Organic Photoelectrochemical Transistors For BoNT-LCA And E.coli Detection

Organic electrochemical transistors(OECTs)have attracted lots of attentions in chemical and biological sensors due to their obvious advantages,such as easy fabrication,low cost,low operatingvoltage(<1V),flexibility,stability,andbiocompatibility.Organic photoelectrochemical transistor(OPECT),which combines OECT and photoelectrochemical(PEC)sensing technology,has a very high detection sensitivity in the application of biosensor because of the reduced background noise.Therefore,it can be put into the important applications of microorganisms and their secretions detection.In this thesis,we took OPECT sensor as the research object,the detection of botulinum toxin and Escherchia coli(E.coli)by OPECT were mainly studied,as well as the fabrication and sensing application of miniaturized OPECT devices.First,cadmium sulfide quantum dots(CdS QDs)and gold nanoparticles(Au NPs)were successfully synthesized.The sensing technique was designed by using the exciton-plasmon interaction(EPI)effect generated between them.At the same time,the OPECT devices were fabricated and its electrical properties were characterized.By optimizing the test conditions(electron donor concentration,excitation wavelength,etc.),the performance of the device in biosensing was optimized.Then,the OPECT sensorss based on the EPI effect were used for botulinum toxin sensing.The sensor showed the best detection performance for botulinum toxin when the substrate protein with a concentration of 0.8 mg/mL bound with Au NPs for 2 h incubation,and the botulinum toxin interacted with the substrate protein for more than 20 min.The detection limit could reach to 1×10~-1414 g/m L,which was 6 orders of magnitude bettter than that of botulinum toxin sensor based on steric hindrance effect.The sensing mechanism was mainly attributed to the EPI effect between CdS QDs on the OPECT gate electrode and Au NP at the end of the substrate protein,which regulated the interface potential change of the gate electrode.In the same sensing system,the detection limit based on the OPECT botulinum toxin sensor is reduced2 orders of magnitude compared to the conventional PEC sensor,indicating that the higher detection sensitivity of OPECT.Furthermore,the OPECT-based botulinum toxin sensor was also proved to be very selective.The detection of E.coli by OPECT was also studied.The results showed that OPECT had the best detection performance for E.coli and the detection limit is 10~2 cells/m L,when the incubation temperature of E.coli with the antibody was between 25°C and 30°C and the incubation time is more than 1 h.The detection principle is mainly due to the steric hindrance effect of E.coli on the charge transfer on the gate electrode.At the same time,the detection limit of the OPECT-based E.coli sensor is one order of magnitude lower than that of the conventional PEC sensor,which proved that OPECT had a higher detection sensitivity.Moreover,the OPECT-based E.coli sensors were also proved selective.Finally,a miniaturized OPECT device was designed for sensing application.The miniatured OPECT devices were fabricated by using micro-machining technology,and their structures and size were optimized for superior electrical properties.Meanwhile,the application of the miniaturized OPECT devices to the sensing of E.coli was explored preliminarily.The results showed that the E.coli with trace amounts can be detected by the miniaturized OPECT devices.The OPECT sensor can be supposed to have a wide potential application prospect in the field of biosensing,especially in the micro-detection of biomolecules.