Date of download: 6/28/2016 Copyright © 2016 SPIE. All rights reserved. (a) General concept of the colorimetric sensor of ammonia: 1—light emitter, 2—input light beam, 3—input window, 4—light transmitting/sensing element, 5—output light beam, 6—output window, 7—photodetector, 8—electronic module, 9—power supply, 10—enclosure, 11—gas permeable membrane, 12—gas in, 13—gas out, 14—data logger. (b) Schematic of the old, planar optical waveguide configuration of the sensor: 4.1—input coupling hardware based on a prism that couplers input light beam 2 in the planar waveguide using thin film of reagent 4, 4.2—substrate, 4.3—output optical coupler. (c) New configuration of the proposed sensor: optical window 3 serves as the substrate for the reagent layer 4. L is the distance the light travels through the reagent. Figure Legend: From: Colorimetric polymer-metal nanocomposite sensor of ammonia for the agricultural industry of confined animal feeding operations Opt. Eng. 2013;53(2): doi: /1.OE

Date of download: 6/28/2016 Copyright © 2016 SPIE. All rights reserved. Evolution of the optical absorption spectrum of the reagent made of polyimide and bromocresol purple (BCP): 1—spectrum of the freshly made film; 2—spectrum of the film exposed to ammonia ( ∼ 10,000-ppm concentration in air); 3—spectrum 3 min after the exposure stopped; 4—spectrum 3 h after the exposure. The film was deposited on a glass substrate using dipping followed by baking in an oven. Figure Legend: From: Colorimetric polymer-metal nanocomposite sensor of ammonia for the agricultural industry of confined animal feeding operations Opt. Eng. 2013;53(2): doi: /1.OE

Date of download: 6/28/2016 Copyright © 2016 SPIE. All rights reserved. Differential optical absorption spectra between the reagent doped with gold nanoparticles and the reagent without nanoparticles (Fig. 2). Curve 1 corresponds to the case when both samples (previously exposed to ammonia numerous times) stayed in air without ammonia; 2—samples exposed to the same amount of ammonia ( ∼ 10,000-ppm concentration) until the absorption was saturated; 3—at >3 h after ammonia is removed. Curve 4 is the optical extinction spectrum of the aggregated Au nanocolloid in GBL used for preparing the reagent film. O.D. stands for optical density=−[log(transmittance)]. Figure Legend: From: Colorimetric polymer-metal nanocomposite sensor of ammonia for the agricultural industry of confined animal feeding operations Opt. Eng. 2013;53(2): doi: /1.OE

Date of download: 6/28/2016 Copyright © 2016 SPIE. All rights reserved. (a) Response of the “bare” sensor (without the air filter attached) to 74.3 ppm ammonia (in air) at a flow rate of ∼ 10 mL/min; rise time was 0.6 min (from 0% to 90% maximum), fall time—33 min (from maximum to 10% maximum after the exposure is stopped). (b) Typical calibration plot of the sensor. Baseline=1.155 V. Figure Legend: From: Colorimetric polymer-metal nanocomposite sensor of ammonia for the agricultural industry of confined animal feeding operations Opt. Eng. 2013;53(2): doi: /1.OE

Date of download: 6/28/2016 Copyright © 2016 SPIE. All rights reserved. Sensor baseline (at zero ammonia) signal versus time along with the temperature and relative humidity. The relative humidity curve is turned over for easy comparison. Figure Legend: From: Colorimetric polymer-metal nanocomposite sensor of ammonia for the agricultural industry of confined animal feeding operations Opt. Eng. 2013;53(2): doi: /1.OE

Date of download: 6/28/2016 Copyright © 2016 SPIE. All rights reserved. Sensor baseline signal plotted versus temperature. Solid line represents the result of the linear regression analysis. Figure Legend: From: Colorimetric polymer-metal nanocomposite sensor of ammonia for the agricultural industry of confined animal feeding operations Opt. Eng. 2013;53(2): doi: /1.OE

Date of download: 6/28/2016 Copyright © 2016 SPIE. All rights reserved. Sensor baseline signal plotted versus reversed relative humidity. Figure Legend: From: Colorimetric polymer-metal nanocomposite sensor of ammonia for the agricultural industry of confined animal feeding operations Opt. Eng. 2013;53(2): doi: /1.OE

