- Email: [email protected]
Photocatalytically Decorated Au-nanoclusters TiO2 Nanofibres for Elemental Mercury Vapor Detection
Available online at www.sciencedirect.com
ScienceDirect Procedia Engineering 120 (2015) 422 – 426
EUROSENSORS 2015
Photocatalytically decorated Au-nanoclusters TiO2 nanofibres for elemental mercury vapor detection A. Macagnano1*, E. Zampetti , V. Perri , A. Bearzotti1, F. Sprovieri2, N. Pirrone1, G. Esposito1, F. De Cesare1,3 1
4
1
IIA-CNR, Via Salaria km 29,300, 00015 Monterotondo (Rome) ITALY; 2IIA-CNR, 87036, Arcavacata Rende (CS), ITALY 3 DIBAF-University of Tuscia, Via S. Camillo de Lellis 01100, Viterbo, ITALY 4 Physics Dep.-University of Calabria, Via Pietro Bucci, 87036, Arcavacata Rende (CS), ITALY
Abstract Electrospun nanofibrous nets of titania (anatase) were deposited on interdigitated microelectrodes and photocatalytically decorated with gold nanoclusters (AuNCs) upon UV irradiation. The resulting devices appeared to be conductive even at room temperature (Ohmic behavior), and were investigated as potential chemosensors capable of entrapping and detecting elemental mercury vapors in the atmosphere. The strong affinity and specificity of Au for Hg0 conferred to AuNCs a key role in mercury sensing, by inducing a decrease in current upon mercury adsorption. Sensors conductivity appeared not to be dependent on humidity. The resulting chemosensors are expected to be inexpensive, very stable (due to the peculiar structure), and requiring low power, low maintenance and simple equipment to work. © Published by Elsevier Ltd. This © 2015 2015The TheAuthors. Authors. Published by Elsevier Ltd.is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the organizing committee of EUROSENSORS 2015. Peer-review under responsibility of the organizing committee of EUROSENSORS 2015
Keywords: TiO2 nanofibres, electrospinning, Au nanoclusters, conductive sensors, elemental mercury, atmosphere
1. Introduction Mercury is a well-known neurotoxic (even at very low levels) and persistent worldwide pollutant1. It is emitted to the air by human activities, such as manufacturing facilities, coal power plants and artisanal small scale goal mining and from natural biogeochemical processes including those related to emissions from oceans, soil and volcanoes2,3. In the atmosphere, mercury exists in three different species: i) gaseous elemental mercury; ii) particle-bound
* Corresponding author. Tel.: +39 06 90672395; fax: +39 06 90672660. E-mail address: [email protected]
1877-7058 © 2015 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license
(http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the organizing committee of EUROSENSORS 2015
doi:10.1016/j.proeng.2015.08.657
E. Zampetti et al. / Procedia Engineering 120 (2015) 422 – 426
mercury; iii) oxidized gaseous mercury (i.e. RGM, reactive gaseous mercury), this last predominantly in watersoluble forms. The factors that determine how severe the health effects are from mercury exposure include the chemical form of Hg, the duration and the route of exposure (i.e. inhalation, ingestion, dermal contact, etc.) as well as the age of the person exposed (e.g. unborn children and infants are the most susceptible). The World Health Organization has set the current Personal Exposure Limit for Hg at 0.05 mg/cm3 or 5.6 ppbv in air. Since 2010 a European project called Global Mercury Observation System (GMOS - www.gmos.eu)3,4, expected to directly support the implementation of the Minamata Convention, has been involved in creating an international network capable of providing accurate measurements of Hg on a global scale. Up to now, air monitors are highly sensitive and capable of detecting the global mercury background, but are complex, costly and high-maintenance (requiring more than 40 monitoring sites and skilled operators). The detection and measurement of mercury is usually performed by spectroscopic methods, i.e. atomic absorption spectroscopy (AAS), atomic fluorescence spectroscopy (AFS), atomic emission spectroscopy (AES), or mass spectrometry (MS) 5. The need for fast detection systems, at low cost and low maintenance, as well as ease of use are becoming ever more urgent. Accordingly, recently there has been a