We report the structural, optical and electrical properties of Graphene-Vanadium oxide nanoparticles (rGO/VO-NPs) nanocomposites prepared via a hydrothermal method on glass substrates. The samples have been characteri...We report the structural, optical and electrical properties of Graphene-Vanadium oxide nanoparticles (rGO/VO-NPs) nanocomposites prepared via a hydrothermal method on glass substrates. The samples have been characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (ATR-FTIR), Raman spectroscopy, ultraviolet-visible spectra (Uv-Vis) (absorbance/reflectance) and electrical conductivity. Our results are revealing a remarkable effect on the morphology and structure of vanadium oxide nanoparticles. Hence, the graphene layers improved their electrical conductivity and highly influenced their optical properties. Therefore, the obtained results may lead to better performance for a large field of applications.展开更多
Microstructure and electrical properties of La2 O3-doped ZnO-Bi2 O3 thin films prepared by sol–gel process have been investigated.X-ray diffraction shows that most diffraction peaks of ZnO are equal,and the crystals ...Microstructure and electrical properties of La2 O3-doped ZnO-Bi2 O3 thin films prepared by sol–gel process have been investigated.X-ray diffraction shows that most diffraction peaks of ZnO are equal,and the crystals of ZnO grow well.Scanning electron microscopy and atomic force microscopy results indicate that the samples have a good structure and lower surface roughness.The nonlinear V–I characteristics of the films show that La2 O3 develops the electrical properties largely and the best doped content is 0.3% lanthanum ion,with the leakage current of 0.25 mA,the threshold field of 150 V/mm and the nonlinear coefficient of 4.0 in detail.展开更多
The fine control of doping levels in graphene materials such as reduced graphene oxide(RGO)is important to properly manipulate their ambipolar transport characteristics for various device applications.However,conventi...The fine control of doping levels in graphene materials such as reduced graphene oxide(RGO)is important to properly manipulate their ambipolar transport characteristics for various device applications.However,conventional doping methods involve complex chemical reactions,large-scale doping processes,and poor stability.Herein,a simple and controllable electrochemical doping treatment(EDT),performed via the conductive channels created at the RGO surface by the application of an electric field,is introduced to tailor the electrical properties of RGO films.X-ray photoelectron spectroscopy and Raman spectroscopy measurements are performed to detect the presence of Ni atoms in RGO films after the EDT(EDT-RGO).Then,EDT-RGO field-effect transistors(FETs)are fabricated with different doping areas(0 to 100%fractional area)on the RGO active channel to investigate the effect and selective-area doping capability of the EDT.Owing to p-type doping compensation by the intercalated Ni atoms,the electron mobility of the EDT-RGO FET decreases from 1.40 to 0.12 cm2 V-1s-1 compared with that of the undoped RGO-FET,leading to the conversion from ambipolar to unipolar p-type transfer characteristics.展开更多
Electrical transport and thermoelectric properties of Ni-doped YCOl-xNixO3 （0 ≤ x ≤0.07）, prepared by using the sol-gel process, are investigated in a temperature range from 100 to 780 K. The results show that wit...Electrical transport and thermoelectric properties of Ni-doped YCOl-xNixO3 （0 ≤ x ≤0.07）, prepared by using the sol-gel process, are investigated in a temperature range from 100 to 780 K. The results show that with the increase of Ni doping content, the values of DC resistivity of YCo 1-xNixO3 decrease, but carder concentration increases. The temperature dependences of the resistivity for YCOl-xNixO3 are found to follow a relation of lnp o, lIT in a low-temperature range （LTR） （T 〈- 304 K for x = 0; - 230 K 〈 T 〈- 500 K for x = 0.02, 0.05, and 0.07） and high-temperature range （HTR） （T 〉-655 K for all compounds）, respectively. The estimated apparent activation energies for conduction Eal in LRT and Ea2 in HTR are both found to decrease monotonically with doping content increasing. At very low temperatures （T 〈-230 K）, Mott＇s law is observed for YCOl-xNixO3 （x≥ 0.02）, indicating that considerable localized states form in the heavy doping compounds. Although the Seebeck coefficient of the compound decreases after Ni doping, the power factor of YCOl-xNixO3 is enhanced remarkably in a temperature range from 300 to 740 K, i.e., a 6-fold increase is achieved at 500 K for YCo0.98Ni0.0203, indicating that the high-temperature thermoelectric property of YCoO3 can be improved by partial substitution of Ni for Co.展开更多
