| Fluorescence-based analytical method has attracted widespread attention due to the accessibility of various fluorescent materials with simple synthesis process,low cost,quick response and excellent sensitivity.In recent years,the fluorescent paper sensor based on ratiometric fluorescence achieves rapid and visual detection.However,it still relies on the assistance of additional hand-held UV light and dark background environment and is often limited to semi-quantitative detection,which seriously restricts the real-time,precise and on-site detection especially in resource-constrained fields.Thus,in view of the aforementioned issues,the study achieves sensitive,convenient,reliable and visual detection of pesticide residue and biomolecules using an integrated smartphone sensing platform based on the combination of ratiometric fluorescent test paper and the smartphone device.The platform provides an efficient sensing strategy in the aspects of food and medicine supervision,environment monitoring and human health diagnostics.The main contents of the study are presented as follows:(1)A smartphone sensing platform based on ratiometric fluorescent test paper has been constructed for visual and real-time/on-site detection of thiram residue.The amino-functioned carbon dots(CDs)were covalently linked to the outer surface of silica(SiO2)nanoparticles which were embedded with red CdTe quantum dots to construct ratiometric fluorescence probe.The addition of gold nanoparticles(Au NPs)renders the quenching of blue fluorescence.After introducing thiram,the blue fluorescence was recovered gradually due to the quick aggregation of Au NPs which ascribed to the cleavage of S-S bond of thiram molecule and the strong and quick interaction of Au-S,and the FRET effect was blocked and the blue fluorescence was restored.It achieved the fluorescence "on-off-on" strategy to detection of pesticide thiram.The fluorescent paper strip was prepared based on the ratiometric probe solution and combined with smartphone device to construct sensing platform for visual and real-time detection of thiram.The fluorescence exhibited a wide color variation from pink to purple to blue with increasing thiram concentration.A Color Recognizer APP installed in the smartphone could out-put the corresponding RGB values,and the R/B values exhibited a linear relationship with concentration of thiram and could be used for reliable detection of thiram with a low detection of limit of 59 nM.At the same time,the sensing platform was applied for real samples detection and testified the practicality of the platform.(2)We utilized the smartphone sensing platform based on the fluorescent test paper for accomplishing real-time/on-site and visual sensing of glutathione(GSH).We adopted blue fluorescent CDs and orange fluorescent gold nanoclusters(AuNCs)to fabricate ratiometric probe for detection of GSH.For the system,blue CDs acted as internal reference and orange Au NCs acted as responsive unit.Under the existence of Cu2+,the orange fluorescence decreased due to Cu2+-triggered aggregation-induced fluorescence quenching through chelation effect of Cu2+and Au NCs.After adding GSH,the fluorescence was enhanced gradually owing to the much strong coordination between Cu2+and GSH,and Cu2+were easily taken away from the surface of Au NCs.The sensing procedure accomplished visual detection with fluorescence change from orange to blue to orange and a sensitive detection of limit of 0.19 ?M.Adopting the portable smartphone sensing platform based on fluorescent test paper achieved real-time,visual and reliable determination of GSH.To demonstrate the flexibility of the sensing platform,the human serum was chosen to detect the level of GSH.The final results suggest the sensing platform can be able to detect the GSH in normal and aberrant level,thus monitor the human health and accomplish human health prognosis.Most significantly,the constructed platform could play an important role in on-site/on-line and accurate detection and medical diagnostics. |
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