Co-reporter:Yongqiang Cao;Yongmei Chen;Yaan Cao
The Journal of Physical Chemistry C March 4, 2010 Volume 114(Issue 8) pp:3627-3633
Publication Date(Web):Publication Date (Web): February 8, 2010
DOI:10.1021/jp100786x
A new type of composite film (heterostructure) with optoelectronic properties have been prepared by coupling Sn-doped rutile TiO2 (R-TiO2−Sn) and N-doped anatase TiO2 (A-TiO2−N) with use of a sol−gel method. Under visible and UV light irradiation, it exhibits a higher photocatalytic activity than both R-TiO2−Sn and A-TiO2−N films due to the formation of a heterojunction at the interface, as well as the increase of total amount of photogenerated charge carriers and introduction of doping states. If R-TiO2−Sn is the outmost layer, moreover, the composite film shows a much higher photodegradation capability of HCHO than that when A-TiO2−N is the outmost layer. Our results offer a paradigm for developing optoelectronic functional materials that can be used in many fields, such as solar cells, photocatalysis, and photosynthesis.
Co-reporter:Jiarui Jin, Tao He
Applied Surface Science 2017 Volume 394() pp:364-370
Publication Date(Web):1 February 2017
DOI:10.1016/j.apsusc.2016.10.118
Highlights
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Bi2S3 nanoribbons are successfully synthesized by the solvothermal method.
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The length-to-width ratio of Bi2S3 nanoribbons can be readily tuned.
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CO2 is photoreduced to CH3OH over Bi2S3 nanoribbons under visible-light irradiation.
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Bi2S3 nanoribbons exhibit relatively high activity for CO2 photoreduction.
Co-reporter:Yanjie Wang;Saher Hamid;Xin Zhang;Naeem Akhtar;Xuehua Zhang
New Journal of Chemistry (1998-Present) 2017 vol. 41(Issue 4) pp:1591-1597
Publication Date(Web):2017/02/13
DOI:10.1039/C6NJ03338E
An electrochemiluminescence (ECL) sensor based on a poly(luminol–benzidine sulfate) electrode has been fabricated for dopamine detection. Different concentrations of luminol and benzidine sulfate with a constant ratio of 2 : 3 are used as precursors to synthesize poly(luminol–benzidine sulfate) by cyclic voltammetry. Tyramine oxidase is immobilized onto the surface of the resultant poly(luminol–benzidine sulfate) film so as to oxidize dopamine and produce H2O2 for ECL detection. The ECL signal increases linearly with the concentration of dopamine in the range of 1–20 nM with the optimized electrode. The obtained biosensor exhibits a detection limit of 0.5 nM. It shows almost no response to the excess amount of interferents like ascorbic acid and uric acid with a 100-fold concentration of dopamine. Therefore, this work may provide a promising sensor with high sensitivity and selectivity for dopamine detection.
Co-reporter:Sivakumar Palanisamy;Xuehua Zhang
Science China Chemistry 2016 Volume 59( Issue 4) pp:387-393
Publication Date(Web):2016 April
DOI:10.1007/s11426-015-5500-0
Dopamine (DA) plays an important role in health and peripheral nervous systems. Colorimetric detection of DA has the advantage of color change and simplicity in operation and instrumentation. Herein, we report a highly sensitive and selective colorimetric detection of DA by using two specific ligands modified Ag nanoparticles, where the DA molecules can make dual recognition with high specificity. The colloidal suspension of modified Ag nanoparticles was agglomerated after interacting with DA, while the color of Ag nanoparticles suspension changed from yellow to brown, arising from the interparticle plasmon coupling during the aggregation of Ag nanoparticles. The modified Ag nanoparticles suspension and agglomeration were confirmed by transmission electron microscope images. The optical properties behind the color change were thoroughly investigated by using UV-Vis and Raman techniques. The changes in pH, zeta potential, particle size and surface charge density by adding DA were also determined by using dynamic light scattering measurements. The detection limits of modified Ag probes for DA was calculated to be 6.13×10-6 mol L-1 (S/N=2.04) and the correlation co-efficient was determined to be 0.9878. Because of the simplicity in operation and instrumentation of the colorimetric method, this work may afford a feasible, fast approach for detecting and monitoring the DA levels in physiological and pathological systems.
Co-reporter:Ling-ju Guo;Yan-jie Wang
The Chemical Record 2016 Volume 16( Issue 4) pp:1918-1933
Publication Date(Web):
DOI:10.1002/tcr.201600008
Abstract
Photoreduction of CO2, which utilizes solar energy to convert CO2 into hydrocarbons, can be an effective means to overcome the increasing energy crisis and mitigate the rising emissions of greenhouse gas. This article covers recent advances in the CO2 photoreduction over heterostructure-based photocatalysts. The fundamentals of CO2 photoreduction and classification of the heterostructured photocatalysts are discussed first, followed by the latest work on the CO2 photoreduction over heterostructured photocatalysts in terms of the classification of the coupling semiconductors. Finally, a brief summary and a perspective on the challenges in this area are presented.
Co-reporter:Sivakumar Palanisamy, Xuehua Zhang and Tao He
Journal of Materials Chemistry A 2015 vol. 3(Issue 29) pp:6019-6025
Publication Date(Web):22 Jun 2015
DOI:10.1039/C5TB00495K
Colorimetric detection of dopamine has the advantage of simplicity in operation and instrumentation. Herein, a highly sensitive and selective colorimetric biosensor with fast response has been developed by using 4′-aminobenzo-18-crown-6 (ABCE) and 4-mercaptophenyl boronic acid (MPBA) modified Au nanoparticles. The modified probe shows an excellent detection limit of 6.0 nM of dopamine at a S/N of 2.01 and about 46 nM at a S/N of 3 within microseconds response. It exhibits excellent detection selectivity even in 1000-fold excess of many different interferents like metal ions, uric acid and ascorbic acid. All these may make it fulfill the requirements for in vivo analysis.