significant amount of works6 which has focused on developing microsensors based nanomaterials to monitor Hg0 vapor in air. Gold nanostructures (nanoparticles, nanowires, nanorods) due to the combination of both the affinity of Au with Hg0 and the size of the structures (a few nanometers), resulted the most investigated nanomaterials for mercury detection among the several sensing strategies based on optical, gravimetric, electrochemical and conductive sensors7-9. In the present study, hybrid nanofibrous electrospun layers of TiO2 coating Pt microelectrodes were suitably designed in order to create nanostructured 3D-frameworks, potentially capable of adsorbing and revealing elemental mercury vapors in the atmosphere. Indeed, exploiting the outstanding photocatalytic properties of the nanofibres of titania, gold nanoclusters were selectively grown, under UV-light irradiation, on the electrospun titania nanofibres through the photocatalytic reduction of HAuCl4 (tetrachloroauric acid ) in the presence of an organic capping reagent. Due to the uniqueness of the resulting nanostructures (high surface to volume ratio, high fibres interconnectivity and nano-scale interstitial spaces)10 and for production rate and cost, the planned sensors were expected to be promising candidates for elemental mercury detection in traces. 2. Experimental Electrospinning solution (7.877 × 10−5 M), was prepared according to literature11. The substrates were fixed, through a suitable holder, to the collector surface (600 rpm, 21 ◦C and 35% RH) and the deposition time was set to 20 min. Fibres were annealed under oxygen atmosphere using a thermal ramp from room temperature up to 550 ◦C (1 ◦C min−1, 4h dwell time) in order to remove PVP and proceed to crystallize the metal oxide (anatase). The resulting fibrous layers were immersed into an aqueous solution containing 1.5•10-3M tetrachloroauric acid (HAuCl4) and 0.1M PVP (as capping agent). The substrate was then irradiated with UV light for specified intervals (UV lamp (365 nm) (Helios Italquartz). The samples on silicon wafers were directly employed for scanning electron microscopy (SEM, Jeol, JSM 5200, 20keV) and atomic force microscopy (AFM, Nanosurf FlexAFM, tapping mode 190Al-G, 190 kHz, 48N/m). The transducers, interdigitated electrodes (IDEs), had 40 pairs of Ti/Pt electrodes, 150 nm thick, 20 Pm width electrode, 20 Pm gap). Each chemoresistor was placed in a suitable case made of PTFE and connected to an electrometer (Keithley 6517 Electrometer). In order to test the responsiveness of the device to lower Hg concentration (measured by Tekran®2537A), a dynamic permeation tube was set up to dilute the mercurysaturated gas to the concentration range of interest, by using a mass flow controller system (4-Channel-MKS 247). 3. Results and Discussion Specifically, titania fibers (100 nm mean diameter) were decorated with gold nanoclusters (AuNCs) induced to grow selectively upon photocatalytic reduction of HAuCl4 caused by UV light irradiation (Fig. 1,a). Similar structures are reported in literature12 to be used to create electrospun nanofibrous filters and catalytic systems as novel abatement systems for Hg0. They reported an efficiency of about 100%. The morphology and size of gold nanoclusters and the coverage of fibres depended on UV irradiation exposure (Fig.1,b-c). When the samples were UV irradiated for 1 hour, fibres were completely covered with Au particles (confirmed by SEM microanalysis, data not shown) with globular shape merged together, and numerous protruding buds, densely clustered and overlapping (SEM and AFM
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micrographs in Fig.1). On the contrary, when fibres were exposed to UV irradiation for a shorter time (30 min), they appeared more homogeneously coated with round-shaped nanoparticles.
Figure 1. (a)Optical micrographs of the electrodes before(top) and after electrospun deposition (in the middle) and a picture of the samples (down) in solution and under UV irradiation; SEM (b) and AFM (c) micrographs of titania nanofibres after 60 min and 30 min of UV exposure, respectively. The chemical reaction can be monitored by the color change of the solution (colorless>orange>red>purple).
