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Envenoming caused by snakebites is a very important neglected tropical disease worldwide. The myotoxic phospholipases present in the bothropic venom disrupt the sarcolemma and compromise the mechanisms of energy production, leading to myonecrosis. Photobiomodulation therapy (PBMT) has been used as an effective tool to treat diverse cases of injuries, such as snake venom-induced myonecrosis. Based on that, the aim of this study was to analyze the effects of PBMT through low-level laser irradiation (904 nm) on the muscle regeneration after the myonecrosis induced by Bothrops jararacussu snake venom (Bjssu) injection, focusing on myogenic regulatory factors expression, such as Pax7, MyoD, and Myogenin (MyoG). Male Swiss mice (Mus musculus), 6–8-week-old, weighing 22 ± 3 g were used. Single sub-lethal Bjssu dose or saline was injected into the right mice gastrocnemius muscle. At 3, 24, 48, and 72 h after injections, mice were submitted to PBMT treatment. When finished the periods of 48 and 72 h, mice were euthanized and the right gastrocnemius were collected for analyses. We observed extensive inflammatory infiltrate in all the groups submitted to Bjssu injections. PBMT was able to reduce the myonecrotic area at 48 and 72 h after envenomation. There was a significant increase of MyoG mRNA expression at 72 h after venom injection. The data suggest that beyond the protective effect promoted by PBMT against Bjssu-induced myonecrosis, the low-level laser irradiation was able to stimulate the satellite cells, thus enhancing the muscle repair by improving myogenic differentiation.

The notional area of field emission is an important parameter to correlate characteristic current density to the emission current, linking field emission theories to experimental observations. Recently, it has been reported that the notional area of emission contributes to the high brightness of large diameter emitters. Thus, it is necessary to understand how the notional area of emission depends on physical and geometrical parameters. In this work, we carried out numerical simulations to evaluate the notional area, A n, considering cold field electron emission from a hemisphere on a cylindrical post (HCP) emitter in an array. An HCP is suitable to model classically carbon nanotubes or carbon nanofibres-like emitters. We provide the dependence of A n on a wide range of physical and geometrical parameters, namely: the separation between the HCP emitters, the aspect ratio, radius, local work function and the macroscopic emission current. We explain the behavior of A n as a function of these parameters and show in which cases A n can be considered nearly constant. Our numerical results are within the framework of the standard Fowler-Nordheim (FN) theory and can simplify the modeling of the field emission phenomenon, because it directly relates simulation predictions to the currents observable experimentally. Also, this work provides information for experimentalists that can be useful to check the validity of the Schottky-Nordheim (SN) barrier upon the elementary FN theory.

Reduced graphene oxide-coated carbon nanotubes (RGO-CNT) electrodes have been prepared by hot filament chemical vapour deposition system in one-step growth process. We studied RGO-CNT electrodes behaviour as cold cathode in field emission test. Our results show that RGO-CNT retain the low threshold voltage typical of CNTs, but with greatly improved emission current stability. The field emission enhancement value is significantly higher than that expected being caused by geometric effect (height divided by the radius of nanotube). This suggested that the field emission of this hybrid structure is not only from a single tip, but eventually it is from several tips with contribution of graphene nanosheets at CNT's walls. This phenomenon explains why the graphenated carbon nanotubes do not burn out as quickly as CNT does until emission ceases completely. These preliminaries results make nanocarbon materials good candidates for applications as electron sources for several devices.

The pathogenesis of myonecrosis caused by myotoxins from bothropic venom is associated with local extracellular matrix (ECM) disintegration, hemorrhage, and inflammation. Search for alternative methods associated with serum therapy is mandatory to neutralize the fast development of local damage following snakebites. The experimental use of photobiomodulation therapy (PBMT) in murine models has shown promising results relative to structural and functional recovery from bothropic snakebite-induced myonecrosis. This study pioneered in using Raman and Fourier transform infrared (FTIR) spectroscopies to characterize biochemical alterations in the gastrocnemius that had been injected with Bothrops jararacussu venom and exposed to local PBMT. Results show that vibrational spectra from lyophilized and diluted venom (1307 cm −1) was also found in the envenomed gastrocnemius indicating venom presence in the unirradiated muscle 48 h post-injection; but any longer visible after PBMT at this time exposure or 72 h post-injection regardless irradiated or not. Raman and FTIR analyses indicated that the bands with higher area and intensity were 1657 and 1547 cm−1 and 1667 and 1452 cm−1, respectively; all are assignments for proteins, especially collagen, and are higher in the PBMT-exposed gastrocnemius. The infrared spectra suggest that laser treatment was able to change protein in tissue and that such change indicates collagen as the main target. We hypothesize that the findings reflect remodeling of ECM with key participation of collagen and faster tissue recovery for an anabolic condition.

