Size Andmorphology Research Articles

Revisiting Early Jurassic Biscutaceae: Similiscutum giganteum sp. nov.

Abstract. A large, broadly elliptical coccolith of the genus Similiscutum (Biscutaceae) was observed in sediments dated from the Lower Jurassic (upper Pliensbachian to Toarcian) coming from different localities of western Tethys, namely Portugal (Lusitanian Basin), France (Causses and Paris basins) and Spain (Subbetic area). This form is quite easy to find in the Toarcian GSSP (Global Stratotype Section and Point) of Peniche (Portugal), where the holotype has been described. More than 100 specimens of Similiscutum were digitally captured using a CCD camera, including this large form and two other related species, Similiscutum finchii and Similiscutum novum. The length and width of the coccoliths and the length and width of their central area were measured, and biometric analyses were performed. Results show that this large morphotype of Similiscutum is well characterized and easily differentiable by its size and morphology from the species S. finchii and S. novum, which are characterized by a similar extinction pattern in optical-microscope crossed polars . On the basis of combined differences in size and in central-area shape and structure, Similiscutum giganteum sp. nov. is introduced here. (Plant Fossil Names Registry no.: PFN003067; Act LSID: urn:lsid:plantfossilnames.org:act:3067).

Cambrian ooids, their genesis and relationship to sea-level rise and fall: A case study of the Qingshuihe section, Inner Mongolia, China

ABSTRACT: TheCambrian strata at the northwestern margin of the North China Platform in InnerMongolia hold thick oolitic-grain bank deposits.Generally, the strata are dominated by calcareous mudstone of shelf facies in the lower part, micritic limestone consisting of deep to middle ramp facies in the middle part, and oolitic limestone encompassing shallow ramp to grain bank facies in the upper part of each formation. The shelf and deep ramp facies are the result of relative sea-level rise, while oolitic limestones developed in response to relative sea-level fall. Microscopically, the studied ooids are represented by radial crystal structures and concentric laminations with or without cores, single crystal or neomorphosed ooids, and highly bored ooids. The size andmorphology of the ooids indicate a two-fold mechanical influence of microbes; constructive in the Miaolingian and destructive in the Furongian ooids. Based on these observations, it can be inferred that microbes (predominantly composed of filamentous fossils of cyanobacteria) excreted extracellular polymeric substances (EPS) to develop multiple bacterial biofilms microbial mats. The subsequent decay of the EPS through sulfate reducing bacteria most likely caused precipitation around these ooids. The depositional style of ooids occupying the upper parts of the formations, and their possible genesis from microbes provide clue for regional correlation, as well as affirm biological control in the formation of ooids.

Lidocaine-Loaded Solid Lipid Microparticles (SLMPs) Produced from Gas-Saturated Solutions for Wound Applications.

The delivery of bioactive agents using active wound dressings for the management of pain and infections offers improved performances in the treatment of wound complications. In this work, solid lipid microparticles (SLMPs) loaded with lidocaine hydrochloride (LID) were processed and the formulation was evaluated regarding its ability to deliver the drug at the wound site and through the skin barrier. The SLMPs of glyceryl monostearate (GMS) were prepared with different LID contents (0, 1, 2, 4, and 10 wt.%) using the solvent-free and one-step PGSS (Particles from Gas-Saturated Solutions) technique. PGSS exploits the use of supercritical CO2 (scCO2) as a plasticizer for lipids and as pressurizing agent for the atomization of particles. The SLMPs were characterized in terms of shape, size, and morphology (SEM), physicochemical properties (ATR-IR, XRD), and drug content and release behavior. An in vitro test for the evaluation of the influence of the wound environment on the LID release rate from SLMPs was studied using different bioengineered human skin substitutes obtained by 3D-bioprinting. Finally, the antimicrobial activity of the SLMPs was evaluated against three relevant bacteria in wound infections (Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa). SLMPs processed with 10 wt.% of LID showed a remarkable performance to provide effective doses for pain relief and preventive infection effects.

