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Cellulose is a common natural polymer, and the surface of the nanocellulose has a large number of hydroxyl groups, which is possible used to precipitate metal salts to obtain the precursors, and then calcine to get the corresponding metal oxides. In this paper, tin dioxide (SnO2) nanoparticles were prepared with different amounts of nanocellulose by a low-temperature hydrothermal method (60°C) followed by calcination. The obtained material was verified to be impurity-free SnO2 nanoparticles by various types of physical phase analysis and morphological characterization. The SnO2 nanoparticles obtained from 50 mg nanocellulose exhibited a significantly improved sensing performance, and the response toward SO2 at 1 ppm was 4.68. In addition, multiple performance tests were conducted on the obtained gas sensor, and it was finally found to have a good gas sensitivity and an excellent selectivity. The repeatability and stability also presented preferable results. Additionally, the sensing mechanism was discussed. The prepared SnO2 sensor is promising for the detection of SO2 due to its high sensitivity and selectivity. [ABSTRACT FROM AUTHOR]

[Display omitted] • Synthesized 10 nm SnO 2 nanoparticles using a simple, environmentally friendly approach at low temperature. • The nanomaterials possess a large specific surface area of 58.17 m2/g and a substantial pore volume of 0.1678 cm3/g. • The gas sensor demonstrates rapid response to 3 ppm NO 2 at room temperature under UV light. • The sensor remains sensitive to NO 2 even at room temperature without UV activation. Amino acids, as naturally occurring small molecules, have shown potential as materials for gas sensor-assisted synthesis. In this study, we present a novel method based on amino acid templates for the assisted synthesis of small-sized SnO 2 nanoparticles at a low temperature of 140℃. Specifically, the Gly/SnO 2 -2 sample, synthesized with 20 % wt glycine incorporation, exhibited a sensitivity of 22.74 towards a low concentration (3 ppm) of NO 2 under UV irradiation at 365 nm, with a rapid response/recovery time of 12/11 s. Remarkably, even under UV-free room-temperature conditions, the sensor continued to respond to NO 2. Crystal structure analysis of the material was conducted through scanning electron microscopy (SEM) and transmission electron microscopy (TEM), revealing excellent crystallinity with a particle size of approximately 10 nm. Additionally, BET characterization indicated a well-defined spatial structure with a specific surface area of 58.17 m2/g. Experimental data further demonstrated that the Gly/SnO 2 -2 displayed good selectivity, reproducibility, and stability. These findings underscore the potential of amino acid templating in advancing gas sensing technologies, offering avenues for the development of highly efficient sensing materials. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ag-doped ZnCo 2 O 4 /FF composites were synthesized by a facile method. • The Ag-ZCO/FF composites have good formaldehyde gas-sensitive properties at 175 ℃. • Compared with reported ZnCo 2 O 4 materials, the Ag-ZCO/FF materials in this study showed better response at lower concentration. Cobalt-containing spinel oxides are highly active materials for gas sensing and have shown promise in various applications. In this study, we prepared a series of gas-sensitive composites by doping Ag into ZnCo 2 O 4 /Phenylalanine dipeptide (ZCO/FF) and investigated their gas sensitivity to formaldehyde. The experiments showed that the response of ZCO/FF-3 wt%Ag to 20 ppm formaldehyde was 23 at an optimum operating temperature of 175 °C. Further experimental data show that the sensor has excellent selectivity and stability. These results provide basic knowledge for the practical use of spinel oxide gas sensors. [ABSTRACT FROM AUTHOR]

