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PubMed2004

Electrochemical performance of diamond thin-film electrodes from different commercial sources.

The electrochemical properties of two commercial (Condias, Sumitomo) boron-doped diamond thin-film electrodes were compared with those of two types of boron-doped diamond thin film deposited in our laboratory (microcrystalline, nanocrystalline). Scanning electron microscopy and Raman spectroscopy were used to characterize the electrode morphology and microstructure, respectively. Cyclic voltammetry was used to study the electrochemical response, with five different redox systems serving as probes (Fe(CN)(6)(3)(-)(/4)(-), Ru(NH(3))(6)(3+/)(2+), IrCl(6)(2)(-)(/3)(-), 4-methylcatechol, Fe(3+/2+)). The response for the different systems was quite reproducibile from electrode type to type and from film to film for electrodes of the same type. For all five redox systems, the forward reaction peak current varied linearly with the scan rate(1/2) (nu), indicative of electrode reaction kinetics controlled by mass transport (semi-infinite linear diffusion) of the reactant. Apparent heterogeneous electron-transfer rate constants, k degrees (app), for all five redox systems were determined from deltaE(p)-nu experimental data, according to the method described by Nicholson (Nicholson, R. S. Anal. Chem. 1965, 37, 1351.). The rate constants were also verified through digital simulation (DigiSim 3.03) of the voltammetric i-E curves at different scan rates. Good fits between the experimental and simulated voltammograms were found for scan rates up to 50 V/s. k degrees (app) values of 0.05-0.5 cm/s were observed for Fe(CN)(6)(3)(-)(/4)(-), Ru(NH(3))(6)(3+/2+), and IrCl(6)(2)(-)(/3)(-) without any extensive electrode pretreatment (e.g., polishing). Lower k degrees (app) values of 10(-)(4)-10(-)(6) cm/s were found for 4-methylcatechol and Fe(3+/2+). The voltammetric responses for Fe(CN)(6)(3)(-)(/4)(-) and Ru(NH(3))(6)(3+/2+) were also examined at all four electrode types at two different solution pH (1.90, 7.35). Since the hydrogen-terminated diamond surfaces contain few, if any, ionizable carbon-oxygen functionalities (e.g., carboxylic acid, pK(a) approximately 4.5), the deltaE(p), i(p)(ox), and i(p)(red) values for the two systems were, for the most part, unaffected by the solution pH. This is in contrast to the typical behavior of oxygenated, sp(2) carbon electrodes, such as glassy carbon.

Boron↗
PubMed2005

High-affinity capture of proteins by diamond nanoparticles for mass spectrometric analysis.

Carboxylated/oxidized diamond nanoparticles (nominal size 100 nm) exhibit exceptionally high affinity for proteins through both hydrophilic and hydrophobic forces. The affinity is so high that proteins in dilute solution can be easily captured by diamonds, simply separated by centrifugation, and directly analyzed by matrix-assisted laser desorption/ionization (MALDI) time-of-flight (TOF) mass spectrometry (MS). No preseparation of the adsorbed molecules from diamonds is required for the mass spectrometric analysis. Compared to conventional MALDI-TOF-MS, an enhancement in detection sensitivity by more than 2 orders of magnitude is achieved for dilute solution containing cytochrome c, myoglobin, and albumin because of preconcentration of the probed molecules. The lowest concentration detectable is 100 pM for a 1-mL solution. Aside from the enhanced sensitivity, the overall performance of this technique does not show any sign of deterioration for highly contaminated protein solutions, and furthermore, no significant peak broadening and band shift were observed in the mass spectra. The promise of this new method for clinical proteomics research is demonstrated with an application to human blood serum.

Adsorption↗
PubMed2006

Electrochemical detection of arsenic(III) using iridium-implanted boron-doped diamond electrodes.