Influence of Co ion doping on the microstructure, magnetic and dielectric properties of Ni1-xCoxFe2O4 ceramics

Ni1-xCoxFe2O4 (x = 0, 0.2, 0.4, 0.6, 0.8) ceramics were prepared by chemical co-precipitation method and the effect of Co ion doping on the microstructure, magnetic and dielectric properties has been investigated. The results show that the synthesized ceramics display only spinel phase of Ni1-xCoxFe2O4, without other apparent impurities found. The lattice of Ni1-xCoxFe2O4 crystal structure was distorted as a result of the incorporation of Co ion, and the lattice parameters increase with the increase of Co ion content. The grain size decreases slightly with increasing the content of Co ion, indicating a change of particle size and morphology at higher doping content. The results of impedance analysis shows that the sample doped with 80 at.%Co possesses the maximal dielectric constant, while the pure NiFe2O4 sample shows the minimal value when the frequency is below 0.1MHz. The M-H loops of these ceramics exhibit highly magnetic nature and the saturation magnetization. The remnant magnetization increases linearly with the increase of Co-concentration in nickel ferrite while the coercive field (Hc) shows non-monotonic variation with Co content. The minimal and maximal values of Hc can be obtained when the Co concentrations are 40 and 80 at.%, respectively. The highest value of the saturation magnetization is 63 emu/g obtained with 80 at.% Co doping while the lowest value is ~31 emu/g for the pure NiFe2O4 ceramics. The abnormal magnetic behaviour is due to the A-B super exchange interaction when magnetic Co2+ ions are added.

Facile biosynthesis, characterization, and solar assisted photocatalytic effect of ZnO nanoparticles mediated by leaves of L. speciosa

Synthesis of metal oxide nanoparticles using novel methodologies always attracts great importance in research. The use of plant extract to synthesize nano-particle has been considered as one of the eco-friendly methods. This paper describes the biosynthetic route of preparation of zinc oxide nanoparticles (ZnO NPs) from the Lagerstroemia speciosa leaf extract. This approach appears to be low-cost preparation and alternative method to conventional methods. Highly stable and hexagonal phase ZnO NPs with average particle size of 40nm were synthesized and characterized by UV–Vis absorption spectroscopy (surface Plasmon resonance), Fourier transform infrared spectroscopy (surface functionalities), X-ray Diffraction analysis (crystallinity), TEM and SEM (size and morphology), Energy Dispersive X-ray spectroscopy (elemental composition), Thermogravimetric analysis (weight loss) and Zeta potential (stability). The preliminary phytochemical experiments identify the possible chemical groups present in leaves extract. The photocatalytic properties of ZnO NPs were studied using UV–Vis spectroscopy by exposing methyl orange to sunlight and it is found to be degraded up to 93.5% within 2h. The COD values were significantly reduced from 5600mg/L to 374mg/L after 100min of solar radiation. The hemolytic activity of synthesized zinc oxide nanoparticles was performed on human erythrocyte cells. Thus the present study provides a simple and eco-friendly method for the preparation of multifunctional property of ZnO NPs utilizing the biosynthetic route.

Impedance spectroscopy of nanocrystalline MgFe2O4 and MnFe2O4 ferrite ceramics: Effect of grain boundaries on the electrical properties

Two ferrite ceramic materials, MgFe2O4 and MnFe2O4, were successfully fabricated by a conventional sintering of nanosized powders (at 1373 K for 2 h) synthesized by soft mechanochemical route. The particle size and morphology of powders were studied using X-ray diffraction (XRD) and transmission electron microscopy (TEM). XRD analysis was carried out for the determination of phase purity, crystal structure and average crystallite size of sintered ferrites. Both mechanosynthesized ferrite samples show mean crystallite sizes in the nm-range. Over the frequency range of 100 Hz to 1 MHz, impedance spectra of prepared ferrite ceramics are investigated at and above room temperature. Changes in the impedance plane plots with temperature have been discussed and correlated to the microstructure of materials. An equivalent circuit model is applied to explore the electrical parameters (resistance and capacitance) associated with grains and grain boundaries. Complex impedance analysis indicates the dominance of grain boundary effects which control the overall electrical behaviour of studied ferrites. The decrease in grain boundary resistance with temperature suggests a thermally activated conduction mechanism.

Potential Implementation of Electronic Waste Based Magnetite Powder for Magnetorheological Elastomers

This paper focuses on the preliminary characterization of alternative magnetic particles as a replacement for commercial carbonyl iron particles for magnetorheological elastomers (MREs). Magnetite powder (Fe3O4) can be found in electronic waste (E-waste), iron ore as well as toner waste. In this study, three types of powders namely electronic waste based ferrite powder, iron sand, and toner waste are characterized according to their size and morphology (SEM), chemical elements (EDAX), chemical compound (XRD) and magnetic properties (VSM). The results are used as considerations to choose the most suitable powders that could replace carbonyl iron. The average size of all powders types is about 1 to 50 microns and having irregular shapes. The highest content of magnetite (Fe3O4) compound is found in electronic waste based ferrite powders by referring to magnetite patterns (reference code: JCPDS 01-088-0315). Electronic waste based ferrite powder has the highest magnetic moments saturation of 92.9 emu/g compared the counterparts. Finally, electronic waste based ferrite powder appears to be the most potential materials for replacing the carbonyl iron.