The sensors coated with both structures showed Ohmic behavior in air and at room temperature (Figure 2), but with different resistance values depending on the quality of the coverage, as expected. In the present study we reported the preliminary results related to sensors coated with 1h UV-irradiated fibres (the most conductive sensors, R=580650 Ohm). Oxygen and relative humidity did not affect the electrical parameters of the sensors, thus comparable electrical features were reported when measurements were carried out under nitrogen or air (Figure 2, left) and increasing percentages of relative humidity (Figure 2,right). The strong affinity and specificity of Au for Hg0 explain the sensitive responsiveness of Au nanoclusters (AuNCs) on the nanofibrous scaffolds to mercury3, highlighted by the current changes of the sensors upon Hg adsorption.
Figure 2 (Left): Current-Voltage curve of 1h-UV-exposed sensor under air (black line) and nitrogen (red one) flow; (right) sensor transient response (current) to increasing percentage of relative humidity (10%-70% %RH) (0.5V).
E. Zampetti et al. / Procedia Engineering 120 (2015) 422 – 426
425
In detail, sensors exposed to mercury vapours, pointed out a decrease in current, and the slope of the electrical signals seemed to be dependent on analyte concentration. When a sensor was exposed overnight to high concentration of Hg (PV=1.6•10-3 mbar), its resistance changed by 30% (Fig. 3, a). In order to test the responsiveness of the device to low Hg concentration, mercury vapours were flushed, from a dynamic permeation tube, throughout the measuring chamber. The final Hg0 concentration was obtained by tuning the oven temperature and the dilution flow. Preliminary results showed that the exposure of a sensor to 7.5ng/l of Hg resulted in decreasing current, with a rate of ~109 nA/min (+2V) and a limit of detection about 0.18 ng/l (LOD: three times the standard deviation of the blank) (Figure 3, b).Quick thermal shots restored sensors, due to the high porosity of the layer and the extremely reduced size of the gold nanoclusters.
Figure 3. a) Diagram of the change of resistance values of the sensor after 1 and 12 hour of exposure to mercury vapour (1.6 •10 -3 mbar); b) Sensor responses (current values) to 10 sccm-flow of mercury-saturated air (~7.5 ng/l) over time (30-90 min)
4. Conclusions Electrospinning was confirmed to be a very promising nanotechnology for developing smart and ultra-sensitive sensing systems. Exploiting the excellent photocatalytic properties of the nanofibrous titania, the sensing layer was decorated with gold nanoparticles (AuNPs) by immersing the electrospun material, into a solution containing HAuCl4 under UV irradiation. AuNCs played an active role in mercury sensing, increasing the active surface area, improving both diffusion inside the layer and the sensor conductivity. The resulting sensors, functioning in air and at room temperature, showed constant and low level of resistance, thus providing the potential to work at very low voltage values (low power, slow sensor degradation). The response curve of the tested sensors to increasing concentrations of mercury vapor reported a general decrease in current. These attracting sensing features sound as encouraging premises to develop sensors for elemental mercury based on electrospun fibres of gold nanofunctionalised titania. References [1] J. Qui, Tough talk over mercury treaty, Nature 493(2013) 144–145. [2] N. Pirrone, W. Aas., S. Cinnirella, R. Ebinghaus, I. M. Hedgecock, J. M. Pacyna, F. Sprovieri, E. M. Sunderland (2013) Toward the next generation of air quality monitoring: Mercury. Atmospheric Environment, doi:10.1016/j. atmosenv.2013.06.053. [3] Lubick, N., Fundign Struggle for Mercury monitoring (2013) Nature, 459, 620-621 (2009) | doi:10.1038/459620b [4] S. Cinnirella, F. D’Amore, M. Bencardino, F. Sprovieri, N. Pirrone, The GMOS cyber(e)-infrastructure: advanced services for supporting science and policy, Environmental Science and Pollution Research 21 (2013) 4193-4208 [5] http://www.labcompare.com/10-Featured-Articles/133134-Mercury-Analyzers-in-the-Laboratory [6] PD. Selid, H Xu, EM. Collins, MS Face-Collins and J X Zhao, Sensing Mercury for Biomedical and Environmental Monitoring, Sensors 9 (2009) 5446-5459 [7] JZ. James, D. Lucas, CP. Koshland, Gold Nanoparticle Films As Sensitive and Reusable Elemental Mercury Sensors, Environ. Sci. Technol. 46 (2012) 9557–9562
