Recent advancements in high temperature rapid thermal annealing (RTA) of irradiated diamond particles has made possible the production of the particles with fluorescence based on complexes of nitrogen and vacancies in a broad range of colors: blue, green, red/NIR as well as their mixtures, depending on the temperature and irradiation fluence. Still, the production of fluorescent diamond particles suffers from fluorescence inhomogeneity among particles. The goal of the current study is improvement of the fluorescence uniformity among the treated particles. Experiments were performed using as-grown 40 mu m in diameter type Ib synthetic diamond particulate assuming that nitrogen uniformity among the as-grown particles should be higher versus milled ones used in previous studies. Particles were irradiated under mild conditions with 1 MeV electrons to a fluence 3 x 10(18) e/cm(2) without overheating during irradiation which resulted in relatively uniform green fluorescence among particles treated via RTA at temperatures corresponding to H3 centers formation.

Terahertz (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 THz imaging of breast cancer. Microdiamonds, nanodiamonds (NDs), and nanometer-scale onion-like carbon (OLC) are characterized with THz transmission spectroscopy in low-absorption backgrounds of polydimethylsiloxane or polyethylene. The refractive index and absorption coefficients are calculated based on the measured electric fields. NDs show little effect on the THz signal, microdiamonds express resonance-like, size-dependent absorption peaks, and OLC provides a uniform increase in the optical properties even at low concentration. Due to its strong interaction with THz frequencies and ability to be activated for selective binding to cancer cells, OLC 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 THz 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 OLC shows the strongest impact on the THz signal and holds promise as a THz contrast agent.

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 similar to 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.

Paramagnetic triplet centers produced by e-beam irradiation of synthetic microcrystalline Ib-type high-pressure high-temperature (HPHT) diamonds were studied by continuous wave (CW) electron paramagnetic resonance (EPR) spectroscopy at X-band (9.4 GHz), pulsed EPR at X- and Q-bands (34 GHz), and fluorescence spectroscopies as a function of radiation fluences up to 5 × 1019 e–/cm2. EPR spectra of mostly “forbidden” Δms = 2 electronic spin transitions observed at g ≈ 4 (i.e., so-called half-field EPR spectra) reveal the presence of the main W15 triplet defects associated with the fluorescent negatively charged nitrogen-vacancy (NV–) centers as well as additional triplet spin centers identified as W16, W17, W18, and W33 that appear upon increasing the e-beam fluence. Consequent annealing at 1,400 °C significantly reduces the content of W17, W18, and W33 but not W15 and W16 defects. The efficacy of NV– center fabrication as a function of fluence dependent e-beam irradiation is also reported.

A method for forming a carbon nanotube (CNT) reinforced copper (Cu) composite by an electrodeposition process has been developed. Nanoscale diamond particles were introduced as a dispersing agent to prevent aggregation of carbon nanotubes while performing electrodeposition, or what is commonly referred to as electroplating. The technique involves co-deposition of Cu and CNTs in an electroplating process that uses both direct current and a sequence of forward and reverse pulses. Reverse pulse times were varied in order to examine parameters for dispersion of carbon nanotubes in the resultant composite material. Electrical resistivity, surface morphology, and composite structure were investigated using a probe station, scanning electron microscopy, and x-ray diffraction, respectively. Experimental results show carbon nanotubes can be dispersed uniformly in a Cu/CNT composite due to the role played by the nanodiamond particles in CNT de-aggregation. Direct current electrodeposition yields high deposition rates while reverse pulse electrodeposition is a slower process although necessary for providing a higher percentage of CNTs integrated into the composite.

Diamond nanoparticles occupy a special niche among nanomaterials due to their combination of outstanding mechanical performance, chemical resistance, biocompatibility, and unique optical and electronic properties. In this review a brief survey of the different classes of nanodiamond particles based on synthesis method and associated structural features is provided. Then major structural features of ND particles (size, shape, crystallographic core, surface chemistry, internal defects/dopants, and presence of sp(2) carbon) are discussed as well as their connection with ND properties and related applications. In conclusion current opportunities in the fields of production and processing of nanodiamond particles and the outlook for the future of the field are critically discussed. (C) 2016 Elsevier Ltd. All rights reserved.

Poly(ethylene terephthalate) (PET) nanocomposite film with 1 wt % of nanodiamonds terminated with carboxylic groups (PET- ND COOH ), PET nanocomposite film containing 1 wt% of ND COOH and 0.3 wt % nanographene platelets (PET- ND COOH -NGP) and a neat PET film were prepared by melt extrusion. Raman spectroscopy was performed in order to establish the interactions between the nanofiller (ND COOH and nanographene platelets (NGPs)) and polymer matrix. The thermal behaviour of the PET nanocomposites was studied using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Mechanical properties were determined by tensile tests performed on strips cut from the prepared films in directions parallel and perpendicular to the direction of film preparation. Raman spectroscopy and DSC results showed that incorporation of ND COOH and NGPs into the composite enhances crystallinity, inducing the growth of crystals in the polymer matrix. According to TGA results, the addition of ND COOH and NGP enhanced thermal stability. The results obtained from the tensile strength tests in the longitudinal direction showed that incorporation of ND COOH particles resulted in matrix plasticization. The increase in stiffness in the transversal direction can be ascribed to interactions between ND COOH and the PET matrix. The tensile strenght of PET-ND COOH -NGP nanocomposite film in both directions decreased in comparison to neat PET.

