ZnO和NiSe纳米材料增强的吸附与传感性能及其机制研究

【作者】 裴翠锦；

【导师】 杨合情；

【作者基本信息】 陕西师范大学 ， 材料学， 2016， 博士

【摘要】 采用简单的溶剂热法和溶液快速热反应法成功制备出ZnO超薄纳米片组装的三维花状分级结构,In掺杂的暴露{001}晶面ZnO泡沫结构和蜂窝状超长NiSe纳米带。采用场发射扫描电子显微镜(FESEM)、多功能成像光电子能谱仪(XPS)、X射线衍射仪(XRD)、透射电子显微镜(TEM)、原子力显微镜(AFM)、红外光谱仪(IR)、物理吸附仪和热重分析仪等对产物的形貌和结构进行表征。探索ZnO花状分级结构、NiSe超长纳米带对三苯甲烷类染料的吸附特性,系统研究了吸附剂的形貌、吸附时间、染料浓度、溶液pH值和溶液温度等条件对三苯甲烷类染料吸附量的影响,探讨了其可能的吸附机制;研究了氢化处理后的ZnO纳米颗粒和In掺杂的暴露{001}晶面ZnO泡沫结构的传感性能,探讨了 ZnO样品表面结构变化与传感性能的关系,并初步阐明电阻型传感器的传感反应机制。这些研究结果为ZnO、NiSe纳米结构材料的可控制备、物理化学性能研究特别是在吸附、传感、光催化等领域的进一步应用奠定了基础。具体研究结果如下:(1)在乙酸锌-亚硒酸钠-硼氢化钾-吡啶溶剂热体系中,100 ℃反应24 h成功制备出由厚度约为1.5 nm的ZnO超薄纳米片组装而成的花状分级结构。测得其比表面积为132 m2/g。研究了ZnO花状分级结构对酸性品红、孔雀石绿、碱性品红、刚果红和酸性大红染料的吸附性能,其对应吸附量分别为7154.9,2587.0,1377.9,85.0和38.0 mg/g。结果表明,ZnO超薄纳米片组装的花状分级结构对三苯甲烷类染料酸性品红、孔雀石绿和碱性品红具有优异的吸附性能,尤其是对酸性品红的吸附量为目前已有报道中量值最高的。对吸附过程中的吸附动力学、吸附等温线进行了模拟研究,发现该吸附过程均符合准二级动力学模型和Langmuir等温线模型。探讨了可能的吸附机理,认为ZnO花状分级结构对三苯甲烷类染料的吸附主要归因于两者之间的静电作用和离子缔合物的形成。(2)通过简单的溶液快速热反应法,在550 ℃下制备出In掺杂的暴露{001}晶面ZnO三维泡沫结构,并研究其对乙醇、甲醛、丙酮和甲醇的传感特性,发现其对乙醇的响应灵敏度明显高于其它三种气体。在350 ℃测试条件下,In掺杂的暴露{001}晶面ZnO泡沫结构对400ppm乙醇的响应灵敏度达到了308。分析了掺In浓度与ZnO泡沫结构结晶性和比表面积的关系,探讨了活性晶面的暴露、结晶性、比表面积、表面吸附氧含量等因素对样品传感性能的影响,提出了传感反应的机理。实验结果表明,In的掺杂改变了ZnO样品的表面结构及结晶性,适当浓度In的掺杂可以显著提高ZnO传感材料的灵敏度,同时也可以改善传感反应的选择性。(3)对商业ZnO粉末在500℃下进行氢化处理,将氢化后所得的ZnO样品制作成传感元件,研究其对丙酮、甲醛、三乙胺和乙醇的传感性能。在350 ℃测试条件下,发现不同时间通氢处理后的ZnO样品均比未通氢处理的ZnO样品具有更好的响应灵敏度,且其传感性能随着通氢时间的延长而逐渐增强。考察了通氢时间与样品表面吸附氧含量以及红外光谱中羟基变化的关系,比较了通氢前后ZnO样品分别在空气和饱和待测气体气氛中电阻的变化。提出了该传感反应的活性位是带有悬挂键的不饱和的Zn原子这一概念,探讨了传感反应的物理本质。实验结果表明,对ZnO样品进行氢气处理是提高传感器灵敏度的一种简单有效的方法,所提出的传感反应活性位为带有悬挂键的不饱和Zn原子这一概念,对理解半导体纳米材料传感反应机理有一定的借鉴意义。(4)在金属镍片-硒粉-硼氢化钾-乙二胺的溶剂热体系中,180 ℃下反应12 h以及后续热处理,在Ni片基底上制备出了 NiSe超长纳米带自组装的蜂窝状结构。通过时间调控实现了不同纵横比纳米结构的可控合成。研究了其纵横比依赖的吸附性能,发现在180℃下反应2,6和12 h并且热处理后所得NiSe纳米结构对孔雀石绿的吸附量分别可达到329.5,366.8和501.5 mg/g,其吸附性能随着NiSe纳米结构纵横比的增大而增强。研究了蜂窝状结构的NiSe超长纳米带和NiSe八面体的吸附性能,发现NiSe超长纳米带的吸附性能明显优于NiSe八面体,表明NiSe超长纳米带具有的优异吸附性能可能与其独特的蜂窝状结构和较大的比表面积有关。对吸附过程中的吸附动力学、吸附等温线以及热力学进行了模拟和计算分析。探讨了可能的吸附机理,认为NiSe超长纳米带对孔雀石绿的吸附主要归因于两者之间的静电作用。更多还原

