy (EIS) and transient absorption spectroscopy (TAS). These data decisively revealed the dependences on the photovoltaic performance of ruthenium sensitizers incorporating electron-donating antennas.
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http://dx.doi.org/10.1021/acsami.6b04411DOI Listing
August 2016

Significantly Enhanced Separation using ZIF-8 Membranes by Partial Conversion of Calcined Layered Double Hydroxide Precursors.

ChemSusChem 2015 Nov 2;8(21):3582-6. Epub 2015 Oct 2.

Institute of Physical Chemistry and Electrochemistry, Leibniz University Hannover, Callinstr. 22, 30167, Hannover, Germany.

Significantly enhanced H2 /CH4 (ca. 80) selectivity was realized by effective suppression of the framework flexibility of a prepared ZIF-8 membrane. Initially a ZnO buffer layer consisting of 20 nm-sized ZnO-nanoparticle aggregates was fabricated by controlled calcination of a ZnAl-NO3 layered double hydroxide membrane. Owing to its high chemical reactivity, the ZnO buffer layer was partially converted into a well-intergrown ZIF-8 membrane with a certain penetration depth upon solvothermal treatment with ligands. Our method may represent a new concept for the design of advanced MOF membranes with high selectivity.
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http://dx.doi.org/10.1002/cssc.201500977DOI Listing
November 2015

Self-Template Synthesis of Porous Perovskite Titanate Solid and Hollow Submicrospheres for Photocatalytic Oxygen Evolution and Mesoscopic Solar Cells.

ACS Appl Mater Interfaces 2015 Jul 2;7(27):14859-69. Epub 2015 Jul 2.

†Department of Materials Science and Engineering, Faculty of Engineering, NUSNNI-NanoCore, National University of Singapore, 5 Engineering Drive 2, 117576 Singapore.

We describe a general synthesis strategy, which combines sol-gel and hydrothermal processes, for the large-scale synthesis of porous perovskite titanates spheres with tunable particle size and inner structures. Amorphous hydrous TiO2 solid spheres (AHTSS) are first synthesized by a sol-gel method and are then used as precursor and template for the subsequent hydrothermal reaction with alkaline earth metal ions in an alkaline medium. This strategy can be generalized to synthesize porous spheres of various perovskite titanates (i.e., SrTiO3, BaTiO3, and CaTiO3) consisting of single-crystalline nanocubes. By controlling the textural properties (i.e., size, porosity, and structure) of AHTSS, perovskite titanates with tunable size and inner structures are selectively synthesized. The underlying formation mechanism is manifested by XRD and TEM to involve in situ crystallization or Ostwald ripening during the hydrothermal process. The obtained porous SrTiO3 spheres present superior performance in photocatalytic oxygen evolution and CdSe-sensitized mesoscopic solar cells.
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http://dx.doi.org/10.1021/acsami.5b03396DOI Listing
July 2015

Reconstruction of Colloidal Spheres by Targeted Etching: A Generalized Self-Template Route to Porous Amphoteric Metal Oxide Hollow Spheres.

Langmuir 2015 Apr 10;31(15):4566-72. Epub 2015 Apr 10.

Department of Materials Science and Engineering, Faculty of Engineering, NUSNNI-NanoCore, National University of Singapore, Singapore 117576, Singapore.

Despite the significant progress in developing various synthetic strategies for metal oxide hollow spheres (h-MO), the so-far explored materials are mostly chemically inert metal oxides. Very few attempts have been made for amphoteric metal oxides such as Al2O3 and ZnO due to the difficulties in the control of the dissolution and recrystallization process. Herein, a facile self-template route to the synthesis of amphoteric h-MO with tunable size and shell thickness is developed by targeted etching via an acid-base reaction. With the protection of polyvinylpyrrolidone (PVP) on the surface, the interior of metal oxide solid colloidal spheres (c-MOs) that possess radially divergent structures could be selectively etched with acid/alkali as an etchant, forming h-MO of Al2O3 and ZnO. Our results also show that a wide variety of metal oxide colloidal spheres can be potential self-templates for targeted etching, which paves the way for developing a generalized strategy for the synthesis of various metal oxide hollow spheres.
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http://dx.doi.org/10.1021/acs.langmuir.5b00638DOI Listing
April 2015

Remarkably enhanced gas separation by partial self-conversion of a laminated membrane to metal-organic frameworks.