Co-reporter:Sana Ijaz, Muhammad Fahad Ehsan, Muhammad Naeem Ashiq and Tao He
Catalysis Science & Technology 2015 vol. 5(Issue 12) pp:5208-5215
Publication Date(Web):11 Aug 2015
DOI:10.1039/C5CY00955C
Due to shortage of fossil fuels and rapid growth of energy demand, exploration of new energy resources becomes essential. Moreover, the CO2 level is increasing day by day, which has caused global warming as well as environmental pollution. Designing a suitable photocatalyst that can solve both issues always remains a challenge. In this work, we have designed such a nanocatalyst that may be helpful in solving these issues. A hydrothermal method has been used for the synthesis of Bi2S3 and CeO2, and their nanocomposite (Bi2S3/CeO2) has been prepared by a two-step method. X-ray diffraction results confirm the formation of the target materials. High resolution transmission electron microscopy and scanning electron microscopy show that Bi2S3 is rod-shaped and CeO2 is in the form of spherical particles. Both Bi2S3 and CeO2 are well distributed in the nanocomposite. The optical properties of the obtained nanocatalysts are analyzed by UV/visible absorption spectroscopy and photoluminescence spectroscopy. X-ray photoelectron spectra are used to determine the position of the valence band. All the synthesized materials are applied to the photoreduction of CO2 with water under visible-light irradiation (λ ≥ 420 nm). The Bi2S3/CeO2 nanocomposite exhibits higher yields of methane and methanol than the individual semiconductors. Moreover, the nanocomposite shows improved stability compared to the individual catalysts.
Co-reporter:Jiarui Jin, Yanjie Wang and Tao He
RSC Advances 2015 vol. 5(Issue 121) pp:100244-100250
Publication Date(Web):13 Nov 2015
DOI:10.1039/C5RA21888H
BiOCl nanosheets with different percentages of exposed {001} facets were prepared by a controlled facile hot-injection technique. The synthesis was conducted using bismuth chloride as a metal precursor, octadecene as a solvent, and oleic acid, oleylamine and octadecene as morphology-control agents. The presence of trace amounts of water in the reaction system leads to mild hydrolysis. The obtained BiOCl nanosheets with highly exposed {001} facets exhibited high activity for photocatalytic reduction of CO2 to CH4. Moreover, the thinner the nanosheets, the higher the production yield. The detailed mechanism has been studied. This work may afford a feasible protocol for the preparation of BiOCl nanosheets with high photocatalytic activity.
Co-reporter:Muhammad Fahad Ehsan, Muhammad Naeem Ashiq and Tao He
RSC Advances 2015 vol. 5(Issue 8) pp:6186-6194
Publication Date(Web):15 Dec 2014
DOI:10.1039/C4RA13593H
Hollow and mesoporous microstructures have been found to be an attractive class of materials due to their superior physical properties and potential applications. In the present work, a hydrothermal method has been used to synthesize hollow and mesoporous ZnTe hierarchical microspheres. The as-synthesized microspheres are characterized by a variety of techniques, including X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy, transmission electron microscopy, high resolution transmission electron microscopy, X-ray photoelectron spectroscopy and ultraviolet-visible spectroscopy. Nitrogen adsorption–desorption measurements and the curve of relative pore size distribution via Brunauer–Emmett–Teller analysis confirm the existence of mesopores in the obtained nanomaterials. Different reaction parameters such as NaOH concentration, reaction temperature and time, and concentration of the tellurium precursor have been studied and the detailed growth mechanism has been proposed. These hollow and mesoporous microspheres are also used for the photoreduction of carbon dioxide into methane under visible-light illumination (λ ≥ 420 nm) with a solar energy conversion efficiency of 0.072%.
Co-reporter:Yan Huang, Yanjie Wang, Yiqing Bi, Jiarui Jin, Muhammad Fahad Ehsan, Min Fu and Tao He
RSC Advances 2015 vol. 5(Issue 42) pp:33254-33261
Publication Date(Web):02 Apr 2015
DOI:10.1039/C5RA04227E
Hydroxyl-rich g-C3N4 nanosheets were prepared by ultrasonic exfoliation of bulk g-C3N4 in water. The samples were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, atomic force microscopy, UV-vis absorption spectroscopy, photoluminescence spectroscopy, time-resolved fluorescence decay spectroscopy, Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy and photocurrent response. The results indicated that the bulk g-C3N4 was exfoliated to five or six layers. The specific surface area increased from 8.66 m2 g−1 for the bulk g-C3N4 to 26.48 m2 g−1 for the nanosheets. More importantly, the amount of hydroxyl group on the g-C3N4 surface increased greatly upon ultrasonic treatment in water. Meanwhile, the separation rate of charge carriers was improved greatly and the conduction band potential shifts to a more negative value. All these can explain the enhanced activity of g-C3N4 nanosheets for visible-light photocatalytic reduction of CO2.
Co-reporter:Feng Bi;Muhammad Fahad Ehsan;Wei Liu
Chinese Journal of Chemistry 2015 Volume 33( Issue 1) pp:112-118
Publication Date(Web):
DOI:10.1002/cjoc.201400476
Abstract
In the past few decades there has been a remarkable rise in the study of visible-light photocatalytic reduction of carbon dioxide (CO2) into value-added chemicals such as methane (CH4) with water as reducing agent in order to prevent global warming and energy crisis. However, so far the conversion efficiency leaves much to be enhanced under sunlight irradiation. In this work, Cu2O hollow nanospheres were synthesized via soft-template method and were combined with TiO2 through in-situ hydrolysis of Ti(OBu)4 under sonication. The obtained photocatalysts of Cu2O and Cu2O/TiO2 composite were characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy, X-ray diffraction, UV-visible diffuse reflectance spectroscopy, and X-ray photoelectron spectroscopy. Compared to Cu2O hollow nanospheres, the Cu2O/TiO2 composite exhibited higher efficiency in photocatalytic reduction of CO2 into CH4 under visible-light irradiation (λ⪖420 nm). This is because of the formation of a p-n heterojunction in the composites, resulting in efficient suppression of recombination of the photogenerated electrons and holes as well as an improved stability of the catalyst and, thereby, the improved visible-light photocatalytic activity.
