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Adsorption of catechols at TiO2 single crystal surfaces.Charge transfer processes in photovoltaics and structure of novel biomedical materials.

邻苯二酚在 TiO2 单晶表面的吸附。光伏中的电荷转移过程和新型生物医学材料的结构。

基本信息

批准号：
EP/H020446/1
负责人：
Andrew THOMAS
金额：
$ 0.54万
依托单位：
University of Manchester
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2009
资助国家：
英国
起止时间：
2009 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=EP%2FH020446%2F1
关键词：
Adsorption catechols TiO2 single crystal

项目摘要

This project will study the interaction of two molecules from a group of ring molecules called catechols, namely pyrocatechol and dopamine, with titanium dioxide (TiO2) surfaces. This interaction is of some interest for two reasons. Firstly it has been known for about 10 years or so that pyrocatechol (and other catechols including dopamine) adsorbed on TiO2 nanoparticles shifts the absorption of light from the ultraviolet region to the visible region of the electromagnetic spectrum. Since TiO2 is so cheap this may offer the potential for new cheap solar generation of electricity. It has been suggested in these types of cells, where a molecule is attached to a semiconductor surface that the strength of attachment is key in the efficient transfer of charge from the molecule to the surface. The other problem is that TiO2 is a photocatalyst capable of decomposing certain organic molecules so clearly the long term stability of the molecule must be understood and verified before this type of technology is developed. In addition, the catechol-TiO2 system is of interest as a possible targeted biomedical material. Unlike catechol, dopamine has a small chain on the side of the ring which can be grafted onto other molecules. In this way the dopamine can be attached to the surface of TiO2 nanoparticles and these functional molecules attached to the chain. Careful selection of the functional molecules can allow the nanoparticle TiO2 to respond to a specific stimulus. A polymer chain - Polytheyleneglycol (PEG) - effectively renders the nanoparticles invisible to the body's immune system. The inclusion of grafted temperature sensitive molecules along with the PEG means that at the site of an infection or disease the nanoparticles will clump together and form an opaque region in an x-ray. Since the particles are small they can be injected - thus quickly giving a surgeon information on where a problem may be located. Again one of the potential problems in these particles is the stability. We have been working with colleagues in the School of Pharmacy at Manchester, looking at the real nanoparticle systems but the surface structure is complicated by the presence of solvents and molecules used in the synthesis of the particles and chains. In this work we will use atomically clean surfaces and deposit carefully controlled amounts of pure catechols. Using the radiation facility at Elettra on Trieste we can determine a number of things about the nature of the chemistry at the surface including the orientation of the molecules and their stability over short timescales and different conditions. X-ray photoemission and absorption spectroscopies will be used to determine changes to the chemistry over time. In addition using a combination of x-ray absorption and photoemission we are able to infer the charge transfer time between the adsorbed molecules and the surface of the TiO2. We will study adsorption two different surfaces of TiO2 i.e. the rutile (110) and anatase (101), which arise from different crystal structures of TiO2. Anatase is the structure adopted by nanoparticulate TiO2 so our studies on this crystal will potentially give more realistic information. Rutile is a more widely studied material as it is easier to grow and obtain commercially. In fact we are one of the few groups who have carried out substantial research on anatase single crystal surfaces. Although some of what we have determined in previous work suggests organic acid molecules interact in similar ways on these two surfaces it is of some fundamental interest to determine whether this is also the case for the catechols. In addition the two different molecules will allow us to determine whether the presence of the side chain on the dopamine results in differences in the adsorption geometry or the chemical stability since this chain could potential react with the oxygen molecule through which the dopamine bonds to the surface.

该项目将研究一组称为儿茶酚的环状分子中的两种分子（即邻苯二酚和多巴胺）与二氧化钛（TiO 2）表面的相互作用。这种相互作用有两个原因。首先，大约10年前就已经知道，吸附在TiO 2纳米颗粒上的邻苯二酚（和其他儿茶酚，包括多巴胺）将光的吸收从电磁光谱的紫外区转移到可见区。由于TiO 2是如此便宜，这可能提供新的廉价太阳能发电的潜力。在这些类型的细胞中，分子附着在半导体表面上，附着的强度是电荷从分子有效转移到表面的关键。另一个问题是，TiO 2是一种光催化剂，能够分解某些有机分子，因此在开发这种类型的技术之前，必须了解和验证分子的长期稳定性。此外，儿茶酚-二氧化钛系统作为一种可能的靶向生物医学材料的兴趣。与儿茶酚不同，多巴胺在环的一侧有一个小链，可以接枝到其他分子上。通过这种方式，多巴胺可以附着在TiO 2纳米颗粒的表面，并将这些功能分子附着在链上。仔细选择功能分子可以使纳米颗粒TiO 2对特定的刺激做出响应。一种聚合物链-聚乙二醇（PEG）-有效地使纳米粒子对人体的免疫系统不可见。与PEG一起沿着的接枝温度敏感分子的包含意味着在感染或疾病的部位，纳米颗粒将聚集在一起并在X射线中形成不透明区域。由于颗粒很小，它们可以被注射-从而快速地为外科医生提供关于问题可能位于何处的信息。这些颗粒的潜在问题之一是稳定性。我们一直在与曼彻斯特药学院的同事合作，研究真实的纳米颗粒系统，但由于颗粒和链合成中使用的溶剂和分子的存在，表面结构变得复杂。在这项工作中，我们将使用原子清洁的表面和存款仔细控制量的纯儿茶酚。使用的里雅斯特Elettra的辐射设施，我们可以确定一些关于表面化学性质的事情，包括分子的取向及其在短时间尺度和不同条件下的稳定性。X射线光电子能谱和吸收光谱将用于确定化学性质随时间的变化。此外，使用X-射线吸收和光电发射的组合，我们能够推断吸附的分子和表面的TiO 2之间的电荷转移时间。我们将研究吸附两个不同的表面，即金红石（110）和金红石（101），这产生于不同的晶体结构的TiO 2。锐钛矿是纳米颗粒TiO 2所采用的结构，因此我们对这种晶体的研究将可能提供更真实的信息。金红石是一种更广泛研究的材料，因为它更容易生长和商业化。事实上，我们是少数几个对单晶表面进行了大量研究的小组之一。虽然我们在以前的工作中已经确定的一些建议有机酸分子以类似的方式在这两个表面上相互作用，但确定这是否也是儿茶酚的情况是一些基本的兴趣。此外，这两种不同的分子将使我们能够确定多巴胺上的侧链的存在是否导致吸附几何形状或化学稳定性的差异，因为该链可能与多巴胺结合到表面的氧分子发生潜在反应。