Magetic-Optical Nano Iron-Based Core-Shell Structured Photoelectrochemical Sensing With High Performance

Photoelectrochemical?PEC?sensor is a novel quantitative analysis method,which has become one of the leading research fields in analytical chemistry.It has good performance in fast,simple,sensitive,wide linear range of detection.In recent years,the research progress of photoelectrochemical sensors mainly focuses on the various photoelectric sensitizing strategies,thus continuously improving the sensitivity.However,the selectivity and stability still need to be further improved for the complex real samples.In this project,therefore,superparamagnetic Fe₃O₄,Fe₃O₄@SiO₂,Fe₃O₄@SiO₂@TiO₂ and precious metal silver nanoparticles combined with aptamer and antibody were prepared for the construction of PEC sensing with good performance for silver ions,progesterone and matrix metalloprotease-2 in complex samples.The main tasks are as follows:?1?The current silver ions sensors are typically focused on the C-Ag⁺-C complex structure resulted from specific interaction between silver ions and cytosine?C?,which has the features of high cost and complexity of electrode modification.Consequently,cytosine-rich oligonucleotide-free sensors will arouse intense research interests for an alternative strategy.Herein,yolk-shell structured Fe₃O₄@void@TiO₂was applied to constructing oligonucleotide-free PEC sensing for silver ions based on Ag⁺-Na⁺exchange after the base etching of silica interlayer.The captured silver ions in Fe₃O₄@void@TiO₂ can be in situ reduced by ethanol washing.The more silver ions captured,the more silver nanoparticles generated.By the light irradiation,the hot electrons from plasmonic silver nanoparticles can be injected into conduction band of TiO₂ and remarkably enhance the photocurrent response in a proportional manner.Superparamagnetic Fe₃O₄@void@TiO₂ can effectively separate the target from complex matrix,and then carry out the silver ions determination in pure buffer solution.Finally,the as-designed PEC sensor has been successfully utilized to monitor silver ions in serum samples.Additionally,it has good performance in easy operation,portability,sensitivity,selectivity,and short time consuming.?2?Selectivity is a crucial parameter for PEC sensing,in complex system,despite the use of specific probes such as aptamers,antibodies,and enzymes,the coexisted interferences can still result in the inaccuracy of PEC sensing.Herein,we utilized to bifunctional magnetic-optical beacon of Fe₃O₄@SiO₂@TiO₂,and modification of aptamer and capture DNA on the surface of the amino-functionalized Fe₃O₄@SiO₂@TiO₂,progesterone was captured in a liquid milk sample by Fe₃O₄@SiO₂@TiO₂-NH₂-aptamer-cDNA.Afterwards,we by an external magnetic field to separated and washed,and the diluted suspension was orderly assembled on the surface of ITO electrodes.Under the optimized condition,based on Fe₃O₄@SiO₂@TiO₂-NH₂-aptamer-cDNA modified electrode,the photocurrent decreased proportionally with the increase of progesterone concentration.It indicated that the PEC sensor can be successfully utilized to monitor progesterone in liquid milk samples.The well-designed PEC sensor exhibited a low detection limit of 0.3pM and a wide linear range from 1⁶000 pM for target progesterone detection.In addition to the excellent selectivity,the as-designed PEC senor has good performance in sensitivity,cost-effectiveness,easy to fabrication,and reproducibility.?3?Matrix metalloproteinases-2?MMP-2?is looked as an important biomarker and target for early cancer predication and medication,respectively.Accordingly,sensitive detection of MMP-2 expression levels is of great importance to early diagnosis and therapy of the cancers.Herein,a novel PEC sandwich immunoassay for MMP-2?antigen,Ag?has been developed based on superparamagnetic Fe₃O₄@SiO₂-Ab₁ and TiO₂-Ag NPs coated with HRP-conjugated goat anti-rabbit IgG?Ab₂??TiO₂-Ag NPs-Ab₂?.Superparamagnetic Fe₃O₄@SiO₂-Ab₁ can effectively separate targets from complex real samples with external magnetic field,and remarkably improve the selsectivity therefore.TiO₂-Ag NPs-Ab₂ works as PEC signal amplification indication because the in situ plasmonic Ag NPs confined in titanium dioxide can significantly increase the photocurrent.Specifically,the hot electrons from Ag NPs can inject into the conduction band of amorphous TiO₂ and consequently enhance the photocurrent conversion efficiency compared to that of single amorphous TiO₂.The amount of target Ag affects the change of photoelectric signal from the sandwich structured Fe₃O₄@SiO₂-Ab₁-Ag-Ab₂-TiO₂-Ag NPs?FSAAATA?in a proportional manner.Under the optimized condition,the as-designed PEC immunoassay sensor exhibited a wide dynamic linear range from 1fg mL^-1 to 100 pg mL^-1 with a low detection limit of 0.34 fg mL^-1.In addition to the ultrasensitivity,it has good performance in selectivity,stability,reproducibility and cost-effectiveness.