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What it is

A compact Mid-Infrared (Mid-IR) sensor designed for in-situ, real-time detection of organic pollutants such as aromatic hydrocarbons and selected pesticides. To our knowledge, this kind of portable integrated Mid-IR sensor for water organics is unique worldwide.

What it measures

  • Aromatic hydrocarbons (BTX: benzene, toluene, xylenes)
  • Pesticides: cypermethrin, nicosulfuron, dicamba
  • Current project focus: toluene and cypermethrin

Current Status

TRL   4 – validated at lab scale (non-integrated)
Readiness   Lab testing with realistic water matrices (seawater, wastewater, freshwater)
Environment   Low-temperature water, realistic salinity and matrix conditions

Performance so far

  • Detection limits (LOD) (indicative values in water):
    • BTX: ~100 μg/L
    • Toluene: ~250 μg/L
    • Cypermethrin: ~10,000 μg/L (ongoing optimisation)
  • Quantification ranges (current best performance):
    • BTX: 150 μg/L – 200 mg/L
    • Toluene: 750 μg/L – 520 mg/L
    • Cypermethrin: 10,000 μg/L – 300 mg/L
  • Response time
    • Full equilibrium: typically 30–90 minutes, depending on analyte, polymer and configuration
    • Calibration-grade signal (T63): from ~5–25 minutes, and down to ~5–6 minutes in the microfluidic cell for BTX and toluene with PIB polymer

Key Innovations

  • Chalcogenide glass IR photonic waveguides that transmit light up to ~20 μm, enabling broadband IR sensing of organics.
  • Polymer functionalisation of the sensing surface, with:
    • Petrochemical polymers (PIB, PDMS) (Figure 1)  and
    • Bio-based polyhydroxyalkanoates (PHAs) (Figure 2) as a more sustainable alternative. PHAs have been successfully used for IR detection of BTX and pesticides; PIB currently gives the most versatile performance.
  • Microfluidic cell that mimics real environmental flow and temperature conditions, and shows higher sensitivity than the original ATR flow cell.

Laser, detector and system progress

  • Quantum Cascade Laser (QCL)
    • Moving from a single emitter to a 10-emitter QCL array designed for toluene detection around 6.6 μm.
  • Detector (Figure 3)
    • Target detectivity was 5×10⁹ Jones; current devices reach ~2.3×10¹⁰ Jones, significantly improving achievable LOD.
  • Transducer integration
    • Butt-coupling between QCL, chalcogenide waveguide, and detector successfully demonstrated on the lab bench.

Recent highlights

  • First use (to our knowledge) of bio-based PHAs for IR sensing of water pollutants.
  • Successful detection of pesticides in water with the ATR-FTIR system.
  • Confirmed operation in seawater and wastewater, bringing the system closer to realistic in situ operation.

Results Gallery (click on the image to enlarge it!)

Figure 1: SEM micrograph of a cross-section of 5 µm thick polyisobutylene film deposited on chalcogenide waveguide (Se4 for guiding layer and Se2 for buffer layer) on Si substrate.

Figure 2: SEM micrograph of: a) P3HB4HB; b) PH3HB3HV; c) PHBHH and d) PHO films prepared with dichloromethane deposited on chalcogenide (Se4) glass film (1 µm) on a silicon wafer

Figure 3: Photograph of a PVIA-4TE-8-TO8-wZnSeAR-36 detector

Coming soon!

Coming soon!

Coming soon!

Coming soon!