This present study reported a high-performance gas sensor, based on In2O3/ZnO composite material modified by polypeptides, with a high sensibility to NO2, where the In2O3/ZnO composite was prepared by a one-step hydrothermal method. A series of results through material characterization technologies showed the addition of polypeptides can effectively change the morphology and size of In2O3/ZnO crystals, and effectively improve the sensing performance of the gas sensors. Due to the single shape and small size, In2O3/ZnO composite modified by polypeptides increased the active sites on the surface. At the same time, the gas sensing properties of four different ratios of polypeptide-modified In2O3/ZnO gas sensors were tested. It was found that the In2O3/ZnO-10 material showed the highest response, excellent selectivity, and good stability at room temperature under UV light. In addition, the response of the In2O3/ZnO-10 gas sensor showed a strong linear relationship with the NO2 gas concentration. When the NO2 gas concentration was 20 ppm, the response time was as quick as 19 s, and the recovery time was 57 s. Finally, based on the obtained experimental characterization results and energy band structure analysis, a possible gas sensing mechanism is proposed. [ABSTRACT FROM AUTHOR]

Nitrogen dioxide (NO 2) is a significant air pollutant with a notable environmental impact, necessitating precise monitoring. However, most existing NO 2 sensing materials exhibit low sensitivity and require high-temperature operation. In this study, we employed a hydrothermal and co-precipitation method to synthesize a novel ternary nanocomposite, In 2 O 3 /SnO 2 nanoparticles (NPs)/fluorine-doped carbon quantum dots (F-CDs). By varying the mass ratio of In 2 O 3 to SnO 2 NPs, we investigated the gas-sensing performance of the composite towards NO 2. The results demonstrate that when the ratio of SnO 2 and In 2 O 3 reaches to 1 : 2, the 2-In 2 O 3 /SnO 2 /F-CDs gas sensor exhibited the highest response, excellent selectivity, and remarkable stability under ultraviolet (UV) light irradiation at room temperature (∼25 °C). Furthermore, the response of the 2-In 2 O 3 /SnO 2 /F-CDs gas sensor displayed a strong linear relationship with the concentration of NO 2 gas. At a NO 2 gas concentration of 3 ppm, the sensitivity was 238, which is significantly higher than that of In 2 O 3 /SnO 2 NPs and In 2 O 3 sensors. The response time and recovery time were measured at 62 s and 33 s, respectively. Finally, based on experimental characterization results and band structure analysis, we confirmed the promising effects of ternary nanocomposite in enhancing gas sensing. [ABSTRACT FROM AUTHOR]

To enhance the poor sensing capabilities of traditional p-type metal oxide semiconductor sensors, a novel gas sensor was designed with Co3O4/CuO heterostructure modified by glutathione (GSH)-reduced gold (Au), which was characterized by different analyses. The experiments showed that the 0.5 wt.% Au–Co3O4/CuO gas sensor exhibited excellent sensing performance with a response value of up to 28.3 for 3 ppm NO2 at a relatively low operating temperature (1 0 0 ∘ C). Besides, it demonstrated a linear relationship between detection concentration and response value, displayed good selectivity for NO2, showcased stability and exhibited repeatability. Moreover, the sensor revealed the ability to resist humidity at the optimal temperature. Finally, we proposed a gas sensing mechanism to explain the enhanced NO2 detection performance of the sensor, attributed to the heterojunction structure between Co3O4/CuO and the catalytic properties of Au. This led to an increase in adsorbed oxygen, as confirmed by XPS characterization. Therefore, the 0.5 wt.% Au–Co3O4/CuO ternary nanocomposite gas sensor is deemed to be a highly effective sensing material that can be utilized to detect NO2 gas in real-life applications. Au-Co3O4/CuO ternary nanocomposites were successfully fabricated by a one-step hydrothermal method with a subsequent two-step sintering method. The experiments showed that the 0.5 wt% Co3O4/CuO gas sensor exhibited excellent sensing performance with a response value of up to 28.3 for 3 ppm NO2 at a relatively low operating temperature (100∘C). Thus, it is deemed to be a highly effective sensing material that can be utilized to detect NO2 gas for real-life applications. [ABSTRACT FROM AUTHOR]

