Preparation Of CePO₄:Tb Nanorods And Application In Detecting Phosphatase

Alkaline phosphatase（ALP）,an essential biological enzyme in catalyzing the dephosphorylation process of proteins,nucleic acids,and small molecules,widely exists in mammalian body fluids and tissues.The overexpressed level of serum ALP is associated with various diseases,such as adynamic bone disease,diabetes,prostatic cancer,and liver dysfunction etc.Thus,ALP is one of the most extensively assayed enzymes in clinical practice.Up to now,several strategies have been established for the detection of ALP,such as colorimetry,electrochemistry,surface-enhanced Raman scattering,fluorescence and so on.However,most of these methods face some defects,including need for complex modification process,easy to be disturbed by external conditions,insensitive detection and narrow detection linear range etc,which limit the widespread use.Thus,it is of great significance to develop simple,rapid,label-free,highly sensitive and selective methods for ALP detection.Rare earth phosphate nanoparticles have good development prospects in the field of biosensing because of their unique optical properties such as long lifetime,high quantum yield,low photobleaching,low toxicity,and high chemical stability etc.In this paper,a rare earth luminescent nanomaterial-CePO₄:Tb nanorod was synthesized and used for the detection of alkaline phosphatase.This thesis mainly includes the following contents:1.Rare earth luminescent nanomaterial is prepared using a simple,gentle method.The TEM image of rare earth luminescent nanomaterial shows that rare earth luminescent nanomaterial is nanorod with a diameter of about 5-7 nm and a length of50-80 nm.The optical properties of CePO₄:Tb nanorods is inspected by fluorescence spectra.The result show that CePO₄:Tb nanorods have good luminescent properties and exhibit the characteristic emission bands of Tb³⁺at 494,548,590,and 624 nm,which are ascribed to the 4f-4f transitions of ⁵D₄→⁷F₆,⁵D₄→⁷F₅,⁵D₄→⁷F₄,and⁵D₄→⁷F₃,respectively.There is no perceptible shift of the maximum emission peak at excitation range from 240 to 290 nm,with the maximum emission obtained at 270nm excitation.2.There are abundant carboxyl groups on the surface of AuNPs which reduced by citric acid.AuNPs can assemble onto the surface of CePO₄:Tb through the coordination of CePO₄:Tb with the carboxyl groups of AuNPs,resulting in the fluorescence of CePO₄:Tb quenching.When pyrophosphate（PPi）is introduced,due to the stronger affinity of PPi to CePO₄:Tb than that of AuNPs,leading to the disassembly of AuNPs and CePO₄:Tb and the fluorescence of CePO₄:Tb recovery.In the presence of ALP,PPi can be hydrolyzed into Pi,then AuNPs and CePO₄:Tb reform to the assembly,leading to the fluorescence quenching again.Based on this,this paper proposes a new method for rap id,sensitive and label-free detection of ALP by using the preparation of CePO₄:Tb nanorods as fluorescent probes.