Co-reporter:Wan Zhang, Changsheng Xie, Guozhu Zhang, Jian Zhang, Shunping Zhang, Dawen Zeng
Materials Chemistry and Physics 2017 Volume 186() pp:228-236
Publication Date(Web):15 January 2017
DOI:10.1016/j.matchemphys.2016.10.048
•The new composites composed of p-type LaFeO3 and n-type SnO2 were first attempted.•An enhanced sensitivity for CO2 detection is obtained at a relatively low temperature.•A quite short response time is achieved at the same time.•The mechanism of the enhanced performance concerning as-formed P-N junctions in the interfaces was investigated.Perovskite LaFeO3 nanocrystalline powder, synthesized by sol–gel method, was composited with SnO2 nanopowders to fabricate porous LaFeO3/SnO2 thick film sensors. The as-prepared sensors exhibit high gas sensitivity, fast response and low working temperature for CO2 detection. The optimal sensing performance of LaFeO3/SnO2 thick film sensors is obtained with the molar ratio of La/Sn = 1:1. The observed response is nearly 2 times higher than that of bare LaFeO3 at 4000 ppm CO2 and the response time is less than 20 s at 250 °C. CO2 sensing mechanism of the as-prepared nanocomposites porous film is addressed. The results demonstrate that the as-formed P-N junctions can greatly enhance the carrier transfer efficiency which is attributed to the improved sensing performance. Moreover, the hydroxyl species absorbed on the surface of the nanocomposites are also involved in the sensing process.
Co-reporter:Qiang Zhu;Huayao Li;Dawen Zeng
Nano Research 2016 Volume 9( Issue 10) pp:2972-3002
Publication Date(Web):2016 October
DOI:10.1007/s12274-016-1182-y
The controllability of persistent photoconductance (PPC) and charge/energy storage of ZnO nanorod arrays (NRAs) were demonstrated experimentally by tuning the nanorod diameter. The dependency of the ZnO NRAs’ photoelectric characteristics on the nanorod diameter suggests that the Debye length and photon penetration depth in ZnO could spatially partition a standalone nanorod into three different photoelectric functional regions (PFRs). Theoretically, a series of rate functions was employed to describe the different extrinsic/intrinsic carrier photogeneration/recombination dynamic sub-processes occurring in the different PFRs, associated with oxygen chemisorption/photodesorption, oxygen vacancy photoionization, and electron trapping by photoionized oxygen vacancies. On the basis of the coupled contributions of these different dynamic sub-processes in the photoelectric properties of the ZnO NRAs, a thorough-process photoelectric dynamic model (TPDM) was proposed using the simultaneous rate functions. Through solving the rate functions, the corresponding analytical equations could be employed to simulate the time-resolved PPC spectra of the ZnO NRAs, and then the quantitative parameters extracted to decipher the PPC and charge/energy storage mechanisms in the ZnO NRAs. In this way, the TPDM model provided a numerical-analytical method to quantitatively evaluate the photoelectric properties of ZnO NRA-based devices. Additionally, the TPDM model revealed how the different photoinduced carrier dynamics in the different PFRs could play functional roles in different optoelectronic applications, e.g., photodetectors, photocatalysts, solar cells and optical nonvolatile memories, and thus it illuminated a practical approach for the design of ZnO NRA-based devices via optimization of the modularized spatial configuration of the PFRs.
Co-reporter:Qiang Zhu, Changsheng Xie, Huayao Li, Jian Zhang, and Dawen Zeng
Chemistry of Materials 2015 Volume 27(Issue 8) pp:2861
Publication Date(Web):March 31, 2015
DOI:10.1021/cm504739f
In the past decades, many models have been developed to describe the photoconductance and the related photoresponse phenomena in wide-band gap metal oxides, but the related mechanisms and kinetics are still confused. Here, based on the persistent photoconductance observed in the porous ZnO nanocrystalline film, a donor photoionization model (DPM) is proposed to decipher the photoelectric kinetics both upon the sub-band gap and the above-band gap illuminations. In the DPM, the reaction rate equations and the related analytical functions are employed to numerically model the through processes of photoconductance spectra in a time-domain by comprehensively considering the photoelectric processes in ZnO such as the band-to-band transition, the donor photoionization, the surface oxygen adsorption/desorption, and the photogenerated electron recapture by donors. In the DPM simulation processes, some essential parameters, such as the electron yield from donor photoionization, the electron capture rates by donors, and the oxygen adsorption reaction rates on ZnO surface, are extracted quantitatively from the photoconductance spectra. The DPM analytical process herein reveals the photoresponse kinetics in detail and proposes a new insight into the basic theory of metal oxide photoresponse that might be helpful for further understanding the photoexcited carrier kinetics and the related photochemical processes.
Co-reporter:Shasha Zhang, Changsheng Xie, Guozhu Zhang, Qiang Zhu and Shunping Zhang
Physical Chemistry Chemical Physics 2015 vol. 17(Issue 27) pp:18045-18054
Publication Date(Web):15 Jun 2015
DOI:10.1039/C5CP02391B
Porous ZnO nanocrystalline films have been widely used in optoelectronic and gas-sensing applications. However, the effect mechanisms of the external fields, such as light, heat and atmosphere, are still controversial. In this work, the multi-variable coupling effects of the UV light, heat and oxygen were thoroughly studied by a newly proposed method, the central idea of which was to first isolate each effect of the fields on electron concentration and mobility, and then analyze how the coupling effects were achieved. Our results revealed the important roles of oxygen adsorption-induced interface barriers and photo-assisted thermal ionization first proposed here, because of which the positive coupling effect of UV light/heat and oxygen, as well as the negative coupling effect of UV light and heat was observed. Our work provides inspiration for studies on metal oxides from both the whole idea and the detailed argument.
Co-reporter:Shasha Zhang
The Journal of Physical Chemistry C 2015 Volume 119(Issue 1) pp:695-702
Publication Date(Web):December 5, 2014
DOI:10.1021/jp509105c
A simple and effective way to get electron concentration and mobility accurately is significant for the electronic and photoelectric applications of porous ZnO nanocrystalline film. On the basis of the defect ionization and the electron scattering, we proposed here a new temperature-programmed-dependent conductivity-based synchronous derivation method (TPDCBSD) to evaluate electron concentration and mobility of porous ZnO nanocrystalline film independently. The obtained results were consistent with others. Compared with the commonly used Hall-effect measurements, the TPDCBSD method is much more simple, has lower noise, and is convenient to couple external fields. More importantly, the extracted electron concentration and electron mobility are relatively independent. Besides, a series of physical parameters related to the effects of temperature and oxygen partial pressure were obtained, and the coupling effect of temperature and oxygen was discussed in this work, which are inspiring for the applications of porous ZnO nanocrystalline film.
Co-reporter:Jianwei Zhao, Changsheng Xie, Li Yang, Shunping Zhang, Guozhu Zhang, Ziming Cai
Applied Surface Science 2015 330() pp: 126-133
Publication Date(Web):1 March 2015
DOI:10.1016/j.apsusc.2014.12.194
•Lithium can enhance the sensing performance of ZnO.•The effects of Li doping were investigated using temperature dependent conductivity measurements.•Li doped ZnO can induce two forms of oxygen defects: oxygen vacancies and oxygen interstitials.•The synergistic effect of oxygen vacancies and oxygen interstitials is responsible for the sensing performance enhancement of Li doped ZnO.Li doped ZnO (Zn1−xLixO) nanoparticles with different content were synthesized. X-ray photoelectron spectroscopy (XPS) indicated that the ratio of oxygen to zinc for ZnO increased with increasing of Li content from x = 0 to 0.2, which had been attributed to the introduction of oxygen interstitial by Li dopant. The sensing performance and the temperature-dependent conductivity were investigated. It is observed that Li doped ZnO showed higher sensitivity and selectivity compared to the undoped ZnO. The 0.1 Li doped ZnO performed the maximum responses of 71.5 and 40.2 for 100 ppm methanol and formaldehyde, respectively, at 350 °C. The research showed that the oxygen vacancies served as active sites which supported the oxygen adsorption and reaction, oxygen interstitials served as active sites to oxidize the reducing gases and produce electrons. The enhanced sensing performance of Li doped ZnO was attributed to the synergistic effect of oxygen interstitials and oxygen vacancies.
Co-reporter:Chaoqun Yang, Qiang Zhu, Tao Lei, Huayao Li and Changsheng Xie
Journal of Materials Chemistry A 2014 vol. 2(Issue 44) pp:9467-9477
Publication Date(Web):12 Sep 2014
DOI:10.1039/C4TC01150C
In this paper, four kinds of WO3 films, namely, Pt-loaded hydrogenated WO3, Pt-loaded WO3, and hydrogen-treated and untreated WO3 films were synthesized and their photoelectric properties were investigated at room temperature. The quantitative results showed that the gas-sensitized WO3 film in formaldehyde exhibited much higher photocurrent than that in air. In addition, the sensitivity of Pt-loaded hydrogenated WO3 to formaldehyde reached 15.8 which was nearly 15 times higher than that of the others. Moreover, Pt-loaded hydrogenated WO3 shows excellent electrical response towards formaldehyde in the dark. The intriguing performance of the Pt-loaded hydrogenated WO3 film indicates an efficient coupled effect of oxygen vacancies and Pt. The results provide the potential for improving the efficiency of photoelectric sensing devices by coupling two modification mechanisms. To explain the response characteristics of the four kinds of WO3 films, a schematic diagram of the band bending and spill over model are proposed.
