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Understanding materials with dimensions down to a few nanometers is of major importance for fundamental science as well as prospective applications. Structural transformation and phonon-confinement...

Detonation nanodiamonds (DND), their properties and deaggregation remain an active field of research. Here we innovated the salt-assisted ultrasonic deaggregation (SAUD) by employing NaHCO3 (a milling agent with relatively low solubility) followed by dialysis (a purification step) and processed two DND and one laser-synthesized (LND) commercial powders. The obtained ND colloids were separated to single-digit supernatant with the yield of 57–65% and sediment fractions by centrifugation and analyzed separately. By thermal analysis we evidenced chemical sensitization of the SAUD-processed DNDs manifested by significantly lower combustion temperatures. By correlation of spectroscopic, microscopic, and thermal analysis techniques we revealed a size and shape inhomogeneity of primary DND particles, also affecting strength of aggregation. By elemental analysis of the fractions we also show that nitrogen content is systematically higher in the smaller primary DND particles. Those features are inherent to all the three ND samples. The provided analyses highlight the need for better understanding of relations between detonation synthesis parameters and properties of the synthesized DNDs in terms of DND primary particle size, aggregation and nitrogen incorporation.

Ultra-small nanoparticles of a size smaller than or comparable to cell membrane pores (1–5 nm) offer significant potential in the field of biomedicine. This study presents a systematic in vitro investigation of fundamental bio-chemical interactions of such ultra-small hydrogenated and oxidized detonation nanodiamonds (DNDs) with biomolecules and human cells. We apply mass spectrometry methods (LC-MS/MS) for the qualitative and quantitative analysis of the protein corona as a function of the surface chemistry and size of DNDs. We observe that protein interactions with DNDs are more related to their surface chemistry (H/O-termination) rather than size. Bioinformatics characterization of the identified proteins points to the strong influence of electrostatic interaction between proteins and DNDs depending on their termination. Such specific interaction leads to formation of different protein corona on 2 nm DNDs, which influences also interaction with cells including different level of cytotoxicity.

Apart from the frequently used high-temperature annealing of detonation nanodiamonds (DNDs) in an inert environment, laser irradiation of DNDs in a liquid can be effectively used for onion-like carbon (OLC) formation. Here, we used fully de-aggregated hydrogenated DNDs (H-DNDs) dispersed in ethanol, which were irradiated for up to 60 min using a 532 nm NdYAG laser with an energy of 150 mJ in a pulse (5 J/cm2) at a pulse duration of 10 ns and a repetition rate of 10 Hz. We investigated the DND surface chemistry, zeta potential, and structure as a function of laser irradiation time. Infrared spectroscopy revealed a monotonical decrease in the C–Hx band intensities and an increase of the C–O and C=O features. Transmission electron microscopy (TEM) revealed the formation of OLC, as well as a gradual loss of nanoparticle character, with increasing irradiation time. Surprisingly, for samples irradiated up to 40 min, the typical and unchanged DND Raman spectrum was recovered after their annealing in air at 450 °C for 300 min. This finding indicates the inhomogeneous sp3 to sp2 carbon transformation during laser irradiation, as well as the insensitivity of DND Raman spectra to surface chemistry, size, and transient structural changes.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Color centers in diamonds have shown excellent potential for applications in quantum information processing, photonics, and biology. Here we report chemical vapor deposition (CVD) growth of nanocrystalline diamond (NCD) films as thin as 5–6 nm with photoluminescence (PL) from silicon-vacancy (SiV) centers at 739 nm. Instead of conventional 4–6 nm detonation nanodiamonds (DNDs), we prepared and employed hydrogenated 2 nm DNDs (zeta potential = +36 mV) to form extremely dense (∼1.3 × 1013 cm–2), thin (2 ± 1 nm), and smooth (RMS roughness < 0.8 nm) nucleation layers on an Si/SiOx substrate, which enabled the CVD growth of such ultrathin NCD films in two different and complementary microwave (MW) CVD systems: (i) focused MW plasma with an ellipsoidal cavity resonator and (ii) pulsed MW plasma with a linear antenna arrangement. Analytical ultracentrifuge, infrared and Raman spectroscopies, atomic force microscopy, and scanning electron microscopy are used for detailed characterization of the 2 nm H-DNDs and th...

