Carbon Tip Research Articles

Breakdown of plane-wave-based theories of field emission from a subnanometer-radius tip

We present a combined experimental and theoretical study of field electron emission from an ultrasharp carbon tip with a subnanometer radius formed by a field-emission-induced structural modification of a diamond needle-like microcrystallite. The tip dimensions were measured by high-resolution transmission electron microscopy and used to calculate the potential distribution outside the emitter. Substitution of the calculated field into the Fowler-Nordheim (FN) theory and the more refined theory based on the Simmons equation overestimate the field emission current by six and five orders, respectively. We show that such a strong discrepancy is due to the incorrect use of plane wavefunctions to describe electrons inside a subnanometer emitter. We present a theory based on more realistic non-planar wavefunctions, which takes into account the effect of localization and one-dimensional density of states inside the emitter. These modifications of the FN theory allowed us to obtain a good order-of-magnitude agreement with the experimental values of the field emission current. The presented results are of great practical importance, since field emitters with nanometer radius are intensively studied experimentally and are the basis of state-of-the-art vacuum nanoelectronic devices.

Analysis of trace phytoavailable heavy metals in saline soil extract by one-step electroextraction coupled with in situ desorption microplasma optical emission spectrometry

On-site and sensitive analysis of phytoavailable heavy metals is the key to fast evaluate the pollution incidents, while the development of convenient and efficient sample introduction approaches against matrix interference is crucial to improve the performances of field-deployable instruments. Herein, trace phytoavailable heavy metals in soil are first extracted by 0.1 M NaNO3, afterwards adsorbed onto an activated carbon tip via electroextraction (EE), and finally analyzed by dielectric barrier discharge (DBD) microplasma optical emission spectrometry (OES) via in situ desorption. The activated carbon tip is not only able to extract heavy metals from alkali metals/alkaline earth metals matrix, resisting the interference of coexisting anions and non-electroactive species in saline soil extract, but also significantly improves the detection sensitivity of subsequent DBD-OES analysis by increasing loading amounts of analytes. Taking the key heavy metals pollution as model, the detection limits of Cd, Zn, Cu and Pb reach 0.8, 2.3, 6.0 and 4.5 μg kg−1, respectively, and precisions are within 2.7–4.6%. The accuracy and practicability of the present miniaturized EE-DBD-OES device have been verified by measuring several certified reference materials and real soil samples, providing a promising tool for convenient and sensitive analysis of trace phytoavailable heavy metals in soil.

The Characteristics and Potency of Limestone-based carbonate hydroxyapatite to Viability and Proliferation of Human Umbilical Cord Mesenchymal Stem Cell

Background: Limestone primarily consists of CaCO3 (calcium carbonate), which have a similarity to one of human bone component, hydroxyapatite (HA), an element of apatite group (Ca10(PO4)6(OH)2). There were several setbacks in the use of artificial hydroxyapatite in the bone repair process; one of them was its relatively higher crystallinity level compared to those of human bone apatite. The addition of carbonate element to hydroxyapatite could improve its characteristics, such as increasing the solubility, decreasing the crystallinity, and changing the morphology of the crystal. That caused carbonate hydroxyapatite is preferable to help in the bone repair process. Aims: This study aimed to find the effect of limestone-based CHA on viability and proliferation of hUMSCs, thus discovering the potential of CHA as a bone graft biomaterial candidate derived from limestone. Methods: This study used FTIR, EDX, and XRD assays to CHA powder sample derived from limestone found in Padalarang and Cirebon extracted by BBK. Two grams of the sample were placed in the sample holder and examined by computer software. EDX assay was conducted three times in three different points, and the means were recorded. In the XRD assay, a carbon tip was put to the sample holder to allow sample attachment. The recorded data was compared to JCPDS data. Toxicity and proliferation examination of CHA were conducted through MTT assay in human umbilical cord mesenchymal stem cell (hUCMSC) cell lines with four different doses: 50µg/ml, 25µg/ml, 12,5µg/ml, and 6,25µg/ml. Results: Limestone-based CA has hydroxyl (OH-), phosphate (PO42-), and carbonate (CO32-) functional groups. It has crystal particle formation and consists of O, Ca, and P elements. The result of the MTT assay showed limestone-based CHA is not toxic in all concentrations and has the proliferative ability. There were significant differences between the control and treatment groups. Conclusion: CHA has OH-, PO42-, and CO32- function group. It has crystal particle formation and O, Ca, and P elements as its composition, with a Ca/P ratio of 1,67. It shows no toxicity to hUCMSC in all doses and has the ability to stimulate hUCMSC proliferation.

