关键词: 阴极光电流, Zr-MOFs, 同型半胱氨酸

Abstract:

Due to the independent form of the light source and detection system, photoelectrochemical (PEC) sensor has the advantages of low background, high sensitivity and simple operation. So far, PEC systems have been widely used in the fields including the actual detection of metal ions, biological antibodies or antigens in environmental pollutants. When the photosensitive material is irradiated by a light source with an energy being equal to or greater than its band gap, electrons (e^-) transition occurs from the valence band to the conduction band, leaving a hole (h⁺), at the same time, the generated electron-hole pair (e^-/h⁺) separate, and migrate to the electrode surface and electrolyte to generate photocurrent or photovoltage. When the target analyte is added, it will interact with its recognition molecule, and affect the separation or migration process of the charge, thereby, causing a change in the photocurrent. Metal organic framework (MOF) is a material composed of metal ions and organic linking groups. They have adjustable porosity, functional surface and massive conjugate back bone. These unique characteristics of MOF have been extensively explored in various fields. Zr-MOFs were synthesized use 4-carboxyphenylporphyrin (TCPP) as the ligand, and metal zirconium (Zr) as the coordination metal. Using Zr-MOFs as the photoelectrically active material, a cathode photoelectrochemical sensor was constructed to detect homocysteine (Hcy). A three-electrode system, consisting of Zr-MOFs/FTO electrode, Pt electrode and Ag/AgCl electrode, was inserted into 0.01 mol·L^-1 HEPES solution to prepare the sensor. An aqueous solution of homocysteine was added to the electrolyte, allowing it to stand for 5 min. Cyclic voltammetry and electrochemical impedance spectroscopy were used to characterize the reaction process and the electron transfer process between optoelectronic materials. When the Xe lamp with λ > 420 nm is used to irradiate Zr-MOFs, electrons (e ^-) in the valence band transfer to the conduction band, and holes (h⁺) are generated in the valence band, thereby, generating light current. The addition of homocysteine will hinder the transfer of electrons, causing the cathode photocurrent to be decreased. The prepared sensor had good linear responses in the ranges of 10 ~ 100 nmol·L^-1 and 100 ~ 1000 nmol·L^-1, and the detection limit was 2.17 nmol·L^-1. The sensor also exhibited good stability and selectivity. The prepared cathode photoelectric sensor could sensitively and efficiently detect homocysteine in milk. The studied high-performance photoelectric active materials and chemical sensing platforms may be important for the design of other chemical sensing platforms and the development of PEC applications.

Key words: cathodic photocurrent, Zr-MOFs, homocysteine