Herein,graphene oxide(GO)-encapsulated silica(SiO 2)hybrids(GO@SiO 2)were prepared via electrostatic self-assembly of the 3-aminopropyltriethoxysilane(APS)-modified SiO_(2) and GO.The as-prepared GO@SiO 2 was introduc...Herein,graphene oxide(GO)-encapsulated silica(SiO 2)hybrids(GO@SiO 2)were prepared via electrostatic self-assembly of the 3-aminopropyltriethoxysilane(APS)-modified SiO_(2) and GO.The as-prepared GO@SiO 2 was introduced into polydimethyl-siloxane(PDMS)elastomer to simultaneously increase the dielectric constant(k)and mechanical properties of PDMS.Then,the in situ thermal reduction of GO@SiO_(2)/PDMS composites was conducted at 180℃ for 2 h to increase the interfacial polariz-ability of GO@SiO_(2).As a result,the values of k at 1000 Hz are largely improved from 3.2 for PDMS to 13.3 for the reduced GO@SiO_(2)(RGO@SiO_(2))/PDMS elastomer.Meanwhile,the dielectric loss of the composites remains low(<0.2 at 1000 Hz).More importantly,the actuated strain at low electric field(5 kV/mm)obviously increases from 0.3%for pure PDMS to 2.59%for the composites with 60 phr of RGO@SiO_(2),an eightfold increase in the actuated strain.In addition,both the tensile strength and elastic modulus are obviously improved by adding 60 phr of RGO@SiO_(2),indicating a good reinforcing effect of RGO@SiO_(2) on PDMS.Our goal is to develop a simple and effective way to improve the actuated performance and mechanical strength of the PDMS dielectric elastomer for its wider application.展开更多
Photonic crystal（Ph C） presents unique optical properties and functionality, and are used widely as detectors, modulators, plasmonics and light generating devices. However, the low electrical conductivity and mechan...Photonic crystal（Ph C） presents unique optical properties and functionality, and are used widely as detectors, modulators, plasmonics and light generating devices. However, the low electrical conductivity and mechanical strength limit its applications. We introduced here a layer-by-layer composite membrane based on reduced graphene oxide（RGO） and two-dimensional（2 D） colloidal crystal array（CCA）. The 2 D CCA was fabricated by an air/water interface deposition technique using polystyrene（PS）and polymethyl methacrylate（PMMA） colloidal particles. The composite membrane were characterized by SEM, Debye diffraction, reflectance spectra and electrical resistance measurement. The results indicated that layer-by-layer composite membrane have highly periodicity, and the monolayer of RGO and 2 D CCA combined tightly. The Debye diffraction rings of the layer-by-layer heterostructure composite are the superimposition of the individual monolayers of 2 D CCA. The reflection spectrum of the layer-by-layer heterostructure composite membrane showed that two peaks of reflection curve located in near ultraviolet region and visible region respectively, and the RGO sheet have no influence on the peak position and shape of reflection curve of the Ph C. The RGO improved the electrical conductivity of the layer-by-layer heterostructure composite. The layer-by-layer heterostructure composite showed promising potential for the applications as sensors and optoelectronic devices.展开更多
Thermoelectric properties of Al substituted compounds Ca3（Co1-xAlx）4O9 （x=0, 0.03, 0.05）, prepared by a sol-gel process, have been investigated in the temperature range 305-20 K. The results indicate that after Al...Thermoelectric properties of Al substituted compounds Ca3（Co1-xAlx）4O9 （x=0, 0.03, 0.05）, prepared by a sol-gel process, have been investigated in the temperature range 305-20 K. The results indicate that after Al substitution for Co in Ca3（Co1-xAlx）4O9, the direct current electrical resistivity and thermopower increase due to the reduction of carrier concentration. Experiments show that Al substitution results in decreased lattice thermal conductivity. The figure of merit of temperature behavior suggests that Ca3（Co0.97Al0.03）4O9 would be a promising candidate thermoelectric material for high-temperature thermoelectric application.展开更多
Polycrystalline Ca2.7-xEr0.3NaxCo4O9+δ (x=0, 0.05, 0.1, 0.15) samples were prepared using a sol-gel process followed by hot-pressing technique sintering and their high-temperature thermoelectric properties were measu...Polycrystalline Ca2.7-xEr0.3NaxCo4O9+δ (x=0, 0.05, 0.1, 0.15) samples were prepared using a sol-gel process followed by hot-pressing technique sintering and their high-temperature thermoelectric properties were measured from 350 up to 1073 K. The results showed that with the increase of the dopant amount of Na, the electrical conductivity increased, while the Seebeck coefficient and thermal conductivity decreased. The electrical conductivity was dominated by polaron hopping conductivity mechanism above about 550 K and the Na+ substitution for Ca2+ could not change the transport mechanism. The dimensionless figure of merit ZT value reaches 0.31 for Ca2.55Er0.3Na0.15Co4O9+δ at 1073 K, which suggested that Ca2.7-xEr0.3NaxCo4O9+δ (x=0, 0.05, 0.1, 0.15) were good potential oxides for thermoelectric application.展开更多
文摘We report the structural, optical and electrical properties of Graphene-Vanadium oxide nanoparticles (rGO/VO-NPs) nanocomposites prepared via a hydrothermal method on glass substrates. The samples have been characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (ATR-FTIR), Raman spectroscopy, ultraviolet-visible spectra (Uv-Vis) (absorbance/reflectance) and electrical conductivity. Our results are revealing a remarkable effect on the morphology and structure of vanadium oxide nanoparticles. Hence, the graphene layers improved their electrical conductivity and highly influenced their optical properties. Therefore, the obtained results may lead to better performance for a large field of applications.
