Journal
NANOTECHNOLOGY
Volume 20, Issue 18, Pages -Publisher
IOP Publishing Ltd
DOI: 10.1088/0957-4484/20/18/185301
Keywords
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Funding
- Air Force Office of Scientific Research [FA95500610398]
- National science Foundation [DMR0702372]
- Division Of Materials Research
- Direct For Mathematical & Physical Scien [0702372] Funding Source: National Science Foundation
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We report a method for fabricating predefined photopatterns of upconversion nanophosphors using a chemical amplification reaction for direct writing of films with multilayer color-coded patterning for security applications. To photopattern the nanocrystal film we have synthesized rare-earth ion (Er3+/Yb3+ or Tm3+/Yb3+) co-doped sodium yttrium fluoride (alpha-NaYF4) nanophosphors and functionalized the nanocrystal surfaces by incorporation of a photopatternable ligand such as t-butoxycarbonyl (t-BOC). The surface modification allows photopatterning of the nanophosphor solid state film. Furthermore, upconversion nanophosphors show a nearly quadratic dependence of the upconversion photoluminescence (PL) intensity on the excitation light power, and tailoring of the PL wavelength is possible by changing the lanthanide ions. We have demonstrated the capability of anchoring nanophosphors at desirable locations by a photolithography technique. The photopatterned films exhibit fixed nanophosphor structures clearly identifiable by strong upconversion photoluminescence under IR illumination which is useful for a number of applications in security.
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