Metal Chelation Assisted In Situ Migration and Functionalization of Catalysts on Peapod-Like Hollow SnO₂toward a Superior Chemical Sensor

Abstract

Rational design of nanostructures and efficient catalyst functionalization methods are critical to the realization of highly sensitive gas sensors. In order to solve these issues, two types of strategies are reported, i.e., (i) synthesis of peapod-like hollow SnO nanostructures (hollow 0D-1D SnO ) by using fluid dynamics of liquid Sn metal and (ii) metal-protein chelate driven uniform catalyst functionalization. The hollow 0D-1D SnO nanostructures have advantages in enhanced gas accessibility and higher surface areas. In addition to structural benefits, protein encapsulated catalytic nanoparticles result in the uniform catalyst functionalization on both hollow SnO spheres and SnO nanotubes due to their dynamic migration properties. The migration of catalysts with liquid Sn metal is induced by selective location of catalysts around Sn. On the basis of these structural and uniform functionalization of catalyst benefits, biomarker chemical sensors are developed, which deliver highly selective detection capability toward acetone and toluene, respectively. Pt or Pd loaded multidimensional SnO nanostructures exhibit outstanding acetone (R /R = 93.55 @ 350 °C, 5 ppm) and toluene (R /R = 9.25 @ 350 °C, 5 ppm) sensing properties, respectively. These results demonstrate that unique nanostructuring and novel catalyst loading method enable sensors to selectively detect biomarkers for exhaled breath sensors.

Pt Nanoparticles Sensitized Ordered Mesoporous WO3 Semiconductor: Gas Sensing Performance and Mechanism Study

“…In Figure C, the peaks at 74.1 and 70.8 eV (gap = 3.3 eV) can be assigned to Pt 0 4f 5/2 and Pt 0 4f 7/2 ; while the peaks at 75.5 and 72.2 eV are assigned to Pt 2+ 4f 5/2 and Pt 2+ 4f 7/2 , respectively. It indicates that some of metallic Pt species in the pore of the mesoporous WO 3 were oxidized to PtO x after calcination in air . It should be noted that the commercial Pt/carbon which has Pt 4f signals at 71.3 and 74.6 eV (Figure S6, Supporting Information), slightly higher than the signals for metallic Pt, immobilized on WO 3 in this study.…”

“…The base resistance of WO 3 /Pt‐0.5 was measured to 16.0 MΩ, much higher than that (1.58 MΩ) of WO 3 /Pt‐0 (Figure C,D), further confirming that the presence of Pt/PtO x NPs can significantly increase baseline resistance. When exposed to CO during the sensing process, the oxidized Pt NPs were reduced to metallic Pt, which resulted in the disappearance of the p–n heterojunction between PtO x and WO 3 and donated electrons to the WO 3 matrix, leading to effective modulation of the surface depletion layer . In addition, as more oxygen species were adsorbed on the surface of WO 3 /Pt, more surface redox reactions could occur between CO and chemisorbed oxygen.…”

“…Precious metal loaded mesoporous WO 3 materials have been reported by using the complicated hard templating synthesis of mesoporous WO 3 followed by loading noble metal via impregnation . Precious metal ions embedded in protein nanocages or metal−organic framework were prepared for electrospinning and calcination to synthesize SMO nanofibers with immobilized metal nanoparticles (e.g., Au, Pt, and Pd), which improved the dispersity of noble metal nanoparticles in SMO . However, these methods involve a multistep synthesis with poor controllability in terms of the porosity and pore accessibility, positioning metal nanoparticles and so on.…”

Heterogeneous, Porous 2D Oxide Sheets via Rapid Galvanic Replacement: Toward Superior HCHO Sensing Application

“…The as‐prepared 2D oxide NSs (CoO x NSs, G_SnO 2 /CoO x NSs and W_SnO 2 /CoO x NSs) were drop‐coated on sensing substrates that consisted of interdigitated Au electrodes (width = 25 µm, gap size = 150 µm). All the measurements were carried out under dry conditions using a homemade measurement system . The optimized HCHO‐sensing temperature was 400 °C considering the response values (Figure S5, Supporting Information).…”

Facile synthesis of In2O3 nanoparticles with high response to formaldehyde at low temperature

“…To investigate the band gap and the electron states of In 2 O 3 nanoparticles, UV–vis diffuse reflectance spectroscopy was studied, as shown in Figure A. It can be seen that all the samples have strong absorption at the wavelength of 300 nm, which is attributed to the electronic transition from the valence band to the conduction band . The band gap energies ( E g ) are calculated using the Taucs Equation 3:…”