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As a typical perovskite oxide, BaTiO 3 has been fully proved to be an excellent impedance humidity sensing material, meanwhile its application in human respiratory monitoring needs to be further researched. In this contribution, BaTiO 3 nanorods (BT-NR), nanowires (BT-NW) and micron particle (BT-MP) were successfully synthesized by the molten salt synthesis (MSS) method. Various characterization techniques were used to analyze the structure, morphology and composition of these materials. As-synthesized BaTiO 3 samples had been assembled as impedimetric humidity sensors and then tested systematically under relatively humidity (RH) range of 11%–97%. All the three sensors exhibited high response values greater than three orders of magnitude, which are much higher than the commercial BaTiO 3 (BT-C) sensor (S 97% = 4.90 × 102). Thereinto, the BT-NR humidity sensor holds the fastest response-recovery times (1 s and 22 s) and the smallest hysteresis (ΔH = 0.67%). Excellent sensing performance of BT-NR can be attributed to synergistic effects of larger specific surface area and smaller pore size. In addition, the BT-NR humidity sensor shows considerable potential in the field of human respiratory monitoring. This work provides a new perspective to high-performance humidity sensors for human body-related detection through morphology-controlled perovskite nanostructures. [ABSTRACT FROM AUTHOR]

ACu 3 Ti 4 O 12 (A = Sr, Ba) double perovskites are attractive dielectric materials, yet they have not been reported in the field of gas and humidity sensors. In this work, SrCu 3 Ti 4 O 12 (SCTO) and BaCu 3 Ti 4 O 12 (BCTO) powders were synthesized by a facile modified solid-phase sintering method with characteristic of abundant cation-oxygen dual-defects (oxygen vacancy, metal deficiencies of Cu+ and Ti3+). For the first time, SCTO and BCTO are explored as humidity sensing materials, while the SCTO sensor holds a response value of four orders of magnitude (S r = 2.8× 104), which is over a thousand times higher than that of BCTO (S r = 25). In addition, the SCTO sensor is featured in fast response (7 s), reliable linearity (R2 = 0.97), small hysteresis (ΔH max = 0.8%) and good repeatability in a wide relative humidity (RH) range (11%–97%). The boosted humidity sensing performance enables the SCTO sensor to possess great potential in human-body related moisture monitoring of breath and finger detection. Finally, the complex impedance analysis reveals different majority carriers of SCTO (H+) and BCTO (H 3 O+) under high RH range. The enhanced humidity sensing performance of SCTO can be attributed to the synergistic effects of richer dual-defects and larger ion potential. This work provides an excellent humidity sensing material of SCTO, and furthermore, gives new insights on defect sensitization strategy of perovskites for high-performance electronic sensory devices. [ABSTRACT FROM AUTHOR]

Layered perovskite-type niobates A 5 Nb 4 O 15 (A = Ba, Sr) are thought to be good candidates for microwave dielectric and water-splitting applications, but traditional solid-state syntheses of these compounds usually require high temperatures and complicated procedures. In this work, Ba 5−x Sr x Nb 4 O 15 (x = 0 − 5) perovskite solid solutions were obtained using a facile molten salt synthetic method. The crystal structure of Ba 5−x Sr x Nb 4 O 15 solid solutions were characterized by X-ray diffraction (XRD). Crystal structure parameters with different Sr 2+ concentrations show that the lattice parameters and unit cell volumes of Ba 5−x Sr x Nb 4 O 15 decrease with increasing [Sr 2+ ]. The humidity sensing behavior of Ba 5−x Sr x Nb 4 O 15 solid solutions was investigated over a wide relative humidity (RH) range, from 11% to 95%. Ba 2 Sr 3 Nb 4 O 15 shows the highest sensitivity among the obtained samples with a humidity hysteresis of ca. 4% RH. The response-recovery times of the Ba 2 Sr 3 Nb 4 O 15 sensor are only 2 s and 17 s as the humidity alternates between 11% and 95% RH, respectively, showing excellent potential as a humidity sensing material for practical applications. [ABSTRACT FROM AUTHOR]

In this contribution, all-inorganic lead-free halide perovskites Cs 2 SnX 6 (X = Cl, Br, I) were synthesized by simple room-temperature precipitation. Material characterization demonstrated their feature in rich defects of halogen vacancies. As room-temperature formaldehyde (HCHO) sensing materials, Cs 2 SnX 6 exhibited reliable sensitivity order of Cs 2 SnCl 6 < Cs 2 SnBr 6 < Cs 2 SnI 6. Notably, the Cs 2 SnI 6 sensor showed excellent selectivity for HCHO at room temperature with high response (S r = 78, 100 ppm), short response/recovery time (3.6 s/7.2 s), good repeatability and long-term stability. Finally, the HCHO sensing mechanism was investigated via in-situ infrared analysis, conforming abundant intermediates of dioxymethylene, formate, and carbonate. The excellent sensing performance is attributed to rich iodine vacancies (V I) as active sites induced boosted stepwise oxidation of HCHO molecules on Cs 2 SnI 6 surface. This work provides a fine candidate for practical HCHO detection at room temperature, and furthermore, gives new insights in designing halide perovskites for next-generation sensory devices. An all-inorganic lead-free halide perovskite Cs 2 SnI 6 with rich iodine vacancies (V I) was applied to room-temperature formaldehyde detection for the first time with boosted performance, especially high sensitivity and rapid response-recovery. [Display omitted] [ABSTRACT FROM AUTHOR]