Triboelectric nanogenerators (TENGs) have attracted many research endeavors as self-powered sensors for force, velocity, and gas detection based on solid–solid or solid–air interactions. Recently, triboelectrification at liquid–solid interfaces also showed intriguing capability in converting physical contacts into electricity. Here, we report a self-powered triboelectric sensor for liquid chemical sensing based on liquid–solid electrification. As a liquid droplet passed across the tribo-negative sensor surface, the induced surface charge balanced with the electrical double layer charge in the liquid droplet. The competition between the double layer charge and surface charge generated characteristic positive and negative voltage spikes, which may serve as a "binary feature" to identify the chemical compound. The sensor showed distinct sensitivity to three amino acids including glycine, lysine and phenylalanine as a function of their concentration. The versatile sensing ability was further demonstrated on several other inorganic and organic chemical compounds dissolved in DI water. This work demonstrated a promising sensing application based on the triboelectrification principle for biofluid sensor development. [ABSTRACT FROM AUTHOR]

Nitrogen dioxide (NO2) is a major pollutant that poses significant risks to sustainable human life. As a result, a growing focus has been placed on the development of highly selective and sensitive gas sensors for NO2. Traditional cutting-edge non-organic NO2 gas detectors often necessitate stringent production conditions and potentially harmful materials, which are not environmentally friendly, and these shortcomings have limited their widespread practical use. To overcome these challenges, we synthesized self-assembled peptide nanotubes (SPNTs) through a molecular self-assembly process. The SPNTs were then combined with SnO2 in varying proportions to construct NO2 gas sensors. The design of this sensor ensured efficient electron transfer and leverage the extensive surface area of the SPNTs for enhanced gas adsorption and the effective dispersion of SnO2 nanoparticles. Notably, the performance of the sensor, including its sensitivity, response time, and recovery rate, along with a lower detection threshold, could be finely tuned by varying the SPNTs content. This approach illustrated the potential of bioinspired methodologies, using peptide self-assemblies, to develop integrated sensors for pollutant detection, providing a significant development in environmentally conscious sensor technology. [ABSTRACT FROM AUTHOR]

In this work, a novel gas sensor based on ZnO/silk fibroin (ZnO/SF), which was synthesized by the hydrothermal method, was proposed for efficient and fast detection of NO 2 gas under the irradiation of 365 nm UV-light at room temperature. The prepared ZnO/SF sensor activated by UV showed a high sensing response of about 85 towards 20 ppm NO 2 gas at room temperature with an average response and recovery time of 26 s and 16 s, respectively. Test results of 1 ppm, 5 ppm, 10 ppm, 20 ppm NO 2 gas indicated that the ZnO/SF sensor had a very excellent response and linearity. Additionally, the sensing mechanism was analyzed as well. [ABSTRACT FROM AUTHOR]

MoS 2 , as a two-dimensional material, shows great potential for use in the gas sensor field because of its large specific surface area and remarkable electrical performance. However, previous studies have shown that gas sensors based on MoS 2 materials have the drawbacks of low response and instability, which limit their development. In this paper, a suitable amount of MoS 2 and metal oxide (SnO 2) were used to form a composite material and the SnO 2 were prepared by a hydrothermal method. Compared with that of original sensors, the response of this SnO 2 /MoS 2 sensor is 4.68 at a low concentration of 1 ppm SO 2. The crystal structures and morphologies of the composites were characterized, showing that they have high crystallinity and that SnO 2 is spherical. Further experimental data indicate that the SnO 2 /MoS 2 sensor has good selectivity, repeatability and stability. In addition, the enhanced sensing characteristics of the sensor were discussed on the basis of the depletion layer and SnO 2 /MoS 2 heterojunction. • Heterostructure SnO 2 /MoS 2 was synthesized by a hydrothermal method with trace MoS 2 participated. • High sensitive sulfur dioxide gas sensor based on SnO 2 /MoS 2 was fabricated. • The role of trace MoS 2 towards improved gas sensing performance is proposed. [ABSTRACT FROM AUTHOR]

Abstract: A new polysiloxane material, polymethyl[3-(2-hydroxy)phenyl] siloxane (PMPS), was synthesized. The PMPS is a linear polysiloxane polymer functionalized with o-allyl phenol group. The chemoselective polymer was spin-coated on a 434MHz surface acoustic wave (SAW) device for detection of dimethyl methylphosphonate (DMMP) vapor ranging from 5 to 40ppm. It was found that the frequency shifts were linear to the vapor concentrations with a high sensitivity of 3kHz/ppm. Fast response of 30s and good reproducibility were achieved as well. The influence of humidity on the sensor response was also examined. The results showed that the sensitivity decreased about 1/2 when tested in 70% RH wet air than in dry nitrogen. [Copyright &y& Elsevier]

