Guyan Reagent-New prototype device for rapid detection of PCB

Polychlorinated biphenyls (PCBs) are a typical type of persistent organic pollutants (POPs). Due to the bio-enrichment and high toxicity of PCBs, such chemical products that once played a huge role also caused great harm to humans and the ecological environment. Dr. Yajun Yang, Institute of Solid State Physics, Hefei Academy of Material Sciences, Chinese Academy of Sciences, used the surface of silver nanodendrites to enhance the Raman scattering effect to achieve rapid and trace detection of tetrachlorobiphenyl. Recently, postdoctoral researcher Li Mingtao of the Institute collaborated with researcher Meng Guowen, associate researcher Yin Zhijun and researcher Huang Qing of the Institute of Plasma, inventing a new surface photovoltage sensor that can quickly detect PCBs.

Zinc oxide semiconductor porous materials will cause their own surface photovoltage (SPV) changes before and after adsorbing PCBs. The analysis shows that under the irradiation of sub-band gap monochromatic light, the transition of surface state electrons causes the change of the surface potential, resulting in SPV. PCBs adsorbed on the surface of zinc oxide can affect the transition of surface state electrons, resulting in changes in SPV. For example, under the illumination of 500 nm monochromatic light, the SPV signal of the sensor will decrease after adsorbing PCBs; and the magnitude of SPV decrease is related to the amount of PCBs adsorbed, and there is a linear relationship between the two within a certain range. In this way, the content of PCBs can be quickly detected by simply measuring the change in surface photovoltage.

Based on the above principles, the newly developed sensor has a very simple structure, consisting of two sheets of conductive glass and a thin layer of porous zinc oxide powder sandwiched between them (Figure A). There is a small round hole in the middle of the conductive glass on the side of the illuminated surface, which is the channel for PCBs to enter the zinc oxide powder layer. The SPV is measured by a lock-in amplifier connected to conductive glass. The system has high sensitivity and can detect weak SPV signal changes. The reason why porous zinc oxide powder is used is to enhance the enrichment of PCBs, thereby improving the detection sensitivity. Because the sensor can obtain a stable SPV signal within a few seconds after illumination (Figure B), it has a shorter analysis time and is expected to be used for rapid detection of PCBs.

The current common method for detecting PCBs is the combined detection technology based on chromatography and mass spectrometry. However, these detection methods are not only complicated, time-consuming, and costly, making it difficult to monitor online trace PCBs in real time. The researchers used newly developed sensors to test two PCBs, PCB29 and PC101, and found that their detection sensitivity can reach 10-6 M, and the analysis time does not exceed one minute. This provides a new way to build sensors for rapid detection of PCBs (even other POPs), and has important reference value for rapid trace detection of POPs in the environment.