Cu²⁺Fluorescent Probes Based On Rhodamine B Derivatives And Synthesis Of Immobilized Fluorescent Probe

As one of most common transition-metal ions,Cu2+ is one of the highly toxic and global widespread pollutants.As the third most abundant transition metal in the human body,Cu2+ plays a vital role in many biological processes,such as the absorption of iron,the redox process of mitochondrial respiration and a large number of enzymes(including superoxide dismutase,cytochrome c oxidase and tyrosine,etc.)as a catalytic cofactor.Some reports showed that excessive levels of Cu2+ accumulate could induce severe diseases to living body.Hence,there remained a significant challenge for development of rapid detection and removal of copper from pollutants.Recently,the hydrogen sulfide(H2S)has proved as a novel gasotransmitter,and exhibited important physiological function like nitric oxide(NO),carbon monoxide(CO)in animal systems.The protonated forms of sulfur,such as HS-or H2S are more toxic than sulfide.If mammal drinks the water contaminated with sulfide,it will damage mucous membranes and cause respiratory problem.Therefore,development of a quick and sensitive method for immediate sulfide detection in aqueous media is of high interest.Recently,rhodamine B-based dyes have been widely used as fluorescence reporting groups due to their excellent spectroscopic properties,such as large molar extinction coefficient,high fluorescence quantum yields,long absorption and emission wavelength.The sensing mechanisms of these chemosensors probes are mainly based on the structure changes of spirocyclic towards its open-cycle forms.On the grounds of these strategies,we designed a novel rhodamine B moiety of L as a"turn-on" fluorescent probe for Cu2+ sensing in aqueous solution.In the absent of Cu2+ ions,the L exists in spirocyclic form,which is colorless with weak fluorescent intensity.Upton addition of Cu2+ ion into L,the spirocycle structure opened and the solution showed clear pink color,which also generated a fluorescence enhancement response.Additionally,high selectivity toward Cu2+ion over other metal ions was clearly observed.Meanwhile,we also found L-Cu2+ complex can be employed to detect sulfide.By adding sulfide to the solution of L-Cu2+ complex,the color of the aqueous change from pink to colorless.In the further study,we synthesized a rhodamine B-based receptor and immobilized it on the surface of magnetic F3O4@SiO2 silica nanoparticles as a new approach to the development of a chemosensor for the detection and removal of Cu2+.