AIEgens Functionalized Materials For The Highly Sensitive Detection Of Mercury Ions And Aflatoxin B₁

Rapid detection of hazardous substances in foods is critical for preventing foodborne diseases and ensuring food safety.Fluorescence sensing detection methods have the advantages of high sensitivity,rapid signal response,and good selectivity over traditional detection methods.Because of their high aggregation fluorescence efficiency and ease of modification,the aggregation-induced emission luminescences（AIEgens）materials have been widely used in sensing detection,biological imaging,biomedicine,and public security.AIEgen’s advantages,particularly its low background fluorescence,large Stokes shift,and good optical stability,make it widely used in the detection of agricultural and veterinary drug residues and heavy metal ions.In this study,TPE-RB-functionalized hydrogel（TR-FC hydrogel）and Au-AIE nanoparticles（Au-AIENPs）were prepared by utilizing their excellent photophysical properties of AIE materials.Firstly,the agarose hydrogel with rich hydrogen bonds and crosslinked network structure was used to promote the mass transfer rate between the hydrogel and the hydrophilic target in the surrounding environment,thereby enhancing the reaction efficiency between AIEgens and target substances.Additionally,the confined crosslinked network of hydrogel also provides physical support for AIEgens to resist the interferences from environmental factors.Secondly,the Au-AIE bifunctional material with“Janus”structure was prepared by a microemulsion method,in which the oleylamine-coated gold nanoparticles（OA-Au NPs）and AIEgens were located in different spaces of the microsphere because of the phage separation reaction.Therefore,the effects of Au NPs on the fluorescent signal of AIEgens can be effectively eliminated.Then,the Au-AIENPs with excellent fluorescence and colorimetric performance were suggested as the dual-signal probe to establish the lateral-flow immunochromatographic assay method（LFIA）,and the developed LFIA can flexibly choose the interpretation mode according to different application scenarios,and the results obtained from two interpretation modes can be verified each other,and thereby effectively improving the accuracy of LFIA method.Firstly,the TR-FC hydrogel probe was prepared using AIEgens（TPE-RB）combined with agarose hydrosol,and a rapid and sensitive method for detecting Hg²⁺in environmental water was developed.The fiber structure in the hydrogel is not only used as a fixed network to promote the aggregation induced luminescence of AIE,but also used to construct an internal hydrophilic space for enhancing the diffusion of water-soluble pollutants into the hydrogel,and resulting in the improvement of reaction efficiency between the AIEgens and the analytes.Under the optimal conditions,the developed method shows a good linearity with the Hg²⁺concentration ranging from 0.195μM to 12.5μM,which can be represented by a regression equation of y=0.9484 ln（x）+2.3237（R²=0.9918）.The limit of detection（LOD）of the proposed method is 0.152μM,which is 4-fold higher than that of the method by using the AIEgens as the fluorescence probes.Furthermore,the proposed TR-FC hydrogel shows no cross reaction with other common metal ions in water,indicating the high specificity to Hg²⁺.The average recoveries of proposed method for Hg²⁺determination in sewage is 82.54%～109.59%,with the coefficient of variation（CV）ranging from 2.51%to 12.17%,indicating an acceptable accuracy and precision.Secondly,A plasma-fluorescent bifunctional Au-AIENPs with“Janus”structure was prepare via co-assembling OA-Au NPs and AIEgens（TPETPAFN）in the PMAO polymer matrix by a microemulsion method,in which the AIEgens was preferentially aggregated to form the fluorescent core,while the PMAO polymer was formed the shell,and the OA-Au NPs distributed in PMAO matrix to form a semi-crescent shape.In the Au-AIENPs,the OA-Au NPs and AIEgens components have a good spatial separation state,and thereby effectively reducing the mutual interference between the colorimetric and fluorescent signals.The as-prepared Au-AIENPs.was used as the difunctional probes to construct the Au-AIENPs-RFLFIA.The developed Au-AIENPs-RFLFIA can be used for the AFB₁qualitative detection by the naked eye,and for the AFB₁quantitative detection by the fluorescence reader.The visual limit of detection（v LOD）of Au-AIENPs-RFLFIA was achieved at 0.02 ng/m L.The dynamic linearity of this method for AFB₁quantitative analysis in corn samples was in a range of 0.01 ng/m L to 5 ng/m L,which can be presented by a four-parameter fitting equation of y=3.55-3.32/（1+（x/2.09）^0.83）（R²=0.9967）.The quantitative limit of detection（q LOD）was calculated as low as 0.0076 ng/m L.Furthermore,the detection performances of Au-AIENPs-RFLFIA was compared with those of traditional competitive colorimetric-fluorescence strip by using Au-AIENPs as probes（Au-AIENPs-CFLFIA）,and also compared with the ratio fluorescence strip by using the AIENPs as the probes（AIENPs-RFLFIA）.Compared with the colorimetric Au-AIENPs-CFLFIA,the Au-AIENPs-RFLFIA shows an obvious color change in fluorescence from red-orange to-green on the T-line with the AFB₁concentration increasing,and the v LOD value is 62-fold lower than that of Au-AIENPs-CFLFIA.Compared with AIENPs-RFLFIA,the q LOD value of Au-AIENPs-RFLFIA is 1.92times lower than that of AIENPs-RFLFIA,while the dynamic linear range is 2 time wider than that of AIENPs-RFLFIA.In addition,the proposed Au-AIENPs-RFLFIA shows a high specificity for the AFB₁determination with a negligible cross reaction to other four common mycotoxins.The average recoveries for the AFB₁spiked corn samples were in a range of 95.72%to 102.2%with the CV ranging from 8.75%to12.56%,indicating that Au-AIENPs-RFLFIA had an accepted accuracy and precision for the AFB₁quantitative determination in real corn samples.