Excitation and Emission Wavelengths of UV Fluorescent Pigments: A Technical Guide to 365 nm and 254 nm Series Selection
Nichwell is a professional manufacturer of UV fluorescent pigments and thermochromic pigments, supplying specialty colorant solutions to security printing, coatings, and plastics customers across more than 30 countries.
1. What Are Excitation and Emission Wavelengths?
UV fluorescent pigments work by absorbing ultraviolet light at a specific wavelength (the excitation wavelength) and re-emitting that energy as visible light at a longer wavelength (the emission wavelength). This process is known as photoluminescence.
Two parameters define the optical behavior of every UV fluorescent pigment:
Excitation Wavelength
This is the wavelength at which the pigment absorbs ultraviolet energy most efficiently. The pigment must be exposed to UV light at or near this point to produce strong, reliable fluorescence. Industrial UV fluorescent pigments are typically designed for excitation at:
- 365 nm (Long-wave ultraviolet / UV-A)
- 254 nm (Short-wave ultraviolet / UV-C)
Emission Wavelength
This is the wavelength of visible light emitted by the pigment after excitation. It determines the glowing color observed by the human eye or machine sensor. Typical emission peaks include Blue (440 nm), Green (494 nm), Yellow-green (530 nm), and Red (610 nm).
The exact combination of excitation and emission wavelengths determines whether a pigment is suitable for a specific authentication system and security requirement.
Daylight
Under 365nm UV Light
2. Why Wavelength Matching is Critical
Matching the excitation wavelength of your pigment to your scanning verification system is a fundamental requirement.
If a pigment is exposed to a non-optimal excitation wavelength, it suffers a significant loss of brightness and color purity. In high-security printing, printed features are verified using fixed-wavelength UV equipment. The pigment must perfectly match the light source to ensure consistent, reliable authentication results and avoid false negatives.
3. 365 nm UV Fluorescent Pigment Series
The 365 nm series is the industry standard for most commercial and security applications because 365 nm (UV-A) lamps are widely available and safe to handle.
Organic Series vs. Inorganic Series
- Organic 365 nm Pigments: Engineered for security inks (offset, flexographic, screen-printing). They offer extremely high brightness, vivid color emission, and appear completely off-white or invisible in daylight.
- Inorganic 365 nm Pigments: Designed for applications requiring higher thermal stability and weathering performance, such as plastic masterbatches, architectural coatings, and ceramics.
Available Colors & Specs:
Our 365 nm series covers the full visible spectrum, providing strict emission peaks for Red (610 nm), Green (494 nm), Blue (440 nm), Yellow, Orange, and White. Depending on the grade, particle sizes are highly controlled between 1 to 15 µm.
For a complete list of colors, exact spectral data, and technical specifications, please visit our main UV Fluorescent Pigments Product Page.
4. 254 nm UV Fluorescent Pigment Series
254 nm excitation (UV-C short-wave) is used in high-security authentication. These covert features remain invisible under standard 365 nm long-wave UV lights.
Typical applications include:
- Banknote, identity document, and tax stamp security printing
- Forensic evidence marking and chain-of-custody tracking
Because 254 nm fluorescent features cannot be excited by standard UV lamps, they provide an advanced level of covert security that requires specialized short-wave reading equipment.
Safety Notice: 254 nm UV sources (UV-C) require suitable shielding and eye protection. Operators must follow strict safety regulations when testing these formulations.
5. 365 nm vs 254 nm: Core Comparison
To summarize the differences for your formulation:
- Excitation: 365 nm uses standard UV-A long-wave; 254 nm uses specialized UV-C short-wave.
- Covert Security Level: 365 nm is the standard for packaging and labels; 254 nm offers high-level security (invisible under 365 nm light) for currency and IDs.
- Chemistry: Both series are available in organic and inorganic formulations to suit your specific binder system.
6. How to Select the Right Series for Your Application
Before starting your lab formulations, clarify these parameters to select the correct powder:
- Step 1: What UV wavelength does your verification equipment use?
This is the primary rule. If your process uses standard long-wave UV lamps, select the 365 nm series. If specialized short-wave equipment is used, select the 254 nm series. - Step 2: What are your processing conditions?
Thermal stability varies significantly. For high-temperature processing like plastics extrusion, inorganic grades are generally preferred. However, limits vary by color and exposure time. Share your processing profile with our technical team first. - Step 3: What is your binder and ink system?
Pigment compatibility with binders and solvents must be evaluated in your actual system. Let us know your resin type so we can recommend the best dispersion grade.
7. Quality Control and Technical Support
In security printing, batch-to-batch spectral consistency directly affects the reliability of automated sorting systems. At Nichwell, each production batch is strictly evaluated for emission wavelength, fluorescence brightness, and particle size distribution under our ISO 9001-certified quality management system.
Custom Colors: For high-security applications, custom colors, blends, and targeted emission characteristics are available upon technical evaluation.
Please note: The data presented in this technical guide are typical reference values. Customers should conduct thorough application testing under their specific formulation conditions.
Request a Sample or Technical Consultation
Tell us your required excitation wavelength, binder system, processing temperature, and target emission color. The Nichwell technical team is ready to recommend a suitable grade for your evaluation.