SnO2 nano particles with various Pd-doping concentrations were prepared using a template-free hydrothermal method.The effects of Pd doping on the crystal structure,morphology,microstructure,thermal stability and surfa...SnO2 nano particles with various Pd-doping concentrations were prepared using a template-free hydrothermal method.The effects of Pd doping on the crystal structure,morphology,microstructure,thermal stability and surface chemistry of these nano particles were characterized by transmission electron microscope,X-ray diffractometer and X-ray photoelectron spectroscope respectively.It was observed that Pd-doping had little effect on the grain sizes of the obtained SnO2 nano particles during the hydrothermal route.During thermal annealing,Pd-doping could restrain the growth of grain sizes below 500℃ while the grain growth was promoted when the temperature increased to above 700℃.XPS results revealed that Pd existed in three chemical states in the as-synthesized sample as Pd^0,Pd^2＋ and Pd^4＋,respectively.Pd^4＋ was the main state which was responsible for improving the gas-sensing property.The optimal Pd-doping concentration for better gas-sensing property and thermal stability was 2.0%-2.5% （mole fraction）.展开更多
Polythiophene/WO3（PTP/WO3）organic-inorganic hybrids were synthesized by an in situ chemical oxidative polymerization method,and char- acterized by X-ray diffraction（XRD）,transmission electron microscopy（TEM）and ...Polythiophene/WO3（PTP/WO3）organic-inorganic hybrids were synthesized by an in situ chemical oxidative polymerization method,and char- acterized by X-ray diffraction（XRD）,transmission electron microscopy（TEM）and thermo-gravimetric analysis（TGA）.The Polythiophene/ WO3 hybrids have higher thermal stability than pure polythiophene,which is beneficial to potential application as chemical sensors.Gas sensing measurements demonstrate that the gas sensor based on the Polythiophene/WO3 hybrids has high response and good selectivity for de- tecting NO2 of ppm level at low temperature.Both the operating temperature and PTP contents have an influence on the response of PTP/WO3 hybrids to NO2.The 10 wt%PTP/WO3 hybrid showed the highest response at low operating temperature of 70-C.It is expected that the PTP/WO3 hybrids can be potentially used as gas sensor material for detecting the low concentration of NO2 at low temperature.展开更多
The high-temperature stabilization of ZnO nanorods synthesized by hydrothermal treatment was investigated. The structure and morphologies of ZnO nanorods were characterized by XRD and SEM, respectively. The thermal st...The high-temperature stabilization of ZnO nanorods synthesized by hydrothermal treatment was investigated. The structure and morphologies of ZnO nanorods were characterized by XRD and SEM, respectively. The thermal stability of ZnO nanorods was also detected by thermal gravity analyzing. Thermal annealing treatment results indicate that ZnO nanorods are fundamentally stable when annealing temperature is lower than 600 ℃. When annealing temperature is beyond 600℃, the diameters of ZnO nanorods obviously decrease and the aggravating tendency of nanorods between each other also increase. Annealing treatment can greatly influence the gas sensing properties of ZnO nanorods. Comparing with ZnO nanorods without annealing treatment, the gas sensing property of ZnO nanorods to H2 with concentration of 2.5×10-6 can increase from 2.22 to 3.56. ZnO nanorods annealed at 400 ℃ exhibit optimum gas sesing property to H2 gas.展开更多
Bi3.15Nd0.85Ti3O12 (BNdT) films were deposited on Pt/Ti/SiO2/Si(100) substrates by a metal organic decomposition (MOD)method, and annealed by a rapid thermal annealing process in oxygen atmosphere and in air, respecti...Bi3.15Nd0.85Ti3O12 (BNdT) films were deposited on Pt/Ti/SiO2/Si(100) substrates by a metal organic decomposition (MOD)method, and annealed by a rapid thermal annealing process in oxygen atmosphere and in air, respectively. The crystalline structuresand morphologies of BNdT films were characterized by X-ray diffraction and field-emission scanning electron microscopy, and thegas sensing properties were measured by monitoring its resistance at different gas concentrations. The results indicate that the BNdTfilms annealed in air are of porous microstructure and rough surface, and the annealing atmosphere has great influence on gas sensingproperties. At an operating temperature of 100 °C, the BNdT films annealed in air are of high response value to 1×10?6 gaseousethanol, and the detecting limit is as low as 0.1×10?6. The corresponding response and recovery time is about 10 and 6 s, respectively.The results can offer useful guidelines for fabricating high performance ethanol sensors.展开更多
