Nicholas Nunn

Visible to near-IR fluorescence from single-digit detonation nanodiamonds: excitation wavelength and pH dependence

Detonation nanodiamonds are of vital significance to many areas of science and technology. However, their fluorescence properties have rarely been explored for applications and remain poorly understood. We demonstrate significant fluorescence from the visible to near-infrared spectral regions from deaggregated, single-digit detonation nanodiamonds dispersed in water produced via post-synthesis oxidation. The excitation wavelength dependence of this fluorescence is analyzed in the spectral region from 400 nm to 700 nm as well as the particles’ absorption characteristics. We report a strong pH dependence of the fluorescence and compare our results to the pH dependent fluorescence of aromatic hydrocarbons. Our results significantly contribute to the current understanding of the fluorescence of carbon-based nanomaterials in general and detonation nanodiamonds in particular.

Commercial quantities of ultrasmall fluorescent nanodiamonds containing color centers

Optically active nanodiamond particles remain one of the most popular research topics due to the photoluminescent properties of crystallographic defects in the diamond lattice, referred to as color centers. A number of groups are currently undertaking efforts to commercialize this material. Recently, our group succeeded in large-scale production of fluorescent diamond particles containing nitrogen-vacancy (NV) color centers in hundred-gram per batch scales using irradiation with 2-3 MeV electrons. Production of ND-NV fractions with median sizes ranging between 10 nm and 100 nm was achieved. While 100 nm fluorescent nanodiamonds (FNDs) are ~10x brighter than a conventional dye (Atto 532), the brightness of FNDs drops with decreasing particle size. Because of this, significant efforts must be undertaken to elucidate the size/brightness compromise and identify relevant application niches for FND in bioimaging and biolabeling. In order for a new material to be considered for applications in the overcrowded optical reagent market, the reagent must be convenient to use by an end user from the biomedical community, be validated both in vitro and in vivo, and offer measurable and significant (rather than incremental) benefit to end users in specific applications. This paper reports on the characteristics of the ultrasmall (10-40nm) and larger fluorescent nanodiamonds as well as our efforts toward their adaptation for use in the biological science community.

A phantom study of terahertz spectroscopy and imaging of micro- and nano-diamonds and nano-onions as contrast agents for breast cancer

THz imaging is effective in distinguishing between cancerous, healthy, and fatty tissues in breast tumors, but a challenge remains in the contrast between cancerous and fibroglandular (healthy) tissues. This work investigates carbon-based nanoparticles as potential contrast agents for terahertz imaging of breast cancer. Microdiamonds, nanodiamonds, and nanometer-scale onion-like carbon are characterized with terahertz transmission spectroscopy in low-absorption backgrounds of polydimethylsiloxane or polyethylene. The refractive index and absorption coefficients are calculated based on the measured electric fields. Nanodiamonds show little effect on the terahertz signal, microdiamonds express resonance-like, size-dependent absorption peaks, and onion-like carbon provides a uniform increase in the optical properties even at low concentration. Due to its strong interaction with terahertz frequencies and ability to be activated for selective binding to cancer cells, onion-like carbon is implemented into engineered three-dimensional breast tumor models composed of phantom tissue mimicking infiltrating ductal carcinoma surrounded by a phantom mimicking healthy fibroglandular tissue. This model is imaged using the terahertz reflection mode to examine the effectiveness of contrast agents for differentiation between the two tissue types. In both spectroscopy and imaging, a 10% concentration of onion-like carbon shows the strongest impact on the terahertz signal and holds promise as a terahertz contrast agent.

Fluorescent single-digit detonation nanodiamond for biomedical applications

Detonation nanodiamonds (DNDs) have emerged as promising candidates for a variety of biomedical applications, thanks to different physicochemical and biological properties, such as small size and reactive surfaces. In this study, we propose carbon dot decorated single digit (4-5 nm diameter) primary particles of detonation nanodiamond as promising fluorescent probes. Due to their intrinsic fluorescence originating from tiny (1-2 atomic layer thickness) carbonaceous structures on their surfaces, they exhibit brightness suitable for in vitro imaging. Moreover, this material offers a unique, cost effective alternative to sub-10 nm nanodiamonds containing fluorescent nitrogen-vacancy color centers, which have not yet been produced at large scale. In this paper, carbon dot decorated nanodiamonds are characterized by several analytical techniques. In addition, the efficient cellular uptake and fluorescence of these particles are observed in vitro on MDA-MD-231 breast cancer cells by means of confocal imaging. Finally, the in vivo biocompatibility of carbon dot decorated nanodiamonds is demonstrated in zebrafish during the development. Our results indicate the potential of single-digit detonation nanodiamonds as biocompatible fluorescent probes. This unique material will find application in correlative light and electron microscopy, where small sized NDs can be attached to antibodies to act as a suitable dual marker for intracellular correlative microscopy of biomolecules.

Production and purification of nanodiamonds

Abstract Nanodiamond is one of the few carbon nanomaterials that has a well-established industrial production capacity. When this is paired with its outstanding application breadth, ranging from lubricants to biomarkers, it is no surprise that nanodiamond has an ever growing popularity in both the commercial and research sectors. Works performed primarily in the past 20–30 years in the synthesis and purification stage have made large volumes of sub-50 nm (including dispersions of 5 nm DNDs) nanodiamond a reality. At this intersection of commercial and academic interest that is currently overtaking the nanodiamond community, there is perhaps no better time to push boundaries on what has been previously done to maximize the success of nanodiamonds throughout the world. The greatest challenges in effective synthesis, purification, and disaggregation are still open for more creative solutions that are cleaner, cost effective, and even more efficient. With a number of interesting challenges ahead, and a clear and growing commercial demand, there is no other nanomaterial with as bright a future as nanodiamond.

Atomic and Electronic Structures of Functionalized Nanodiamond Particles

1. LeRoy Eyring Center for Solid State Science, Arizona State University, Tempe, AZ 85287, United States. 2. Department of Physics, Arizona State University, Tempe, AZ 85287, United States. 3. Universite Grenoble Alpes, and CNRS, LEPMI, F-38000 Grenoble, France. 4. International Technology Center, 8100 Brownleigh Dr., Raleigh, North Carolina 27617, United States .NanoCarbon Research Institute, Ueda, Japan. 6. Virtual Nanoscience Laboratory, CSIRO, Parkville, Australia.