Preparation Of Fluorescence Enhanced Metal Nanoclusters And Their Sensing Applications

Fluorescent metal nanoclusters are widely applied in optical fields such as chemical sensing,bio-imaging,and light-emitting devices because of their large Stokes shift,easy optical regulation,good water-solubility,and biocompatibility.However,compared to traditional fluorescent materials such as organic dyes and quantum dots,most of the prepared metal nanoclusters are not competitive in terms of fluorescence quantum yield and stability,which seriously limits their practical application in the optical field.Therefore,aiming at the above problems,the fluorescence properties of metal nanoclusters have been improved by aggregation-induced emission effect and confinement induced emission enhancement effect,respectively.On this basis,the application of MNCs was fully developed and expanded,and a series of fluorescence sensing platforms were constructed to realize the sensitive detection of small molecules and biological enzymes.The specific research contents include:1.Negatively charged copper nanoclusters（CuNCs）were adsorbed and aggregated onto the surface of melamine formaldehyde（MF）microspheres（MF@CuNCs）by electrostatic interaction,successfully increasing the fluorescence quantum yield from 0.14%to 8.93%and overcoming the shortcoming of poor stability of CuNCs.Based on this,an enzyme-free sensing platform for methyl parathion was established.Under alkaline conditions,p-nitrophenol can be produced by methyl parathion hydrolysis,and the fluorescence of MF@CuNCs can be quenched by p-nitrophenol through electron transfer.Therefore,the enzyme-free detection of methyl parathion was realized.Combined with a smartphone,fast visual analysis of methyl parathion was realized.The sensing platform was further applied to the determination of methyl parathion in real samples such as vegetables,fruits,and soil,and satisfactory results were obtained.2.The fluorescence quantum yield of CuNCs was further increased to 9.25%and the stability was also improved greatly by the spatial confinement effect of porous zirconium dioxide（ZrO₂@CuNCs）.Based on this,a three-mode sensing platform for metoprolol tartrate was established.The fluorescence and colorimetric detection of metoprolol tartrate was realized by the internal filter effect and dynamic quenching effect between ZrO₂@Cu NCS and Au NPs,as well as the aggregation and fading effect of Au NPs induced by metoprolol tartrate.In addition,a portable sensing platform for metoprolol tartrate was constructed through the combination of a dark box produced by a 3D printer and a smartphone.This work constructed a multimode optical and portable metoprolol tartrate sensor,which provides a new method for drug monitoring in the treatment of cardiovascular diseases.3.Gold nanoclusters（AuNCs）with higher stability were prepared and the fluorescence quantum yield was successfully enhanced to 11.50%by Ce³⁺-triggered aggregation-induced emission effect of AuNCs（Ce@AuNCs）.Based on this,the fluorescence and colorimetric dual-mode sensing ofα-glucosidase（α-Glu）was realized.The fluorescence of Ce@AuNCs can be quenched by 2,6-dichloroindophenol（DCIP）through the internal filtration effect and dynamic quenching effect.α-Glu can catalyzes the hydrolysis of L-ascorbic acid-2-O-α-D-glucopyranosyl to produce ascorbic acid,which can reduce DCIP and cause its discoloration and then recover the fluorescence of Ce@AuNCs.Thus,the fluorescence and colorimetric dual-mode sensing ofα-Glu was realized.This method was further applied to evaluate the inhibiting capacity of naturalα-Glu inhibitors,including luteolin,apigenin,and hesperidin.The multi-mode optical sensor designed in this chapter has the potential for accurate discovery of natural anti-diabetes drugs and the therapy of diabetes.4.AuNCs were successfully encapsulated into melamine-formaldehyde polymer nanoparticles（AuNCs-MF PNPs）,and the fluorescence quantum yield was further significantly increased to 36.90%by the confinement effect.Based on this,ratiometric fluorescence sensing of H₂S was achieved.H₂S can decrease the ratio of Au（I）/Au（0）in AuNCs,thus quenching the fluorescence of AuNCs-MF PNPs.By mixing AuNCs-MF PNPs as signal indicator and CDs as internal reference,a ratiometric fluorescence sensing platform for H₂S with self-calibration capability was established.In addition,solid-state powders of AuNCs-MF PNPs with high fluorescence intensity were further applied to prepare light-emitting diode with favorable characteristics,which may enhance the competitiveness of AuNCs in the field of intelligent luminescence.