【Abstract】 ZnO flower-like architectures,In doped ZnO foam structures and ultralong NiSe nanobelts were synthesized by solvothermal and solution combustion method at 550 ℃.Morphologies and structures of these products were characterized by means of field emission scanning electron microscope(FESEM),scanning electron microscopy(SEM),X-ray photoelectron spectra(XPS),X-ray diffraction(XRD),transmission electron microscopy(TEM),atomic force microscopy(AFM),IR spectrum and absorption-desorption porosimetry.The adsorption performance of ZnO flower-like architectures and ultralong NiSe nanobelts for triphenylmethane dyes were studied.The effect of adsorbents morphology,adsorption time,dye concentration,pH and solution temperature for adsorption capacity were investigated,and the adsorption mechanism was discussed.The influence of hydrogenation and In-doping on the gas sensing properties of the ZnO structures was explored,and the sensing reaction mechanism was proposed.These research results would provide a base for further research on synthesises of ZnO,NiSe nanostructures,the physical and chemical properties of ZnO,NiSe nanostructures and their applications in adsorption,sensor and photocatalyst.Specific research results as follows:(1)The 3-dimensional hierarchical ZnO flower-like architectures were synthesized in a Zn(Ac)2-2H2O-Na2SeO3-KBH4-pyridine solvothermal system at 100 ℃ for 24 h.The flower-like architecture is assembled from ZnO nanosheets with a thickness of～1.5 nm,and the flower-like architecture specific surface area is 132 m2/g.When the ZnO flower-like architecture is used as the adsorbent for acid fuschin(AF),malachite green(MG),basic fuchsin(BF),congo red(CR)and acid red(AR)in water,the adsorption capacities for AF,MG,BF,CR and AR are 7154.9,2587.0,1377.9,85.0 and 38.0 mg/g,respectively.Evidently,the as-obtained ZnO flower-like architectures show excellent adsorption performances for triphenylmethane dyes,and the adsorption capacity of 7154.9 mg/g for AF is the highest of all adsorbents for dyes.The adsorption mechanism can be attributed to the electrostatic attraction and the formation of ion-association complex between triphenylmethane dyes and ZnO hierarchical flower-like architectures.(2)In doped ZnO foam structures with exposed {001} facets were successfully prepared by solution combustion method at 550 ℃,and the influence of different In-doping concentrations on the gas sensing properties of the ZnO foam structures was explored.The ZnO foam with 5%of In-doping exhibits the highest sensitivity(about 308)to 400 ppm ethanol at 350 ℃.The effect of crystallinity,crystallite size,specific surface area and surface adsorption oxygen content on gas-sensing property of ZnO samples was investigated.The excellent sensing performance to ethanol was attributed to the increase in the surface and the amount of adsorbed oxygen.(3)Hydrogenation is successfully used to enhance ZnO-based gas sensors.The hydrogenated ZnO sensors show significantly higher response to organic compound vapors than the samples without hydrogenation.The relationship between the time of hydrogenation and the oxygen content of the sample surface as well as the hydroxyl in the infrared spectrum was investigated.The resistance change of the ZnO samples before and after hydrogenation was compared.The enhanced sensing performance is attributed to the increased density of the unsaturated Zn atoms with dangling bonds on the surface resulted from the hydrogenation process.The unsaturated Zn atoms with dangling bonds are found to be active sites for the sensing reaction.The concept of the unsaturated metal atoms with dangling bonds serving as active sites can deepen understanding of the sensing reaction mechanisms and affords guidance to design more effective gas sensing materials.(4)The ultralong NiSe nanobelts were synthesized by a solvothermal reaction of Ni with Se and KBH4 in ethylenediamine at 180 ℃ for 12 h and subsequent annealing in Ar.The aspect ratios of nanobelts can be changed by tuning the reaction time.These NiSe nanostructures were used as adsorbents in wastewater treatment,and the adsorption capacities for MG are 329.5,366.8 and 501.5 mg/g,respectively.It was found that the adsorption performance was improved with an increase on the aspect ratios of NiSe nanostructures.The excellent adsorption performance of the as-prepared ultralong NiSe nanobelts for MG removal could be attributed to the unique honeycomb-like superstructures and high surface area.The adsorption process agreed well with the pseudo-second-order kinetics and the Langmuir isotherm equation.Thermodynamic parameters indicated the feasibility of the adsorption process.Electrostatic attraction between Malachite green and NiSe ultralong nanobelts was considered as the adsorption mechanism.更多还原