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In this section we would like to present the most important aspects of our project once more and discuss the outcome of our work. Apart from this we would like to give an outlook on future projects based on our results beyond BIOMOD.

Goals reached

When assessing the project, it is essential to compare previously defined goals with the actual results. Inspired by the idea of developing a self-assembling single photon source, we decided to focus on one essential and so far unsolved problem as a feasible goal for one summer:
The development of a method to functionalize the surface of nanodiamonds. Such a functionalization has to fulfill three conditions:

  1. It has to be biocompatible to allow a future in vivo use.
  2. The functionalized nanodiamonds must offer surface groups which can be linked to specific docking sites of the DNA origami.
  3. The functionalization should cause the nanodiamonds to be well dispersed, as single nanodiaomds should be attached to DNA origami.

We were able to reach all of those aims:

All materials used are fully biocompatible and are intended for a use under physiological conditions. The nanodiamonds are well dispersed. Therefore they could be bound specifically to the 6HB structure we designed. Those result were verified by TEM measurements. We are happy to be able to report successful specific binding of functionalized nanodiamonds to DNA origami for the very first time.

Normalized emission(red) and excitation(blue) spectra taken by FluoroLog
Normalized emission(red) and excitation(blue) spectra taken by FluoroLog

After providing the proof of principle of our approch, we already made some progress in improving the yield of our method. In the last samples we reached a yield of approximately 10% of structures with two diamonds while 50% showed at least one attachment.

Additionally we were already able to roughly determine the excitation and emission spectra of the used fluorescence diamonds. The excitation wavelength lies at 535nm, whereas the emission wavelength lies at 650nm. So the NVCs can be easily excited since commonly used laser systems such as doubled Nd:YAG work at a wavelength of 532nm. All this fluorescence measurements were taken by FluoroLog.

Next steps

Model of the self assembling nanodiamond gold hybrid structure
Model of the self assembling nanodiamond gold hybrid structure

Since the initial motivation of the project was based on realizing diamond nanoparticles hybrid structures in a self assembling way we are already planning the next steps. To accomplish this we will work together with Prof. Högele’s group which has the expertise and equipment available that is necessary for both detailed optical characterization and single photon measurements at the nano-scale.

The long term objective is to synthesize a 6HB structure with nanodiamonds surrounded by goldnanoparticles on both sides. A visualization of the structure setup is shown on the picture to the right.
With this in mind we first tried to make some fluorescence pictures of the assembled nanodiamond 6HB structures. But the spectrum of the emission turned out to be a problem, since it is not in the measurement range of the fluorescence microscope available. However, we are confident to find a solution for this problem with the the cooperation of Prof. Högele. After that we will be able to conduct the first single photon measurements which constitute the basis for the interpretation of the following experiments with goldnanoparticles-nanodiamonds arrangements. Regarding this we have already conducted some first experiments adding gold particles to structures developed by us. Unfortunatly the goldparticles clustered with the nanodiamonds and thus inhibited the specific attachment to the 6HB. But once we overcome this last obstacle we should be able to assemble the proposed nanodiamond gold hybrid structure similar to the one used in the paper of Schietinger et al. in a self assembling way.

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