Functionalization Of Two-dimensional Carbon-rich Materials And Its Analytical Application

Since graphene won the Nobel Prize,two-dimensional materials have been widely applied in the fields of energy,electronic devices and biosensing.Two-dimensional materials have unique physical and chemical properties,optical and electrical properties.Especially in the field of biosensing,two-dimensional materials have attracted increasing attention.On the one hand,the construction of biosensors needs to find new materials that can exhibit higher performance.On the other hand,it is important to further optimize the performance of the obtained materials by functionalization.In this way,the material can give full play to its advantages,so that the biosensing exhibits more excellent performance.Therefore,in order to further improve the sensitivity,accuracy,selectivity and portability of biosensors,the functionalization of two-dimensional materials is very necessary.This paper focuses on the covalent and non-covalent functionalization of the two-dimensional materials carbon nitride(CN)and titanium carbide(Ti₃C₂T_x,MXene)to improve the interface properties of the material,further improve the connection between the material and foreign biomolecules,regulate the surface properties of the material or improve the stability of the material.Thus,functionalization makes materials better used in the field of biosensing.1.As an emerging 2D carbon material,graphitic carbon nitride(CN)has drawn much attention for applications ranging from photo-/electro-catalysts to biosensors.Interfacial modification of CN is fundamentally vital but is still in its infancy and remains challenging due to the low reactivity of CN.Here we report that,in conjunction with a?-?stacking interaction,bulk CN could be simultaneously exfoliated via facile mechanical grinding.The obtained CN nanosheets(m-CNNS)not only retained the pristine optoelectronic properties of bulk CN but also enriched a friendly interface for further coupling biomolecules with advanced properties,overcoming the deficiencies of CN in surface science.The m-CNNS were further covalently linked to a DNA probe,and the resultant electrochemiluminescent biosensor for the target DNA exhibited much enhanced sensitivity with respect to that obtained by direct physical absorption of the DNA probe on unmodified CNNS.This noncovalent exfoliation and interfacial modification should greatly expand the scope of potential applications of CN in areas such as biosensing and should also be applicable to other 2D materials in interface modulation.2.Based on the non-covalent?-?stacking interaction between carbon nitride and aromatic molecules proposed in the previous work,we selected CNNS/AF system(donor-acceptor self-assembly system)from a variety of aromatic dye molecules.AF is the most efficient molecule for quenching the fluorescence of CNNS.According to the data of UV-Vis absorption spectrum,fluorescence lifetime,and energy level position,we proposed that the possible fluorescence quenching mechanism of CNNS/AF is fluorescence resonance energy transfer(FRET)and photoinduced electron transfer(PET).However,the distance can sensitively affect the efficiency of FRET and PET,which in turn caused the changes of fluorescence intensity.Based on this principle,we used the CNNS/AF system to construct a highly sensitive biosensor for detecting telomerase activity.The sensor obtains a wider sensing range and lower detection limit.In addition,in the early and later stages of testing,the state of the biosensor can be investigated by testing the dynamic curve of the CNNS,which provides a method for evaluating the reliability of the biosensor.3.As an emerging 2D material,MXene combing hydrophilic surface,metallic conductivity and rich surface chemistry,has drawn much attention for applications ranging from electronic devices to electrochemical energy storage.However,the stability of MXene needs improvement,which is crucial to related applications.Here,we report a facile silylation reaction for efficient stabilizing the MXene against structural degradation due to spontaneous oxidation and improved surface properties with adjustable hydrophilicity.(3-Aminopropyl)triethoxysilane functioned MXene(APTES-MXene)was chosen as the model to evaluate the stability and surface property changes.By measuring the UV–Vis absorbance change of samples,the stability could be facilely monitored.The stability of the MXene in air degraded by 17.1%,35.4%,65.3%and 95.6%after 1,3,6 and 11?days,respectively.In contrast,the stability of APTES-MXene only reduced 20.8%after 11?days.Other silylating reagents were also explored and exhibited similar boosted stability with additional surface regulation from hydrophilic to hydrophobic.