中文摘要
摘要
TiO2是一种性能优越的环境功能材料，因其光催化活性高、性质稳定和价廉无毒等独特优势而被作为最常用的光催化剂。目前限制TiO2广泛应用有以下两个方面：一是光响应面较窄，仅能利用太阳光中紫外光；另外是电子-空穴易复合，光量子效率较低。本论文基于目前光催化技术的现状，提出以石墨烯为基底复合“上转换发光技术”和“TiO2光催化技术”是一种较有前景方法来改进光催化剂TiO2的光催化效率。
本论文通过水热法制备出稀土离子单掺的上转换材料β-NaYF4:Ho3+，溶胶凝胶法制备出核壳结构的β-NaYF4:Ho3+@TiO2可见光催化剂，通过紫外光还原GO 制备出β-NaYF4:Ho3+@TiO2-rGO三元光催化剂，为了考察制备的催化剂结构、形貌、发光性能以及光催化活性，本论文采用大量表征并得到以下结论：
①X射线衍射（XRD）和扫描电镜（SEM）结果表明β-NaYF4:Ho3+呈六棱柱状，其长约9.0 um，直径约4.0 um，通过能谱分析（EDS）和光电子能谱分析（XPS）结果表明上转换材料Ho元素是以离子价态形式存在于基质材料β-NaYF4的晶格内。β-NaYF4:Ho3+@TiO2复合光催化剂，通过透射电子显微镜（TEM）和STEM-EDS 等表征发现，复合材料呈核壳结构，且TiO2壳的厚度约50 nm。在β-NaYF4:Ho3+@TiO2-rGO三元光催化体系内rGO表现优异的二维片层结构，复合材料形貌和结构并没有
因为rGO的引入而发生改变。
②紫外可见漫反射（UV-Vis DRS）表征结果显示，β-NaYF4:Ho3+在可见光内有三个明显的吸收峰，分别为450、532和633 nm，并以此波长为激发波长，通过对上转换材料、复合材料和三元复合材料的荧光发射光谱（PL）表征发现：在三个可见光波长激发下均产生上转换现象，其中在450nm激发下发射出290 nm的紫外光，可激发TiO2产生光催化现象。另外通过改变激发光功率，可以确定该体系均发生的是两光子上转换现象。同时对β-NaYF4:Ho3+@TiO2的PL表征结果表明，在450 nm激发下产生的PL光谱极弱，发光被TiO2吸收利用。对比发现β-NaYF4:Ho3+@TiO2-rGO三元复合物在450 nm激发下的PL峰进一步减弱，几乎不发射荧光，这是由于体系内rGO的引入有利于提高光催化的效率。
③通过傅立叶红外光谱（FTIR）、拉曼光谱（Raman）、XPS和UV-Vis DRS 表征表明在三元复合体系内存在rGO，而且在还原过程中TiO2和rGO形成Ti-C 化学键，有利于使TiO2的吸收截面红移。通过电化学、3D荧光光谱和电子自旋共振（ESR）表征得出，在β-NaYF4:Ho3+@TiO2-rGO三元光催化剂体系中，由于rGO 的引入可有效增强电子的传输能力，有利于提高电子和空穴的分离，同时比表面
积表征（BET）发现由于rGO的引入使得体系的比表面积和孔径都有较大的提升，有利于有机污染物的吸附降解，增强光催化性能。
④β-NaYF4:Ho3+@TiO2-rGO三元光催化剂光催化降解实验结果表明，对RhB 溶液的脱色效果光催化剂用投加量有关，当光催化剂投加量为0.15 g时，脱色效果最好，光照下10 h的RhB脱色率高达95%。而底物浓度与RhB溶液的脱色效果成反比。RhB浓度为4.0 mg/L时，脱色效果最好，光照下10 h可实现完全脱色。光照强度增大时，光催化剂对RhB的脱色率呈上升趋势，光照强度为100600 lx 时，光照下6 h即可实现完全脱色。β-NaYF4:Ho3+@TiO2-rGO三元光催化剂降解RhB的符合Langmuir- Hinshelwood零级动力学方程。考虑光催化剂用量（m cata）、底物的初始浓度（C0）和光照强度（E）因素对脱色效果的影响，给出β-NaYF4:Ho3+@TiO2-rGO光催化剂降解RhB的总反应动力学模型为：
{
C R=C0-3.96993×10-7m cata
0.31404
C00.7179E0.59734
(50mg≤m cata≤150mg, 4mg/L≤C0≤9mg/L, 40700 lx≤E≤100600 lx)
C R=C0-5.68888×10-5m cata英语动物谜语
-0.67537
C00.7179E0.59734
(150mg≤m cata≤300mg, 4mg/L≤C0≤9mg/L, 40700 lx≤E≤100600 lx)关键词：光催化，上转换发光，石墨烯，二氧化钛，三元复合物
扫地的英语
TiO2is a kind of environmental functional material with excellent performance, which is friendly to the environment, it’s also stable in quality and cheap in price. However, due to the wide band gap of TiO2, it can only be excited by ultraviolet light, so it’s utilization rate of solar light is very low; on the other hand, the TiO2 electron hole recombination rate is high, leads to the low light quantum efficien
大三阳的症状cy. So that the wide application of TiO2has been affected and restricted. Bad on the analysis of the existing photocatalyst modification technology that the graphene platform "upconversion (UC) technology" and "TiO2 photocatalytic technology" is a promising treatment technology.
