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Structural Stability and Performance of Noble Metal-Free SnO2-Based Gas Sensors.

Tricoli A - Biosensors (Basel) (2012)

Bottom Line: The effect of crystal growth during operation (TO = 320 °C) on the sensor response to ethanol has been reported, revealing possible long-term destabilization mechanisms.In particular, crystal growth and sintering-neck formation were discussed with respect to their potential to change the sensor response and calibration.Furthermore, the effect of SiO2 cosynthesis on the cross-sensitivity to humidity of these noble metal-free SnO2-based gas sensors was assessed.

View Article: PubMed Central - PubMed

Affiliation: Department of Mechanical and Process Engineering, ETH Zurich, CH-8092 Zurich, Switzerland. atricoli@ethz.ch.

ABSTRACT
The structural stability of pure SnO2 nanoparticles and highly sensitive SnO2-SiO2 nanocomposites (0-15 SiO2 wt%) has been investigated for conditions relevant to their utilization as chemoresistive gas sensors. Thermal stabilization by SiO2 co-synthesis has been investigated at up to 600 °C determining regimes of crystal size stability as a function of SiO2-content. For operation up to 400 °C, thermally stable crystal sizes of ca. 24 and 11 nm were identified for SnO2 nanoparticles and 1.4 wt% SnO2-SiO2 nanocomposites, respectively. The effect of crystal growth during operation (TO = 320 °C) on the sensor response to ethanol has been reported, revealing possible long-term destabilization mechanisms. In particular, crystal growth and sintering-neck formation were discussed with respect to their potential to change the sensor response and calibration. Furthermore, the effect of SiO2 cosynthesis on the cross-sensitivity to humidity of these noble metal-free SnO2-based gas sensors was assessed.

No MeSH data available.


Average crystal size (dXRD) of large (triangles) and small (squares) SnO2 nanoparticles as a function of the sintering time at 400 °C. Cosynthesis of 1.4 wt% SiO2 (circles) drastically increased the long-term thermal-stability of SnO2 crystals.
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biosensors-02-00221-f001: Average crystal size (dXRD) of large (triangles) and small (squares) SnO2 nanoparticles as a function of the sintering time at 400 °C. Cosynthesis of 1.4 wt% SiO2 (circles) drastically increased the long-term thermal-stability of SnO2 crystals.

Mentions: Crystal growth during operation at the elevated working-temperatures (250–500 °C) of metal-oxide gas sensors is considered to contribute to the drift of their baseline (film resistance without the analyte) and poor long-term stability of their response [2,3]. The BET and XRD size were within 1 nm suggesting formation of mainly monocrystalline particles. Figure 1 shows the average crystal size of large (triangles) and small (squares) SnO2 nanoparticles as a function of the sintering time at 400 °C. The crystal size of the better performing, small SnO2 nanoparticles (Figure 1, squares) increased from 12 to 22 nm with increasing sintering time from 0 to 24 h. A crystal size of 21.6 nm was obtained already after 12 h sintering (Figure 1, squares). In contrast, the crystal size of the large SnO2 nanoparticles (Figure 1, triangles) increased only from 21.9 to 24.2 with increasing sintering time from 0 to 24 h. This indicates that, for sensor operation at 400 °C, flame-made nanoparticles constituted by pure SnO2 crystals have a thermodynamically stable size of nearly 24 nm in agreement with the poor thermal stability of small SnO2 nanoparticles and with the grain size stability conditions reported for several other synthesis methods [3]. This is in line with the rapid crystal and grain growth of flame-made SnO2 nanoparticles observed already at low sintering temperatures [7] suggesting that obtaining stable sensor responses requires testing of the sensors for several consecutive days. In particular, the asymptotic-like growth of the small SnO2 nanoparticles (Figure 1, squares) toward 22 nm suggests that small drift of sensor response and baseline may continue for a very long time span (>>24 h). In fact, the thermodynamically stable crystal size (at 400 °C) of 24 nm was still not obtained upon 24 h sintering.