Abstract: Quartz crystal microbalance (QCM) gas sensors based on polymeric material were fabricated and their gas response characteristics were examined for four simulant gases of chemical agents, which were dimethyl methyl phosphonate (DMMP), N,N-dimethylacetamide (DMA), 1,5-dichloropentane (DCP) and dichloroethane (DCE). For the selection of appropriate coating materials, both principal component analysis (PCA) and hierarchical cluster methods were applied to a data set collected from 15 QCM sensors for 12 analytes. Four appropriate coating materials were selected after optimizing the correlation between the 15 coating materials and the first four principal component (PC) factors. The four chosen polymers were used as sensitive component for a sensor array, and then PCA is adapted to classify four simulant gases. The results show that the QCM sensor array has high sensitivity and selectivity to four chemical agents. [Copyright &y& Elsevier]

Abstract: A quartz crystal microbalance (QCM) modified with poly(vinylidene fluoride) (PVDF) was fabricated and used for detection of dimethyl methylphosphonate (DMMP) vapor, a simulant of nerve agents using a drop-coating method. Measurements were based on the frequency shifts due to the adsorption of DMMP vapor on the surface of the modified electrodes. It was found that frequency shifts were linear to the concentrations of analyte in the range of 5–60ppm with a correlation coefficient of above 0.997. The influences of temperature and humidity on the sensors were also examined. Results showed that the sensitivity to DMMP vapor was almost identical in various humidity circumstances, and the sensitivity was higher in a lower temperature range. [Copyright &y& Elsevier]

[Display omitted] • At present, most CO sensors possess high operation temperature, high power consumption and low stability. We proposed a high-performance CO sensor at room temperature. • The SnO 2 /graphene nanocomposite exhibits unique morphology with SnO 2 nanoparticles dispersing in graphene nanosheets, which exerts a great effect on in improving sensing performance of CO. • The sensor shows improved CO gas response (R≈5.9 at 40 ppm CO) compared with pure SnO 2 (R≈3.27 at 40 ppm CO). Moreover, the sensor also exhibits fast response and recovery time (37 s/43 s). A low concentration CO gas sensor at 25 °C based on SnO 2 modified graphene nanocomposite was reported in this paper. The SnO 2 /graphene nanocomposite has higher CO gas sensing performance than pure SnO 2. The SnO 2 /graphene nanocomposite showed a high response to CO (R ≈ 5.9 at 40 ppm CO) at 25 °C and shorter response and recovery times (37 s/43 s), excellent repeatability and good stability. The excellent CO sensing performance of the composites is due to graphene's ability to provide a large surface area for adsorption sites and its capacity to prevent the disagglomeration of SnO 2 nanoparticles. [ABSTRACT FROM AUTHOR]

In consideration of the different electron structure-associated physical properties and internal sensing merits of MoS 2 and SnO 2 , this work reports a nanocomposite with unique structure of MoS 2 nanosheets dispersed SnO 2 nanoparticles. The sensing performance of MoS 2 /SnO 2 sensor toward low concentration CO was investigated at room temperature under the UV light illumination. It was found that MoS 2 /SnO 2 sensor shows improved CO gas response (R ~ 4.97 at 40 ppm CO) compared with pure SnO 2 (R ~ 3.27 at 40 ppm CO), which is due to the unique structure and the formation of heterostructure between MoS 2 and SnO 2. Moreover, the fabricated sensor also exhibits fast response and recovery time (43 s/36 s). The sensor provides a potential platform for monitoring CO gas at room temperature. [ABSTRACT FROM AUTHOR]