Porous and self-standing structures are highly promising as membranes, electrodes, high sensitivity gas sensors, and supercapacitors due to their high surface area and tuneable surface properties. Composition of such materials with a polycrystalline diamond film may provide new functionalities for biological and electrochemical applications. However, the diamond growth on foreign substrates as a pinhole-free continuous thin film is still a not a trivial task. Here, we present a successful templated deposition process of polycrystalline diamond film on reticulated vitreous carbon foam (C-foam). Samples of polyvinyl alcohol (PVA) polymer-nanodiamond (ND) mixtures with various ND concentrations were prepared and characterized by means of optical spectroscopy, Raman spectroscopy, dynamic light scattering, zeta potential and pH measurements. The ND/PVA mixtures are employed for the preparation of diamond film by microwave plasma enhanced chemical vapour deposition process, and the effect of their composition (NDs/PVA ratio) on the nucleation (seed density, clustering) and diamond growth (substrate etching, polymer transformation) is analysed. The nucleation, early-stage of diamond growth and the resulting diamond-coated C-foams are characterized by scanning electron microscopy, atomic force microscopy and Raman spectroscopy. The obtained results underline the importance to tailor the NDs/PVA ratio for a well-defined three-dimensional C-foam coverage with the continuous diamond film.

Composite nanoparticles of detonation nanodiamond (DND) and polypyrrole (PPy) were produced in colloidal solution and on surfaces by wet chemical process. Changes of vibrational bands (in particular > CO and CH) in Fourier-transform infrared spectroscopy revealed the DND/PPy composite formation and tight interaction of PPy with hydrogenated DND (H-DND) and oxidized DND (O-DND). Atomic force microscopy showed uniform PPy coating but different PPy thickness on H-DND (7.0 nm) and O-DND (3.5 nm). These results suggest different bonding nature and arrangement of PPy on H-DND and O-DND surfaces.

Water interaction with surface modified nanodiamonds (NDs) is critical for many possible applications of NDs e.g. in biomedicine. Here we report on investigation of water interaction with hydrogenated and oxidized detonation nanodiamonds (H-DNDs, O-DNDs) by means of Fourier transform infrared spectroscopy (FTIR), thermal analysis, and Kelvin probe force microscopy (KPFM). Higher water content (4.4%) as well as weaker interaction of water with H-DNDs are identified by thermal analysis. It is explained by hydrophobicity of the H-DND surface, as revealed by the analysis of bending and stretching vibrations of surface water in FTIR spectra. On the other hand, hydrophilic nature of O-DNDs leads to lower water content (3.1%) but stronger interaction with the O-DND surface. This is evidenced by as high as 300 °C desorption temperature of the surface water from O-DNDs. KPFM analysis shows that the surface-bound water can have significant screening effect on contact potential difference (CPD) of nanodiamonds (up to 510 mV) as well as on the CPD difference between H-DNDs and O-DNDs (from 50 mV to 210 mV). Nevertheless, H-DNDs exhibit always lower work function.

Nanodiamonds (NDs) represent a novel nanomaterial applicable from biomedicine to spintronics. Here we study ability of air annealing to further decrease the typical 5 nm NDs produced by detonation synthesis. We use atomic force microscopy (AFM) with sub-nm resolution to directly measure individual detonation nanodiamonds (DNDs) on a flat Si substrate. By means of particle analysis we obtain their accurate and statistically relevant size distributions. Using this approach, we characterize evolution of the size distribution as a function of time and annealing temperature: i) at constant time (25 min) with changing temperature (480, 490, 500°C) and ii) at constant temperature (490°C) with changing time (10, 25, 50 min). We show that the mean size of DNDs can be controllably reduced from 4.5 nm to 1.8 nm without noticeable particle loss and down to 1.3 nm with 36% yield. By air annealing the size distribution changes from Gaussian to lognormal with a steep edge around 1 nm, indicating instability of DNDs below 1 nm.

