Lately novel strategies to enhance the sensing properties on iron oxide have been proposed to achieve high performance gas sensors for acetone detection. In this working report, the synthesis of iron-glycerate (Fe-Gly) using glycerol to combine with Fe 3+ is first presented. Depending on the thermal treatment, this compound can evolve into γ-Fe 2 O 3 , α/γ-Fe 2 O 3 and α-Fe 2 O 3 . α/γ-Fe 2 O 3 shows better sensing performance as far as acetone detection is concerned. Using the dual phases of α/γ-Fe 2 O 3 as a fundamental building block, their sensing properties were further improved using Ni doping and Ru nanoparticles functionalization. The high response and selectivity to acetone detection was ascribed to the synergistic effects of unique nanosheets, mixed phases, rich oxygen vacancies and excellent catalytic activity of Ru nanoparticles. Graphical abstract
Although individual γ-Fe2O3and α-Fe2O3have been widely fabricated for gas sensors, their mixed phase of α/γ-Fe2O3might deliver excellent sensing properties. In this study, a facile solvothermal method was used to fabricate Fe-alkoxide. After thermal treatment, it was converted into γ-Fe2O3, α-Fe2O3and their mixed-phase α/γ-Fe2O3with a nanosheets-assembled flower-like structure. We studied the influence of calcination temperature on the phase and sensing properties on acetone detection. The α/γ-Fe2O3which annealed at 400 °C included 18% α-Fe2O3and it exhibited excellent sensing performance towards acetone compared to that of γ-Fe2O3and α-Fe2O3. It showed a response of 353 to acetone with a concentration of 200 ppm, and a low limit of detection of 0.5 ppm at 160 °C. In addition, the change in responses with acetone concentration from 50 to 200 ppm shows a good linear relationship. Moreover, this material has good reproducibility and selectivity as well as a fast response time of 22 s and recovery time of 14 s to 200 ppm. Therefore, our mixed phase of α/γ-Fe2O3possesses great prospects for acetone detection.Keywords:Fe2O3;phase;gas sensor;acetone;sensing performance
Heterojunction with same elements but different types of semiconductors is a special material which is convenient for fabrication and industrialization. In this work, a series of α/γ-Fe 2 O 3 isoelement heterostructures with different crystal contents (γ-Fe 2 O 3 , 10 % α-Fe 2 O 3 /90 % γ-Fe 2 O 3 , 33 % α-Fe 2 O 3 /67 % γ-Fe 2 O 3 , 55 % α-Fe 2 O 3 /45 % γ-Fe 2 O 3 , 78 % α-Fe 2 O 3 /22 % γ-Fe 2 O 3 and α-Fe 2 O 3 ) were constructed by hydrothermal method combined with controlled partial annealing process. Physicochemical analyses including XRD, TEM , XPS , BET, UV-Vis, PL spectra and ESR analyses were applied to investigate the advantages of isoelement α/γ-Fe 2 O 3 compared with the pure single-crystalline Fe 2 O 3 . Benefiting from the enlarged specific surface area and staggered band structure, the fabricated heterostructure with 78 wt% α-Fe 2 O 3 content exhibited more efficient separation of charge carriers and thus superior photodegradation efficiency than pure Fe 2 O 3 under visible-light irradiation. Different from TiO 2 -based P25 heterostructures, Fe 2 O 3 system possesses narrower bandgap and cannot efficiently consumed the excited holes. As a result, the accumulated h + would inhibit the further separation of excitons with photocatalysis proceeding and thus induce insufficient driving force for the increment of photocatalytic ability like P25. The results presented in this work would be conducive to the rational design of staggered heterostructures.
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