Counterfeiting
and inverse engineering of security and confidential
documents, such as banknotes, passports, national cards, certificates,
and valuable products, has significantly been increased, which is
a major challenge for governments, companies, and customers. From
recent global reports published in 2017, the counterfeiting market
was evaluated to be $107.26 billion in 2016 and forecasted to reach
$206.57 billion by 2021 at a compound annual growth rate of 14.0%.
Development of anticounterfeiting and authentication technologies
with multilevel securities is a powerful solution to overcome this
challenge. Stimuli-chromic (photochromic, hydrochromic, and thermochromic)
and photoluminescent (fluorescent and phosphorescent) compounds are
the most significant and applicable materials for development of complex
anticounterfeiting inks with a high-security level and fast authentication.
Highly efficient anticounterfeiting and authentication technologies
have been developed to reach high security and efficiency. Applicable
materials for anticounterfeiting applications are generally based
on photochromic and photoluminescent compounds, for which hydrochromic
and thermochromic materials have extensively been used in recent decades.
A wide range of materials, such as organic and inorganic metal complexes,
polymer nanoparticles, quantum dots, polymer dots, carbon dots, upconverting
nanoparticles, and supramolecular structures, could display all of
these phenomena depending on their physical and chemical characteristics.
The polymeric anticounterfeiting inks have recently received significant
attention because of their high stability for printing on confidential
documents. In addition, the printing technologies including hand-writing,
stamping, inkjet printing, screen printing, and anticounterfeiting
labels are discussed for introduction of the most efficient methods
for application of different anticounterfeiting inks. This review
would help scientists to design and develop the most applicable encryption,
authentication, and anticounterfeiting technologies with high security,
fast detection, and potential applications in security marking and
information encryption on various substrates.