Chemically synthesized ZnS thin film is found to be a good x-ray radiation sensor. We report the effect of annealing on the x-ray radiation detection sensitivity of a ZnS thin film synthesized by a chemical bath depos...Chemically synthesized ZnS thin film is found to be a good x-ray radiation sensor. We report the effect of annealing on the x-ray radiation detection sensitivity of a ZnS thin film synthesized by a chemical bath deposition technique. The chemically synthesized ZnS films are annealed at 333, 363 and 393K for 1 h. Structural analyses show that the lattice defects in the films decrease with annealing. Further, the band gap is also found to decrease from 3.38 to 3.21 eV after annealing at 393K. Current-voltage characteristics of the films are studied under dark and x-ray irradiation conditions. Due to the decrease of lattice defects and band gap, the conductivity under dark conditions is found to increase from 2.06 × 10^-6 to 1.69 × 10^-5 S/em, while that under x-ray irradiation increases from 4.13 × 10^-5 to 5.28 ×10^-5 S/cm. On the other hand, the x-ray radiation detection sensitivity of the films is found to decrease with annealing. This decrease of detection sensitivity is attributed to the decrease of the band gap as well as some structural and surface morphological changes occurring after annealing.展开更多
A type of compact solution concentration sensor based on a microfiber with a nanoscale-structured film is proposed and demonstrated experimentally. Additional loss at different solution concentrations is calculated by...A type of compact solution concentration sensor based on a microfiber with a nanoscale-structured film is proposed and demonstrated experimentally. Additional loss at different solution concentrations is calculated by means of the three-dimensional finite-difference time-domain （3D-FDTD） method. The microfiber is fabricated by using the flame-heated scanning technique. Nanoscale-structured film is coated on the microfiber surface, which is assembled as a sensing unit. The sensitivity of this kind of sensor increases with the decreasing diameters of the microfiber. When the diameter of the microfiber is 2 #m, a minimum concentration sensitivity of 1% （under 450s measuring time） is demonstrated in the experiment. Higher sensitivity can be attained when the solution concentration is higher. The sensing properties of this microfiber with the nanoscale-structured film may provide opportunities for new applications in optical sensing devices.展开更多
Semiconductor-type TiO2 oxygen sensing thin films were synthesized using tetrabutyl titanate （Ti （OBu）4） as precursor and diethanolamine （DEA） as complexing agent by the sol-get process. The porous and oxygen se...Semiconductor-type TiO2 oxygen sensing thin films were synthesized using tetrabutyl titanate （Ti （OBu）4） as precursor and diethanolamine （DEA） as complexing agent by the sol-get process. The porous and oxygen sensing TiO2 films were obtained by the addition of polyethylene glycol （PEG）. The micrographs of scanning electron microscope （SEM） show that the pores of the sample about 400-600 nm in size with PEG（2 000 g/mol） are larger than those about 300 nm in size with PEG（ 1 000 g/mol）, while the density of pores is lower. The results also indicate that increasing the content of PEG properly is beneficial to the formation of porous structure. With the increasing content of PEG from 0 g to 2.5 g, the oxygen sensitivity increases from 330 to more than 1 000 at 800 ℃, from 170 to more than 1 000 at 900℃, and the response time to O2 and H2 are about 1.5 s and less than 1s, respectively.展开更多
The mechanical and strain sensing properties of carbon nanotube composite yarns （CNTs/PDMS） with different weight percent of PDMS were studied. The CNT/PDMS composite yarn was prepared by infiltration method. Pictur...The mechanical and strain sensing properties of carbon nanotube composite yarns （CNTs/PDMS） with different weight percent of PDMS were studied. The CNT/PDMS composite yarn was prepared by infiltration method. Pictures of diameter of CNT composite yarns were obtained though polarized light microscope. Resistance change values of CNT composites under stretching were obtained though the single fiber strength tester and digital multimeter and related mechanical, electrical software. The changes of mechanical properties. electrical properties and sensing pertbrmance of pure and composite CNT yarns were discussed and analyzed. The results showed that the strength of CNT yarn declined after it was composited with PDMS polymer. In addition, the conductivity and sensing performance of CNT yarns improved significantly. The most suitable CNT composite yam occurs at PDMS mass fraction of 1% when strength and sensing properties were all considered.展开更多
We demonstrate a fiber refractive index（RI） sensor based on an excessively tilted fiber grating（ExTFG）immobilized by large-size plasmonic gold nanoshells（GNSs）. The GNSs are covalently linked on ExTFG surface.Ex...We demonstrate a fiber refractive index（RI） sensor based on an excessively tilted fiber grating（ExTFG）immobilized by large-size plasmonic gold nanoshells（GNSs）. The GNSs are covalently linked on ExTFG surface.Experimental results demonstrate that both the intensity of the transverse magnetic（TM） and transverse electric（TE） modes of ExTFG are significantly modulated by the localized surface plasmon resonance（LSPR） of GNSs due to the wide-range absorption band. The wavelength RI sensitivities of the TM and TE modes in the low RI range of 1.333–1.379 are improved by ～25% and ～14% after GNSs immobilization, respectively, and the intensity RI sensitivities are ～599%/RIU and ～486%/RIU, respectively.展开更多
