Gold Tip Research Articles

Visible light enhanced selective benzene response of hexagonal atomic structured CuS microcloves

We have reported CuS microcloves (MCs) for highly selective detection of benzene using scanning kelvin probe (SKP) technique. The electron microscopy investigations revealed the formation of clove shaped CuS with a size of about 1–2 µm at 180 °C and 6 h. The time of reaction significantly affected the crystallinity as well as the morphology of resulting CuS materials. The investigations on adsorption behavior of different types of common volatile organic compounds (VOCs) with varying charge and nature revealed an outstanding selectivity towards benzene when compared to other VOCs. The difference in work function between gold tip and sensor surface modified with CuS MCs was decreased under the exposure of light, most likely caused by transfer of electrons to conduction band of CuS under illumination of light. As a result, the CuS MCs showed enhanced photo response in visible light exposure in the presence of benzene. A chemiresistive type sensor device was fabricated using CuS MCs and exposed to benzene vapor in a concentration ranging from 2.8 to 11.2 ppm. The sensitivity was found to be 1.63 × 10-3 ppm−1. Notably, a rapid response time of ∼6 s and recovery time of ∼ 16 s was achieved for the sensor at a benzene concentration of 5.6 ppm at room temperature. Also, considerable and repeatable sensor response was observed for 560 ppb of benzene vapor at 70 °C. Hence, these results suggested that the CuS MCs have huge potential as novel material for selective benzene detection in gas phase towards breath analysis and other environmental monitoring.

A Gold Needle Tip Array Ultrafast Electron Source with High Beam Quality.

Electron sources are crucial elements in diverse applications such as electron microscopes, synchrotrons, and free-electron lasers. Nanometer-sharp needle tips are electron emitters with the highest beam quality, yet for a single needle the current is limited. Combining the emission of multiple needles promises large current yields while preserving the individual emitters' favorable properties. We present an ultrafast electron source consisting of a lithographically fabricated array of sharp gold tips illuminated with 25 fs laser pulses. The source provides up to 2000 electrons per pulse for moderate laser peak intensities of 1011 W/cm2 and a narrow energy width of 0.5 ± 0.05 eV at low current. The electron beam has a well-behaved Gaussian profile and is highly collimated, yielding a small normalized emittance on the order of nm·rad. These properties are well suited for applications requiring both high current and spatial resolution, such as free-electron light sources and chip-based particle accelerators.

NOVEL APPROACH FOR ONE-POT SELF-ASSEMBLED MONOLAYER PREPARATION OF GOLD TIPPED CdSe/CdS NANORODS

In this study, CdSe/CdS nanorods (NRs) were synthesized via hot injection method to perform simultaneous self-assembly studies with gold tip formation on the nanorods. In this new approach, we propose and demonstrate reductant chemical and gold organosol-free synthesis of gold-tipped nanocrystals on the subphase. Instead of gold organosol usage, gold precursor was prepared by addition of gold source into subphase, and photocatalytic reduction of gold on the tip of nanorods was achieved by exciting the samples under UV-light excitation. Reduction of gold nanoparticles on the tip of NRs was also tried by heating effect, which results in nanopillar formation. The optical properties of these nanorods were determined by spectrophotometric measurements, and gold-tipped nanorods were imaged by TEM analysis. This method enables self-assembly of nanorods and following gold tip formation on the subphase, and it can pave the way to prepare well-defined metal-tipped oriented surfaces that can be used for optical and photocatalysis applications.

Corrugated Gold Tip as Optical Tweezers to Apply Force on Zinc Sulphide Quantum Dot Nanoparticle

Corrugated Gold Tip as Optical Tweezers to Apply Force on Zinc Sulphide Quantum Dot Nanoparticle

Squeezed Protons and Infrared Plasmonic Resonance Energy Transfer.