Co-reporter:Sivakumar Palanisamy, Lanqin Yan, Xuehua Zhang and Tao He
Analytical Methods 2015 vol. 7(Issue 8) pp:3438-3447
Publication Date(Web):03 Mar 2015
DOI:10.1039/C4AY03061C
Herein, we have reported worm-like silver (Ag) clusters deposited on glass substrate via radio frequency sputtering for surface enhanced Raman scattering (SERS) detection of dopamine (DA) in the presence of excess ascorbic acid (AA) and uric acid (UA). The SERS enhancement was optimized by tuning the cluster size and film thickness of Ag by controlling sputtering parameters like time, pressure and power. The selectivity of the optimized Ag thin film for DA detection was studied by adding 100-fold excess of AA and UA. The limit of detection for optimized Ag film was calculated to be 8.3 × 10−9 M at a signal to noise ratio (S/N) of ∼3. The enhancement factor was estimated to be of the order of 107.
Co-reporter:Naeem Ashiq Muhammad;Yanjie Wang;Fahad Ehsan Muhammad
Science China Materials 2015 Volume 58( Issue 8) pp:634-639
Publication Date(Web):2015 August
DOI:10.1007/s40843-015-0077-7
The utilization of CO2 and solar energy have drawn much attention due to global warming and fuel crisis. Of particular interest in our research, we prepared strontium zirconate (SrZrO3) nanoparticles as the photocatalyst to convert CO2 into value-added products. SrZrO3 nanoparticles were successfully synthesized via a sonochemical method and applied to the photoreduction of CO2. The samples were characterized by X-ray diffraction, Raman spectroscopy, scanning electron microscopy, Brunauere Emmette Teller measurement, X-ray photoelectron spectroscopy and UV-vis absorption spectroscopy. Ethanol, methane and carbon monoxide were the major products with the yield respectively as follows, 41 μmol g‒1, 2.57 μmol g‒1 and 1.6 μmol g‒1 after 4 h of reaction. The reason for the multiple photoreduction products is briefly discussed. Our work indicates that the as-prepared SrZrO3 nanoparticles can be used as a promising photocatalyst in turning CO2 into value-added chemicals.全球变暖和能源危机使得人们开始同时关注二氧化碳和太阳能的利用. 在本工作中, 我们制备了SrZrO3纳米颗粒, 并将其 作为催化剂使二氧化碳转化为高能量附加值产品. 我们利用超声化学法成功制备了SrZrO3纳米材料, 并通过X射线衍射(XRD)、拉曼光 谱、扫描电子显微镜(SEM)、BET比表面积分析、X射线光电子能谱(XPS)以及紫外-可见吸收光谱(UV/vis)等对样品进行了相应表征. 将SrZrO3作为催化剂, 在300W氙灯光源照射下进行光催化还原二氧化碳实验, 结果表明乙醇、甲烷和一氧化碳是主要的光催化产物, 反应进行4小时后, 三种产物相应的产量分别为41、2.57和1.6 μmol g−1. 论文分析了三种产物生成的原因. 本研究工作表明, SrZrO3纳米 材料可以作为一种有效的催化剂应用于光催化还原二氧化碳.
Co-reporter:Shan Lu, Shasha Wang, Ruobing Han, Ting Feng, Lingju Guo, Xuehua Zhang, Dongsheng Liu and Tao He
Journal of Materials Chemistry A 2014 vol. 2(Issue 32) pp:12805-12811
Publication Date(Web):09 Jun 2014
DOI:10.1039/C4TA02193B
Many different materials have been used as alternative counter electrodes (CEs) for dye-sensitized solar cells (DSSCs) mainly due to the high cost of Pt CEs. So far the majority of reported work has focused on the modulation of conductivity and morphology of the CEs. The working mechanism is still unclear, specifically that of the electrocatalysis. Here it is elucidated for the first time by using polypyrrole (PPy) as the target material. The electrocatalysis is mainly comprised of formation of the weakly and strongly bonded iodine species, and formation and reduction of the intermediates. This mechanism may be valid for other CEs too. We envision that this work can help to better understand and optimize the performance of DSSCs fabricated using alternative CEs.
Co-reporter:Yin Qiu, Shan Lu, Shasha Wang, Xuehua Zhang, Shengtai He, Tao He
Journal of Power Sources 2014 Volume 253() pp:300-304
Publication Date(Web):1 May 2014
DOI:10.1016/j.jpowsour.2013.12.061
•SDS can act as both dopant and surfactant during PANI electropolymerization.•SDS can improve the microstructure and conductivity of resultant PANI films.•PANI films prepared with SDS have high catalytic activity on I3− reduction.•PANI-SDS CE based DSSCs exhibit comparable power conversion efficiency to Pt CE.Polyaniline (PANI) counter electrode (CE) has been fabricated for dye-sensitized solar cells (DSSCs) via electropolymerization in the presence of sodium dodecyl sulfate (SDS), which can act as both dopant and surfactant. The introduction of SDS in the synthetic solution for PANI can improve the microstructure and conductivity of resultant thin film and greatly increase the catalytic activity of the as-prepared PANI film for I3− reduction. The DSSCs based on the resultant PANI CEs achieve a remarkable power conversion efficiency of 7.0%, about 95% of that based on conventional Pt CEs (7.4%). The results indicate that the PANI film prepared with SDS may substitute the expensive Pt as the CEs for DSSCs application.