Dion–Jacobson structure layered perovskite K(K 1.5 Eu 0.5 )Ta 3 O 10 was synthesized using a traditional solid-state reaction. A humidity sensor made from the obtained K(K 1.5 Eu 0.5 )Ta 3 O 10 reveals that the sensitivity exhibits good linear response, and the response and recovery time is only about 6 s and 2 s at 85% RH respectively, showing fast response and recovery characteristics. Furthermore, the humidity hysteresis is only 7% RH. All these results indicate that K(K 1.5 Eu 0.5 )Ta 3 O 10 can be utilized in high-performance humidity sensors. [ABSTRACT FROM AUTHOR]

Pure ZnO and carbon-doped ZnO hollow spheres were successfully synthesized by a hydrothermal-calcination process. The doping content of carbon in ZnO was controlled by different calcination temperatures at 500 ℃ and 600 ℃ (named as ZnO-500 and ZnO-600). Systematic material characterization indicates that mesoporous ZnO hollow spheres are featured in abundant defects induced by in-situ carbon doping. Used as gas sensing materials, the response of ZnO-600 towards 200 ppm dimethylamine (83.6) is 28.6 times and 2.5 times higher than that of Pure ZnO (2.9) and ZnO-500 (32.8) at the optimum operating temperature of 240 ℃. Remarkably, the response of ZnO-600 toward 1 ppm dimethylamine is as high as 7.2, and simultaneously the limit of detection is as low as 108 ppb. In addition, ZnO-600 hollow spheres hold excellent gas-sensing performance in response-recovery speed, selectivity, repeatability, long-term stability, and water resistance towards dimethylamine. The boosted dimethylamine sensing performance of ZnO-600 is mainly attributed to synergistic effects of the unique mesoporous microstructure and rich defects induced by in-situ carbon doping. This work provides a promising material for dimethylamine detection, the properties of which can be improved for practical applications in the future. Furthermore, this contribution gives new insights into nonmetal-doped metal oxide nanostructures for high-performance gas sensors via surface defect control. [Display omitted] • In-situ carbon-doped ZnO hollow spheres were successfully synthesized by a hydrothermal-calcination process. • ZnO hollow spheres doped with different carbon amounts were obtained by controlling the calcination temperature. • Carbon-doped ZnO hollow spheres exhibited excellent gas sensing properties to dimethylamine. • The enhanced response is attributed to the unique microstructure and abundant defects induced by in-situ carbon doping. [ABSTRACT FROM AUTHOR]

In this study, an all-inorganic lead-free halide perovskite Cs 2 InCl 5 (H 2 O) was synthesized using a hydrothermal method. Considering the structural characteristics of Cs 2 InCl 5 (H 2 O), this material is explored for room-temperature humidity-sensing application. We demonstrated that the Cs 2 InCl 5 (H 2 O) sensor has excellent performance in the 11% to 97% relative humidity (RH) range, including high sensitivity (1.04 × 103), fast response (30 s), small hysteresis (0.38%), and good long-term stability (30 days). Consequently, this high performance enables the Cs 2 InCl 5 (H 2 O) sensor to demonstrate great latent capacity in noncontact finger moisture detection. Finally, the humidity sensing mechanism was determined by using complex impedance spectra and corresponding equivalent circuits, demonstrating the role of charge carriers at different RH levels. This work provides a highly efficient sensing candidate for moisture detection, and more importantly offers a new strategy for the utilization of halide perovskites in high-performance sensory devices. An all-inorganic lead-free perovskite Cs 2 InCl 5 (H 2 O) with heterogeneous oxygen was applied to humidity test for the first time with high performance, enabling great latent capacity in noncontact finger moisture detection. [Display omitted] [ABSTRACT FROM AUTHOR]

Highlights: [•] Red-light-emitting La4Ti9O24:Eu3+ phosphor was obtained from sol–gel precursors. [•] Under 465nm excitation, the phosphor exhibits strong red emission at 613nm. [•] Doping with either Si4+ or Bi3+ enhances emission intensity of the phosphor. [•] The phosphor could be candidate for color mixing in white light-emitting diode. [ABSTRACT FROM AUTHOR]

Abstract: Flowerlike ZnO nanostructures composed of nanorods were synthesized by co-precipitation method using Zn(NO3)2·6H2O and (CH2)6N4 as reactants, polyethylene glycol 400 as surfactant. La2O3 was dispersed onto the obtained ZnO with a content of 0.5–2.0wt% to enhance the gas-sensing property. Gas-sensing results of the La2O3-doped ZnO to ethanol, acetone, ammonia and formaldehyde, respectively, reveal that response of La2O3-doped ZnO to a specified test gas is higher than that of no La2O3-doped. Response of 1.0wt% La2O3-doped ZnO to 200ppm acetone reaches 54.1 at the working temperature of 350°C, and the response time is only 8s, implying the potential for detection of low gas concentration. [Copyright &y& Elsevier]