Carbon powder-filled microelectrode: An easy-to-fabricate probe for cellular electrochemistry

Carbon fiber and carbon fiber disc microelectrodes are widely used for electrochemical detection of biochemicals released from cells. However, fabricating these types of microelectrodes is difficult and time-consuming. Here, we report an easy-to-fabricate, carbon powder-filled microelectrode consisting of a pulled glass capillary backfilled with carbon powder. Carbon tip size and responsiveness can be controlled by adjusting the settings of the puller. Carbon powder-filled microelectrodes with tip opening diameters of 7–24 μm detected sub-micromolar to sub-millimolar levels of dopamine and catecholamines released from PC-12 cells. This simple microelectrode should promote further work on cellular and tissue electrochemistry.

Carbon tip aperture cantilevers: Fabrication & features in near-field magneto-optical imaging

Improving the ways of magnetic structure investigation with the lowest possible resolution is important in the study and practical implementation of fundamental magnetism. Here we discuss one of the most modern magneto-optical method of domain structure (DS) imaging, scanning near-field magneto-optical microscopy (SNMOM), and propose the new technology based on focused ion beam (FIB) treatment to produce aperture cantilevers with carbon hollow pyramid tip (ACCT). Estimated ACCT light transmission coefficients show better results compare to commonly used aperture silicon cantilevers. By measuring the polarization characteristics of aperture with diameter from 83 to 263 nm, we illustrate the possibility of ACCT to maintain a liner polarization of transmitted light. Testing of ACCT in atomic-force and SNMOM modes shows that ACCT are the effective tool in near-field imaging. Features of morphology and DS of Bi-substituted iron garnet (Bi: IG) films synthesized and used as the test objects, including DS peculiarities of 100 nm-size, is revealed.

Assessment of implant surface and instrument insert changes due to instrumentation with different tips for ultrasonic-driven debridement

BackgroundTo assess the changes of implant surfaces of different roughness after instrumentation with ultrasonic-driven scaler tips of different materials.MethodsExperiments were performed on two moderately rough surfaces (I—Inicell® and II—SLA®), one surface without pre-treatment (III) and one smooth machined surface (IV). Scaler tips made of steel (A), PEEK (B), titanium (C), carbon (D) and resin (E) were used for instrumentation with a standardized pressure of 100 g for ten seconds and under continuous automatic motion. Each combination of scaler tip and implant surface was performed three times on 8 titanium discs. After instrumentation roughness was assessed by profilometry, morphological changes were assessed by scanning electron microscopy, and element distribution on the utmost surface by energy dispersive X-ray spectroscopy.ResultsThe surface roughness of discs I and II were significantly reduced by instrumentation with all tips except E. For disc III and IV roughness was enhanced by tip A and C and, only for IV, by tip D. Instrumentation with tips B, D and E left extensive residuals on surface I, II and III. The element analysis of these deposits proved consistent with the elemental composition of the respective tip materials.ConclusionAll ultrasonic instruments led to microscopic alterations of all types of implants surfaces assessed in the present study. The least change of implant surfaces might result from resin or carbon tips on machined surfaces.

Treatment of uterine evasion by faradization

According to the author, electricity in most cases of uterine evasion is an excellent medical agent. It satisfies all three indications most often encountered in this suffering, counteracts the formation of dense exudates, promotes metabolism and restores the contractility of the ligaments that support the uterus. The author uses the apparatus of the Chardin system, the electrodes are a uterine probe with a carbon tip, described by Apostoli, and a zinc plate wrapped in felt and suede.

Cover Feature: Elucidating the Performance Limitations of Alkaline Electrolyte Membrane Electrolysis: Dominance of Anion Concentration in Membrane Electrode Assembly (ChemElectroChem 19/2020)

The Cover Feature illustrates the fabrication of a perovskite solar cell (PSC) based on lead fixation from an electrolyte as an electrodeposited PbO2 film, which is further converted to PbBr2 using gaseous HBr. Finally, PbBr2 is converted into CsPbBr3 using spin-coated CsBr. A pressed carbon tip with a calibrated area was used to close the circuit in the PSC. This method avoids the spill of toxic lead compounds compared with traditional spin-coating. More information can be found in the Article by D. Ramírez et al.

Quantitative measurement of nanofriction between PMMA thin films and various AFM probes

This study reports the quantitative, precise and accurate results of nanoscale friction measurements with the use of an Atomic Force Microscope calibrated with a precise nanoforce sensor. For this purpose, three samples of spin-coated thin Polymethylmethacrylate (PMMA) films were prepared with the following thicknesses: 235, 343, and 513 nm. Three different AFM probes were used for the friction measurements: with diamond-like carbon (DLC) tip with a small (15 nm) or big (2 µm) tip radius, and a reference silicon tip with a small (8 nm) radius. The results show that in all of the studied cases, the coefficient of friction strongly depends on the applied load, being much higher for a lower load. Furthermore, a strong relation of the friction force on the cantilever’s geometry, the scanning velocity, and the film thickness was observed.

