The Applications Of Photoelectrochemical Technique In The Detection Of Alcohol Concentration In Liquor And Cobalt Ion And Sulfur Ion In Drinking Water

Photoelectrochemical?PEC?analysis has the advantages of high sensitivity,fast response,simple equipment,and easy miniaturization.Thus,PEC attracted wide attention in the field of food safety.Selecting appropriate PEC materials is crucial for the fabrication of PEC sensors with high performance.In this paper,WO₃ and AgI are chosen as PEC semiconductors.Due to the excellent electroconductivity and surface plasmon resonance?SPR?effect,AuNPs are used to improve the electron-hole pair separation efficiency of both WO₃ and AgI,thus improve their PEC performance.Taking these into consideration,PEC sensors on the basis of VAP-WO₃/AuNPs/FTO and AgI/AuNPs/FTO were fabricated for fast and sensitive detection of ethanol and sulfur ions,respectively.In addition,due to the good hole-consuming and strong chelating ability of CS,the CS/WO₃/FTO was fabricated for PEC sensing of Co?II?in tap water.The main research contents of this paper include:?1?Vertically aligned plate-like tungsten trioxide?VAP-WO₃?sensitized with gold nanoparticles?AuNPs?is applied for non-enzymatic PEC sensing of ethanol in liquors.For the fabrication of the novel ethanol sensor,AuNPs were electrodeposited onto fluorine-doped tinoxide?FTO?,and,subsequently,VAP-WO₃ was hydrothermally grown on the AuNPs/FTO surface.Owing to the SPR effect,as well as the good conductivity of the AuNPs,the efficiency of the light absorption and the photoelectron–hole separation of VAP-WO₃ were greatly improved,resulting in a significant enhancement in the VAP-WO₃/AuNPs/FTO photocurrent.Interestingly,ethanol functioned as a sacrificial agent leading to further amplification of the PEC signal on the VAP-WO₃/AuNPs/FTO electrode.Inspired by this phenomenon,a sensitive and non-enzymatic PEC platform was constructed for monitoring ethanol in the range of 1.0–1000?mol L^-1 with a detection limit of 0.5?mol L^-1,which is comparable with those obtained by the enzymatic ethanol sensors.?2?Chitosan?CS?is applied as an efficient hole-scavenger that enhances the photoelectrochemical?PEC?properties of tungsten trioxide?WO₃?for Co?II?detection in water.Decoration of WO₃/FTO electrodes with CS remarkably improves the visible light absorption and enhances the photo electron–hole separation efficiency of WO₃,giving rise to significant photocurrent enhancement.Moreover,by taking the advantage of the strong chelating ability of CS,Co?II?can be extracted effectively from water by using the CS/WO₃/FTO material.The introduction of Co?II?prevents CS from consuming the oxidative holes,resulting in a decrease of the photocurrent.Enlightened by this,we developed a sensitive and selective PEC method for tracing of Co?II?in the range of 1.0 to 60.0?mol L^–1,with a detection limit of 0.3?mol L^-1.?3?Construction of an AuNPs-sensitized AgI(K_sp=8.3×10^-17)PEC sensor for the determination of sulfur ion(S^2-).Due to the substitution reaction between AgI and S^2-,a more stable Ag₂S(K_sp=6.3×10^-50)is formed on the surface of the electrode.Based on results,the ultraviolet-visible absorption peak of Ag₂S/FTO is red-shifted,and more importantly,the absorbance on Ag₂S/FTO is stronger than that on AgI/FTO,thereby increasing the photocurrent of the electrode.Since the AuNPs deposited on the surface of the FTO would change the direction of the AgI photocurrent,the sensitivity of the PEC sensor for detecting S^2-is further improved.According to the results,the photocurrent has a good linear relationship with the concentration of S^2-in the range of 0.2⁵.0 and5.0⁵0?mol L^-1,and the detection limit was 0.08?mol L^-1.Additionally,the sensor was used for the recovery test of S^2-in tap water with good accuracy.