In order to assess the safety of the carbon nanotubes to human health and the environment, we investigated the potential toxicity and ability of multi-walled carbon nanotubes (NT), to induce DNA damage by employing the Allium cepa genotoxicity/mutagenicity test and the Somatic Mutation and Recombination Test (SMART) in the fruitfly, Drosophila melanogaster. The results demonstrated that NT did not significantly induce genotoxic or mutagenic effects in the Allium cepa test. All concentrations evaluated in the SMART assay showed survival rates higher than 90 percent, indicating the absence of chronic toxicity for NT. Furthermore, the various treatments showed no significant increase in the NT mutation and recombination frequencies in mwh/flr3 genotype compared to respective negative controls, demonstrating the absence of DNA damage caused by NT.

Reduced graphene oxide (RGO) and vertically aligned carbon nanotubes (VACNT) superhydrophilic films were prepared by chemical vapor deposition techniques for electrical energy storage investigations. These electrodes were characterized in terms of their material and electrochemical properties by scanning electron microscopy (SEM), surface wettability, Fourier transform infrared spectroscopy (FTIR), energy dispersive and Raman spectroscopies, cyclic voltammetry (CV) and galvanostatic charge–discharge. We observed several physical structural and electrochemical similarities between these carbon-based materials with particular attention to very good specific capacitance, ultra-high energy storage and fast power delivery. Our results showed that the main difference between specific capacitance values is attributed to pseudocapacitive contribution and high density of multiwall nanotubes tips. In this work we have tested a supercapacitor device using the VACNT electrodes.

We report a technique of fabrication of Al nanoislands of dimensions as small as 3 nm. Thin Al foils were anodized from both the surfaces under conditions suitable for the growth of porous alumina. Unanodized Al nanoislands were thus formed at the interpore regions and characterized by transmission electron microscopy. The method allows control over the distribution and the size of the nanoscale islands through the parameters of the anodization process, and automatic passivation by surrounding alumina.

Microcrystalline (MCD) and nanocrystalline (NCD) magnetic diamond samples were produced by hot-filament chemical vapour deposition (HFCVD) on AISI 316 substrates. Energy Dispersive X-ray Spectroscopy (EDS) measurements indicated the presence of Fe, Cr and Ni in the MCD and NCD samples, and all samples showed similar magnetisation properties. Cell viability tests were realised using Vero cells, a type of fibroblastic cell line. Polystyrene was used as a negative control for toxicity (NCT). The cells were cultured under standard cell culture conditions. The proliferation indicated that these magnetic diamond samples were not cytotoxic.

Polyvinyl alcohol (PVA) hydrogels both pure and reinforced with two types of carbon nanoparticles (nanotubes and nanofibres) were studied as a candidate material for osteochondral defect repair. The carbon nanoparticles produced by chemical vapour deposition were characterised by Raman spectroscopy, field emission scanning electron microscopy and high-resolution transmission electron microscopy. The hydrogels were surgically implanted in osteochondral defects in the articular cartilage of rats and, after 3 and 12 weeks of follow-up, examined by scanning electron microscopy (SEM), optical microscopy (OM), creep indentation test (CIT) and X-ray fluorescence (XRF). No sign of tissue adhesion or abrasive wear could be seen by SEM. OM revealed dense connective tissue at the interface after 3 weeks and neoformed bone tissue without significant inflammatory process after 12 weeks. Dense connective tissue could be seen at the pure-PVA/tissue interface after 12 weeks, but not at the carbon reinforced-PVA/tissue interface after the same follow-up time. The hydrogel creep modulus increased with follow-up time. XRF revealed an increasing concentration of calcium and phosphorus in the implants over time, a phenomenon more pronounced for the hydrogels with carbon nanofibres. The results suggest that PVA hydrogel with carbon nanoparticles elicits a stronger biological response than pure hydrogel.

Polyvinyl alcohol (PVAl) hydrogel, alone and reinforced with two types of carbon nanoparticles, was studied in cultured cells to assess its potential use in treating osteochondral defects. The carbon nanoparticles were produced by hot-filament chemical vapour deposition. The carbon material was characterised with a Renishaw Invia Raman microscope system and the morphological particles were characterised with field emission scanning electron microscopy and high-resolution transmission electron microscopy. Cytotoxicity was evaluated by measuring the Vero fibroblast-type cells’ metabolic activity and studying their morphology. The osteogenic differentiation of mesenchymal stem cells obtained from rat bone marrow was evaluated by alkaline phosphatase (ALP) and alizarin red S (ARS) staining. Cell viability and morphology were assessed with thiazolyl blue tetrazolium bromide and scanning electron microscopy, respectively. The materials did not interfere with the viability, metabolic activity, morphology and spreading of either of the cell types analysed. Nodules of mineralised organic matrix were identified with ARS and ALP, confirming osteogenic differentiation. These results indicated higher concentration of ALP and mineralised matrix for PVAl with carbon nanoparticles. The results of this study indicate the potential use of carbon nanoparticles with PVAl hydrogels as orthopaedic biomaterials to treat osteochondral defects, but further in vivo investigations are still necessary.