Co-reporter:Qiang Zhu, Changsheng Xie, Huayao Li, Chaoqun Yang, Shunping Zhang and Dawen Zeng
Journal of Materials Chemistry A 2014 vol. 2(Issue 23) pp:4566-4580
Publication Date(Web):07 Mar 2014
DOI:10.1039/C4TC00011K
Energy band engineering is a promising method to tune the photoelectric properties of semiconductors. In this paper, we report an un-element-doped ZnO nanorod array film with a degenerate energy band via annealing in a hydrogen atmosphere. Due to the energy band modification, the photogenerated carrier transitions in the degenerate energy band, involving the valance band, the defect bands and the degenerate conduction band, cause unique photoelectric properties in the degenerate ZnO film. The degenerate ZnO film performs with outstanding conductivity and exhibits an obvious optical absorption in the visible region. Its photoluminescence and photoresponse properties are investigated to understand the fundamentals of photogenerated carrier excitation and recombination in the degenerate ZnO film. Interestingly, the degenerate ZnO film performs with poor photoresponse and has poor photocurrent efficiencies for ultraviolet, blue, and green illuminations, but the photoresponse for near-infrared illumination is attractive. Our results also demonstrate the selectively enhanced down-conversion photoluminescence both at the UV band and at the near-infrared band from the degenerate ZnO film after being excited by an ultraviolet laser source.
Co-reporter:Guozhu Zhang, Changsheng Xie, Shunping Zhang, Jianwei Zhao, Tao Lei, and Dawen Zeng
ACS Combinatorial Science 2014 Volume 16(Issue 9) pp:459
Publication Date(Web):August 4, 2014
DOI:10.1021/co500054r
A combinatorial high-throughput temperature-programmed method to obtain the optimal operating temperature (OOT) of gas sensor materials is demonstrated here for the first time. A material library consisting of SnO2, ZnO, WO3, and In2O3 sensor films was fabricated by screen printing. Temperature-dependent conductivity curves were obtained by scanning this gas sensor library from 300 to 700 K in different atmospheres (dry air, formaldehyde, carbon monoxide, nitrogen dioxide, toluene and ammonia), giving the OOT of each sensor formulation as a function of the carrier and analyte gases. A comparative study of the temperature-programmed method and a conventional method showed good agreement in measured OOT.Keywords: arrays; gas sensor; high-throughput screening; isothermal technique; oxide materials; temperature-dependent conductivity
Co-reporter:Chaoqun Yang, Qiang Zhu, Shunping Zhang, Zhijun Zou, Kuan Tian, Changsheng Xie
Applied Surface Science 2014 Volume 297() pp:116-124
Publication Date(Web):1 April 2014
DOI:10.1016/j.apsusc.2014.01.095
Highlights
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The microstructures in WO3 films were characterized systematically.
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The photocurrent of WO3 under different light sources irradiation is investigated.
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Hydrogen-treated WO3 films show superior infrared photoresponse property.
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The electron trapping effect is proposed to explain the slow decay of photocurrent.
Co-reporter:Xueli Yu, Changsheng Xie, Zhijun Zou, Li Yang, Tao Zou, Guozhu Zhang
Journal of Alloys and Compounds 2014 Volume 584() pp:356-362
Publication Date(Web):25 January 2014
DOI:10.1016/j.jallcom.2013.09.063
•The photocurrent of NiO/TiO2 porous films in methanol is much higher than usual.•A quantitative formula confirms the synergistic effect between the p–n junction and methanol.•A new insight into gas molecule photooxidation on the coupling catalyst is provided.In this work, the NiO/TiO2 porous films with different weight-ratios were prepared by the screen-printing technique. To uncover the roles of gas molecules and the junction on the carrier migration, the photocurrent measurements in methanol were employed. The corresponding experiments were performed in a high-throughput platform where the concentration of target gas and the applied bias voltage were both precisely controlled. Our results revealed that not only the p–n junction but also methanol had a distinct enhancement effect on the photocurrent. Furthermore, the synergistic effect was further confirmed by a quantitative formula of multi-factor effect (ME) based on the carrier density. In addition, a new insight into gas molecule photooxidation on the coupling catalyst was provided, which was of great significance for potential application to photocatalytic degradation and gas sensing.
Co-reporter:Xueli Yu, Changsheng Xie, Li Yang, Shunping Zhang
Sensors and Actuators B: Chemical 2014 195() pp: 439-445
Publication Date(Web):
DOI:10.1016/j.snb.2014.01.070
Co-reporter:Ye Zhao, Shunping Zhang, Guozhu Zhang, Xiaoshuang Deng, Changsheng Xie
Sensors and Actuators B: Chemical 2014 191() pp: 431-437
Publication Date(Web):
DOI:10.1016/j.snb.2013.09.111
Co-reporter:Ya Xiong, Guozhu Zhang, Shunping Zhang, Dawen Zeng, Changsheng Xie
Materials Research Bulletin 2014 52() pp: 56-64
Publication Date(Web):
DOI:10.1016/j.materresbull.2013.12.057
Co-reporter:Guozhu Zhang ; Changsheng Xie ; Shunping Zhang ; Shasha Zhang ;Ya Xiong
The Journal of Physical Chemistry C 2014 Volume 118(Issue 31) pp:18097-18109
Publication Date(Web):July 5, 2014
DOI:10.1021/jp503059e
Cationic interstitial and substitutional defects, which serve as a key role in shaping the material’s performance, are considered as two kinds of important defect structures in the doped SnO2. To give a clear characterization of such metal cation defects, temperature-dependent electrical conduction measurement by the high throughput screening platform of gas-sensing materials is carried out, for the first time, to perform the defect structure studies of the p-type (Li+, Cd2+, Al3+), isovalent (Ti4+), and n-type (Nb5+, W6+) doped SnO2 nanocrystalline films in the oxygen-free atmosphere. The temperature-dependent measurements indicate that subtle induced impurities are capable of evidently modifying the electrical conduction mechanism of the SnO2. In terms of the small-polaron hopping mechanism, an improved defect chemical model is proposed in which the properties of the metal cation defects are explicitly depicted. Values for the ionization energy (ΔED) of the metal cation defects and electron hopping energy (EH) in the doped SnO2 are extracted by fitting the experimental data to the defect model. These data that reflect the nature of the metal cation defects and their effects on the electronic structure of the SnO2 are first introduced here, and the validity of these data are confirmed. What’s more, the ΔED calculated here is of critical importance for understanding the defect structure of the metal dopants in the SnO2.
Co-reporter:Jinjin Wu, Dawen Zeng, Xiaoxia Wang, Lei Zeng, Qingwu Huang, Gen Tang, and Changsheng Xie
Langmuir 2014 Volume 30(Issue 37) pp:11183-11189
Publication Date(Web):2017-2-22
DOI:10.1021/la5017559
The formation mechanism of SnO2 nanotubes (NTs) fabricated by generic electrospinning and calcining was revealed by systematically investigating the structural evolution of calcined fibers, product composition, and released volatile byproducts. The structural evolution of the fibers proceeded sequentially from dense fiber to wire-in-tube to nanotube. This remarkable structural evolution indicated a disparate thermal decomposition of poly(vinylpyrrolidone) (PVP) in the interior and the surface of the fibers. PVP on the surface of the outer fibers decomposed completely at a lower temperature (<340 °C), due to exposure to oxygen, and SnO2 crystallized and formed a shell on the fiber. Interior PVP of the fiber was prone to loss of side substituents due to the oxygen-deficient decomposition, leaving only the carbon main chain. The rest of the Sn crystallized when the pores formed resulting from the aggregation of SnO2 nanocrystals in the shell. The residual carbon chain did not decompose completely at temperatures less than 550 °C. We proposed a PVP-assisted Ostwald ripening mechanism for the formation of SnO2 NTs. This work directs the fabrication of diverse nanostructure metal oxide by generic electrospinning method.
Co-reporter:Qiang Zhu, Changsheng Xie, Huayao Li, Chaoqun Yang, Dawen Zeng
Nano Energy 2014 Volume 9() pp:252-263
Publication Date(Web):October 2014
DOI:10.1016/j.nanoen.2014.08.002
•A capacitor and a photodetector were integrated by an ultra-thin film.•The sulfated TiO2 film offers multifunctionality in the self-powered photodetector.•The entire device is planar, transparent, and in all solid state.•The sulfated TiO2 film performs the excellent capacitive and photoelectric features.•The protonation/deprotonation determines the charge/discharge process of the film.Recently, much effort has been dedicated to achieve integrated nanodevices with energy storage capability in order to meet the demands of multifunctional electronics. Here we demonstrate the concept based on a sulfated TiO2 film that integrates a transparent all-solid-state capacitor and a self-powered photodetector simultaneously for the first time. The sulfated TiO2 film shows a high capacitance of 140 F/cm3, and offers a bifunctionality of the active material and the electrolyte that broadens the operating voltage to 2.3 V. Especially, the film can be charged via a pulsed voltage; then it performs with high responsivity and shows very fast response to UV light without any external bias voltage. Besides, the protonation/deprotonation in the sulfated TiO2 has been also proposed to enhance the excellent charge storage and the photoresponse properties of the film.