Dual-emitting N-CDs with multi-application of white light emission, detection of metal ions, solvatochromism, detection of the water content in organic solvents, pH detection, and temperature detection. [Display omitted] • Dual-emissive N-CDs were synthesized and applied for pH and temperature sensing. • Ratiometric fluorescence probe based on N-CDs detected Fe3+, Cu2+ and Ag+ simultaneously. • N-CDs exhibited unique solvatochromism phenomena and were used for detecting water content in organic solvents. Ratiometric fluorescence probes based on multi-emission carbon dots improve accuracy and sensitivity on detecting various environment issues. Herein, a novel dual-emitting N-doped carbon dots (N-CDs) was synthesized from citric acid and urea via a solvothermal method in N,N-dimethylformamide (DMF). The blue and orange emissions of N-CDs in water were modulated, and pure white light-emitting with Commission Internationale de L'Eclairage (CIE) coordinates of (0.33, 0.33) was achieved. The two PL centers behaved differently for Fe3+, Cu2+ and Ag+ ions, with the limit of detection (LOD) of ppm as fluorescence probes. Additionally, N-CDs displayed unique solvatochromism phenomenon. A new green emission appeared in organic solvents and gradually quenched with the increase of solvent polarity. The ratiometric PL displayed an excellent linear response for detecting water, and the LOD was between 0.003 % and 0.3 % in DMF, ethanol, isopropanol and N-methylpyrrolidone. Furthermore, N-CDs exhibited pH-sensitive response in the range of 4.0–7.0 and temperature-dependent response during heating–cooling cycles between 15 and 70 °C. A simple, efficient and reliable multi-functional ratiometric probe for detecting metal ions, water content, pH and temperature simultaneously was realized. However, there is a need for future application research to overcome the limitation imposed by the excitation wavelength of 330 nm. [ABSTRACT FROM AUTHOR]

BiFeO 3 –BaTiO 3 solid solutions with pseudo-cubic phase have received a lot of attention because of their large strain for potential piezoelectric multilayer actuator applications. However, the high sintering temperature, large dielectric loss and severe strain hysteresis hindered their real applications. In this work, Li 2 CO 3 sintering aid modified 0.64BiFeO 3 -0.36BaTiO 3 (BF-BT-L) ceramics were prepared by the high-temperature sintering method, and their phase structure, microstructure, electric properties as well as strain were investigated. With the increase of Li 2 CO 3 content, the sintering temperature decreases down to 900 °C, and the relative density increases up to 96%. Of particular importance is that the dielectric loss and strain hysteresis of BF-BT-L ceramics are reduced by 40% and 47%, respectively, while BF-BT-L ceramics shows a large strain of 0.3% (60 kV/cm). The sintering temperature, relative density, strain, large-signal d 33 * and strain hysteresis of BF-BT-L ceramics are 900 °C, 96.5%, 0.3%, 500 pm/V, and 25% respectively. The reduced dielectric loss and strain hysteresis result from the enhanced relative density, decreased concentration of defects and partial phase transition from partial pseudo-cubic to rhombohedral one by Li 2 CO 3 additions. Furthermore, BF-BT-L ceramics show positive temperature dependent strain, with large d 33 * and strain hysteresis of 675 pm/V and 15% at 200 °C respectively. The simple composition, low sintering temperature, large strain and reduced strain hysteresis of BF-BT-L ceramics indicate that they are promising candidates for high-performance and lead-free piezoelectric multilayer actuator applications. Figure (a) Comparison of sintering temperature, large signal d 33 * (60 kV/cm) and strain hysteresis (60 kV/cm) of typical BF-BT based ceramics, (b) Unipolar strain of BF-BT-L ceramics with 1.5 mol% Li 2 CO 3 under the electric field of 40 kV/cm at 200 °C. [Display omitted] [ABSTRACT FROM AUTHOR]