Date of download: 6/28/2016 Copyright © 2016 SPIE. All rights reserved. Installation diagram of the sensor in a commercial poultry house. Figure Legend: From: Colorimetric polymer-metal nanocomposite sensor of ammonia for the agricultural industry of confined animal feeding operations Opt. Eng. 2013;53(2): doi: /1.OE

Date of download: 6/28/2016 Copyright © 2016 SPIE. All rights reserved. Ammonia level measured by the sensor inside the plastic container simulating a concentrated animal feeding operations (CAFO) facility. The spike of ammonia followed the injection of a few drops of ammonium hydroxide inside the container. The sensor kicked in ventilation when the ammonia level exceeded 25 ppm. Figure Legend: From: Colorimetric polymer-metal nanocomposite sensor of ammonia for the agricultural industry of confined animal feeding operations Opt. Eng. 2013;53(2): doi: /1.OE

Date of download: 6/28/2016 Copyright © 2016 SPIE. All rights reserved. Ammonia concentration during the flock feeding period as measured by the proposed sensor and the photoacoustic analyzer. The measurements were conducted by the research team of the University of Georgia in Athens in a commercial poultry house between March 23 and April 10, Figure Legend: From: Colorimetric polymer-metal nanocomposite sensor of ammonia for the agricultural industry of confined animal feeding operations Opt. Eng. 2013;53(2): doi: /1.OE

Date of download: 6/28/2016 Copyright © 2016 SPIE. All rights reserved. Photoacoustic analyzer readings from Fig. 10 plotted versus the readings of the proposed sensor. Measurements were conducted by the University of Georgia in Athens between March 23 and April 10, Figure Legend: From: Colorimetric polymer-metal nanocomposite sensor of ammonia for the agricultural industry of confined animal feeding operations Opt. Eng. 2013;53(2): doi: /1.OE

Date of download: 6/28/2016 Copyright © 2016 SPIE. All rights reserved. (a) The view of the two proposed sensors co-located with the air filter used as inlet for the Innova analyzer in a commercial poultry house at the University of Arkansas (UArk). (b) Inside view of the instrumentation trailer at the UArk that housed the data acquisition system for the gas analyzer Innova and the data loggers of the house ventilation rates, T/RH, etc. Figure Legend: From: Colorimetric polymer-metal nanocomposite sensor of ammonia for the agricultural industry of confined animal feeding operations Opt. Eng. 2013;53(2): doi: /1.OE

Date of download: 6/28/2016 Copyright © 2016 SPIE. All rights reserved. Ammonia concentration readings from the proposed sensor and from the Innova from December 10 to 20, 2010 (flock sold March 3, 2011), at the commercial poultry house of the UArk. Figure Legend: From: Colorimetric polymer-metal nanocomposite sensor of ammonia for the agricultural industry of confined animal feeding operations Opt. Eng. 2013;53(2): doi: /1.OE

Date of download: 6/28/2016 Copyright © 2016 SPIE. All rights reserved. Raw voltage output from the two proposed ammonia sensors placed side by side in a poultry house at a commercial farm of the UArk and the ammonia level in the same spot in the house measured by the photoacoustic gas analyzer Innova between March 14 and 23, Sensors 1 and 2 are the copies of the same proposed sensor. The significant difference in the magnitude of their raw voltage outputs was the result of the poor reproducibility of the individual fabrication procedures on the prototyping stage of the product development. This deficiency (of the technical nature) would be solved on the transition to the mass scale commercial production. Figure Legend: From: Colorimetric polymer-metal nanocomposite sensor of ammonia for the agricultural industry of confined animal feeding operations Opt. Eng. 2013;53(2): doi: /1.OE

Date of download: 6/28/2016 Copyright © 2016 SPIE. All rights reserved. Ammonia level measured by Innova plotted versus the ammonia level measured by proposed Sensor 1 placed in a poultry house at a commercial farm of the UArk. Period of testing is March 14 to March 23, Figure Legend: From: Colorimetric polymer-metal nanocomposite sensor of ammonia for the agricultural industry of confined animal feeding operations Opt. Eng. 2013;53(2): doi: /1.OE