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E. Zampetti et al. / Procedia Engineering 120 (2015) 422 – 426 [8] TP. McNicholas, K. Zhao, C. Yang, SC. Hernandez, A Mulchandani, NV. Myung, and MA. Deshusses, Sensitive Detection of Elemental Mercury Vapor by Gold Nanoparticle Decorated Carbon Nanotube Sensors, J Phys Chem C Nanomater Interfaces. 115 (2011) 13927–13931. [9] S. Keebaugh, A.K Kalkan, WJ. Nam, and SJ. Fonash, Gold Nanowires for the Detection of Elemental and Ionic Mercury,Electrochem. SolidState Lett. 2006 9(9) H88-H91 [10] A. Macagnano, E. Zampetti, E. Kny, Electrospinning for high performance sensors, Nanoscience and Technology Series, Springer International Publisher 2015, pp. 1-329, ISBN: 978-3-319-14405-4 [11] E. Zampetti, S Pantalei, A Muzyczuk, A. Bearzotti, F De Cesare, C Spinella, A. Macagnano, A high sensitive NO 2 gas sensor based on PEDOT–PSS/TiO2 nanofibres, Sensors and Actuators B 176 (2013) 390– 398 [12] D. Li, JT. McCann, M. Gratt, Y. Xia, Photocatalytic deposition of gold nanoparticles on electrospun nanofibers of titania, Chemical Physics Letters 394 (2004) 387–391.
ScienceDirect Procedia Engineering 120 (2015) 422 – 426
EUROSENSORS 2015
Photocatalytically decorated Au-nanoclusters TiO2 nanofibres for elemental mercury vapor detection A. Macagnano1*, E. Zampetti , V. Perri , A. Bearzotti1, F. Sprovieri2, N. Pirrone1, G. Esposito1, F. De Cesare1,3 1
4
1
IIA-CNR, Via Salaria km 29,300, 00015 Monterotondo (Rome) ITALY; 2IIA-CNR, 87036, Arcavacata Rende (CS), ITALY 3 DIBAF-University of Tuscia, Via S. Camillo de Lellis 01100, Viterbo, ITALY 4 Physics Dep.-University of Calabria, Via Pietro Bucci, 87036, Arcavacata Rende (CS), ITALY
Abstract Electrospun nanofibrous nets of titania (anatase) were deposited on interdigitated microelectrodes and photocatalytically decorated with gold nanoclusters (AuNCs) upon UV irradiation. The resulting devices appeared to be conductive even at room temperature (Ohmic behavior), and were investigated as potential chemosensors capable of entrapping and detecting elemental mercury vapors in the atmosphere. The strong affinity and specificity of Au for Hg0 conferred to AuNCs a key role in mercury sensing, by inducing a decrease in current upon mercury adsorption. Sensors conductivity appeared not to be dependent on humidity. The resulting chemosensors are expected to be inexpensive, very stable (due to the peculiar structure), and requiring low power, low maintenance and simple equipment to work. © Published by Elsevier Ltd. This © 2015 2015The TheAuthors. Authors. Published by Elsevier Ltd.is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the organizing committee of EUROSENSORS 2015. Peer-review under responsibility of the organizing committee of EUROSENSORS 2015
Keywords: TiO2 nanofibres, electrospinning, Au nanoclusters, conductive sensors, elemental mercury, atmosphere
1. Introduction Mercury is a well-known neurotoxic (even at very low levels) and persistent worldwide pollutant1. It is emitted to the air by human activities, such as manufacturing facilities, coal power plants and artisanal small scale goal mining and from natural biogeochemical processes including those related to emissions from oceans, soil and volcanoes2,3. In the atmosphere, mercury exists in three different species: i) gaseous elemental mercury; ii) particle-bound
* Corresponding author. Tel.: +39 06 90672395; fax: +39 06 90672660. E-mail address: [email protected]
1877-7058 © 2015 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license