Thedepositionofwell-adherentdiamondfilmsontotheoutersurfaceofcylindricalsubstrateswasperformed.Severaldiametersizesanddifferentsubstratesmaterialswerestudied.Diamondfilmsadherencewasimprovedbyincreasingthesubstratesurfaceroughnessandbypyrolisingcastoroilorpolyanilinepolymeronsubstratesurfacetoacceleratetheformationofdiamondinitialnuclei.Profilometryand scanning electron microscopy were used respectively to measure roughness of surface and to characterize the morphologies ofthe diamond films. The residual stress in the diamond films was characterized by Raman spectroscopy with depth series analysis.Voltammetric analysis using c-BDD electrodes were performed in acid media, revealing high quality diamond behavior.© 2012 The Electrochemical Society. [DOI: 10.1149/2.001205jss] All rights reserved.Manuscript submitted June 12, 2012; revised manuscript received July 25, 2012. Published August 29, 2012.

Magnetic semiconductors are promising materials for electronic applications, because it is possible to control the quantum state of the electron spin (up or down), providing almost total spin polarization. We present boron-doped nanocrystalline diamond samples with magnetic properties prepared by chemical vapor deposition process and characterized using X-ray photoelectron spectroscopy, energy dispersive X-ray spectroscopy, Raman spectroscopy, scanning electron microscopy and magnetization assays. We believe that ferromagnetic elements were incorporated into the diamond film by diffusion from stainless steel substrates, during film growth.

Chemical vapor deposited diamond is a new potential biomedical material which has the advantage of chemical inertness, extreme hardness and low coefficient of friction, among others. In orthopedics and maxillofacial surgery, these properties could improve implant performance, reducing metallic corrosion, particle wear, inflammatory reactions and bone loss. In the present study, two types of chemical vapor deposition (CVD) diamonds have been analyzed: microcrystalline diamonds (MD) and nanocrystalline diamonds (ND), both produced by hot-filament chemical vapor deposition. The diamond tubes were previously characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM) and Raman scattering spectroscopy (RSS). The aim of this study was to verify the interface between bone and MD and ND, surgically implanted in the femoral diaphysis of Wistar rats, after 4 and 8 weeks. The outcome was evaluated by scanning electron and optical microscopy using a semi quantitative method. The results suggest that nanocrystalline diamonds (ND) elicits a richer biological response than microcrystalline diamonds (MD) when in interaction with bone.

Sulfur doping of diamond samples produced by the hot-filament chemical vapor deposition (CVD) process using carbon disulfide highly diluted in ethanol and hydrogen has been investigated. The polycrystalline morphology observed by Scanning Electron Microscopy (SEM) and the characteristic diamond Raman peak were practically not affected by addition of CS2 in the range of 0.8–2.0% by volume. The electrical resistivity dependence due to CS2 addition showed a “down-and-up” curve with minimum resistivity of about 3.6 × 10−4 Ωcm. Hall mobility as high as 325.9 cm2V−1s−1 have been achieved. PIXE and XRF measurements showed that sulfur (100–400 ppm) was incorporated during the deposition independent of the CS2 added. Unintentional contaminations with Si, W, Cu and Cr have been detected. All the samples, measured by hot-point method and Hall effect, showed p-type characteristics.

In order to improve the dispersion of single-wall carbon nanotubes in a matrix of poly(3-hexylthiophene), this paper reports the modification of single-wall carbon nanotubes with COOH groups followed by reaction with cysteamine that introduced thiol groups along the tubes. The resulting modified single-wall carbon nanotubes were characterized by high resolution transmission electron microscopy, thermogravimetric analysis, X-ray photoelectron spectroscopy and Raman spectroscopy. The modified carbon nanotubes were applied, in combination with poly(3-hexylthiophene), in a bulk heterojunction solar cell. After passing through a post-treatment process to obtain debundied modified single-wall carbon nanotubes, solar cells with improved performance were obtained. After the treatment sequence, both the open circuit voltage and short-circuit current increased in comparison to the non-treated modified single-wall carbon nanotubes polymer solar cells.

