Fabrication of a room temperature hydrogen sensor based on thin film of single-walled carbon nanotubes doped with palladium nanoparticles

A new sensor for the detection of hydrogen at parts per million (ppm) levels was fabricated by coating a thin film of palladium-doped activated single-walled carbon nanotube on the inner wall of a glass tube. The response of the sensor was based on the changes in the impedance of the sensor upon the adsorption of hydrogen molecules. The linear dynamic range of the sensor was from 1 to 50?ppm. The relative standard deviation of six replicate analyses of 5?ppm of H₂ was 2.1% and the limit of detection was 0.73?ppm for H₂ species. Humidity, methane and hydrogen sulphide did not have any serious effect on hydrogen recognition. Also, no interfering effect was observed when 20-fold excess (mass/mass) of carbon dioxide or carbon monoxide was present with hydrogen.     

CdS/Nd2O3 and CdSe/Nd2O3 thin film transistors

Thin film transistors were grown by the multiple-pumpdown method of vacuum deposition. The behaviour of CdS and CdSe thin film transistors with Nd₂O₃ as the gate insulator was studied, and the various characteristics and parameters of the fabricated devices were determined. The performance of CdSe-Nd₂O₃ thin film transistors was found to be superior to that of CdS/Nd₂O₃ thin film transistors. The devices showed little change over a period of 4 months.     

Nanostructured ZnFe2O4 thick film as room temperature liquefied petroleum gas sensor

In the present work, thick film of nanostructured zinc ferrite was prepared by screen printing method and its liquefied petroleum gas (LPG) sensing properties were investigated. The structural and surface morphological characterisations of the sample were analysed by means of X-ray diffraction (XRD) and scanning electron microscopy (SEM). The minimum crystallite size of ZnFe₂O₄ calculated from Scherrer's formula is found to be 4 nm. SEM images exhibit the porous nature of the sensing material with a number of active sites. Optical characterisation of the film was carried out by ultraviolet–visible spectrophotometer. The estimated value of band gap of the film was found 1.91 eV. The LPG sensing properties of the zinc ferrite film were investigated at room temperature for different vol.% of LPG. The variations in electrical resistance of the film were measured with the exposure of LPG as a function of time. The maximum values of sensitivity and percentage sensor response were found 16 and 1785, respectively, for 5 vol.% of LPG. These experimental results show that nanostructured zinc ferrite is a promising material for LPG sensor.     

CuAl2O4掺杂改性TiO2薄膜的制备与可见光催化性能研究

采用溶胶-凝胶方法在玻璃基片上制备了CuAl2O4掺杂改性的复合薄膜．研究了CuAl2O4的掺杂量、光照时间、薄膜厚度对TiO2复合薄膜光催化性能的影响，利用可见-紫外分光光度计测定酸性红B降解前后516nm处的吸光度，依此计算出薄膜对染料的降解率．借助于紫外可见光谱、X射线衍射、接触角测定仪等研究了薄膜的结构与性能．结果表明：随着CuAl2O4掺杂量的增加，TiO2复合薄膜对酸性红B水溶液的可见光降解脱色率增大．采用吸收光谱确定了CuAl2O4掺杂量为0％、0．5％、1％、1．5％％（摩尔分数）的TiO2复合薄膜的激发极限波长，分别是350、370、380、430nm，吸收边向可见区红移了20-80nm，可见光吸收范围明显扩大．     

Room temperature electroluminescence from arsenic doped p-type ZnO nanowires/n-ZnO thin film homojunction light-emitting diode

The highly arrayed arsenic doped p-ZnO nanowires/n-ZnO thin film homojunction light-emitting diode was fabricated on semi-insulated Si substrate. The homojunction was consisted of high-quality n-ZnO thin film grown by metal–organic chemical vapor deposition technology following arsenic doped ZnO nanowires grown by chemical vapor deposition. The device shows good rectification characteristic with a turn-on voltage of ~4.8 V and reverse breakdown voltage of ~18 V. Moreover, two distinct electroluminescence bands centered at 2.35 and 3.18 eV are detected from this device under forward bias at room temperature.     

Highly selective NH3 gas sensor based on polypyrrole/Ti3C2Tx nanocomposites operating at room temperature

Journal of Materials Science: Materials in Electronics - Semiconducting nanomaterials with different sizes and shapes have wide applications in the field of electronics, and one of the key pathway...     

