Nanocomposite of molybdenum oxide and conductive carbon for formaldehyde gas detection at room temperature
A sensor for formaldehyde gas, methods of making the same, and methods of using the same, are described.
1 . A sensor comprising:
a base transducer;
a carbon support on the base transducer;
a MoO x -based sensing element comprising MoO x on the carbon support, wherein x is from 2 to 3; and
a solid-state electrolyte on the MoO x -based sensing element;
wherein the solid-state electrolyte comprises a sulfonated tetrafluoroethylene-based fluoropolymer-copolymer.
2 . The sensor of claim 1 , wherein the MoO x -based sensing element comprises a combination of molybdenum (IV) oxide (MoO 2 ), molybdenum (V) oxide (Mo 2 O 5 ), and molybdenum (VI) oxide (MoO 3 ).
3 . The sensor of claim 1 , wherein the MoO x -based sensing element and the carbon support form a nanocomposite.
4 . The sensor of claim 1 , wherein the base transducer comprises a 2 mm gold working electrode, a Ag/AgCl reference electrode, and a Pt counter electrode.
5 . The sensor of claim 1 , comprising from 1 wt. % Mo/carbon to 30 wt. % Mo/carbon.
6 . The sensor of claim 1 , wherein the sensor is in a hand-held, portable device.
7 . The sensor of claim 1 , wherein the carbon support comprises carbon black.
8 . The sensor of claim 1 , wherein:
the carbon support comprises carbon black; and
the base transducer comprises a screen-printed gold electrode.
9 . The sensor of claim 8 , comprising from 1 wt. % Mo/carbon to 30 wt. % Mo/carbon.
10 . A method of detecting formaldehyde gas, the method comprising:
exposing the sensor of claim 1 to a gas phase comprising formaldehyde; and
measuring a change in current of the sensor to detect the formaldehyde.
11 . The method of claim 10 , wherein the formaldehyde is present in the gas phase at a concentration as low as about 5 ppb.
12 . The method of claim 10 , wherein volatile organic compounds in addition to the formaldehyde are present in the gas phase.
13 . The method of claim 10 , wherein cyclic voltammetry is used to measure the current change of the sensor.
14 . The method of claim 10 , wherein electrochemical impedance spectroscopy is used to detect an impedance change and phase angle shifts due to interfacial interaction of the formaldehyde with the MoO x -based sensing element.
15 . The method of claim 10 , wherein the formaldehyde is detected with a current change of 1.2 μA.
16 . A sensor comprising:
a base transducer;
a carbon support on the base transducer;
a MoO x -based sensing element comprising MoO x on the carbon support, wherein x is from 2 to 3; and
a solid-state electrolyte on the MoO x -based sensing element;
wherein the MoO x -based sensing element and the carbon support form a nanocomposite.