(http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the organizing committee of EUROSENSORS 2015
doi:10.1016/j.proeng.2015.08.657
E. Zampetti et al. / Procedia Engineering 120 (2015) 422 – 426
mercury; iii) oxidized gaseous mercury (i.e. RGM, reactive gaseous mercury), this last predominantly in watersoluble forms. The factors that determine how severe the health effects are from mercury exposure include the chemical form of Hg, the duration and the route of exposure (i.e. inhalation, ingestion, dermal contact, etc.) as well as the age of the person exposed (e.g. unborn children and infants are the most susceptible). The World Health Organization has set the current Personal Exposure Limit for Hg at 0.05 mg/cm3 or 5.6 ppbv in air. Since 2010 a European project called Global Mercury Observation System (GMOS - www.gmos.eu)3,4, expected to directly support the implementation of the Minamata Convention, has been involved in creating an international network capable of providing accurate measurements of Hg on a global scale. Up to now, air monitors are highly sensitive and capable of detecting the global mercury background, but are complex, costly and high-maintenance (requiring more than 40 monitoring sites and skilled operators). The detection and measurement of mercury is usually performed by spectroscopic methods, i.e. atomic absorption spectroscopy (AAS), atomic fluorescence spectroscopy (AFS), atomic emission spectroscopy (AES), or mass spectrometry (MS) 5. The need for fast detection systems, at low cost and low maintenance, as well as ease of use are becoming ever more urgent. Accordingly, recently there has been a significant amount of works6 which has focused on developing microsensors based nanomaterials to monitor Hg0 vapor in air. Gold nanostructures (nanoparticles, nanowires, nanorods) due to the combination of both the affinity of Au with Hg0 and the size of the structures (a few nanometers), resulted the most investigated nanomaterials for mercury detection among the several sensing strategies based on optical, gravimetric, electrochemical and conductive sensors7-9. In the present study, hybrid nanofibrous electrospun layers of TiO2 coating Pt microelectrodes were suitably designed in order to create nanostructured 3D-frameworks, potentially capable of adsorbing and revealing elemental mercury vapors in the atmosphere. Indeed, exploiting the outstanding photocatalytic properties of the nanofibres of titania, gold nanoclusters were selectively grown, under UV-light irradiation, on the electrospun titania nanofibres through the photocatalytic reduction of HAuCl4 (tetrachloroauric acid ) in the presence of an organic capping reagent. Due to the uniqueness of the resulting nanostructures (high surface to volume ratio, high fibres interconnectivity and nano-scale interstitial spaces)10 and for production rate and cost, the planned sensors were expected to be promising candidates for elemental mercury detection in traces. 2. Experimental Electrospinning solution (7.877 × 10−5 M), was prepared according to literature11. The substrates were fixed, through a suitable holder, to the collector surface (600 rpm, 21 ◦C and 35% RH) and the deposition time was set to 20 min. Fibres were annealed under oxygen atmosphere using a thermal ramp from room temperature up to 550 ◦C (1 ◦C min−1, 4h dwell time) in order to remove PVP and proceed to crystallize the metal oxide (anatase). The resulting fibrous layers were immersed into an aqueous solution containing 1.5•10-3M tetrachloroauric acid (HAuCl4) and 0.1M PVP (as capping agent). The substrate was then irradiated with UV light for specified intervals (UV lamp (365 nm) (Helios Italquartz). The samples on silicon wafers were directly employed for scanning electron microscopy (SEM, Jeol, JSM 5200, 20keV) and atomic force microscopy (AFM, Nanosurf FlexAFM, tapping mode 190Al-G, 190 kHz, 48N/m). The transducers, interdigitated electrodes (IDEs), had 40 pairs of Ti/Pt electrodes, 150 nm thick, 20 Pm width electrode, 20 Pm gap). Each chemoresistor was placed in a suitable case made of PTFE and connected to an electrometer (Keithley 6517 Electrometer). In order to test the responsiveness of the device to lower Hg concentration (measured by Tekran®2537A), a dynamic permeation tube was set up to dilute the mercurysaturated gas to the concentration range of interest, by using a mass flow controller system (4-Channel-MKS 247). 