Antivenom therapy has been ineffective in neutralizing the severe local fast developing tissue damage following snakebite envenoming. Herein, some effects of in situ helium neon (HeNe) laser irradiation on rat nerve-muscle preparation injected with Bothrops jararacussu venom are described. The tibialis anterior muscle was injected with venom diluted in 0.9% saline solution (60 microg/0.02 mL) or saline solution alone. Sixty minutes after venom injection, laser (HeNe) treatment was administered at three incident energy densities: dose 1, a single exposure of 3.5 J cm(-2); dose 2, three exposures of 3.5 J cm(-2); dose 3, a single exposure of 10.5 J cm(-2). Muscle function was assessed through twitch tension recordings whereas muscle damage was evaluated through histopathologic analysis, morphometry of area of tissue affected and creatine kinase (CK) serum levels, and compared to unirradiated muscles. Laser application at the dose of 3.5 J cm(-2) reduced the area of injury by 64% (15.9 +/- 1.5%vs 44.2 +/- 5.7%), decreased the neuromuscular blockade (NMB) by 62% (11.5 +/- 2.5%vs 30.4 +/- 5.2%) and reduced CK levels by 58% (from 455 +/- 4.5% to 190.3 +/- 23.4%) when compared with unirradiated controls. Dose 2 showed a poorer benefit than dose 1, and dose 3 was ineffective in preventing the venom effects. Measurements of the absorbance of unirradiated and irradiated venom solution showed no difference in absorption spectra. In addition, no difference in the intensity of partial NMB in nerve-muscle preparation was shown by unirradiated and irradiated venom. The results indicate that the laser light did not alter venom toxicity. We conclude that HeNe laser irradiation at a dosage of 3.5 J cm(-2) effectively reduces myonecrosis and the neuromuscular transmission blocking effect caused by B. jararacussu snake venom. Thus, low level laser therapy may be a promising tool to minimize the severity of some of the local effects of snake envenoming.

Field emission properties of hot filament chemical vapor deposited boron doped polycrystalline diamond have been studied. Doping level ( N B ) of different samples has been varied by the B/C concentration in the gas feed during the growth process and doping saturation has been observed for high B/C ratios. Threshold field ( E th ) for electron emission as function of B/C concentration has been measured, and the influences of grain boundaries, doping level and surface morphology on field emission properties have been investigated. Carrier transport through conductive grains and local emission properties of surface sites have been figured out to be two independent limiting effects in respect of field emission. Emitter current densities of 500 nA cm −2 were obtained using electric fields less than 8 V/μm.

The electrochemical properties of boron-doped diamond (BDD) polycrystalline films grown on tungsten wire substrates using ethanol as a precursor are described. The results obtained show that the use of ethanol improves the electrochemistry properties of "as-grown" BDD, as it minimizes the graphitic phase upon the surface of BDD, during the growth process. The BDD electrodes were characterized by Raman spectroscopy, scanning electronic microscopy, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The boron-doping levels of the films were estimated to be ∼10 20 B/cm 3 . The electro- chemical behavior was evaluated using the Fe CN

Nanostructured diamond doped with sulphur has been prepared using a hot-filament assisted chemical vapour deposition system fed with an ethyl alcohol, carbon disulfide, hydrogen, and argon mixture. The reduction of diamond grains to the nanoscale is relevant to create a network of defective grain boundaries which may be n-type doped to facilitate the transport and injection of electrons to the diamond grains located at the vacuum interface, enhancing the electron field-emission properties of the samples. The downsizing was produced by secondary nucleation and defects induced by sulphur and argon atoms in the chemical vapour deposition surface reactions. Sulphur also acts as an n-type dopant of diamond. Raman measurements show that the samples are nanodiamonds embedded in a matrix of graphite and disordered carbon grains and the morphology, revealed by field electron scanning microscopy, shows that the grains are in the range of 10 to 30 nm. The lowest threshold achieved for field emission was 13.20 V/μm.

Nanometric sponge-like structures have been prepared from the carburization of polyaniline-(emeradine salt) using a rapid immersion in hot-filament system fed with carbon dioxide, ethyl alcohol and argon. Fiber-like fragments of width in the range of 20 - 40 nm have been observed by field emission scanning electron microscopy (FESEM). Raman measurements suggested that benzenoid rings and amide were present in the carburized samples. Lowest threshold achieved for field emission was 23.5 V/μm.

Diamond coatings on pure titanium substrates are of interest for tribological and biomedical implants, among others, however, due to the different thermal expansion coefficients of the two materials, it is difficult to grow adherent thick diamond layers on Ti. The aim of this work was to investigate the influence of cooling down the substrate from the deposition temperature to the room temperature and then repeat the deposition process several times, on the quality and stress of the deposited diamond. This process intended to allow a partial relaxation of the diamond/Ti thermal stresses by accommodating the diamond nuclei onto the titanium carbide formed interlayer without detachment from the substrate. A hot-filament chemical vapor deposition system fed with ethanol, highly diluted in hydrogen was employed. Coatings of complete surface coverage with faceted grains of lateral size of about 4 μm and 0.38 GPa have been obtained.