ZnO thin films prepared by using quantitative filter paper as a template and Zn（CH3CO2）2.2H2O ethanol precursor solution were characterized by scanning electron microscopy （SEM） and X-ray diffraction （XRD）. The ...ZnO thin films prepared by using quantitative filter paper as a template and Zn（CH3CO2）2.2H2O ethanol precursor solution were characterized by scanning electron microscopy （SEM） and X-ray diffraction （XRD）. The effects of sample calcination temperature, precursor concentration and filter paper types were studied, and the growth process was investigated by infra-red （IR） spectroscopy and thermogravimettic analysis/differential thermal analysis （TGA/DTA）. The results show that samples soaked in a 1.5 mol/L Zn（CH3 CO2）2.2H2O ethanol solution and calcined at 600 ℃ yield ZnO films of uniform particle size, approximately 30, 40 and 50 nm. for fast-, medium- and slow-speed filter papers, respectively. The formaldehyde gas sensing properties of the ZnO nanoparticles were tested, showing that the material prepared from fast-speed filter paper has a higher response to 120-205 ppm formaldehyde at 400 ℃ than that prepared from medium- or slow-sneed paper, which depends on the narticle size.展开更多
The thin film gas sensors of bismuth iron molybdate were prepared by ion beam sputtering technique. The prototype gas sensors studied have high sensitivity and selectivity to reducing gases, such as ethanol vapor, s...The thin film gas sensors of bismuth iron molybdate were prepared by ion beam sputtering technique. The prototype gas sensors studied have high sensitivity and selectivity to reducing gases, such as ethanol vapor, show a long term stability of response under most operating conditions and insensitivity to atmospheric humidity, and respond quickly comparing to traditional sintered gas sensors. The crystallographic structure and phase composition of these thin films were investigated with XRD, XPS and SEM techniques.展开更多
Flexible sensors,a class of devices that can convert external mechanical or physical signals into changes in resistance,capacitance,or current,have developed rapidly since the concept was first proposed.Due to the spe...Flexible sensors,a class of devices that can convert external mechanical or physical signals into changes in resistance,capacitance,or current,have developed rapidly since the concept was first proposed.Due to the special properties and naturally occurring excellent microstructures of biomaterials,it can provide more desirable properties to flexible devices.This paper systematically discusses the commonly used biomaterials for bio-based flexible devices in current research applications and their deployment in preparing flexible sensors with different mechanisms.According to the characteristics of other properties and application requirements of biomaterials,the mechanisms of their functional group properties,special microstructures,and bonding interactions in the context of various sensing applications are presented in detail.The practical application scenarios of biomaterial-based flexible devices are highlighted,including human-computer interactions,energy harvesting,wound healing,and related biomedical applications.Finally,this paper also reviews in detail the limitations of biobased materials in the construction of flexible devices and presents challenges and trends in the development of biobased flexible sensors,as well as to better explore the properties of biomaterials to ensure functional synergy within the composite materials.展开更多
We report the structural characterization and proposed formation mechanism of honeycomb-like ZnO conglomerations fabricated by direct precipitation method. X-ray diffraction （XRD）, energy-disperse X-ray spectrometry...We report the structural characterization and proposed formation mechanism of honeycomb-like ZnO conglomerations fabricated by direct precipitation method. X-ray diffraction （XRD）, energy-disperse X-ray spectrometry （EDS）, scanning electron microscopy （SEM） showed that the as-prepared ZnO calcined at 700 ℃ were micron sphere particles with honeycomb-like structure. In the UV-vis absorbing spectrum, it was observed that there is a new additional absorption band at 260 nm, and it was speculated that the absorption may be caused by defects on the surface and interface of honeycomb-like ZnO. The as-products showed high sensitivity and short response time to sulfured hydrogen gas. These results demonstrate that honeycomb-like ZnO conglomerations are very promising materials for fabricating H2S gas sensors.展开更多
Capacitive humidity sensors were made of nanometer barium titanate.The pellets were prepared under different pressures between 3920N to 7850N force.The capacitance changes in three orders of magnitude in the relative ...Capacitive humidity sensors were made of nanometer barium titanate.The pellets were prepared under different pressures between 3920N to 7850N force.The capacitance changes in three orders of magnitude in the relative humidity range of 10%～98%,indicating high humidity sensitivity of the sensors.At a certain measuring frequency,the capacitance of the sensors increases as increasing of the preparation pressure,while the sensitivity of the sensors basically remains the same.The frequencies corresponding to the peaks of the dielectric loss of the sensors move to the higher frequency direction as increasing of the relative humidity.At a certain humidity,the frequencies corresponding to the peaks of the dielectric loss move to the higher frequency direction as increasing of the preparation pressure.展开更多
