NLO and opto-optic switching of guest-loaded SURMOF-layers: Second-order optical effects

客体加载的 SURMOF 层的 NLO 和光电开关：二阶光学效应

• 批准号: 316710032
• 负责人: Professor Dr. Jürgen Caro
• 金额: --
• 依托单位: Max-Planck-Institut für Kohlenforschung
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/316710032?language=en
• 关键词: NLO; opto; optic; switching; guest

During the last few months, we have prepared a variety of SURMOF-based host guest systems and evaluated them in non-linear optics. The nano-composites were prepared on different supports by bringing different optically active molecules as guests into the pores of different SURMOFs by using different loading techniques from gas or liquid phase. The SURMOF layers of < 1 µm thickness were prepared by solvothermal synthesis, spraying, dipping and interfacial synthesis. However, these preparations scattered light. To get optically transparent non-scattering SURMOF layers of < 1 µm, we developed the „controlled injection technique“. After loading with optically active guest molecules, we measured the 2nd-order non-linear susceptibility chi(2) (via the Pockels effect) which is responsible for such non-linear optical effects like Second Harmonic Generation (SHG), Sum Frequency Generation (SFG), Difference Frequency Generation (DFG). Surprisingly, we found giant chi(2) data. The highest value of 337 pm/V was measured for p-nitroaniline (pNA) in the 1D pores of a sub-µm Cu-MOF-74 SURMOF layer on FTO glass. Such giant chi(2) values are so far unknown; highest experimental values and their theoretical explanation are one order of magnitude smaller. Very likely, the giant values can be only explained by a special uptake mechanism of the pNA into the 1D pores of Cu-MOF-74: Every pNA molecule must enter the pore in a certain orientation thus forming stable dipole chains inside the 1D pores. However, a theoretical estimate shows that this geometry of parallel dipole chains can give only a high chi(2) value which is about one order of magnitude smaller than the measured one. This means, the existence of domains of oriented dipole chains of pNA in the 1D Cu-MOF-74 alone cannot explain the giant chi(2) values. Therefore, there must be additional mechanisms to explain the giant chi(2) data such as (i) perfectly H-coupled chains, or (ii) counter dipole fields in the MOF lattice opposite the to dipole field of the pNA molecules. It will be, therefore, the aim of the project to give a molecular understanding of the oriented uptake and the resulting giant chi(2) values, and to develop a Tool Box for high chi(2) materials combining suitable supports (FTO, ITO, Si wafer), SURMOF structures, preparation techniques, and dye loading (from gas or liquid phase). The resulting non-linear optical materials will be tested in (i) Pockels effect, (ii) Kerr effect, (iii) opto-optical switching.

在过去的几个月里，我们已经准备了各种基于SURMOF的主客体系统，并在非线性光学中对其进行了评估。采用气相或液相不同的负载技术，将不同的光学活性分子作为客体引入不同的SURMOFs的孔中，在不同的载体上制备了纳米复合材料。通过溶剂热合成、喷涂、浸渍和界面合成制备厚度< 1 µm的SURMOF层。然而，这些准备工作分散了光线。为了获得< 1 µm的光学透明非散射SURMOF层，我们开发了“受控注入技术”。在负载光学活性客体分子后，我们测量了二阶非线性极化率chi（2）（通过Pockels效应），其负责诸如二次谐波产生（SHG）、和频产生（SFG）、差频产生（DFG）等非线性光学效应。令人惊讶的是，我们发现了巨大的chi（2）数据。在FTO玻璃上的亚微米Cu-MOF-74 SURMOF层的1D孔中测量对硝基苯胺（pNA）的最高值337 pm/V。 如此巨大的chi（2）值至今仍是未知的;最高的实验值和它们的理论解释都要小一个数量级。很可能，巨大的值只能通过pNA进入Cu-MOF-74的1D孔的特殊吸收机制来解释：每个pNA分子必须以一定的方向进入孔，从而在1D孔内形成稳定的偶极链。然而，理论估计表明，这种平行偶极链的几何形状只能给出比测量值小一个数量级的高chi（2）值。这意味着，在1D Cu-MOF-74中pNA的定向偶极链的结构域的单独存在不能解释巨大的chi（2）值。因此，必须有额外的机制来解释巨大的chi（2）数据，例如（i）完美的H-耦合链，或（ii）与pNA分子的偶极场相反的MOF晶格中的反偶极场。因此，该项目的目标是对定向吸收和由此产生的巨大chi（2）值进行分子理解，并开发一种用于高chi（2）材料的工具箱，该工具箱结合了合适的载体（FTO，ITO，Si晶片），SURMOF结构，制备技术和染料负载（从气相或液相）。所得到的非线性光学材料将在（i）Pockels效应、（ii）Kerr效应、（iii）光-光开关方面进行测试。