Preparation Of Antibacterial Carbon Dots And Their Performance As Water-based Lubricant Additive

With the increasing awareness of environmental protection and the advent of the energy crisis,the call for the development of new lubricants to replace traditional oil-based lubricants has become increasingly strong.Water-based lubricants have attracted the attention of scholars due to it's environmental protection,renewable,wide source of raw materials and low price.However,water-based lubricants currently have many problems.Various lubricating additives are needed to improve the performance of lubricants.Considering that the addition of multiple ingredients may affect each other,it is of great significance to look for a lubricant additive with two or mutifunction for the development of water-based lubrication.In recent years,carbon dots(CDs)have attracted the attention of scholars in various fields due to their excellent physical and chemical properties.Therefore,this paper successfully prepared water-based lubricant additives with lubricating property and antibacterial property by modifying polymers on the surface of CDs.The specific research content is as follows:1.Firstly,using polyethylene glycol and polyethyleneimine as precursors and passivators,P-P-CDs are synthesized in one step by hydrothermal method.The test results show that after adding 0.2 wt% P-P-CDs,the average friction coefficient of the water base fluid is reduced by59.77%,and the average wear volume is reduced by 57.97%,which effectively improves the lubricating performance of the water base fluid.At the same time,P-P-CDs have a relatively obvious inhibitory effect on E.coli and S aureus.P-P-CDs can be stably dispersed in the water base solution for at least one month without obvious precipitation.P-P-CDs can keep the suspension free of bacteria under the condition of continuous supplementation of the bacterial solution,showing strong dispersion stability and long-lasting antibacterial ability.2.In order to further broaden the application range of water-based lubricants,we use PEG,which has a wider application range and better basic lubricating property,as the base fluid in chapter 2.At the same time,in order to explore the effect of different synthesis temperatures of carbon core on the properties of the final material,CPP-CDs with lubricating property and antibacterial property are synthesized using a two-step method.At first,we synthesize carbon core with citric acid as the precursor,and then modify the carbon core with polyethylene glycol and polyethyleneimine as passivators.The test shows that in the first step of synthesizing citric acid CDs,as the temperature increases,the lubricating performance of citric acid CDs have a certain improvement.However,during the second step of modifying polymers,it is found that the synthesis temperature of citric acid CDs will affect the active sites for the second step.It is finally determined that the CPP-CDs has the best lubricating performance when the citric acid CDs synthesis temperature is 200?.When the concentration of CPP-CDs is 0.35wt%,the average friction coefficient and average wear volume are reduced by 40.08% and 49.8%respectively compared with pure PEG lubrication.The antibacterial activity of CPP-CDs generally increase first and then decrease slightly with increasing synthesis temperature of citric acid CDs,they all show excellent antibacterial ability.At the same time,the sedimentation experiment shows that CPP-CDs can be stably dispersed in the PEG base solution for a long time.The biological stability experiment finds that the suspension can keep no bacteria under the premise of continuous supplementation of bacterial solution,showing excellent continuous antibacterial ability.