A series of aluminium-containing α-type hydrated zirconium hydrogen phosphates,Zr_(1-x)Alx (H_(1+x/2)PO_4 )_2 with x=0-0.06,were hydrothermally synthesized and characterizedby means of X-ray diffraction,differential ...A series of aluminium-containing α-type hydrated zirconium hydrogen phosphates,Zr_(1-x)Alx (H_(1+x/2)PO_4 )_2 with x=0-0.06,were hydrothermally synthesized and characterizedby means of X-ray diffraction,differential thermal analysis and thermogravimetric analysis.The proton conductivity,1.2×10￣(-4) S·cm￣(-1)at 180℃ was found in Zr_(0.98)Al_(0.02)(H_(1.01)PO_4)_2·H_2O.Humidity-sensing measurements were carried out at 120℃ and 140℃ respectively.Even a limited substitution of Al for Zr can enhance both proton conductivity and humidity sensitivity.展开更多
Nanocrystalline tin oxide samples were prepared by using Sn2 （NH4 ）2 （C2O4）3 as the precursor. The thermal decompositions were respectively conducted at 250,450 and 650 ℃. TG-DTA, XRD, TEM, FTIR were used to char...Nanocrystalline tin oxide samples were prepared by using Sn2 （NH4 ）2 （C2O4）3 as the precursor. The thermal decompositions were respectively conducted at 250,450 and 650 ℃. TG-DTA, XRD, TEM, FTIR were used to characterize the samples. The indirect heating sensors by using these materials as sensitive bodies were fabricated on an alumina tube with Au electrodes and platinum wires. Sensing properties of these sensors were investigated. It was found that the tin oxide sample obtained by thermal decomposition at 450 ℃ has a higher sensitivity to C2H5OH and a higher selectivity to hexane and ammonia than those obtained via the conventional precipitate method and the working temperatures needed were greatly decreased.展开更多
A γ - type of layered zirconium hydrogen phosphate, Zr(HPO 4) 2·2H 2O( γ ZrP), was synthesized under hydrothermal conditions and characterized by powder X ray diffraction and thermogravimetric analysis....A γ - type of layered zirconium hydrogen phosphate, Zr(HPO 4) 2·2H 2O( γ ZrP), was synthesized under hydrothermal conditions and characterized by powder X ray diffraction and thermogravimetric analysis. The temperature dependence of the proton conductivity in γ ZrP was investigated in a temperature range of 23￣413 ℃ by ac impedance spectroscopy. The variation of the conductivity with water loss and phase transitions was observed. The best proton conductivity in γ ZrP is 6×10 -4 S·cm -1 at 60 ℃. The proton conductivities in the dehydrated sample are ￣10 -5 at 150 ℃ and ￣10 -4 S·cm -1 at 350 ℃, respectively. The conductivities as a function of humidity in the temperature range of 120￣200 ℃ were measured.展开更多
Carbon nanotube(CNT)yarns with adjustable diameters were manufactured by twisting CNT films with varied twists.Different from traditional CNT fibers,CNT yarns exhibited a larger diameter(423μm)and a higher tensile fo...Carbon nanotube(CNT)yarns with adjustable diameters were manufactured by twisting CNT films with varied twists.Different from traditional CNT fibers,CNT yarns exhibited a larger diameter(423μm)and a higher tensile force(1988 cN).The results showed that CNT yarns with the twist angle of 35°exhibited the highest conductivity(886 S/cm)and the highest tensile strain(35%).展开更多
Due to its unique physical,chemical and surface electronic properties,molybdenum disulfide(MoS_(2))nanosheets open up a new avenue for nitrogen dioxide(NO2)detection at room temperature.Nevertheless,the gas sensing pr...Due to its unique physical,chemical and surface electronic properties,molybdenum disulfide(MoS_(2))nanosheets open up a new avenue for nitrogen dioxide(NO2)detection at room temperature.Nevertheless,the gas sensing properties of pure MoS_(2) nanosheets are inevitably degenerated by the adsorption of atmospheric oxygen,which results in weak stability for MoS_(2)-based gas sensors.Reducing surface defects and constructing heterojunctions may be effective strategies to improve the gas sensing properties of MoS_(2) nanosheets.In this work,we design a novel nanocomposite based on MoS_(2) nanosheets decorated with tin disulfide(SnS_(2))nanoparticles(MoS_(2)/SnS_(2))via combining the mechanical exfoliation method with the facile hydrothermal method.The experimental results indicate that,after surfaces decoration with SnS_(2) nanoparticles,the as-prepared gas sensor based on MoS_(2)/SnS_(2) nanocomposites exhibits reliable long-term stability with the maximum response value drift of less than 3%at room temperature.Moreover,the MoS_(2)/SnS_(2) sensor also possesses desirable gas sensing properties upon NO_(2) at room temperature,such as high sensitivity,rapid response/recovery speed(28 s/3 s,5×10^(-6) NO_(2)),satisfactory selectivity,favorable repeatability and reversibility.The improved gas sensing properties of MoS_(2)/SnS_(2) nanocomposites can be attributed to the unique electronic properties of MoS 2 nanosheets with the fewer layers structure and the competitive adsorption effect of SnS_(2) nanoparticles.This work elucidates that SnS_(2) nanoparticles serving as an effective antioxidative decoration can promote the stability of MoS_(2) nanosheets,providing a promising approach to achieve high-stability NO2 gas sensors at room temperature.展开更多