Angew Chem Int Ed Engl 2015 Mar 21;54(10):3028-32. Epub 2015 Jan 21.

Institute of Physical Chemistry and Electrochemistry, Leibniz University Hannover, Callinstr. 22, 30167 Hannover (Germany).

Separation methods based on 2D interlayer galleries are currently gaining widespread attention. The potential of such galleries as high-performance gas-separation membranes is however still rarely explored. Besides, it is well recognized that gas permeance and separation factor are often inversely correlated in membrane-based gas separation. Therefore, breaking this trade-off becomes highly desirable. Here, the gas-separation performance of a 2D laminated membrane was improved by its partial self-conversion to metal-organic frameworks. A ZIF-8-ZnAl-NO3 layered double hydroxide (LDH) composite membrane was thus successfully prepared in one step by partial conversion of the ZnAl-NO3 LDH membrane, ultimately leading to a remarkably enhanced H2 /CH4 separation factor and H2 permeance.
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http://dx.doi.org/10.1002/anie.201411550DOI Listing
March 2015

In situ synthesis of MOF membranes on ZnAl-CO3 LDH buffer layer-modified substrates.

J Am Chem Soc 2014 Oct 3;136(41):14353-6. Epub 2014 Oct 3.

Department of Physical Chemistry and Electrochemistry, Leibniz University Hannover , Callinstr. 22, 30167, Hannover, Germany.

We develop here a urea hydrolysis method to in situ prepare asymmetric ZnAl-CO3 layered double hydroxide (LDH) buffer layers with various stable equilibrium morphology on porous Al2O3 substrates. In particular it is found that well-intergrown ZIF-8 membranes can be directly synthesized on the ZnAl-CO3 LDH buffer layer-modified substrates, owing to the specific metal-imidazole interaction between ZnAl-CO3 LDHs and ZIF-8. Other Zn-based MOF membranes, like ZIF-7 and ZIF-90, can also be synthesized with this method. Our finding demonstrates that LDH buffer layer represents a new concept for substrate modification.
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http://dx.doi.org/10.1021/ja507408sDOI Listing
October 2014

Scalable synthesis of urchin- and flowerlike hierarchical NiO microspheres and their electrochemical property for lithium storage.

ACS Appl Mater Interfaces 2013 Jul 20;5(13):6292-9. Epub 2013 Jun 20.

Department of Materials Science and Engineering, Faculty of Engineering, NUSNNI-NanoCore, National University of Singapore, Singapore.

A nickel salt-urea-H2O ternary system has been developed for the large-scale synthesis of hierarchical α-Ni(OH)2 microspheres, the solid precursor for the subsequent topotactic transition to NiO upon calcination. In this facile synthetic system, hierarchical structure is self-assembled under the cooperative direction of urea and anions in nickel salts. Thus, simply tuning the Ni salts leads to the selective construction of urchin and flowerlike hierarchical α-Ni(OH)2 and NiO microspheres consisting of radial 1D nanowires and 2D nanoplates, respectively. The obtained NiO microspheres possessing accessible nanopores, excellent structural stability and large surface area up to 130 m(2)/g show promising electrochemical performance in anodic lithium storage for lithium-ion battery.
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http://dx.doi.org/10.1021/am401330gDOI Listing
July 2013

A hierarchically assembled mesoporous ZnO hemisphere array and hollow microspheres for photocatalytic membrane water filtration.

Phys Chem Chem Phys 2012 May 25;14(20):7481-9. Epub 2012 Apr 25.

School of Civil and Environmental Engineering, Nanyang Technological University, Singapore 639798, Singapore.

