Diamond Surface Homogenization And Modification

Magnetic resonance is a useful means to characterize the composition and structural information of matter.It’s widely used in physics,biology,chemistry,and materials.However,limited by the measurement method for magnetic detection,the traditional magnetic resonance technique can only detect the signal accumulated from billions of molecules.It is important to enhance its sensitivity of magnetic measurement in order to obtain the single molecule’s signal.Nitrogen-vacancy defect in diamond,a magnetic quantum sensor,makes it possible.Before using the NV center to probe the electron or nuclear spin of a molecule,attaching the target molecule to the diamond must be done first.It’s common to make use of carboxyl groups on the diamond surface for covalent modification,but the density of the modification is low,which results in that only a few NV centers can probe the signal from the sample.So the bulk diamond needs to be modified with higher surface density.Nanodiamond(ND),as a microscopic form of diamond,can possesse NV centers,too.This provides it with stable fluorescence and quantum sensing function.In addition,ND is very small and biocompatible,and its surface is easy to be functionalized,which makes it well suited for biological applications.For in vivo biological applications,the entry of ND into cells is the primary condition.If the surface purity and uniformity of ND are low,it is often prone to agglomeration,resulting in the NDs becoming too large to be taken up by cells.Therefore,the ND’s surface needs to be homogenized to promote its dispersion.To boost the research on the NV center for the magnetic resonance detection of biomolecules on the one hand,and to promote the biological application of NDs on the other hand,this paper mainly involves the following works:(1)Trifluoroacetic acid-protected 10-aminodecene(TFAAD)was synthesized organically from non-toxic raw materials at first.And it was immobilized onto the bulk diamond by photochemical reaction then.The spacing between the modified TFAAD molecules is less than 3 nm,which is one order of magnitude smaller than the modification obtained by covalent modification based on surface carboxyl groups.In addition,the thickness of the molecular layer is 0.2～0.4 nm.(2)Methods to increase the concentration of NV centers in ND and enhance surface homogenization were both explored.After the treatment,the brightness of the particles was increased and the transparent and stable nanodiamond dispersion was obtained,which provides the basic material for applying ND in bioimaging,drug delivery and other biological fields.(3)A wide-field optically detected magnetic resonance measurement system was established by extending the commercial microscope with a laser optical path,microwave circuit,and pulse timing control.It can be realized that detecting all NDs within an 80 × 80μm2 field of view simultaneously on this platform,which allows for further investigation into the biological applications of NDs.