Color centers in diamond have shown excellent potential for applications in quantum information processing, photonics, and biology. Here we report the optoelectronic investigation of shallow silicon vacancy (SiV) color centers in ultra-thin (7&ndash, 40 nm) nanocrystalline diamond (NCD) films with variable surface chemistry. We show that hydrogenated ultra-thin NCD films exhibit no or lowered SiV photoluminescence (PL) and relatively high negative surface photovoltage (SPV) which is ascribed to non-radiative electron transitions from SiV to surface-related traps. Higher SiV PL and low positive SPV of oxidized ultra-thin NCD films indicate an efficient excitation&mdash, emission PL process without significant electron escape, yet with some hole trapping in diamond surface states. Decreasing SPV magnitude and increasing SiV PL intensity with thickness, in both cases, is attributed to resonant energy transfer between shallow and bulk SiV. We also demonstrate that thermal treatments (annealing in air or in hydrogen gas), commonly applied to modify the surface chemistry of nanodiamonds, are also applicable to ultra-thin NCD films in terms of tuning their SiV PL and surface chemistry.

This chapter introduces complex opto-electronic behavior of nanodiamonds when they are in contact with surrounding materials. Kelvin probe force microscopy (KPFM) is used to show that surface potential of nanodiamonds is not uniform but depends on many factors such as substrate and probe material, nanodiamond surface termination, charge trapping, illumination, and adsorbed water. Special attention is devoted to practical aspects and methodology of the KPFM measurements of nanodiamonds and other nanoscale objects, in general. KPFM serves here also as a nanoscale tool for investigation of local charge exchange between the nanodiamonds and surroundings, which is shown to influence also their other physical properties such as photoluminescence, secondary electron emission, and photovoltage.

Evaluation of diamond nanoparticles (DNPs) electrical potential under ambient environment is important for their application in electronics as well as sensors and biology. Here we use a novel methodology for characterization of nanoparticles based on recording of their electrical potential as a function of their size by two-pass Kelvin force microscopy (KFM). We study thermally oxidized detonation DNPs of 5 nm nominal size. The nanoparticles were deposited from diluted water solutions on a Si substrate half coated with Au. The KFM using conductive Si tip resolved characteristic negative potential differences of 10–60 mV on nanoparticles versus the substrate. When negative bias voltage to the KFM tip (−4 V) is applied during the topography acquisition (the first pass), subsequent potential measurement (the second pass) shows inversion of nanoparticles potential contrast. The same effects were observed also in the case of 20 nm colloidal Au nanoparticles. This effect is reversible and it is attributed to a charge retention in (or on) the nanoparticles.

Detonation nanodiamonds (DNDs) with a typical size of 5 nm have attracted broad interest in science and technology. Further size reduction of DNDs would bring these nanoparticles to the molecular-size level and open new prospects for research and applications in various fields, ranging from quantum physics to biomedicine. Here we show a controllable size reduction of the DND mean size down to 1.4 nm without significant particle loss and with additional disintegration of DND core agglutinates by air annealing, leading to a significantly narrowed size distribution (±0.7 nm). This process is scalable to large quantities. Such molecular-sized DNDs keep their diamond structure and characteristic DND features as shown by Raman spectroscopy, infrared spectroscopy, STEM and EELS. The size of 1 nm is identified as a limit, below which the DNDs become amorphous.

Proceedings of the 9th International Conference on New Diamond and Nano Carbons (NDNC), 5-28 May 2015, Shizuoka, Japan. Editors Shinichi Shikata, Atsushi Hirata, Fumio Kokai, Junichi H. Kaneko, Kenji Watanabe, Mutsuko Hatano, Takako Nakamura.; International audience; Photoluminescence of 5 nm detonation nanodiamonds (DNDs) is studied as a function of their surface treatment (hydrogenation/oxidation) and underlying substrate materials (silicon, gold, platinum, and nickel). The substrates affect DND photoluminescence emission spectrum and lifetime in the spectral range of 600-800 nm. The dependence is different for hydrogenated and oxidized DNDs. We attribute these effects to different electrostatic charging of DNDs on the substrates with different work functions (4.4 to 5.5 eV). We discuss the data based on naturally present NV centers, their phonon sideband, and surface-related non-radiative transitions.