Forensic Dentistry as a Morphological Exercise in the Medico-legal Investigation of Death

INTRODUCTIONIn one of the first scenes of the American thriller film“The Silence of the Lambs”, young FBI agent ClariceStarling is assigned to investigate the body of Buffalo Bill’srecently discovered victim. When Starling helps perform theautopsy, she manages to identify and extract the chrysalis ofa death’s-head Hawkmoth (Acherontia atropos) from thevictim’s mouth. Eventually, this finding was an importantpiece of evidence which lead to the capture of the serialkiller. Less cinematographically, Wankhede (2000) reportsfour factual cases with the aim to underline that examinationof the oral cavity, trachea, hands and all injuries is a vitalpart of post-mortem investigation. In the first one, a case ofhanging, the suicide note was found in the oral cavity.In forensics, the nature of collected evidence makesanalysis in many disciplines complex. Each type of traceevidence requires a unique systematic approach, and eventhese approaches are significantly based on the size andmorphology of the evidence being examined. Sincemorphology is the part of the biology that studies the formof organic beings and the modifications or transformationsthat it experiments, thanatology (the study of death and itsmechanisms), and forensic pathology (the morphology ofthe cadaveric injuries), they justify the morphologicalperspective of the medico-legal analysis. Forensic pathologyis essentially a visual exercise (El-Nageh et al., 1999).Although the forensic dentistry is a well-recognizeddiscipline, the term “Forensic Oral Pathology” is used todefine the field of odontology that involves the“identification, documentation, recovery and preservationof all signs in soft and hard oral tissues to making availablethe legal evidence”. This approach is more integral andcomprehensive than the recognized but unjustly delimitated,

<i>In vitro</i> and <i>In vivo</i> Characterisation of Piroxicam-Loaded Dika Wax Lipospheres

Purpose: To formulate piroxicam-loaded lipospheres and evaluate their in vitro and in vivo properties.Method: Piroxicam-loaded lipospheres were prepared by hot homogenization technique using dika wax and Phospholipon® 90G (1:1, 1:2 and 2:1) as the lipid matrix. Characterisation, based on particle sizeand morphology, pH, drug content and encapsulation efficiency, were carried out on the lipospheres. In vitro release was evaluated in simulated intestinal fluid (pH 7.5). Anti-inflammatory and ulcerogenic properties of the piroxicam-loaded lipospheres were studied using healthy, adult Wistar rats.Result: Photomicrographs revealed spherical particles in the range of 1.66 – 3.56 ìm. The results also indicated that lipospheres formulated with lipid matrix 1:1 and containing 0.25 % piroxicam had the highest encapsulation efficiency of 84 %. In vitro release data showed that lipospheres formulated with lipid matrix having higher concentration of dika wax exhibited the fastest drug release of drug with maximum release time between 60 - 70 min. The lipospheres exhibited good anti-inflammatoryproperties with 58.6 % oedema inhibition at 5 h. Piroxicam-loaded liposheres had an ulcer index of zero while, the reference (plain piroxicam) had an ulcer index of 15.00 ± 1.23 (p < 0.05).Conclusion: Piroxicam lipospheres formulated with a mixture of dika wax and phospholipid exhibited good in vitro and in vivo properties.Keywords: Dika wax, Lipospheres, Piroxicam, Phospholipid, Ulcerogenicity, Anti-inflammatory

Enhanced sulfur resistance of bifunctional Pd/HZSM-5 catalyst comprising hierarchical carbon-templated zeolite

