A multifunctional upconversion nanoparticles probe for Cu^(2+)sensing and pattern recognition of biothiols

Lanthanide-doped upconversion nanoparticles(Ln-UCNPs)are a new type of nanomaterials with excellent fluorescence properties,which are well applied in fluorescent biosensing.Herein we developed a multifunctional probe based on the surface engineering of core-shell structure UCNPs with polyacrylic acid(PAA).The developed PAA/UCNPs probe could be highly selective to detect and respond to Cu^(2+) at different pH.Cu^(2+) could easily combine with the carboxylate anion of PAA to quench the fluorescence of UCNPs.Therefore,we creatively proposed a fluorescent array sensor(PAA/UCNPs-Cu^(2+)),in which the same material acted as the sensing element by coupled with pH regulation for pattern recognition of 5 thiols.It could also easily identify the chiral enantiomer of cystine(L-Cys-and D-Cys),and distinguish their mixed samples with different concentrations,and more importantly,it could be combined with urine samples to detect actual level of homocysteine(Hcys)to provide a new solution for judging whether the human body suffers from homocystinuria.

Fabricating UCNPs-AuNPs Fluorescent Probe for Sensitive Sensing Thiamphenicol

A novel fluorescent probe has been constructed based on fluorescence resonance energy transfer(FRET)between upconversion nanomaterials(UCNPs)NaYF4:Yb,Er and gold nanoparticles(AuNPs).The fluorescent“off-on”switching was formed for the detection of thiamphenicol(TAP)in egg samples.The fluorescence of UCNPs can be quenched to a certain degree by AuNPs.After adding TAP,the AuNPs generated aggregation and the fluorescence of UCNPs was recovered.The synthesized amination UCNPs and AuNPs were characterized by Fourier transform infrared spectroscopy(FTIR),UV-Vis,X-ray diffraction(XRD),energy dispersive spectrometer(EDS),and transmission electron microscope(TEM)techniques for observation and confirmation.As a model target,the detection of TAP has two linear ranges in the buffer solution within 0.01–0.1µmol/L and 0.1–1µmol/L using this fluorescent probe.The detection limit was obtained to be 0.003µmol/L(S/N=3),which is favorable for trace analysis.The recovery of TAP from 98.2%to 105.3%was obtained,and the relative standard deviation(RSD)was from 2.5%to 4.3%.Furthermore,the method established in this study based on the UCNPs auto-low background fluorescence has high selectivity and strong ability to eliminate interference,which is beneficial to analyzing complex samples.