White-light flashlight activated up-conversion luminescence for ultraviolet-B tagging
Aiying Wang, Yichun Liu, Xiaojun Wang, Feng Liu
Abstract
Optical tagging technology with emission in the ultraviolet region upon visible-light excitation is promising for objects identified in visually bright environments, while the relevant research is absent. Here we put forward a covert tagging concept, which is based on up-converting phosphors (e.g., <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:msub> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mi mathvariant="normal">L</mml:mi> <mml:mi mathvariant="normal">u</mml:mi> </mml:mrow> <mml:mn>3</mml:mn> </mml:msub> </mml:mrow> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:msub> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mi mathvariant="normal">A</mml:mi> <mml:mi mathvariant="normal">l</mml:mi> </mml:mrow> <mml:mn>5</mml:mn> </mml:msub> </mml:mrow> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:msub> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mi mathvariant="normal">O</mml:mi> </mml:mrow> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mn>12</mml:mn> </mml:mrow> </mml:msub> </mml:mrow> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mo>:</mml:mo> </mml:mrow> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:msup> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mi mathvariant="normal">P</mml:mi> <mml:mi mathvariant="normal">r</mml:mi> </mml:mrow> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mn>3</mml:mn> <mml:mo>+</mml:mo> </mml:mrow> </mml:msup> </mml:mrow> </mml:math> ) with emission peaking in the ultraviolet-B region (UV-B, 290−320 nm). A white-light flashlight serves as excitation source to make the up-converter emit, and an ultraviolet camera is applied to see such an emission wavelength range. This Letter expands the excitation source for an up-conversion process to a convenient flashlight for the first time, to the best of our knowledge. Moreover, such a flashlight-pumped UV-B tagging technology is generally applicable for many other phosphors, which can be utilized to mark and differentiate objects in commercial, civilian, or military applications.