New-Type Nitrogen/Sulfur-containing Carbogenic Polymer Dots:Synthesis And Their Fluorescence Properties

Carbogenic quantum dots have potential applications in bioimaging,drug-delivery,photocatalysis,energy storage/conversion,and sensors due to their bright luminescence,high photostability,low toxicity,excellent water solubility,and easy availability.?1?In this paper,a simple approach has been designed for synthesis of nitrogen-containing carbogenic polymer dots?NPDs?through polymerization of polybromopyrroles assisted by microwave irradiation in an alkaline ethanolthermal environment at 80 °C.The structure,composition,morphology,and optical properties of NPDs were characterized with XRD,Raman,FT-IR,XPS,?-Potential,high-resolution TEM,scanning probe microscopy?SPM?,UV?Vis,and photoluminescence techniques.The results indicated that:The NPDs have tunable size distribution,high yield?25%?,and a high degree of graphitization.The absolute quantum yield of NPDs is greatly improved to be 24% from 3% after simple surface reduction by NaBH4.Twenty aromatic compounds were tested in the role of quenchers to induce fluorescence quenching of NPDs.Through theoretical calculations and instrumental analysis,we conclude that non-photochemical quenching dominates the quenching of NPDs by aromatic compounds.NPDs show high sensitivity to 2,4,6-trinitrophenol even if the solution contains six other ACs such as aniline,nitrobenzene,4-nitrobenzaldehyde,4-nitrotoluene,dopamine,and N,N-diethylaniline,which cannot induce fluorescence quenching of NPDs under excitation at 360 nm.This result ensures effective fluorescent detection of trace 2,4,6-trinitrophenol through NPD-based sensors.?2?A simple approach has been designed for synthesis of sulfur-containing carbogenic polymer dots?SPDs?through polymerization of tetrabromothiophene assisted by heating reflux in PEG400.The structure,composition,morphology,and optical properties of NPDs were characterized with XRD,FT-IR,high-resolution TEM,scanning probe microscopy?SPM?,UV?Vis,and photoluminescence techniques.The results indicated that:The SPDs have a narrow size distribution.There are many hydroxyl and carbonyl functional groups on the surface of the SPDs.The presence of large number of surface hydroxyl groups causes it to Fe³⁺ with a specific recognition.SPDs show high sensitivity to Fe³⁺ even if the solution contains six other metal ions such as Ag+?Hg²⁺?Cd²⁺?Cr³⁺?Pb²⁺?Cu²⁺,which cannot induce fluorescence quenching of SPDs under excitation at 280 nm.So SPDs can be used to detect Fe³⁺ in water.