Using a smartphone-based portable spectrofluorimeter, measurement of metal ion concentration in water is reported. A UV LED (λ_ex ~ 370 nm), which is powered by the internal source of the smartphone was implemented to function as the excitation source. The emission peak of the UV LED overlaps well with the absorption peak of the Zn²⁺-responsive molecular probe 6-(1,4,8,11-cyclam-1-yl)ethyl-1,2,3-triazol-4-yl)2-ethyl-naphthalimide fluoro-ionophore (λ_abs ~ 358 nm). The fluorescence emission of this dye at λ_em ~ 458 nm is enhanced upon coordination of Zn²⁺. A customized Android application digitally processes the image from a nano-imprinted polymer diffraction grating and analyses the spectral changes. Zn²⁺ concentration in water samples were measured with a detection limit of δ ~ 5 μM.

Date Published: 1 July 2015
PDF: 4 pages
Proc. SPIE 9655, Fifth Asia-Pacific Optical Sensors Conference, 965511 (1 July 2015); doi: 10.1117/12.2184246

Published in SPIE Proceedings Vol. 9655:
Fifth Asia-Pacific Optical Sensors Conference
Byoungho Lee; Sang-Bae Lee; Yunjiang Rao, Editor(s)