Synthesis Of Non-aromatic Fluorescent Materials By Amidation Reaction And Its Properties

The phenomenon that non-aromatic organic fluorescent compounds without typical fluorescent groups can emit fluorescence has attracted the attention of more and more scientists.Compared with aromatic fluorescent materials,the non-aromatic organic fluorescent compounds have excellent water solubility and biocompatibility,lower toxicity and simple preparation process due to it carries multiple functional groups,such as amino,carboxyl,hydroxyl and amide,which are also important functional groups that make up amino acids,peptides and proteins.However,due to the short research time and the complexity of the structure of non-aromatic organic fluorescent materials,it is difficult for researchers to determine their luminous centers,which severely limits their application fields and further development.In this paper,polycarboxylic acids and polyamine molecules were used as raw materials to prepare non-aromatic fluorescent small molecules,polymer dots,and composite materials assembled using small molecules via amidation reaction with acid chloride method and hydrothermal method.Through a series of characterization and analysis on the structure and fluorescence properties of non-aromatic fluorescent materials,the corresponding fluorescence emission mechanism was proposed,and their application in multiple fields was also explored.Significantly,this research will provide ideas for the subsequent preparation,application,and luminescence mechanism of non-aromatic fluorescent materials,as well as provide a guiding significance for understanding bioluminescence in nature.In this paper,the detailed research contents are as follows:1.Citric acid(CA)and N-aminoethylpiperazine(AEP)were used as raw materials to synthesized an amino acid-like non-aromatic fluorescent molecule CA-AEP by the acid chloride method.Optical characteristics indicate that the space electron delocalization system formed by carboxyl,amino and hydroxyl clusters was the luminescent center.Interestingly,CA-AEP can emit weak light in dilute solution and emits strong blue fluorescence under high concentration and solid conditions,showing concentration enhanced emission(CEE)and aggregation induced emission(AIE)characteristics.These properties are derived from various types of clusters that CA-AEP can form under different conditions and lead to different luminescent behaviors.In addition,CA-AEP also has high selectivity,sensitivity and anti-interference ability in detecting Hg2+.Significantly,this work not only provides a method for designing and preparing amino acid-like light-emitting biomolecules,which can help further clarify the light-emitting behavior of biomolecules,but also further expand the application field of light-emitting biomolecules.2.CA and AEP were used as raw materials to prepare luminescent C-PDs by a simple hydrothermal method.The prepared C-PDs have bright blue emission,a quantum yield of 56 %,good water solubility,light stability,and temperature sensitivity.In addition,it was experimentally verified that the photoluminescence of the C-PDs originates from two components: one is the amide molecule generated by the reaction between AEP and CA,and the other is the carbon core generated at a high temperature.What's more,the fluorescence of C-PDs is temperature-dependent and has excellent sensitivity and recoverability.Non-aromatic C-PDs/epoxy resin composites were prepared by doping C-PDs into epoxy resins,showing more excellent temperature response properties,which may be caused by the change of dielectric constant of the medium around C-PDs.In addition,the fluorescence of C-PDs can be effectively quenched by Hg2+,while the addition of biothiols can restore the fluorescence of C-PDs.3.Non-aromatic fluorescent silica microspheres(Si-FMs)of around 150 nm were prepared by the St?ber method using non-aromatic fluorescent small molecules CA-AEAPMDS containing silanol groups at the ends and TEOS.After heating in an oven at 120 ?,the fluorescence quantum yield of Si-FMs reached 70.0%(named Si-FMs-120).Interestingly,Si-FMs-120 shows different detection performance in different solvents.When using absolute ethanol as a dispersant,Si-FMs-120 can be used for qualitative and quantitative detection of Fe3+ with a detection limit of 37.8 n M.And when using deionized water as a dispersant,it can be used as an ON-OFF-ON fluorescent probe.The fluorescence of the probe was quenched by Hg2+ and then recovered by biothiol.The detection limit of Hg2+ is as low as 34.9 n M.In addition,organosilicon fluorescent nanoparticles(Si-NPs)around 30 nm were synthesized by changing the experimental conditions.It had a uniform particle size and a bright blue fluorescence emission.Si-NPs exhibit excellent stability under ultraviolet irradiation and a wide p H range,and their improved stable optical properties are attributed to the protection of the silica matrix.Moreover,the effectiveness of Si-NPs for potential fingerprint detection on a variety of substrates has been demonstrated.4.Non-aromatic polymer dots(N-PDs)were synthesized by amidation reaction of polyethyleneimine(PEI)and CA via hydrothermal method.The reasons for the fluorescence emission of N-PDs were discussed by comparing experimental phenomena.Significantly,N-PDs can be used as excellent fluorescent probes to detect Cu2+ and Cl O-in aqueous solutions.Cu2+ can be combined with the PEI portion of N-PDs to form a copper amine complex,and then quench the fluorescence by internal filtration.Cl O-can oxidize the hydroxyl groups on the surface of N-PDs to form a positive charge,preventing the electron transfer between the hydroxyl group and the chromophore,and then quenching the fluorescence of N-PDs.Finally,N-PDs were successfully applied to the detection of Cu2+ and Cl O-in environmental water samples.