Ammonia gas sensor based on PPy/ZnSnO3 nanocomposites

In this paper, Zinc stannate (ZnSnO₃) nanoparticles were synthesized by a sol-gel method. Then, polypyrrole (PPy)/ZnSnO₃ nanocomposites were prepared by a simple in situ chemical polymerization method. By means of X-ray diffraction, Fourier transform infrared and scanning electron microscopy, the microstructure of PPy/ZnSnO₃ nanocomposites was characterized. The XRD patterns indicate that ZnSnO₃ nanoparticles have a perovskite phase with an orthorhombic structure, and incorporation of PPy did not change the crystalline structure of ZnSnO₃. The PPy was evenly dispersed on the surface of ZnSnO₃ particles, which was endorsed by FTIR spectral analyses. SEM images indicate that the PPy was evenly dispersed on the surface of ZnSnO₃ particles without apparent agglomeration. We found that the nanocomposites exhibited a higher response to NH₃ gas.     

Wide temperature range negative temperature coefficient thermistor of a Y2O3 modified LaMnO3 bilayer thin film

Journal of Materials Science: Materials in Electronics - A bilayer architecture was established to modify the negative temperature coefficient (NTC) properties of LaMnO3 thin films. By...     

Reliable high temperature,high humidity flexible thin film encapsulation using Al2O3/MgO nanolaminates for flexible OLEDs

Since most organic materials are very sensitive to moisture and oxygen, organic light emitting diodes (OLEDs) require an encapsulation layer to protect the active layer from these gases. Since light, flexible and portable OLEDs are being employed in more diverse climates and environmental conditions, the OLED encapsulation layer must retain robust mechanical properties and stability in high temperature/high humidity conditions. Al₂O₃ films have demonstrated excellent barrier performance, but they readily hydrolyze when exposed to prolonged harsh environments. In this study, we fabricated a thin film encapsulation (TFE) film that was resistant to hydrolysis, using Al₂O₃/MgO (AM) nanolaminates. MgO has superior resistance to harsh environments, and the aluminate phase generated by the chemical reaction of Al₂O₃ and MgO provided excellent barrier performance, even after storage in harsh conditions. A multi-barrier fabricated using the AM nanolaminate showed excellent barrier performance, close to the level required by OLEDs. It did not significantly deteriorate even after a bending test of 1,000 iterations at 0.63% strain. After 1,000 cycle of bending, the electrical properties of the passivated OLEDs were not significantly degraded at shelf-lifetime test where the fabricated device was stored for 50 days in a harsh environment of 60 °C, 90% relative humidity. The multi-barrier shows the best performance compared to previous studies on flexible encapsulation that can be used in harsh environments.

     

Room temperature multiferroic properties of (Bi0.95La0.05)(Fe0.97Mn0.03)O3/NiFe2O4 double layered thin film

(Bi_0.95La_0.05)(Fe_0.97Mn_0.03)O₃/NiFe₂O₄ double layered thin film was prepared on a Pt(111)/Ti/SiO₂/Si(100) substrate by a chemical solution deposition method. X-ray diffraction and Raman scattering spectroscopy studies confirmed the formation of the distorted rhombohedral perovskite and the inverse spinel cubic structures for the (Bi_0.95La_0.05)(Fe_0.97Mn_0.03)O₃/NiFe₂O₄ double layered thin film. The (Bi_0.95La_0.05)(Fe_0.97Mn_0.03)O₃/NiFe₂O₄ double layered thin film exhibited well saturated ferromagnetic (2 M_r of 18.1 emu/cm³ and 2H_c of 0.32 kOe at 20 kOe) and ferroelectric (2P_r of 60 μC/cm² and 2E_c of 813 kV/cm at 866 kV/cm) hysteresis loops with low order of leakage current density (4.5 × 10⁻⁶ A/cm² at an applied electric field of 100 kV/cm), which suggest the ferroelectric and ferromagnetic multi-layers applications in real devices.     