Co-reporter:Zhengkai Guo, Xuemin Li, Xuehua Zhang, Zishen Guan and Tao He
Physical Chemistry Chemical Physics 2014 vol. 16(Issue 23) pp:11502-11508
Publication Date(Web):17 Apr 2014
DOI:10.1039/C4CP00816B
Titanium dioxide (TiO2) nanotubes are prepared by electrochemical anodization using Ti metal foils under a DC bias of 30 V for 20 h. The electrolyte is a mixture of formamide (FA) and ethylene glycol (EG), which contains NH4F (0.3 wt%) and H2O (2.0 v%). The diameter and wall thickness of the nanotubes decrease with the increase of EG content, while the length first decreases with the increase of EG content and then increases again. An O-ring-like pattern is formed on the outer surface of TiO2 nanotubes upon the introduction of FA into the EG electrolyte, upon which the surface becomes rougher and rougher with increasing FA content. This is caused by the breaking and re-establishment of a double layer at the interface. All of the observed phenomena are closely related to the conductivity and viscosity of the electrolyte as well as the formation of hydrogen bond in the system. The proposed mechanism is confirmed by introducing hydroxyl ions into the pure EG electrolyte.
Co-reporter:Muhammad Fahad Ehsan, Muhammad Naeem Ashiq, Feng Bi, Yiqing Bi, Sivakumar Palanisamy and Tao He
RSC Advances 2014 vol. 4(Issue 89) pp:48411-48418
Publication Date(Web):16 Sep 2014
DOI:10.1039/C4RA06828A
Limited fossil fuel resources and increasingly stringent requirement of environmental protection from major greenhouse gases, including carbon dioxide (CO2), which results directly from the burning of fossil fuels, energy savings and greenhouse-effect alleviation have emerged as major global concerns. The development of an “artificial photosynthetic system” (APS) having both the analogous important structural elements and the reaction features of photosynthesis to achieve solar-driven water splitting and CO2 reduction is highly challenging. Herein, it has been demonstrated that SrTiO3–ZnTe can be utilized as an efficient APS for the photoreduction of CO2 into methane (CH4) under visible-light irradiation (≥420 nm). The results indicate that the combination of ZnTe with SrTiO3 visibly increases the formation of CH4 by efficiently promoting electron transfer from the conduction band of ZnTe to that of SrTiO3 under visible-light irradiation, and thereby demonstrate this to be a promising candidate for the photocatalytic conversion of CO2 into hydrocarbon fuels.
Co-reporter:Jiarui Jin ; Xuehua Zhang
The Journal of Physical Chemistry C 2014 Volume 118(Issue 43) pp:24877-24883
Publication Date(Web):October 13, 2014
DOI:10.1021/jp508814y
In pursuit low-cost and facile synthesis of counter electrode (CE) material as an alternative to expensive Pt for dye-sensitized solar cells (DSSCs), a new procedure for preparing CEs without any postannealing treatment is reported by using a self-assembly technique to obtain a stable thin film as the CE in DSSCs. The self-assembled CoS2 film is prepared via a facile two-step approach, which shows high electrocatalytic activity on the I–/I3– redox reaction. A maximum power conversion efficiency of 6.78% is achieved for the DSSC based on the resultant CoS2 nanocrystal CE, which is close to that of the cell using a Pt CE (7.38%) under the same condition. Moreover, the flexible device based on a CoS2 CE exhibits an efficiency of 6.40%. The results indicate that the self-assembled CoS2 nanoctrystal film may replace the expensive Pt CE for DSSC application, especially for the large-scale flexible devices.
Co-reporter:Bin Wang, Lingju Guo, Meng He and Tao He
Physical Chemistry Chemical Physics 2013 vol. 15(Issue 24) pp:9891-9898
Publication Date(Web):08 Apr 2013
DOI:10.1039/C3CP50862E
Owing to potential industrial applications and fundamental significance, tailored synthesis of well-defined anatase TiO2 nanocrystals with exposed highly reactive {001} facets has stimulated great research interest. In this work, surface-fluorinated anatase TiO2 nanocrystals have been successfully prepared by using an ionic liquid (IL) assisted hydrothermal synthetic route. TiCl4 is used as precursor, and 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim]+[BF4]−) as morphology-controlling agent. The anion of the IL plays a key role in controlling the crystallization process via a dissolution–recrystallization process. Compared with the benchmark material Degussa P25, the fluorinated anatase TiO2 nanocrystals exhibit superior photocatalytic activity.
Co-reporter:Xuemin Li, Yin Qiu, Shasha Wang, Shan Lu, Robert I. Gruar, Xuehua Zhang, Jawwad A. Darr and Tao He
Physical Chemistry Chemical Physics 2013 vol. 15(Issue 35) pp:14729-14735
Publication Date(Web):04 Jul 2013
DOI:10.1039/C3CP51705E
TiO2 compact layers (CLs) prepared by electrophoretic deposition (EPD) from an aqueous nanoparticle suspension were used in dye-sensitized solar cells (DSSCs) to prevent charge recombination at the interface between the transparent fluorine-doped tin oxide (FTO) substrate and the electrolyte. The TiO2 nanopowder (ca. 4.5 nm diameter) suspension used in the EPD process was prepared via a continuous hydrothermal flow synthesis pilot plant (at a production rate of ca. 0.38 kg h−1). The optimal thickness of the TiO2 CL for DSSCs is about 115 nm. Compared to the DSSCs without a CL, the optimal cell has shown improved short-circuit current density (JSC) and solar energy conversion efficiency by 13.1% and 15.0%, respectively. The mechanism for improved performance has been studied by the measurements of dark current and electrochemical impedance spectra. The interfacial charge transfer resistance at the FTO/electrolyte interface is increased after fabricating a CL in the cell, indicating inhibited electron recombination at the interface.
Co-reporter:Xuemin Li, Zhengkai Guo and Tao He
Physical Chemistry Chemical Physics 2013 vol. 15(Issue 46) pp:20037-20045
Publication Date(Web):09 Oct 2013
DOI:10.1039/C3CP53531B
The chromium doped titanium dioxide (Cr–TiO2) has been synthesized using a hydrothermal method. The as-prepared samples have been characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), transmission electron microscopy (TEM), high resolution TEM (HR-TEM), XPS valence band spectroscopy, UV-vis diffuse reflectance spectroscopy (UV-vis DR), photoluminescence (PL) spectroscopy and time resolved PL (TR-PL) spectroscopy. The doping mechanism and related influence on the photocatalytic performance of TiO2 are thus proposed. The doped Cr3+ ions can replace the Ti atoms in the lattice with oxygen vacancy compensation, distribute homogeneously in the framework of TiO2 crystals, and may make the n-type TiO2 less n-type or more p-type due to the resultant formation of oxygen vacancies, resulting in absorption of visible light, decrease of the intensity of PL emission and prolonged lifetime of photogenerated charge carriers. Compared with TiO2, the doped samples exhibit an improved visible-light photocatalytic activity. The influence of nitrogen modification has also been studied. We envision that these results would afford a better understanding of the doping mechanism of TiO2 using metal ions and, therefore, may provide a feasible way to prepare the TiO2-based photocatalysts for real applications.