MoS2,acting as a promising gas sensing material,has shown huge potential in monitoring of toxic and harmful gases at room temperature.However,MoS2-based gas sensors still suffer from poor gas sensing performance such ...MoS2,acting as a promising gas sensing material,has shown huge potential in monitoring of toxic and harmful gases at room temperature.However,MoS2-based gas sensors still suffer from poor gas sensing performance such as poor sensitivity,long response time.Constructing the hete ro structure is an effective approach to improve gas-sensing performance of MoS2.Herein,PbS@MoS2 composites synthesized by mechanical exfoliation combining with wet-chemical precipitation are used to investigate its performance in detecting NO2 at room temperature.The response value of PbS@MoS2 gas sensor against NO2 is significantly improved compared with the pure MoS2 gas sensor.At the same time,the modification with PbS also accelerates the response speed of MoS2,and the response time is almost reduced by two orders of magnitude,from hundreds of seconds to less than ten seconds.The enhanced response value and fast response time are mainly benefited from the modulation effect of NO2 to PbS@MoS2 heterostructure and the mechanically exfoliated MoS2 surface with few defects.This work can be expected to provide useful guidance for designing composite materials with excellent gas sensing properties.展开更多
基金Projects(60806032,20975107) supported by the National Natural Science Foundation of ChinaProject(2009R10064) supported by the Scientific Research Foundation for the Returned Overseas Chinese Scholars of Education Ministry,China+2 种基金 Project(2009R10064) supported by "Qianjiang Talent Program"Projects(2009A610058,2009A610030) supported by the Ningbo Natural Science Foundation,ChinaProject supported by K.C.WONG Magna Fund in Ningbo University,China
文摘SnO2 nano particles with various Pd-doping concentrations were prepared using a template-free hydrothermal method.The effects of Pd doping on the crystal structure,morphology,microstructure,thermal stability and surface chemistry of these nano particles were characterized by transmission electron microscope,X-ray diffractometer and X-ray photoelectron spectroscope respectively.It was observed that Pd-doping had little effect on the grain sizes of the obtained SnO2 nano particles during the hydrothermal route.During thermal annealing,Pd-doping could restrain the growth of grain sizes below 500℃ while the grain growth was promoted when the temperature increased to above 700℃.XPS results revealed that Pd existed in three chemical states in the as-synthesized sample as Pd^0,Pd^2＋ and Pd^4＋,respectively.Pd^4＋ was the main state which was responsible for improving the gas-sensing property.The optimal Pd-doping concentration for better gas-sensing property and thermal stability was 2.0%-2.5% （mole fraction）.
基金financially supported by the National Natural Science Foundation of China(No.20871071)the Science and Technology Commission Foundation of Tianjin(No.09JCYBJC03600 and 10JCYBJC03900)
文摘Polythiophene/WO3（PTP/WO3）organic-inorganic hybrids were synthesized by an in situ chemical oxidative polymerization method,and char- acterized by X-ray diffraction（XRD）,transmission electron microscopy（TEM）and thermo-gravimetric analysis（TGA）.The Polythiophene/ WO3 hybrids have higher thermal stability than pure polythiophene,which is beneficial to potential application as chemical sensors.Gas sensing measurements demonstrate that the gas sensor based on the Polythiophene/WO3 hybrids has high response and good selectivity for de- tecting NO2 of ppm level at low temperature.Both the operating temperature and PTP contents have an influence on the response of PTP/WO3 hybrids to NO2.The 10 wt%PTP/WO3 hybrid showed the highest response at low operating temperature of 70-C.It is expected that the PTP/WO3 hybrids can be potentially used as gas sensor material for detecting the low concentration of NO2 at low temperature.
基金Project(51201052)supported by the National Natural Science Foundation of ChinaProject(2012RFQXG107)supported by the Innovative Talent Fund of Harbin City+1 种基金Project(E201056)supported by Natural Science Foundation of Heilongjiang Province of ChinaProject(1252G022)supported by the Program for Youth Academic Backbone in Heilongjiang Provincial University,China
文摘The high-temperature stabilization of ZnO nanorods synthesized by hydrothermal treatment was investigated. The structure and morphologies of ZnO nanorods were characterized by XRD and SEM, respectively. The thermal stability of ZnO nanorods was also detected by thermal gravity analyzing. Thermal annealing treatment results indicate that ZnO nanorods are fundamentally stable when annealing temperature is lower than 600 ℃. When annealing temperature is beyond 600℃, the diameters of ZnO nanorods obviously decrease and the aggravating tendency of nanorods between each other also increase. Annealing treatment can greatly influence the gas sensing properties of ZnO nanorods. Comparing with ZnO nanorods without annealing treatment, the gas sensing property of ZnO nanorods to H2 with concentration of 2.5×10-6 can increase from 2.22 to 3.56. ZnO nanorods annealed at 400 ℃ exhibit optimum gas sesing property to H2 gas.