A mesoporous ZnO hemisphere array has been prepared via a topotactic transition of Zn(4)(OH)(6)CO(3)·H(2)O (ZCHH) by chemical bath deposition. Each hemisphere is comprised of a radially oriented nanoflake shell grown on the hemispherical interior. Reaction time-dependent SEM analysis shows that the morphological formation of ZCHH involves a deposition-growth-secondary growth-redeposition procedure. Upon calcination, ZCHH readily decomposes to nanocrystalline wurtzite-phase ZnO without significant change in morphology, and the release of CO(2) and H(2)O from ZCHH creates an additional mesoporous structure in both hemispherical interior and nanoflake shell. A similar process but without using a substrate has been developed for synthesis of mesoporous ZnO hollow microspheres in powder form. Both the elaborated superstructured photocatalysts consisting of mesoporous nanoflakes have been demonstrated to exhibit excellent performances in the photocatalytic membrane filtration.
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http://dx.doi.org/10.1039/c2cp40997fDOI Listing
May 2012

Hierarchical N-doped TiO2 hollow microspheres consisting of nanothorns with exposed anatase {101} facets.

Chem Commun (Camb) 2011 Jun 20;47(24):6942-4. Epub 2011 May 20.

Department of Chemical and Biomolecular Engineering, Faculty of Engineering, National University of Singapore, 4 Engineering Drive 4, Singapore 117576, Singapore.

A green solvothermal synthesis approach employing water as a hollowing controller and diethylenetriamine as both crystal growth stabilizer and N dopant source to the preparation of hierarchical N-doped TiO(2) hollow microspheres comprised of nanothorns with exposed anatase {101} facets is established. The superstructured TiO(2) shows excellent photocatalytic activities in degrading dyes under visible light irradiation.
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http://dx.doi.org/10.1039/c1cc11796cDOI Listing
June 2011

Effect of calcination temperature on the textural properties and photocatalytic activities of highly ordered cubic mesoporous WO3/TiO2 films.

J Nanosci Nanotechnol 2010 Jul;10(7):4747-51

School of Civil and Environmental Engineering, Nanyang Technological University, 639798, Singapore.

Highly organized cubic mesoporous WO3/TiO2 films were successfully prepared by evaporation-induced self-assembly (EISA) process, employing triblock copolymer as template. The characterization results by XRD, SEM, TEM, UV-Vis. spectrophotometry, and nitrogen adsorption-desorption isotherms reveal that the mesoporous films are made up of well-defined 3-D cubic (lm3m space group) mesoporous structure and nanocrystalline anatase frameworks with high surface area, uniform pore sizes and excellent optical transparency. Photocatalytic properties of the mesoporous WO3/TiO2 films in decomposing gaseous 2-propanol to CO2 were analyzed as a function of calcinations temperature. The highest photocatalytic activity was obtained for the films calcined at 450 degrees C, which possess an appropriate crystallinity and relevant ordering of mesoporous structure. It was found that that long-range ordering of mesopores is one of the important factors in determining the photocatalytic degradation of gaseous organics.
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http://dx.doi.org/10.1166/jnn.2010.1672DOI Listing
July 2010

Transformation of bromine species in TiO2 photocatalytic system.

Environ Sci Technol 2010 Jan;44(1):439-44

School of Civil and Environmental Engineering, Nanyang Technological University, 639798 Singapore.

Bromine species have six oxidation states from Br(-) to BrO(3)(-), and their transformation between each oxidation state is complex and has been a common debate topic in photocatalytic systems where oxidants (h(+) and OH.) and reducers (e(-)) coexist. In this study, the lowest oxidation state (Br(-)) and highest oxidation state (BrO(3)(-)) were used as the starting compounds in a photocatalytic reaction to investigate the transformation of bromine species. The experimental results showed that oxidation of Br(-) to BrO(3)(-) by OH. and reduction of BrO(3)(-) to Br(-) by e(-) were concurrent. However, due to a higher reaction rate for reduction of BrO(3)(-) under a pH range of 3-11, oxidation of Br(-) was totally offset and hence, only the reduction of BrO(3)(-) was observed with hydrobromous acid and hydrobromite formed as intermediates. Apart from e(-), H(2)O(2), to a certain extent, was involved in the photocatalytic reduction of BrO(3)(-). A low concentration of organic matter (3 mg/L) reacted with hydroxyl radicals to inhibit combination of holes and electrons, hence promoting photocatalytic reduction of BrO(3)(-). It is important to note that pH had an influence on the transformation of bromine species, because it affects adsorption of reactants on the photocatalyst and controls the amount of aqueous H(+) and OH(-) ions present. Photocatalytic oxidation of Br(-) became dominant under a strong acidic condition (pH 1.5) while both photocatalytic oxidation and reduction were inhibited under a strong basic condition (pH 13.5).
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http://dx.doi.org/10.1021/es902592wDOI Listing
January 2010

Combination of one-dimensional TiO(2) nanowire photocatalytic oxidation with microfiltration for water treatment.

