nn9b08326_si_001.pdf (2.5 MB)
Temporal Multilevel Luminescence Anticounterfeiting through Scattering Media
journal contribution
posted on 2020-03-17, 10:29 authored by Meiling Tan, Feng Li, Xing Wang, Rongwei Fan, Guanying ChenOptical anticounterfeiting, typically
using luminescent materials to encode and unveil hidden patterns,
plays an essential role in countering fraud in trademark, document
security, food industry, and public safety. However, this technique
is often realized through color-encoded fashion and in the visible
range, preventing high-order encryption as well as visualization through
scattering layers. Here, we describe a set of shortwave infrared (SWIR)-emitting
lanthanide-doped nanoparticles with precisely controlled luminescence
lifetime, which can be utilized as temporary codes for multilevel
anticounterfeiting through opaque layers. To achieve this, we devise
a core/shell/shell/shell structure of NaYF4:Yb3+/Er3+ @ NaYbF4 @ NaYF4 @ NaYF4:Nd3+, in which the inert NaYF4 shell
acts as an energy-retarding layer to regulate energy flow from the
outmost light-harvesting layer to the inner core domain to produce
long-lived SWIR luminescence at 1532 nm. A precise control of the
NaYF4 layer thickness enables yielding a precisely defined
lifetime tunable between ∼3 and 10 ms, yet without compromising
luminescence intensities. Importantly, optical patterns of these lifetime-encoded
core/multishell nanoparticles are able to dynamically show a multitude
of secured images in the time domain at defined time points through
opaque plastic and biomimetic intralipid layers (about half a centimeter
thick). Our temporal optical multiplexing results, demonstrated here
in multilevel anticounterfeiting, have implications for optical data
storage, biosensing, diagnostics, and nanomedicine.