We
have studied the photopatterning of a gold surface functionalized
with a self-assembled monolayer of an o-nitrobenzyl-based
photouncaging ligand bound to the gold surface with a dual thiol anchor.
We find that the dose of UV light required to induce the photoreaction
on gold is very similar to the dose in an alcohol solution, even though
many optical phenomena are strongly suppressed on metal surfaces.
We attribute this finding to a combination of the large skin depth
in gold at UV wavelengths, the high speed of the photoreaction, and
the spatially indirect nature of the lowest excited singlet. Any photoreactive
compounds where the quantum efficiency of fluorescence is sufficiently
low, preferably no larger than about 10–5 in the
case of gold surfaces, will show a similarly high photoreactivity
in metal-surface monolayers.
In general, most of the substances in nature exist in mixtures, and the noninvasive identification of mixture composition with high speed and accuracy remains a difficult task. However, the development of Raman spectroscopy, machine learning, and deep learning techniques has paved the way for achieving efficient analytical tools capable of identifying mixture components, thus leading to an apparent breakthrough in the identification of mixtures beyond traditional chemical analysis methods. This review summarizes the work of Raman spectroscopy in identifying the composition of substances; reviews the preprocessing process of Raman spectroscopy, artificial intelligence analysis methods, and analysis procedures; and examines the application of artificial intelligence. Finally, the advantages and disadvantages and development prospects of Raman spectroscopy are discussed in detail.
The process of spontaneous emission can be dramatically modified by optical microstructures and nanostructures. We have studied the modification of fluorescence dynamics using a variable thickness polymer spacer layer fabricated using layer-by-layer self-assembly with nanometer accuracy. The change in fluorescence lifetime with spacer layer thickness agrees well with theoretical predictions based on the modified photonic density of states (PDOS), and yields consistent values for the fluorophores' intrinsic fluorescence lifetime and quantum yield near a dielectric as well as a plasmonic interface. Based on this observation, we further demonstrate that self-assembled fluorophores can be used to probe the modified PDOS near optical microstructures and nanostructures.
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