Unusual nuclear quantum effects may emerge near noble metal nanostructures such as squeezed vibrational states in molecular junctions and plasmonic resonance energy transfer in the infrared domain. Herein, nuclear quantum effects near heavy metals are studied by nuclear-electronic orbital density functional theory (NEO-DFT) with an effective core potential. For a quantum proton sandwiched between a pair of gold tips modeled by two Au6 clusters, NEO-DFT calculations suggest that the quantum proton density can be squeezed as the tip distance decreases. For an HF molecule placed near a one-dimensional Au nanowire composed of up to 34 Au atoms, real-time NEO time-dependent density functional theory (RT-NEO-TDDFT) shows that the infrared plasmonic motion within the Au nanowire may resonantly transfer electronic energy to the HF proton vibrational stretch mode. Overall, these calculations illustrate the advantages of the NEO approach for probing nuclear quantum effects, such as squeezed proton vibrational states and infrared plasmonic resonance energy transfer.

Histological artifacts associated with laser and electroscalpel gingivectomy: Case series

Introduction. Over time, efforts have been invested in the design of new instruments that overcome the disadvantages of the gold standard instrument in surgery, the scalpel. As a result, electronic equipment has emerged such as the electric scalpel and laser devices. The available evidence on these instruments suggests that the tissue response is related to each instrument’s physical and biological cutting principles. Objective. To compare the histological changes in gingiva samples associated with surgical cutting performed with a 940 nm diode laser, a 2780 nm erbium, chromium: yttriumscandium-gallium-garnet (Er,Cr:YSGG) laser, and an electric scalpel, by presenting a series of cases. Case presentation. We present three cases of healthy patients undergoing cosmetic surgery. The clinical examination revealed exposure of a keratinized gingiva band greater than 4 mm, normal color and texture in gingival tissue, with a firm consistency and no bleeding on periodontal probing. Gingivectomy was indicated with the following protocols: Diode laser of 940 nm at 1 W, in continuous mode; Er,Cr:YSGG laser of 2780 nm at 2.5 W, 75 Hz, H mode, air 20, water 40, gold tip MT4); and electric scalpel in cutting mode at power level four. Gingival tissue samples were taken and stored in 10% formaldehyde for histological analysis. Conclusion. All the evaluated cutting instruments generated histological changes produced by the thermal effect, the main ones being collagen coagulation and carbonization. The depth of thermal damage caused by the 2780 nm Er,Cr:YSGG laser was much lesser than that induced by the electric scalpel and the 940 nm diode laser.

Electrodeposition of Multi-Segment Nanowires and Site-Selective Solder Deposition for Magnetic Assembly and Nanoscale Joining

Electronic device packaging involves complex wiring assemblies for transport of electrical and thermal energy, enabling increasingly sophisticated circuit designs in an industry favoring aggressive device miniaturization. Nanoscale miniaturization of the wire morphology has become increasingly sophisticated in recent years with regards to synthesis; however, the ability to arrange and manufacture these small-scale materials to fully exploit their novel properties has been quickly outpaced. The purpose of this investigation is the establishment of a synthesis technique for a core/shell nanowire structure with tunable compositional templating via electrodeposition which can pass through this bottleneck via directed matrix assembly. A gold-nickel-gold nanowire structure was utilized as the core, synthesized via electrochemical deposition into an anodic aluminum oxide (AAO) template; the nickel segment was chosen to act as a magnetic vehicle for directed assembly, while the bordering gold tips were coated with a solder shell. Gold-selective deposition of this tin solder shell was achieved by establishing a chemisorbed nickel-protective monolayer via immersion in azelaic acid solution. Next, the protected nanowires were dispersed in an aqueous reaction vessel with excess sodium borohydride reducing agent. Controlled addition of tin sulfate and sodium dodecyl sulfate solution to the vessel resulted in the formation of tin seeds which deposited along the gold tips of the nanowires, growing into a “dumbbell” shape nanowire with tin deposited on both gold tips. Composition and confirmation of the solder deposition was performed with scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopic (EDS) analysis. Crystal structure of the core/shell nanowires was performed with x-ray diffraction (XRD) to identify intermetallic formation between the tin and gold. The core/shell nanowires were arranged magnetically across a conductive interdigitated electrode and melted by an infrared-driven reflow procedure under flux atmosphere, establishing ohmic contact tip-to-tip between nanowires and in wire-to-pad morphologies. This work establishes an effective and scalable method for site-specific nanowire functionalization while simultaneously addressing miniaturization-associated assembly issues in its desired applications.

