【作者】 王彦敏；

【导师】 刘宏；

【作者基本信息】 山东大学 ， 材料学， 2009， 博士

【摘要】 自1991年日本学者饭岛澄男发现碳纳米管以来,一维纳米材料（纳米管、纳米棒、纳米线、纳米带、同轴纳米电缆等）引起了人们的广泛关注。近来随着TiO₂纳米线、纳米管及纳米带等一维纳米结构的合成和性能研究的开展,二氧化钛在催化、传感器、水处理等领域显示了更广阔的应用前景。二氧化钛是一种多功能材料,具有良好光电性能、气敏特性和光催化性能,但是目前应用于以上用途的二氧化钛一般以纳米颗粒或者薄膜的形式存在,对于二氧化钛纳米带的研究、特别是应用研究较少,且其光电性能、气敏特性和光催化性能仍然无法满足实际应用要求。因此,本研究在采用水热法实现批量制备高质量二氧化钛纳米带的基础上,通过对其改性,制得二氧化钛纳米带表面异质结构,实现对纳米带性能的调控,制备高性能二氧化钛纳米器件并探索其在光电、光催化、传感器等几个方面的应用。随着器件制备技术的显著进步,人们实现了单根纳米带性能的测量,并利用单根半导体纳米带或者纳米带阵列制成了超灵敏纳米场效应管、光电器件、气体传感器和生物传感器。但是由于利用纳米带制备这些纳米器件一般需要价值昂贵的设备,其制造成本使得这些传感器几乎无法投入市场。本研究提出了采用普通的造纸原理将氧化物纳米带制成纳米纸张的新思路,然后将纸张按照一定的标准切割、连接、封装就可以制备性能均一的器件,此方法为纳米带由实验室走向实际应用提供了一条可行的新途径。本研究中采用氧化钛基纳米带构成的纳米纸张,制备了相应的纳米器件,研究其在光电器件、气敏元件和生物传感器方面的应用。本研究得到的主要结论如下:1、利用水热法实现了Na₂Ti₃O₇、H₂Ti₃O₇和TiO₂纳米带的批量合成。通过XRD、TEM、SEM等手段对所制备的纳米带进行表征。结果表明:纳米带宽度为50-200nm,长度达到几十微米,甚至一百多微米;产物产率高,质量好,结晶良好,表面洁净,无缺陷。纳米带的形成机制为“溶解一结晶”机制。首先TiO₂被NaOH溶液在水热条件下溶解,然后结晶生长,形成Na₂Ti₃O₇纳米带;酸洗后,Na⁺和H⁺交换,形成H₂Ti₃O₇纳米带;经一定温度的热处理后转变为TiO₂纳米带。2、将制备的氧化钛基纳米带采用普通的造纸原理得到了厚度一致的柔性纳米结构纸张。将纸张按照一定标准切割、连接、封装制备了性能均一的器件。对TiO₂、H₂Ti₃O₇和Na₂Ti₃O₇纳米结构纸的电子传输性能进行了检测,其可测的Ⅰ-Ⅴ行为说明了纳米结构纸在传感器方面的潜在应用。研究了TiO₂纳米带结构纸张对O₂的敏感性,结果表明,氧化钛纳米结构纸表现出了对氧气的超敏感性。通过抗菌实验测了改性制备的Ag-H₂Ti₃O₇纳米结构纸的抗菌和抑菌性能,结果表明Ag-H₂Ti₃O₇纳米结构纸具有良好的抗菌和抑菌性能,将在无菌过滤和空气过滤方面具备应用前景。3、通过光催化还原金属离子法制备了贵金属（Au、Ag）/TiO₂纳米带表面异质结构。通过XRD、TEM、SEM、XPS等手段对样品进行表征,结果表明,贵金属（金、银）离子都被还原形成了贵金属单质纳米颗粒,在二氧化钛纳米带上分散良好,颗粒均匀一致。合成的Ag/TiO₂异质结构纳米带,表面纳米Ag颗粒的粒径约为10nm。而Au/TiO₂异质结构纳米带,表面纳米Au颗粒的粒径约为30nm。利用这种方法制备贵重金属/TiO₂异质结构纳米带的方法,制备工艺简单,表面洁净无污染,不需要添加任何表面活性剂。此材料可以在光催化、催化、杀菌以及太阳能电池等领域具有广泛的应用。4、采用TiO₂纳米带、Ag/TiO₂异质结构纳米带修饰改性玻碳电极,并对其电化学性能进行了研究。结果表明,Ag/TiO₂/GCE在PBS溶液中表现出了稳定的电化学行为,在不同浓度的L-半胱氨酸的0.25 M PBS（pH 7.0）溶液中的循环伏安曲线表明该电极对于巯基的检测表现出了很高的灵敏度。这预示了Ag/TiO₂在生物传感器方面的潜在应用。5、通过液相合成法在TiO₂纳米带表面组装ZnO纳米结构,制备了ZnO/TiO₂纳米带表面异质结构。所制得的产物是TiO₂的纳米带表面组装了ZnO纳米花:TiO₂纳米带的宽度为50-200纳米,长度达到几十微米,而ZnO异质结呈花状,长为500纳米的骨苞上长有200纳米左右的花瓣。这种异质结构纳米材料将在光催化、气体传感器、太阳能电池等领域有重要作用。6、将H₂Ti₃O₇纳米带在一定浓度酸溶液中、100℃温度条件下进行腐蚀,再经600℃1h热处理制备了Anatase TiO₂纳米颗粒/Anatase TiO₂异质结构纳米带（ANP/ANB TiO₂异质结构）,然后采用光催化还原方法在此表面沉积金属Ag,制备了Ag/ANP/ANB TiO₂双异质结构纳米带。对所制得的样品通过XRD、TEM、HRTEM和UV-Vis光谱进行了表征。采用氧化钛P25和未腐蚀的TiO₂纳米带做参照,研究了ANP/ANB TiO₂异质结构纳米带和Ag/ANP/ANB TiO₂双异质结构纳米带的光催化性能,结果表明:异质结构纳米带的光催化性能明显高于未经过处理的TiO₂纳米带;通过贵重金属沉积的异质结构纳米带的光催化性能高于未沉积贵重金属异质结构纳米带;经过24h腐蚀的异质结构ANP/ANB TiO₂纳米带和经过12h腐蚀的异质结构Ag/ANP/ANB TiO₂纳米带的光催化性能和氧化钛P25相当。综上所述,本研究提出”二氧化钛纳米带表面异质结构”的概念,采用光催化还原技术原位制备了贵金属（Au、Ag）/TiO₂纳米带表面异质结构;采用液相合成法制备了ZnO/TiO₂纳米带表面异质结构;采用酸溶液腐蚀方法制备ANP/ANB TiO₂异质结构纳米带和Ag/ANP/ANB TiO₂双异质结构纳米带;采用不同表征手段对纳米带异质结构进行了表征,并且对异质结构纳米带表面能级、电子传输性能、光催化性能等进行了研究。本研究采用专利技术将所制备的纳米带制备成“纳米结构纸张”,并制备相应的纳米器件,研究了其在光电器件、气敏元件和生物传感器方面的应用,为纳米带材料由实验室走向实际应用提供一条可行的途径。更多还原

【Abstract】 Since the discovery of carbon nanotubes in 1991,much interest has been focused on the one-dimensional nanostructures due to their exceptional electric, mechanical,and chemical properties.Among such materials,titania nanotubes, nanowires and nanoribbons（or nanobelts） have received a great deal of attention, because TiO₂ can exhibit a wealth of important photovoltaic（solar energy conversion）,photocatalytic,catalytic support and gas-sensing properties, especially when prepared as nanomaterial.TiO₂ is a multifunctional material with remarkable chemical,electronic and optical properties.TiO₂ membranes and nanoparticles have been extensively studied.However the applications of TiO₂ nanobelts have been rarely studied.Furthermore,the properties of photoelectric, gas-sensitive and photocatalysis of TiO₂ nanobelts are still too low to fit for the requirement of application.Herein,the synthesis of titanate