International audience; Macroscopic and microscopic photovoltage characteristics of detonation nanodiamonds (DNDs) with distinct surface terminations are presented. Organic photodiodes are fabricated based on P3HT+DNDs mixture (50 wt%). We compare effect of hydrogen and oxygen termination of DNDs. Compared to photodiodes without DNDs the current-voltage characteristics of photodiodes with O-DNDs in dark and under AM 1.5 illumination show reduced dark current, and higher photocurrent and open circuit voltage. H-DNDs shunt the photodiodes, which is attributed to their surface conductivity. Kelvin probe force microscopy detects a reproducible photovoltage of around 5 mV generated by a green laser (532 nm) on both types of pristine DNDs. Thus although conductivity of H-DNDs may represent a problem for photodiodes, both types of DNDs alone can function as miniature energy conversion devices.

Sensitivity of an intrinsic nanocrystalline diamond (NCD) layer to naphthalene Tröger's base derivative decorated with pyrrole groups (TBPyr) was characterized by impedance spectroscopy. The transducer was made of Au interdigitated electrodes (IDE) with 50 μm spacing on alumina substrate which were capped with the NCD layer. The NCD-capped transducer with H-termination was able to electrically distinguish TBPyr molecules (the change of surface resistance within 30-60 kΩ) adsorbed from methanol in concentrations of 0.04 mg/mL to 40 mg/mL. An exponential decay of the surface resistance with time was observed and attributed to the readsorption of air moisture after methanol evaporation. After surface oxidation the NCD cap layer did not show any leakage due to NCD grain boundaries. We analyzed electronic transport in the transducer and propose a model for the sensing mechanism based on surface ion replacement.

We report on visualization of a phase separation in Agx(As0.33S0.67)100−x and Agx(As0.33S0.335Se0.335)100−x chalcogenide glasses by means of atomic force microscopy (AFM). Sufficient topographical contrast (~20 nm) was achieved by selective polishing of a phase-separated sample (Ag-poor, Ag-rich regions) and phase separation occurred within 0.5–20 at.% Ag and 2–18 at.% Ag in Agx(As0.33S0.67)100−x and Agx(As0.33S0.335Se0.335)100−x systems, respectively. Homogenous regions were observed below and above the phase separation lower and upper limits. Direct comparison of scanning electron microscopy and atomic force microscopy sensitivity of phase separation detection is shown. In addition, concentration of silver in particular phases of AgAsS system was evaluated by NanoSIMS (secondary ion mass spectroscopy) and very similar concentration of silver was detected in the phases at boundaries of immiscibility region.

The electric properties of LiI containing chalcohalide glasses in the system Ga2S3–GeS2 were studied by means of impedance spectroscopy and potentiostatic chronoamperometry. Two sets of the samples were prepared by direct synthesis from elements and compounds in evacuated quartz ampoules. The prepared glasses were as follows: xLiI–xGa2S3–(100−2x)GeS2, x = 15, 20, 25 and 20LiI–xGa2S3–(80−x)GeS2, x = 0, 5, 10, 15 and 20. In the first set the concentration of LiI increased and the second set was prepared to study the influence of Ga2S3 on the properties of the glasses. Additional aim of this work was to compare the electric properties of LiI containing Ga2S3–GeS2 glasses with analogous AgI containing Ga2S3–GeS2 glasses recently studied by us. The conductivity of the LiI containing glasses in the Ga2S3–GeS2 system was higher and the activation energy was lower than in the analogous AgI containing system. The residual electronic (hole) conductivity remained similar in both systems being almost negligibly low. Raman spectroscopy proved the influence of LiI as well as Ga2S3 on glass structure, however interpretation of Raman spectra of these glasses is complicated due to small mass difference between gallium and germanium.

We report on electric properties of Ag x (As 0.33 Ch 0.67 ) 100 − x (Ch═S, Se, Te) glass systems in relation to their microstructure and changing constituting chalcogenide atoms. We observed decreasing contribution of the ionic conductivity when sulphur was replaced by selenium and tellurium. We also found a strong correlation between the conductivity and the phase separation into a silver-rich and a silver-poor phase which appears to be responsible for the semiconductor — ionic conductor transition in the sulphur and selenium based systems.

