Research On Electrochemical Detection Of Dihydroxybenzene Contaminants In Aqueous Environment

Dihydroxybenzene isomers is a class of typical environmental organic contaminants,including hydroquinone（HQ,p-dihydroxybenzene）,catechol（CC,o-dihydroxybenzene）and resorcinol（RS,m-dihydroxybenzene）,which is harmful to water quality and human health.However,due to their similar structure and physicochemical properties as well as coexist in water,it is very difficult to quantitatively and simultaneously detect isomers in water resource.So far,the accurate identification and detection of isomers has become a serious challenge.Thanks to the merits of high sensitivity,good selectivity,wide response range and simplicity,we farbicate electrochemical sensor to detect dihydroxybenzene isomers.The key to the development of an electrochemical sensing platform lies in the choice of interface materials,so we designed heteroatom-doped nanocarbon materials to construct dihydroxybenzene sensors.This article details the application of heteroatom-doped nanocarbon to detect isomers and investigates the intrinsic relationship between the sensing materials and electrochemical performance to reveals the sensing mechanism of isomers.By designing three heteroatom-doped nanocarbons,the author explores their electrocatalytic oxidation activity in the distinguishing and sensing of dihydroxybenzene isomers and provides an accurate direction for the preparation of sensitive materials with high conductivity,excellent activity and specificity.The main research contents and conclusions are as follows:1.Nitrogen-doped nanocarbon（NC）materials were prepared by high-temperature calcination of the mixtures of melamine and L-alanine,which were used for simultaneously sensing toward HQ and CC.The SEM and TEM images show that the NC presents a porous nanosheet structure with high crystallinity and the lattice width is ca.0.34 nm.BET experiment shows that NC has a mesoporous structure with total pore volume of 0.383 cc g^-1.The linear ranges of NC sensing platform for HQ and CC are 0.60～8400μM and 8400～25650μM,0.60～389.8μM and 486.4～5110μM,respectively,and corresponding limits of detection（LOD）is 0.2μM.This work facile constructs the NC sensor for simultaneous detection of HQ and CC,abundant N species such as pyridine N and pyrrole N in NC act as active sites to promote electrochemical oxidation of HQ and CC molecules;2.Boron-nitrogen-co-doped nanocarbons（BNC）was prepared by pyrolyzing a mixture of melamine,L-alanine and boric acid in N₂,and BNC was used for the simultaneous sensing of HQ and CC.It is found that BNC was porous nanosheet structure with defects-rich according to XRD and Raman analysis.The specific surface area of BNC is 726.98m² g^-1,which is 7 times higher than that of NC.Due to the incorporation of B atoms into nitrogen-doped nanocarbon induces abundant defects structurally,and then the resulting BNC possess hierarchical pore structure.The LODs of the BNC sensor for HQ and CC are 33.3 and 16.3n M,respectively.HQ and CC have two broad linear ranges of 0.099～43340μM and 0.049～5110μM,respectively.In addition,the chemical state of BNC before and after sensing is deeply investigated by means of FT-IR and XPS.More importantly,we study the adsorption behavior of HQ and CC on BNC based on first-principles DFT and crystal orbital Hamiltonian population（OCHP）,revealing that the introduction of B atoms into nitrogen-doped nanocarbon,not only enhance the adsorption of HQ and CC on substrate,but also,increase adsorption energy difference between HQ and CC,which dramatically boosts the response of two isomers.The electrochemical performance enhancement was ascribed to higher content of doping atoms（N and B）and hierarchical pore structure of BNC than NC.3.The cobalt-nitrogen co-doped nanocarbon（A-Co-NC）material was prepared by high-temperature calcination in nitrogen and utilized for the simultaneous detection of dihydroxybenzene isomers.The SEM and TEM images presented thin nanosheet structure for A-Co-NC,we further confirmed the incorporation of Co and N through EDX elemental mapping.In addition,the electrochemical performance of the A-Co-NC is regulated under the optimal p H,applied potential and material modification.The kinetic process of isomers is explored through the relationship between scanning rate and peak current.Results showed that the kinetic process of HQ and CC is controlled by adsorption and diffusion,while the kinetic process of RS is mainly controlled by diffusion.In addition,we further investigated its anti-interference ability with satisfactory results.