nanobelts from commercial TiO₂ via the alkali-hydrothermal process was reported.The synthesis route achieves high yield production of TiO₂-based nanobelts.In order to improve the properties,TiO₂ nanobelts are modified and "surface heterostructured nanobelts" concept is proposed in this paper.Recently,with the development of the techiques for preparation of nanodevices,many ultra-sensitive devices such as field effect transistors, optoelectric devices,gas sensors,biosensors,etc.,have been fabricated using single nanobelt or nanobelt an’ay.Some of them have to be fabricated using complex and high-cost techniques such as focused-ion-beam microscopy of electrical connections and precise photolithography.Although electrical responses of single-nanobelt devices are very sensitive to their environment,the size variation of nanobelts may lead to significant difference in their intrinsic electrical properties.As a result,it is difficult to be well calibrated for practical applications. Based on the as-made nanobelts,a novel preparation route was used to fabricate paper-like nanostructured membrane,which was also called as nanostructured sheet or nanostructrued paper.The nanobelts are packed together forming a porous network structure by a conventional paper making process.Nanodevices,such as photo-electric devices,gas sensor,biosensor,can be made by tailoring,connecting and sealing the nanostructrued paper.This research will be open a new door for the application of nanobelts.The main conclusions arc as followings:1.Titania-based nanobelts from commercial TiO₂（annatase phase） were successfully synthesized via an alkali-hydrothermal process.The as-synthesized nanobelts are sodium titanate（Na₂Ti₃O₇）,hydrogen titanate（H₂Ti₃O₇） and anatase （TiO₂）.The nanobelts are characterized by Thermogravimetric/Differential Thermal Analysis（TG/DTA）,X-ray Diffraction（XRD）,Infrared Spectra（IR）, transmission electron microscopy（TEM） and Scanning Electron Microscope （SEM）.The characterization indicates that the nanobelts with typical widths of 50 to 200 nm,thicknesses of 20 to 50 nm,were up to one hundred micrometer in length.H₂Ti₃O₇ nanobelts can be obtained from Na₂Ti₃O₇ by exchanging alkali ions with protons using dilute acid solution.The anatase nanobelts can be obtained from H₂Ti₃O₇ by a topochemical reaction and dehydrating process.2.Based on the as-made nanobelts,the conventional paper making process was used to fabricate flexible nanostructured paper.The nanobelts are connected with hydrogen bonds or bridge-oxygen-atoms and packed together forming a porous network structure and the average size of the pores of the nanostructured paper is about 500nm.The electric transport properties of the as-made nanostructured paper were measured and the detectable conductive behavior of the nanostructured paper promises the potential application in sensors by designing a corresponding electronic device.Moreover,it is very convenient for preparing various types of nanobelts-based devices by tailoring the nanostructured paper to the designed sizes and shapes.Gas sensitivity to O₂ of TiO₂ nanopaper was investigated which revealed ultrasensitive detection for O₂.This suggests that TiO₂ nanobelt-based paper can be applied in gas sensing with performances suitable for the environment at room temperature.Ag-H₂Ti₃O₇ nanostructured paper with antibacterial effect was obtained by decorating the nanobelts with silver nanoparticles.The zone of inhibition test results showed that an