Co-reporter:Qingwu Huang, Shouqin Tian, Dawen Zeng, Xiaoxia Wang, Wulin Song, Yingying Li, Wei Xiao, and Changsheng Xie
ACS Catalysis 2013 Volume 3(Issue 7) pp:1477
Publication Date(Web):May 22, 2013
DOI:10.1021/cs400080w
Recently, graphene-based semiconductor photocatalysts have attracted more attention because of their enhanced photocatalytic activity caused by interfacial charge transfer (IFCT). However, the effect of a chemical bond is rarely involved for the IFCT. In this work, TiO2/graphene composites with a chemically bonded interface were prepared by a facile solvothermal method using tetrabutyl orthotitanate (TBOT) as the Ti source. The chemically bonded TiO2/graphene composites effectively enhanced their photocatalytic activity in photodegradation of formaldehyde in air, and the graphene content exhibited an obvious influence on the photocatalytic activity. The prepared composite with 2.5 wt % graphene (G2.5-TiO2) showed the highest photocatalytic activity, exceeding that of Degussa P25, as-prepared pure TiO2 nanoparticles, and the mechanically mixed TiO2/graphene (2.5 wt %) composite by a factor of 1.5, 2.6, and 2.3, respectively. The enhancement in the photocatalytic activity was attributed to the synergetic effect between graphene and TiO2 nanoparticles. Other than the graphene as an excellent electron acceptor and transporter, the enhanced photocatalytic activity was caused by IFCT through a C–Ti bond, which markedly decreased the recombination of electron–hole pairs and increased the number of holes participating in the photooxidation process, confirmed by XPS analysis, the gaseous phase transient photocurrent response, electrochemical impedance spectroscopy, and photoluminescence spectra. This work about effective IFCT through a chemically bonded interface can provide new insights for directing the design of new heterogeneous photocatalysts, which can be applied in environmental protection, water splitting, and photoelectrochemical conversion.Keywords: chemical bonding; C−Ti bond; gaseous phase photocurrent; interfacial charge transfer; photocatalytic activity
Co-reporter:Shouqin Tian, Xiaohu Ding, Dawen Zeng, Jinjin Wu, Shunping Zhang and Changsheng Xie
RSC Advances 2013 vol. 3(Issue 29) pp:11823-11831
Publication Date(Web):23 Apr 2013
DOI:10.1039/C3RA40567B
The permissible limitation of formaldehyde (HCHO) is 80 ppb in an indoor environment. Hence, the rapid real-time monitoring of trace HCHO is urgent and faced as a great challenge by gas sensors based on semiconducting metal oxides. To enhance the HCHO sensing performance of gas sensors, mesoporous SnO2 fibers are used to fabricate a bare SnO2 sensor and then the sensor is functionalized with Pd nanodots by a facile dipping–annealing process. The obtained Pd-functionalized SnO2 sensor exhibits a very high response to HCHO, ultralow detection limit (50 ppb), excellent sensor selectivity over other reducing gases, and short response and recovery time to 100 ppb HCHO (53 s and 103 s, respectively) at a low working temperature of 190 °C. Herein, the Pd nanodots loaded onto SnO2 fibers serve as sensitizers or promoters, increasing the amount of adsorbates as well as molecule–ion conversion rate and simultaneously providing a new catalytic oxidization pathway of HCHO (HCHO → [CH2O]n (POM) → HCOOH → CO2 + H2O) accompanied with a promotion in the electron transfer rate, and thus improving HCHO sensing performance. The combination of the SnO2 mesoporous structure and catalytic activity of the Pd nanodots loaded could give us a very attractive sensing behavior for applications as real-time monitoring gas sensors with rapid response speed.
Co-reporter:Li Yang, Shunping Zhang, Guozhu Zhang, Shasha Zhang, Huayao Li, Changsheng Xie
Sensors and Actuators B: Chemical 2013 Volume 182() pp:239-249
Publication Date(Web):June 2013
DOI:10.1016/j.snb.2013.03.013
The perspective focuses on two easily neglected phenomena: the non-linear I–V and chair-type I–t curves, by modulating the external fields (such as the operating temperature, the category of testing gas and the bias voltage). I–V curves were obtained when the sensor exposed to the methanol and ethanol at a range from 150 to 400 °C. The results show that the non-linear I–V curve appears only the sensor exposed to ethanol at the operating temperature of 300 °C, while the linear I–V curves were obtained when the sensor was operated under all other selected measuring conditions. To further study the above mentioned critical phenomenon at 300 °C, I–t curves were measured at 250–350 °C. Interestingly, both I–V and I–t experimental results display good corresponding relation: the non-linear I–V and chair-type I–t characteristics always occur at the same measuring condition. At the mechanistic level, we presented a coupling induced framework and also believed that the selective effect of segregated trapping levels was dominant responsible for these special environmental responses. The mechanism framework was verified indirectly via in situ DRIFTS technology.
Co-reporter:Li Yang, Shunping Zhang, Huayao Li, Guozhu Zhang, Chengyong Zhan, Changsheng Xie
Sensors and Actuators B: Chemical 2013 176() pp: 217-224
Publication Date(Web):
DOI:10.1016/j.snb.2012.09.008
Co-reporter:Kuan Tian, Changsheng Xie, Xianping Xia
Colloids and Surfaces B: Biointerfaces 2013 Volume 109() pp:82-89
Publication Date(Web):1 September 2013
DOI:10.1016/j.colsurfb.2013.03.036
•Chitosan/alginate multilayer film contained indomethacin is assembled as delivery system.•This drug delivery system exhibits controlled indomethacin release performance.•This multilayer film could eliminate the initial burst release of cupric ion.•This medicated device may be useful to diminish side effects existed in a Cu-IUD.To reduce such side effects as pain and bleeding caused by copper-containing intrauterine device (Cu-IUD), a novel medicated intrauterine device, which is coated with an indomethacin (IDM) delivery system on the surface of copper/low-density polyethylene (Cu/LDPE) composite intrauterine device, has been proposed and developed in the present work. The IDM delivery system is a polyelectrolyte multilayer film, which is composed of IDM containing chitosan and alginate layer by layer, is prepared by using self-assembled polyelectrolyte multilayer method, and the number of the layers of this IDM containing chitosan/alginate multilayer film can be tailored by controlling the cyclic repetition of the deposition process. After the IDM containing chitosan/alginate multilayer film is obtained on the surface of Cu/LDPE composite intrauterine device, its release behavior of both IDM and cupric ion has been studied in vitro. The results show that the release duration of IDM increase with the increasing of thickness of the IDM containing chitosan/alginate multilayer film, and the initial burst release of cupric ion cannot be found in this novel medicated Cu/LDPE composite IUD. These results can be applied to guide the design of novel medicated Cu-IUD with minimal side effects for the future clinical use.
Co-reporter:Qicheng Yang, Huayao Li, Changsheng Xie, Qiang Zhu
Applied Surface Science 2012 Volume 263() pp:465-470
Publication Date(Web):15 December 2012
DOI:10.1016/j.apsusc.2012.09.083
Abstract
In order to study the ZnO photoresponse mechanism, a platform that can perform the photocurrent spectrum measurement has been designed. By using our platform, the photocurrent spectrum of porous ZnO film sensitized by metal chloride solutions was obtained. We used the screen printing technique to fabricate the material chip. The measurements were performed in dry air (relative humidity 15%) and at room temperature. We observed two peaks in the photocurrent spectrum. The peak at 380 nm is assigned to the exciton transition. The shoulder peak at 480 nm is owed to surface states introduced by sensitization and we find VZn plays an important role on this phenomenon. A model is proposed to explain the phenomenon. Furthermore, it is suggested that our platform is a useful tool for photoresponse research and can offer an effective guidance for further investment of light activated gas sensors.
Co-reporter:Shasha Zhang, Changsheng Xie, Zhijun Zou, Li Yang, Huayao Li, and Shunping Zhang
The Journal of Physical Chemistry C 2012 Volume 116(Issue 37) pp:19673-19681
Publication Date(Web):August 29, 2012
DOI:10.1021/jp305898a
We propose a gas-sensitized porous nanocrystalline TiO2 film with a potential application in photovoltaic devices and report about the systematic photoconductivity study of it. The quantitative results show that the gas-sensitized TiO2 film in formaldehyde atmosphere exhibits much higher photoconductivity (3–4 orders of magnitude) and longer carrier lifetime than usual. The intriguing performance of the gas-sensitized TiO2 film indicates the distinct charge carrier transport kinetic courses, whose contributions to the photoconductivity are shown in a designed flowchart. From the flowchart, it is clearly found that two electron loss processes, recombination and electron scavenging, are suppressed for the gas-sensitized TiO2 film in formaldehyde gas, leading to large improvements of photoconductivity and carrier lifetime. The results provide the potential of improving efficiency of photovoltaic devices, and measuring photoconductivity under target gas appears to be a useful tool for research on photocatalytic and photoelectrical processes.
Co-reporter:Zikui Bai, Changsheng Xie, Shunping Zhang, Weilin Xu, Jie Xu
Materials Science and Engineering: B 2011 Volume 176(Issue 2) pp:181-186
Publication Date(Web):15 February 2011
DOI:10.1016/j.mseb.2010.11.005
Thick film gas sensors based on ZnO nanopowders were fabricated by using microwave sintering. The surface and cross section morphologies were characterized by field-emission scanning electron microscopy (FE-SEM). The stability of the microstructure was studied by impedance spectroscopy. The results showed that the shape of the nanoparticles was not changed through microwave sintering, and the thick films had the more dense microstructures than that by muffle oven sintering. The resistance–temperature characteristic and the responses to toluene, methanol and formaldehyde revealed that the microwave sintering technique could effectively control the growth of ZnO nanoparticles, realize the uniform sintering of thick film, gain the stable microstructure and improve the response of sensor. In addition, the formative mechanism of the thick film microstructure was proposed according to microwave sintering mechanism.