Degradation of oral biofilms by zerumbone from Zingiber zerumbet (L.)

Oral biofilms manifestated in dental plaques can lead to further pathogenically condition such as caries. In a search for a new effective anti dental plaque from natural resources, zerumbone, an essential oil component of Zingiber zerumbet (L.) (Zingiberaceae) was reported to be active against biofilms of aerobic microbes. The purpose of this study was to investigate the planktonic growth, biofilm inhibition and degradation effects of zerumbone on dental plaque initiator microbes, Streptococcus sanguinis and Lactobacillus acidophilus in an anaerobic environment. The zerumbone was isolated from Z. zerumbet using distillation technique, followed by crystallization with n-hexane. Gas Chromatography- Mass Spectrometry was applied for compound's identification. Planktonic and biofilm degradation were observed in vitro by using microdilution techniques on 96 microtiter plates to determine Minimum Inhibition Concentration (MIC50) and Minimum Biofilm Eliminating Concentration (MBEC50) values. Crystal violet was used as a stain and Optical Density (OD) value was measured at 595 nm with anaerobic condition. This condition was made by anaerogen gas pack in the chamber. Modification of biofilm morphology on surface was observed by Scanning Electron Microscopy (SEM) and for the preparation sample for SEM is used the coating process with carbon tip. The results showed that zerumbone has the degradation effect on S. sanguinis and L. acidophillus single spesies biofilms. The values of MBEC50of zerumbone on S. sanguinis, L. acidophilus) were 0.5% v/v and 1%, respectively. SEM images showed membrane cell disruption of S. sanguinis, L. acidophilus following zerumbone exposure. Zerumbone had degradation effect on S. sanguinis and L. acidophilus biofilms and had a great potential in anti caries.

Light polarization and intensity behaviour in aperture cantilevers with carbon tip created by focused ion beam

Modern atomic force microscopy (AFM) techniques and their combination with other methods give us a possibility to investigate the same samples from the new side at nano-scale. One of very promising combinations is polarization near field microscopy integrated into AFM tool. It allows one to make topography imaging by standard AFM tool and optical magnetic structure imaging by magneto-optical method simultaneously. Moreover, this combination gives synergy effect on both methods by improving their weak sides: elimination of magnetic influence of magnetic force microscopy on the sample, on the one hand, and overcoming the diffraction limit of the magneto-optical microscopy, on another hand. The cantilevers play a very important role in this combination of the methods since they interact with the surface and allow focusing the laser beam to the sample in near field mode. The geometry and other parameters of cantilevers are determined as a result of the combined methods implementation. Authors investigate the new type of carbon-tips aperture cantilevers for AFM and high resolution magneto-optical combination.

Talks

The expression of human chorionic gonadotropin (hCG) is com-monly associated with a variety of cancers including testicular,bladder and gestational trophoblast diseases. All trophoblastictumours secrete very high amounts of hCG however hyperglyco-sylated form of hCG was found to be highly elevated in chorio-carcinoma patients. Current analytical methods, measuringbranched N-linked glycans in hCG, involve use of antibodieswhich may cause uncertainty due to issues of antibody specificity.In this project, highly sensitive and robust method to identify N-linked glycans, based on their specific chemical composition andmass tolerance, was developed. It was applied to variety of hCGforms, including hCG from pregnancy, choriocarcinoma andrecombinant hCG. hCG and its varied forms, with freebhCG,were isolated using IgG-coupled magnetic beads. N-linked gly-cans were then isolated from hCG by denaturation, reduction,alkylation (100°C, 10mM DTT, 20mM IAA) followed by degly-cosylation (PNGase, 37°C, 20h) and purification using porousgraphite carbon tips (Hypercarb). MALDI IT-TOF MS was usedto separate resulting glycans, which were then characterised usingProtein Scape software. Glycan peaks were reported, m/z 900–5,000 (Da), and carbohydrate library with precise glycan searchparameters (GlycoQuest, Bruker) was designed. A series of gly-cans were successfully identified from selected hCG sources, andsignificant differences in repertoire of glycans composition weredetected. Alteration in cellular glycosylation of proteins con-tribute to cancer metastasis, therefore strategies to understandtumour glycome and glycoproteome provide diagnostic potential,and targets for therapeutic intervention. Rapid and efficientdetection method of specific hCG glycoforms, from crudepatients urine samples, could help to speed and improve diagno-sis of hCG associated cancers including choriocarcinoma andnon-trophoblastic malignancies.

