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Sol-Gel Thin Films for Plasmonic Gas Sensors.

Della Gaspera E, Martucci A - Sensors (Basel) (2015)

Bottom Line: Plasmonic gas sensors are optical sensors that use localized surface plasmons or extended surface plasmons as transducing platform.Surface plasmons are very sensitive to dielectric variations of the environment or to electron exchange, and these effects have been exploited for the realization of sensitive gas sensors.In this paper, we review our research work of the last few years on the synthesis and the gas sensing properties of sol-gel based nanomaterials for plasmonic sensors.

View Article: PubMed Central - PubMed

Affiliation: CSIRO Manufacturing Flagship, Bayview Ave, Clayton, Victoria 3168, Australia. enrico.dellagaspera@csiro.au.

ABSTRACT
Plasmonic gas sensors are optical sensors that use localized surface plasmons or extended surface plasmons as transducing platform. Surface plasmons are very sensitive to dielectric variations of the environment or to electron exchange, and these effects have been exploited for the realization of sensitive gas sensors. In this paper, we review our research work of the last few years on the synthesis and the gas sensing properties of sol-gel based nanomaterials for plasmonic sensors.

No MeSH data available.


(a) SEM image of a TiO2-Au film annealed at 100 °C; (b) SEM image of a TiO2-Au film annealed at 500 °C; (c) Time resolved tests for a TiO2-Au film exposed to different concentrations of H2 (in volume %) at 300 °C (λ = 595 nm); (d) Optical absorption spectra of TiO2-Au NRs films synthesized from layered titanates showing the effect of UV treatment in avoiding the spheroidization of Au NRs; (e) Optical absorption spectra of TiO2 films containing Au-Pt core-shell NPs exposed to 1% hydrogen at room temperature. The inset shows Au-Pt colloidal solutions; (f) Time resolved tests for a TiO2-Au-Pt film exposed to 1% hydrogen at room temperature (λ = 500 nm).
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sensors-15-16910-f003: (a) SEM image of a TiO2-Au film annealed at 100 °C; (b) SEM image of a TiO2-Au film annealed at 500 °C; (c) Time resolved tests for a TiO2-Au film exposed to different concentrations of H2 (in volume %) at 300 °C (λ = 595 nm); (d) Optical absorption spectra of TiO2-Au NRs films synthesized from layered titanates showing the effect of UV treatment in avoiding the spheroidization of Au NRs; (e) Optical absorption spectra of TiO2 films containing Au-Pt core-shell NPs exposed to 1% hydrogen at room temperature. The inset shows Au-Pt colloidal solutions; (f) Time resolved tests for a TiO2-Au-Pt film exposed to 1% hydrogen at room temperature (λ = 500 nm).

Mentions: An even greater degree of control in the microstructure and on the properties of the metal/metal oxide nanocomposites is achieved when also the TiO2 matrix is synthesized starting from colloidal NPs. Following this idea, we have developed an acid-catalyzed sol-gel protocol to synthesize small (~4 nm) anatase NPs that can be directly mixed with PVP-stabilized Au colloids and used to prepare TiO2-Au composite films [55]. Briefly, titanium isopropoxide is slowly added to a mixture of water, methanol and hydrochloric acid under vigorous stirring and mildly heated to nucleate small anatase crystals. The electrostatically stabilized colloids can be purified and redispersed in methanol at a high concentration suitable for thin film deposition via spin coating. Such suspensions are mixed with Au colloids in ethanol obtaining stable mixed colloidal solutions, thanks to the Au surface ligands which guarantee colloidal stability in solution and homogeneous dispersion of the metal NPs within the nanocrystalline TiO2 matrix (Figure 3a,b). This approach enables to prepare highly crystalline thin films at low temperatures, because there is no need to anneal at high temperature to trigger the crystallization of the titania sol-gel matrix, which has been found to occur above 400 °C. The very small TiO2 NPs also provide a larger surface area and an increased number of active sites with respect to traditional sol-gel films. Moreover, excellent surface contact between Au and TiO2 NPs has been demonstrated, and exploited to improve the gas sensing performances of these nanocomposites. In fact, reversible CO and hydrogen detection, with enhanced sensitivity compared to the state of the art TiO2-Au optical sensors has been achieved with our colloidal approach (Figure 3c). Detection limits below 10 ppm and response times as low as 10–20 s are demonstrated with nanocomposite films which are only 40–50 nm thick.


