Synthesis Of Persistent Luminescence Nanoprobes And Application In Plant Imaging

Nanoparticles（NPs）,including manufactured nanoparticles and nanoplastics,have become a matter of concern as a new type of pollutant in recent years,mainly due to the increasing production of nanomaterials and the uncontrollably environmental emission of nano-waste.Once exposed to the environment,these NPs not only affect plant growth and development,but also circulate among various food webs in an ecosystem through the edible parts of plants,which brings unforeseen or unintended risks on organism health.There is an increasing amount of research on the phytotoxicity of nanoparticles and their fate in plants,nonetheless,the lack of high-sensitivity tracking techniques in vivo constrains intensive research on the plant-nanoparticle interaction.Herein,we have overcome this limitation by first introducing persistent luminescence nanoparticles（PLNPs）as an imaging probe,which can detect the NPs distribution in whole plants with high sensitivity by completely eliminating interference from autofluorescence.In order to develop new approaches for visual tracing of uptake and transport of different nanoparticles in plants,two kinds of optical nanoprobes were synthesized based on PLNPs in this study.The main research contents are as follows:（1）In this chapter,Zn_1.1Ga_1.8Ge_0.1O₄:Cr_0.005 persistent luminescencenanomaterials（ZGGC）with good dispersibility,small and uniform size and near-infrared persistent luminescence emission,were synthesized by a hydrothermal method.After polyethyleneimine modification on the surface of ZGGC,the zeta potential changed to+63.2 m V,this was termed ZGGC（+）,and the zeta potential of PLNPs modified by polyacrylic acid was-41.5 m V,this was termed ZGGC（-）.Additionally,the ZGGC（+）and ZGGC（-）dispersions exhibited good stability in water and can still dispersed in solution after standing for 7 days,making them appropriate for tracing the charge-dependent uptake of NPs in hydroponically cultivated plants.In this work,mung bean（Vigna radiata L.）with fast growth was adopted as a model plant to evaluate the short-term toxicity of those nanoprobes on dicotyledon species.The results demonstrate that high-concentration ZGGC（+）and ZGGC（-）have no significant toxic effect on mung beans.Subsequently,the temporal and spatial distribution of persistent luminescence（Pers L）signals from PLNPs-treated plants was collected by an imaging system.Pers L signals of positively charged PLNPs were observed in the whole exposed portion of plant roots,while negatively charged PLNPs were mainly in the root collars instead of exposed portion.With prolonged exposure,the presence of Pers L signals in leaves indicated the long-distance translocation of differently charged PLNPs from roots to leaves.To confirm the results of Pers L imaging,electron microscopes were adopted as complementary techniques and proved the internalization and accumulation of PLNPs in plants.（2）In this chapter,m Si O₂-Zn_1.3Ga_1.4Sn_0.3O₄:Cr_0.005,Y_0.003 persistent luminescence nanomaterials（m ZGSO）with good monodispersity,uniform size and near-infrared Pers L emission were synthesized by a mesoporous silica（MSN）template method.Subsequently,C=C bonds were anchored on MSN surfaces through modified with silane coupling agent（MPS）,making m ZGSO to participate in the polymerization of styrene,and then be coated concentrically by a polystyrene（PS）layer.The nanoplastic with a PLNPs core（m ZGSO@PS）used as a tracer,which can emit Pers L without in situ excitation and has the surface properties of polymer.The m ZGSO@PS was negatively charged in deionized water and 1/4 Hoagland solution.Moreover,m ZGSO@PS suspension exhibited long time stability in water 2 months later.For hydroponic experiment,rice（Oryza sativa L.）seedling roots were partially exposed to a 1/4 Hoagland solution containing m ZGSO@PS and Pers L imaging were performed after 5,10 and 15 days.Results showed that rice roots can internalize and translocate nanoplastics with increasing exposure time.To assess the effects of airborne nanoplastics,rice seeds were exposed to those particles by adding m ZGSO@PS suspension to the surface and Pers L imaging were performed after 5,10 and 15 days.Results showed that m ZGSO@PS particles could penetrate rice husks and accumulation on brown rice.