nanoDot^TM Taggant System

Voxtel’s uniquely designed and engineered taggant system is ideal for use in security applications, covert operations, anti-counterfeiting systems, and encryption technologies. The core of the technology is based on a nanoengineered material that takes advantage of having high absorptivity in either the ultraviolet (200 - 400 nm) or the near infrared spectral regimes (700 - 1600 nm) both areas that are ‘invisible’ to human sight. Absorption of light in these spectral regimes, followed by an efficient energy transfer to specially designed luminophores located within the nanocrystalline material - enables these taggants to give an emissive signature at a number of different wavelengths - both in the visible (400 - 700 nm) and in the near infrared regimes (700 - 1600 nm).

These taggants are highly customizable and can be adapted to many applications. As shown in the above image, these nanomaterials consist of three layers:

• an inner core which consists of a material used to strongly absorb ultraviolet light and an emissive material used to down-convert the ultraviolet light to either visible light or near infrared light.
• an inner shell used to ‘protect’ the inner core from environmental effects such as humidty, smog and other interactions with compounds in the given environment. This is important in order to maintain the high degree of emissive control within the nanoparticle.
• an outer shell used to promote the desired physical properties of the nanomaterial.

Based on this nanostructural design, the properties of the nanomaterial and taggant system can be tailored in the following ways:

 

Absorption Tuning
Although intended mostly for use in the down conversion of ultraviolet light to either visible or near infrared light - these materials may also absorb infrared light and undergo an upconversion process to produce visible light. Absorption tuning is then controlled to allow (more combinations are possible, please inquire for more details):

• UV-A absorption
• UV-B and UV-A absorption
• UV-C, UV-B and UV-A absorption
• NIR absorption (monochromatic)

Emission Tuning
A number of different emissive wavelengths are available, both in the visible and in the near infrared spectral regimes. In addition to the use of a single taggant material, mixtures of taggants may be used to provide a unique, spectral signature which allows for > 10⁶ (1,000,000) possible combinations per pixel of encryption.

Physical Properties
The physical properties of the taggant material can be customized for your application. A few of parameters that may be customized include:

• adhesion
• solubility (hydrophilic, hydrophobic, amphiphilic)
• matrix compatibility (thin film processing in a polymeric film for instance)
• substrate compatibility (changing the wetting characteristics when deposited on a given substrate)

Additionally, customization of these physical properties also allows the capability of incorporating features that allow deposition of this material through many different formats: paints, aerosols, drop-on-demand applications such as inkjet, electrophotography (dry and liquid), traditional offset press inks, etc.

As a system, other features that may be included in ‘customizing’ for your application and needs include:

customizing for wavelength(s) of activation of taggants

• this feature allows for the promotion of a ‘gated’ security system. Use of taggants that are activated by different wavelengths permits use of a ‘field’ activation for initial testing, and for use of additional activation of all components for ‘forensic’ analysis.
• This same feature may also be used for different levels of encryption methodologies
• monochromatic ultraviolet excitation
• panchromatic (polychromatic) excitation
• monochromatic near infrared excitation (laser - for upconversion processes)

customizing for wavelength(s) of detection (emission by taggants)

• this feature allows for the promotion of a ‘gated’ security system as well - by choosing which wavelengths to monitor, different messages may be read
• single wavelength detection
• multiple wavelength detection
• relative concentration of signal detection

Finally, this taggant system may be used for different types of encyprion practices:

• gated security (message available to be read dependent upon security clearance of intended target)
• spatial resolution (use of standard encryption technologies / bar code technologies)
• spectral resolution (activation, emission and concentration dependence of the taggant)