Dynamic Irradiation-responsive Germanate Materials For Anti-counterfeiting In Bright And Dark Fields

With the increasing number of counterfeit and shoddy products,trademark anti-counterfeiting technology is constantly facing novel and severe challenges.Advanced anti-counterfeiting technology can not only reduce economic losses for enterprises,but also protect the interests of consumers.Generally,luminescent anti-counterfeiting technology has been widely reported by researchers in the field of trademark anti-counterfeiting due to the advantages of visualization of luminescent parameters(luminescent color and luminous intensity,etc.).However,common luminescence parameters do not change under simple stimulation(ultraviolet lamp irradiation),so they are easily imitated and forged by criminals.In addition,traditional luminescent anti-counterfeiting materials only show optical features in a dark field environment(dark/invisible).This specific use environment will limit the convenience of reading anti-counterfeiting features,further affecting the application of trademark optical anti-counterfeiting.Therefore,in this work,we developed a germanate based material,which exhibits unique dynamic photoluminescence and dynamic color change properties under continuous irradiation.Based on the above material characteristics,a kind of dynamic anti-counterfeiting film device is further prepared,which can be applied in dark and bright fields at the same time.It shows good practical application value in the field of trademark anti-counterfeiting.The research on the matrix in the luminescent powder is very important.The single-phase CaZnGe₂O₆ matrix is synthesized by the high-temperature solid-phase method,and its good bandwidth provides the conditions for doping ions.Most transition metal ions have broad emission bands and inherent electron spin laws.It is especially found that solid solutions with dynamic irradiation-responsive properties are found after doping Mn²⁺and Pb²⁺in the CaZnGe₂O₆ matrix.Further in the dark field environment,with the increase of the UV lamp irradiation time,the luminescence color of the Mn²⁺doped samples will dynamically change from green to red,and it is interesting that the photoluminescence color of the Pb²⁺doped samples will dynamically change from red.turns lavender.Compared with the traditional static luminescence phenomenon,these two materials achieve the purpose of changing the photoluminescence color in the time dimension in the dark field environment in the same matrix,which provides the base for the subsequent trademark dynamic optical anti-counterfeiting application.Moreover,based on the dynamic photoluminescence performance in the dark field,it was also found that the body color(powder color)of the samples doped with Pb²⁺also changed dynamically from white to yellow in the bright field(daytime/visible).Based on the unique dynamic irradiation-responsive characteristics,the powder was mixed with PDMS,and the luminescent anti-counterfeiting device"Lanzhou Three Forts"was prepared by screen printing.When continuously stimulated by UV light,its anti-counterfeiting characteristics will change dynamically,which significantly improves the anti-counterfeiting level of the trademark.