• Tue. Nov 28th, 2023

    Critical Thought

    Critical thoughts on quantum technologies

    The Fascinating Chemistry Behind Silica-Coated Nanodiamonds Revealed

    ByByron Bekker

    Nov 20, 2023
    The Fascinating Chemistry Behind Silica-Coated Nanodiamonds Revealed

    Coating nanodiamonds with silica, the primary component of sand, may seem unconventional, but the results of this unique combination have proven to be invaluable in various fields. However, until now, the precise bonding mechanism between these two materials has remained elusive.

    In a new study published in the journal ACS Nanoscience Au, researchers from San Jose State University (SJSU) have uncovered the key bonding mechanism responsible for creating uniformly coated silica shells on nanodiamonds. This breakthrough has the potential to enhance the development of silica-coated nanodiamonds, which have applications ranging from biolabeling cancer cells to quantum sensing.

    The research team relied on the powerful X-ray capabilities provided by the Stanford Synchrotron Radiation Lightsource (SSRL) at the SLAC National Accelerator Laboratory to unravel the intricate chemistry behind the bonding process. By obtaining finer details about the mechanism, the researchers can now explore new diamond hybrid systems with greater precision and accuracy.

    Nanodiamonds are minuscule fragments of synthetic diamonds, each small enough that it would take 40,000 of them to span the width of a single human hair. While nanodiamonds typically possess perfect carbon lattices, occasional defects occur when a nitrogen atom replaces a neighboring carbon atom. Interestingly, these defects enable nanodiamonds to respond to various stimuli, including magnetic fields, electric fields, and light, all at room temperature.

    The introduction of silica coatings resolves two significant challenges associated with nanodiamonds. Firstly, the silica forms a smooth and uniform shell that eliminates the sharp edges of the diamond. This property is especially essential when working with delicate biological samples, as the coated nanodiamonds are less likely to rupture cell membranes. Secondly, the silica coating provides a customizable surface on which scientists can attach specific tags or markers, allowing precise targeting of the nanodiamonds to specific cells or structures.

    For many years, the scientific community has debated the exact process through which the silica shell forms. However, the SJSU research team managed to shed light on this mystery. They discovered that a combination of ammonium hydroxide and ethanol, typically employed in the coating process, generates alcohol groups on the nanodiamond surface. These alcohol groups play a crucial role in facilitating the growth of the silica shell.

    To gain a deeper understanding of the coating process, the researchers utilized two key techniques. First, they employed transmission electron microscopes at the Lawrence Berkeley National Laboratory Molecular Foundry to visualize the particles and their surfaces. Subsequently, they used the SSRL X-ray facilities to investigate the hidden surfaces beneath the silica coating.

    By employing a state-of-the-art transition edge sensor developed by SSRL, the researchers were able to detect which chemical groups were present on the nanodiamonds’ surfaces. Additionally, they utilized X-ray absorption spectroscopy (XAS) to generate electrons on the nanodiamond surface and monitor their movement through the silica shell. The thickness of the coating influenced the number of electrons that reached the surface, thereby serving as a measuring tape on the nanometer scale.

    This groundbreaking study not only unraveled the complex bonding mechanism between nanodiamonds and silica but also demonstrated the usefulness of XAS for material scientists and chemists in studying submerged materials.

    Looking ahead, the researchers are eager to continue their investigations by exploring the use of alternative materials for coating nanodiamonds, such as titanium, zinc, and other metal oxides. These advancements could pave the way for new possibilities in fields like quantum sensing and biological labeling applications.

    With a comprehensive understanding of how silica shells form on nanodiamonds, researchers can optimize the coating process and expand the range of materials used. This newfound knowledge opens up countless opportunities for leveraging the incredible potential of nanodiamonds in various scientific and technological endeavors.


    1. What are nanodiamonds?

    Nanodiamonds are minuscule fragments of synthetic diamonds that possess unique properties due to defects in their carbon lattice structure. Despite their small size, nanodiamonds have applications in quantum computing, biolabeling, and sensing.

    2. How does coating nanodiamonds with silica benefit their applications?

    Silica coatings on nanodiamonds provide several advantages. Firstly, the silica creates a smooth and uniform shell that eliminates the diamond’s sharp edges, making them safer to use in biological samples. Secondly, the silica coating allows for precise targeting and customization by attaching specific tags or markers to the nanodiamond surface.

    3. How did researchers uncover the bonding mechanism between nanodiamonds and silica?

    Using powerful X-ray techniques, researchers from San Jose State University (SJSU) examined the surfaces of nanodiamonds beneath the silica coating. The team utilized specialized sensors and spectroscopy methods to observe the movement of electrons through the silica shell and determine its thickness.

    4. What are the potential future applications of nanodiamonds?

    Beyond their current applications in quantum computing and biolabeling, nanodiamonds hold promise for advancements in quantum sensing and biological labeling using alternative coating materials such as titanium and zinc.

    5. What is X-ray absorption spectroscopy (XAS)?

    X-ray absorption spectroscopy (XAS) is an analytical technique that uses X-rays to probe the electronic structure of materials. It provides valuable insights into the composition, bonding, and properties of substances.