Combined “Dual” Absorption and Fluorescence Smartphone Spectrometers

Abstract

A dual absorption and fluorescence smartphone spectrometer is demonstrated. The optical sources are the white flash LED, a blue LED λ = 450 nm and a UV LED at 370 nm, the latter two placed at 90º. Detection was carried out with the camera CMOS chip. By integrating the blue and UV excitation sources into the white LED circuitry, the entire system is self-contained and powered from the smartphone battery; the design can be scaled to add further excitation sources. The dispersive element is a low cost, nano-imprinted diffraction grating coated with Au, which is placed in a 3D printed case. Using a customized Android App, measurements of both absorption and fluorescence spectra are demonstrated using pH and Zn2+-sensitive fluorescence chemosensor probes. The spectral resolution obtained is of 1.3 nm.