Diamond has outstanding bulk properties such as super hardness, chemical inertness, biocompatibility, luminescence, to name just a few. In the nanoworld, in order to exploit these outstanding bulk properties, the surfaces of nanodiamond (ND) particles must be accordingly engineered for specific applications. Modification of functional groups on the ND's surface and the corresponding electrostatic properties determine their colloidal stability in solvents, formation of photonic crystals, controlled adsorption and release of cargo molecules, conjugation with biomolecules and polymers, and cellular uptake. The optical activity of the luminescent color centers in NDs depends on their proximity to the ND's surface and surface termination. In order to engineer the ND surface, a fundamental understanding of the specific structural features and sp(3)-sp(2) phase transformations on the surface of ND particles is required. In the case of ND particles produced by detonation of carbon containing explosives (detonation ND), it should also be taken into account that its structure depends on the synthesis parameters and subsequent processing. Thus, for development of a strategy of surface modification of detonation ND, it is imperative to know details of its production. In this review, the authors discuss ND particles structure, strategies for surface modification, electrokinetic properties of NDs in suspensions, and conclude with a brief overview of the relevant bioapplications.

SummaryIn this study poly(dimethylsiloxane) (PDMS) nanocomposites with 1wt % of zinc oxide (ZnO) and 1wt % of silanized ZnO nanoparticles were prepared through cross‐linking reaction. The prepared samples were irradiated under vacuum at room temperature with a 2 MeV proton beam with fluences in the 1013–1015 cm−2 range. The influence of nanoparticles on the cross‐linking processes and structural degradation of irradiated PDMS nanocomposites was investigated using Raman and Fourier transform infrared spectroscopy (ATR). The analysis of vibrational spectra has shown that prepared PDMS nanocomposites have higher resistance to proton irradiation in comparison to pristine PDMS. Under the highest proton irradiation fluence (1015 cm−2) PDMS with 1 % ZnO provided the best radiation protection.

We report on the characterization of thin-film near and short wavelength infrared absorbers comprised of carbon nanotubes dispersed in a polymer. Charged nanodiamond particles are used to effectively and uniformly disperse the carbon nanotubes in the polymer matrix, leading to a very homogenous film. Using this new technique, we demonstrate an infrared absorption of up to 95% in films with thicknesses . This remarkably high absorption is the result of low reflection off the surface and high absorption across the film thickness. The complex refractive index of the films is extracted using an effective media approximation. Calculations show the film has a wide angle for high absorption and is polarization independent. These films are easy to fabricate, robust and damage-resistant, and are compatible with post-processing techniques. These films can be used as the coating layer to boost the efficiency of uncooled infrared sensors and solar-thermal energy harvesters.

This paper reports on the fabrication and characterization of thin-film nanocomposites comprised of tangled carbon nanotubes in a polymer matrix. The concentration of nanotubes in the polymer was significantly increased using detonation nanodiamonds. Nanodiamonds reduce the surface forces between the polymer and the nanotubes and mitigate the agglomeration problem of nanotubes in polymer. This resulted in thinner and more uniform networks that are efficient absorbers of infrared energy over a broad spectrum, ranging from the visible to the mid-wavelength infrared. An infrared absorbance of 97% was achieved for a 1.6 μm thick nanocomposite film across the spectral range of 714 nm to 5 μm. The films are mechanically and thermally stable up to 300 °C, and can be integrated with microbolometers to enhance their responsivity.

In the present study, three different nanocomposites of poly(dimethylsiloxane) (PDMS) with 1 wt. % of nanoparticles of detonation nanodiamond (DND) (PDMS-DNDS), zinc oxide (ZnO) (PDMS-ZnO), and single-walled carbon nanotubes (SWNTs) (PDMS-SWNTs) were irradiated under vacuum at room temperature with a 2 MeV proton beam with fluences in the 1013–1015 cm−2 range. Modification of the structures and properties of the nanocomposite materials were monitored as a function of proton fluence. Specifically, the vibrational dynamics of PDMS nanocomposites for unirradiated and irradiated samples were investigated using Raman and Fourier transform infrared spectroscopy in the attenuated total reflection mode (FTIR-ATR) and compared. The results were also compared with the results obtained for the unirradiated/irradiated pure PDMS polymer. The Raman and FTIR-ATR spectra of the PDMS nanocomposites exhibit an overall reduction in intensity of the characteristic vibrational bands of the irradiated samples. However, an important difference between the irradiated pure PDMS versus PDMS nanocomposites’ Raman and FTIR spectra appeared; comparable structural degradation of polymer nanocomposites with ZnO, DND, and SWNT fillers takes place at least at 1 or even 2 orders of magnitude higher fluence than for pure PDMS, indicating the potential use of ZnO-based, DND-based, and SWNT-based polymer composites in high radiation environments. The highest resistance to radiation was demonstrated for PDMS-ZnO samples. Since the benefit is realized at a low loading, the cost of the nanocomposite can be kept low and the polymer retains the other beneficial properties that make them attractive.

Pure poly(dimethylsiloxane) (PDMS) films, PDMS–nanodiamond (ND) and pure nanodiamond powder were irradiated with 2 MeV protons under a variety of fluence and current conditions. Upon proton irradiation, these samples acquire a fluence-dependent photoluminescence (PL). The emission and excitation spectra, photostability and emission lifetime of the induced photoluminescence of PDMS and PDMS–ND samples are reported. Pure PDMS exhibits a noticeable stable blue PL, while the PDMS–ND composites exhibit a pronounced stable green PL under 425 nm excitation. The PL of PDMS–ND composites is much more prominent than that of pure PDMS or pure ND powder even when irradiated at higher doses. The origin of the significantly enhanced PL intensity for the proton-irradiated PDMS–ND composite is explained by the combination of enhanced intrinsic PL within ND particles due to ion-implantation-generated defects and by PL originating from structural transformations produced by protons at the nanodiamond/matrix interface.