# US 7,238,328 B2 · Solid-state light source photolytic nitrogen dioxide converter > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 7,238,328 B2 - Document ID: US7238328B2 - Status: Granted - Kind: B2 - Application number: 10/313,827 - Filed: 2002-12-06 - Published: 2004-06-10 - Granted: 2007-07-03 - Earliest claimed: 2002-12-06 - Assignees: Sonoma Technology - Inventors: Martin Patrick Buhr - Web page: https://patentgrep.com/patent/US7238328B2 ## CPC - G01N 21/05: Flow-through cuvettes (G01N21/09 takes precedence; handling fluid samples G01N1/10) - G01N 21/631: {using photolysis and investigating photolysed fragments} - G01N 31/005: {investigating the presence of an element by oxidation (G01N31/12 takes precedence)} - G01N 33/0037: {NOx} - G01N 2021/0325: {Cells for testing reactions, e.g. containing reagents} - 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 A solid-state light source photolytic NO2 converter including a reaction chamber made of a reflective material with diffuse reflective properties, whereby the reaction chamber includes a low volume gas cell wherein the gas sample residence time is less than 5 seconds is provided. The NO2 in the air sample is exposed to ultraviolet radiation at wavelengths less than 420 nm, whereby the NO2 is converted to NO. The NO is subsequently measured using an NO analyzer. The solid-state light source includes diode lasers and LED's that emit UV wavelength in the range of 350–420 nm. The use of a narrow wavelength range afforded by the solid-state light source results in an interference-free conversion of NO2 to NO at high efficiency. ## Claims ### Claim 1 A photolytic NO2 converter for converting NO2 present in a gas sample into NO, comprising: a body including a reaction chamber that possesses diffuse reflective properties located substantially within said body, said reaction chamber possessing at least one aperture, said reaction chamber being highly reflective, having a reflective efficiency of at least 0.95 for light in the ultraviolet wavelength range; a reaction chamber inlet in communication with said reaction chamber for transporting a gas sample into said reaction chamber; a reaction chamber outlet in communication with said reaction chamber for transmitting a processed gas sample out of said reaction chamber; and at least one low-power light-emitting diode (LED) configured to produce UV wavelength radiation in the range of 350–420 nm optimally situated at the overlap of high NO2 adsorption and quantum yield located substantially adjacent to said at least one aperture to enable UV wavelength radiation to pass from said at least one low-power LED into said reaction chamber through said at least one aperture, for converting NO2 present in a gas sample transported into said reaction chamber by said reaction chamber inlet into NO in a processed gas sample for transportation out of said reaction chamber by said reaction chamber outlet, said reaction chamber having a volume for providing a residence time of said processed gas sample in said reaction chamber of less than 5 seconds. ### Claim 2 (depends on 1) The photolytic NO2 converter as in claim 1, further comprising: NO detector means, in communication with said reaction chamber outlet, for generating a signal indicative of a concentration of NO in said processed gas sample. ### Claim 3 (depends on 1) The photolytic NO2 converter as in claim 1, further comprising: at least one heat sink mounted to said body and located substantially near said at least one low-power LED. ### Claim 4 (depends on 1) The photolytic NO2 converter as in claim 1, further comprising: at least one thermoelectric cooling device mounted to said body and located substantially near said at least one low-power LED. ### Claim 5 (depends on 1) The photolytic NO2 converter as in claim 1, wherein said diffuse reflective properties are produced by a material selected from the group consisting of materials and Barium Sulfate polytetrafluoroethylene (Teflon). ### Claim 6 (depends on 1) The photolytic NO2 converter as in claim 1, further comprising: a means for controllably introducing the gas sample to the reaction chamber, said reaction chamber, and said means for controllably introducing said gas sample to the reaction chamber, each comprises a volume which minimizes a residence time of the gas sample in said photolytic NO2 converter. ### Claim 7 A photolytic NO2 converter for converting NO2 present in a gas sample into NO, comprising: a body including a reaction chamber that possesses diffuse reflective properties by a polytetrafluoroethylene (Teflon) material, said reaction chamber located substantially within said body and possessing at least one aperture, said reaction chamber having a reflective efficiency of at least 0.95 for light in the ultraviolet wavelength range; a reaction chamber inlet in communication with said reaction chamber for transporting a gas sample into said reaction chamber, a reaction chamber outlet in communication with said reaction chamber for transmitting a processed gas sample out of said reaction chamber; and at least one light-emitting diode (LED) configured to produce UV wavelength radiation in the range of 350–420 nm optimally situated at the overlap of high NO2 adsorption and quantum yield, located substantially adjacent to said at least one aperture to enable UV wavelength radiation to pass from said at least one LED into said reaction chamber through said at least one aperture, for converting NO2 present in a gas sample transported into said reaction chamber by said reaction chamber inlet into NO in a processed gas sample for transportation out of said reaction chamber by said reaction chamber outlet, said reaction chamber having a volume for providing a residence time of said processed gas sample in said reaction chamber of less than 2 seconds.