The Designs And Application Of Smartphone-based Portable Colormetric Devices And Methods

Recently,with the rapid development in microelectronics and optics technology,smartphones have been integrated with high-resolution cameras,high-speed processors and various sensors,offering the ability in high-definition image acquisition and high-speed data analysis and processing.Smartphone-based portable analytical devices and methods are helpful to achieve the goal of fast and accurate on-site detection.In this thesis,we improve the analytical performance of smartphone-based colormetric detection devices and methods,especially in the sensitivity and reliability.The main contents are outlined as follows.1.Portable long optical path absorbance device and method based on ratiometric fluorescence measurementChlorine is the most common chemical compound used for treatment of water,but the concentration of free chlorine must be strictly controlled.For fast and on-site detection of free chlorine,cost-effective and miniaturized devices are required.Herein,we reported a smartphone-based colorimetric device with improved sensitivity and reliability,equipped an absorbance(total optical path 20 cm)and a fluorescence cuvettes.The reaction mixture of free chlorine and 3,3’,5,5’-tetramethylbenzidine(p H=1.8)were added in the absorbance cuvette and methionine stabilized Au nanoclusters(Met-Au NCs)solution was added in the fluorescence cuvette.A 450 nm laser beam was passed through the fluorescence and absorbance cuvettes and reflected back by a triangular mirror at the end of absorbance cuvette.The fluorescence images of Met-Au NCss solution in the reference and measuring areas were captured by the camera in a smartphone.The absorbance was obtained by using a ratiometric fluorescent strategy,which is found to be independent of the variations in light source intensity,concentration of fluorescent luminophore,and exposure parameters of the camera.The absorbance measured in the proposed device obeys Lambert-Beer law in the range of 0~1.The triangular mirror is useful to double the absorption optical path and reduce the distance between the reference and measuring fluorescence areas.The sensitivity in long-path colorimetric device was one order of magnitude higher than that in spectrophotometer using 1 cm cuvette.This simple colorimetric device offers the advantages of portability,sensitivity and reliability for field analysis.2.Correction of the influence of asymmetric imaging of colorimetric cell array in high-throughput portable absorbance device by dual wavelength approachIn this chapter,we developed a smartphone based high-throughput portable absorbance device.When a group of micro cells are integrated to a colormetric array,the angle of each micro cell to the camera lens is not the same,which will cause a large measurement error.To overcome this shortcoming,the visual field of the camera is expanded by using a wide-angle lens.On the other hand,the influence of the asymmetric imaging of colorimetric cell array in the high-throughput portable absorbance device was corrected by dual wavelength approach.The precision and accuracy of the absorbance measurements are much improved.In order to avoid the crosstalk of the light source,the black microporous plate is used as the colormetric array to realize the uniform and isolated illumination distribution for each micro cell.The proposed smartphone dual wavelength colorimetric device can detect 40 samples at the same time,offering the advantage of high-throughput.The feasibility of this method in different wavelength regions was tested by using iodometry,starch and Mn(III)-EDTA methods for dissolved oxygen determination in water samples.3.Correction the influence of light source intensity attenuation on portable colorimetric device on absorbance measurement by an internal reference methodVisual colorimetry is a cost-effective method in field analysisr.To reduce the errors from estimating the hue by naked eyes and to enhance the sensitivity,we propose a smartphone-based portable colorimetric device with long-path and self-calibration ability.The key idea relies on a flow colorimetric tube with the illumination in empty tube or at a low absorption wavelength as the internal references to correct the baseline drift due to light source intensity decay.The self-focusing ability in the round-bottom colorimetric tube is helpful to simplify the design of the portable device.The absorbance measured by proposed device obeyes the Lambert-Beer law in the range of 0~1.By using N,N-diethyl-pphenylenediamine as the colorimetric regent,the proposed method demonstrates a promising result for the determination of free chlorine with the linear range of 0.8–14 mM and the limit of detection of 0.23 m M.This simple colorimetric device offers the advantages of cost effectiveness,ease of implementation,portability,sensitivity and reliability for field analysis.