# US 10,768,135 B2 · Oxidizing gas detection method and apparatus thereof > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,768,135 B2 - Document ID: US10768135B2 - Status: Granted - Kind: B2 - Application number: 15/855,933 - Filed: 2017-12-27 - Published: 2019-06-27 - Granted: 2020-09-08 - Earliest claimed: 2017-12-27 - Assignees: Industrial Technology Research Institute - Applicants: Industrial Technology Research Institute - Inventors: I-Cherng Chen; Pi-Guey Su; Hong-Ci Syu; Hui-Yu Cho; Pin-Chou Li; Jian-Hong Wu; Ren-Der Jean - Web page: https://patentgrep.com/patent/US10768135B2 ## CPC - G01N 27/27: Association of two or more measuring systems or cells, each measuring a different parameter, where the measurement results may be either used independently, the systems or cells being physically associated, or combined to produce a value for a further parameter - G01N 27/305: {optically transparent or photoresponsive electrodes} - G01N 27/4065: {Circuit arrangements specially adapted therefor} - G01N 27/407: for investigating or analysing gases {(G01N27/411 takes precedence)} - G01N 33/0037: {NOx} - G01N 33/0039: {O3} - Y02A 50/20: Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters - G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q) - Y02A: TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE ## Abstract An oxidizing gas detection method and an apparatus thereof are provided for trace oxidizing gas detection. The detection method includes the following steps. First, perform an electroreduction reaction and a photoreduction reaction simultaneously to a metal oxide in which nanoconductors are distributed. Next, stop the electroreduction reaction and the photoreduction reaction, and read a resistance of the reduced metal oxide by applying a first pulse-width modulation signal. Next, provide an oxidizing gas to the reduced metal oxide, and photo-catalyze a redox reaction between the oxidizing gas and the reduced metal oxide. Next, read a resistance of the oxidized metal oxide by applying a second pulse-width modulation signal. Next, converse a concentration of the oxidizing gas according to a ratio of the resistance of the oxidized metal oxide and the resistance of the reduced metal oxide. ## Claims ### Claim 1 A method for detecting concentration of an oxidizing gas comprising: providing a gas detecting module with the gas detecting module comprising a metal oxide and a plurality of nanoconductors, wherein the plurality of nanoconductors are distributed in the metal oxide; performing an electroreduction reaction and a photoreduction reaction simultaneously to the metal oxide; stopping the electroreduction reaction and the photoreduction reaction to the metal oxide; applying a first pulse-width modulation signal for reading a reduction-state resistance of a reduced metal oxide; providing the oxidizing gas to the reduced metal oxide; performing a redox reaction by photo-catalyzing the oxidizing gas and the reduced metal oxide; applying a second pulse-width modulation signal for reading an oxidation-state resistance of the oxidized metal oxide; and calculating the concentration of the oxidizing gas according to a ratio of the oxidation-state resistance to the reduction-state resistance. ### Claim 2 (depends on 1) The method for detecting concentration of an oxidizing gas according to claim 1, wherein performing the electroreduction reaction to the metal oxide is to apply a voltage of 5 to 10 volts to the metal oxide. ### Claim 3 (depends on 1) The method for detecting concentration of an oxidizing gas according to claim 1, wherein performing the photoreduction reaction to the metal oxide is to irradiate the metal oxide with a light with a wavelength of 254 to 430 nanometers. ### Claim 4 (depends on 1) The method for detecting concentration of an oxidizing gas according to claim 1, wherein a time for performing the electroreduction reaction and the photoreduction reaction simultaneously to the metal oxide is 0.1 to 5 minutes. ### Claim 5 (depends on 1) The method for detecting concentration of an oxidizing gas according to claim 1, wherein a step of stopping the electroreduction reaction and the photoreduction reaction to the metal oxide is to stop performing the photoreduction reaction firstly, then to stop performing the electroreduction reaction after 0.1 to 5 minutes. ### Claim 6 (depends on 1) The method for detecting concentration of an oxidizing gas according to claim 1, wherein the first pulse-width modulation signal is a pulse-width modulation signal with voltage ranging from 3 to 7 volts and with frequency ranging from 5 to 15 hertz. ### Claim 7 (depends on 1) The method for detecting concentration of an oxidizing gas according to claim 1, wherein time for applying the first pulse-width modulation signal is 0.1 to 1000 milliseconds. ### Claim 8 (depends on 1) The method for detecting concentration of an oxidizing gas according to claim 1, wherein a step of performing the redox reaction by photo-catalyzing the oxidizing gas and the reduced metal oxide is to apply a monochromatic light with a wavelength of 550 to 950 nanometers to irradiate a contact surface of the reduced metal oxide and the oxidizing gas. ### Claim 9 (depends on 1) The method for detecting concentration of an oxidizing gas according to claim 1, wherein a step of performing the redox reaction by