The samples prepared by hydrothermal method of rare earth ions doped UC material β-NaYF4:Ho3+, sol-gel preparation of β-NaYF4:Ho3+@TiO2core-shell photocatalyst, and UV reduction of GO preparation of β-NaYF4:Ho3+@TiO2ternary photocatalyst. And the photoca talyst’s structure, morphology, luminescent properties, and photocatalytic properties were studied in the next.The main contents and conclusions of the paper are as follows:
生产质量标语①The X ray diffraction (XRD) and scanning electron microscopy (SEM) results showed that β-NaYF4:Ho3+ was hexagonal. The average microcrystal length is roughly 9.0 um, with a diameter of about 4.0 um. The spectrum analysis (EDS) and X-ray photoelectron spectroscopy (XPS) results show that Ho3+ had successful incorporation of rare e arth ions into the β-NaYF4 host matrix. The TEM and STEM-EDS results show that the UC microcrystals are uniformly coated by a TiO2layer, and the average thickness of the TiO2shells is about 50 nm. In the β-NaYF4:Ho3+@TiO2-rGO ternary photocatalytic system, the rGO exhibits in the excellent sheet structure, and the morphology and structure of the composites are not changed.
②The UV-Vis absorbance spectra (UV-Vis DRS) showed that the β-NaYF4:Ho3+ has obviously three absorption peaks, 450, 532 and 633 nm. The fluorescence spectrum (PL) results show that the UC phenomenon can occur under the excitation of Vis, which emits UV light of 290 nm under the excitation of 450 nm can be strongly quenched by being absorbed by TiO2. The dependence of luminescence intensity on excitation power results shows that the transitions were all transitions of two-photon UC process. After coating β-NaYF4:Ho3+ with TiO2, notable spectral differences were obrved. The
inten emission peak at 290 nm almost disappeared. For rGO-assisted β-NaYF4:Ho3+@TiO2, the low emission intensity can be ascribed to the fact that the lights were absorbed by the composite with the help of rGO.
逢的组词
③The FTIR, Raman, XPS, and UV-Vis DRS results showed that the existence of rGO in ternary photocatalytic system. Moreover, the existence of Ti-O-C bond indicates the existence of chemical bond force between rGO and TiO2, and such chemical bond is beneficial to the red shift of absorbed wavelength. The photoelectrochemical three-dimensional fluorescence spectroscopy, and electron s
pin resonance (ESR) results showed that the introduction of rGO can effectively enhance the electron transfer capability, which is beneficial to improve the paration of electrons and holes. Brunauer-Emmett-Teller surface area measurement (BET) showed that the introduction of rGO can enlarge surface area and pore volume, are beneficial for the β-NaYF4:Ho3+@TiO2-rGO composite contacting with organic contaminants,
④Rhodamine B was ud in a ries of degradation experiments to evaluate the photocatalytic activity of β-NaYF4:Ho3+@TiO2-rGO. The results showed that with the increa of the amount of photocatalyst, the photocatalytic degradation effect incread at frist and then decread, and decolorization rate of RhB is up to 95% within 10 h when the photocatalyst dosage is 0.15 g. The initial concentration was inverly proportional to the decolorization rate, and completely bleached of RhB within 10 h when the initial concentration of RhB was 4.0 mg/L. When the light intensity incread, the decolorization rate of RhB on the photocatalyst showed an upward trend. When the light intensity was 100600 lx, the decolorization could be achieved by 6 h. The degradation of RhB by β-NaYF4:Ho3+@TiO2-rGO ternary photocatalyst was consistent with the zero order kinetic equation of Langmuir-Hinshelwood. Considering the factors of the photocatalyst dosage (m cata), the initial concentration of RhB (C0) and light intensity (E), the dynamic model is:
{
C R=C0-3.96993×10-7m cata
0.31404
C00.7179E0.59734
专家库(50mg≤m cata≤150mg, 4mg/L≤C0≤9mg/L, 40700 lx≤E≤100600 lx)
C R=C0-5.68888×10-5m cata
-0.67537
C00.7179E0.59734
(150mg≤m cata≤300mg, 4mg/L≤C0≤9mg/L, 40700 lx≤E≤100600 lx)
Keywords: Photocatalysis, Upconversion Luminescence, Graphene, Titania, Ternary Composite
目录
目录
中文摘要.......................................................................................................................................... I 英文摘要....................................................................................................................................... III 1 绪论.. (1)
1.1 引言 (1)
1.2 光催化概况及研究现状 (3)
1.2.1 光催化原理 (3)
1.2.2 TiO2光催化技术的特点及存在问题 (4)
1.2.3 TiO2光催化剂改性方法 (5)
1.3 上转换技术研究现状 (7)
1.3.1 上转换技术概述 (7)
1.3.2 上转换发光材料 (8)
1.3.3 上转换发光机理 (8)
1.3.4 上转换发光材料复合光催化剂研究现状 (11)
我的卧室英语作文
1.4 石墨烯的研究进展 (12)
1.4.1 石墨烯的概述 (12)
1.4.2 石墨烯性质 (12)
1.4.3 石墨烯负载TiO2复合光催化剂研究进展 (13)
1.4.4 石墨烯作为基底改性上转换复合TiO2光催化剂研究进展 (14)
1.5 课题的提出及主要研究内容 (14)
1.5.1 课题的提出 (14)
1.5.2 主要研究内容 (15)
2 实验材料与方法 (17)
2.1 化学试剂与仪器 (17)
2.1.1 化学试剂 (17)
2.1.2 实验仪器 (17)
2.2 实验方法 (18)
2.2.1 上转换材料β-NaYF4:Ho3+的制备方法 (18)
神奇的近义词是什么2.2.2 β-NaYF4:Ho3+@TiO2核壳微晶制备方法 (19)
2.2.3 β-NaYF4:Ho3+@TiO2-rGO三元光催化剂的制备方法 (19)
2.3 材料表征方法 (19)
2.3.1 X射线衍射表征（XRD） (19)
