Research On The Synthesis And Luminescence Mechanism Of Non-conjugated Polyamine Nano-particles And The Properties

Non-conjugated Polymer Fluorescence Nano-particles（NCPF NPs）have created new avenues for sensors,bioimaging,drug and gene delivery,and other biomedical applications.Ideal NCPF NPs should be autofluorescent without doping an external fluorochrome,which have favorable water solubility,high quantum yield,good photostability,and low toxicity.In the synthesis of NCPF NPs,the larger molecular weight of polyamine macromolecules and their active groups such as primary amine（-NH₂）make the size and distribution of NCPF NPs difficult to control,and the labeling efficiency was decreased.The stability of NCPF NPs was determined by the unreacted active groups.In addition,due to aminos in NCPF NPs could coordinate with various metal ions,the detection of metal ions was limited.1.0-Generation Dendrimers Polyamidoamine or branched poly（ethylene imine）crosslinked with 2,3-Diketogu-L-lonic acid（DKG）which was oxidation of ascorbic acid by one-step hydrothermal method.Under hydrothermal conditions,yellow-green photoluminescence polyamidoamine（PADF NPs）or poly（ethylene imine）nanoparticles（bPEIDF NPs）were produced.The fluorescence mechanism of the produces was obtained by optimizing the synthesis conditions,ion recognition and the study of fluorescence properties.The results are as follows:Yellow-green Non-conjugated Polyamine Fluorescence Nano-particles（NCPAF NPs）were obtained by cross-link with DKG and PAMAM or bPEI.The average particle sizes of product were 4.86 and 1.2 nm,and the standard deviation of particle size were s₁²=0.5648,s₂²=0.1826,respectively.When the concentrations of PADF NPs than 1mM,the concentration quenching of fluorescent materials can be avoided.The fluorescence intensity of PADF NPs was quenched under alkaline conditions,but it could be stabilized for 5 d in acid/neutral solutions（pH=3.00,7.00;respectively）at 35℃.The fluorescence intensity of bPEIDF NPs in acid/alkaline solutions（pH=3.00,12.00,respectively）at 35℃could be stabilized for 7 d,and the acidic environment could inhibit the blue shift of bPEIDF NPs due to its improvement ofstructural defects.Fluorescence of NCPAF NPs was quenched by the Cu²⁺formed complex with N,O atoms of NCPAF NPs,and the corresponding linear equation of concentration of Cu²⁺-fluorescence intensity was calculated:（1）PADF NPs:Y₁=-40.591X+100.12,R₁²=0.9869,（2）bPEIDF NPs:Y₂=-192.11X+303.32,R₂²=0.9979,Where Y₁,Y₂ denote the fluorescence intensity of PADF NPs and bPEIDF NPs,respectively;X is the concentration of Cu²⁺.The exploration on fluorescence mechanism indicated that the fluorescence of heteroatom can be enhanced by chemical cross-linking or physical aggregation.In this process,the vibration and rotation of the sub-fluorophore were restricted,leading to an increase of radiative transition.the NCPF NPs always possess lex-dependent fluorescence,which indicates that there are multiple excited states.Because each one of the NCPF NPs is composed of plentiful sub-fluorophores,the NCPF NPs have a wide composition distribution,and every sub-fluorophore may be in different chemical environments,diverse fluorescence states in the NCPF NPs may exist.Compared with 1.0G PAMAM with spatial symmetry,bPEI with short branched chains can formed denser clusters by cross-linking reaction with DKG.The Cu²⁺can be formed complex with N,O atoms of NCPF NPs,and leading to the fluorescence quenching via energy transfer or inner filter effect.