Iridium-modified, boron-doped diamond electrodes fabricated by an ion implantation method have been developed for electrochemical detection of arsenite (As(III)). Ir+ ions were implanted with an energy of 800 keV and a dose of 10(15) ion cm(-2). An annealing treatment at 850 degrees C for 45 min in H2 plasma (80 Torr) was required to rearrange metastable diamond produced by an implantation process. Characterization was investigated by SEM, AFM, Raman, and X-ray photoelectron spectroscopy. Cyclic voltammetry and flow injection analysis with amperometric detection were used to study the electrochemical reaction. The electrodes exhibited high catalytic activity toward As(III) oxidation with the detection limit (S/N = 3), sensitivity, and linearity of 20 nM (1.5 ppb), 93 nA microM(-1) cm(-2), and 0.999, respectively. The precision for 10 replicate determinations of 50 microM As(III) was 4.56% relative standard deviation. The advantageous properties of the electrodes were its inherent stability with a very low background current. The electrode was applicable for analysis of spiked arsenic in tap water containing a significant amount of various ion elements. The results indicate that the metal-implanted method could be promising for controlling the electrochemical properties of diamond electrodes.

Arsenites↗
PubMed2006

Geometric properties of covalently bonded DNA on single-crystalline diamond.

Diamond is a promising candidate for bioapplications. Properties of hybridized DNA arrays on single-crystalline diamond are studied on a microscopic level by atomic force microscopy (AFM) in buffer solutions. Compact DNA layers in a thickness of 76 A are resolved by optimizing phase and height contrast in AFM. The height shows some long-range (30 nm) undulations of +/-5 A due to tip and DNA interactions. The axis of double helix DNA is oriented at about 36 degrees with respect to the diamond surface. DNA molecules can be removed by contact-mode AFM with forces >45 nN, indicating stronger DNA bonding than on gold substrates.

DNA↗
PubMed2006

The cycloadditions of various substituted carbenes, silylenes, and germylenes onto the diamond (100) surface: a theoretical exploration.

The cycloadditions of 21 singlet substituted carbenes, silylenes, and germylenes onto the diamond (100) surface have been theoretically studied by means of density functional theory coupled with effective cluster models. The calculated reaction energies and reaction pathways have disclosed that the substituents play an important effect on the reaction profiles for the additions of carbenes, silylenes, and germylenes onto the diamond (100) surface. Our theoretical investigations illustrate that, irrespective of carbenes, silylenes, and germylenes, the cycloadditions of those with electropositive substituents (such as H and CH(3)) onto diamond (100) are much more favorable than those with electronegative and pi-donating substituents (such as F and NH(2)) both thermodynamically and kinetically. In broad perspective, we believe that a similar reactivity trend can also be extended to that of Si (100), Ge (100), fullerene, single-walled carbon nanotube, disilenes, digermenes, silenes, and germenes because all of these materials feature an analogous bonding motif.

Cyclization↗
PubMed2006

Characterization of DNA hybridization on partially aminated diamond by aromatic compounds.

Here, we report a novel method of micropatterning oligonucleotides via aromatic groups as linkers on partially amino-terminated diamond and the inherence on subsequent hybridization. The covalent immobilization of probe oligonucleotides and characterization of immobilized probe oligonucleotides with carboxylic compounds were investigated by X-ray photoelectron spectroscopy (XPS). To confirm the effects of linker flexibility in a low amino group on diamond for probe oligonucleotides, three kinds of dicarboxylic compound--adipic acid, terephthalic acid, and trimesic acid--were used for immobilization of probe oligonucleotides, like linkers; and these oligonucleotides were hybridized with target oligonucleotides labeled with Cy 5 on the micropatterned diamond surface. The hybridization intensities determined by epifluorescence microscopy were compared and analyzed.

Carbocyanines↗
PubMed2006

Giant enhancement of the carrier mobility in silicon nanowires with diamond coating.

We show theoretically that the low-field carrier mobility in silicon nanowires can be greatly enhanced by embedding the nanowires within a hard material such as diamond. The electron mobility in the cylindrical silicon nanowires with 4-nm diameter, which are coated with diamond, is 2 orders of magnitude higher at 10 K and a factor of 2 higher at room temperature than the mobility in a free-standing silicon nanowire. The importance of this result for the downscaled architectures and possible silicon-carbon nanoelectronic devices is augmented by an extra benefit of diamond, a superior heat conductor, for thermal management.

