Fabrication Of DYE-NaYF₄:Yb,Er:Yb,Er Nanohybrid For Upconversion Luminescent Detection

Dye-upconversion nanoparticle（UCNP）is a new type of energy coupling system.As probes,dye-UCNP system has the advantages of high light penetration depth,high signal-to-noise ratio and zero background interference,playing an important role in biological imaging,fluorescence detection and photogenetics.Due to high signal-to-noise ratio of more than 100,dye-UCNP system with energy transfer from dye to UCNP has attracted more and more attention from researchers.However,photostability of the system is inferior,and microscopic mechanism of photobleaching is not clear.Fluorescent detection of living tissue is still a qualitative judgment and quantitative study is difficult.Although the sensitivity is high,the relationship between ensemble and single nanoparticle in the dye-UCNP system is not clear.To solve these problems,Na YF₄:Yb,Er UCNPs of hexagonal phase were made to propel the following three aspects:The IR806-Na YF₄:Yb,Er energy coupling system was constructed based on the coordination between carboxyl groups of organic dyes and orbital of rare-earth ions.It was confirmed that IR806 can transfer energy to oxygen molecule and generate singlet oxygen after photon absorption and intersystem crossing under the excitation of 808 nm laser.Singlet oxygen with strong eletrophilicity reacts easily with the excited IR806molecule,which destroys its structure and leads to photobleaching.As a singlet oxygen quenching agent,the addition of?-carotene can effectively reduce the concentration of singlet oxygen,thus increasing the photostability of IR806-Na YF₄:Yb,Er energy coupling system,and the photochemical reaction degree can be reduced from 41%to 12%（at 18min）.Meanwhile,the upconversion luminescence of the composite system was increased by 3.0～6.3 times.In order to avoid photobleaching,combinational screen was used to achieve IR820molecules,only responsive to hydroxyl radical and superoxide anion.The IR820-Na YF₄:Yb,Er@Na YF₄:Yb energy coupling system was constructed by hydrophobic interaction between the amphiphilic molecules（DSPE-PEG 2000）,oleic acid molecules on the surface of UCNP and IR820 molecules.By regulating the density of hydrophobic layers on the surface of UCNP,a composite system with specific response only to hydroxyl radical was obtained.Via fenton reaction,the highly sensitive detection of hydrogen peroxide was achieved.The probes can detect hydrogen peroxide in the range of 0.5 to 100 nmol/L,with detection limit of 0.1 nmol/L and detection time of 5 min.Meanwhile,the probes show good optical stability and repeatability（RSD=1.44%）.Finally,we combined the optical probes with intervention medical devices,quantitative detection of hydrogen peroxide in serum samples and ascites tumor in mice were achieved,realizing quantitative detection in deep animal tissues.The BHQ1-DNAzyme-Na YF₄:Yb,Er energy coupling system with specific response to copper ions was constructed by active chemical modification.Due to the bridging effect of DNAzyme,the energy transfer from the ⁴S_3/2 energy level of Er³⁺to the excited energy level of BHQ1 was realized.The energy transfer process included both non-radiative energy transfer（56%）and internal filtering effect（34%）.Via the specific recognition and breakage of DNAzyme,the highly sensitive detection of copper ions was realized,with detection range of 5 to 500 nmol/L,detection limit of 1.5 nmol/L,and detection time of 20 min.At the same time,the optical stability（within 3%）and repeatability（RSD=3.22%）of the system are favourable,showing no obvious responses to other metal ions.Finally,the microcosmic process of copper ions detection was studied at the single particle level,revealing the random microcosmic change of copper ion detection reaction and the energy transfer between UCNPs and dyes at the single particle level.The signal-to-noise ratio is up to 7200,so the detection sensitivity is greatly improved with detection limit of 220 pmol/L.