Atomic force microscopy (AFM) and scanning electron microscopy (SEM) have been used to assess the 3D organization at molecular and structural resolution during the healing course of experimentally injured tibiae in unirradiated and irradiated rats. Rat tibiae were surgically injured and HeNe laser radiation was transcutaneously applied after surgery. Newly formed collagen fibrils at the injury site of the irradiated tibiae had acquired improved lamellar organization close to the spatial organization of mature intact bone. The HeNe laser doses accelerated bone neoformation.

The room temperature field-emission properties of tin oxide films have been studied. The samples were prepared on Si and glass substrates using the spray deposition technique using vapors of pentahydrated stannic chloride and ethanol diluted in hydrogen. Raman and Atomic force microscopy (AFM) analyses have been carried out to study the relation between the surface morphology and chemical composition with the emission properties of the samples. It was found that the deposition temperature has a dramatic influence on the electron field-emission properties. This effect is explained in terms of the temperature dependence of the hydrolysis reaction to form n -type SnO 2 grains and the increase of the film roughness with the temperature.

Atomic force microscopy (AFM) was used to study the morphology and coagulation of human blood cells in contact with solid surfaces. Blood was extracted from the veins of healthy adult donors and the samples were used immediately after extraction, deposited either on borosilicate glass or diamond substrates. Some blood samples were anti-coagulated by adding heparin for single cell AFM imaging. No chemicals were used for attaching or immobilizing the cells. The diamond substrates were produced by chemical vapour deposition (CVD diamond) using a hot-filament CVD system fed with ethanol highly diluted in hydrogen. AFM imaging of isolated cells (anti-coagulated by heparin) was only possible on the glass substrates due to the lack of adherence of the cells to the diamond surface. The coagulation results suggest that blood clotting on diamond produces a less rough surface than blood clotting on glass.

Nanostructured diamond and diamond-like materials having good field electron emission properties have been prepared using a hot-filament assisted chemical vapour deposition system fed with ethanol/hydrogen/helium mixtures. The changes in the structure of the samples were determined by the hydrogen content in the gas mixture and varied from samples of nanocrystalline diamond with graphitic connection between the grains (for helium concentration 40 vol %). Although the samples had such structural differences, low threshold values for electron field emission in vacuum were observed for representative samples of low and high hydrogen concentrations in the gas feed.

Background and Objectives Viper snake envenoming induces in the victims systemic coagulopathy, and severe local tissue damage such as edema, hemorrhage, intense pain, and myonecrosis. Serumtherapy and other first-aid managements are ineffective in neutralizing these local effects. The effects of the gallium-arsenide (Ga-As) laser irradiation on mice gastrocnemius injected intramuscularly (i.m.) with Bothrops moojeni snake venom were investigated. Study Design/Materials and Methods Macroscopical, histopatological, and myonecrosis quantification through serum creatine kinase (CK) evaluation was done at 3, 12, and 24 hours (two, five, and eight irradiation sessions, 4 J/cm2, 1 minute 32 seconds per period, respectively), were done after the venom or saline injection, and in venom-unirradiated mice. Results In unirradiated gastrocnemius, the venom induced massive hemorrhage, vascular congestion, time-progressing myonecrosis, edema, abundant inflammatory infiltrate, and high CK serum levels. Ga-As irradiation significantly decreased the amount of myonecrosis in all the periods tested (P

A hot-filament chemical vapor deposition system fed with ethanol highly diluted in hydrogen was employed to grow self-supported diamond tubes with external diameter to wall thickness aspect ratio between ∼5 and ∼60, and 30 mm in length. Tungsten wires of diameters between 238 and 586 μm were used as substrates for the deposition, and were subsequently completely removed by etching, to leave stress-free diamond tubes, as demonstrated by micro-Raman spectroscopy. Scanning electron microscopy revealed cross-sections with diamond grains growing radially, forming well-faceted top-surface grains on the tube's external surface.

Direct syntheses of carbon structures including nanodiamond, microdiamond and diamond-like carbon (DLC) on silicon wafers by liquid phase electro-deposition are presented. The solution (ethanol/water) was employed as electrolyte at different concentration levels. Assays were carried out maintaining constant the electric potential between the silicon electrodes in the range of (80−300 V) at current density of approximately 2.0 mA/cm 2 . Scanning electron microscopy showed that non-uniform, smooth and heterogeneous structures were produced. The structural composition was evaluated by micro-Raman spectroscopy. A mechanism for the formation of sp3 and sp2 hybridizations is proposed.

