Study Of Synthesis And Properties Of Ag, TiO₂Micro/Nano Structures And Their Composite Materials

One dimensional of silver nanostructures, TiO2spherical structures as well as Ag@TiO2and Ag/AgCl composite materials have been synthesized by simple chemical method. AndTiO2materials, Ag/AgCl composite materials were used for the study of photocatalyticperformance. Among them, hollow TiO2microspheres show enhanced photocatalytic activitywhen compared with the solid ones; Ag/AgCl heterostructures, not only use the surfaceplasmon resonance effect of silver, but also use the semiconductor properties of silve chloride,which demonstrates an excellence photocatalytic performance and widen the response of thelight. The specific research contents as follows:1. Silver nanostructures were prepared via a polyol-thermal method, regulated byvariable valency metal ions. Various silver nanostructures were prepared by ethylene glycol(EG) reduction of silver nitrate together with poly (vinyl pyrrolidone)(PVP). Variable valencymetal ions, such as iron and copper, affected the morphologies of these nanostructures. Owingto the reduction of Ag+, Fe2+and Cu+with different reduction abilities, quasi-flag types ofsilver nanostructures and regular silver nanowires (Ag NWs) have been obtained.Furthermore, the diameter and morphologies of regular Ag NWs were adjusted by changingthe amount of PVP and CuCl2.2. The fabrication of multiple crystalline Ag NWs was regulated by EG and glycerolpolyol-thermal method. The large scale synthesis of multiple crystalline Ag NWs withuniform diameter was carried out by using EG and glycerol as co-mediated solvents in thepresence of PVP. Ag NWs are evolved from the multiple crystalline seeds initially generatedby the reduction of AgNO3with glycerol and EG. The different reduction ability and viscosityof EG and glycerol, playing an important role for the control of the nucleation at thebeginning of reaction, in the presence of PVP molecules selectively adsorbed on the surfaceof Ag seeds, glycerol with high viscosity slows down the migration velocity of Ag0in favorof forming the uniform Ag NWs with small diameter (40nm). The yield of the Ag NWs isdependent on the volume ratio of EG and glycerol. This paper provides a new approach forsynthesis of Ag NWs with uniform diameter by means of simply adjusting the solventcomponents. Furthermore, V-shaped Ag nanostructure was obtained with changing the reaction parameter, and the possible formation mechanism of the structure has beendiscussed.3. Hollow TiO2microspheres and Ag@TiO2composite material were successfullysynthesized. Hollow TiO2microspheres were prepared by metal salts with low solubility inethanol acting as intelligent templates through a simple one-pot solvothermal method. Hollowspheres with large diameter were obtained using CuSO45H2O as templates while small oneswere obtained using Sr(NO3)2as templates. Titanium precursor plays an important role for themorphology of samples. Solid TiO2microspheres were obtained by using titaniumtetrabutoxide (TBT). In contrast, bowl-like hollow microspheres were fabricated by usingtitanium tetrachloride (TiCl4). Furthermore, the amount of H2O can stimulate the hydrolysisrate of TiCl4to form solid spheres. Quantificationally, for the test of UV-lightphotodegradation of methyl orange (MO), the apparent photocatalytic degradationpseudo-first-rate constant of the hollow microspheres is1.25times of that of the solid ones.Besides, based on the synthesis of Ag NWs and TiO2hollow spheres, Ag@TiO2compositematerial with the diameter of70nm was successfully prepared.4. Plasmonic photocatalysts of Ag/AgCl necklace-like nano-heterostructures werefabricated. Ag/AgCl necklace-like nano-heterostructures with an average diameter of55nmwere synthesized by a facile oxidation process in situ. Owing to lots of boundaries existencein the multiple crystalline Ag nanowires, uniform Ag/AgCl necklace-like heterostructures canbe successfully obtained in the presence of PVP molecules. In contrast, the loose structure ofAg/AgCl with large particles was obtained without addition of PVP. And the formationmechanism of Ag/AgCl necklace-like nano-heterostructures has been proposed. Furthermore,the molar ratio of Ag and AgCl plays an important role for the photocatalytic activity of thenano-heterostructures which can be simple tuned. The results of photocatalytic investigationsdemonstrate the Ag/AgCl heterostructures with AgCl component of85%having excellentactivity for decomposing organic pollutants of MO and2,4-dichlorophenol as well as watersplitting to produce oxygen.5. Efficient plasmonic photocatalysts of molecularly homogeneous Ag/AgClnano-heterostructures was prepared at room temperature using a novel and facile method. Agparticles can be obtained by a rarely reported method using AgNO3and NaOH in the ethanol solution. And then Ag/AgCl heterostructures with the particle size of30-200nm can besuccessfully achieved when a certain amount of FeCl3.6H2O added into the mixed solution.The molar ratio of Ag and AgCl can be easily adjusted by changing the amount of FeCl3.When adding small amount of FeCl3, unhomogeneous Ag/AgCl heterostructures wereprepared, while increasing the amount of FeCl3, homogeneous Ag/AgClnano-heterostructures were obtained. Experiment results show that the Ag/AgClhomogeneous nano-heterostructures with50%and80%AgCl components both demonstrateexcellent activity for degradation of MO molecules under UV light.