Water Permeability And Ion Selectivity Of Carbon Nanotubes As Bionic Water Channels

As the demand for fresh water increases,water purification and membrane desalination technologies have been working to increase water supply in an effective manner.Due to the high energy consumption and low water permeability of reverse osmosis technology,researchers have developed bionic membranes with high permeability and low energy consumption based on Aquaporins(AQPs),However,AQPs biomimetic membranes face the problems of protein inactivation and poor selectivity in practical operation.The emergence of bionic water channels provides a new way for solving the problems above.As a commonly used bionic water channel,Carbon nanotube(CNTs)have attracted the attention of researchers in the field of water treatment.CNTs are widely used in the field of water treatment biomimetic membranes and biomimetic water channels due to their inherent nanometer size and the hydrophobic characteristics of the tube inner wall.However,in the actual development of bionic water channels based on CNTs,it is difficult to synthesize ultra-short CNTs or the synthetic CNTs always exhibit defects and low affinity for lipid membrane.Therefore,there is an urgent need to find a simple and fast CNTs synthesis method to synthesize CNTs with the feature of ultra-short and low defects,and can be fully fused in lipid membrane system to solve the problems encountered in the practical application of AQPs biomimetic membranes.In the research of this article,first of all,we used acid cutting technology treating CNTs to obtain ultra-short CNTs,but the length of the obtained CNTs can not meet the needs of preparing bionic water channels.We next employed ultrasonic cutting method in order to obtain ultra-short CNTs.The length of CNTs obtained by different processing methods was verified.We found that the power of ultrasonic cutting has a great influence on the synthesis of CNTs,the relationship between the time of ultrasonic cutting and the length of CNTs obtained decreases linearly.Secondly,a new method for preparing ultrashort CNTs by active agent-assisted ultrasonic cutting was developed.In this method,CNTs were firstly wrapped with surfactant to make them phospholipid followed by ultrasonic cutting.The CNTs prepared by this method have the characteristics of close to lipid membrane thickness,low defects and high affinity.Different types of surfactants and different surfactant dosages have different effects on the preparation of CNTs.Finally,the functional verification of CNTs obtained by acid cutting,ultrasonic cutting,and active agent-assisted ultrasonic cutting was carried out.We constructed E.coli with high expression of AQPs and extracted AQPs as a control for CNTs water channel,the water permeability and ion selectivity of AQPs and CNTs were tested in the lipid membrane system.The closer the length of the CNTs is to the thickness of the lipid membrane,the better the water transportability;the higher the affinity of the CNTs,the better the water transportability.The selectivity of CNTs water channels for ions is consistent with water permeability.The water permeability of the CNTs water channel obtained by ultrasonic cutting is 1256±137?m/s,which is 2.94 times that of acid-treated CNTs water channel and 1.43 times that of natural AQPs.The water permeability of CNTs water channel obtained by active agent assisted ultrasonic cutting is 1936±123?m/s,which is 2.21 times of natural AQPs.In this paper,an active agent-assisted ultrasonic cutting method for CNTs is developed.The synthesis of ultra-short CNTs close to the thickness of the lipid membrane.In addition,during the synthesis process,the degree of defects of CNTs is reduced while the affinity of CNTs is improved.This method further improvs the insertion efficiency of CNTs in liposome system,Thereby increasing the water permeability of the CNTs water channel.The research based on CNTs water channel has been greatly developed.This study provides a new method for obtaining high-quality ultra-short CNTs through active agent-assisted ultrasonic cutting,solving the difficult synthesis and low affinity problems faced by the bionic water channel.Therefore,the problems of protein inactivation and poor selectivity based on AQPs biomimetic membranes are solved.