The fabrication and characterization of ‘self-supporting’ diamond tubes grown by chemical vapor deposition (CVD) are reported. Diamond layers were deposited onto tungsten wires with diameters of 238 μm; the tungsten cores were subsequently completely removed by etching to leave ‘self-supporting’ diamond tubes with a diameter of approximately 400 μm and length of 20 mm. A hot-filament CVD system fed with ethanol highly diluted in hydrogen was employed. Growth rates of 7.8 μm h −1 have been measured and incubation times >3 h have been estimated. Scanning electron microscopy of cross-sections revealed columnar structures, which terminate on sharp (111) facets on the tube's external surface. Raman spectroscopy showed that the tube structure is predominantly composed of CC sp 3 bonds, with intrinsic tensile stresses.

Atomic force microscopy (AFM) was used to study the relation between the surface morphology of SnO2 coatings with their room-temperature resistivities. A hot-plate chemical vapor deposition system fed with vapors of tin tetrachloride and methyl alcohol diluted in a nitrogen gas carrier was used to deposit the SnO2 films on soda-lime glass. It was found that above a critical deposition temperature (T=643 K), the film resistivity reaches its minimum value, which is almost constant over the wide range of the SnCl4 vapor concentration used. AFM revealed that the increase in the deposition temperature increased the grain size and that the surface roughness increases with greater SnCl4 vapor concentration. Therefore films of the same resistivity (deposited at the same temperature) may have different roughnesses.

Diamond-like carbon films were grown on pyrolised bamboo substrates by hot filament-chemical vapor deposition from ethanol/hydrogen mixtures. Different stages of deposition of films grown on untreated substrates and substrates seeded with diamond dust were compared. Changes in film morphology and structure under changes in these parameters were investigated using scanning electron microscopy and Raman spectroscopy. Diamond-like carbon (DLC) with ball-like morphology on the micrometer scale and glassy DLC with a stacked planar structure were observed for depositions of >2 h on unseeded and seeded substrates, respectively. Gasification of the fibers by hydrogen in the early stages of growth may play a role in film growth, but this requires further study. Nevertheless, DLC films can be grown on pyrolised bamboo substrates, which suggests that other carbonaceous substrates for film fabrication by hot-filament chemical vapor deposition also merit systematic investigation.

In this paper, we discuss the experimental results of the fabrication of porous diamond/porous silicon and porous diamond structures by chemical vapor deposition of diamond over a skeleton of porous silicon, replicating the porous surface geometry around the Si pores and also creating new porous diamond structures. Scanning electron microscopy (SEM) revealed that the diamond nuclei are deposited on the top of the porous silicon skeleton, forming isolated grains in the first nucleation stages, and then growing like the usual structure of most ceramic materials, making a self-sustained porous diamond structure. Raman spectroscopy revealed that the diamond films are of good quality, close to that of diamond films grown on crystalline silicon.

Porous diamond and porous carbon structures were deposited by hot-filament chemical vapor deposition (HFCVD) onto natural fibers derived from pyrolized bamboo substrates. 'Seeding' of the substrate with diamond dust prior the HFCVD process, allowed the fabrication of porous diamond, replicating the porous surface geometry of the bamboo fibers. As indicated by scanning electron microscopy and Raman spectroscopy, respectively, the films deposited on 'seeded' substrates are poly-faceted and are composed predominantly of C-C sp bonds. 2001 Elsevier Science B.V. All rights reserved. 3

Tungsten wires were used as templates for the deposition of tubes of micro-crystalline diamond or of 'spongy' carbon nano- structures. A hot-filament chemical vapor deposition system fed with highly diluted ethanol in hydrogen and argon was used. Argon was intentionally added to the feed at different concentrations to affect the crystalline growth. As the argon concentration was increased beyond 65 vol.% in the reactor feed, the morphology drastically changed from micro-crystalline diamond to complex carbon nano-structures. While the samples produced at argon concentrations of 65 vol.% or less resulted in a radial columnar structure of micro-crystalline diamond, the samples produced at higher argon concentrations showed radial flaws and 'spongy' structures. Each type of morphology is of potential interest for the use of these tubes as molecular filters or in electron emission devices. 2001 Elsevier Science B.V. All rights reserved.

Diamond-coated stainless-steel blades promise smoother cutting and greater durability. In this work the feasibility of coating stainless-steel blades with diamond and diamond-like carbon (DLC) by hot-filament chemical vapor deposition was investigated. Two pre-deposition seeding procedures using either diamond dust or oil droplets were tested. As revealed by scanning electron microscopy and Raman spectroscopy, both seeding methods allow the production of diamond films also containing some DLC. The oil-seeding method, however, is the most successful in promoting diamond nucleation. Film deposition along the blade edge is also enhanced by its curvature.

The usual design of field-emission displays (FEDs) often results in high vacuum pressure gradients inside the glass plates of the device, and this is the main limitation to the widespread availability of large area FEDs. In this paper, we perform theoretical calculations using the finite element method for determining the pressure distributions in several pumping configurations, including a new FED configuration known as porous FED or pFED. The approach here is capable of clarifying the design issues influencing the final pressure relevant to the field-emission display devices.

