A new phase transformation path from nanodiamond to new-diamond via an intermediate carbon onion

Abstract

The investigation of carbon allotropes such as graphite, diamond, fullerenes, nanotubes and carbon onions and mechanisms that underlie their mutual phase transformation is a long-standing problem of great fundamental importance. New diamond (n-diamond) is a novel metastable phase of carbon with a face-centered cubic structure; it is called "new diamond" because many reflections in its electron diffraction pattern are similar to those of diamond. However, producing n-diamond from raw carbon materials has so far been challenging due to n-diamond's higher formation energy than that of diamond. Here, we, for the first time, demonstrate a new phase transformation path from nanodiamond to n-diamond via an intermediate carbon onion in the unique process of laser ablation in water, and establish that water plays a crucial role in the formation of n-diamond. When a laser irradiates colloidal suspensions of nanodiamonds at ambient pressure and room temperature, nanodiamonds are first transformed into carbon onions serving as an intermediate phase, and sequentially carbon onions are transformed into n-diamonds driven by the laser-induced high temperature and high pressure from the carbon onion as a nanoscaled temperature and pressure cell upon the process of laser irradiation in a liquid. This phase transformation not only provides new insight into the physical mechanism involved, but also offers one suitable opportunity for breaking controllable pathways between n-diamond and carbon allotropes such as diamond and carbon onions.

<p>Carbon Quantum Dots: In vitro and in vivo Studies on Biocompatibility and Biointeractions for Optical Imaging</p>

“…In this study, the CQDs were synthesized by the LAL process, as reported by our group, [19][20][21][22] and then characterized. Figure 1A is an AFM image showing the morphology of CQDs.…”

“…The synthesis of CQDs using the LAL protocol was performed as previously described, [19][20][21][22] the process is in the Supplementary Materials section of the supplementary information.…”

“…To the best of our knowledge, until now, there are no comprehensive data on the biointeractions, biodistribution, and immunotoxicity of CQDs, as reported by our group. [19][20][21][22] In addition, a lack of risk assessments on their immunotoxicity and insufficient data relating to their optical imaging in vitro and in vivo have prevented the preclinical application of CQDs. The main challenge for these studies is the precise detection of CQDs and establishing their interactions with biological systems.…”

“…17,18 In the past, our group has successfully prepared CQDs by laser ablation in liquid (LAL), as they are potential optical nanoprobes. [19][20][21][22] In this paper, we extended the study of those CQDs by undertaking comprehensive preclinical research using cells and zebrafish. We systematically investigated the following: ⅰ. Biocompatibility in vitro, including cytotoxicity and apoptosis; ⅱ.Biodistribution in vitro, using scanning electron microscopy, transmission electron microscopy (TEM), and confocal imaging; ⅲ. Immunotoxicity in vivo, including the levels of reactive oxygen species (ROS) and multiple cluster of differentiation (CD) markers in peripheral blood, and the relative expression of genes related to immunotoxicity in the liver; ⅳ. Biointeractions between CQDs and intracellular proteins using fluorescence lifetime imaging (FLIM); ⅴ. Optical confocal imaging of zebrafish.…”

Enhanced strength of nano-polycrystalline diamond by introducing boron carbide interlayers at the grain boundaries

“…carbon nanotubes, C 60 , glassy carbon, onion-like boron nitride and graphite) at extreme high pressure and high temperatures (HPHT). [21][22][23][24][25] A breakthrough was achieved by Tian's group in the fabrication of nt-diamond which is about two-fold harder than natural diamond, together with higher fracture toughness (15 MPa m 0.5 ) and in-air oxidation temperature. 3 Extensive experimental and theoretical studies had been devoted to further strengthening polycrystalline superhard materials, involving controlled creation of composted phases, internal defects, stacking faults and interface boundaries.…”