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Portable Room Temperature Ammonia Sensor
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  • Detail Technical Brochure
  • Application Procedure
Portable Room Temperature Ammonia Sensor
Overview

NH3 is one of the highly toxic gases which is widely used in various industrial applications. It causes irritation in nose and throat, and in extreme case causes severe lungs problem (pulmonary edema). Nanocrystalline SnO2 thin film based portable sensor detects NH3 from 5 ppm onwards at room temperature with fast response and recovery. The sensor works on the principle of increase in electrical resistance upon a chemical interaction with NH3.

Commercially available SnO2 gas sensors for NH3 are usually operated at high temperature to achieve reversibility and fast response. Shortcomings of high temperature operation of the sensor are: shorter life time, does not have portability and is not favorable in explosive environment.

Portable Room Temperature Ammonia Sensor

   Sensor for on-site monitoring

 

Quick View Leaflet

Gas sensors are usually operated at high temperature to achieve fast response and reversibility and this leads to shorter lifetime of the sensor. Nanocrystalline SnO2 thin films fabricated from the thermal decomposition of Langmuir-Blodgett (LB) film precursor, exhibit room temperature gas sensitivity comparable to that required for air quality monitoring. LB technique offers control over SnO2 film thickness and crystallite size. By controlling the crystallite size and film thickness room temperature operation is achieved. The sensor is specific to NH3 gas at room temperature and shows fast response and recovery without any carrier gas flow. The stability studies of the sensor indicated that these sensors are stable at least for a year with no significant change in sensitivity.

ADVANTAGES

  • Room temperature operation, low power requirement and portable.

  • Reliable over a period of 1 year.

SPECIFICATIONS

  • NH3 detection range
: 5-40 ppm

  • Operating temperature
: Room temperature
  • Safe operating temperature
: 25-50°C
  • Response time (time to reach 90% of the resistance change)
: 40 sec
  • Recovery time (time to reach 10% of the resistance change)
: 20 min
  • Response at 5 ppm NH3 [(Rgas - Rair)x100]/Rair
: 10-15%
  • Selectivity for NH3 (comparison to CH4, CO2, H2S, SO2, H2 etc.)
: Detectable decrease in current only for NH3 among these gases
  • Life time under operating conditions
: ~ 1 year


APPLICATIONS

  • Heavy water plants

  • Fertilizer plants

  • Pollution monitoring agencies
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Detail Technical Brochure


NH3 is one of the highly toxic gas, which is widely used in various industrial applications. It  causes irritation in nose and throat and  in extreme case it causes severe lungs problem (pulmonary edema). Its long-term (8 h) and short-term (10 minutes) exposure limits are 25 and 50 ppm respectively. The nanocrystalline tin oxide (SnO2) thin film based sensor detects NH3 with high sensitivity, is selective to NH3 among other reducing gases, and is stable for more than 1 year. Commercially available SnO2 gas sensors are usually operated at high temperature to achieve reversibility and fast response. High temperature operation causes shorter life time and not favorable in explosive environment.

WORKING PRINCIPLE

The sensor works on the principle of change in electrical resistance of nanocrystalline SnO2 thin film upon chemical interaction with NH3. This change is calibrated and displayed directly on a monitor as NH3 concentration.

Preparation of SnO2 thin film and sensing mechanism :

The sensor element is nanocrystalline SnO2 thin film which is prepared by using Langmuir- Blodgett (LB) film precursors. Multilayer LB films (100 ± 20 layers) of ODA–stannate complex deposited on quartz are decomposed at 600 °C in the presence of ambient oxygen.

Nanocrystalline SnO2 surface has a net negative charge due to the large number of surface species O2-,O- present on it. NH3 which is a mild reducing gas, a polar molecule containing partial positive charge on its H atoms. When NH3 gas is injected into the gas testing chamber containing SnO2 thin film, it reduces the mobility of the electrons in SnO2, thereby increasing the resistance. This makes the sensor unique and specific to ammonia at room temperature.

SPECIFICATIONS

Property Value
  • Drift in base current

: 2-3 %

  • Sensitivity (towards NH3)
    S=((RNH3-Rair)x 100)/Rair
: 10-15 % at 5 ppm of NH3
  • Response time
: 40 sec
  • Recovery time (after opening of stopcocks, without any carrier gas flow) 
: 20 min for 90 % recovery
  • Range of the sensor 
: 3-40 ppm
  • Reproducibility after a year
    (towards NH3)
: Sensitivity intact
Response time : 200 sec
Recovery time : 1 hr
  • Repeatability 
: 90%
  • Percentage error in sensitivity
: 10-15%
  • Sensor Housing
: Water and light proof

Selectivity in presence of other gases

Selectivity and Sensitivity (as change in current )
Gas Change in current Gas concentration
  • NH3

decrease

1 ppm

  • H2

no change

6 ppm
  • H2O

no change

< 97% RH
  • CO

no change

6 ppm
  • H2S

increase

< 1 ppm
  • SO2

increase

< 1 ppm
  • NO2

decrease (with no recovery at room temperature, recovery only after heating at 70°C for 2 hours)

< 85 ppb
  • Conclusion
Sensor is highly selective for NH3 in presence of other gases (except for NO2 gas) as mentioned above in the table.

APPLICATIONS

  • Heavy water plants
  • Fertilizer plants
  • Pollution monitoring agencies

REQUIREMENTS FOR SENSOR PREPARATION

A. Raw materials

  1. Chemicals: Octadecyl amine, Choloroform and Sodium stannate
  2. Distilled water for making sodium stannate solution
  3. Quartz substrates (1cm x 2 cm) for film deposition
  4. Gold (24 ct, for contact electrodes deposition)

B. Equipments

  1. LB trough or stepper motor controlled deposition unit
  2. Furnace for heating at 600°C
  3. Thermal evaporation system for gold contact electrode deposition
  4. Enclosure for keeping the film, connector cable
  5. Calibration chamber
  6. Gas canisters and syringes (Electronics for the sensor is not included)

C. Space

  • The space requirement is approximately 12ft by 15ft to comfortably accommodate the process equipments such as LB trough, CVD system, Furnace, space for assembling and packaging, testing and calibration setup etc.

MANPOWER REQUIREMENT

2 Numbers :

  • 1 person with B.Sc. degree in Physics/Chemistry
  • 1 person with diploma in Electrical/Electronics

Who Should apply


Interested parties with Engineering & Scientific knowledge, good financial background and adequate experience of products manufacturing & fabrication with technical capability in the area of interested technology and having or interested in setting –up facilities for production would be preferred.


How to apply

Send your Technology Transfer Application form duly filled and signed alongwith a Demand Draft/Bankers cheque of Rs. 500/- (for Indian entities) or US $50/- (for foreign entities) drawn in favour of “Accounts Officer, BARC” as application processing fee on following address: 

Head, Technology Transfer and Collaboration Division 
Bhabha Atomic Research Centre,
Trombay, Mumbai – 400 085, India.

Fax : +91-22-25505151


Note:Applications without processing fee as applicable above of Rs. 500/- or US $50/- for each technology will not be considered.


Click here for Technology Transfer Application Form

Contact Us

Head, 
Technology Transfer and Collaboration Division
Bhabha Atomic Research Centre,
Trombay, Mumbai 400 085.

Tel  : 091-022-25595137
Fax : 091-022- 25505151
Email : technology@barc.gov.in

How to apply

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