Preparation And Application Of Multilevel MXene/Sodium Alginate Silica Phase Change Microcapsules

Solid-liquid phase change materials（PCM）are an environmentally friendly class of materials that can store and release heat through phase changes.However,such materials have problems such as easy leakage and low thermal conductivity.By selecting the appropriate type of shell to microencapsulate solid-liquid PCM,it can not only solve the problem of easy leakage and improve its thermal conductivity,but also design the shell type to realize the application of PCM in building energy saving,aerospace,wearable devices and other fields.In order to broaden the application field of PCM,the MXene-modified multi-level phase change microcapsule MXene/SA/Si O₂@C₂₂ MEPCM was obtained by designing the structure of the outer shell of the phase change microcapsule,encapsulating n-docosane(C₂₂)as PCM in the silicon dioxide（Si O₂）shell,and coating the Si O₂ shell with sodium alginate（SA）functional layer and MXene nanosheet.Based on the excellent temperature control performance of PCM and the good conductivity of MXene,cholesterol oxidase（Chox）fixed on the surface of MXene/SA/Si O₂@C₂₂ MEPCM showed ultra-sensitive detection of cholesterol（Cho）at medium and high temperatures.Based on PCM’s reversible thermal energy storage and release and MXene’s excellent light absorption properties,sustainable desalination under intermittent sunlight is possible.The specific research content is as follows:（1）The prepared MXene/SA/Si O₂@C₂₂ MEPCM was immobilized to form Chxo-MXene/SA/Si O₂@C₂₂ MEPCM after immobilization of Chox,which not only had a clear hierarchical microstructure and required chemical and biological components,but also had a phase change enthalpy of more than133 J g^-1,which could realize dynamic thermal management and realize the thermal temperature regulation of immobilized Chox.Using Chox-MXene/SA/Si O₂@C₂₂ MEPCM modified GCE as the working electrode,an electrochemical biosensor for Cho detection was constructed.When Cho is detected at a higher detection temperature,the phase change of PCM realizes the in-situ regulation of GCE microenvironment temperature,effectively prevents the protein denaturation of Chox,and minimizes the influence of heat on the biosensing performance of cholesterol biosensor.The results showed that the sensitivity of the biosensor reached 4.63 m M^-1 cm^-2 at 60°C,and the detection limit reached 0.081 m M.It has higher sensitivity and lower detection limits than the 3.49 m A m M^-1 cm^-2 and the detection limit of 0.112 m M compared to the heatless management biosensor.In addition,the prepared biosensors have been proven to provide highly accurate and reliable biosensing detection of real biological samples over a wide temperature range to meet the requirements for Cho detection in harsh environments.（2）Multi-level phase change microcapsules MXene/SA/Si O₂@C₂₂MEPCM are applied as photothermal materials to solar interface evaporation systems to achieve sustainable desalination.The introduction of SA and MXene nanosheets makes the microcapsules have more than 97%high light absorption capacity and good wettability,and the evaporation rate reaches 2.11 kg m^-2 h^-1under one sunlight.Moreover,MXene/SA/Si O₂@C₂₂ MEPCM has a high latent heat capacity of more than 150 J g^-1,which is conducive to the latent heat absorption and release of the evaporation system and improves its continuous evaporation performance under light fluctuations.Compared with the evaporator without PCM core,the evaporator based on MXene/SA/Si O₂@C₂₂MEPCM increased the evaporation mass by 1.4 kg m^-2 after five continuous evaporation processes under sunlight and free cooling.Moreover,under 7.5 h of natural sunlight on a cloudy day,the total water yield increased by 1.01 kg m^-2 compared with the without PCM evaporator.The above results provide ideas for the development of multi-level PCM microcapsules and their application in temperature regulation and thermal energy storage and release.