Preparation Of G-C₃N₄-based Nanocomposites And Its Application In Photoelectrochemical Biosensing

Recently,PEC detection technology with multiple advantages,including sensitivity,cheap instrumentation with simple operation and a wide dynamic range has been widely applied to immunoassay,genosensor and cytosensor.The PEC biosensor shows inherent superiority with negligible background due to its total separation and the different energy forms of visible light as a non-intrusive excitation source and generates photoelectric signal as a detection signal.In this paper,two sensitive PEC biosensor were constructed by using special materials to enhance the photocurrent efficiency.Also,these PEC platforms with high selectivity,good repeatability,and perfect stability can serve as a potential tool for bioanalysis.1.Preparation,characterization and co-sensitizing effect of ternary nanocomposites TiO2/g-C3N4/CdS with CdSeIn this paper,a kind of ternary nano-composite with series energy level arrangement was synthesized.The material was successfully characterized by XRD and IR.The morphology of the composite was characterized by SEM and TEM.Through the analysis of XPS spectra,it is found that the Fermi energy level rearrangement occurs in the complex,which makes the ternary complex have a special arrangement of energy levels in series.The energy level arrangement of the material not only increases the absorption and utilization ratio of light,but also can be rapidly separated and converted after the generation of photogenerated electrons and holes,which has a high photoelectric conversion efficiency.The cosensitization efficiency of QDs is investigated by combining them with CdSe quantum dots.The results show that the co-sensitizing efficiency of the ternary nanocomposites with CdSe is high and can be used in the construction of photoelectrochemical biosensors for other life analysis.2.A TiO2/g-C3N4/CdS nanocomposite-based photoelectrochemical biosensor for ultrasensitive evaluation of T4 polynucleotide kinase activityHerein,an efficient photoelectrochemical(PEC)platform was constructed by a co-sensitization strategy with a cascade energy level arrangement for the ultrasensitive evaluation of T4 polynucleotide kinase(T4 PNK).Based on CdSe quantum dots(QDs)with an extremely narrow bandgap,this co-sensitization strategy offered an highly efficient sensitizer with a matching band-edge level of a ternary TiO2/g-C3N4/CdS nanocomposite.In this protocol,the ternary nanocomposite was first prepared to serve as the matrix to construct the PEC sensing platform.On the other hand,a well-designed hairpin DNA1 probe with 5'-hydroxyl termini was specifically phosphorylated by T4 PNK which would be selectively cleaved with lambda exonuclease(X.-Exo)outputting 3'-thiol end ssDNA2.After tagged with CdSe QDs,ssDNA2 was captured by the complementary capture DNA3 on the electrode surface.As a result,CdSe QDs were in close contact with the ternary nanocomposite matrix,leading to an enhanced photocurrent response.Therefore,this proposed PEC platform displayed an analytical performance with a wide linear range from 0.0001 to 0.02 U mL-1 and a low detection limit down to 6.9×10-5 U mL-1.Moreover,this teIIary nanocomposite-based platform exhibited excellent selectivity,good reproducibility,and remarkable storage stability,which shows the great potential for the T4 PNK detection and inhibitor screening.3.Photoelectrochemical DNA biosensor based on g-C3N4/MoS2 2D/2D heteroj unction electrode matrix and co-sensitization amplification with CdSe QDs for the sensitive detection of ssDNAA novel enhanced photoelectrochemical(PEC)DNA biosensor,based on a compact heterojunction g-C3N4/MoS2 and co-sensitization effect with CdSe quantum dots(QDs),was first proposed for simple and accurate analysis of a short ssDNA.In this work,the g-C3N4/MoS2 was successfully synthesized and used as the electrode matrix material to construct PEC biosensor for the first time.As expected,2D/2D heterojunction was formed between g-C3N4 and MoS2,which could promote the separation of photogenerated electron-hole pairs resulting in an enhanced photocurrent.In the present of target DNA,the CdSe QDs labeled reporter DNA was complementary pairing with target DNA which was specific recognized by capture DNA loading on self-assembled CdS QDs film,leading to close contact between CdSe QDs and g-C3N4/MoS2 modified electrode surface,thereby resulting in the enhance photocurrent intensity due to the co-sensitization effect.Under the optimal operating conditions,the photoelectrochemical biosensor demonstrated favorable accuracy and could responds to 0.32 pM(S/N=3)with a linear concentration ranging from 1.0 pM to 2.0?M.Moreover,the proposed PEC DNA biosensor exhibits high sensitivity,excellent specificity,acceptable reproducibility and accuracy,showing a promising potential in DNA bioanalysis and other relative fields.