Nanomaterials And Single Atom Catalysts For Sensing Applications

Electrochemiluminescence(ECL)is a light-emitting process triggered by the substance produced via the electrochemical reactions near the electrodes and the most sensitive and selective analytical method that is widely used in environmental monitoring,pharmaceutical study,immunoassay,forensics,food quality testing,and clinical diagnosis.In 1927,the concept of ECL was proposed and comprehensively conducted in 1964 by categorizing ECL into annihilation ECL and co-reactant ECL.The co-reactant-based ECL is a far-reaching reform that brings the ECL phenomenon from academia to real-world applications.As a result,commercial ECL immunoassays have become a popular clinical diagnosis technique and even the gold standard in hospitals all over the world.Most ECL systems so far are designed by using Ru(bpy)32+,luminol,and quantum dots as ECL emitters and TPrA,H2O2,dissolved O2(DO),and S2O82-as co-reactant.H2O2 and DO have been used regularly in the luminol-ECL systems.Such ECL systems suffered from poor selectivity and instability due to H2O2 and ultra-low ECL reaction efficiency due to DO.To improve the ECL sensitivity of the luminol-DO system,new co-reactant accelerators are usually needed.In this dissertation,we mainly focused on boosting the ECL signal of the luminol-DO system via co-reactant accelerators such as single and dual atom catalysts,high entropy oxide(HEO),and 2D ordered plasmonic nanomaterial for signal enhancement and applied for detection of both biological and environmental analytes.The vital points of dissertations are as follow:1.Newly emerging SACs have recently been exploited for luminol-dissolved oxygen ECL;however,they still suffer from low sensitivity and narrow detection range for a real sample assay.In this work,we boost markedly the ECL signal of the Fe-SACs-based system,by the excitation of 2D plasmons derived from the well-packed meta-structure by self-assembly and controlled high-density "hot spot" of the Au@SiO2 nanomembrane.As a proof-of-concept,the developed sensor was applied for the detection of DA,hemin,and Hg2+,under optimum conditions in both pure state and real samples,with pretty low detection limits of 0.1,0.7,and 0.13 nM,wider linear ranges of 0.001-1.0,0.001-10,and 0.01-0.5 nM,and recoveries in the ranges of 97.8-103.4,93.7-105.5,and 97.8-100.6%,respectively.2.In this study,an effective oxygen vacancy(Ov)-involved luminol-dissolved oxygen(O2)ECL(luminol-DO ECL)system was developed and exploited for ECL sensing applications through significant plasmon enhancement of the Ov-involved weak luminol-DO ECL signals by the combined use of Cu-doped TiO2 oxygen vacancy and a Au@SiO2 nanomembrane.The results disclosed that the ECL response of the corresponding system could be synergistically boosted.Furthermore,the developed system has been successfully applied for the highly sensitive detection of alkaline phosphatase with a low limit of detection of 0.005 U/L and an excellent linear range of 0.005 to 10 U/L.3.In this work,we explored the use of high entropy oxide(HEO)comprising five metal ingredients(Ni,Co,Cr,Cu,and Fe),to accelerate the reduction reaction of DO into ROS for boosting the ECL performance of the luminol-DO system.Benefiting from the existing abundant oxygen vacancies induced by the unique crystal structure of the HEO,DO could be efficiently converted into ROS,thus significantly boosting the performance of the corresponding ECL sensor with about～240-fold signal enhancement.As a proof-of-concept,under optimal conditions,the developed sensor was successfully applied for efficient biosensing of dopamine and alkaline phosphatase with a fine linear range from 1 pM to 10 nM and from 0.01 to 100 U/L as well as a low limit of detection of 5.2 pM and 0.008 U/L,respectively.4.Improving the sensitivity of ECL systems is highly desired for in vitro ECL diagnosis and bio-detections due to the often-low content of biomarkers in diseases.In this study,an efficient luminol-DO ECL system was developed through the complexing of Fe,Co dual single-atom catalysts(D-SACs)supported by N-doped graphene with the luminol-capped Ag nanoparticles(AgNPs).Benefiting from the electronic interaction between Fe and Co metal sites in the relevant D-SACs and plasmon enhancement of AgNPs,the performance of the corresponding ECL system could be significantly boosted up to～677-fold under optimal testing conditions,comparable to the classic luminol-O2 system.Furthermore,the developed luminol-DO ECL system was successfully applied for the stable ultrasensitive detection of prostate-specific antigen(PSA)in an extensive linear range,low detection limit,and good stability.5.In the last work,Fe-N5 single-atom catalyst(SAC)supported on graphene was first employed for simultaneous electrochemical detection of DA and UA.Owing to its unique electronic structure and abundant active sites,under optimal conditions,the enzyme-like Fe-N5 SAC constructed electrochemical(bio)sensor exhibits excellent linear typical responses in the range of 0.005-500 and 0.01-480μM,as well as the low limit of detection of 0.007 and 0.027 nM for DA and UA,respectively.More critically,the developed electrochemical system shows promising merits of exceptional stability and good repeatability,and,consequently,it was magnificently applied for the concurrent detection of DA and UA in the samples of human serum.