Lycopene, a natural colorant and
antioxidant with a huge growing
market, is highly susceptible to photo/thermal degradation, which
demands real-time sensors. Hence, here a transparent upconversion
nanoparticles (UCNPs) strip having 30 mol % Yb, 0.1 mol % Tm, and
β-NaYF4 UCNPs, which shows an intense
emission at 475 nm, has been developed. This strip has been found
to be sensitive to lycopene with a detection limit as low as 10 nM
using a smartphone camera, which is due to static quenching that is
confirmed by the lifetime study. In comparison to previous paper strips,
here the transparent strip has minimal scattering with maximum sensitivity
in spite of not using any metal quenchers. An increase in strip hydrophobicity
during the fabrication process complements the strip to selectively
permeate and present an extraction-free substitute analysis for chromatography.
Hydrophobicity endows the strip with the capability to reuse the strip
with ∼100% luminescence recovery.