Co-reporter:Can Li, Shunping Zhang, Mulin Hu, Changsheng Xie
Sensors and Actuators B: Chemical 2011 Volume 153(Issue 2) pp:415-420
Publication Date(Web):20 April 2011
DOI:10.1016/j.snb.2010.11.008
A new coplanar gas sensor array of ZnO was fabricated by injecting different volumes of 0.01 mol/L AlCl3, CuCl2, SnCl4, TiCl4, PdCl2 and WCl6 solutions and post treatment to improve the selectivity in liquor. The new four-sensor array was optimized by maximizing Sum of Euclidean distances (SED) of the gases of liquor. The morphology of films was characterized by field-emission scanning electron microscopy (FESEM). The results showed that ZnO nanostructures were formed on the surface of films after the injecting process. Nanowires, 100 nm in diameter and 3 μm in length, were found when the solutions included AlCl3, CuCl2, SnCl4 and PdCl2. However, when the injecting solution was TiCl4, nanotowers with 500 nm in diameter and 4 μm in length appeared. No new structures appeared when the WCl6 solution was injected. The results of testing gases of liquor revealed that the injecting process could improve the response of the sensors array effectively. Through calculating the value of the SED, the best array was confirmed whose SED value would be three times the worst one.
Co-reporter:Aihua Yan, Changsheng Xie, Dawen Zeng, Shuizhou Cai, Huayao Li
Journal of Alloys and Compounds 2010 Volume 495(Issue 1) pp:88-92
Publication Date(Web):9 April 2010
DOI:10.1016/j.jallcom.2010.01.092
Three-dimensional WO3 nanowall was successfully synthesized by a facile solvothermal approach in the solution of F127 template. The effect of solvent on tailoring morphology was investigated in detail. The results show that the products with a diameter of 1–3 μm are actually a kind of nanowall structure, which is composed of high-density nanosheets with about 30 nm in thickness. A possible formation mechanism is proposed here. Sensing properties show that the sensitivity of the three-dimensional WO3 sensor is obviously higher than that of commercial WO3 sensor. UV illumination on three-dimensional WO3 sensor could greatly improve the response because of the formation of defects.
Co-reporter:Zhijun Zou, Yuan Liu, Huayao Li, Yichuan Liao and Changsheng Xie
ACS Combinatorial Science 2010 Volume 12(Issue 3) pp:363
Publication Date(Web):March 12, 2010
DOI:10.1021/cc1000117
On the basis of the idea of equilateral ingredient triangle, a material library of the TiO2/WO3/MnO2 composite material system was designed, which consisted of 66 ingredient points. Each point in the library corresponded with a device. To fabricate the device, the technology of screen printing was used. The pastes which were suitable for this technology were prepared by ball milling. After we printed the pastes onto the alumina substrate which had been preprinted with Au interdigital electrodes, these printed samples were sintered at 550 °C for 2 h in air. The photocurrent of each device under different light sources was measured respectively using a high-throughput screening system. The largest photocurrent was observed when the mole ratio of TiO2/WO3 was 2/8 in the composite system. X-ray diffraction (XRD) was used to investigate the phase structure of the powder which had excellent photoelectric response.
Co-reporter:Yichuan Liao, Huayao Li, Yuan Liu, Zhijun Zou, Dawen Zeng, and Changsheng Xie
ACS Combinatorial Science 2010 Volume 12(Issue 6) pp:883
Publication Date(Web):September 21, 2010
DOI:10.1021/cc100121d
On the basis of combinatorial methodology and the idea of an equilateral ingredient triangle, the TiO2/ZnO/Fe2O3 composite system including 66 ingredient points was designed. The photocurrents under different light sources and bias voltages were measured, and the photocurrent amplitude at 300 s was chosen as a parameter to evaluate the photoelectric response of the composite. To appraise the composition effect of the composite compared with pure materials, the quantitative formula of the composition effect has been provided for the first time in this paper. We found that not all the ingredient points demonstrated the enhanced composition effect in the as-designed ingredient triangle material library. The reasons of different composition effect for different ingredient points have been discussed in detail. X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM) were used to investigate the phase structure and the grain morphology of the composite.
Co-reporter:Aihua Yan, Changsheng Xie, Dawen Zeng, Shuizhou Cai, Mulin Hu
Materials Research Bulletin 2010 45(10) pp: 1541-1547
Publication Date(Web):
DOI:10.1016/j.materresbull.2010.05.026
Co-reporter:Changsheng Xie, Liqi Xiao, Mulin Hu, Zikui Bai, Xianping Xia, Dawen Zeng
Sensors and Actuators B: Chemical 2010 Volume 145(Issue 1) pp:457-463
Publication Date(Web):4 March 2010
DOI:10.1016/j.snb.2009.12.052
Nanostructured flat-type coplanar gas sensor arrays of ZnO with different MnO2 additive concentration were fabricated by a combination of screen-printing technology and solution growth process. The morphologies and crystal structures were characterized by X-ray diffraction (XRD) and field-emission scanning electron microscopy (FESEM). The results showed that ZnO nanostructures were induced on the surface of gas sensor arrays through the solution growth process. The nanostructures were composed of nanowalls and nanosheets with the thickness of about 50–200 nm and length of about 1–2 μm. The resistance–temperature characteristic and the response to formaldehyde revealed that the solution growth process could effectively control the morphologies, change the aspect ratio of ZnO nanostructures and significantly improve the response of gas sensor arrays. In addition, the response to formaldehyde of ZnO sensors with 0.5 wt% and 1.0 wt% MnO2 additive was higher than that of pure ZnO sensor.
Co-reporter:Zikui Bai, Changsheng Xie, Shunping Zhang, Liuxian Zhang, Qinyi Zhang, Weilin Xu, Jie Xu
Sensors and Actuators B: Chemical 2010 Volume 151(Issue 1) pp:107-113
Publication Date(Web):26 November 2010
DOI:10.1016/j.snb.2010.09.039
Nanostructured films of tetrapod-shaped ZnO (T-ZnO) were fabricated by a combination of screen-printing technology and hydrothermal treatment process. The morphologies and crystal structures of the films were characterized by X-ray diffraction (XRD) and field-emission scanning electron microscopy (FESEM). The stability was analyzed by impedance spectroscopy. The results showed that ZnO nanostructures were induced on the surface of the films through the hydrothermal treatment process. The nanostructures were composed of nanowalls with thickness of about 15 nm. The resistance–temperature characteristic and the response to VOCs (benzene, toluene, methanol and ethanol) revealed that the hydrothermal treatment process could effectively control the surface morphologies and microstructures of the films, keep the nanocharacteristic of the films, enhance the response of the sensors and improve the stability of the sensors.
Co-reporter:Shunping Zhang, Changsheng Xie, Zikui Bai, Mulin Hu, Huayao Li, Dawen Zeng
Food Chemistry 2009 Volume 113(Issue 4) pp:1346-1350
Publication Date(Web):15 April 2009
DOI:10.1016/j.foodchem.2008.08.090
The seafood dipped with formaldehyde to prevent from spoiling by dishonest mongers is a big danger to the physical health of consumer. An E-nose with six TGS gas sensors was used for spoiling and formaldehyde-containing detection of seafood in this paper. Two static features R0 (resistance in the air), S (sensor response), and one dynamic feature DR (desorption rate) were extracted. Fresh octopus samples dipped in water solutions with different formaldehyde concentrations were measured. In these measurements, the stability of sensors and features was evaluated and compared. The mean relative errors of these three features were 23.6%, 19.7%, and 4.1%, respectively. The results showed that the dynamic feature was more stable. With principal component analysis, the spoilage of seafood could be easily detected. And the correct recognition rate of different octopus samples was 93.1%. The results showed that electronic nose analysis could be an efficient method for seafood quality assessment.
Co-reporter:Shunping Zhang, Changsheng Xie, Dawen Zeng, Huayao Li, Yuan Liu, Shuizhou Cai
Sensors and Actuators B: Chemical 2009 Volume 142(Issue 1) pp:243-252
Publication Date(Web):12 October 2009
DOI:10.1016/j.snb.2009.08.015
Sensor array configuration needs to be optimized in developing an application-specific instrument of electronic noses. Currently, sensor array optimization is commonly done by feature selection techniques. These methods could solve how to optimize a sensor array. However, they could not figure out what are the unique functions that each sensor plays in the optimized sensor array. The method proposed in this paper could solve this problem by sensor clustering and dividing the whole sample classification mission into several small recognition tasks. A measurement with a six Taguchi Gas Sensors (TGS sensor hereinafter) sensors array to classify 11 gas sorts was used in the data validation. The sensor array was optimized to three sensors with the proposed method. Each sensor in the optimized array had unique functions to solve different recognition tasks. TGS2600 had the unique functions to discriminate butanone and acetaldehyde. TGS2602 had the unique functions to discriminate benzene and cyclohexane, methanol and ethanol. TGS813 had the unique functions to discriminate cyclohexane and pentane. The combination of TGS2600 and TGS2602 had the unique functions to discriminate acetone and butanone, acetone and acetaldehyde. The proposed method might be a new generation of sensor array optimization methods.
