254nm Bandpass Filter

254nm light is a specific wavelength in the ultraviolet (UVC) spectrum, known for its germicidal properties as it can effectively disrupt the DNA and RNA of microorganisms.

  • Application 1: In water purification systems, the filter is used to isolate 254nm light, enabling targeted disinfection by neutralizing harmful bacteria and viruses in the water.
  • Application 2: For air sterilization in HVAC systems, the filter ensures only 254nm UVC light is transmitted, eliminating airborne pathogens such as mold spores and bacteria to improve indoor air quality.
  • Application 3: In surface disinfection of medical equipment or food processing surfaces, the filter focuses 254nm light to destroy microbial contaminants on contact, providing a chemical-free sterilization solution.

254nm Filter Selection Guide for Specific Applications

1. UV Sterilization & Disinfection Systems

Application Requirement: Utilize 254nm UV light to disrupt microbial DNA structures for high-efficiency sterilization (e.g., medical equipment, water treatment systems).Filter Configuration:

  • Central Wavelength & Bandwidth: Narrow-bandpass design at 254nm ±5nm, concentrating energy at the microbial DNA absorption peak (254nm) to achieve a sterilization efficiency >99.9%.
  • Substrate Material: JGS1-grade quartz glass, providing >85% transmittance at 254nm while completely blocking vacuum UV below 230nm to prevent ozone generation.
  • Coating Technology:
  • Multilayer dielectric coatings (e.g., HfO₂/SiO₂) with a steep cut-off slope (>40dB/oct), reducing transmittance of deep UV below 230nm to 0.01% and suppressing visible light interference.
  • Surface-applied TiO₂ photocatalytic coating to minimize transmittance decay caused by organic contamination (annual decay <3%).
  • Anti-Aging Design:
  • Quartz substrate with low thermal expansion coefficient (5.5×10⁻⁷/℃) for long-term UV radiation resistance.
  • RF ion source coating technology (e.g., KRi RFICP 380) to enhance film density and prevent layer delamination.

Selection Rationale:

  • Precision Sterilization: The narrow-bandpass design maximizes 254nm energy density, achieving irradiance >6mW/cm² when combined with quartz's high transmittance. This meets international standards (e.g., BIFMA HCF 8.1-2019) for surface disinfection dose requirements (291kJ/m²).
  • Safety Protection: Deep UV cut-off design prevents leakage of 200-240nm wavelengths, controlling ozone concentration below 0.05ppm to avoid secondary pollution.
  • Long-Term Stability: TiO₂ coating and ion-source coating technology address common aging and contamination issues, ensuring a service life >5,000 hours under 24/7 operation.

2. Oil-in-Water Fluorescence Detection Systems

Application Requirement: Use 254nm UV light to excite aromatic hydrocarbons (e.g., PAH) in water and detect fluorescence signals for pollution monitoring.Filter Configuration:

  • Excitation Optical Path:
  • Bandpass filter: Central wavelength 254nm, 30nm bandwidth, peak transmittance >25%, with cut-off bands 200-1100nm (OD >2).
  • Substrate & Coating: Fused quartz substrate with hard coatings resistant to oil contamination in water.
  • Fluorescence Signal Acquisition:
  • Long-pass filter: Cut-off wavelength 280nm, transmitting 280-380nm to capture fluorescence signals with photodetectors (e.g., PIN photodiodes).
  • Dichroic mirror: Reflects excitation light at 254nm and transmits fluorescence signals to reduce optical path interference.
  • Anti-Interference Design:
  • Antireflective coating on the rear surface to minimize reflection ghosting and improve signal-to-noise ratio.
  • Large-aperture optical design (>10mm) to reduce light flux attenuation caused by suspended solids in water samples.

Selection Rationale:

  • Excitation Efficiency Optimization: The 254nm narrow-bandpass filter matches the emission spectrum of UV LED light sources (e.g., 254nm UV LEDs), maximizing excitation energy.
  • Signal Purity: The long-pass filter blocks residual excitation light (254nm), and the dichroic mirror separates optical paths, reducing background noise in fluorescence signals to <0.05μW/cm².
  • Environmental Adaptability: Fused quartz substrate resists acid/alkali corrosion, and hard coatings prevent oil adhesion, making it suitable for long-term submerged monitoring (e.g., industrial wastewater treatment).

3. Key Parameter Comparison & Selection Logic

Core Parameter Comparison:

  • Central Wavelength
  • Sterilization: 254nm ±5nm
  • Fluorescence Detection: 254nm (excitation) + 280-380nm (emission)
  • Bandwidth
  • Sterilization: Narrow band (FWHM ±5nm)
  • Fluorescence Detection: Narrow excitation band (30nm) + broad emission band (100nm)
  • Substrate Material
  • Sterilization: JGS1-grade quartz
  • Fluorescence Detection: Fused quartz
  • Coating Technology
  • Sterilization: Multilayer dielectric coatings + TiO₂ photocatalytic layer
  • Fluorescence Detection: Hard coatings + antireflective coatings
  • Cut-off Depth
  • Sterilization: OD >6 (200-240nm)
  • Fluorescence Detection: OD >2 (200-280nm)

Selection Logic:

  1. Sterilization Scenarios: Prioritize spectral purity and energy density. Narrow-bandpass and high-transmittance designs enable rapid sterilization while strict stray light control ensures safety.
  2. Detection Scenarios: Balance excitation efficiency and signal purity. Combine narrow excitation bands with broad emission bands to enhance SNR, using dichroic mirrors for optical path optimization.

Considerations:

  • In high-temperature environments (>60℃), choose synthetic quartz substrates (heat resistance >300℃) to prevent coating delamination.
  • In high-humidity environments, add moisture-resistant coatings (e.g., SiO₂ protective layers) to avoid transmittance degradation due to film oxidation.

This configuration ensures system performance while significantly reducing maintenance costs (e.g., extending sterilization filter replacement cycles from 3 months to 1 year), meeting reliability requirements for industrial applications.

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