Electrodeposition And Photoelectrochemistry/electrochemistry Of Amorphous Molybdenum Sulfide-based Materials

Photoelectrochemical?PEC?sensing has been rapidly developed in recent years,which has the advantages of high sensitivity,low background signal and desirable selectivity.To date,PEC sensors have been widely applied in numerous fields such as disease diagnosis,medicine research,food safety and environmental monitoring.Although a series of new PEC sensors with various signal amplification modes have emerged,the low photo-conversion efficiency and weak photocorrosion resistance of the common photoactive species limit the PEC sensing performances.Exploring high-quality photoactive material with efficient visible-light absorption,fast charge transport rate and stability is crucial to developing high-performance PEC sensor.Amorphous molybdenum sulfide?a-MoS_x?,especially electrodeposited ultra-thin film,is a prime candidate of photoactive materials due to high optical transparency and visible light absorption,good stability and biocompatibility,as well as the ease of electrodeposition preparation.Due to the unique properties with isotropic nature and disordered structure,a-MoS_x can offer more active sites and exhibit higher catalytic activity,which is of great important for enhancing PEC sensitivity.However,the charge transfer is still limited by poor crystallinity,which hampers the photocurrent response.An efficient way to overcome this drawback is construction of heterostructures by composing with other semiconducts or loading on the conductive substrates.Rational design of signal amplification strategy can also promote photocurrent of the a-MoS_x-based photoelectrode.In this thesis,a series of a-MoS_x-based photoelectrochemical active materials were prepared by facile and low-cost electrodeposition method.The photoelectrochemical and electrochemical properties of these materials were systematically studied.By rational selecting biorecognition probe and signal amplification mode,several PEC sensors with high sensitivity and selectivity have been constructed.The main contents are described as below:?1?a-MoS_x/RGO hybrid film was directly prepared on ITO via one-step electrodeposition followed by a post annealing process.The as-deposited hybrid film exhibited good uniformity,fast photoelectric switching behavior and robust stability under visible light illumination,which were crucial for developing high-quality photoelectrode for PEC sensing.The a-MoS_x/RGO photoelectrode was directly utilized for glucose determination.Rapid,stable and reproducible detection of glucose in serum samples was realized.?2?High visible-light-actived a-MoS_x@ZnO nanorod arrays was sequentially electrodeposited on ITO substrate,which was used to construct an ultrasensitive self-powered PEC aptasensor with the potential of monitoring trace amount of tobramycin in real sample.The core-shell arrays electrode exhibited three-fold photocurrent of the ZnO nanorod arrays due to combination of a-MoS_x together with favorable energy band alignment.By employing specific aptamer as recognition element,a self-powered PEC aptasensor for ultrasensitive and selective determination of tobramycin was constructed.?3?Hybrid a-MoS_x/carbon dots?CDs?film was prepared via an all-electrochemical approach.Methylene blue?MB?was attached to adenosine aptamer probe via specific interaction,resulting in the formation of co-sensitized structure with a-MoS_x/CDs hybrid film.The photocurrent intensity of the hybrid system was thus enhanced.In this system,CDs cannot only act as an electron transfer relay to facilitate the electron transfer from excited MB to a-MoS_x,but also act as light-scattering centers to increase the light absorption of MB,further improving the sensitization effect.When the adenosine aptamer probe specifically bounded with adenosine,MB adsorbed on the aptamers probe was released from the electrode surface,leading to the decrease of the photocurrent because of the depressed sensitization effect.Accordingly,the target analytes of adenosine molecules could be sensitively and specifically detected.?4?The a-MoS_x/depAu was prepared by electrodepositing Au nanoparticles on the surface of a-MoS_x,which exhibited enhanced photocurrent response and high stability compared with pristine a-MoS_x.The thionine@MoS₂ quantum dots?Th@MoS₂ QDs?was ultilized as signal amplification elements that were labeled on the terminal of the insulin aptamer probe.A conformational change of aptamer was employed to regulate sensitization effect of Th@MoS₂ QDs.In the absence of insulin,the sensitization effect was depressed due to the formation of double helix structure.While insulin existed,the sensitization effect was activated due to the formation of G-quadruplex,and the photocurrent intensity was enhanced.The proposed PEC aptasensor exhibited high sensitity and sesitibity for insulin determination.?5?An advanced three-dimensional porous electrode comprised of a-MoS_x nanosheets with strong adhesion on Ni foam for efficient supercapacitors was fabricated by electrodeposition.The as-prepared a-MoS_x nanosheets possess robust structure,large electroactive surface area,and good conductivity,which are highly demanded by the supercapacitor electrode materials.Owing to these advantageous features,the a-MoS_x/Ni foam electrode exhibited a high specific capacitance of 463F/g at 1 A/g,as well as good cycling stability?87.1%capacitance retention at a high rate of 5 A/g?.