Co-reporter:Shunping Zhang, Changsheng Xie, Huayao Li, Zikui Bai, Xianping Xia, Dawen Zeng
Sensors and Actuators B: Chemical 2009 Volume 135(Issue 2) pp:552-559
Publication Date(Web):15 January 2009
DOI:10.1016/j.snb.2008.10.021
The metal oxide (MOX) gas sensors have distinct response patterns with different gas sorts. In this paper, a reaction model of MOX gas sensors is represented to simulate the sensor response patterns. Six model parameters of each sensor responding to each gas sort could be calculated out in the sensor response pattern simulations. The sensor response curves also could be reconstructed by the model with the six parameters. In this way, a performance database of sensors could be built with these model parameters. A pattern matching method based on the sensor performance database was also proposed for gas sort classification without any usual pattern recognition methods. Eleven volatile organic compounds (VOCs) were measured by a gas sensor array of 6 TGS gas sensors for model validation. The mean simulation error of all sensors was 3.98%. The performance database of these sensors was well built by model calculation. The correct recognition ratio of the pattern matching method was 100%. The results indicated that the proposed reaction model might have many advantages in real applications. The work in this paper is a step towards a general applicable model for MOX gas sensors.
Co-reporter:Zhihong Yang, Changsheng Xie, Hua Xiang, Jinqing Feng, Xianping Xia, Shuizhou Cai
Colloids and Surfaces B: Biointerfaces 2009 Volume 69(Issue 2) pp:276-280
Publication Date(Web):1 March 2009
DOI:10.1016/j.colsurfb.2008.11.027
Copper/indomethacin/low-density polyethylene (Cu/IDM/LDPE) nanocomposite was prepared as a novel material for intra-uterine device (IUD). IDM release profile of the nanocomposite was investigated by using spectrophotometer. The results show that IDM release rate of Cu/IDM/LDPE nanocomposite is higher in simulated uterine solution than that in methanol, confirming that the release process of IDM is dominated mainly by pore diffusion. The decrease in copper particle size and the increase in copper mass content all accelerate IDM release, indicating that IDM release rate can be adjusted by changing copper loading or copper particle size. The surface of the incubated nanocomposite was characterized by X-ray diffraction, scanning electron microscopy and energy dispersive X-ray microanalysis. A few deposits composed of P, Cl, Ca, Cu and O were observed on the nanocomposite surface, which may be related to the presence of IDM particles with large particle size.
Co-reporter:Huihu Wang, Changsheng Xie
Journal of Physics and Chemistry of Solids 2008 Volume 69(Issue 10) pp:2440-2444
Publication Date(Web):October 2008
DOI:10.1016/j.jpcs.2008.04.036
Colloidal ZnO nanoparticles were prepared in ethanol solutions and annealed at different temperatures (150–500 °C) subsequently. The size, morphology and surface characteristics of ZnO nanoparticles were examined by TEM, XRD, UV–vis absorption spectrum and FTIR technique. With the increase of annealing temperature, the mean size of ZnO nanoparticles was increased from 10 to 90 nm, while the bonding structure of acetate groups coordinating with zinc ions evolved from unidentate to bidentate type. The UV-induced degradation results of methyl orange verified that the photocatalytic process of colloidal ZnO nanoparticles without annealing and the sample annealed at 150 °C was unstable for the weakly bonding unidentate type of acetate groups. However, the sample annealed above 150 °C demonstrated their photocatalytic stability in the whole catalytic process for the stable bidentate bonding type of acetate groups. In addition, the change of particle size in the annealing process significantly affected the catalytic activity of photocatalysts. ZnO nanoparticles annealed at 300 °C would be a prospective photocatalysts with a high catalytic activity and stability compared with the other samples.
Co-reporter:Chunqiao Ge, Zikui Bai, Mulin Hu, Dawen Zeng, Shuizhou Cai, Changsheng Xie
Materials Letters 2008 Volume 62(Issue 15) pp:2307-2310
Publication Date(Web):31 May 2008
DOI:10.1016/j.matlet.2007.11.073
ZnO nanorod-bundle thin films have been synthesized by a simple self-assembly method with the aid of F127 (EO106–PO70–EO106) triblock copolymer. Their morphologies and crystal structures were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM). SEM results showed that films were composed of a lot of bundles, which comprised nanorods with the diameter of about 10 nm. The possible formation mechanism of ZnO nanorod-bundle structures is proposed. Gas-sensing property of thin films, to alcohol, was also detected. It was also found that the sensitivity, to 100 ppm alcohol, of ZnO nanorod-bundle thin films was higher than that of ZnO nanoparticle thin films. The results showed that the triblock copolymer, served as the surfactants, could effectively control the morphologies and the aspect ratio of nano-ZnO, and then improve its gas-sensing property.
Co-reporter:Zikui Bai, Changsheng Xie, Mulin Hu, Shunping Zhang
Physica E: Low-dimensional Systems and Nanostructures 2008 Volume 41(Issue 2) pp:235-239
Publication Date(Web):December 2008
DOI:10.1016/j.physe.2008.07.019
The sensors based on Ni-doped ZnO nanopowder with tetrapod-shape (T-ZnO) were fabricated by screen-printing technique with external magnetic field in different direction. The morphologies and crystal structures of the thick film were characterized by X-ray diffraction (XRD) and field-emission scanning electron microscopy (FE-SEM), respectively. Gas-sensing property of sensors responded to 100 ppm formaldehyde was also detected. The results show that the direction of magnetic field has crucial effect on the sensor sensitivity. The sensors based on 5 wt% Ni-doped T-ZnO induced by magnetic field in parallel direction to the thick film surface, has the optimization sensitivity, the shortest response and recovery time, which are 10.6, 16 and 15 s, respectively. The magnetic-field induction model and the gas-sensing mechanism of the Ni-doped T-ZnO are proposed.
Co-reporter:Huihu Wang, Changsheng Xie
Physica E: Low-dimensional Systems and Nanostructures 2008 Volume 40(Issue 8) pp:2724-2729
Publication Date(Web):June 2008
DOI:10.1016/j.physe.2007.12.012
The effects of oxygen partial pressure on the microstructures and photocatalytic activity of ZnO nanoparticles prepared by evaporation–condensation method in a flow of Ar and O2 have been studied by field-emission scanning electron microscopy (FESEM), XRD, XSM800 photoelectron spectrometer (XPS) and UV–Vis spectrometer. The size and shape of ZnO nanoparticles prepared at the oxygen partial pressure (700–800 Pa) show slight difference from that prepared at the oxygen partial pressure ranging from 1500 to 2300 Pa. However, the relative percentage of surface oxygen vacancies decreases from 40.6% (prepared at 700–800 Pa) to 29.3% (2200–2300 Pa) in the condition of similar ratio of Zn atoms to total oxygen species by the qualitative calculation of XPS data. ZnO nanoparticles were examined as photocatalysts for the UV-induced degradation of methyl orange in water solution. The photodegradation results directly demonstrate that the oxygen partial pressure influences the photoactivity of ZnO nanoparticles greatly.
Co-reporter:Zikui Bai, Changsheng Xie, Mulin Hu, Shunping Zhang, Dawen Zeng
Materials Science and Engineering: B 2008 Volume 149(Issue 1) pp:12-17
Publication Date(Web):15 March 2008
DOI:10.1016/j.mseb.2007.11.020
The testing chamber humidity and the storage circumstance humidity effects on the tetrapod-shaped ZnO nanopowder (named as T-ZnO) thick film sensors were investigated by measuring the resistance and sensitivity. The resistance increases gradually with increasing relative humidity (RH) in a range of 32%–75% RH in testing chamber, while in a range of 75%–96% RH, decreases gradually with the increase of RH. The sensitivity to ethanol 100 ppm in testing chambers with different humidity is in the order of 50% RH > of 75% RH > of 32% RH > of 96% RH. The sensitivity change in the storage circumstance with different RH is similar to the change in testing chamber with different RH. The stability of T-ZnO sensor is influenced evidently by the storage circumstance humidity. The water vapour in the tetrapod-shaped ZnO nanopowders was investigated by thermogravimetric analysis (TGA). The testing gas and the reactant adsorbed in the sensitive film were characterized by infrared spectrum (IR). The explanation of the observed effects was given and the mechanism of interaction of the ZnO sensing layer with H2O was proposed.
Co-reporter:Shunping Zhang, Changsheng Xie, Mulin Hu, Huayao Li, Zikui Bai, Dawen Zeng
Sensors and Actuators B: Chemical 2008 Volume 132(Issue 1) pp:81-89
Publication Date(Web):28 May 2008
DOI:10.1016/j.snb.2008.01.015
A phase space entire (PSE) feature extraction method for metal oxide gas sensors was proposed in this paper. This method extracts six features from the response curve in phase space. The difference from other feature extraction methods such as extracting phase space integral (PSI), which also use phase space, is that the sensor response curves could be completely described and well reconstructed with the six features by a sensory response feedback process. The proposed method PSE was compared with the PSI extracting method and a common signal maximum (SM) extracting method in a dataset. The dataset was consisted of 264 measurements of 11 volatile organic compounds (VOCs) of four concentrations by six TGS gas sensors. The six features were first extracted from each response curve of all samples, and then all response curves were reconstructed by the six features. The mean sensory response feedback error of the reconstructed response curves from the original signal response curves was 5.4%, which indicated that PSE could extract the entire signal of response curves. Meanwhile, Fisher discriminant analysis (FDA) was used in the comparison of the three feature extraction methods. The correct recognition rates of FDA with SM, PSI and PSE were 90.9%, 81.1% and 100%, respectively. The results show that PSE is an efficient entire feature extraction method.
