Preparation And Performance Studies Of ZnO-based And Al₂O₃-based Functional Films

Rapid immobilization of chemicals in nano and ionic scales on a two-dimensional surface(glass,conductive glass,plastic and stainless steel)has broad applications and implications for researchers in various areas of chemical biosensors,catalysis,trace analysis,self cleaning and corrosion resistance.It is desirable and practical if functional chemicals can be tailored to attain required properties and to express their functions on a two-dimensional surface.Film,as one form of the two-dimensional surfaces,has received considerable attention due to its unique opitical,electrical,magnetic and mechanical properties.In this work,ZnO based and Al₂O₃ based functional film surfaces have been prepared and their applications have been studied in details.The main contents of this work are summarizied as follows:(1)Unique short submicron wire-like ZnO films were successfully prepared on silicate glass substrates by calcination of spin-coated zinc acetate ethanol solution in the presence of ethanolamine(EA)as structure-directing agent.Ag@Ag Cl particles were deposited on ZnO films by a simple impregnating-precipitation-photoreduction method.The photocatalytic ability of Ag@Ag Cl/ZnO was evaluated by using methylene blue(MB)and methyl orange(MO)as model pollutants under visible light irradiation.The Ag@Ag Cl/ZnO-3 exhibited the best photocatalytic performance and the degradation percentage of MB after 2 h reached 92.9%,while 80.7%of MO was degraded after 4 h.This film photocatalyst was stable and easy to separate from the reaction,and the tests show that the films were reusable for four times without significantly loosing efficiency.Additionally,GC-MS was applied to investigate the intermediates resulted from the photocatalytic degradation of MB and MO under Ag@Ag Cl/ZnO-3.A possible interficial charge transfer photocatalytic mechanism for Ag@Ag Cl/ZnO film was proposed based on the photoelectrochemical measurements and radical trapping experiments.(2)This study presents the first reports for Cu_xO/ZnO sequentially sputtered leading to stable and uniform films effective accelerated degradation of the emerging pollutant sulfamethazine(SMT)under simulated solar light and visible light.The most effective Cu_xO(30 s)/ZnO(4 min)film was sputtered from a Zn-target for 4?min followed by Cu-sputtering for 30?s on polystyrene(PS)petri dish.Cu O was the predominant species in Cu_xO(30 s)/ZnO(4 min)film as confirmed by XRD and XPS.The surface atomic composition of Cu_xO(30 s)/ZnO(4 min)film determined by the XPS peak area was Cu_1.25O(30 s)/ZnO(4 min).The photocatalytic performace of Cu_xO/ZnO film mediated SMT degradation was investigated by the pollutant concentration,intial p H and light intensity.A differentiated plausible iso-energetic charge transfer mechanism was suggested for both under simulated solar light or visible light.(3)A simple sol-gel technique using boehmite as precursors to produce a transparent,chemically robust and nanostructured porous Al₂O₃ layer on conductive glass substrate(PAOCG)was reported.Galvanic replacement reaction was designed for direct growth of GNPs and Ag NPs on PAOCG.This mechanism was further studied by open circuit potential-time(OCP-t)experiment and the result demonstrated that steel induced the continuous proceeding of this reaction.The optimal Au/PAOCG(60 min)SERS substrate allowed as low as 10^-9 M CV and 10^-8 M 4-Mpy to be detected.From the viewpoint of analytical chemistry,EF values for 10^-9 M CV at 1171 cm^-1 and 10^-8 M 4-Mpy at 1095 cm^-1were estimated for 3.4×10⁷ and 4.6×10⁶,respectively.To have a quantitative SERS analysis for CV and 4-Mpy detections,the plots of SERS intensity as a function of logarithmic concentration of the target molecule were fitted.The regeneration of the used Au/PAOCG was achieved by simple heat treatment,and the intensities of characteristic peaks for CV at 1171 cm^-1 and 4-Mpy at 1095 cm^-1 were reduced only by around 24%and16%,respectively,as compared to the untreated substrate.(4)Ag/PAOCG-60 exhibited the optimal PNP reduction and SERS properties.88.9%of PNP was converted to PAP in the presence of Ag/PAOCG-60 and the pseudo-first-order kinetic rate constant was calculated to be 0.0203 min^-1.This film catalyst could be readily regenerated and reused for up to ten times without significantly depreciate its efficiency for PNP reduction.Ag/PAOCG-60 was capable of detecting as low as 10^-10 M aqueous CV.The uniformity,reproducibility and reusability of this SERS substrate was investigated in details.This substrate could be reused for at least five cycles without significantly reduced SERS performance.The intensity differences of characteristic peaks for CV at 1171 cm^-11620 cm^-1and 916 cm^-1 were only around 7.2%,14.4%and 6.1%,respectively,as compared to the initial untreated SERS substrate.(5)A simple but practical technique for preparation of Na₂Si O₃/Al₂O₃ composite coating on 304 stainless steel(SS)for enhancing high temperature oxidation inhibition and chloride-induced corrosion resistance was reported.The most effective protective sample which was prepared by 15 wt.%Na₂Si O₃solution had a weight gain of merely 0.010mg/cm² after placed at 1000 ^oC for 2 h,much lower than that of the bare SS(4.790mg/cm²).The mass gain per unit area as a function of time for thermal oxidation of uncoated,Al₂O₃ and Na₂Si O₃/Al₂O₃ coated SS in air at 1000 ^oC within 24 h was studied.The chloride-induced corrosion behavior of these samples was evaluated by polarization curves and electrochemical impedance spectroscopy(EIS)techniques in 3.5 wt.%Na Cl solutions for 21 days.To further explore the chloride-induced corrosion resistance mechanism,an equivalent circuit model has been put forward by using the ZView software.Time dependence of coating capacitance and coating resistance of these samples during 21days immersion was also investigated.