This article describes the preparation of multi-walled carbon nanotube—chalcogenide glass composite by direct synthesis and the melt-quenching method. The carbon nanotubes—chalcogenide glass composite was characterized by high-resolution transmission electron microscopy (HRTEM), TEM/energy-dispersive X-ray spectroscopy, low energy electron excited X-ray spectroscopy, Raman spectroscopy, spectroscopic ellipsometry, microhardness, and impedance spectroscopy. CNTs–AgAsS 2 glass composite possess highly increased ionic conductivity, from σ 25 °C =4.38±0.0438×10 −6 to σ 25 °C =6.57±0.0657×10 −6 S cm −1 and decreased refractive index from n =2.652 to 2.631 at the wavelength λ =1.55 μm.

Glasses with general formula Ag x (As 0.33 Se 0.67 ) 100− x were studied by means of modulated differential scanning calorimetry (MDSC), conductivity and permittivity measurements and atomic force acoustic microscopy (AFAM). In the whole range of doping ( x = 2–12 at.% Ag) a phase separation was supposed. The proportional amount of the ion-conductive Ag rich phase increased with the Ag content. A rapid increase (almost four orders of magnitude) in the conductivity was observed in the Ag concentration range 4–8 at.%, which could be associated with the interconnection of this ion-conductive phase. The transition from a hole conductivity (at low Ag concentration) to a mixed ionic-hole conductivity at higher Ag concentration was studied by permittivity measurements.

Electrical properties of (100 −2x)GeS2–xGa2S3–xAgI (x=15, 20, 25, 30 at.%), 60GeS2–20Ga2S3–20AgX (X = Cl, Br and I) and (60GeS2– 20Ga2S3–20AgI)100 −x–Agx (x=1 and 5 at.%) chalcohalide glasses are described in terms of conductivity and permittivity. The impedance spectroscopy method was used in the frequency range of 0.1 to 10 6 Hz and in the temperature range of 258 to 393 K for our conductivity and permittivity studies. We observed an Arrhenius behavior for all samples in the case of the temperature dependence of conductivity and a large dispersion of the real part of permittivity with decreasing frequency was identified. We also found a power-law dependence of the conductivity on the silver iodide content and an unusual almost linear dependence of the exponent α on the temperature. In addition, we determined frequencies ftp which were found to be threshold frequencies between the polarization due to the space charge accumulation and a rapid polarization process occurring in glassy ionic conductors. © 2008 Elsevier B.V. All rights reserved.

In this paper, results of investigation of the bulk glasses with composition of Ag x (As 0.33 S 0.335 Se 0.335 ) 100− x ( x =0–28 at%) are revealed. The amorphous structure of samples was confirmed by the X-ray diffraction analysis. The structure was deduced from the Raman spectra measured for all silver contents in As–S–Se matrix. From the point of their electrical properties, all glasses behave as ionic conductors. Their ac conductivity increases with increasing content of silver. As determined from the comparison of ac and dc conductivities, the contribution of electronic conductivity to the overall conductivity is very low and decreases from about 3% for the glass with 12 at% of Ag to about 1% for the glass with 22 at% of Ag.

High-pressure high-temperature (HPHT) nanodiamonds originate from grinding of diamond microcrystals obtained by HPHT synthesis. Here we report on a simple two-step approach to obtain as small as 1.1 nm HPHT nanodiamonds of excellent purity and crystallinity, which are among the smallest artificially prepared nanodiamonds ever shown and characterized. Moreover we provide experimental evidence of diamond stability down to 1 nm. Controlled annealing at 450 degrees C in air leads to efficient purification from the nondiamond carbon (shells and dots), as evidenced by X-ray photoelectron spectroscopy, Raman spectroscopy, photoluminescence spectroscopy, and scanning transmission electron microscopy. Annealing at 500 degrees C promotes, besides of purification, also size reduction of nanodiamonds down to 1 nm. Comparably short (1 h) centrifugation of the nanodiamonds aqueous colloidal solution ensures separation of the sub-10 nm fraction. Calculations show that an asymmetry of Raman diamond peak of sub-10 nm HPHT nanodiamonds can be well explained by modified phonon confinement model when the actual particle size distribution is taken into account. In contrast, larger Raman peak asymmetry commonly observed in Raman spectra of detonation nanodiamonds is mainly attributed to defects rather than to the phonon confinement. Thus, the obtained characteristics reflect high material quality including nanoscale effects in sub-10 nm HPHT nanodiamonds prepared by the presented method.