Sensitive and selective imprinted electrochemical sensor for p-nitrophenol based on ZnO nanoparticles/carbon nanotubes doped chitosan film

A sensitive and selective molecularly imprinted electrochemical sensor for p-nitrophenol detection has been developed based on ZnO nanoparticles/multiwall carbon nanotubes (MWNTs)-chitosan (CTS) nanocomposite. This nanocomposite was dripped onto an indium tin oxide electrode and then imprinted sol-gel solution was electrodeposited onto the modified electrode to construct the proposed sensor. The morphologies and electrochemical behaviors of the imprinted sensor were characterized by scanning electron microscope, X-ray diffraction, electrochemical impedance spectroscopy, square wave voltammetry and cyclic voltammetry. The imprinted sensor displayed excellent selectivity towards the target molecule p-nitrophenol. Meanwhile, the introduced nanocomposite increased surface area and active sites for electron transfer, thus remarkably enhancing the sensitivity of the imprinted sensor. Under optimal conditions, the peak current was linear to p-nitrophenol concentration ranging from 1.0 × 10^− 8 to 2.0 × 10^− 4 mol·L^− 1 with a detection limits of 1.0 × 10^− 9 mol·L^− 1 (S/N = 3). This proposed sensor was applied to the detection of p-nitrophenol in various water samples successfully.     

Nanoporous TiO2 thin film based conductometric H2 sensor

Nanoporous titanium dioxide (TiO₂) based conductometric sensors have been fabricated and their sensitivity to hydrogen (H₂) gas has been investigated. A filtered cathodic vacuum arc (FCVA) system was used to deposit ultra-smooth Ti thin films on a transducer having patterned inter-digital gold electrodes (IDTs). Nanoporous TiO₂ films were obtained by anodization of the titanium (Ti) thin films using a neutral 0.5% (wt) NH₄F in ethylene glycol solution at 5 V for 1 h. After anodization, the films were annealed at 600 °C for 8 h to convert the remaining Ti into TiO₂. The scanning electron microscopy (SEM) images revealed that the average diameters of the nanopores are in the range of 20 to 25 nm. The sensor was exposed to different concentrations of H₂ in synthetic air at operating temperatures between 100 °C and 300 °C. The sensor responded with a highest sensitivity of 1.24 to 1% of H₂ gas at 225 °C.     

Copper and iron based thin film nanocomposites prepared by radio-frequency sputtering. Part II: elaboration and characterization of oxide/oxide thin film nanocomposites using controlled ex-situ oxidation process

CuO/CuFe₂O₄ thin films were obtained on glass substrate by ex situ oxidation in air at 450 °C for 12 h from various starting metal/oxide nanocomposites by radio-frequency sputtering technique. The structure and microstructure of the films were examined using grazing incidence X-ray diffraction, Raman spectroscopy, scanning and transmission electron microscopies, X-ray photoelectron spectroscopy, and electron probe microanalysis. These studies reveal that a self-organized bi-layered microstructure with CuO (surface layer) and CuFe₂O₄ (heart layer) was systematically obtained. Due to the porosity of the upper layer formed during annealing, an increase in total thickness of the film was observed and is directly correlated to the oxidation of the metallic copper content initially present in the as-deposited sample. A self-organization in two stacked layers CuO/CuFe₂O₄ with various void fractions ranging from 0 to 41 % can be obtained by controlling the as-deposited elaboration step described in the part I of this paper. The highest porosities were observed for films deposited at low argon pressure and low target-to-substrate distance. Due to their specific self-organization in p- and n-type layers associated with their high porosity, such structured films exhibited the best electrical sensitivity to CO₂ gas sensing. The obtained results demonstrated the importance of microstructure control to improve the response of sensing layers.     

Novel magnetically separable g-C3N4/Fe3O4/Ag3PO4/Co3O4 nanocomposites: Visible-light-driven photocatalysts with highly enhanced activity

In this study, a series of novel quaternary g-C₃N₄/Fe₃O₄/Ag₃PO₄/Co₃O₄ nanocomposites were fabricated. The prepared nanocomposites were characterized by XRD, EDX, SEM, TEM, UV-DRS, FT-IR, PL, TG, and VSM methods to gain insight about structure, purity, morphology, optical, thermal, and magnetic properties. Photocatalytic activity of the samples was investigated under visible-light irradiation by degradations of rhodamine B, methylene blue, methyl orange, and phenol as four organic pollutants. The highest photocatalytic degradation efficiency was observed when the sample calcined at 300 °C for 2 h with 20 wt% of Co₃O₄. The photocatalytic activity of this nanocomposite is almost 16.8, 15.7, 4.6, and 5.1 times higher than those of the g-C₃N₄, g-C₃N₄/Fe₃O₄, g-C₃N₄/Fe₃O₄/Ag₃PO₄ (20%), and g-C₃N₄/Fe₃O₄/Co₃O₄ (20%) samples in photodegradation of rhodamine B, respectively. Finally, on the basis of the energy band positions, the mechanism of enhanced photocatalytic activity was discussed.     