Diamond↗
PubMed1999

Root debridement of single-rooted teeth with a diamond-coated sonic scaler insert during flap surgery. A pilot study.

In our laboratory, we modified inserts of a sonic scaler to increase effectivity of root surface instrumentation during flap surgery. The present clinical study investigates whether use of this diamond-coated, thickened insert facilitates more rapid root debridement compared to hand instruments and whether clinical wound healing is influenced by the type of instrument used. In 13 patients with moderate to advanced periodontal destructions, flap surgery was carried out on single rooted teeth with probing depth of > or =6 mm. The mean amount of time saved by root debridement with the diamond-coated insert was 60% over curets. Regardless of the used instrumentation method probing depths and attachment level changes were altered and remained unchanged for 2 years after surgery. In conclusion the newly-developed, diamond-coated sonic scaler insert facilitates more rapid root debridement during flap surgery than hand instruments without disadvantageously affecting clinical healing.

Adult↗
PubMed1999

Root debridement of molars with furcation involvement using diamond-coated sonic scaler inserts during flap surgery -- a pilot study.

In our laboratory, we modified sonic scaler inserts to increase effectivity of root surface instrumentation of molars with furcation involvement during flap surgery. The working end of conventional sonic scaler inserts was thickened ellipsoidally and diamond coated. Inserts with variously angled shafts were designed in order to facilitate insertion into the furcation. A clinical, split-mouth study examined the debridement of molars with furcation involvement during flap surgery using either hand instruments or diamond-coated sonic scaler inserts with 15 patients. Average treatment time was cut by ca. 50%, using diamond-coated inserts as compared to hand instruments for root surface debridement during surgery. 2 years after surgery, the clinical parameters had not been influenced by type of instrument used.

Adult↗
PubMed2004

Diamond-structured photonic crystals.

Certain periodic dielectric structures can prohibit the propagation of light for all directions within a frequency range. These 'photonic crystals' allow researchers to modify the interaction between electromagnetic fields and dielectric media from radio to optical wavelengths. Their technological potential, such as the inhibition of spontaneous emission, enhancement of semiconductor lasers, and integration and miniaturization of optical components, makes the search for an easy-to-craft photonic crystal with a large bandgap a major field of study. This progress article surveys a collection of robust complete three-dimensional dielectric photonic-bandgap structures for the visible and near-infrared regimes based on the diamond morphology together with their specific fabrication techniques. The basic origin of the complete photonic bandgap for the 'champion' diamond morphology is described in terms of dielectric modulations along principal directions. Progress in three-dimensional interference lithography for fabrication of near-champion diamond-based structures is also discussed.

Crystallization↗
PubMed2003

Characterization of the cutting edge of glass and diamond knives for ultramicrotomy by scanning force microscopy using cantilevers with a defined tip geometry. Part II.

The cutting edge of glass as well as diamond knives was studied at high resolution using a scanning force microscope (SFM). The local shape of the cutting edge was estimated from single line profiles of the SFM topographs taking into account the exact shape of the probing tip estimated by a high-resolution field emission scanning electron microscope (FESEM). The glass knives were prepared by 'balanced breaking'. The radius of the investigated cutting edges was found to be 3.2-4.4 nm and 4.3-6.0 nm for the 35 degrees and 45 degrees diamond knife, respectively, and 3.4-4.3 nm for the glass knives. Besides the opening angle and the cutting edge radius, the friction of a knife during sectioning represents a significant factor influencing the quality of sections. Thus, the roughness of both the diamond clearance angle side and the back side was characterized as well. Corresponding RMS values of the roughness were found to be smaller on the back side (approximately 0.14 nm) than on the clearance angle side (approximately 0.26 nm).

Diamond↗
PubMed2005

Specific Role for Yeast Homologs of the Diamond Blackfan Anemia-associated Rps19 Protein in Ribosome Synthesis.

