Controlled Preparation And Applications Of Sulfur Nanoparticles

Sulfur is a natural,economical,and harmless material.Since ancient times,with the advantage of single element that can be obtained directly from nature,sulfur has been used to treat skin diseases and parasites,prevent plant diseases and insect pests,and manufacture gunpowder.With the development of nanotechnology,and the rooting of the principles of green chemistry in people's thinking,many excellent properties of sulfur nanoparticles have been researched.In the field of traditional biological sterilization,sulfur nanoparticles have better bactericidal activity than traditional sublimed sulfur.They have been extensively studied in animal and plant sterilization,disease treatment,anti-cancer cells,etc.In this paper,a solvent-antisolvent precipitation has been developed to prepare sulfur nanoparticles(SNPs).On this basis,microchannels were used to intensify the preparation process,and CFD simulation was also used to study the microfluidic preparation process.In addition,high gravity reactive precipitation method was also used to prepare SNPs.Moreover,the prepared sulfur nanoparticles were used for biological sterilization and the preparation of hydrophobic nano-sulfur/PVA composite films.The main research contents and results are as follows:(1)Using a traditional batch stirred tank,SNPs were prepared by an antisolvent precipitation route.The effects of various conditions such as solution concentration,solvent/anti-solvent ratio(S/AS),surfactant type,and surfactant dosage on the preparation of sulfur nanoparticles were mainly investigated.The optimal process conditions were obtained:the solution concentration is 20 mg/mL,the anti-solvent ratio is 1:20,the surfactant is CTAB,and the amount of CTAB added is 30 wt%.Furthermore,sulfur nanoparticles powder with an average particle size of about 20 nm is obtained by freeze-drying.(2)The microchannels were further used to intensify the anti-solvent precipitation process.The effects of solution concentration,S/AS,total flow rate,microchannel structure and size on the preparation of sulfur nanoparticles were mainly investigated.The optimal micro-channel preparation process conditions are:solution concentration is 20 mg/mL,S/AS is 1:10,the overall flow rate is 88 mL/min,and the Y-type microchannel with a channel size of 300?m is used.Under this optimum conditions,the average particle size of the as-prepared SNPs is 15 nm.Compared with the traditional batch stirred tank,the sulfur nanoparticles prepared by the microchannel have a smaller particle size and a narrower distribution,and the amount of anti-solvent required in the preparation process can be reduced by 50%.The difference between the mixing process of Y-type and T-type microchannels was compared by CFD simulation.The mixing effect of Y-type microchannels is better,and the T-type microchannel has longitudinal back-mixing at the intersection of the fluids,resulting in a larger particle size than Y-type microchannels.(3)High-gravity reactive precipitation was used to prepare SNPs.The effects of acid type,reaction concentration,reaction time,rotating speed of RPB,and the feed flow rate on the preparation of nano-sulfur were mainly investigated.The optimal process conditions were obtained:the acid source is hydrochloric acid,sodium thiosulfate concentration is 0.05 mol/L,the reaction time is 5 min,the rotating speed of RPB is 1500 rpm,the feed flow rates of hydrochloric acid solution and sodium thiosulfate solution are 50 mL/min and 200 mL/min.Under the optimum conditions,sulfur nanoparticles with an average particle size of 15 nm with good dispersibility.Compared with a traditional batch stirred tank,the reaction time is reduced from 25 min to 5 min.The average particle size is decreased from 50 nm to 15 nm,and the corresponding size distribution is narrower.(4)The SNPs were further applied to the sterilization and the preparation of SNPs/PVA composite films.Taking the Staphylococcus aureus and Escherichia coli as the objects,the antibacterial properties of the sulfur nanoparticles were studied.Compared with sublimated sulfur,SNPs have the much better antibacterial properties,and show a good small size effect that 15 nm particles have better properties than 50 nm particles.The SNPs/PVA composite films were further prepared through a simple solution mixing route,With the increase of the addition amount of sulfur nanoparticles from 0 to 30 wt%,the contact angle of nanocomposite films is obviously increased from 66.7°to 98.9°.The films show good hydrophobicity without affecting the hydrolysis ability.