Fabrication Of Fluorescent Sensing Based On Carbon Quantum Dots And Rare-earth Ion Complex For Rapid And Sensitive Detection Of Inorganic Pollutants In Water Samples

Inorganic pollutants in water bodies have an major impact on ecosystems and human health,therefore,the development of rapid and sensitive analysis methods for typical inorganic pollutants in water samples is significant for understanding the pollution status of water environment,water pollution prevention and guaranteeing drinking water security.Fluorescent sensing has unique advantages such as fast response,high sensitivity,easy operation and low cost,however,these fluorescent sensing still suffer from low quantum yield,complicated fabrication process and less practical applications.To solve the above issues,based on the excellent fluorescence characteristics,easy surface functionalization and environmental friendliness of carbon quantum dots and rare-earth ion complex,this paper have fabricated several novel fluorescent sensing for the rapid,highly sensitive and selective detection of several typical inorganic pollutants in water bodies,and the relevant sensing mechanism was also explored.This work includes the following aspects:?1?Nitrogen-and sulfur-codoped carbon quantum dots?N,S-CQDs?for the rapid and selective detection of sulfide and Fe³⁺were prepared.N,S-CQDs with fluorescence quantum yield of 16.1%were synthesized by one-step hydrothermal method using ammonium citrate and L-cysteine as raw materials,and its fluorescence spectra is excitation-dependent.Its selective recognition for sulfide was found,and the limits of detection?LOD,S/N=3?for sulfide is 11.0 n M?about 0.35?g/L?.While citric acid was used instead of ammonium citrate to prepare N,S-CQDs,the fluorescence quantum yield of N,S-CQDs significantly improved?69%?,and its emission spectra is nearly independent on the excitation wavelengths.It was found that this N,S-CQDs realized selective detection of Fe³⁺with LOD?S/N=3?of 14.0 n M?about 0.8?g/L?.?2?Ciprofloxacin-Eu³⁺(CIP-Eu³⁺)complex for ultrasensitive and selective detection of phosphate based on antenna effect-improved by sodium dodecylbenzenesulfonate?SDBS?was developed.It was found that sodium dodecylbenzenesulfonate?SDBS?with a lower concentration could significantly enhance the resonance energy transfer?FRET?from CIP to Eu³⁺in the CIP-Eu³⁺complex,and sensitizing Eu³⁺to emit characteristic fluorescence.This complex system realized sensitive and selective detection of phosphate in 5 min and the LOD?S/N=3?attained 4.3 n M?about 0.13?g/L for P?.This system has been successfully applied to analysis of total phosphorus in water bodies and atmospheric particulates,which also provides a new strategy for designing fluorescent sensing based on FRET mechanism.?3?A ratiometric fluorescent sensing for ultrasensitive and selective detection of Ag⁺based on quantum dots?QDs?hybrid was developed.Nitrogen-and silicon-codoped blue-emitting carbon quantum dots?N,Si-CQDs?were synthesized by one-step hydrothermal method with citric acid and aminopropyltriethoxysilane as raw materials.Red-emitting Cd Te QDs capped by N-acetyl-L-cysteine?NALC-Cd Te QDs?were prepared.The N,Si-CQDs/NALC-Cd Te QDs dual-emission fluorescent sensing was fabricated based on N,Si-CQDs and NALC-Cd Te QDs.The system realized the ratiometric detection of Ag⁺in the range of 5.0–1000.0 n M and the LOD?S/N=3?attained 1.7 n M?about 0.2?g/L?.The assay has been successfully applied to determination of Ag⁺in wastewater with satisfactory results.?4?A dual-emission fluorescent sensing for simultaneous detection of phosphate and Fe³⁺baed on N,S-CQDs and rare-earth ion coordination polymers?Eu-CPs?hybrid was fabricated.A facile,rapid and green method was developed to prepare Eu-CPs at ambient-temperature in aqueous solution.N,S-CQDs/Eu-CPs dual-emission sensing was fabricated by introducing blue-emitting N,S-CQDs.This system can realize simultaneous detection of phosphate and Fe³⁺,and the LOD?S/N=3?is 68.6 n M?about2.1?g/L for P?and 48.3 n M?about 2.7?g/L?,respectively.The assay has been successfully applied to determination of total phosphorus in surface water and human urine.?5?A dual-emission fluorescent sensing for simultaneous detection of nitrite and Hg²⁺based on Tb³⁺-modified CQDs/3-aminophenylboronic acid hybrid?APBA?was developed.Blue-emitting CQDs were prepared by one-step hydrothermal method with nicotinic acid and barbituric acid as raw materials,which can sensitize Tb³⁺to emit characteristic fluorescence.CQDs-Tb³⁺and APBA realized sensitive and selective fluorescence response to nitrite and Hg²⁺in 30 s and 5 min,respectively,and the LOD?S/N=3?for nitrite attained 2.0 n M?about 0.1?g/L?.This sensing system has been successfully applied to nitrite analysis in tap water,groundwater,surface water as well as rainwater,which also provide a new strategy for designing fluorescent sensing for dual or more targets determination.