| In recent years, the morbidity of diabetes increase rapidly. More and morepeople are under the threat of diabetes. Every day, there is millions of diabetespatients need to measure the level of blood glucose. Moreover, Glucose biosensorhas been widely applicated in the field of clinical detection, biological analysis,environmental monitor and food industry. Such a huge market demand speed up thedevelopment of the glucose sensor, at the same time, it puts forward higherrequirements on glucose sensor: higher sensitivity and lower detection limit, betterstability and stronger anti-jamming ability. Electrochemical glucose sensor hasadvantages of low cost, simple manufacturing process and fast response. However, ithas some disadvantages, such as low sensitivity, slow response, poor stability andweak anti-interference ability, which prompted the researchers to develop newglucose sensor with higher performance.In order to get high-performance glucose sensor, we have the innovation andbreakthrough from two aspects of test methods and electrode materials on the basisof the existing electrochemical glucose sensor. On the one hand,photoelectrochemical testing method has been used for the detection of glucose. Onthe other hand, metal oxide nanomaterials photonic crystal was selected as electrodematerials. Photoelectrochemical sensor has the dual advantages of fluorescent andelectrochemical sensing, which has great application potential. Photoelectrochemicalsensor realized the separation of the excitation signal and the detection signal, whichgreatly reduced background noise of the sensors and improved the performance ofthe sensor. Photoelectrochemical glucose sensor added external excitation light source on the basis of the electrochemical glucose sensor, which absorbs the energyof the incident light and produce light carrier by the electrode material hasphotoelectric conversion characteristic of itself or the material with the photoelectricproperties modified on surface of the electrode. The photon-generated carriertransferred from valence to the conduction band provided a large number of freeelectrons for the redox reaction of glucose and formed the photocurrent, whichincrease the strength of forward current, at the same time suppress the reversecomposite of electrons and holes and improve the performance of glucose sensor.The key to building a photoelectrochemical biosensor problem lies in the selection ofelectrode materials and preparation.Among numerous nanometer materials, metal oxide nanometer material, whichhas excellent optical and electrical properties and good photoelectric properties, isone of the most ideal electrode materials of photoelectrochemical biosensor, and italso has a great application prospect in the field of biological sensing.Metal oxide inverse opal photonic crystal structure is highly orderedmacroporous nanomaterials, which has a larger specific surface area and uniformpore distribution. The larger specific surface area makes the electrodes and theelectrolyte contact more adequately, which provides more sites for the bio-materials.The three-dimensional ordered macroporous structure is beneficial for electrontransmission and the diffusion and adsorption of biological molecules inside theelectrode, reduced the diffusion distance of electrons from the electrode substrate tothe redox center of the adsorption of biomolecules, thus improve the transmissioncapacity of electronic. Moreover, slow light effects due to photonic crystals withmultiple scattering effect can enhance interaction between light and photoconductivesemiconductor materials, effectively improve the light absorption, make the photoniccrystal materials shows better photocatalytic activity, so the photoelectric controleffect can be realized based on photonic crystals of photoelectrochemical responseeffectively.In this paper, we prepared two kinds of metal oxide inverse opal photonic crystal electrode, and realized photoelectrochemical sensor for glucose. The mainresearch results are as follows:(1) Zinc oxide and copper oxide inverse opal photonic crystals electrodes wereprepared by self-assembly PMMA colloidal crystal template combined with sol-gelmethod, which has highly ordered macroporous structure and photonic band gap canbe controlled. We studied how the photonic band gap position influenced lightabsorption and the performance of glucose sensor, and slow light effect of photoniccrystal was observed in the experiment.(2) The choice of the precursor material, ratio of ethanol and water, the choice ofthe clathrate, amount of various material in response, reaction temperature, pH valueand other factors had been carefully researched, when metal oxide precursor solutionwas made by sol-gel method.(3) In order to further improve the performance of the sensor, electrodes should bemodified by functionalized material. Chloroauric acid solution infiltrated the surfaceof prepared ZnO IOPCs, and Au nanoparticles were synthesized on the skeleton ofinverse opal photonic crystals after annealing. Through the research of differentconcentration of chloroauric acid and the temperature of annealing, we found thatelectrodes kept good inverse opal structure and modified by the uniformmonodisperse Au nanoparticles when the concentration of chloroauric acid was50mM and the temperature of annealin was500℃. In order to improve the sensingperformance of the CuO IOPCs/FTO electrode, cadmium sulfide quantum dotswere modified with continuous ion adsorption reaction (SILAR) in the surface ofCuO IOPCs. Through the research of different concentration of ion concentration inSILAR reaction and reaction time, we found that electrodes kept good inverse opalstructure and modified by5nm cadmium sulfide quantum dots when theconcentration of ion was50mM and reaction time was1min.(4) Glucose oxidase and Nafion were modified on the surface of ZnO IOPCs, then anew Nafion/GOD/ZnO IOPCs/FTO electrodes were fabricated and theirphotoelectrochemical biosensing properties were carefully studied. ZnO IOPCs was firstly applied in photoelectrochemical detecting for glucose. The influence of someparameters of the photonic crystals, such as aperture size and film thickness, wasfurther studied on the sensing performance. At the same time, the mechanism and thespecific process of redox reaction were analyzed, and researched on the dynamicprocess of electron transfer. In addition, slow light effects and multiple scatteringeffects of photonic crystals were also studied. The results demonstrated that thesensitivity of Nafion/GOD/ZnO IOPCs/FTO electrode was18times than thatwith the same quality of Nafion/GOD/ZnO thin film/FTO electrode, due to theporous structure of IOPCs with a large surface area. For photoelectrochemicaldetection, the sensitivity of Nafion/GOD/ZnO IOPCs/FTO electrodewas reachedup to52.4μA mM-1cm-2, which was almost4times to the result of electrochemicaldetection (14.1μA mM-1cm-2). We believed that the electrode sensitivityenhancement could be attributed to slow light effects and multiple scattering effectproduced by the inverse opal photonic crystal structure.(5) CdS quantum dots were modified on the surface of CuO IOPCs by ionic layeradsorption and reaction (SILAR). Then the CdS-QDs/CuO IOPCs/FTO electrodewas fabricated and their photoelectrochemical biosensing properties were carefullystudied. The sensitivity of CuO IOPCs electrode was4065μA mM-1cm-2, which wasgreater than the referenced CuO thin film electrode due to the large surface area anda uniform porous distribution of structure of IOPCs. CuO mainly absorbs infraredlight as a narrow-band semiconductor. In order to obtain visible light absorption andbetter photoelectrochemical properties, we further modified the CuO IOPCs byincorporating cadmium sulfide (CdS) quantum dots (QDs) on the electrode surface.With a band gap of around2.4eV, which matches well with the visible spectralrange of solar irradiation, CdS exhibits excellent photocatalytic activity because ofits highly effective absorption of solar energy. The results demonstrated that thethickness of CdS–QDs on the surface of electrode was5nm after three SILARcycles, and the electrode had the best sensitivity for glucose, which was4345μAmM-1cm-2. There are two reasons for the enhancement of sensitivity. On the onehand, cadmium sulfide quantum dots improve the absorption of incident light. Onthe other hand, cadmium sulfide quantum dots inhibit the reverse composite of electrons and holes. |
PDF Full Text Request