Structural Stability and Performance of Noble Metal-Free SnO2-Based Gas Sensors.

Tricoli A - Biosensors (Basel) (2012)

Average crystal size (dXRD) of large (triangles) and small (squares) SnO2 nanoparticles as a function of the sintering time at 400 °C. Cosynthesis of 1.4 wt% SiO2 (circles) drastically increased the long-term thermal-stability of SnO2 crystals.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4263576&req=5

biosensors-02-00221-f001: Average crystal size (dXRD) of large (triangles) and small (squares) SnO2 nanoparticles as a function of the sintering time at 400 °C. Cosynthesis of 1.4 wt% SiO2 (circles) drastically increased the long-term thermal-stability of SnO2 crystals.
Mentions: Crystal growth during operation at the elevated working-temperatures (250–500 °C) of metal-oxide gas sensors is considered to contribute to the drift of their baseline (film resistance without the analyte) and poor long-term stability of their response [2,3]. The BET and XRD size were within 1 nm suggesting formation of mainly monocrystalline particles. Figure 1 shows the average crystal size of large (triangles) and small (squares) SnO2 nanoparticles as a function of the sintering time at 400 °C. The crystal size of the better performing, small SnO2 nanoparticles (Figure 1, squares) increased from 12 to 22 nm with increasing sintering time from 0 to 24 h. A crystal size of 21.6 nm was obtained already after 12 h sintering (Figure 1, squares). In contrast, the crystal size of the large SnO2 nanoparticles (Figure 1, triangles) increased only from 21.9 to 24.2 with increasing sintering time from 0 to 24 h. This indicates that, for sensor operation at 400 °C, flame-made nanoparticles constituted by pure SnO2 crystals have a thermodynamically stable size of nearly 24 nm in agreement with the poor thermal stability of small SnO2 nanoparticles and with the grain size stability conditions reported for several other synthesis methods [3]. This is in line with the rapid crystal and grain growth of flame-made SnO2 nanoparticles observed already at low sintering temperatures [7] suggesting that obtaining stable sensor responses requires testing of the sensors for several consecutive days. In particular, the asymptotic-like growth of the small SnO2 nanoparticles (Figure 1, squares) toward 22 nm suggests that small drift of sensor response and baseline may continue for a very long time span (>>24 h). In fact, the thermodynamically stable crystal size (at 400 °C) of 24 nm was still not obtained upon 24 h sintering.

Bottom Line: The effect of crystal growth during operation (TO = 320 °C) on the sensor response to ethanol has been reported, revealing possible long-term destabilization mechanisms.In particular, crystal growth and sintering-neck formation were discussed with respect to their potential to change the sensor response and calibration.Furthermore, the effect of SiO2 cosynthesis on the cross-sensitivity to humidity of these noble metal-free SnO2-based gas sensors was assessed.

View Article: PubMed Central - PubMed

Affiliation: Department of Mechanical and Process Engineering, ETH Zurich, CH-8092 Zurich, Switzerland. atricoli@ethz.ch.

ABSTRACT
The structural stability of pure SnO2 nanoparticles and highly sensitive SnO2-SiO2 nanocomposites (0-15 SiO2 wt%) has been investigated for conditions relevant to their utilization as chemoresistive gas sensors. Thermal stabilization by SiO2 co-synthesis has been investigated at up to 600 °C determining regimes of crystal size stability as a function of SiO2-content. For operation up to 400 °C, thermally stable crystal sizes of ca. 24 and 11 nm were identified for SnO2 nanoparticles and 1.4 wt% SnO2-SiO2 nanocomposites, respectively. The effect of crystal growth during operation (TO = 320 °C) on the sensor response to ethanol has been reported, revealing possible long-term destabilization mechanisms. In particular, crystal growth and sintering-neck formation were discussed with respect to their potential to change the sensor response and calibration. Furthermore, the effect of SiO2 cosynthesis on the cross-sensitivity to humidity of these noble metal-free SnO2-based gas sensors was assessed.

No MeSH data available.