Nano-pesticides Prepared By Flash Precipitation In Micro-mixer Based On Green Carriers And Their Applications

The demand for food is increasing as the population increases,which requires a stable and higher grain yield.At the same time,crop losses caused by pests and diseases reach to 20-40%of total yield,making it more challenging to realize the Zero Hunger goal by 2030.Pesticides with the characteristic of quick-action are a powerful means to achieve this goal.However,traditional pesticide formulations containing large amounts of organic solvents and additives often loss into the surrounding ecological environment through volatilization,runoff,and rainwater erosion.Only 0.1%of the pesticide active ingredients can reach the target organism,which leads to resource waste and environmental pollution.Therefore,it is urgent to develop a new type of pesticide formulations that are highly efficient and environmentally friendly.Currently,the combination of nanocarrier and nanotechnology for construction of intelligent nanopesticide delivery systems to achieve the targeted release of pesticide active ingredients has become a hot research area.In view of the commonly used nanopesticide carrier materials accumulate continuously in the environment due to their non-degradability,causing long-term effects to the ecosystem.The development of green carrier materials with safe,non-toxic,biodegradable and biocompatible to create environmentally friendly nanopesticide formulations with cost-effective has become an inevitable trend to ensure food and ecological security.In this thesis,a series of green carrier materials with good biocompatibility were used to prepare functional and environmentally friendly nanopesticides rapidly and efficiently using a multi-inlet vortex mixer(MIVM)by kinetically controlled enhanced molecular self-assembly,i.e.,Flash nanoprecipitation(FNP).The morphology and size of the nanopesticide particles can be effectively controlled by adjusting the process parameters involved in microfluidic mixing process.Moreover,the wettability and adhesion of nanopesticides on the foliage of different target plants were investigated and the interaction mechanism between nanopesticides and target leaf surface was studied in depth.Then,the distribution and deposition process of nanopesticides on the leaf surface of target crops,as well as the transport behavior and migration pattern in target plants and soil were further investigated in a non-invasive manner by the in situ tracer method of optical imaging technology.In addition,the in vitro slow-release behavior and controlled release mechanism of nanopesticides were revealed.Finally,the control efficacy of nanopesticides against pest and disease were investigated.The research contents and results are as follows.1.Natural sophorolipids,secondary metabolites of microbial fermentation,were selected as carrier materials.Two different types of sophorolipids(acidic and lactonic)were successfully separated by alkali hydrolysis and column chromatography,and their structures were confirmed by nuclear magnetic resonance technique,and a series of nanopesticides loaded with lambda-cyhalothrin were successfully prepared by FNP technique.The study found that the structure of the nanopesticides could be controlled by adjusting the weight ratio of acidic and lactonic sophorolipids,and spherical nanopesticides with a size of 120 nm and narrow particle size distribution(PDI=0.109)were obtained.The particle sizes(120-174 nm)and particle size distributions(PDI=0.099-0.138)of the nanopesticides could be flexibly controlled by changing the Reynolds(Re)number.Furthermore,the nanopesticides showed good wetting properties on the plant leaves,good stability,and slow-release performance.Importantly,the as-prepared nanopesticides demonstrated the higher control efficacy against the Hyphantria cunea larvae compared to commercial emulsifiable concentrate formulations.2.A continuous FNP technique with a combination of two MIVM was employed to construct a multifunctional nanopesticide delivery system using amphiphilic bovine serum albumin as the carrier,polydiallyldimethylammonium chloride(PDDA)as an antimicrobial component and abamectin as a model pesticide.The multifunctional nanopesticide demonstrated enhanced leaf adhesion,simultaneously control plant diseases(Escherichia coli and Botrytis cinerea as model pathogens)and pests(Plutella xylostella L)The results showed that the nanopesticide exhibited a uniform spherical morphology,good storage stability,slow-release behavior(>218 h),high drug loading capacity(30%),and ideal inhibition effect against Botrytis cinerea.In addition,the effects of different PDDA additions on the wettability and retention of nanoparticles on the foliage of target plants and on the inhibition of crop bacterial diseases(Escherichia coli)were investigated.Finally,bioassay tests demonstrated that the nanopesticide formulation had better control efficacy against Plutella xylostella L compared to commercial emulsion in water.3.A novel type of enzyme-responsive fluorescent nanopesticides was successfully prepared by the continuous FNP technique using fluorescein isothiocyanate(FITC)-labeled bovine serum protein as the carrier,anionic polysaccharide gum arabic as the stabilizer,and hydrophobic abamectin as a model pesticide by the continuous FNP technique.The as-prepared fluorescent nanopesticides exhibited good water dispersibility,excellent storage stability,and better foliar affinity compared to commercial formulations.The controlled accelerated release behavior under trypsin stimulation means that the nanoparticles can be rapidly disintegrate to release abamectin in trypsin-rich lepidopterans.The interaction mechanism of nanopesticides with leaves of different hydrophobic target plants(cabbage and cucumber)and the transport pattern in cucumber were systematically investigated by fluorescence imaging.The results showed that the nanopesticides could be uniformly distributed on the target leaves and mainly concentrated on the roots of the target plants.Furthermore,the fluorescent nanopesticides exhibited the high control efficacy against Plutella xylostella L,which was comparable with commercial emulsifiable concentrate formulation.4.A series of deformable hollow mesoporous organosilica nanoparticles(HMONs)based on organic group-enriched silicon precursors was fabricated by FNP technique.The synthesized HMONs possessed controllable softness,high surface area(571.1 m~2/g),narrow size distribution(PDI=0.03),and large hollow cavity.The effects of the fluid components,co-solvent,and ratio of silicon source precursors on the morphology and size of HMONs were systematically investigated.The particle sizes(457-629 nm)of the HMONs could be tuned by easily controlling the mixing Reynolds(Re)number.More importantly,atomic force microscopy(AFM),transmission electron microscopy(TEM),and small angle X-ray scattering(SAXS)results revealed that the as-obtained HMONs were have a“soft”structure in solution(Young’s modulus of53.2 MPa)in solution.Two types of abamectin nanopesticides were prepared by selecting deformable and non-deformable HMONs as drug carriers,and both of them exhibited sustained release properties(>270 h).Deformable HMONs demonstrated the improved affinity to the leaf surface as well as the enhanced insecticidal activity to Meloidogyne incognita.