Desigins And Applications Of Smartphone-based Analytical Devices

With the rapid development in information technology,smartphones which equip have high-speed central processing unit,high megapixel camera and various sensors,large storage space,have powerful data process and exchange ability.Smartphones have became essential tools in communication,photography and mobile payment.Recently,the development of smartphone based detection devices in chemical and biomedical fields has recived remarkable attentions.In this thesis,smartphone-based colorimetric and ratiometric fluorescence detection devices with improving analytical performance are designed for field analysis.The main research contents are outlined below:1.Field analysis Cr（Ⅵ）in water samples by a smartphone-based absorbance device with ultralong absorption pathThe sensitivity of a spectrophotometer is proportional to the length of absorption optical path.But in the portable absorbance detection device,the increase of length of cuvette will result in the loss in its portability.Based on the consideration in both the sensitivity and portability,the absorption optical path is increased via a multiple reflection approach,obtaining a total absorption optical path of 83.5 cm or larger if needed for an absorption cell in similar length as the smartphone.Thus,the sensitivity of a portable absorbance device is much improved.In the proposed device,a laser pointer is used as the light source and the illumination sensor in the smartphone as the light intensity detector.The absorbance measured by the smartphone-based device obeys the Lambert-Beer law in the range of 0～1.1.The intensity of the reflected light in empty colorimetric cell can be serviced as the internal references to correct the possible baseline drift due to light source intensity decay,improving the stability of absorbance.This device was applied to Cr（Ⅵ）determination in water samples on site by using 1,5-diphenylcarbazide as the colorimetric reagent with the linear range of 1～18μg L^-1and the limit of detection of 0.26μg L^-1.This simple absorbance device offers the advantages of cost effectiveness,ease of implementation,portability,sensitivity and reliability for field analysis.2.Visual colorimetry with absorption wavelength in ultraviolet and near-infrared regionsVisual colorimetry is based on the change in color.By replacing naked eyes by the camera in a smartphone as the detector,the accuracy can be much improved.But only the absorbance change in visible region can be detected by the camera in a smartphone due to the limit in cost.In the absorbance system with the absorption wavelength is beyond the visible region,it is difficult to detect the absorbance change by a direct photographic method.To extend visual colorimetry with larger wavelengths region,the absorbance is measured by a ratiometric fluorescence strategy.In a three-channel cuvette,the absorbance cell was sandwiched between two fluorescence detection chambers.The intensities of incident light and transmitted light with respect to the absorbance cell were measured from the fluorescence intensity of the reference and measurement chambers,respectively.The as-measured absorbance from the fluorescence intensity ratio obeys the Lambert-Beer law in the range of 0～1.0.The influence of the variation in the light source intensity on the absorbance was corrected by the ratiometric strategy.The absorption wavelength was extended to the ultraviolet region by using luminophore with excitation wavelength in ultraviolet region while emission wavelength in visible region.By using the up-converted fluorescent materials with excitation wavelength in near-infrared region while emission wavelength in visible region,the absorbance in near-infrared region can be measured.A red carbon quantum dots with broad excitation spectrum is used the fluorescent luminophore,the absorbance at the wavelength of 365 nm（ultraviolet）,505 nm（visible）and 780 nm（near infrared）is measured for the determination of folic acid,dissolved oxygen and hypochlorous acid,respectively.The portable absorbance device was applied for the field analysis of dissolved oxygen in environmental water samples,offering the advantages of portability,reliability and accuracy for field analysis.3.Monitor kinetic process under strong vibration by a portable ratiometric fluorescence deviceSophisticated fluorospectrophotometer and fragile fluorescence cuvette usually require fluorescence intensity to be measure under motionless conditions.For reaction systems under strong mixing conditions,the reaction and measurement stages should be performed in separated places,which is not suitable for kinetic process monitor of rapid reaction.Thanking to the non-contact fluorescence imaging recorded by the camera and the self-correction ability of ratiometric fluorescence,a smartphone-based fluorescence detection device was designed to monitor the reaction kinetics under strong mixing conditions.The hydrolysis of Cs₄Pb Br₆nanocrystals（NCs）was taken as an example to test the analytical performance of the device.In the presence of trace water and vigorous mixing conditions,Cs₄Pb Br₆NCs（non-fluorescence）was converted to CsPbBr₃NCS（strong green fluorescence,emission wavelength 517 nm）.Using anthracene as the reference fluorophore,the brightness ratio of the green（from CsPbBr₃NCs）to blue（from anthracene）components in the fluorescence image which was recorded in situ by the smartphone camera was measured as the signal for kinetic analysis.It was shown that the water-triggered conversion reaction from Cs₄Pb Br₆NCs to CsPbBr₃NCs follows the pseudo-second-order kinetic model in the early rapid hydrolysis stage（up to 4 min）.With increasing water content,the hydrolysis of Cs₄Pb Br₆NCs is promoted to yield more CsPbBr₃NCs,which was used to determine trace water in n-hexane,dichloromethane,and toluene with detection limits of 0.031,0.043,and 0.057μL mL^-1,respectively.