A bifunctional hierarchical micro-mesoporous Pd/HZSM-5-BP catalyst (2 wt% Pd) has been prepared by impregnating an HZSM-5 sample hydrothermally synthesized in the presence of nearly uniform carbon nanoparticles (Black Pearls 2000) of ca. 12 nm in size in order to generate intracrystalline mesovoids (mostly in the 10–20 nm range, as ascertained by TEM). An equivalent catalyst (Pd/HZSM-5-ref) comprising an HZSM-5 zeolite having roughly the same Si/Al ratio (26, from ICP-OES), crystallite size and morphology (SEM), and acidity (FTIR-pyridine and NH 3-TPD) but synthesized in the absence of carbon has also been prepared for comparison purposes. TEM, CO chemisorption and XPS results on reduced catalysts (400 °C in H 2 flow) revealed that Pd 0 is better dispersed in the catalyst involving the hierarchical carbon-templated zeolite, for which a large fraction of metal nanoparticles was found to be confined within the intracrystalline mesocavities (TEM). Despite the differences in dispersion, both bifunctional catalysts were found to be well balanced in terms of metal/acid ratio and consequently equally active and selective for the hydroconversion of n-octane (which is able to easily access all the acid sites in the 10-ring channels of ZSM-5) in the absence of sulfur. However, after addition of 100 ppm sulfur to the n-octane feed, the hierarchical Pd/HZSM-5-BP catalyst displayed a superior thioresistance leading to a notably higher steady conversion (48% as compared to 21% attained on Pd/HZSM-5-ref). The higher sulfur resistance of the hierarchical catalyst is ascribed to the inhibition of the sulfur-induced migration and sintering of Pd 0 nanoparticles on the external zeolite surface when confined within the mesovoids, as revealed by TEM after catalysis.

The synthesis and characterization of platinum nanoparticles: a method of controlling thesize and morphology

In this paper, Pt nanoparticles with good shapes of nanocubes and nano-octahedraand well-controlled sizes in the range 5–7 and 8–12 nm, respectively, havebeen successfully synthesized. The modified polyol method by adding silvernitrate and varying the molar ratio of the solutions of silver nitrate andH2PtCl6 has been used to produce Pt nanoparticles of the size and shape to be controlled. The sizeand morphology of Pt nanoparticles have been studied by transmission electron microscopy(TEM) and high resolution TEM (HRTEM). The results have shown that their very sharpand good shapes exist in the main forms of cubic, cuboctahedral, octahedral andtetrahedral shapes directly related to the crystal nucleation along various directions of the{100} cubic,{111} octahedraland {111} tetrahedral facets during synthesis. In particular, various irregular and new shapes of Ptnanoparticles have been found. Here, it is concluded that the role of silver ions has to be consideredas an important factor for promoting and controlling the development of Pt nanoparticles of{100} cubic,{111} octahedraland {111} tetrahedral facets, and also directly orienting the growth and formation of Ptnanoparticles.

Controlled synthesis of dendritic Au@Pt core–shell nanomaterials for use as an effectivefuel cell electrocatalyst

We report the controlled synthesis of dendritic Au@Pt core–shell nanomaterials. The sizeand morphology of the Au cores and the Pt shell thickness of the Au@Pt core–shellnanostructures could be easily tuned. It was found that the directing agent and thereducing agent play critical roles in the synthesis of dendritic Au@Pt core–shellnanomaterials. For comparison purposes, conventional Au@Pt core–shell nanoparticles andmonometallic Pt nanoparticles were also synthesized by the successive reduction method.Transmission electron microscopy (TEM) observations demonstrated the dendritic surfaceof the products obtained. The UV–visible (UV–vis) spectroscopy results and a comparisonof the average diameter between the dendritic Au@Pt and conventional Au@Ptconfirmed the relatively loose Pt shells around Au cores for the dendritic Au@Pt. Theas-prepared dendritic Au@Pt showed enhanced electrocatalytic activity for methanoloxidation in acid medium, compared to the conventional Au@Pt and monometallicPt.

Synthesis, Preparation and Catalytic Activities of V-Doped TiO<sub>2</sub> Gel Coating on Porous α-Al<sub>2</sub>O<sub>3</sub> Beads

