Probing The Interaction Between Ag₂S QDs And HSA As Well As PH Sensor Preparation By Fluorescence Spectroscopy

As a new excellent near infrared fluorescent nanomaterial,Silver sulfide quantum dots?Ag₂S QDs?with distinct optical properties and low biological toxicity has been widely used in cell imaging and biodetection in recent years.But the interaction of Ag₂S QDs and protein remain to be elucidated.And the preparation of ratiometric fluorescence sensor based on Ag2S QDs is still relatively rare.Therefore,this paper adopted a convenient rapid method to synthesis water-soluble Ag₂S QDs and explored its interaction with human serum albumin?HSA?,which was used to construct the ratio fluorescent probe for detecting pH.Concrete research contents were as follows:1.The water soluble Ag₂S QDs were synthesized through a one-step synthetic method.By investigation the interaction of quantum dots and HSA,it was found that with increasing the concentrations of Ag₂S QDs,the fluorescence intensity of HSA gradually decreased,while their fluorescence lifetime did not change.This phenomenon demonstrated that the fluorescence quenching model of the HSA by Ag₂S QDs was static quenching.By calculating the kinetic constant,it indicated that their interaction was mainly attributed to electrostatic interaction.This study confirmed that the Ag₂S QDs was a good fluorescence quenching agent for the protein similar with HSA,and it should have the potential application for the design of a ratio fluorescent probe.2.The ratio fluorescence probe was constructed via the electrostatically adsorption of the negatively charged Ag₂S QDs with the positively charged carbon dots?CDs?.By means of transmission electron microscope?TEM?,X-ray photoelectron spectroscopy?XPS?,Fourier transform infrared spectroscopy?FT-IR?,etc.,the particle size,structure,surface function group and water solubility of the probe were characterized.The accumulation of Ag₂S-CDs caused by the protonation of carboxylic group under acidic conditions led to the fluorescence enhancement of the Ag₂S QDs,which could be further used to detect the pH.When pH changing between 5.4 and 6.8,I₅₀₀/I₆₇₀ was in linear correlation with pH.The linear equation is I₅₀₀/I₆₇₀=-3.40+0.83pH,and the correlation coefficient is 0.997.When the pH was alternated between 5and 7,the fluorescence intensity of Ag₂S-CDs show a great reversibility.Therefor,it is promising to be further applied in biological systems.