3. Results and Discussion Specifically, titania fibers (100 nm mean diameter) were decorated with gold nanoclusters (AuNCs) induced to grow selectively upon photocatalytic reduction of HAuCl4 caused by UV light irradiation (Fig. 1,a). Similar structures are reported in literature12 to be used to create electrospun nanofibrous filters and catalytic systems as novel abatement systems for Hg0. They reported an efficiency of about 100%. The morphology and size of gold nanoclusters and the coverage of fibres depended on UV irradiation exposure (Fig.1,b-c). When the samples were UV irradiated for 1 hour, fibres were completely covered with Au particles (confirmed by SEM microanalysis, data not shown) with globular shape merged together, and numerous protruding buds, densely clustered and overlapping (SEM and AFM
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micrographs in Fig.1). On the contrary, when fibres were exposed to UV irradiation for a shorter time (30 min), they appeared more homogeneously coated with round-shaped nanoparticles.
Figure 1. (a)Optical micrographs of the electrodes before(top) and after electrospun deposition (in the middle) and a picture of the samples (down) in solution and under UV irradiation; SEM (b) and AFM (c) micrographs of titania nanofibres after 60 min and 30 min of UV exposure, respectively. The chemical reaction can be monitored by the color change of the solution (colorless>orange>red>purple).
The sensors coated with both structures showed Ohmic behavior in air and at room temperature (Figure 2), but with different resistance values depending on the quality of the coverage, as expected. In the present study we reported the preliminary results related to sensors coated with 1h UV-irradiated fibres (the most conductive sensors, R=580650 Ohm). Oxygen and relative humidity did not affect the electrical parameters of the sensors, thus comparable electrical features were reported when measurements were carried out under nitrogen or air (Figure 2, left) and increasing percentages of relative humidity (Figure 2,right). The strong affinity and specificity of Au for Hg0 explain the sensitive responsiveness of Au nanoclusters (AuNCs) on the nanofibrous scaffolds to mercury3, highlighted by the current changes of the sensors upon Hg adsorption.
Figure 2 (Left): Current-Voltage curve of 1h-UV-exposed sensor under air (black line) and nitrogen (red one) flow; (right) sensor transient response (current) to increasing percentage of relative humidity (10%-70% %RH) (0.5V).
E. Zampetti et al. / Procedia Engineering 120 (2015) 422 – 426
425
In detail, sensors exposed to mercury vapours, pointed out a decrease in current, and the slope of the electrical signals seemed to be dependent on analyte concentration. When a sensor was exposed overnight to high concentration of Hg (PV=1.6•10-3 mbar), its resistance changed by 30% (Fig. 3, a). In order to test the responsiveness of the device to low Hg concentration, mercury vapours were flushed, from a dynamic permeation tube, throughout the measuring chamber. The final Hg0 concentration was obtained by tuning the oven temperature and the dilution flow. Preliminary results showed that the exposure of a sensor to 7.5ng/l of Hg resulted in decreasing current, with a rate of ~109 nA/min (+2V) and a limit of detection about 0.18 ng/l (LOD: three times the standard deviation of the blank) (Figure 3, b).Quick thermal shots restored sensors, due to the high porosity of the layer and the extremely reduced size of the gold nanoclusters.