TiO2 and V-doped TiO2 gel were synthesized and coated onto porous α-Al2O3 beads to study the thermal catalytic activities of oxidation reactions. Titanium isopropoxide (Ti(OPr)4) and 1,2-butadiol(Bu(OH)2) were used as starting chemicals for preparation of TiO2 gel without Vdoping. After aging at ambient temperature for one week, a TiO2 gel was obtained. The concentration of Ti(OPr)4 was varied, 0.2, 0.3, 0.7 and 2.4 M was used. For V-doping of the TiO2 gel, 0.05, 0.20 and 0.75 mole% of V was prepared by ultrasonically dissolving vanadium acetylacetone (V(acac)2) in 1,2-butadiol. The solutions were then added to Ti(OPr)4. Finally, the mixed solutions were kept under ambient temperature for one week to form the V-doped TiO2 gel. TiO2 and V-doped TiO2 were calcined at 300, 400, 500, 600, 700, and 800 °C. XRD analysis, SEM and TEM in conjunction with EDS analysis were used to identify the phases present, grain size and morphology. The TiO2 grains have a particle size in the nano-scale range. Doping TiO2 with V could retard growth of the TiO2 particles and affect phase transformation at higher calcination temperatures. Both the TiO2 and V-doped TiO2 gels were prepared and coated onto α-Al2O3 beads to test oxidation reactions in a purpose-designed reactor. The results of the catalytic reactions indicated that V-doped TiO2 had a higher oxidation activity than the undoped TiO2 gel. The content of vanadium was related to the reaction efficiency.

Microstructure Analysis and Characterization of Li(Ni<sub>1-x</sub>Co<sub>x</sub>)O<sub>2</sub> Thin Film Prepared by Li Diffusion on Ni-Co Alloy Substrates for Cathode Application

The currently commercialized cathode material for Li ion batteries such as LiCoO2 exhibited limit to further improve the performance of the batteries, since the employed screen printing method for cathode fabrication is difficult to reduce the thickness and control the microstructure of the oxide layer. In this studies, we have synthesized Li(Ni1-xCox)O2 thin film by utilizing Li-diffusion reaction on the surface of Ni-Co alloy substrates. For the preparation of Ni-Co alloy rod, Ni and 20at.%Co powder were mixed for 24hrs by ball milling, and then pressed into rod-shape by cold-isostatic pressing. The Ni-Co rods were sintered at 1100°C for 6hrs in the reducing atmosphere of Ar 96% and H2 4%. The sintered Ni-20at%Co rod was cold-rolled into tape at 5% reduction ratio with the final thickness of 100㎛, and the recrystallization heat treatment for the development of the cube texture of the rolled Ni alloy tape was carried out at 1000°C in Ar 96% and H2 4%. After thin layer of metallic Li was deposited on the surface of Ni-Co template using thermal evaporation method in the glove box, the Li/Ni-Co composite tape were heat-treated at 700~850°C for 1~2hrs in oxidizing atmosphere to induce Li-diffusion into Ni-Co substrate and Li(Ni0.8Co0.2)O2 phase formation. The phase evolution of Li(Ni0.8Co0.2)O2 was confirmed by X-ray diffraction and the grain size and morphology of the surface were analyzed by scanning electron microscopy and atomic force microscopy. Also the charge and discharge test were conducted to confirm the electrical characteristics of Li(Ni1-xCox)O2/Ni-Co thin film for the cathode application.

The Microstructural Evolution of Mn<sub>3</sub>O<sub>4</sub> Hausmannite during Autoxidation

Mn3O4 hausmannite, which is a normal spinel with the Mn2+ in the tetrahedral site and the Mn3+ in the tetrahedral site, is one of the most stable manganese oxides. Variation in the valence of Mn ions (2+, 3+ and 4+) contributes to several different structures of manganese oxides. The autoxidation of precipitated manganese hydroxide in an alkaline solution is a practical approach to synthesize hausmannite (Mn3O4) at low temperature. During the process, the particle size and morphology of derived products were totally different from the precursors even though nanometer-sized Mn(OH)2 crystals were fabricated at first. It was observed that the variation was resulted from the accumulation of produced Mn3O4 crystallites which departed from the original crystals. This study has not only discussed the influence of reactant concentrations on the particle size and morphology of derived powders, but also revealed the morphological transformation of crystals involved in autoxidation with the aid of electron micrographs

Preparation of oridonin-loaded solid lipid nanoparticles and studies on them in vitro and invivo

