Study On The Application Of Layered Double Hydroxides In Cosmetics

There are a large number of microorganisms,bacteria,fungi and other pathogenic microorganisms in nature.Some microorganisms can pollute the environment,destroy materials?cosmetics?in life,and endanger animals and plants.Therefore,one or more bacteriostatic agents must be added to the product to prevent spoilage.However,the discoloration and toxicity of many inorganic antibacterial agents limit their use on the human body.Organic antibacterial agents also have the disadvantages of susceptibility to sensitization and poor photothermal stability.Therefore,it is necessary to study antibacterial materials with excellent properties.This dissertation is based on the theory of intercalation and assembly of hydrotalcite materials,with layered double hydroxides?LDHs?as the main body,and DL-mandelic acid?MA?and kojic acid?KA?as the objects.Hydrotalcite intercalation materials ZnAl-MA-LDH and ZnTi-KA-LDH were constructed by ion exchange method.Their various types of characterization and performance were explored.At the same time,the ZnTi-LDH with different initial molar ratios of Zn²⁺/Ti⁴⁺was explored,and the antibacterial properties of LDO obtained after calcination at different temperatures were investigated.The inhibitory effect of hydrotalcite materials on microorganisms has been systematically studied to solve problems such as the safety of organic antibacterial agents,poor photothermal stability,and toxicity of inorganic antibacterial agents.LDHs/organic molecular composite cosmetic antibacterial materials have been successfully constructed.The detailed contents of this paper are listed as follows:?1?Inorganic-organic composite cosmetic antibacterial material ZnAl-MA-LDH was successfully prepared.The thermal and light stability of ZnAl-MA-LDH is much better than that of pure MA,and the release time of MA after intercalation is prolonged,which in turn prolongs the efficacy of MA.The antibacterial experiments show that the novel nanocomposites have good antibacterial activity against Escherichia coli,Staphylococcus aureus and Candida albicans.?2?The organic acid KA with double efficacy of whitening and bacteriostasis was intercalated into ZnTi-CO₃-LDH to prepare inorganic-organic host-guest material ZnTi-KA-LDH.ZnTi-KA-LDH was successfully prepared and crystallized by XRD,FT-IR,SEM and TG-DTA.The thermal stability of the ZnTi-KA-LDH was better than that of pure KA before intercalation.Sustained-release experiments show that ZnTi-KA-LDH not only prevents KA from directly contacting the skin,but also maintains the concentration of KA at the desired concentration for a long period of time,prolonging the action time of KA.In addition,ZnTi-KA-LDH still has good whitening effect by inhibiting levodopa oxidation.Antibacterial experiments found that ZnTi-KA-LDH has the effect of inhibiting Pseudomonas aeruginosa and Escherichia coli.?3?ZnTi-CO₃-LDH precursors with molar ratios Zn²⁺/Ti⁴⁺of 2:1,3:1,4:1 and 6.25:1were prepared,respectively.The nanocomposite metal oxide obtained after calcination at500?,600?,800?,1000?and 1200?.The structure and morphology of hydrotalcite and its calcined composite oxides were characterized by XRD and SEM.And the antibacterial effect of nano-composite metal oxides with different Zn²⁺/Ti⁴⁺ratios was explored.The results show that Zn_6.25Ti-LDO has a good antibacterial effect against Candida albicans,and the inhibitory effect of Zn₄Ti-LDH on Staphylococcus aureus after calcination at 500?is the best among the studied samples.