Multi-photon patterning of photoactive o-nitrobenzyl ligands bound to gold surfaces,Photochemical & Photobiological Sciences

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Multi-photon patterning of photoactive o-nitrobenzyl ligands bound to gold surfaces
Photochemical & Photobiological Sciences ( IF 2.7 ) Pub Date : 2018-10-15 00:00:00 , DOI: 10.1039/c8pp00346g
Brenden A. Magill _{1,

2,

3} , Xi Guo _{2,

3,

4,

5} , Cheryl L. Peck _{2,

3,

4,

5} , Roberto L. Reyes _{1,

2,

3} , Erich M. See _{1,

2,

3} , Webster L. Santos _{2,

3,

4,

5} , Hans D. Robinson _{1,

2,

3}

Affiliation

We quantitatively investigate lithographic patterning of a thiol-anchored self-assembled monolayer (SAM) of photocleavable o-nitrobenzyl ligands on gold through a multi-photon absorption process at 1.7 eV (730 nm wavelength). The photocleaving rate increases faster than the square of the incident light intensity, indicating a process more complex than simple two-photon absorption. We tentatively ascribe this observation to two-photon absorption that triggers the formation of a long-lived intermediate aci-nitro species whose decomposition yield is partially determined either by absorption of additional photons or by a local temperature that is elevated by the incident light. At the highest light intensities, thermal processes compete with photoactivation and lead to damage of the SAM. The threshold is high enough that this destructive process can largely be avoided, even while power densities are kept sufficiently large that complete photoactivation takes place on time scales of tens of seconds to a few minutes. This means that this type of ligand can be activated at visible and near infrared wavelengths where plasmonic resonances can easily be engineered in metal nanostructures, even though their single-photon reactivity at these wavelengths is negligible. This will allow selective functionalization of plasmon hotspots, which in addition to high resolution lithographic applications would be of benefit to applications such as Surface Enhanced Raman Spectroscopy and plasmonic photocatalysis as well as directed bottom-up nanoassembly.

中文翻译：

结合到金表面的光活性邻硝基苄基配体的多光子图案

我们通过在1.7 eV（730 nm波长）处的多光子吸收过程，对金上可光裂解的邻硝基苄基配体的硫醇锚定自组装单分子层（SAM）的光刻图案进行了定量研究。光解速率的增加快于入射光强度的平方，这表明该过程比简单的双光子吸收更为复杂。我们暂时将此观察结果归因于双光子吸收，这触发了长寿命中间体aci的形成-硝基物种，其分解产率部分取决于吸收其他光子或入射光所引起的局部温度升高。在最高的光强度下，热过程会与光激活竞争，从而导致SAM损坏。该阈值足够高，即使功率密度保持足够大以至于在数十秒到几分钟的时间范围内发生完全的光活化，也可以在很大程度上避免这种破坏性过程。这意味着这种类型的配体可以在可见光和近红外波长处被激活，尽管可以忽略不计在这些波长下的单光子反应性，但可以在金属纳米结构中轻松进行等离子共振。这将允许等离子体激元热点的选择性功能化，

更新日期：2018-10-15

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