基金Project(20123227120021)supported by the Specialized Research Fund for the Doctoral Program of Higher Education of ChinaProject(BK2012156)supported by the Natural Science Foundation of Jiangsu Province,China+3 种基金Project(KFJJ201105)supported by the Opening Project of State Key Laboratory of Electronic Thin Films and Integrated Devices,ChinaProject(CJ20125001)supported by the Application Program for Basic Research of Changzhou,ChinaProject(13KJB430006)supported by the Universities Natural Science Research project of Jiangsu Province,ChinaProject supported by the Industrial Center of Jiangsu University Undergraduate Practice-Innovation Training Program,China
文摘Microstructure and electrical properties of La2 O3-doped ZnO-Bi2 O3 thin films prepared by sol–gel process have been investigated.X-ray diffraction shows that most diffraction peaks of ZnO are equal,and the crystals of ZnO grow well.Scanning electron microscopy and atomic force microscopy results indicate that the samples have a good structure and lower surface roughness.The nonlinear V–I characteristics of the films show that La2 O3 develops the electrical properties largely and the best doped content is 0.3% lanthanum ion,with the leakage current of 0.25 mA,the threshold field of 150 V/mm and the nonlinear coefficient of 4.0 in detail.
基金supported financially by the National Research Foundation of Korea(NRF)(No.2016R1A3B1908249).
文摘The fine control of doping levels in graphene materials such as reduced graphene oxide(RGO)is important to properly manipulate their ambipolar transport characteristics for various device applications.However,conventional doping methods involve complex chemical reactions,large-scale doping processes,and poor stability.Herein,a simple and controllable electrochemical doping treatment(EDT),performed via the conductive channels created at the RGO surface by the application of an electric field,is introduced to tailor the electrical properties of RGO films.X-ray photoelectron spectroscopy and Raman spectroscopy measurements are performed to detect the presence of Ni atoms in RGO films after the EDT(EDT-RGO).Then,EDT-RGO field-effect transistors(FETs)are fabricated with different doping areas(0 to 100%fractional area)on the RGO active channel to investigate the effect and selective-area doping capability of the EDT.Owing to p-type doping compensation by the intercalated Ni atoms,the electron mobility of the EDT-RGO FET decreases from 1.40 to 0.12 cm2 V-1s-1 compared with that of the undoped RGO-FET,leading to the conversion from ambipolar to unipolar p-type transfer characteristics.
基金Project supported by the Key Laboratory of Novel Thin Film Solar Cells, Chinese Academy of Sciences (Grant No. KF201101)the Key Science Foundation of Higher Education Institutions of Anhui Province, China (Grant Nos. KJ2011A053 and KJ2012Z034)the National Natural Science Foundation of China(Grant Nos. 51202005, 11204005, and 41075027)
文摘Electrical transport and thermoelectric properties of Ni-doped YCOl-xNixO3 （0 ≤ x ≤0.07）, prepared by using the sol-gel process, are investigated in a temperature range from 100 to 780 K. The results show that with the increase of Ni doping content, the values of DC resistivity of YCo 1-xNixO3 decrease, but carder concentration increases. The temperature dependences of the resistivity for YCOl-xNixO3 are found to follow a relation of lnp o, lIT in a low-temperature range （LTR） （T 〈- 304 K for x = 0; - 230 K 〈 T 〈- 500 K for x = 0.02, 0.05, and 0.07） and high-temperature range （HTR） （T 〉-655 K for all compounds）, respectively. The estimated apparent activation energies for conduction Eal in LRT and Ea2 in HTR are both found to decrease monotonically with doping content increasing. At very low temperatures （T 〈-230 K）, Mott＇s law is observed for YCOl-xNixO3 （x≥ 0.02）, indicating that considerable localized states form in the heavy doping compounds. Although the Seebeck coefficient of the compound decreases after Ni doping, the power factor of YCOl-xNixO3 is enhanced remarkably in a temperature range from 300 to 740 K, i.e., a 6-fold increase is achieved at 500 K for YCo0.98Ni0.0203, indicating that the high-temperature thermoelectric property of YCoO3 can be improved by partial substitution of Ni for Co.
基金We would like to express our sincere thanks to the National Natural Science Foundation of China[grant number 51173007],[grant number 51103090],[grant number 51221002]for financial support.