Co-reporter:Zhihong Yang;Xianping Xia
Journal of Materials Science: Materials in Medicine 2008 Volume 19( Issue 11) pp:3319-3326
Publication Date(Web):2008 November
DOI:10.1007/s10856-008-3467-5
To decrease the side effects of the existing copper-bearing intrauterine devices, the zinc/low-density polyethylene (Zn/LDPE) nanocomposite and zinc-oxide/low-density polyethylene (ZnO/LDPE) nanocomposite have been developed in our research for intrauterine devices (IUDs). In this study, the influences of preparation methods of nanocomposites and particle sizes of zinc and zinc oxide on Zn2+ release from composites incubated in simulated uterine solution were investigated. All release profiles are biphasic: an initial rapid release phase is followed by a near zero-order release period. Zn2+ release rates of nanocomposites prepared by compressing moulding are higher than those of the nanocomposites prepared by hot-melt extrusing. Compared with Zn2+ release from the microcomposites, the release profiles of the nanocomposites exhibit a sharp decrease in Zn2+ release rate in the first 18 days, an early onset of the zero-order release period and a high release rate of Zn2+ at the later stage. The microstructure of the Zn/LDPE sample and the ZnO/LDPE sample after being incubated for 200 days was characterized by SEM, XRD and EDX techniques. The results show that the dissolution depth of ZnO/LDPE nanocomposite is about 60 μm. Lots of pores were formed on the surface of the Zn/LDPE sample and ZnO/LDPE sample, indicating that these pores can provide channels for the dissolution of nanoparticles in the matrix. The undesirable deposits that are composed of ZnO are only detected on the surface of Zn/LDPE nanocomposite, which may increase the risk of side effects associated with IUDs. It can be expected that ZnO/LDPE nanocomposite is more suitable for IUDs than Zn/LDPE nanocomposite.
Co-reporter:Feng Wen, Changsheng Xie, Xianping Xia, Guomin Le
Journal of Electroanalytical Chemistry 2007 Volume 603(Issue 2) pp:219-226
Publication Date(Web):15 May 2007
DOI:10.1016/j.jelechem.2007.02.009
The corrosion characteristics of five copper/low-density polyethylene (Cu/LDPE) microcomposite in the simulated uterine solution have been studied by the electrochemical measurements, XRD and FESEM. The critical threshold (composition from which the material changes from insulator to electrical conductor) of the Cu/LDPE microcomposite is between 50 wt.% and 60 wt.% copper microparticles’ loading. Five microcomposites have similar corrosion mechanism in the course of corrosion in simulated uterine solution. The intermediate products of them are mainly Cu2O. When corrosion of the microcomposite reaches stable, Cu2+ generated within composite disperses through solution path to penetrate to simulated uterine solution outside the microcomposite, and corrosion rate rises as the copper content in composite increases. Compared with the microcomposite with high copper content, the microcomposite with low copper content have high copper transformation ratio, almost no sediments and hardly possible passivation characteristic, but its corrosive rate is slower than the former. This paper also compared the corrosion behaviour of the composite and bulk copper in the simulated uterine solution; there were more insoluble subproducts in the corrosion process of bulk copper than the composite. The Cu/LDPE microcomposite is favorable to use as the novel material of intrauterine device, and the copper content in composite should be reduced as greatly as possible if only contraception requirement can be sufficient.
Co-reporter:Chunqiao Ge, Changsheng Xie, Mulin Hu, Yanghai Gui, Zikui Bai, Dawen Zeng
Materials Science and Engineering: B 2007 Volume 141(1–2) pp:43-48
Publication Date(Web):25 June 2007
DOI:10.1016/j.mseb.2007.05.008
La-doped ZnO nanoparticles were synthesized by sol–gel method starting from zinc acetate dihydrate, lanthanum sesquioxide, alcohol and nitric acid. The crystal structure and morphology of the nanoparticles were characterized by XRD, FESEM, respectively. The thermal decomposition behavior of the the ZnO-based xerogel was detected by TG-DSC. The results show that as-prepared nanoparticles with the hexagonal wurtzite contain the adsorbed water and some organic compounds below 300 °C, which is the key to the calcinations of the ZnO-based xerogel. Pure ZnO and La-doped ZnO thick film sensors were prepared and tested for specific sensitivity to alcohol and benzene with (and without) UV-light excitation. Among all, 10 at.%La–ZnO-based sensors are significantly sensitive to 100 ppm alcohol and 100 ppm benzene. There is an obvious enhancement of the gas-sensing performances with UV-light excitation. That is, the sensitivity to 100 ppm benzene rises twice. The observed sensitivity to alcohol and benzene could be explained with the surface adsorption theory and the conduction-band theory.
Co-reporter:Shuizhou Cai;Xianping Xia;Changhong Zhu
Journal of Biomedical Materials Research Part B: Applied Biomaterials 2007 Volume 80B(Issue 1) pp:220-225
Publication Date(Web):12 JUL 2006
DOI:10.1002/jbm.b.30587
The Cu2+ release rate of novel copper/low-density polyethylene composites as an intrauterine device material in the simulated uterine solution was investigated for 280 days. The corrosion products of these composites were identified by the X-ray diffraction method. The distributions of the copper phase and the cuprous oxide phase at different corrosion depths in the composites were measured by the internal standard method. For comparison, copper particles of two sizes were embedded in a polyethylene matrix to form composites. The average copper particle diameter of the nanocomposite was 30 nm, while that of microcomposite was 52 μm. Mechanism of Cu2+ release controlled by the nanocomposite revealed that many clusters composed of copper nanoparticles, which were observed by the field emission scanning electron microscopy in the nanocomposite, led to the formation of large amounts of Cu2O and consequently facilitated the Cu2+ steady release. A scanning electron microscope with energy dispersive X-ray microanalysis mapping technique (SEM/EDX) was employed to measure the corrosion depth and to calculate the life span of the nanocomposite. The result that the nanocomposite displayed a near zero-order release after a month of incubation indicated that the Cu2+ release behavior controlled by nanocomposite was remarkably superior to that by microcomposite. © 2006 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2007
Co-reporter:Chunqiao Ge, Changsheng Xie, Shuizhou Cai
Materials Science and Engineering: B 2007 Volume 137(1–3) pp:53-58
Publication Date(Web):25 February 2007
DOI:10.1016/j.mseb.2006.10.006
CeO2-doped ZnO thin-film gas sensors with different Ce/Zn ratios have been fabricated by dip-coating method, starting from zinc acetate dihydrate, cerium nitrate hexahydrate (Ce(NO3)3·6H2O) and anhydrous ethanol. Each layer was fired at 180 °C in a conventional oven for 30 min and the final coatings were sintered at 500 °C in a muffle furnace for 60 min. The microstructure and morphology of the films were characterized by XRD and FESEM, respectively. The resistance and sensitivities to volatile organic compounds were investigated on the static testing chamber. The X-ray diffraction (XRD) analysis of the films reveals the appearance of CeO2, tetravalent cerium dioxide whose valency is different from cerium nitrate hexahydrate. The results also show that as-prepared thin films with thickness of about 5 μm are polycrystalline with the structure of hexagonal wurtzite type. They consist of almost spherical particles with size ranging from 40 to 65 nm. Pure ZnO and Ce-doped ZnO thin-film sensors were prepared and tested for specific sensitivity to alcohol, acetone and benzene. It is observed that 1 at.% Ce–ZnO and 5 at.% Ce–ZnO are more sensitive to volatile organic compounds (VOCs), compared with other films with the different dopant concentration. The sensitivity of 5 at.% Ce–ZnO thin-film sensors to 100 ppm alcohol reaches 80 or so at 320 °C. 5 at.% Ce–ZnO thin-film sensors show good selectivity to alcohol, and thus can serve as alcohol-sensing sensors. A new physical model of the CeO2 dopant influence on the gas-sensing properties of ZnO thin films is proposed. The addition of Ce to ZnO modified the particles size distribution, electrical conductivity, the catalytic activity and thus affected gas-sensing property to some extent.
Co-reporter:Xianping Xia, Changsheng Xie, Shuizhou Cai, Zhihong Yang, Xiangliang Yang
Corrosion Science 2006 Volume 48(Issue 12) pp:3924-3932
Publication Date(Web):December 2006
DOI:10.1016/j.corsci.2006.04.007
The corrosion characteristics of copper microparticles and copper nanoparticles in distilled water were investigated in this paper. The Cu2+ transformations of copper microparticles and copper nanoparticles in distilled water were tested by using absorbance measurement, the structures of their corrosion products were determined by using XRD and TEM techniques. The results of absorbance measurement show that the corrosion characteristics of copper nanoparticles in distilled water are quite different from that of copper microparticles. The Cu2+ transformations ratio of copper microparticles increases slowly with the increasing of immersion time and levels off eventually, but the Cu2+ transformations ratio of copper nanoparticles increases sharply with the increasing of immersion time and gets to peak rapidly, and then decreases as the immersion time increases and levels off finally. The results of XRD present that they have different corrosion products, the corrosion products of copper microparticles in distilled water are Cu and CuO, but the nanoparticles are Cu, CuO, Cu(OH,Cl)2 · 2H2O and Cu2(CO3)(OH)2. All these differences owe to the size effect of copper particles.