International audience; Properties of nanoparticles in contact with other surfaces are crucial for various applications. Here, we show that electrical potential of individual nanoparticles or their aggregates (sizes 5–50 nm) can be locally switched between negative and positive via work functions of surrounding materials (Si, Au, and Pt). We employed novel methodology of Kelvin probe force microscopy (KPFM) to characterize surface potentials of hydrogenated, thermally oxidized, and partially graphitized detonation diamond nanoparticles (5 nm), as well as gold nanoparticles (20 nm) deposited on the substrates (Si, Au) from colloidal dispersions in water or methanol. We present a comprehensive model of the observed effect based on work functions of the involved materials and charge trapping in or on the nanoparticles. The model is further confirmed by modification of nanoparticle charges after intentional application of up to ±4 V through the KPFM tip. The observed effects may impact other physical properties such as electron emission and photoluminescence of the nanoparticles.

International audience; Electrical potential of nanoparticles under relevant environment is substantial for their applications in electronics as well as sensors and biology. Here, we use Kelvin force microscopy to characterize electrical properties of semiconducting diamond nanoparticles (DNPs) of 5-10 nm nominal size and metallic gold nanoparticles (20 and 40 nm) on Si and Au substrates under ambient conditions. The DNPs are deposited on Si and Au substrates from dispersions with well-defined zeta-potential. We show that the nanoparticle potential depends on its size and that the only reliable potential characteristic is a linear fit of this dependence within a 5-50 nm range. Systematically different potentials of hydrogenated, oxidized, and graphitized DNPs are resolved using this methodology. The differences are within 50 mV, that is much lower than on monocrystalline diamond. Furthermore, all of the nanoparticles assume their potential within -60 mV according to the Au and Si substrate, thus gaining up to 0.4 V difference. This effect is attributed to DNP charging by charge transfer and/or polarization. This is confirmed by secondary electron emission. Such effects are general with broad implications for nanoparticles applications.

We show that a random walk model of diffused ions interprets well the experimentally deduced Nyquist plots in ionic chalcogenide glasses. Fitting of the model to the experimental data in the Nyquist plots of Ag–As–S(Se) glasses taken as case examples yields important physical parameters such as number of mobile Ag+ ions, hopping relaxation time and diffusion coefficient. It was found that the number of freely moving Ag+ ions is almost independent of Ag content in Ag x (As0.33S(Se)0.67)100−x glasses, while the maximum hopping relaxation time is highly dependent on Ag concentration.

(As(0.4)S(0.6))(100-x)Ag(x) glasses (x = 0, 4, 8, 12 at.%) have been studied with high-energy x-ray diffraction, neutron diffraction and extended x-ray absorption spectroscopy at As and Ag K-edges. The experimental data were modelled simultaneously with the reverse Monte Carlo simulation method. Analysis of the partial pair correlation functions and coordination numbers extracted from the model atomic configurations revealed that silver preferentially bonds to sulfur in the As(2)S(3)-Ag ternary glasses, which results in the formation of homoatomic As-As bonds. Upon the addition of Ag, a small proportion of Ag-As bonds (N(AgAs)≈0.3) are formed in all three ternary compositions, while the direct Ag-Ag bonds (N(AgAg)≈ 0.4) appear only in the glass with the highest Ag content (12 at.%). Similar to the g- As(2)S(3) binary, the mean coordination number of arsenic is close to three, and that of sulfur is close to two, in the As(2)S(3)-Ag ternary glasses. The first sharp diffraction peak on the total structure factors of As(2)S(3) binary and (As(0.4)S(0.6))(100-x)Ag(x) ternary glasses is related to the As-As and As-S correlations.