obvious zone inhibition appearing around the Ag-H₂Ti₃O₇ nanostructured paper.3.Noble metals（Ag,Au）/TiO₂ heterostructured nanobelts were prepared by the photocatalytic reduction method at room temperature without template and surfactant as additions.The silver particles,with the grain size of about 10nm, deposited on the surface of nanobelts are uniform.And the grain size of Au on the surface of nanobelts is about 30nm.The noble metal nanoparticles attached on the TiO₂ nanobelts will not only retain catalytic activity of the noble metals,but also possess the intrinsic photocatalysis of TiO₂.Therefore,The promising applications in both heterogeneous and homogeneous catalysis of the as-made samples may exist.4.TiO₂ nanobelts and Ag/TiO₂ heterostructured nanobelts was used to modify glassy carbon electrode（GCE）,respectively.The electrochemical voltammetric properties and the detection of low concentration Logystein in 0.25 M pH 7.0 PBS solutions of the Ag/TiO₂ heterostructured nanobelts modified GCE were studied. The results shows that the modified electrode was stable and can be used to detect the very low concentration of L-gystein(1×10^-7M).The Ag-TiO₂ heterostructured nanobelts offer great advantages to fabricate biosensors.5.ZnO/TiO₂ heterostructured nanobelts were successfully synthesized through the liquid phase method.The samples obtained were characterized by different techniques,such as XRD,SEM,and TEM.The products are ZnO nanoflowers self-assembled on the surface of TiO₂ nanobelts.The nanobelts are 50-200nm in width and several tens micrometers in length,while the ZnO heterostructure is a bud with 500nm in length and with the petals of about 200nm. The formation mechanisms of the titanium dioxide nanobelts and the composites mentioned above were also discussed briefly.6.The Rutile TiO₂ nanoparticles/Anatase TiO₂ nanobelts（ANP/ANB TiO₂） heterostructrue was prepared by eroding H₂Ti₃O₇ nanobelts in 100℃certain concectration acid solution and then heat-treated the eroded H₂Ti₃O₇ nanobelts at 600℃for 1h.To make the Ag/ANP/ANB TiO₂ bi-heterostructrue,Ag nanoparticles were deposited on the ANP/ANB TiO₂ heterostructrue by the photocatalytic reduction method at room temperature.The heterostructrued nanobelts were characterized by XRD,TEM,HRTEM and UV-Vis spectra.The photocatalytic properties of the heterostructrued nanobelts were studied by degrading methyl orange solution.The results indicate that the heterostructrued nanobelts possessed higher photoeatalytic properties than that of TiO₂ nanobelts.Ag/ANP/ANB TiO₂ heterostructrue possessed higher photocatalytic properties than that of ANP/ANB heterostructrue.In conclusion,the concept of TiO₂ nanobelt surface hetero-structure is proposed in this paper.The metal/TiO₂ nanobelt heterostructure can be synthesized through photo-catalysis reduction technique,and.The adjustment regularity of surface energy level,electric transport properties,photo-electric coupling effect,and gas sensitive effect on the surface heterostructure of the nanobelts will be investigated through optical spectra measurement and electric measurement on individual nanoblets.A novel nanostructured paper based on TiO₂ nanobelts and heterostructured nanobelts can be prepared through our patented nanopaper making technique.Some nanodevices,such as photo-electric devices,gas sensor,and biosensor will be prepared by using the nanopaper as building bricks.This research will be open a new door for the application of nanobelts.更多还原