• The morphology of ZnO materials were regulated with polypeptides assisted. • The ZnO/polypeptides materials have good NO 2 gas-sensing performances at room temperature under UV activated. • The ZnO/polypeptides-based sensor also has short response time and good linearity towards NO 2. In this work, nanoflowers-like, nanoneedles-like ZnO and ZnO nanorods have been successfully synthesized by polypeptide-assisted hydrothermal routes. The nanostructures and morphologies of the ZnO crystals were studied through X-ray diffraction (XRD), scanning electron microscopy (SEM), and it was shown that the additive of polypeptides could control the morphologies. The gas sensing properties of NO 2 have been investigated with the three ZnO materials, which showed that the ZnO nanorods-based sensor exhibits the highest response under 365 nm UV illumination at room temperature. Gas sensing results, towards NO 2 at a range of gas concentrations (10–25 ppm), also indicated it had good linearity and repeatability. [ABSTRACT FROM AUTHOR]

Nitrogen dioxide (NO 2) has been severely polluting the atmosphere and deteriorating human beings' sustainable lives. Therefore, development of gas sensors for high-selectivity and high-sensitivity detection of NO 2 has been attracting increasing attention. The state-of-the-art inorganic NO 2 gas sensors require harsh fabrication conditions or toxic materials, making the devices intrinsically eco-unfriendly. Furthermore, in most cases the sensors work at high temperatures. These disadvantages severely impede their practical applications. Herein, we report a room-temperature and highly-integrated NO 2 sensor composed of p -type self-assembled peptide fibrillar nanoforests (SPNFs) scaffolded with n -type SnO 2 nanoparticles (NPs) heterojunctions. The p-n conformations provide efficient access to target gases and allow reliable electron transformations, while the SPNFs afford a large specific surface area and multiporous structures for gas adsorption and SnO 2 NPs dispersion, resulting in an ultrahigh selectivity for NO 2 detection. Especially, the sensing performance can be optimized by modulating the thickness and density of the SPNFs, showing a high response, short response and recovery times, along with a low detection limitation. Our strategy demonstrates the development of a bioinspired platform by utilizing peptide self-assemblies to fabricate integrated sensors for polluting gas detections. • Peptide self-assemblies for practical, portable gas sensors with high performance. • Peptide arrays improve NO 2 selectivity in room-temperature gas sensors. • Fast NO 2 gas sensor: 166 ppb detection, short response/recovery (18 s/35 s). • Wireless mini NO 2 sensor with peptide arrays for portable, real-time monitoring. [ABSTRACT FROM AUTHOR]

Highlights • Fe 2 O 3 nanomaterials with different nanostructures were chosen as active materials to detect H 2 O 2. • Relative good sensing performance of N-rGO/Fe 2 O 3 nanorods electrode to H 2 O 2 was obtained. • The sensor has the potential of detecting H 2 O 2 in real samples. Abstract In this work, iron oxide nanomaterials with different shapes and structures were used as active materials for electrode. The proposed sensitive and non-enzymatic H 2 O 2 biosensor, based on N-doped graphene/porous Fe 2 O 3 NRs (N-rGO/Fe 2 O 3 NRs), exhibits good stability and reproducibility under the optimal experimental conditions. Furthermore, this H 2 O 2 biosensor was also utilized to detect H 2 O 2 in real sample (orange juice) and high selectivity towards H 2 O 2 was found. Therefore, the porous N-rGO/Fe 2 O 3 NRs composite is thought of as a potential material in biosensing and bioanalysis. [ABSTRACT FROM AUTHOR]

The grain-size effects of the direct piezoelectric coefficient (d 33 ) and the converse piezoelectric coefficient (d 33 *) of BaTiO 3 ceramics with different Ba/Ti ratios were systematically explored. It was found that both d 33 and d 33 * exhibited strong grain size (g) dependences for BaTiO 3 ceramics with various Ba/Ti ratios. Although d 33 showed similar grain-size dependence for all the Ba/Ti ratios except a subtle shift of the critical grain size from 1 μm to 3 μm, two entirely different grain-size dependence of d 33 * were observed. By carefully examining the microstructure and ferroelectric properties of the ceramics, the variations of domain configurations and maximum polarization of BaTiO 3 ceramics with different Ba/Ti ratios were considered to be responsible for the different grain-size dependence of d 33 and d 33 *, respectively. [ABSTRACT FROM AUTHOR]

