Research And Application Of Photoelectrochemical Aptamer Sensor Based On Functional Nanomaterials

Photoelectrochemical（PEC）detection is a promising detection technology and has attracted wide attention.It is suitable for the high-throughput analysis.In addition,PEC has a lower background signal,because the energy forms of the input and output signals are different.Due to the specific bioaffinity of biomolecules,PEC biosensors are widely considered as a novel and effective bioanalytical method.So far,PEC technology has been applied in many fields,such as food testing,water quality detecting and clinical diagnosis.The detected targets include small molecules and large proteins.The photosensitive materials are very important for the PEC detection.In this paper,inorganic and organic nanomaterials are combined to construct a PEC sensor.The main work contents are as follows:1.Firstly,silver sulfide（Ag₂S）and organic polymer-polydopamine（PDA）nanocomposites were modified on titanium dioxide nanotubes（TiO₂NTs）.Based on this,the DNA aptamers were immobilized on the electrode to identify the target and the PEC aptamer sensor was constructed.The novel PEC aptamer sensor was firstly used to detect ofloxacin（OFL）.The ascorbic acid（AA）was as a provider of electron holes that could be supplied to photogenerated holes and as a reducing agent at a low concentration,so AA was used as an electron donor for the entire system in this experiment.Secondly,the conduction band of Ag₂S is higher than that of TiO₂NTs,which could facilitate the transfer of electrons from the conduction band of TiO₂NTs to the Ag₂S and then to the surface of the electrode.And polydopamine possessed higher LUMO and HOMO levels,which could further accelerate the separation of electron-hole pairs,improve the electron conductivity rate and finally increase the photocurrent signal.The OFL aptamer was immobilized on the electrode by Michael addition with PDA.Under optimal conditions,the designed photoelectrochemical sensor showed a linear photocurrent response to OFL in the concentration range of5.0 pM-100 nM with a low detection limit（3S/N）of 0.75 pM.And the photocurrent response was proportional to the logarithm of the OFL concentration,and the linear range was wide.The PEC aptamer sensor realized photoelectrochemical detection of OFL for the first time.And there were many advantages such as wide linear range,low detection limit,high sensitivity,good stability and specificity,which was expected to be used for detection of complex foods and water samples.2.The PEC detected platform was constructed by the composite materials of WS₂ and Bi₂S₃.The DNA aptamer double chains were immobilized on the electrode by chitosan,and the Rhodamine B（RhB）was fixed on the electrod which achieved further amplificated.The PEC aptamer sensor realized the quantitative detection of ampicillin（AMP）.In this process,WS₂ was immobilized on ITO by electrophoretic deposition technology.And then the Bi₂S₃ was fixed on the electrode by layer ion adsorption（SILAR）.The modification of Bi₂S₃ greatly increased the absorption of visible light,accelerated electron-hole separation,and increased the electron transfer rate,thereby significantly increased the photocurrent.The PEC aptamer sensor had lower detection with 0.05 pM and had a wide linear range of 0.1 pM to 50 nM.The PEC aptamer sensor had many advantages of high sensitivity,good stability and strong specificity,which provided a powerful method for the detection of AMP.