Research Hydrazine Photoelectrochemical Hydrogen Peroxide Sensor

Photoelectrochemical (PEC) sensor is a newly emerged analytical technique,which uses light to induce electron transfer between PEC-active species and electrodefor generating the detectable photocurrent signal, which has set the advantages ofphotochemical and electrochemical sensors and has brought a wide and brightapplication prospect in the fields of biology, medicine, environment monitoring andetc. Silicon material has the advantage of good photoelectrochemical performance,environmentally friendly and easy to machining, so it is often used as basal electrode.Hydrogen peroxide (H2O2) is an essential mediator in food, pharmaceutical, clinical,industrial, and environmental analyses. Hydrazine (N2H4) and its derivatives arefrequently found in our environment and are used as essential raw materials and/orintermediates in some industrial or agriculture preparations. Nevertheless, hydrazineis extremely toxic, endanger human body health and environmental safety. So it is ofgreat significance to determine the Hydrogen peroxide and hydrogen.This thesis mainly investigates three kinds of PEC sensors based on siliconwafers. Different metals films of Pt, Ni, Pd were coated onto the front surface ofn-n+-Si wafers in high vacuum evaporating system. They were modified for threedifferent types of electrodes as photoelectric chemical sensors. The modifiedelectrodes have been used for determination of hydrogen peroxide (H2O2) orhydrazine (N2H4) with a two-electrode cell in absence of reference electrode byphotocurrent measurement.The experimental results show that these three PEC sensors for detecting thehydrogen peroxide (H2O2) or hydrazine (N2H4) have good sensor performances.Experimental study includes the following three content:1. N-silicon photo-electrode modified by palladium film for hydrogen peroxideand hydrazine determinationIn this work, a palladium film has been evaporated on an n-silicon surface andelectrochemically activated by cyclic voltammetry (CV) to form a modified silicon photo-electrode. Metallurgical microscopy images and x-ray photoelectronspectroscopy (XPS) were used to characterize the morphology and composition of themodified electrode surface. The electrochemical behaviors of the modified electrodewere investigated by cyclic voltammetry (CV). A photo-electrochemical cell based onthe modified electrode was used as sensor for hydrogen peroxide and hydrazinedetermination by photocurrent measurements. The sensor showed good photocurrentresponses by adding different concentrations of hydrogen peroxide and hydrazinewith a good stability. The linear ranges for the detection of hydrogen peroxide are20to200μM with a detection limit of1.8μM at applied voltage of0.4V in pH=7.0phosphate buffer solution (PBS).The linear ranges for the detection of hydrazine are2to20μM with a detection limit of0.5μM at zero voltage in pH=7.0phosphate buffersolution (PBS).2. Composite palladium-cobalt oxide films modified n-silicon electrode forphotoelectrochemical detection of hydrogen peroxideA novel nonenzymatic hydrogen peroxide (H2O2) sensor was fabricated, basedon composite Pd-Co oxide film modified n-silicon electrode. The modified electrodewas consisted of platinum coated n-silicon as substrate prepared by vacuumevaporating platinum coating layer and composite Pd-Co oxide films deposited byelectrochemical technique. The morphology and composition of the modifiedelectrode were characterized via scanning electron microscope (SEM) and X-rayphotoelectron spectroscopy (XPS), respectively. The analytical performances of themodified electrode for determination of H2O2were investigated by cyclicvoltammetry (CV) and chronoamperometry. A new two electrodesphoto-electrochemical cell has been used as sensor for H2O2determination byphotocurrent measurements at zero voltage. The sensor showed good photocurrentresponses by adding different concentrations of H2O2with a good stability. The linearranges for the detection of H2O2are20to200μM with a detection limit of1.5μM inpH=7.0phosphate buffer solution (PBS). In addition, the sensor also exhibitedsuperior stability, anti-interference and portability. These features demonstrated thatthe new photoelectrochemical sensor was suitable for detection of H2O2on site outdoors.3. Determination of hydrazine based on NiOOH films modified n-siliconphotoelectrodesA novel hydrazine sensor was developed by depositing nickel/platinum doublelayers on an n-silicon electrode (Ni/Pt/n-n+-Si) by vacuum evaporating technique. TheNi/Pt/n-n+-Si was electrochemically activated by cyclic voltammetry (CV) in0.1Mpotassium hydroxide (NaOH) solution. Scanning electron microscope (SEM),metallurgical microscopy images and x-ray photoelectron spectroscopy (XPS) wereused to characterize the morphology and composition of the modified electrodes.Two-electrode cells based on the modified electrodes were used as sensor forhydrazine determination by photocurrent measurements. The sensors showed goodphotocurrent responses by adding different concentrations of hydrazine with a goodstability. The linear ranges for the detection of hydrazine are20to220μM with adetection limit of1.0μM in0.1M NaOH solution using NiOOH/n-n+-Si electrode.This provides a facile way of detecting hydrazine and succeeds in averting from aninconvenient reference electrode.