Atomic force microscopy (AFM) was used to comparatively study the structure of the bone matrix of rat tibia from an intact region with that from regions submitted to surgical injury. We used young male adult rats (Wistar), with corporal masses between 250 and 300 g. Each injury was provoked by drilling a 1.5-mm-diam hole in one cortical tibia surface. The healing course was monitored at 8 and 15 days after the injury. Atomic force microscopy images, at different magnifications, allowed the identification of the time dependence of the osteoblast activity, measured by the increase in the area of neoformed primary bone and in the organization of the collagen fibers of the bone matrix. Characterization of the natural recovery of the damaged bone tissue by AFM is potentially of great importance because it allows the comparison of natural recovery processes with those induced by medicines and other therapeutic procedures.

Diamond films of small roughness have been deposited onto thermally oxidized Si substrates by a process of anisotropic crystalline growth induced by nitrogen in a hot-filament chemical vapor deposition reactor. Ethanol (C2H5OH), diluted in hydrogen and nitrogen, was used as the source of carbon. At high concentrations, nitrogen tends to suppress the diamond growth in the 〈100〉 direction, which allows the growth of square mesoscopic-like crystals (“plates”) of large area in the directions parallel to the surface of the substrate. These plates stack upon each other, forming a thick diamond coating of uniform thickness. Analysis of the films made by micro-Raman spectroscopy and atomic force microscopy revealed that it is possible to obtain diamond coatings of high quality with a roughness comparable to that of the SiO2 at the diamond/SiO2 interface, and of nanometric roughness on the surface of the plates. A model to explain the morphology of the plates based on the microscopic mechanisms that involve the possible passivation of the (100) plane and an increase of vacancies by nitrogen is also discussed.

Micro-crystalline diamond films and nano-carbon structures in the form of wires have been grown by the introduction of argon at very high concentrations (60%–87.5% vol Ar) into the feed mixture (ethanol and hydrogen) of a hot-filament chemical vapor deposition reactor. The argon, in addition to acting as an inert diluent, also modified the kinetics of the carbon deposition process; its presence apparently minimized the deposition of intergranular hydrogenated species, induced an increase in the number of flaws between the diamond grains, increased the porosity of the films, and formed new carbon structures. Well-faceted diamond films, diamond-like carbon (DLC) balls, spongy-like wires, and multilayer structures were observed at different concentrations of Ar. Raman spectroscopy of the deposited material showed that structures of high quality diamond (60%–65% vol Ar) and carbon structures related to DLC, fullerenes and carbon nanotubes, may be deposited by this process.

In this work, we undertook a unique study of the growth kinetics of diamond in a hot-filament chemical vapor deposition (HF-CVD) reactor fed with the mixture C2H5OH+H2+Ne, varying the concentration of Ne from 0% vol. to 60% vol. Images obtained by scanning electron microscopy (SEM) show that the addition of neon influenced the grain morphology, but diamond films with well-defined crystalline facets and good Raman quality were obtained up to a concentration of 60% vol. Ne. We verified that neon changes the diamond growth mechanism in the space between the grains, probably by the minimization of the hydrogenation kinetics in these regions. There is an apparent increase in the grain size and an increase in the flaws between the grains. The presence of Ne in the feed mixture also induces a broadening of the Raman peak characteristic of diamond, and this broadening may be related to an increase in the density of vacancies within the diamond grains.

We present experimental results of chemical vapor deposition (CVD) diamond growth from ethanol vapor with the substitution of hydrogen by helium in concentrations varying from 0 to 95 vol.% He. Scanning electron microscopy (SEM) analysis revealed that the addition of helium to the gas phase influenced the growth rate and film structure. The deposition rate of diamond increases up to a helium concentration of 40 vol.% and then decreases. We attribute this behavior to an increase in the density of vacancies in the film or to a change in the reaction kinetics provoked by the chemical inertness of helium. Diamond films with well-defined crystalline facets and of good quality (measured by Raman spectroscopy) were obtained with the addition of up to 70 vol.% He. Use of helium also provokes an increase in film porosity, with the appearance of a strong room temperature photoluminescence with a Gaussian peak at approximately 635 nm. The intensity of the luminescence increases with the concentration of helium and is probably related to nanoporous defects introduced into the diamond structure.