Carbon Nanospikes: Synthesis, characterization and application for high resolution AFM

We present a detailed study of synthesis, structural characterization of sharp, spike-like carbon structures and its application for high-resolution atomic-force microscopy (AFM) measurements of biological molecules. The probes are obtained by chemical vapor deposition of spike-like carbon structures on the apexes of common AFM silicon probes. The deposition process is carried out in carbonaceous gas mixture activated by a direct-current discharge. It was revealed by electron microscopy and Raman spectroscopy that the having dimensions at their ends of few nanometers the structures consist of amorphous carbon. The carbon spikes demonstrate high efficiency and resolutions in AFM studies of biological objects. Sub-molecular resolution is demonstrated on the samples of DNA and streptavidin molecules in AFM measurements with the ultra-sharp carbon tips.

Effects of far infrared radiation by isotropic high-density carbon on the human oral mucosa

ObjectivesWound healing of the oral mucosal epithelium through the application of far infrared radiation emitted by isotropic high-density carbon was investigated in order to clarify the preventive and therapeutic effects of isotropic high-density carbon on oral mucosal injury. Materials and methodsA carbon massager with an isotropic high-density carbon tip was used. Far infrared radiation was applied to the human buccal mucosal squamous cell carcinoma cell line, HO-1-N-1 using a carbon massager, and cell growth factors and heat shock protein levels were measured using real-time RT-PCR and ELISA. Far infrared radiation was applied to oral mucosal injury in SD rats over time using the carbon massager, and its effects were examined by HE staining and immunostaining. The immunostaining positive rate was measured and analyzed using image analysis software. ResultsFar infrared radiation induced stronger mRNA expression and higher HSP27 and HSP70 protein levels on real-time RT-PCR and ELISA than in the control group. The far infrared radiation of oral mucosal injury in rats induced strong positive reactions, and positive rates for Ki67, HSP27, and HSP70 were higher than those in the control group. ConclusionsThe treatment of oral mucosal injury with far infrared radiation emitted by isotropic high-density carbon appears to have promoted heat shock protein production and induced regenerative reactions more strongly than in the control group.

A novel carbon tipped single micro-optrode for combined optogenetics and electrophysiology.

Optical microelectrodes (optrodes) are used in neuroscience to transmit light into the brain of a genetically modified animal to evoke and record electrical activity from light-sensitive neurons. Our novel micro-optrode solution integrates a light-transmitting 125 micrometer optical fiber and a 9 micrometer carbon monofilament to form an electrical lead element, which is contained in a borosilicate glass sheathing coaxial arrangement ending with a micrometer-sized carbon tip. This novel unit design is stiff and slender enough to be used for targeting deep brain areas, and may cause less tissue damage compared with previous models. The center-positioned carbon fiber is less prone to light-induced artifacts than side-lit metal microelectrodes previously presented. The carbon tip is capable of not only recording electrical signals of neuronal origin but can also provide valuable surface area for electron transfer, which is essential in electrochemical (voltammetry, amperometry) or microbiosensor applications. We present details of design and manufacture as well as operational examples of the newly developed single micro-optrode, which includes assessments of 1) carbon tip length–impedance relationship, 2) light transmission capabilities, 3) photoelectric artifacts in carbon fibers, 4) responses to dopamine using fast-scan cyclic voltammetry in vivo, and 5) optogenetic stimulation and spike or local field potential recording from the rat brain transfected with channelrhodopsin-2. With this work, we demonstrate that our novel carbon tipped single micro-optrode may open up new avenues for use in optogenetic stimulation when needing to be combined with extracellular recording, electrochemical, or microbiosensor measurements performed on a millisecond basis.

Suppressing Nanoscale Wear by Graphene/Graphene Interfacial Contact Architecture: A Molecular Dynamics Study.