photo-catalyzing the oxidizing gas and the reduced metal oxide is to apply a two-color composite light with a wavelength of 550 to 950 nanometers to irradiate a contact surface of the reduced metal oxide and the oxidizing gas. ### Claim 10 (depends on 1) The method for detecting concentration of an oxidizing gas according to claim 1, wherein the second pulse-width modulation signal is a pulse-width modulation signal with voltage ranging from 3 to 7 volts and with frequency ranging from 5 to 15 hertz. ### Claim 11 (depends on 1) The method for detecting concentration of an oxidizing gas according to claim 1, wherein a time for applying the second pulse-width modulation signal is 0.1 to 1000 milliseconds. ### Claim 12 (depends on 1) The method for detecting concentration of an oxidizing gas according to claim 1, wherein the oxidizing gas is nitrogen dioxide or ozone. ### Claim 13 (depends on 1) The method for detecting concentration of an oxidizing gas according to claim 1, wherein a step of performing the redox reaction by photo-catalyzing the oxidizing gas and the reduced metal oxide is performed at room temperature. ### Claim 14 An apparatus for detecting concentration of an oxidizing gas comprising: a gas detecting module comprising a metal oxide and a plurality of nanoconductors, wherein the plurality of nanoconductors are distributed in the metal oxide, and the metal oxide is configured to perform a redox reaction with the oxidizing gas; a light module comprising a photoreducing light and at least one photocatalytic light, wherein the photoreducing light is configured to irradiate and drive the metal oxide to be photoreduced, and said at least one photocatalytic light is configured to catalyze a reaction of the oxidizing gas with a reduced metal oxide so that the oxidizing gas is reduced; and a control module electrically connected to the gas detecting module and the light module, wherein the control module is configured to drive the metal oxide to be electroreduced and photoreduced in a constant voltage mode, and to detect a reduction-state resistance of the reduced metal oxide and an oxidation-state resistance of the oxidized metal oxide in a pulse-width modulation mode, wherein the reduction-state resistance and the oxidation-state resistance are configured to calculate a concentration of the oxidizing gas. ### Claim 15 (depends on 14) The apparatus for detecting concentration of an oxidizing gas according to claim 14, wherein the control module comprises a pulse-width modulator and a controller, the gas detecting module electrically connects to a power source through the controller in the constant voltage mode, and the gas detecting module electrically connects to the power source through the controller and the pulse-width modulator in the pulse-width modulation mode. ### Claim 16 (depends on 15) The apparatus for detecting concentration of an oxidizing gas according to claim 15, wherein the gas detecting module further comprises a first electrode and a second electrode, the metal oxide only electrically connects to the first electrode and the second electrode directly, and the first electrode electrically connects to the controller. ### Claim 17 (depends on 14) The apparatus for detecting concentration of an oxidizing gas according to claim 14, wherein the photoreducing light is a light source with a wavelength of 254 to 430 nanometers, and said at least one photocatalytic light is a light source with a wavelength of 550 to 950 nanometers. ### Claim 18 (depends on 17) The apparatus for detecting concentration of an oxidizing gas according to claim 17, wherein said at least one photocatalytic light comprises two photocatalytic lights with different wavelengths. ### Claim 19 (depends on 14) The apparatus for detecting concentration of an oxidizing gas according to claim 14, wherein the photoreducing light is a light source with a wavelength of 365 nanometers, and the photocatalytic light comprises a near-infrared light source with a wavelength of 850 nanometers and a visible light source with a wavelength of 950 nanometers. ### Claim 20 (depends on 14) The apparatus for detecting concentration of an oxidizing gas according to claim 14, wherein the metal oxide is tungsten trioxide or titanium dioxide. ### Claim 21 (depends on 14) The apparatus for detecting concentration of an oxidizing gas according to claim 14, wherein the plurality of nanoconductors is carbon nanotube, graphene, polyacetylene, polythiophene (PT), polypyrrole (PPY), polyaniline (PANI) or poly(3,4 ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT-PSS). ### Claim 22 (depends on 14) The apparatus for detecting concentration of an oxidizing gas according to claim 14, wherein the gas detecting module further comprises a nano-metal catalyst layer, the nano-metal catalyst layer is disposed on a surface of the metal oxide, the nano-metal catalyst layer is configured to catalyze the oxidizing gas and the metal oxide to perform a redox reaction. ### Claim 23 (depends on 22) The apparatus for detecting concentration of an oxidizing gas according to claim 22, wherein a material of the nano-metal catalyst layer is gold, silver or palladium. ### Claim 24 (depends on 23) The apparatus for detecting concentration of an oxidizing gas according to claim 23, wherein a material of the nano-metal catalyst layer is a mixture of gold and silver.