Oridonin, a lipophilic Chinese medicine, has very low oral bioavailability dueto its poor solubility. Solid lipid nanoparticle (SLN) delivery systems oforidonin have been formed using stearic acid, soybean lecithin and pluronicF68 in our studies to overcome this problem. Emulsion evaporation–solidification atlow temperature was used to prepare SLN dispersions. The particle size andmorphology were examined by transmission electron microscopy (TEM), andthe zeta potential was measured by a television micro-electrophoresis apparatus.Process and formulation variables have been studied and optimized on the basisof entrapment efficiency. Differential scanning calorimetry (DSC) and powderx-ray diffraction (PXRD) studies were performed to characterize the state ofthe drug. In vitro release studies were performed in phosphate-buffer solution(PBS) (pH 7.4). The tissue distribution in mice and the pharmacokinetics inrabbits were studied to evaluate the tissue targeted property of SLNs. Stable SLNformulations of oridonin having a mean size range of 15–35 nm and mean zeta potential−45.07 mV were developed. More than 40% oridonin was entrapped in SLNs. DSC and PXRDanalysis showed that oridonin is dispersed in SLNs in an amorphous state. The releasepattern of the drug was analysed and found to follow the Higuchi equations. In vivo studiesdemonstrated that oridonin-loaded SLNs obviously increased the concentration of oridoninin liver, lung and spleen, while its distribution in heart and kidney decreased.

Bis(ethylenedithio)tetrathiafulvalene Charge‐Transfer Salt Nanotube Arrays

The basic structure of BEDT-TTF-based saltcrystals is composed of two alternating layers: a BEDT-TTFcation layer and an anion layer. The anions can be varied interms of size, charge, and structure, giving rise to the proper-ties mentioned above. However, most of these physical prop-erties were investigated on macroscopic single-crystallinesamples to explore the anisotropic characteristics of the prop-erties. To advance these materials for potential applications,such as interfacial materials for organic molecules and inor-ganic substrates, or to probe the size effect on the supercon-ductivity of these materials, quasi-1D BEDT-TTF-based sys-tems, including nanotubes and nanowires, with controlled sizeand morphology are important. To our best knowledge, therehave been no reports in the literature on the fabrication ofBEDT-TTF-based charge-transfer salt nanotubes. In addition,although the electrical characteristics of single crystals andfilms of BEDT-TTF-based charge-transfer salts have beenwell studied

Design of Sb2S3 nanorod-bundles: imperfect oriented attachment

The large scale formation of uniformSb2S3 nanorod-bundles has been achieved via a simple and mild hydrothermal approach with theassistance of polyvinylpyrrolidone. By closely inspecting the growth process and thecrystallographic analysis of as-synthesized products, conclusive evidence has been providedto show that the growth mechanism of such nanorod-bundles is imperfect orientedattachment. The anisotropic adsorption of polyvinylpyrrolidone at the different surfaces ofSb2S3 nanocrystals assists the one-dimensional preferential growth; it is just the misorientationsthat result in the nanorod-based superstructures. Moreover, the hydrothermal treatmenttime plays a crucial role, and can be used as the parameter to control the size andmorphology of the bundles. This simple approach promises future large-scale controlledsynthesis of various nanobody-based superstructures for many important applications innanotechnology.

Morphology observation of carbon deposition byCH4 decomposition over Ni-based catalysts

We found a novel morphology variation of carbon deposition derived fromCH4 decomposition over Ni-based catalysts. By altering the chemical composition and particle size ofNi-based catalysts, carbon filaments, nanofibres and nanotubes were observed over conventionalNi /γ-Al2O3,Ni–Co /γ-Al2O3 andnanoscale Ni–Co /γ-Al2O3 catalysts, respectively. The simple introduction of Co into a conventionalNi /γ-Al2O3 catalyst can vary the carbon deposition from amorphous filamentous carbon to ordered carbon fibres.Moreover, carbon nanotubes with uniform diameter distribution can be obtained over nanosizedNi–Co /γ-Al2O3 catalyst particles. In addition, the oxidation behaviour of the differentdeposited carbon was studied by using a temperature-programmed oxidationtechnique. This work provides a simple strategy to control over the sizeand morphology of the carbon deposition from catalytic decomposition ofCH4.

Field enhanced fabricationof metallic nanostructures using millisecond-pulsed scanningtunnelling microscopy

Scanning tunnelling microscopy (STM) can be used as aneffective tool for the manipulation of atoms on surfaces.However, it is a laborious procedure, often taking severalhours to construct even the simplest patterns. To address thisconstraint, we have investigated the use of distinct tip geometries combined with voltage pulsing in an STM as a methodof rapid nanostructure fabrication. A computationalfinite-element based electrostatic model enables those tipgeometries which can lead to a particular geometrical patternto be identified. The predictions in the case of a truncatedcircular cone are confirmed by experimental observation using voltage-pulsed STM. Constructs comparable both in size andmorphology to quantum corral type structures were constructedwith assembly times in the millisecond regime. The mechanism offormation is discussed.