基金Project(51402250)supported by the National Natural Science Foundation of ChinaProject(2015JJ4046)supported by the Hunan Provincial Natural Science Foundation of ChinaProject(14B168)supported by the Scientific Research Fund of Hunan Provincial Education Department,China
文摘Bi3.15Nd0.85Ti3O12 (BNdT) films were deposited on Pt/Ti/SiO2/Si(100) substrates by a metal organic decomposition (MOD)method, and annealed by a rapid thermal annealing process in oxygen atmosphere and in air, respectively. The crystalline structuresand morphologies of BNdT films were characterized by X-ray diffraction and field-emission scanning electron microscopy, and thegas sensing properties were measured by monitoring its resistance at different gas concentrations. The results indicate that the BNdTfilms annealed in air are of porous microstructure and rough surface, and the annealing atmosphere has great influence on gas sensingproperties. At an operating temperature of 100 °C, the BNdT films annealed in air are of high response value to 1×10?6 gaseousethanol, and the detecting limit is as low as 0.1×10?6. The corresponding response and recovery time is about 10 and 6 s, respectively.The results can offer useful guidelines for fabricating high performance ethanol sensors.
文摘Chemically synthesized ZnS thin film is found to be a good x-ray radiation sensor. We report the effect of annealing on the x-ray radiation detection sensitivity of a ZnS thin film synthesized by a chemical bath deposition technique. The chemically synthesized ZnS films are annealed at 333, 363 and 393K for 1 h. Structural analyses show that the lattice defects in the films decrease with annealing. Further, the band gap is also found to decrease from 3.38 to 3.21 eV after annealing at 393K. Current-voltage characteristics of the films are studied under dark and x-ray irradiation conditions. Due to the decrease of lattice defects and band gap, the conductivity under dark conditions is found to increase from 2.06 × 10^-6 to 1.69 × 10^-5 S/em, while that under x-ray irradiation increases from 4.13 × 10^-5 to 5.28 ×10^-5 S/cm. On the other hand, the x-ray radiation detection sensitivity of the films is found to decrease with annealing. This decrease of detection sensitivity is attributed to the decrease of the band gap as well as some structural and surface morphological changes occurring after annealing.
文摘A type of compact solution concentration sensor based on a microfiber with a nanoscale-structured film is proposed and demonstrated experimentally. Additional loss at different solution concentrations is calculated by means of the three-dimensional finite-difference time-domain （3D-FDTD） method. The microfiber is fabricated by using the flame-heated scanning technique. Nanoscale-structured film is coated on the microfiber surface, which is assembled as a sensing unit. The sensitivity of this kind of sensor increases with the decreasing diameters of the microfiber. When the diameter of the microfiber is 2 #m, a minimum concentration sensitivity of 1% （under 450s measuring time） is demonstrated in the experiment. Higher sensitivity can be attained when the solution concentration is higher. The sensing properties of this microfiber with the nanoscale-structured film may provide opportunities for new applications in optical sensing devices.
基金National Natural Science Foundation of China (No 59995520)
文摘Semiconductor-type TiO2 oxygen sensing thin films were synthesized using tetrabutyl titanate （Ti （OBu）4） as precursor and diethanolamine （DEA） as complexing agent by the sol-get process. The porous and oxygen sensing TiO2 films were obtained by the addition of polyethylene glycol （PEG）. The micrographs of scanning electron microscope （SEM） show that the pores of the sample about 400-600 nm in size with PEG（2 000 g/mol） are larger than those about 300 nm in size with PEG（ 1 000 g/mol）, while the density of pores is lower. The results also indicate that increasing the content of PEG properly is beneficial to the formation of porous structure. With the increasing content of PEG from 0 g to 2.5 g, the oxygen sensitivity increases from 330 to more than 1 000 at 800 ℃, from 170 to more than 1 000 at 900℃, and the response time to O2 and H2 are about 1.5 s and less than 1s, respectively.
文摘The mechanical and strain sensing properties of carbon nanotube composite yarns （CNTs/PDMS） with different weight percent of PDMS were studied. The CNT/PDMS composite yarn was prepared by infiltration method. Pictures of diameter of CNT composite yarns were obtained though polarized light microscope. Resistance change values of CNT composites under stretching were obtained though the single fiber strength tester and digital multimeter and related mechanical, electrical software. The changes of mechanical properties. electrical properties and sensing pertbrmance of pure and composite CNT yarns were discussed and analyzed. The results showed that the strength of CNT yarn declined after it was composited with PDMS polymer. In addition, the conductivity and sensing performance of CNT yarns improved significantly. The most suitable CNT composite yam occurs at PDMS mass fraction of 1% when strength and sensing properties were all considered.
基金supported by the National Natural Science Foundation of China(Nos.61875026 and 61505017)the Foundation and Cutting-Edge Research Projects of the Chongqing Science and Technology Commission(No.cstc2018jcyjAX0122)the Graduate Student Innovation Program of the Chongqing University of Technology(No.ycx2018238)
文摘We demonstrate a fiber refractive index（RI） sensor based on an excessively tilted fiber grating（ExTFG）immobilized by large-size plasmonic gold nanoshells（GNSs）. The GNSs are covalently linked on ExTFG surface.Experimental results demonstrate that both the intensity of the transverse magnetic（TM） and transverse electric（TE） modes of ExTFG are significantly modulated by the localized surface plasmon resonance（LSPR） of GNSs due to the wide-range absorption band. The wavelength RI sensitivities of the TM and TE modes in the low RI range of 1.333–1.379 are improved by ～25% and ～14% after GNSs immobilization, respectively, and the intensity RI sensitivities are ～599%/RIU and ～486%/RIU, respectively.