Co-reporter:Xianping Xia, Shuizhou Cai, Changsheng Xie
Materials Chemistry and Physics 2006 Volume 95(Issue 1) pp:122-129
Publication Date(Web):10 January 2006
DOI:10.1016/j.matchemphys.2005.05.010
Copper/low-density-polyethylene (Cu/LDPE) nanocomposites have been prepared using a melt-blending technique in a single-screw extruder. Their structure and thermal characteristics are characterized by using X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray energy dispersive spectroscopy (EDS), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The results of XRD, SEM and SEM–EDS Cu-mapping show that the nanocomposites are a hybrid of the polymer and the copper nanoparticles, and the copper nanoparticles aggregates were distributed uniformly in general. The results also show that the nanocomposites and the base resin, the pure LDPE, have a different crystalline structure and the same oriented characteristics owing to the presence of copper nanoparticles and the same cooling condition. The results of DSC show that the incorporation of copper nanoparticles can decrease the melting temperatures but increase the crystallization temperatures, and can lower the crystallinity degree of the matrix of the composites. The results of TGA show that the presence of copper nanoparticles can improve the thermal stability of the nanocomposites, a maximum increment of 18 °C is obtained comparing with the pure LDPE in this experiment. The results of TGA also show that the influence of the incorporation of the copper nanoparticles on the thermal stability of the Cu/LDPE nanocomposites is different from that of the non-metal nanoparticles on the polymer/non-metal nanocomposites and the copper microparticles on the Cu/LDPE microcomposites. The increase of the thermal stability of the Cu/LDPE nanocomposites will decrease when the content of the copper nanoparticles is more than 2 wt.%. The difference might be caused by the fact that the activity of the metal nanoparticles is much more higher than that of the non-metal nanoparticles, and the different size effect the different copper particles has.
Co-reporter:Qinyi Zhang, Shunping Zhang, Changsheng Xie, Dawen Zeng, Chaoqun Fan, Dengfeng Li, Zikui Bai
Sensors and Actuators B: Chemical 2006 Volume 119(Issue 2) pp:538-546
Publication Date(Web):7 December 2006
DOI:10.1016/j.snb.2006.01.007
In this paper, 17 commercial Chinese vinegars, acetic acid and 5% diluted acetic acid were analyzed by an electronic nose containing nine nano ZnO thick film gas sensors, which are doped by 5 wt.% and 10 wt.% TiO2, 5 and 10 wt.% MnO2, 1 wt.% V2O5, 5 wt.% Bi2O3, 0.6 and 2.4 wt.% Ag, and 5 wt.% W, respectively. Principal component analysis (PCA) and cluster analysis (CA) were employed to investigate the presence of classes inside the sample population. It was shown that characterizing the Chinese vinegars by the electronic nose was highly related to their type, raw materials, total acidity, fermentation method and production area and all these influencing factors were not independent. The CA results indicated that the type and fermentation method were more effective than the other influencing factors when the vinegars were analyzed by the electronic nose. Finally, the data colleted by the electronic nose were applied to the learning vector quantization (LVQ) neural network performing the role of recognition and classification of the vinegars. The accuracy in terms of predicting tested vinegar measurements was 72.1%, 76.5%, 77.9%, 94.1% and 82.4% according to their type, raw materials, total acidity, fermentation method and production area, respectively. This work was the first step to establish a gas-sensing fingerprint database of Chinese vinegars and develop a commercial electronic nose on the Chinese vinegars quality control.
Co-reporter:Zhihong Yang, Changsheng Xie
Colloids and Surfaces B: Biointerfaces 2006 Volume 47(Issue 2) pp:140-145
Publication Date(Web):1 February 2006
DOI:10.1016/j.colsurfb.2005.12.007
Zn2+ release from Zn and ZnO particles with different sizes in simulated uterine solution were investigated by absorbance measurements. The effects of pH and human serum albumin (HSA) on Zn2+ release were also studied. The morphology of Zn and ZnO particles was observed by scanning electron microscopy, and the corrosion products of zinc nanoparticles were analyzed by XRD. The results indicate that the maximum release ratios of Zn2+ from Zn and ZnO nanoparticles are higher than those from Zn and ZnO microparticles. Zn2+ release ratio depends not only on the pH of the simulated uterine solution but also the presence of human serum albumin. It decreases as the pH of the uterine solution increases. The trends of Zn2+ release ratios are almost the opposite for solutions with and without HSA. XRD analysis results indicate that zinc oxide is the main corrosion product of zinc particles.
Co-reporter:Xianping Xia, Changsheng Xie, Shuizhou Cai, Feng Wen, Changhong Zhu, Xiangliang Yang
Materials Science and Engineering: A 2006 Volume 429(1–2) pp:329-333
Publication Date(Web):15 August 2006
DOI:10.1016/j.msea.2006.05.045
The copper/low-density polyethylene (Cu/LDPE) composites has been developed as a novel intrauterine devices (IUDs) material in our research since the copper-containing IUDs (Cu-IUDs) made of this kind of material can eliminate or lessen the side-effects of the existing Cu-IUDs. In the present study tensile tests were used to characterize the mechanical properties of this novel IUDs material, the Cu/LDPE composites. The influences of the copper particles’ loading, varied from 5 to 25 wt.%, and the copper particles’ size, 50 nm and 5 μm, on the Young's modulus, yield strength, tensile strength and elongation at break were investigated. Increasing the copper particles’ loading caused an increase in Young's modulus for Cu/LDPE nanocomposite but a decrease in Young's modulus for Cu/LDPE microcomposite, a decrease in yield strength for both Cu/LDPE nanocomposite and Cu/LDPE microcomposite except for an increase in yield strength for Cu/LDPE nanocomposite when the copper nanoparticles’ loading is less than 5 wt.%, a decrease in tensile strength and elongation at break for both Cu/LDPE nanocomposite and Cu/LDPE microcomposite. Decreasing the copper particles’ size caused an increase in the Young's modulus, yield strength, tensile strength and elongation at break. These changes are attributed to the different dispersion of the copper particles in matrix and the different interfacial adhesion between the copper particles and the matrix caused by the different loadings and sizes of copper particles. Additionally, after the copper particles inside the Cu/LDPE nanocomposite was corroded completely, its mechanical properties are better than those of the original Cu/LDPE nanocomposite due to the releasing of stress concentration caused by the copper nanoparticles. All these results indicate that the Cu/LDPE nanocomposite is much better to act as a Cu-IUDs material than the Cu/LDPE microcomposite does.
Co-reporter:Xianping Xia;Shuizhou Cai;Junhui Hu
Journal of Biomedical Materials Research Part B: Applied Biomaterials 2006 Volume 79B(Issue 2) pp:345-352
Publication Date(Web):24 APR 2006
DOI:10.1002/jbm.b.30548
Intrauterine devices (IUDs), especially the copper-containing IUDs (Cu-IUDs), are one of the worldwide used forms for birth control, owing to their advantages of long-lasting and high efficacy, economy, safety, and reversibility. However, it is not perfect for the existing Cu-IUDs; some shortcomings related to its side effects have not been overcome yet. For this reason, a new Cu-IUDs material, the copper/low-density polyethylene (Cu/LDPE) nanocomposite, has been developed in our research team. The structure and water uptake characteristics of this new Cu-IUDs material have been investigated by using X-ray diffraction (XRD), Scanning electron microscopy (SEM), X-ray energy dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FT-IR), and gravimetric analysis in this paper. The results of XRD, SEM, EDS, and FT-IR show three important outcomes associated with the structure of the nanocomposite. First, the nanocomposite is hybrid of the polymer and the copper nanoparticles (nano-Cu). Second, porosities, nano-Cu aggregates, and primary alcohol (RCH2OH) are existed in the nanocomposite. Third, the nano-Cu aggregates are distributed uniformly in the polymer matrix in general. The results of Gravimetric analysis, which associated with the water uptake characteristics of the nanocomposite, exhibit that the water absorption behavior of the nanocomposite obeys the classical diffusion theory very well, the water uptake of the nanocomposite increases with the increasing of the nano-Cu loading, and that the water uptake ability of the nanocomposite with 15.0 wt % nano-Cu (50 nm in diameter) is about 150 times larger than that of the base resin and about 45 times higher than that of the Cu/LDPE microcomposite with 15.0 wt % copper microparticles (5 μm in diameter). These water uptake characteristics are mainly attributed to the structure of the Cu/LDPE composites and the size effect of the nano-Cu. © 2006 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2006
Co-reporter:Yanghai Gui, Changsheng Xie
Materials Chemistry and Physics 2005 Volume 93(2–3) pp:539-543
Publication Date(Web):15 October 2005
DOI:10.1016/j.matchemphys.2005.04.006
The present study described a novel method to prepare ZnO nanoneedles and the thermal oxidation behavior of the zinc nanoparticles with and without H2O2 pre-oxidation. Field-emission scanning electron microscopy (FE-SEM), thermogravimetric analysis (TGA)–differential scanning calorimetry (DSC), and XRD were performed to characterize the nanostructures. H2O2 could oxidize a film shell coated on the surface of the zinc core and appropriate coating film shell could supply the source of densest ZnO nanoneedles at the 20 mg ml−1 ratio of the raw powders to H2O2. The growth of nanoneedles is mainly affected by two factors, one the film thickness, the other zinc content in the core. We can control the growth of nanoneedles via simply controlling the H2O2 concentration.