Sol-Gel Thin Films for Plasmonic Gas Sensors.

Della Gaspera E, Martucci A - Sensors (Basel) (2015)

(a) SEM image of a TiO2-Au film annealed at 100 °C; (b) SEM image of a TiO2-Au film annealed at 500 °C; (c) Time resolved tests for a TiO2-Au film exposed to different concentrations of H2 (in volume %) at 300 °C (λ = 595 nm); (d) Optical absorption spectra of TiO2-Au NRs films synthesized from layered titanates showing the effect of UV treatment in avoiding the spheroidization of Au NRs; (e) Optical absorption spectra of TiO2 films containing Au-Pt core-shell NPs exposed to 1% hydrogen at room temperature. The inset shows Au-Pt colloidal solutions; (f) Time resolved tests for a TiO2-Au-Pt film exposed to 1% hydrogen at room temperature (λ = 500 nm).
© Copyright Policy
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4541914&req=5

sensors-15-16910-f003: (a) SEM image of a TiO2-Au film annealed at 100 °C; (b) SEM image of a TiO2-Au film annealed at 500 °C; (c) Time resolved tests for a TiO2-Au film exposed to different concentrations of H2 (in volume %) at 300 °C (λ = 595 nm); (d) Optical absorption spectra of TiO2-Au NRs films synthesized from layered titanates showing the effect of UV treatment in avoiding the spheroidization of Au NRs; (e) Optical absorption spectra of TiO2 films containing Au-Pt core-shell NPs exposed to 1% hydrogen at room temperature. The inset shows Au-Pt colloidal solutions; (f) Time resolved tests for a TiO2-Au-Pt film exposed to 1% hydrogen at room temperature (λ = 500 nm).
Mentions: An even greater degree of control in the microstructure and on the properties of the metal/metal oxide nanocomposites is achieved when also the TiO2 matrix is synthesized starting from colloidal NPs. Following this idea, we have developed an acid-catalyzed sol-gel protocol to synthesize small (~4 nm) anatase NPs that can be directly mixed with PVP-stabilized Au colloids and used to prepare TiO2-Au composite films [55]. Briefly, titanium isopropoxide is slowly added to a mixture of water, methanol and hydrochloric acid under vigorous stirring and mildly heated to nucleate small anatase crystals. The electrostatically stabilized colloids can be purified and redispersed in methanol at a high concentration suitable for thin film deposition via spin coating. Such suspensions are mixed with Au colloids in ethanol obtaining stable mixed colloidal solutions, thanks to the Au surface ligands which guarantee colloidal stability in solution and homogeneous dispersion of the metal NPs within the nanocrystalline TiO2 matrix (Figure 3a,b). This approach enables to prepare highly crystalline thin films at low temperatures, because there is no need to anneal at high temperature to trigger the crystallization of the titania sol-gel matrix, which has been found to occur above 400 °C. The very small TiO2 NPs also provide a larger surface area and an increased number of active sites with respect to traditional sol-gel films. Moreover, excellent surface contact between Au and TiO2 NPs has been demonstrated, and exploited to improve the gas sensing performances of these nanocomposites. In fact, reversible CO and hydrogen detection, with enhanced sensitivity compared to the state of the art TiO2-Au optical sensors has been achieved with our colloidal approach (Figure 3c). Detection limits below 10 ppm and response times as low as 10–20 s are demonstrated with nanocomposite films which are only 40–50 nm thick.

Bottom Line: Plasmonic gas sensors are optical sensors that use localized surface plasmons or extended surface plasmons as transducing platform.Surface plasmons are very sensitive to dielectric variations of the environment or to electron exchange, and these effects have been exploited for the realization of sensitive gas sensors.In this paper, we review our research work of the last few years on the synthesis and the gas sensing properties of sol-gel based nanomaterials for plasmonic sensors.

View Article: PubMed Central - PubMed

Affiliation: CSIRO Manufacturing Flagship, Bayview Ave, Clayton, Victoria 3168, Australia. enrico.dellagaspera@csiro.au.

ABSTRACT
Plasmonic gas sensors are optical sensors that use localized surface plasmons or extended surface plasmons as transducing platform. Surface plasmons are very sensitive to dielectric variations of the environment or to electron exchange, and these effects have been exploited for the realization of sensitive gas sensors. In this paper, we review our research work of the last few years on the synthesis and the gas sensing properties of sol-gel based nanomaterials for plasmonic sensors.

No MeSH data available.