A smartphone-based ratiometric fluorescence and absorbance dual-mode device for Rhodamine B determination in combination with differential molecularly imprinting strategy and primary inner filter effect correction

Multi-signal assays offer the advantage to improve the accuracy and diversity by integrating the merits of each output. In the widely used colorimetric and fluorometric dual-mode, the fluorescent intensity and absorbance signals are usually measured by a lab spectrofluorometer and a spectrophotometer. Herein, a smartphone-based device which is able to measure simultaneously the ratiometric fluorescence and absorbance signals was designed. Its analytical performance is demonstrated by the determination of Rhodamine B (Rh B). In a three-channel cuvette, the detection cell (with test solution) was sandwiched between two light intensity measurement cells (with Rh B standard solution). Under the irradiation of the excitation light of 550 nm, the fluorescent images of the three cells were captured by the camera in a smartphone. The ratiometric fluorescence at 590 nm and the absorbance at 550 nm are obtained according to the brightness ratio of the middle cell and the third cell to the first one, respectively. The dual-mode of fluorescence and absorbance can widen the detection range, with the limit of detection for Rh B of 3.2 nM in ratiometric fluorescence mode and 0.38 μM in absorbance outputs, respectively. Importantly, the possible inner filter effect at the excitation wavelength of the fluorescence can be corrected according to the absorbance signal, improving the accuracy of determination. The dual-mode portable device was used to determine Rh B in combination with differential molecularly imprinting strategy to improve further the anti-interference ability.