Y掺杂Mn3O4/石墨烯复合材料的电化学性能

通过水热法在不同反应温度、一定反应时间条件下制备用于超级电容器的Mn3O4,同时实现Y的掺杂和复合石墨烯。通过X射线衍射(XRD)、扫描电子显微镜(SEM)和电化学工作站对样品的形貌、结构与电化学性能进行分析,发现其与标准PDF卡89-4837相吻合,为单一相的Mn3O4,属四方晶系,空间群为I41/amd(No.141)。所制得Mn3O4为棒状颗粒。Y掺杂含量为5%时Y-Mn3O4的比电容可以达到89 F·g^-1,Y-Mn3O4/石墨烯复合材料的比电容可达到267F·g^-1,并且它们的循环伏安曲线为矩形形状,说明Y的掺杂和石墨烯的负载协同提高了Mn3O4的电化学性能。     

Copper and iron based thin film nanocomposites prepared by radio frequency sputtering. Part I: elaboration and characterization of metal/oxide thin film nanocomposites using controlled in situ reduction process

Copper and iron based thin films were prepared on glass substrate by radio-frequency sputtering technique from a delafossite CuFeO₂ target. After deposition, the structure and microstructure of the films were examined using grazing incidence X-ray diffraction, Raman spectroscopy, electron probe micro-analysis and transmission electron microscopy coupled with EDS mapping. Target to substrate distance and sputtering gas pressure were varied to obtain films having different amount and distribution of copper nanoparticles and different composition of oxide matrix. The overall reaction process, which starts from CuFeO₂ target and ends with the formation of films having different proportion of copper, copper oxide and iron oxide, was described by a combination of balanced chemical reactions. A direct relationship between the composition of the metal/oxide nanocomposite thin film and the sputtering parameters was established. This empirical relationship can further be used to control the composition of the metal/oxide nanocomposite thin films, i.e. the in situ reduction of copper ions in the target.     

Electromagnetic wave absorption properties of mesoporous Fe3O4/C nanocomposites

In this work, the mesoporous Fe₃O₄/C nanocomposites with a yolk-shell structure (Fe₃O₄@void@C) were prepared by a silica-assisted strategy, and their microstructure, magnetic properties, and microwave absorption were studied in detail. The BET surface area and the total pore volume of Fe₃O₄@void@C are 171.5 m² g⁻¹ and 0.19 cm³ g⁻¹, respectively. The composites show a saturation magnetization of 35.4 emu/g and reduced hysteresis loss at room temperature. The Fe₃O₄@void@C nanocomposites exhibit the obvious complementarities between complex permittivity and permeability. A minimum reflection loss value of −18.1 dB was obtained for the absorber thickness reaching 2.0 mm, and even the Fe₃O₄@void@C nanocomposites possess a lower reflection loss of-10 dB under 2 GHz bandwidth. We believe that the investigations on the Fe₃O₄@void@C nanocomposite open up a route to develop a new type of composite, which is considered as a promising candidate for microwave absorber.     

Fe3O4/聚苯胺纳米复合材料高能球磨法制备及其性能研究

以Fe3O4粉体及导电聚苯胺为原料,用高能球磨法制备Fe3O4／聚苯胺纳米复合材料,用Moessbauer谱、XRD、FTIR、VSM等方法对样品进行表征。结果表明随着球磨时间的增加,Fe3O4的粒径迅速减小到纳米量级;Fe3O4表面与聚苯胺作用生成了某种顺磁性物质;同时有少量的α—Fe3O4生成;复合物中Fe3O4颗粒A、B晶位中Fe的含量发生了明显的变化。复合物的电磁性能也明显发生了改变。