Ordered Large-Pore Mesoporous Cr₂O₃ with Ultrathin Framework for Formaldehyde Sensing

Abstract

A series of ordered mesoporous chromium oxides (CrO) were synthesized by first replicating bicontinuous cubic Ia3d mesoporous silica (KIT-6), then a controlled mesostructural transformation from Ia3d to I432 symmetry during the replication from KIT-6 to CrO was achieved by reducing the pore size and interconnectivities of KIT-6, accompanied with an increase in pore size from 3 to 12 nm and a decrease in framework thickness from 8.6 to 5 nm of the resultant CrO replicas. The gas-sensing behavior of the CrO replicas toward formaldehyde (HCHO) was systematically investigated. Ordered mesoporous CrO with both large accessible pores (12 nm) and an ultrathin framework (5 nm) exhibits the best sensing performance, with a response (R/R = 119) toward 9 ppm of HCHO 4.4 times higher than that (R/R = 27) of its counterpart with small pores and a thick framework. Moreover, it possesses excellent selectivity for detecting HCHO over other interference gases such as CO, benzene, toluene, p-xylene, NH, HS, and moisture. The significantly enhanced sensing performance of ordered large-pore mesoporous CrO with ultrathin framework suggests its great potential for the selective detection of HCHO.

Ordered mesoporous NiFe2O4 with ultrathin framework for low-ppb toluene sensing

“…The framework thicknesses for NiFe 2 O 4 -100 and NiFe 2 O 4 -130 are about 7.4 and 8.5 nm respectively. Such effect of KIT-6 on the resultant replicas has been also reported in our previous work on nanocasted NiO and Cr 2 O 3 replicas [31,32], which mainly derives from the influence of the pore size and interconnectivity of KIT-6 on the growth of metal oxide replica within the confined mesochannels. N 2 physisorption isotherms of all the mesoporous NiFe 2 O 4 replicas are shown in Fig.…”

“…All the NiFe 2 O 4 samples were fabricated into gas sensors and tested their gas-sensing performance similar with the procedure reported in our previous work (Fig. S1 online) [31,32]. 20 lL of NiFe 2 O 4 suspension (30 mg mL À1 ) was dropped on the gold interdigital electrode to form the sensing layer.…”

“…Recently, ordered mesoporous metal oxides such as SnO 2 [24,25], In 2 O 3 [26][27][28][29], Cr 2 O 3 [30,31], NiO [32][33][34], Co 3 O 4 [35,36], ZnO [37,38], WO 3 [39][40][41], have widely been investigated as semiconducting gas-sensing materials since their large specific surface area and ordered porous structure allows for the improved sensing performance [42]. Nickel ferrite (NiFe 2 O 4 ) is one of the well-known spinel-type semiconductors and could find application in wide fields including gas sensor [43][44][45], catalysis [46][47][48], magnetism [49][50][51], and so on.…”

Designing and Fabricating Ordered Mesoporous Metal Oxides for CO2 Catalytic Conversion: A Review and Prospect

“…Up to date, several mesoporous silica (such as SBA-15, KIT-6, FDU-12, and SBA-16) have been used as hard templates for the synthesis of mesoporous crystals [25,103]. The ordered mesoporous metal oxides have been synthesized using those silica templates including Cr 2 O 3 [104], Co 3 O 4 [35,105], In 2 O 3 [106,107], NiO [51,52,108], CeO 2 [49,109], WO 3 [74,110], Fe 2 O 3 [111], Fe 3 O 4 [112], and MnO 2 [113,114].…”

Gas sensors using ordered macroporous oxide nanostructures

“…Ordered mesoporous metal oxides are regarded as a type of promising sensing materials for gas sensors because of their high specic surface areas and excellent gas accessibility. [130][131][132] The combination of macro-mesoporous (M/M) structures can not only provide highly connected diffusion channels but also engender surface accessibility, facilitating rapid sensing kinetics and high gas response. 133,134 For instance, Liu et al successfully prepared aperture-controllable 3D interconnected M/M ZnO (3D-IMM-ZnO) nanostructures by template-based Table 1 Gas-sensing properties of representative ordered macroporous metal oxide materials.…”