Approximately 25% of cases of Diamond Blackfan anemia, a severe hypoplastic anemia, are linked to heterozygous mutations in the gene encoding ribosomal protein S19 that result in haploinsufficiency for this protein. Here we show that deletion of either of the two genes encoding Rps19 in yeast severely affects the production of 40 S ribosomal subunits. Rps19 is an essential protein that is strictly required for maturation of the 3'-end of 18 S rRNA. Depletion of Rps19 results in the accumulation of aberrant pre-40 S particles retained in the nucleus that fail to associate with pre-ribosomal factors involved in late maturation steps, including Enp1, Tsr1, and Rio2. When introduced in yeast Rps19, amino acid substitutions found in Diamond Blackfan anemia patients induce defects in the processing of the pre-rRNA similar to those observed in cells under-expressing Rps19. These results uncover a pivotal role of Rps19 in the assembly and maturation of the pre-40 S particles and demonstrate for the first time the effect of Diamond Blackfan anemia-associated mutations on the function of Rps19, strongly connecting the pathology to ribosome biogenesis.

Alleles↗
PubMed1997

A Monte Carlo study of the quality dependence of diamond thermoluminescent dosimeters in radiotherapy beams.

Monte Carlo simulations with the EGS4 code system have been performed to determine the quality dependence of diamond TLDs in photon beams ranging from 25 kV to 25 MV x-rays and also in megavoltage electron beams. It has been shown that diamond TLDs in the form of discs of thickness 0.3 mm and diameter 5.64 mm show no significant dependence on the incident energy in clinical electron beams when irradiated close to dmax, but require an energy correction factor of 1.050 +/- 0.008 compared with diamond TLDs irradiated in 60Co gamma-rays. The correction factor increases with depth of irradiation and this effect is greater for thicker detectors. The Monte Carlo predicted sensitivity in x-ray beams is constant within 2.5% over the energy range 250 kV to 25 MV. However the sensitivity decreases by about 60% for 25 kV x-rays compared with 60Co gamma-rays.

Cobalt Radioisotopes↗
PubMed1998

Application of a diamond detector to brachytherapy dosimetry.

The feasibility of using a diamond detector for the dosimetry of brachytherapy sources has been investigated. A high-activity 192Ir source was selected for this purpose. The dosimetric characteristics measured included the photon fluence anisotropy in air, transverse dose profiles in planes parallel to the plane containing the HDR source and isodose distributions. The 'in-air' anisotropy of the photon fluence relative to seed orientation was measured at 5 and 10 cm from the source centre and compared with TLD measurements. Transverse dose distributions in planes parallel to the plane containing the source long axis were measured in a water phantom and compared with calculations performed with a treatment planning system. Isodose distributions were also measured in several planes around the 192Ir source. Measurements on two sources indicate that the 'in-air' photon fluence anisotropy measured by the diamond detector and the TLDs is very similar. Dose profiles measured at several distances from the source are also found to be in good agreement with the calculated dose profiles and isodose distributions. Results of this feasibility study indicate that the diamond detector, with its excellent spatial resolution and nearly tissue equivalent and isotropic radiation response, is an appropriate detector for dose measurements around brachytherapy sources.

Anisotropy↗
PubMed2002

Thermoluminescence in CVD diamond films: application to actinometric dosimetry.

Diamond is considered a tissue-equivalent material since its atomic number (Z =6) is close to the effective atomic number of biological tissue (Z =7.42). Such a situation makes it suitable for radiation detection purposes in medical applications. In the present work the analysis is reported of the thermoluminescence (TL) and dosimetric features of chemically vapour deposited (CVD) diamond film samples subjected to ultraviolet (UV) irradiation in the actinometric region. The TL glow curve shows peaks at 120, 220), 320 and 370 degrees C. The 120 and 370 degrees C peaks are too weak and the first one fades away in a few seconds after exposure. The overall room temperature fading shows a 50% TL decay 30 min after exposure. The 320 degrees C glow peak is considered to be the most adequate for dosimetric applications due to its low fading and linear TL behaviour as a function of UV dose in the 180-260 nm range. The TL excitation spectrum presents a broad band with at least two overlapped components around 205 and 220 nm. The results indicate that the TL behaviour of CVD diamond film can be a good alternative to the currently available dosemeter and detector in the actinometric region as well as in clinical and medical applications.