It is difficult to develop BaTiO 3 -based ceramics with enhanced electrical properties and temperature stability simultaneously. In this regard, Er-modified Ba(Zr 0.05 Ti 0.95 )O 3 (BZT-Er) ceramics were designed and synthesized to solve the above problem. The effect of Er 2 O 3 on the microstructure, phase transition, piezoelectric, electromechanical performance and thermal stability of BZT piezoceramics were systemically explored. It was shown that the addition of Er 2 O 3 hardly influences the phase structure of BZT ceramics, which was confirmed by the XRD, Raman and dielectric measurements. The optimized piezoelectric and electromechanical performance is achieved for the BZT-0.04Er ceramics with d 33 of 253pC/N and S max / E max of 368 pm/V, respectively, along with no deterioration of the thermal stability. Consequently, the improvement in piezoelectric, electromechanical and thermal stability was realized simultaneously in BZT-Er ceramics. These observations indicate that the Er-modified BZT ceramics can be deemed as one of the hopeful candidates for actual applications, showing remarkable figure of merit. [ABSTRACT FROM AUTHOR]

In this paper, oriented of micron-thick yttrium-iron-garnet ferrite films were deposited on Gd 3 Ga 5 O 12 substrate by magnetron sputtering based on layer-by-layer growth method. The effect of layer by layer growth method on films morphology, crystal structure and magnetic properties were investigated. X-ray diffraction θ-2θ reveals the maximum thickness of oriented film was increased by layer-by-layer growth method. In addition, scanning electron microscopy displays excellent morphology with uniform size of grain for the film prepared under 2.4 μm@800 nm condition. Magnetic hysteresis loops and FMR spectrum represent this layer-by-layer growth method can effective increase film saturation magnetization and decrease FMR linewidth. Specifically, oriented micron-thick (2.4 μm) YIG film with only 12 Oe of FMR linewidth has been obtained by this layer-by-layer growth method. [ABSTRACT FROM AUTHOR]

In this work, CaTiO 3 modified Mg 2 Al 4 Si 5 O 18 (MAS) of (1−x)MAS-xCaTiO 3 (0 ≤ x ≤ 0.35) cordierite ceramics were fabricated by traditional solid phase sintering method. The densification sintering temperatures of (1−x)MAS-xCaTiO 3 ceramics are effectively lowered from 1460 °C to 1250 °C with increasing addition of CaTiO 3 . X-ray diffraction spectra show that (1−x)MAS-xCaTiO 3 ceramics present cordierite phase as 0 < x ≤ 0.05, and the composite phases of cordierite, perovskite-structured CaTiO 3 and monoclinic feldspar phase of CaAl 2 Si 2 O 8 as 0.10 ≤ x ≤ 0.35. Rietveld refinement of XRD data show the six-membered rings of [(Si 4 Al 2 )O 18 ] transit from non-symmetry rings to centro-symmetry equilateral rings in (1−x)MAS-xCaTiO 3 (0 < x ≤ 0.10). The optimal dielectric properties of Q × f = 55490 GHz (at 15.3 GHz), ε r = 7.2 and τ f = −28.3 ppm/°C are obtained at x = 0.5, which are better than those of pure MAS cordierite ceramics. [ABSTRACT FROM AUTHOR]