Co-reporter:Xuemingyue Han, Shuqing Sun, Tao He
Colloids and Surfaces B: Biointerfaces 2013 Volume 108() pp:66-71
Publication Date(Web):1 August 2013
DOI:10.1016/j.colsurfb.2013.02.030
Self-assembled monolayers (SAMs) formed by adsorption of octadecylphosphonic acid (ODPA) on zirconium mediated glass substrates were prepared. In this sandwich structure, Zr4+ was used as a bi-linker to bind phosphonic acid head group in ODPA to glass substrates. The contact angle of the as-prepared SAMs was measured to be around 104°. X-ray photoelectron spectroscopy (XPS) characterization indicated the modification of Zr4+ on glass substrates was critical for the formation of reasonably dense, well-ordered SAMs similar in quality to those typically formed on other metal oxide surfaces. Bifunctional molecule, 10-mercaptodecanylphosphonic acid (MDPA), bearing thiol terminal groups for various chemical reactions, was synthesized and formed SAMs on glass using the same approach, which allowed us to control the surface chemistry and functionality through photooxidation of the thiol terminal group. Photopatterning of proteins was performed first by exposing the SAMs to UV light through a mask, followed by protein immobilization to the masked regions through a heterobifunctional linker, while the exposed areas prohibit nonspecific protein absorption. The present strategy, which combined the SAMs assembly and photolithography, offered a facile approach for the fabrication of biomolecule patterning and could be applied to construction of biochips and other applications.Graphical abstractHighlights► Self-assembled monolayers of alkylphosphonic acid on zirconium mediated glass substrates were prepared. ► Bifunctional 10-mercaptodecanylphosphonic acid was synthesized and used to develop a thiol terminal surface using the same approach. ► Exposure of the thiol terminal surface through a mask yields well-defined patterns that orient specific adsorption of proteins or antibodies.
Co-reporter:Enjun Wang, Peng Zhang, Yongmei Chen, Zhanwei Liu, Tao He and Yaan Cao
Journal of Materials Chemistry A 2012 vol. 22(Issue 29) pp:14443-14449
Publication Date(Web):21 May 2012
DOI:10.1039/C2JM30889D
Nitrogen and indium co-modified TiO2 was prepared by a simple sol–gel method. Under visible-light irradiation, the modified catalysts exhibited much higher photocatalytic activity for 4-chlorophenol photodegradation than both the as-prepared TiO2 and nitrogen-doped TiO2. The structure and properties of the resultant catalysts were characterized by XRD, BET, XPS, UV-vis DRS and PL techniques. It was found that unique chemical species, such as N–O and O–In–Clx (x = 1 or 2), existed on the surface of the nitrogen and indium co-modified TiO2. The surface-state energy levels introduced by these surface species were located close to the valence and conduction bands, respectively, which could lead to significant absorption in the visible-light region and facilitate the separation of photogenerated electrons and holes. Thus, the visible-light photocatalytic activity of TiO2 can be greatly improved by nitrogen and indium modification. We envision the opportunities for using such a method to develop TiO2-based visible-light photocatalysts suitable for practical applications.
Co-reporter:Jixiang Yuan, Qiang Wu, Peng Zhang, Jianghong Yao, Tao He, and Yaan Cao
Environmental Science & Technology 2012 Volume 46(Issue 4) pp:2330-2336
Publication Date(Web):January 19, 2012
DOI:10.1021/es203333k
Indium borate has been prepared by a sol–gel method. The structure, morphology, and photophysics of the resultant photocatalysts have been studied via the techniques of X-ray diffraction (XRD), transmission electron microscopy (TEM), and diffuse reflectance UV–visible light spectroscopy. These photocatalysts have been used to photodegrade 4-chlorophenol. The photocatalytic activity depends on the annealing temperature during preparation. It is found that borates can exhibit a high photodegradation activity under UV-light irradiation, for which the efficiency can be higher than that of as-prepared TiO2. This is explained according to the results of fluorescence spectra and valence band X-ray photoelectron spectroscopy (XPS). It is confirmed by the results of time-resolved photoluminescence decay spectra; i.e., the lifetime of electrons and holes involved in the radiative process can be longer for the borates than that for TiO2. This implies that indium borate can be a promising photocatalyst for future applications in treatment of environment contaminants.
Co-reporter:Fangyi Hu, Yujing Xia, Zisheng Guan, Xiong Yin, Tao He
Electrochimica Acta 2012 Volume 69() pp:97-101
Publication Date(Web):1 May 2012
DOI:10.1016/j.electacta.2012.02.084
ZnO compact layer has been fabricated on transparent conducting oxide glass and plastic polymer substrates at low temperature via electrodeposition. The results of dark current and cyclic voltammetric measurements demonstrate that the compact layer can effectively reduce the short circuit from transparent conducting oxide to electrolyte in dye-sensitized ZnO solar cells, leading to an increase of open-circuit photovoltage and fill factor of the devices and, thereby, the power conversion efficiency. The resultant plastic dye-sensitized ZnO solar cell presents an efficiency of 3.29% under illumination of 100 mW cm−2, AM 1.5G. This indicates that electrodeposition is a viable method to fabricate ZnO compact layer for high performance flexible devices.Highlights► ZnO compact layer is prepared via simple electrochemical method at low temperature. ► Compact layer can effectively block electron transfer from TCO to electrolyte. ► DSC PCE is improved by 17% when ZnO compact layer is introduced. ► Plastic DSCs with ZnO compact layer show a PCE of 3.29% under AM1.5 100 mW cm−2. ► The above efficiency is comparable to that with high temperature sintering step.