Co-reporter:Xianping Xia, Changsheng Xie, Shuizhou Cai
Thermochimica Acta 2005 Volume 427(1–2) pp:129-135
Publication Date(Web):March 2005
DOI:10.1016/j.tca.2004.09.002
The influences of copper nanoparticles content and cooling rate on non-isothermal crystallization behavior of low-density polyethylene/copper (LDPE/Cu) nanocomposites were investigated. Nanocomposites were prepared by extruding mixtures of pure LDPE and copper nanoparticles using melt-blending method in a single-screw extruder. Differential scanning calorimetry (DSC) was used to analyze their non-isothermal crystallization behavior. The results indicate that both the incorporation of copper nanoparticles and cooling rates influence the crystallization behaviors of the LDPE matrix significantly. Especially, the dependence of the effective activation energy on the relative extent of crystallization implies that the copper nanoparticles dispersed in the nanocomposites may act as a heterogeneous nucleation for the crystallization of the LDPE matrix, and that the presence of the copper nanoparticles may hinder the transport of the molecule chains at the same time, resulting in a decrease of the crystallization growth rate of the LDPE matrix.
Co-reporter:B.L. Zhu, C.S. Xie, W.Y. Wang, K.J. Huang, J.H. Hu
Materials Letters 2004 Volume 58(Issue 5) pp:624-629
Publication Date(Web):February 2004
DOI:10.1016/S0167-577X(03)00582-2
A highly sensitive ZnO–TiO2 based thick film volatile organic compound (VOC) sensor had been developed. TiO2 was mixed in ZnO in various weight percentage (0%, 1%, 5% and 10%). The X-ray diffraction (XRD) analysis of mixtures sintered at 650 °C for 2 h revealed the appearance of Zn2TiO4 phase, whereas the surface morphological studies of the films based on the mixture indicated that the average grain size increased with the addition of a small amount of TiO2 in ZnO then decreased with higher TiO2 level. It was observed that the sensitivity greatly increased with increasing the content of TiO2. When the sensors operated at operating temperature of 370 °C, their sensitivity increased quasi-linearly with the concentration of alcohol and acetone, but the sensitivity to benzene, toluene and xylene increased rapidly in a lower concentration range then slowly in higher concentration range. The sensors showed rapid response–recovery time and the response and recovery time was around 10 and 5 s, respectively, at operating temperature >320 °C.
Co-reporter:DongZhi Hou, ChangSheng Xie, KaiJin Huang, ChangHong Zhu
Biomaterials 2003 Volume 24(Issue 10) pp:1781-1785
Publication Date(Web):May 2003
DOI:10.1016/S0142-9612(02)00578-1
Modified high shear homogenization and ultrasound techniques were employed to produce solid lipid nanoparticles (SLNs). Model drug mifepristone had been incorporated in SLNs. The mean particle size measured by laser diffractometry (LD) was found to be 106 nm with a narrow particle distribution of polydispersity index, 0.278. Differential scanning calorimetry and X-ray diffraction measurements suggested that the majority of the SLNs were less ordered arrangement of crystals, and this was favorable for increasing the drug loading capacity. The drug entrapment efficiency (EE%) of SLNs was more than 87 percent and showed relatively long-term physical stability as the leakage was very small after being stored for one month. Therefore, seemed this modified method could prepare high quality SLNs loading lipophilic drugs. It is a simple, available and effective method to produce SLNs.
Co-reporter:Wu Jun, Xie Changsheng, Bai Zikui, Zhu Bailin, Huang Kaijin, Wu Run
Materials Science and Engineering: B 2002 Volume 95(Issue 2) pp:157-161
Publication Date(Web):1 August 2002
DOI:10.1016/S0921-5107(02)00227-1
Varistors based on ZnO–lead zinc borosilicate glass were prepared from tetrapod ZnO nanopowders, every one of which had four needle-like legs and each one was about 20 nm or less in diameter and from several hundreds of nanometers to several micrometers in length by the method of direct co-sintering synthesis of oxides instead of adding amorphous lead zinc borosilicate frit. The compact green disks were conventionally sintered in air for 2 h at a temperature of 900–1170 °C. The varistors with nonlinear coefficient α=38.7 and leakage current IL=1.7 μA were obtained. The results showed that the sintering temperature was lowered to 900 °C, and there was very little influence of the sintering temperature on the nonlinear coefficient α at a range 900–1170 °C.
Co-reporter:Yuan Liu, Changsheng Xie, Tao Zou, Jie Li, Hao Chen, Dawen Zeng
Catalysis Communications (30 November 2011) Volume 16(Issue 1) pp:180-183
Publication Date(Web):30 November 2011
DOI:10.1016/j.catcom.2011.09.037
The photoelectrocatalytic (PEC) degradation of toluene in the gas phase over nanosized WO3 was investigated under both static bias (constant value) and dynamic bias (sine-wave, half sine-wave). The photocatalytic studies indicated that the dynamic bias had a higher PEC synergistic effect compared with the static bias. The photocatalytic efficiency reached the maximum value under 1V10MHz half sine-wave, which was 3.5 times that of WO3 without any external bias. More importantly, under low bias with high frequency, besides the benefit of enhanced efficiency, the formation of formaldehyde as a more poisonous intermediate could also be prevented in the degradation process.Low bias with high frequency can not only further enhance the efficiency of WO3 compared with constant bias, but also prevent the formation of formaldehyde as a more poisonous intermediate in the degradation process.Download full-size imageHighlights► A PEC technique applied in gas-phase for enhancing mineralization ability of WO3. ► The comparison between static and dynamic bias in PEC degradation is studied. ► Low bias with high frequency has the best enhanced effect rather than high bias. ► Low bias with high frequency prevents the formation of formaldehyde meanwhile.
Co-reporter:Qiang Zhu, Changsheng Xie, Huayao Li, Chaoqun Yang, Shunping Zhang and Dawen Zeng
Journal of Materials Chemistry A 2014 - vol. 2(Issue 23) pp:NaN4580-4580
Publication Date(Web):2014/03/07
DOI:10.1039/C4TC00011K
Energy band engineering is a promising method to tune the photoelectric properties of semiconductors. In this paper, we report an un-element-doped ZnO nanorod array film with a degenerate energy band via annealing in a hydrogen atmosphere. Due to the energy band modification, the photogenerated carrier transitions in the degenerate energy band, involving the valance band, the defect bands and the degenerate conduction band, cause unique photoelectric properties in the degenerate ZnO film. The degenerate ZnO film performs with outstanding conductivity and exhibits an obvious optical absorption in the visible region. Its photoluminescence and photoresponse properties are investigated to understand the fundamentals of photogenerated carrier excitation and recombination in the degenerate ZnO film. Interestingly, the degenerate ZnO film performs with poor photoresponse and has poor photocurrent efficiencies for ultraviolet, blue, and green illuminations, but the photoresponse for near-infrared illumination is attractive. Our results also demonstrate the selectively enhanced down-conversion photoluminescence both at the UV band and at the near-infrared band from the degenerate ZnO film after being excited by an ultraviolet laser source.
Co-reporter:Chaoqun Yang, Qiang Zhu, Tao Lei, Huayao Li and Changsheng Xie
Journal of Materials Chemistry A 2014 - vol. 2(Issue 44) pp:NaN9477-9477
Publication Date(Web):2014/09/12
DOI:10.1039/C4TC01150C
In this paper, four kinds of WO3 films, namely, Pt-loaded hydrogenated WO3, Pt-loaded WO3, and hydrogen-treated and untreated WO3 films were synthesized and their photoelectric properties were investigated at room temperature. The quantitative results showed that the gas-sensitized WO3 film in formaldehyde exhibited much higher photocurrent than that in air. In addition, the sensitivity of Pt-loaded hydrogenated WO3 to formaldehyde reached 15.8 which was nearly 15 times higher than that of the others. Moreover, Pt-loaded hydrogenated WO3 shows excellent electrical response towards formaldehyde in the dark. The intriguing performance of the Pt-loaded hydrogenated WO3 film indicates an efficient coupled effect of oxygen vacancies and Pt. The results provide the potential for improving the efficiency of photoelectric sensing devices by coupling two modification mechanisms. To explain the response characteristics of the four kinds of WO3 films, a schematic diagram of the band bending and spill over model are proposed.
Co-reporter:Shasha Zhang, Changsheng Xie, Guozhu Zhang, Qiang Zhu and Shunping Zhang
Physical Chemistry Chemical Physics 2015 - vol. 17(Issue 27) pp:NaN18054-18054
Publication Date(Web):2015/06/15
DOI:10.1039/C5CP02391B
Porous ZnO nanocrystalline films have been widely used in optoelectronic and gas-sensing applications. However, the effect mechanisms of the external fields, such as light, heat and atmosphere, are still controversial. In this work, the multi-variable coupling effects of the UV light, heat and oxygen were thoroughly studied by a newly proposed method, the central idea of which was to first isolate each effect of the fields on electron concentration and mobility, and then analyze how the coupling effects were achieved. Our results revealed the important roles of oxygen adsorption-induced interface barriers and photo-assisted thermal ionization first proposed here, because of which the positive coupling effect of UV light/heat and oxygen, as well as the negative coupling effect of UV light and heat was observed. Our work provides inspiration for studies on metal oxides from both the whole idea and the detailed argument.