Cordierite-type (Mg 1− x Ln x ) 2 Al 4 Si 5 O 18+ x (Ln = La, Sm, 0 ≤ x ≤0.35) ceramics with low permittivity ( ε r ) were fabricated by traditional solid state reaction method. Analysis of X-ray diffraction and Raman spectra demonstrate that the symmetry of hexagonal rings strongly affects the microwave dielectric properties of (Mg 1− x Ln x ) 2 A l4 Si 5 O 18+ x cordierite ceramics. [(Mg 1− x Ln x ) 6 O 36 ] external hexagonal rings in cordierite ceramics tend to be distorted as Ln 3+ ions substitutes Mg 2+ ions, and the shapes of [(Si 4 Al 2 )O 18 ] inner hexagonal rings are alternatively tuned from elliptical to circular. Compared with pure Mg 2 Al 4 Si 5 O 18 cordierite ceramics, the improvement of [(Si 4 Al 2 )O 18 ] ring centro-symmetry and the uniform distribution of grain sizes obviously enhance the Qf value of (Mg 1− x Ln x ) 2 Al 4 Si 5 O 18+ x cordierite type ceramics. The optimum microwave dielectric properties with ε r = 6.7, Qf = 78,500 (@14.3 GHz), τ f = −22 ppm/°C were obtained by (Mg 0.95 La 0.05 ) 2 Al 4 Si 5 O 18+0.05 ceramics. Relative thermal stability with ε r = 6.8, Qf = 24,800 GHz (@13.2 GHz), τ f = −17 ppm/°C were obtained by (Mg 0.8 Sm 0.2 ) 2 Al 4 Si 5 O 18+0.2 ceramics. [ABSTRACT FROM AUTHOR]

The effects of SrTiO 3 addition on phase composition and microwave dielectric properties of cordierite (Mg 2 Al 4 Si 5 O 18 ) ceramics had been investigated in this paper. X-ray diffraction data showed that (1 − x )Mg 2 Al 4 Si 5 O 18 – x SrTiO 3 |(1 − x )MAS − x ST (0 ⩽ x ⩽ 0.35)| ceramics presented β-cordierite solid solution within 0 < x ⩽ 0.10. In the range of 0.15 ⩽ x ⩽ 0.35, the perovskite-structured SrTiO 3 and monoclinic phase of SrAl 2 Si 2 O 8 feldspar were detected. Rietveld refinement of XRD data showed the shapes of [(Si 4 Al 2 )O 18 ] hexagonal rings in (1 − x )MAS– x ST (0 < x ⩽ 0.10) happened to adjust from non-symmetry rings to centro-symmetry equilateral rings, along with the solution of SrTiO 3 into cordierite. The densification sintering temperatures of (1 − x )MAS– x ST ceramics were effectively lowered as to the effect of SrAl 2 Si 2 O 8 feldspar acting as liquid sintering aids, accompanying the improvement of microstructure of (1 − x )MAS– x ST (0 ⩽ x ⩽ 0.35) ceramics. Finally, the (1 − x )MAS– x ST ( x = 0.10) ceramics possessed the best optimal Qf value: ε r = 6.53, Qf = 80,600 GHz ( f o = 13.6 GHz), τ f = −18 ppm/°C. The (1 − x )MAS– x ST ( x = 0.20) ceramics achieved a relative stable temperature coefficient of resonant frequency with: ε r = 6.01, Qf = 51,800 GHz ( f o = 13.1 GHz), τ f = −11 ppm/°C. [ABSTRACT FROM AUTHOR]

Abstract: Hydrogenated silicon film was fabricated by using plasma enhanced chemical vapor deposition method. The influence of crystalline volume fraction variation on the thermal conductivity was investigated. The relation between crystalline volume and film thickness was characterized by using spectroscopic ellipsometry with Bruggeman effective medium (BEMA) model. The thermal conductivity of silicon film was measured based on Fourier thermal transmitting law using sputtering platinum as electrode. The results demonstrate that the thermal conductivity of silicon film is proportional to the volume fraction of crystalline silicon, and there is crystalline and thermal conductive gradient between surface and bottom in the microcrystalline film. [Copyright &y& Elsevier]

Abstract: Polyaniline/titanium dioxide (PANI/TiO2) nanocomposite thin films were processed on a silicon substrate with gold interdigital electrodes by an in-situ self-assembly approach for NH3 gas-sensing application, and the effect of polymerization temperature on the gas response of the PANI/TiO2 thin film gas sensor was investigated. The results showed that the PANI/TiO2 thin film prepared at 10°C was superior to those prepared at other temperatures in terms of response properties, which also exhibited good reproducibility, selectivity and long-term stability. UV–vis absorption and surface morphology characterization of the nanocomposite thin films were performed to explain these different gas-sensing properties. The sensing mechanism was also discussed. [Copyright &y& Elsevier]