A portable fluorescence detection device based on a smartphone employing carbon nanodots for Mn2+ sensing

Abstract

The measurement of fluorescence emission for quantitative analysis is typically based on a traditional spectrofluorometer, which limits an onsite detection approach. Thus, an alternative device should be developed for fulfilling this analysis outside of the laboratory. Therefore, a low-cost, portable, and low-energy consumption fluorescence reader-based smartphone device was developed. An ultraviolet light-emitting diodes (UV-LED) was used to construct the fluorescence device-based smartphone as a low-power excitation light source. The smartphone camera was used as a detector for detecting photons from the fluorescence emission process of the fluorescence probe and was connected to a digital image platform. Transparent acrylic with orange and yellow colors was employed as a filter for reducing the interference from light source intensity. The obtained digital image was converted to red, green and blue (RGB) intensity using a custom-designed smartphone application. N,S-doped carbon nanodots (N,S-CDs) were demonstrated to be a good fluorescence indicator for determining trace quantities of Mn²⁺ in cosmetics. The approach exhibited high selectivity and sensitivity, detecting and quantifying analytes at 1–5 μM concentrations. Furthermore, the method's detection limit of 0.5 μM reflects its capacity to detect trace amounts of a target analyte. Mn²⁺ in cosmetic products was successfully analyzed using this device with high accuracy comparable with the results from inductively coupled plasma-optical emission spectroscopy (ICP-OES).