Nanoscale wear is one of the key factors hindering the performance and lifetime of micro- and nanosystems, such as the scanning tip wear in atomic force microscopy (AFM), the head-disk interface in magnetic storage system, and the moving components in micro- or nanoelectromechanical systems (MEMS/NEMS). Here, we propose to construct the graphene/graphene interfacial architecture to suppress the nanoscale wear. Molecular dynamics simulations show that the atomic roughness of the sliding surfaces with either stepped or amorphous structure can lead to strong inhomogeneity of the local contact pressure distribution. By coating graphene on both sides of the frictional surfaces, the local contact pressure fluctuations due to the atomic roughness are suppressed. Moreover, this trend is more evident with the increasing layer number of the graphene coating. Furthermore, the nanoscratching simulation suggests that the rupture of graphene is driven by the inhomogeneous pressure distribution-induced lateral atomic interlocking between the rough tip and substrate and the consequent in-plane lattice deformation and C-C bond breaking during sliding. By coating graphene on the rough amorphous carbon tip, the critical normal load for wear failure of graphene is significantly increased, due to the weakening effect of the atomic interlocking by improving the contact conditions with atomically smooth graphene/graphene sliding interface. This investigation reveals a strategy for reducing nanowear by suppressing the local contact pressure fluctuations via graphene/graphene sliding interface architecture, which provides a theoretical guidance for designing wear-resistant coatings for the longevity of AFM probes and MEMS/NEMS systems.

Custom-Designed Glassy Carbon Tips for Atomic Force Microscopy.

Glassy carbon is a graphenic form of elemental carbon obtained from pyrolysis of carbon-rich precursor polymers that can be patterned using various lithographic techniques. It is electrically and thermally conductive, mechanically strong, light, corrosion resistant and easy to functionalize. These properties render it very suitable for Carbon-microelectromechanical systems (Carbon-MEMS) and nanoelectromechanical systems (Carbon-NEMS) applications. Here we report on the fabrication and characterization of fully operational, microfabricated glassy carbon nano-tips for Atomic Force Microscopy (AFM). These tips are 3D-printed on to micro-machined silicon cantilevers by Two-Photon Polymerization (2PP) of acrylate-based photopolymers (commercially known as IP-series resists), followed by their carbonization employing controlled pyrolysis, which shrinks the patterned structure by ≥98% in volume. Tip performance and robustness during contact and dynamic AFM modes are validated by morphology and wear tests. The design and pyrolysis process optimization performed for this work indicate which parameters require special attention when IP-series polymers are used for the fabrication of Carbon-MEMS and NEMS. Microstructural characterization of the resulting material confirms that it features a frozen percolated network of graphene sheets accompanied by disordered carbon and voids, similar to typical glassy carbons. The presented facile fabrication method can be employed for obtaining a variety of 3D glassy carbon nanostructures starting from the stereolithographic designs provided by the user.

On intense proton beam generation and transport in hollow cones

Proton generation, transport and interaction with hollow cone targets are investigated by means of two-dimensional PIC simulations. A scaled-down hollow cone with gold walls, a carbon tip and a curved hydrogen foil inside the cone has been considered. Proton acceleration is driven by a 1020 W·cm−2 and 1 ps laser pulse focused on the hydrogen foil. Simulations show an important surface current at the cone walls which generates a magnetic field. This magnetic field is dragged by the quasi-neutral plasma formed by fast protons and co-moving electrons when they propagate towards the cone tip. As a result, a tens of kT Bz field is set up at the cone tip, which is strong enough to deflect the protons and increase the beam divergence substantially. We propose using heavy materials at the cone tip and increasing the laser intensity in order to mitigate magnetic field generation and proton beam divergence.

Detection of individual nanoparticle impacts using etched carbon nanoelectrodes

A rapid and reliable nanofabrication route produces electrodes with beneficial properties for electrochemistry based on stochastic nanoparticle collision events. Carbon nanoelectrodes are etched to expose conical carbon tips which present an increased surface area for the detection of nanoparticle impacts. The tuneable electrode size as well as the conical geometry allow to increase the observed particle impact frequency while maintaining low background noise. Moreover, anodic particle coulometry for the sizing of silver nanoparticles shows that the detected impacts are representative of the polydisperse particle population.

A Mathematical Model for Determining Carbon Coating Thickness and Its Application in Electron Probe Microanalysis.

In electron probe microanalysis where materials are coated with a thin conductive carbon coat before analysis, the X-ray intensity detected from a specimen may be affected to various degrees by the thickness of the carbon coating. Differences in the carbon film thickness between specimens and standards may lead to errors in analytical results, particular for lower energy X-rays. In this study, we demonstrate that the location and the distance of the specimen relative to the carbon tip in the coating chamber can affect the thickness of the carbon film produced on the specimen surface during carbon coating. The closer the specimen is to the carbon tip contacting point, the thicker is the carbon film deposited. A mathematical model to calculate the carbon film thickness at different locations on the coater plate is established, based on the assumption that carbon atoms evaporate from the carbon tip equally in all directions during the coating process. In order to reduce the differences in the carbon coating thickness, we suggest moving the carbon rod to a higher position, moving the thinner samples to the center and thicker samples to the edge of the coater plate, and using a rotating circular coater plate during coating.