Figure 3. a) Diagram of the change of resistance values of the sensor after 1 and 12 hour of exposure to mercury vapour (1.6 •10 -3 mbar); b) Sensor responses (current values) to 10 sccm-flow of mercury-saturated air (~7.5 ng/l) over time (30-90 min)
4. Conclusions Electrospinning was confirmed to be a very promising nanotechnology for developing smart and ultra-sensitive sensing systems. Exploiting the excellent photocatalytic properties of the nanofibrous titania, the sensing layer was decorated with gold nanoparticles (AuNPs) by immersing the electrospun material, into a solution containing HAuCl4 under UV irradiation. AuNCs played an active role in mercury sensing, increasing the active surface area, improving both diffusion inside the layer and the sensor conductivity. The resulting sensors, functioning in air and at room temperature, showed constant and low level of resistance, thus providing the potential to work at very low voltage values (low power, slow sensor degradation). The response curve of the tested sensors to increasing concentrations of mercury vapor reported a general decrease in current. These attracting sensing features sound as encouraging premises to develop sensors for elemental mercury based on electrospun fibres of gold nanofunctionalised titania. References [1] J. Qui, Tough talk over mercury treaty, Nature 493(2013) 144–145. [2] N. Pirrone, W. Aas., S. Cinnirella, R. Ebinghaus, I. M. Hedgecock, J. M. Pacyna, F. Sprovieri, E. M. Sunderland (2013) Toward the next generation of air quality monitoring: Mercury. Atmospheric Environment, doi:10.1016/j. atmosenv.2013.06.053. [3] Lubick, N., Fundign Struggle for Mercury monitoring (2013) Nature, 459, 620-621 (2009) | doi:10.1038/459620b [4] S. Cinnirella, F. D’Amore, M. Bencardino, F. Sprovieri, N. Pirrone, The GMOS cyber(e)-infrastructure: advanced services for supporting science and policy, Environmental Science and Pollution Research 21 (2013) 4193-4208 [5] http://www.labcompare.com/10-Featured-Articles/133134-Mercury-Analyzers-in-the-Laboratory [6] PD. Selid, H Xu, EM. Collins, MS Face-Collins and J X Zhao, Sensing Mercury for Biomedical and Environmental Monitoring, Sensors 9 (2009) 5446-5459 [7] JZ. James, D. Lucas, CP. Koshland, Gold Nanoparticle Films As Sensitive and Reusable Elemental Mercury Sensors, Environ. Sci. Technol. 46 (2012) 9557–9562
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E. Zampetti et al. / Procedia Engineering 120 (2015) 422 – 426 [8] TP. McNicholas, K. Zhao, C. Yang, SC. Hernandez, A Mulchandani, NV. Myung, and MA. Deshusses, Sensitive Detection of Elemental Mercury Vapor by Gold Nanoparticle Decorated Carbon Nanotube Sensors, J Phys Chem C Nanomater Interfaces. 115 (2011) 13927–13931. [9] S. Keebaugh, A.K Kalkan, WJ. Nam, and SJ. Fonash, Gold Nanowires for the Detection of Elemental and Ionic Mercury,Electrochem. SolidState Lett. 2006 9(9) H88-H91 [10] A. Macagnano, E. Zampetti, E. Kny, Electrospinning for high performance sensors, Nanoscience and Technology Series, Springer International Publisher 2015, pp. 1-329, ISBN: 978-3-319-14405-4 [11] E. Zampetti, S Pantalei, A Muzyczuk, A. Bearzotti, F De Cesare, C Spinella, A. Macagnano, A high sensitive NO 2 gas sensor based on PEDOT–PSS/TiO2 nanofibres, Sensors and Actuators B 176 (2013) 390– 398 [12] D. Li, JT. McCann, M. Gratt, Y. Xia, Photocatalytic deposition of gold nanoparticles on electrospun nanofibers of titania, Chemical Physics Letters 394 (2004) 387–391.