Sensing Applications Of Functionalized Carbon Nitride Nanomaterials

Graphitic carbon nitride(g-C3N4)materials are graphite-like polymer semiconductors composed of carbon and nitrogen only.Because of their low density,tunable optical band gap and excellent thermal and chemical stability,they have attracted extensive attentions.g-C3N4 nanomaterials not only inherit excellent physical and chemical properties of bulk g-C3N4,but also exhibit distinguished dispersibility in water,great biocompatibility,catalytic properties,optical and electrical properties,and easy to be functionalized.Due to these merits,they have become ones of research hotspot in the fields of biological materials,environmental science,and sensors.In this thesis,several electrochemiluminescence(ECL)sensors were constructed based on the excellent ECL properties of g-C3N4 nanomaterials.Highly sensitive and selective detections of some anions and cations in real samples have been realized,expanding the applications of g-C3N4 nanomaterials in the field of analytical.The thesis is divided into the following four chapters:In chapter 1,literatures related to g-C3N4 nanomaterials,including their properties,preparation methods and applications in the fields of catalysis,sensing,and imaging are reviewed.In addition,the principles and applications of ECL are briefly outlined.At the end of this chapter,the objective as well as the content of the thesis is summarized.In chapter 2,the research on the construction of cyanide sensors based on the phenomenon of ECL recovery induced by etching has been carried out.The graphitic carbon nitride nanosheets(CNNs)have been firstly prepared by ultrasonication-assisted liquid exfoliation,and then functionalized with gold nanoparticles(Au NPs)to form Au-CNN nanohybrids.Based on the Au-CNN nanohybrid film,a solid-state ECL sensor for cyanide detection has been constructed.The sensor used cyanide-mediated etching of Au NPs to recover the ECL emission of Au-CNN nanohybrids initially inhibited by Forster resonance energy transfer(FRET)from CNNs to Au NPs.The ECL sensor had a sensitive response to cyanide with a detection limit of 50 nM,and showed high specificity due to ultra-strong complexation between Au ion and cyanide.In chapter 3,a special reaction system containing a mixture of SCN-,H2O2,and NH3/NH4Cl has been designed to achieve the regulation of the ECL response of Au-CNN nanohybrid film by Cu2+.Then,a novel ECL sensor for Cu2+ detection was constructed based on the dual inhibition of Cu2+.That is,Cu2+ catalyzed the decomposition of H2O2 and weakened the etching of Au NPs,then suppressed the ECL signal.In addition,Cu2+ can also complexed with CNNs to form CNNs-Cu2+,which suppressed the system emission.As shown in experimental results,the sensor has a linear realationship to Cu2+ in the range of 5 nM to 500 nM and the detection limit is 5 nM.In chapter 4,carbon nitride nanomaterials were developed as a novel ECL co-reactant.The feasibility of using g-C3N4 nanomaterials as co-reactant for the ECL of Ru(bpy)32+ has been investigated.The mixture of CNNs and Ru(bpy)32+ solution were firstly prepaed by mixing both at a certain ratio,and then modified on a glassy carbon electrode followed by coating with a layer of nafion film.Compared to Ru(bpy)32+-nafion film,the CNNs/Ru(bpy)32+-nafion film shows enhanced ECL emission,indicating that CNNs could act as co-reatant of Ru(bpy)32+.We also examined the effect of various reaction conditions on the enhancement of the system ECL.Based on this co-reaction system,an ECL sensor for folic acid detection has been developed.