Co-reporter:Xin Zhang, Yujing Xia, Tao He
Materials Chemistry and Physics 2012 Volume 137(Issue 2) pp:622-627
Publication Date(Web):14 December 2012
DOI:10.1016/j.matchemphys.2012.09.065
Zinc oxide (ZnO) is a versatile material that has been used in photocatalysis, solar cells, chemical sensors, and piezoelectric transducers. All these are directly related to its surface properties. Here ZnO nanorod arrays were successfully synthesized by electrochemical deposition method, the surface of which was modified by dopamine, a robust anchor. Compared with pristine ZnO sample, the surface modification can greatly enhance the ultraviolet and visible-light photoluminescence. This is due to the formation of polydopamine on the nanorod surface, which may act as a dye that can be photoexcited. The resultant photogenerated electrons can inject into the conduction band of ZnO and take part in the luminescent process. These results may provide a foundation for real applications of ZnO nanomaterials in optoelectronic devices and, especially, for the applications in biological field as both the dopamine and ZnO are biocompatible materials.Highlights► ZnO nanorod arrays are prepared via a simple electrochemical deposition method. ► Photoluminescence of ZnO nanorods can be greatly enhanced via dopamine treatment. ► Dye-like polydopamine can be formed on the nanorod surface upon dopamine treatment. ► Photogenerated electrons in polydopamine can inject into conduction band of ZnO. ► Enhanced photoluminescence is because more electrons can contribute to it.
Co-reporter:Xiong Yin;Bin Wang;Meng He
Nano Research 2012 Volume 5( Issue 1) pp:1-10
Publication Date(Web):2012 January
DOI:10.1007/s12274-011-0178-X
Co-reporter:Xin Zhang, Bin Wang, Xuehua Zhang, Tao He
Sensors and Actuators B: Chemical 2012 Volumes 166–167() pp:695-701
Publication Date(Web):20 May 2012
DOI:10.1016/j.snb.2012.03.042
A multilayer thin film electrode has been prepared by using polyacrylic-acid coated nano-ceria and poly(diallyldimethylammonium chloride) via a layer-by-layer assembly method. The particles have been studied by the techniques of X-ray diffraction, transmission electron microscope, UV–vis absorption, and dynamic light scattering. The laminar growth of the thin film has been monitored by using UV–vis absorption spectra. The obtained multilayer film shows good sensitivity and selectivity for dopamine detection in the presence of excess ascorbic acid interferent using electrochemical method. We envision that this may provide a feasible way for in vivo detection of dopamine in the presence of excess interferents.
Co-reporter:Enjun Wang, Tao He, Lusong Zhao, Yongmei Chen and Yaan Cao
Journal of Materials Chemistry A 2011 vol. 21(Issue 1) pp:144-150
Publication Date(Web):15 Oct 2010
DOI:10.1039/C0JM02539A
Tin and nitrogen co-doped titania has been prepared by a hydrolysis precipitation method and studied by X-ray diffraction, X-ray photoelectron spectroscopy, diffuse reflectance UV-vis absorption spectra, and photoluminescence. The surface area has been determined by using the BET method. Tin is incorporated into the TiO2 crystal lattice in substitutional mode, while nitrogen is present as surface species. The resultant energy levels of tin doping and nitrogen surface states are located inside the bandgap, which are close to the conduction and valence bands, respectively. Hence, co-doping of tin and nitrogen can greatly enhance the absorption in the visible light region and inhibit the recombination of photogenerated charge carriers, leading to a higher photocatalytic activity for the co-doped catalyst than pure TiO2 and solely doped TiO2 with nitrogen or tin for degradation of 4-chlorophenol under both visible and UV-light irradiation. This indicates that co-doping simultaneously with two foreign elements is a feasible way to improve the photocatalytic activity of TiO2.
Co-reporter:Hongchun Qin, Weiying Li, Yujing Xia, and Tao He
ACS Applied Materials & Interfaces 2011 Volume 3(Issue 8) pp:3152
Publication Date(Web):July 19, 2011
DOI:10.1021/am200655h
Different composite films prepared by coupling ZnO and nitrogen-doped ZnO (N-ZnO) were used to photodegrade humic acids (HA). The catalysts exhibit an activity in the order of glass/ZnO/N-ZnO > glass/N-ZnO >glass/ZnO > glass/N-ZnO/ZnO when light is irradiated from the film to glass substrate. However, glass/ZnO/N-ZnO exhibits a lower activity than glass/N-ZnO/ZnO when light is illuminated from glass to film. Moreover, glass/ZnO/N-ZnO shows a lower activity when light is irradiated from glass to film than that irradiated in the opposite direction. These results suggest that it is not always the case that the presence of a heterojunction at interface of two semiconductors can definitely result in improving the photoactivity of the heterostructure although it can suppress the recombination of photogenerated charge carriers. They also indicate that photodegradation of HA is mainly via the oxidization by HO• (rather than directly by O2– and h+), which is produced mainly by the reactions with h+. This implies the importance of fabrication a right heterojunction at the interface between the composite materials when they are used for photocatalysis. We envision that this work will help to develop new photocatalysts, as well as to understand better the photocatalytic mechanism.Keywords: heterojunction; humic acid; hydroxyl radical; photocatalysis; zinc oxide;
Co-reporter:Yiqing Bi, Muhammad Fahad Ehsan, Yan Huang, Jiarui Jin, Tao He
Journal of CO2 Utilization (March 2016) Volume 13() pp:
Publication Date(Web):1 March 2016
DOI:10.1016/j.jcou.2015.11.007
Co-reporter:Yiqing Bi, Muhammad Fahad Ehsan, Yan Huang, Jiarui Jin, Tao He
Journal of CO2 Utilization (December 2015) Volume 12() pp:43-48
Publication Date(Web):1 December 2015