Water Res 2009 Mar 25;43(5):1179-86. Epub 2008 Dec 25.

School of Civil and Environmental Engineering, Nanyang Technological University, 639798 Singapore, Singapore.

This paper proposed the fabrication of two different diameter one-dimensional TiO2 nanowires, 10 nm TNW10 and 20-100 nm TNW20, via hydrothermal process using different alkaline sources. TNW10 and TNW20 were used as photocatalysts for the degradation of humic acid (HA), the major natural organic matters (NOMs) in surface and ground water, followed by microfiltration. The evaluation of photocatalytic activities of them showed that TNW10 was superior to the commercial P25 TiO2 while TNW20 was as good as P25. The membrane filtration verified that the two types of nanowires could be completely reclaimed. The membrane fouling caused by TNW10 and TNW20 was much less than that of P25 due to more porous cake and less pore plugging. No apparent decrease on their photocatalytic activity was observed in repeated reuse experiments. These one-dimensional TiO2 nanowires would provide a new route for the combination of photocatalytic oxidation and membrane filtration for water treatment.
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http://dx.doi.org/10.1016/j.watres.2008.12.021DOI Listing
March 2009

Formation of efficient dye-sensitized solar cells by introducing an interfacial layer of long-range ordered mesoporous TiO2 thin film.

Langmuir 2008 Nov 16;24(22):13225-30. Epub 2008 Oct 16.

Nano Materials and Devices Laboratory, Department of Chemistry, Inha University, Incheon 402-751, Korea.

Long-range ordered cubic mesoporous TiO 2 films with 300 nm thickness were fabricated on fluorine-doped tin oxide (FTO) substrate by evaporation-induced self-assembly (EISA) process using F127 as a structure-directing agent. The prepared mesoporous TiO 2 film (Meso-TiO 2) was applied as an interfacial layer between the nanocrystalline TiO 2 film (NC-TiO 2) and the FTO electrode in the dye-sensitized solar cell (DSSC). The introduction of Meso-TiO 2 increased J sc from 12.3 to 14.5 mA/cm (2), and V oc by 55 mV, whereas there was no appreciable change in the fill factor (FF). As a result, the photovoltaic conversion efficiency ( eta) was improved by 30.0% from 5.77% to 7.48%. Notably, introduction of Meso-TiO 2 increased the transmittance of visible light through the FTO glass by 23% as a result of its excellent antireflective role. Thus the increased transmittance was a key factor in enhancing the photovoltaic conversion efficiency. In addition, the presence of interfacial Meso-TiO 2 provided excellent adhesion between the FTO and main TiO 2 layer, and suppressed the back-transport reaction by blocking direct contact between the electrolyte and FTO electrode.
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http://dx.doi.org/10.1021/la802340gDOI Listing
November 2008

Self-etching reconstruction of hierarchically mesoporous F-TiO2 hollow microspherical photocatalyst for concurrent membrane water purifications.

J Am Chem Soc 2008 Aug 5;130(34):11256-7. Epub 2008 Aug 5.

School of Civil and Environmental Engineering, Nanyang Technological University, Singapore 639798.

We report a large-scale self-etching approach for the synthesis of monodispersed mesoporous F-TiO2 hollow microspheres. The self-etching derived from HF was elucidated by the morphology, chemical composition, and crystal size evolutions from solid to hollow microspheres with the increase in the concentration of H2SO4. The resulting TiO2 hollow microspheres exhibited ease for the concurrent membrane filtration and photocatalysis, providing high potential for engineering application in advanced water treatment, for not only increasing water production but also improving water quality.
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http://dx.doi.org/10.1021/ja803582mDOI Listing
August 2008
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