文摘Herein,graphene oxide(GO)-encapsulated silica(SiO 2)hybrids(GO@SiO 2)were prepared via electrostatic self-assembly of the 3-aminopropyltriethoxysilane(APS)-modified SiO_(2) and GO.The as-prepared GO@SiO 2 was introduced into polydimethyl-siloxane(PDMS)elastomer to simultaneously increase the dielectric constant(k)and mechanical properties of PDMS.Then,the in situ thermal reduction of GO@SiO_(2)/PDMS composites was conducted at 180℃ for 2 h to increase the interfacial polariz-ability of GO@SiO_(2).As a result,the values of k at 1000 Hz are largely improved from 3.2 for PDMS to 13.3 for the reduced GO@SiO_(2)(RGO@SiO_(2))/PDMS elastomer.Meanwhile,the dielectric loss of the composites remains low(<0.2 at 1000 Hz).More importantly,the actuated strain at low electric field(5 kV/mm)obviously increases from 0.3%for pure PDMS to 2.59%for the composites with 60 phr of RGO@SiO_(2),an eightfold increase in the actuated strain.In addition,both the tensile strength and elastic modulus are obviously improved by adding 60 phr of RGO@SiO_(2),indicating a good reinforcing effect of RGO@SiO_(2) on PDMS.Our goal is to develop a simple and effective way to improve the actuated performance and mechanical strength of the PDMS dielectric elastomer for its wider application.
基金supported by the National Natural Science Foundation of China (Nos. 21375009 and U1530141)the Fundamental Research Foundation of Beijing Institute of Technology (No. 20151042004)
文摘Photonic crystal（Ph C） presents unique optical properties and functionality, and are used widely as detectors, modulators, plasmonics and light generating devices. However, the low electrical conductivity and mechanical strength limit its applications. We introduced here a layer-by-layer composite membrane based on reduced graphene oxide（RGO） and two-dimensional（2 D） colloidal crystal array（CCA）. The 2 D CCA was fabricated by an air/water interface deposition technique using polystyrene（PS）and polymethyl methacrylate（PMMA） colloidal particles. The composite membrane were characterized by SEM, Debye diffraction, reflectance spectra and electrical resistance measurement. The results indicated that layer-by-layer composite membrane have highly periodicity, and the monolayer of RGO and 2 D CCA combined tightly. The Debye diffraction rings of the layer-by-layer heterostructure composite are the superimposition of the individual monolayers of 2 D CCA. The reflection spectrum of the layer-by-layer heterostructure composite membrane showed that two peaks of reflection curve located in near ultraviolet region and visible region respectively, and the RGO sheet have no influence on the peak position and shape of reflection curve of the Ph C. The RGO improved the electrical conductivity of the layer-by-layer heterostructure composite. The layer-by-layer heterostructure composite showed promising potential for the applications as sensors and optoelectronic devices.
基金financially supported by the Key Lab of Novel Thin Film Solar Cells,Chinese Academy of Sciences (No.KF201101)the Provincial Science Key Foundation of Higher Education Institutions of Anhui,China(No. KJ2011A053)the National Natural Science Foundation of China(No.51202005)
文摘Thermoelectric properties of Al substituted compounds Ca3（Co1-xAlx）4O9 （x=0, 0.03, 0.05）, prepared by a sol-gel process, have been investigated in the temperature range 305-20 K. The results indicate that after Al substitution for Co in Ca3（Co1-xAlx）4O9, the direct current electrical resistivity and thermopower increase due to the reduction of carrier concentration. Experiments show that Al substitution results in decreased lattice thermal conductivity. The figure of merit of temperature behavior suggests that Ca3（Co0.97Al0.03）4O9 would be a promising candidate thermoelectric material for high-temperature thermoelectric application.
基金the National Nature Science Foundation of China (20571019)Project-sponsored by the Scientific Research Foundation for the Returned Overseas Chinese Scholars ,Heilongjiang (LC06C13)Program of Harbin Subject Chief Scientist
文摘Polycrystalline Ca2.7-xEr0.3NaxCo4O9+δ (x=0, 0.05, 0.1, 0.15) samples were prepared using a sol-gel process followed by hot-pressing technique sintering and their high-temperature thermoelectric properties were measured from 350 up to 1073 K. The results showed that with the increase of the dopant amount of Na, the electrical conductivity increased, while the Seebeck coefficient and thermal conductivity decreased. The electrical conductivity was dominated by polaron hopping conductivity mechanism above about 550 K and the Na+ substitution for Ca2+ could not change the transport mechanism. The dimensionless figure of merit ZT value reaches 0.31 for Ca2.55Er0.3Na0.15Co4O9+δ at 1073 K, which suggested that Ca2.7-xEr0.3NaxCo4O9+δ (x=0, 0.05, 0.1, 0.15) were good potential oxides for thermoelectric application.