DOI:10.1016/j.jcou.2015.10.004
•Cr-doped SrTiO3 is successfully synthesized by a facile ultrasonic chemical route.•Cr-doped SrTiO3 exhibits a large specific surface area and visible-light response.•CO2 is photoreduced into CH4 over Cr-doped SrTiO3 under visible-light irradiation.•Cr-doped SrTiO3 shows good stability against photoirradiation.Visible-light-driven Cr-doped SrTiO3 was synthesized through ultrasonic chemical method. Its specific surface area is 54.3 m2 g–1 due to the relatively small particle size. X-ray diffraction pattern and X-ray photoelectron spectra confirmed the crystal structure and Sr substitution. UV–vis absorption spectra indicated that the Cr doping can lead to visible-light absorption. In addition, the oxygen vacancy in Cr-doped SrTiO3 also showed visible-light absorption. The obtained Cr-doped SrTiO3 was used to photocatalytically reduce CO2 into CH4 with a yield of 8.8 μmol g–1 after 10-h reaction. Moreover, the Cr-doped SrTiO3 exhibited good photostability.Cr-doped SrTiO3 synthesized by ultrasonic chemical route can photoreduce CO2 into CH4 under visible-light irradiation with a yield of 8.8 μmol g−1.Download full-size image
Co-reporter:Enjun Wang, Peng Zhang, Yongmei Chen, Zhanwei Liu, Tao He and Yaan Cao
Journal of Materials Chemistry A 2012 - vol. 22(Issue 29) pp:NaN14449-14449
Publication Date(Web):2012/05/21
DOI:10.1039/C2JM30889D
Nitrogen and indium co-modified TiO2 was prepared by a simple sol–gel method. Under visible-light irradiation, the modified catalysts exhibited much higher photocatalytic activity for 4-chlorophenol photodegradation than both the as-prepared TiO2 and nitrogen-doped TiO2. The structure and properties of the resultant catalysts were characterized by XRD, BET, XPS, UV-vis DRS and PL techniques. It was found that unique chemical species, such as N–O and O–In–Clx (x = 1 or 2), existed on the surface of the nitrogen and indium co-modified TiO2. The surface-state energy levels introduced by these surface species were located close to the valence and conduction bands, respectively, which could lead to significant absorption in the visible-light region and facilitate the separation of photogenerated electrons and holes. Thus, the visible-light photocatalytic activity of TiO2 can be greatly improved by nitrogen and indium modification. We envision the opportunities for using such a method to develop TiO2-based visible-light photocatalysts suitable for practical applications.
Co-reporter:Zhengkai Guo, Xuemin Li, Xuehua Zhang, Zishen Guan and Tao He
Physical Chemistry Chemical Physics 2014 - vol. 16(Issue 23) pp:NaN11508-11508
Publication Date(Web):2014/04/17
DOI:10.1039/C4CP00816B
Titanium dioxide (TiO2) nanotubes are prepared by electrochemical anodization using Ti metal foils under a DC bias of 30 V for 20 h. The electrolyte is a mixture of formamide (FA) and ethylene glycol (EG), which contains NH4F (0.3 wt%) and H2O (2.0 v%). The diameter and wall thickness of the nanotubes decrease with the increase of EG content, while the length first decreases with the increase of EG content and then increases again. An O-ring-like pattern is formed on the outer surface of TiO2 nanotubes upon the introduction of FA into the EG electrolyte, upon which the surface becomes rougher and rougher with increasing FA content. This is caused by the breaking and re-establishment of a double layer at the interface. All of the observed phenomena are closely related to the conductivity and viscosity of the electrolyte as well as the formation of hydrogen bond in the system. The proposed mechanism is confirmed by introducing hydroxyl ions into the pure EG electrolyte.
Co-reporter:Enjun Wang, Tao He, Lusong Zhao, Yongmei Chen and Yaan Cao
Journal of Materials Chemistry A 2011 - vol. 21(Issue 1) pp:NaN150-150
Publication Date(Web):2010/10/15
DOI:10.1039/C0JM02539A
Tin and nitrogen co-doped titania has been prepared by a hydrolysis precipitation method and studied by X-ray diffraction, X-ray photoelectron spectroscopy, diffuse reflectance UV-vis absorption spectra, and photoluminescence. The surface area has been determined by using the BET method. Tin is incorporated into the TiO2 crystal lattice in substitutional mode, while nitrogen is present as surface species. The resultant energy levels of tin doping and nitrogen surface states are located inside the bandgap, which are close to the conduction and valence bands, respectively. Hence, co-doping of tin and nitrogen can greatly enhance the absorption in the visible light region and inhibit the recombination of photogenerated charge carriers, leading to a higher photocatalytic activity for the co-doped catalyst than pure TiO2 and solely doped TiO2 with nitrogen or tin for degradation of 4-chlorophenol under both visible and UV-light irradiation. This indicates that co-doping simultaneously with two foreign elements is a feasible way to improve the photocatalytic activity of TiO2.
Co-reporter:Sivakumar Palanisamy, Xuehua Zhang and Tao He
Journal of Materials Chemistry A 2015 - vol. 3(Issue 29) pp:NaN6025-6025
Publication Date(Web):2015/06/22
DOI:10.1039/C5TB00495K
Colorimetric detection of dopamine has the advantage of simplicity in operation and instrumentation. Herein, a highly sensitive and selective colorimetric biosensor with fast response has been developed by using 4′-aminobenzo-18-crown-6 (ABCE) and 4-mercaptophenyl boronic acid (MPBA) modified Au nanoparticles. The modified probe shows an excellent detection limit of 6.0 nM of dopamine at a S/N of 2.01 and about 46 nM at a S/N of 3 within microseconds response. It exhibits excellent detection selectivity even in 1000-fold excess of many different interferents like metal ions, uric acid and ascorbic acid. All these may make it fulfill the requirements for in vivo analysis.