基金National 863 Program (No. 2007AA061401) for financial support
文摘ZnO thin films prepared by using quantitative filter paper as a template and Zn（CH3CO2）2.2H2O ethanol precursor solution were characterized by scanning electron microscopy （SEM） and X-ray diffraction （XRD）. The effects of sample calcination temperature, precursor concentration and filter paper types were studied, and the growth process was investigated by infra-red （IR） spectroscopy and thermogravimettic analysis/differential thermal analysis （TGA/DTA）. The results show that samples soaked in a 1.5 mol/L Zn（CH3 CO2）2.2H2O ethanol solution and calcined at 600 ℃ yield ZnO films of uniform particle size, approximately 30, 40 and 50 nm. for fast-, medium- and slow-speed filter papers, respectively. The formaldehyde gas sensing properties of the ZnO nanoparticles were tested, showing that the material prepared from fast-speed filter paper has a higher response to 120-205 ppm formaldehyde at 400 ℃ than that prepared from medium- or slow-sneed paper, which depends on the narticle size.
文摘The thin film gas sensors of bismuth iron molybdate were prepared by ion beam sputtering technique. The prototype gas sensors studied have high sensitivity and selectivity to reducing gases, such as ethanol vapor, show a long term stability of response under most operating conditions and insensitivity to atmospheric humidity, and respond quickly comparing to traditional sintered gas sensors. The crystallographic structure and phase composition of these thin films were investigated with XRD, XPS and SEM techniques.
基金supported financially by the National Natural Science Foundation of China(52205308,22208120)the China Postdoctoral Science Foundation(2022M711300).
文摘Flexible sensors,a class of devices that can convert external mechanical or physical signals into changes in resistance,capacitance,or current,have developed rapidly since the concept was first proposed.Due to the special properties and naturally occurring excellent microstructures of biomaterials,it can provide more desirable properties to flexible devices.This paper systematically discusses the commonly used biomaterials for bio-based flexible devices in current research applications and their deployment in preparing flexible sensors with different mechanisms.According to the characteristics of other properties and application requirements of biomaterials,the mechanisms of their functional group properties,special microstructures,and bonding interactions in the context of various sensing applications are presented in detail.The practical application scenarios of biomaterial-based flexible devices are highlighted,including human-computer interactions,energy harvesting,wound healing,and related biomedical applications.Finally,this paper also reviews in detail the limitations of biobased materials in the construction of flexible devices and presents challenges and trends in the development of biobased flexible sensors,as well as to better explore the properties of biomaterials to ensure functional synergy within the composite materials.
基金the National Natural Science Foundation of China(No.20771095)He'nan Outstanding Youth Science Fund(No.0612002700)is gratefully acknowledged.
文摘We report the structural characterization and proposed formation mechanism of honeycomb-like ZnO conglomerations fabricated by direct precipitation method. X-ray diffraction （XRD）, energy-disperse X-ray spectrometry （EDS）, scanning electron microscopy （SEM） showed that the as-prepared ZnO calcined at 700 ℃ were micron sphere particles with honeycomb-like structure. In the UV-vis absorbing spectrum, it was observed that there is a new additional absorption band at 260 nm, and it was speculated that the absorption may be caused by defects on the surface and interface of honeycomb-like ZnO. The as-products showed high sensitivity and short response time to sulfured hydrogen gas. These results demonstrate that honeycomb-like ZnO conglomerations are very promising materials for fabricating H2S gas sensors.
基金The project is supported by the National Natural Science Foundation of China （60074031, 60474052）.
文摘Capacitive humidity sensors were made of nanometer barium titanate.The pellets were prepared under different pressures between 3920N to 7850N force.The capacitance changes in three orders of magnitude in the relative humidity range of 10%～98%,indicating high humidity sensitivity of the sensors.At a certain measuring frequency,the capacitance of the sensors increases as increasing of the preparation pressure,while the sensitivity of the sensors basically remains the same.The frequencies corresponding to the peaks of the dielectric loss of the sensors move to the higher frequency direction as increasing of the relative humidity.At a certain humidity,the frequencies corresponding to the peaks of the dielectric loss move to the higher frequency direction as increasing of the preparation pressure.
文摘A series of aluminium-containing α-type hydrated zirconium hydrogen phosphates,Zr_(1-x)Alx (H_(1+x/2)PO_4 )_2 with x=0-0.06,were hydrothermally synthesized and characterizedby means of X-ray diffraction,differential thermal analysis and thermogravimetric analysis.The proton conductivity,1.2×10￣(-4) S·cm￣(-1)at 180℃ was found in Zr_(0.98)Al_(0.02)(H_(1.01)PO_4)_2·H_2O.Humidity-sensing measurements were carried out at 120℃ and 140℃ respectively.Even a limited substitution of Al for Zr can enhance both proton conductivity and humidity sensitivity.