Carbon nitride films were prepared by combined hot filament (HF) and radiofrequency (RF) plasma enhanced chemical vapor deposition techniques from three mixtures, C2H6–N2–Ar, C2H4–N2–Ar and C2H2–N2–Ar, denominated M1, M2 and M3, respectively. Depositions were carried out in a vacuum chamber fitted with two parallel-plate electrodes driven by a 40-MHz generator and a Ta filament resistively heated by an AC power supply. The deposition rates, composition and structural properties were compared for films deposited using the same flow rates of the hydrocarbon, nitrogen and argon mixture fed to the vacuum chamber, and the same radiofrequency and filament power. The deposition rate, R, was determined by dividing the film height, obtained using a profilemeter, by the deposition time. Reflection infrared and Raman spectroscopies were used to investigate the molecular structure while Rutherford backscattering spectroscopy was used to determine the elemental composition. Using combined RF and HF excitation: (i) R increased from mixture M1 to mixture M3; (ii) the concentration of CC bonds was higher in the films deposited in the M3 mixture; and (iii) the incorporation of nitrogen, determined by the nitrogen to carbon atomic ratio, increased from mixture M1 to M3. For the mixture M3, a comparison of the film structure and deposition rate of films produced using HF, RF and combined HF–RF excitation, was made. Both R and the concentration of C–H bonds were higher when HF excitation alone was used. An interpretation of the role of the plasma in the decrease in R is suggested. The influence of the degree of saturation of the hydrocarbon molecules in each mixture on R and on the film structure is highlighted. The Raman spectroscopy results revealed that diamond-like carbon is formed under HF excitation while the use of RF, alone or combined with HF, eliminates the diamond phases.

We studied the effects on the growth kinetics and properties of diamond and carbon-like diamond films obtained by the introduction of argon at low to high concentrations (0–85 vol.% Ar) into the feed mixture (ethanol and hydrogen) of a hot-filament chemical vapor deposition (CVD) reactor. Scanning electron microscopy (SEM) analysis revealed that the addition of argon induces an increase in the diamond grain size, and increases the flaws between the grains and the density of vacancy defects. Well-faceted diamond films of good quality (measured by Raman spectroscopy) have been obtained using up to 65 vol.% of argon in the gaseous mixture, while higher concentrations (85 vol.% Ar) produce diamond-like carbon or other complex carbon structures. We also observed an increase in the diamond growth rate with argon addition that was associated with an increase in carbon free radicals (up to ∼40 vol.% Ar) or to the increase in the filament temperature necessary to keep the substrate temperature constant at higher Ar concentrations (above ∼40 vol.% Ar). Room temperature photoluminescence spectroscopy also confirmed that argon addition increases the density of vacancy defects in the diamond structure.

In this work, we studied the properties of thin nanoporous carbon coatings on very thick porous silicon (PS) layers of very high porosity. The PS was obtained by etching pores into crystalline Si wafers in a process controlled to prevent crack formation during etching and drying. The nanoporous carbon was made by dipping the PS samples in diluted polyvinyl alcohol and submitting the coating to pyrolysis at different temperatures (in the 513–843 K range). The porous carbon coatings obtained on porous silicon using this method presented good adherence, uniform thickness and good optical transparency, the greatest luminescence intensity being obtained at a pyrolysis temperature of 513 K. Such a composite nanoporous structure of two type IV materials may find a large number of future applications, ranging from luminescent devices to molecular sieves.

Diamond growth on non-diamond substrates initially requires a heterogeneous nucleation step on the substrate surface and, depending on the substrate material, the nucleation time may be very long and the nuclei density may also be very low, compromising the film quality. Seeding of substrates prior to chemical vapor deposition (CVD), typically using diamond grains, is commonly employed to increase nucleation of the growing film. Alternative nucleation methods are of great interest. In this work, we demonstrate the feasibility of using natural hematite to increase nucleation on silicon. This mineral in lamellae form is very soft and minimizes damage to the substrate surface. Hematite grains of a silica-rich phase improved the crystalline faceting and the coalescence of the growing diamond, indicating that complex oxides, such as iron silicates, may favor diamond nucleation. The nucleation density was approximately 0.8 × 10 6 nuclei cm -2 , which is a thousand times greater than that obtained on the 'unseeded' silicon surface. Samples 'seeded' with hematite grains of the silica-rich phase presented sharper peaks at 1332 cm -1 (higher aspect-ratio), indicating a higher diamond quality.

Columnar porous silicon (PS) with deep pores has been prepared by laser-assisted electrochemistry of n- type c-Si wafers immersed in HF/C 2 H 5 OH/H 2 O mixtures of different proportions. Analysis of the PS by micro-Raman spectroscopy was undertaken simultaneously with micro-photoluminescence spectroscopy to enable correlation of the characteristics of the luminescence spectra with the probable emission structures. In addition, the cross-sectional surfaces of the samples were studied by micro-Raman and micro-photoluminescence spectroscopy to compare the luminescence of the structures present in the bulk of the PS with that of the structures of the top surface. The results suggest that the strong luminescence observed in these PS films originates from structures present in the bulk of the PS, and not from surface structures. Morphological data obtained by scanning electron microscopy (SEM) and atomic force microscopy (AFM) are also discussed.