In this work, SnO2 nanoparticles with Ni doping were synthesized via a facile one-step hydrothermal route. The addition of Ni to SnO2 lead to significant enhanced response to formaldehyde (HCHO). The Ni-doped SnO2 materials were used to fabricate HCHO gas sensors and the comprehensive HCHO-sensing properties under diverse working temperatures were tested and studied. With suitable Ni concentration, the SnO2 nanoparticles exhibited a 10 times sensing enhancement with high gas response, excellent selectivity and good stability. Furthermore, the limit of detection (LOD) was experimentally figured out to be as low as 120 ppb, which is much lower than the threshold exposure limit of HCHO proposed by American Conference of Governmental Industrial Hygienists. Importantly, the excellent performances of the as-fabricated gas-sensing devices make Ni-doped SnO2 a promising candidate for HCHO sensing applications. This synthesis strategy here can also give guidance for designing high-performance HCHO gas sensors.

Enhanced formaldehyde detection based on Ni doping of SnO2 nanoparticles by one-step synthesis

Ultra-fast and highly selective room-temperature formaldehyde gas sensing of Pt-decorated MoO3 nanobelts

Highly sensitive formaldehyde gas sensors based on Y-doped SnO2 hierarchical flower-shaped nanostructures

Despite the improvement in sensing technologies, detection of small and highly reactive molecules like formaldehyde remains a highly challenging area of research. Applications of nanomaterials/nanostructures and their composites have increased as effective sensing platforms (e.g., reaction time, sensitivity, and selectivity) for the detection of aqueous or gaseous formaldehyde based on diverse sensing principles. In this review, the basic aspects of important nanomaterial-based sensing systems (e.g., electrochemical, electrical, biological, and mass variation sensors) were evaluated in relation to performance, cost, and practicality of sensing gas phase formaldehyde. Accordingly, existing knowledge gaps in such applications were assessed in various respects along with suitable recommendations for building a new roadmap for the expansion of chemical sensing technology of gas phase formaldehyde.

Nanomaterials for sensing of formaldehyde in air: Principles, applications, and performance evaluation

Resistive-type VOCs and pollution gases sensor based on SnO2: A review

Pure and La-doped SnO2 nanoparticles were synthesized by ball-milling solid chemical reaction method. The microstructure, morphologies and gas sensing properties of as-synthesized nanoparticles were characterized by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray, transmission electron microscope and gas-sensing measurement device. Compared with pure SnO2 sensor, La-doped SnO2 sensor exhibited excellent formaldehyde sensing properties at the optimum temperature of 240 °C. Among them, 3 at% La-doped SnO2 sensor showed the highest response of 31.5–50 ppm formaldehyde vapor, the response and recovery time were 5 and 26 s, respectively. Moreover, the relationships between response value and HCHO concentration, and the selectivity of pure and 3 at% La-doped SnO2 sensor were investigated. The result indicated that the 3 at% La-doped SnO2 sensor had high response, short response-recovery time and good selectivity to formaldehyde. Finally, the gas-sensing mechanism of SnO2 sensor were discussed.

Enhanced formaldehyde gas sensing properties of La-doped SnO 2 nanoparticles prepared by ball-milling solid chemical reaction method

In this paper, Ce-doped ZnO gas sensors with different Ce/Zn ratios have been fabricated by a facile hydrothermal process, starting from zinc acetate dihydrate, cerium(III) nitrate hexahydrate and PEG. The microstructure, morphologies and components of pure ZnO and Ce-doped ZnO are characterized by X-ray diffraction, scanning electron microscope and energy dispersive spectrometer, respectively. The sensitivities to testing gases are investigated through the static testing system. Compared with pure ZnO, Ce-doped ZnO sensors showed relatively higher sensitivity and faster response/recovery time. Among them, 3 at.% Ce-doped ZnO sensor exhibited a maximum sensitivity of 560 (Ra/Rg) for 300 ppm of 1,2-propanediol at the optimum operating temperature of 260 °C and the response and recovery time is 4 s and 16 s, respectively. Finally, the gas-sensing mechanism of ZnO sensors is discussed.

Synthesis and properties of Ce-doped ZnO as a sensor for 1,2-propanediol

In this work, TiO2-based varistor ceramics doped with Nb2O5, SiO2 and Sm2O3 are prepared by using conventional solid state synthesis. X-ray diffractometry, scanning electron microscopy, energy dispersive spectrometer and direct current electrical measurement are used to study phase composition, microstructure and nonlinear properties. It is found that the second phase emerges at grain boundary, having a great influence on nonlinear electrical behaviors. Breakdown voltage E1mA initially decreases and then increases with increasing of Sm2O3 content. The minimum of breakdown voltage E1mA (9.3 V/mm) occurs at the composition of 99.0 %TiO2–0.5 %Nb2O5–0.3 %SiO2–0.2 %Sm2O3. Relative dielectric constant initially increases and then decreases. When the content of Sm2O3 increases to 0.3 %, the varistor has ultrahigh dielectric constant, which is consistent with its narrowest grain-boundary barriers. The nonlinear coefficient increases from 2.51 to 4.13 with increase of Sm2O3 from 0.0 to 0.4 %, and varistor of 98.8 %TiO2–0.5 %Nb2O5–0.3 %SiO2–0.4 %Sm2O3 owns the highest grain-boundary barriers.

Xu xiang

Papers

Enhanced formaldehyde gas sensing properties of La-doped SnO 2 nanoparticles prepared by ball-milling solid chemical reaction method

Synthesis and properties of Ce-doped ZnO as a sensor for 1,2-propanediol

Influence of Sm 2 O 3 on electrical performance of (Nb, Si)-doped TiO 2 -based varistor