文摘Nanocrystalline tin oxide samples were prepared by using Sn2 （NH4 ）2 （C2O4）3 as the precursor. The thermal decompositions were respectively conducted at 250,450 and 650 ℃. TG-DTA, XRD, TEM, FTIR were used to characterize the samples. The indirect heating sensors by using these materials as sensitive bodies were fabricated on an alumina tube with Au electrodes and platinum wires. Sensing properties of these sensors were investigated. It was found that the tin oxide sample obtained by thermal decomposition at 450 ℃ has a higher sensitivity to C2H5OH and a higher selectivity to hexane and ammonia than those obtained via the conventional precipitate method and the working temperatures needed were greatly decreased.
文摘A γ - type of layered zirconium hydrogen phosphate, Zr(HPO 4) 2·2H 2O( γ ZrP), was synthesized under hydrothermal conditions and characterized by powder X ray diffraction and thermogravimetric analysis. The temperature dependence of the proton conductivity in γ ZrP was investigated in a temperature range of 23￣413 ℃ by ac impedance spectroscopy. The variation of the conductivity with water loss and phase transitions was observed. The best proton conductivity in γ ZrP is 6×10 -4 S·cm -1 at 60 ℃. The proton conductivities in the dehydrated sample are ￣10 -5 at 150 ℃ and ￣10 -4 S·cm -1 at 350 ℃, respectively. The conductivities as a function of humidity in the temperature range of 120￣200 ℃ were measured.
文摘Carbon nanotube(CNT)yarns with adjustable diameters were manufactured by twisting CNT films with varied twists.Different from traditional CNT fibers,CNT yarns exhibited a larger diameter(423μm)and a higher tensile force(1988 cN).The results showed that CNT yarns with the twist angle of 35°exhibited the highest conductivity(886 S/cm)and the highest tensile strain(35%).
基金financially supported by Hunan Provincial Natural Science Foundation of China(No.2018JJ2404)the Scientific Research Foundation of Hunan Provincial Education Department(Nos.19A475 and 19C1739)Hunan Science and Technology Plan Program(No.2019RS1056)。
文摘Due to its unique physical,chemical and surface electronic properties,molybdenum disulfide(MoS_(2))nanosheets open up a new avenue for nitrogen dioxide(NO2)detection at room temperature.Nevertheless,the gas sensing properties of pure MoS_(2) nanosheets are inevitably degenerated by the adsorption of atmospheric oxygen,which results in weak stability for MoS_(2)-based gas sensors.Reducing surface defects and constructing heterojunctions may be effective strategies to improve the gas sensing properties of MoS_(2) nanosheets.In this work,we design a novel nanocomposite based on MoS_(2) nanosheets decorated with tin disulfide(SnS_(2))nanoparticles(MoS_(2)/SnS_(2))via combining the mechanical exfoliation method with the facile hydrothermal method.The experimental results indicate that,after surfaces decoration with SnS_(2) nanoparticles,the as-prepared gas sensor based on MoS_(2)/SnS_(2) nanocomposites exhibits reliable long-term stability with the maximum response value drift of less than 3%at room temperature.Moreover,the MoS_(2)/SnS_(2) sensor also possesses desirable gas sensing properties upon NO_(2) at room temperature,such as high sensitivity,rapid response/recovery speed(28 s/3 s,5×10^(-6) NO_(2)),satisfactory selectivity,favorable repeatability and reversibility.The improved gas sensing properties of MoS_(2)/SnS_(2) nanocomposites can be attributed to the unique electronic properties of MoS 2 nanosheets with the fewer layers structure and the competitive adsorption effect of SnS_(2) nanoparticles.This work elucidates that SnS_(2) nanoparticles serving as an effective antioxidative decoration can promote the stability of MoS_(2) nanosheets,providing a promising approach to achieve high-stability NO2 gas sensors at room temperature.
基金supported by Hunan Provincial Natural Science Foundation of China(No.2018JJ2404)Scientific Research Foundation of Hunan Provincial Education Department(Nos.19A475,19C1739)Hunan Science and Technology Plan Program(No.2019RS1056)。
文摘MoS2,acting as a promising gas sensing material,has shown huge potential in monitoring of toxic and harmful gases at room temperature.However,MoS2-based gas sensors still suffer from poor gas sensing performance such as poor sensitivity,long response time.Constructing the hete ro structure is an effective approach to improve gas-sensing performance of MoS2.Herein,PbS@MoS2 composites synthesized by mechanical exfoliation combining with wet-chemical precipitation are used to investigate its performance in detecting NO2 at room temperature.The response value of PbS@MoS2 gas sensor against NO2 is significantly improved compared with the pure MoS2 gas sensor.At the same time,the modification with PbS also accelerates the response speed of MoS2,and the response time is almost reduced by two orders of magnitude,from hundreds of seconds to less than ten seconds.The enhanced response value and fast response time are mainly benefited from the modulation effect of NO2 to PbS@MoS2 heterostructure and the mechanically exfoliated MoS2 surface with few defects.This work can be expected to provide useful guidance for designing composite materials with excellent gas sensing properties.