Co-reporter:Xuemin Li, Zhengkai Guo and Tao He
Physical Chemistry Chemical Physics 2013 - vol. 15(Issue 46) pp:NaN20045-20045
Publication Date(Web):2013/10/09
DOI:10.1039/C3CP53531B
The chromium doped titanium dioxide (Cr–TiO2) has been synthesized using a hydrothermal method. The as-prepared samples have been characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), transmission electron microscopy (TEM), high resolution TEM (HR-TEM), XPS valence band spectroscopy, UV-vis diffuse reflectance spectroscopy (UV-vis DR), photoluminescence (PL) spectroscopy and time resolved PL (TR-PL) spectroscopy. The doping mechanism and related influence on the photocatalytic performance of TiO2 are thus proposed. The doped Cr3+ ions can replace the Ti atoms in the lattice with oxygen vacancy compensation, distribute homogeneously in the framework of TiO2 crystals, and may make the n-type TiO2 less n-type or more p-type due to the resultant formation of oxygen vacancies, resulting in absorption of visible light, decrease of the intensity of PL emission and prolonged lifetime of photogenerated charge carriers. Compared with TiO2, the doped samples exhibit an improved visible-light photocatalytic activity. The influence of nitrogen modification has also been studied. We envision that these results would afford a better understanding of the doping mechanism of TiO2 using metal ions and, therefore, may provide a feasible way to prepare the TiO2-based photocatalysts for real applications.
Co-reporter:Shan Lu, Shasha Wang, Ruobing Han, Ting Feng, Lingju Guo, Xuehua Zhang, Dongsheng Liu and Tao He
Journal of Materials Chemistry A 2014 - vol. 2(Issue 32) pp:NaN12811-12811
Publication Date(Web):2014/06/09
DOI:10.1039/C4TA02193B
Many different materials have been used as alternative counter electrodes (CEs) for dye-sensitized solar cells (DSSCs) mainly due to the high cost of Pt CEs. So far the majority of reported work has focused on the modulation of conductivity and morphology of the CEs. The working mechanism is still unclear, specifically that of the electrocatalysis. Here it is elucidated for the first time by using polypyrrole (PPy) as the target material. The electrocatalysis is mainly comprised of formation of the weakly and strongly bonded iodine species, and formation and reduction of the intermediates. This mechanism may be valid for other CEs too. We envision that this work can help to better understand and optimize the performance of DSSCs fabricated using alternative CEs.
Co-reporter:Sana Ijaz, Muhammad Fahad Ehsan, Muhammad Naeem Ashiq and Tao He
Catalysis Science & Technology (2011-Present) 2015 - vol. 5(Issue 12) pp:NaN5215-5215
Publication Date(Web):2015/08/11
DOI:10.1039/C5CY00955C
Due to shortage of fossil fuels and rapid growth of energy demand, exploration of new energy resources becomes essential. Moreover, the CO2 level is increasing day by day, which has caused global warming as well as environmental pollution. Designing a suitable photocatalyst that can solve both issues always remains a challenge. In this work, we have designed such a nanocatalyst that may be helpful in solving these issues. A hydrothermal method has been used for the synthesis of Bi2S3 and CeO2, and their nanocomposite (Bi2S3/CeO2) has been prepared by a two-step method. X-ray diffraction results confirm the formation of the target materials. High resolution transmission electron microscopy and scanning electron microscopy show that Bi2S3 is rod-shaped and CeO2 is in the form of spherical particles. Both Bi2S3 and CeO2 are well distributed in the nanocomposite. The optical properties of the obtained nanocatalysts are analyzed by UV/visible absorption spectroscopy and photoluminescence spectroscopy. X-ray photoelectron spectra are used to determine the position of the valence band. All the synthesized materials are applied to the photoreduction of CO2 with water under visible-light irradiation (λ ≥ 420 nm). The Bi2S3/CeO2 nanocomposite exhibits higher yields of methane and methanol than the individual semiconductors. Moreover, the nanocomposite shows improved stability compared to the individual catalysts.
Co-reporter:Xuemin Li, Yin Qiu, Shasha Wang, Shan Lu, Robert I. Gruar, Xuehua Zhang, Jawwad A. Darr and Tao He
Physical Chemistry Chemical Physics 2013 - vol. 15(Issue 35) pp:NaN14735-14735
Publication Date(Web):2013/07/04
DOI:10.1039/C3CP51705E
TiO2 compact layers (CLs) prepared by electrophoretic deposition (EPD) from an aqueous nanoparticle suspension were used in dye-sensitized solar cells (DSSCs) to prevent charge recombination at the interface between the transparent fluorine-doped tin oxide (FTO) substrate and the electrolyte. The TiO2 nanopowder (ca. 4.5 nm diameter) suspension used in the EPD process was prepared via a continuous hydrothermal flow synthesis pilot plant (at a production rate of ca. 0.38 kg h−1). The optimal thickness of the TiO2 CL for DSSCs is about 115 nm. Compared to the DSSCs without a CL, the optimal cell has shown improved short-circuit current density (JSC) and solar energy conversion efficiency by 13.1% and 15.0%, respectively. The mechanism for improved performance has been studied by the measurements of dark current and electrochemical impedance spectra. The interfacial charge transfer resistance at the FTO/electrolyte interface is increased after fabricating a CL in the cell, indicating inhibited electron recombination at the interface.
Co-reporter:Bin Wang, Lingju Guo, Meng He and Tao He
Physical Chemistry Chemical Physics 2013 - vol. 15(Issue 24) pp:NaN9898-9898
Publication Date(Web):2013/04/08
DOI:10.1039/C3CP50862E
Owing to potential industrial applications and fundamental significance, tailored synthesis of well-defined anatase TiO2 nanocrystals with exposed highly reactive {001} facets has stimulated great research interest. In this work, surface-fluorinated anatase TiO2 nanocrystals have been successfully prepared by using an ionic liquid (IL) assisted hydrothermal synthetic route. TiCl4 is used as precursor, and 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim]+[BF4]−) as morphology-controlling agent. The anion of the IL plays a key role in controlling the crystallization process via a dissolution–recrystallization process. Compared with the benchmark material Degussa P25, the fluorinated anatase TiO2 nanocrystals exhibit superior photocatalytic activity.