Diamond↗
PubMed2006

On the dose response of some CVD diamond thermoluminescent detectors.

The linearity of dose response of chemical vapour deposition (CVD) diamonds grown at the Institute for Materials Research at Limburg University, Belgium, was investigated over a dose range relevant for radiotherapy. The following CVD diamonds were investigated: (1) a batch of square 3 x 3 mm2 detectors cut from a CVD wafer and (2) an as-grown CVD wafer of 6 cm diameter. A total of 20 CVD square detectors were irradiated with 137Cs gamma rays over the dose range from 200 mGy to 25 Gy. The CVD wafer, used as a large-area thermoluminescent (TL) detector, was exposed to a 226Ra needle. Very few square detectors showed linearity over a limited dose range, followed by saturation of the TL signal. The dose range of linearity was found to be strongly affected by the thermal annealing procedure of the detector. Owing to its high sensitivity and homogeneity of response, the large CVD diamond wafer was found to be very suitable as a large-area detector for 2-D dose mapping of the 226Ra brachytherapy source, possibly for Quality Assurance purposes.

Computer Simulation↗
PubMed2006

Label-free DNA sensors using ultrasensitive diamond field-effect transistors in solution.

Charge detection biosensors have recently become the focal point of biosensor research, especially field-effect-transistors (FETs) that combine compactness, low cost, high input, and low output impedances, to realize simple and stable in vivo diagnostic systems. However, critical evaluation of the possibility and limitations of charge detection of label-free DNA hybridization using silicon-based ion-sensitive FETs (ISFETs) has been introduced recently. The channel surface of these devices must be covered by relatively thick insulating layers ( SiO2, Si3N4, Al2O3, or Ta2O5) to protect against the invasion of ions from solution. These thick insulating layers are not suitable for charge detection of DNA and miniaturization, as the small capacitance of thick insulating layers restricts translation of the negative DNA charge from the electrolyte to the channel surface. To overcome these difficulties, thin-gate-insulator FET sensors should be developed. Here, we report diamond solution-gate FETs (SGFETs), where the DNA-immobilized channels are exposed directly to the electrolyte solution without gate insulator. These SGFETs operate stably within the large potential window of diamond (>3.0 V). Thus, the channel surface does not need to be covered by thick insulating layers, and DNA is immobilized directly through amine sites, which is a factor of 30 more sensitive than existing Si-ISFET DNA sensors. Diamond SGFETs can rapidly detect complementary, 3-mer mismatched (10 pM) and has a potential for the detection of single-base mismatched oligonucleotide DNA, without biological degradation by cyclically repeated hybridization and denature.

Biosensing Techniques↗
PubMed2004

Bond strength of simplified-step adhesives to enamel prepared with two different diamond burs.

BACKGROUND: Self-etching primers are reported to produce considerable etching on flat enamel surfaces. However, little is known about the influence of different enamel surface textures. In this study the influence of grinding enamel on bond strength of two all-in-one and one two-step adhesives was investigated. METHODS: Resin composite was bonded to the ground enamel of extracted human third molars that was reduced 0.5 mm from the buccal or lingual surfaces using either regular- or superfine-grit diamond burs with each of the three adhesives. After 24 hours in 37 degrees C water, the specimens were sectioned into slabs of 0.7 mm thickness, trimmed to an hourglass configuration, and subjected to microtensile bond strength (MTBS) testing. RESULTS: For all adhesive systems, MTBS to enamel ground with a regular-grit diamond bur was not significantly different from that with a superfine-grit diamond bur. The etching patterns of these adhesives were partly varied according to the aggressiveness of the adhesives. CONCLUSION: The use of two different burs does not affect the tensile bond strength of the adhesives to enamel.

Acid Etching, Dental↗