Fabrication of pyramid-shaped gold tip for adiabatic nanofocusing of surface plasmon polaritons

Scattering-type scanning near-field optical microscopy based on adiabatic nanofocusing of surface plasmon polaritons (SPPs) is a powerful technique that can achieve free-background nanoscale optical resolution of material. However, the performance of the propagated confined modes strongly depends on the characteristic structure of the probe. Although the metallic pyramid structure provides excellent tightly confined modes, however, it is challenging to realize the required pyramid geometry. Here, we propose a simple method for fabricating a reproducible and controllable gold pyramid-shaped tip. The produced pyramid-shaped tips were made by electrochemical etching and by applying a pulse wave to the system. From a systematic study, we found that the key factor of fabrication of desired tip geometry is based on the platinum (Pt) wire shapes. Traditional circular-shaped platinum ring electrodes are used for gold tip fabrication in an electrochemical etching. In our method, we bent the Pt wire into a triangular shape as the electrode for the etching process. The influence of the geometrical ring shapes on the fabrication of the Au tip structure is investigated. The gold tip structure was optimized by controlling the Pt ring shape, and the desired pyramid-shaped gold tip was achieved with a yield of 70%. The obtained etched pyramid-shaped tips were then mounted along the side of one of the arms of a quartz tuning fork force sensor to test their performance for shear-force topographical image and for guiding SPPs along the pyramid wedge based on adiabatic nanofocusing microscopy. The result shows topographical images of indium tin oxide with a spatial resolution smaller than 20 nm. Furthermore, we experimentally demonstrate the generation of the SPPs that propagated adiabatically along the wedge of an appropriate fabricated pyramid-shaped tip toward a nanometer-size spot at the tip apex. The demonstration of this method strongly suggests that the obtained pyramid-shaped tip will enable new experiments probing the dynamics of optical excitations of individual metallic, semiconducting, and magnetic nanostructures.

3D microelectrode arrays, pushing the bounds of sensitivity toward a generic platform for point-of-care diagnostics

The increased sensitivity of microelectrode arrays (MEAs) over macroelectrodes for biosensing is well established, and results from reducing the diffusion gradient of the target species to and from the electrode surfaces. The current study describes the fabrication and characterisation of a polymer-based MEA, which exploits the advantages of three dimensionality (3D). Firstly, the unique 3D formfactor promotes release of the gold tips from an inert layer in a controlled fashion, to form a highly reproducible array of microelectrodes in a single step. The 3D topography of the fabricated MEAs significantly enhances the diffusion profile of the target species to the electrode which results in higher sensitivity. Furthermore, the “sharpness” of the 3D structure induces differential current distribution that is focused at the apices of the individual electrodes, reducing the active area, and thereby overcoming the requirement for the electrodes to be sub-micron in size before true MEA behaviour can be achieved. The electrochemical characteristics of the 3D MEAs shows ideal micro-electrode behaviour, with a level of sensitivity of three orders of magnitude greater than that of enzyme-linked immunosorbent assays (ELISA), as the optical based gold standard. The application of the 3D MEAs uses the combination of enzyme-label and substrate approach employed in ELISAs as a generic basis for biosensing and can hence be applied to the plethora of targets that utilise the ELISA approach. As an example, the 3D MEAs are applied to the detection of RNA and demonstrate a level of detection down to single digit picomolar concentrations.

Photomagnetically Powered Spiky Nanomachines with Thermal Control of Viscosity for Enhanced Cancer Mechanotherapy.

Nanomachines with active propulsion have emerged as an intelligent platform for targeted cancer therapy. Achieving an efficient locomotion performance using an external energy conversion is a key requirement in the design of nanomachines. In this study, inspired by diverse spiky structures in nature, a photomagnetically powered nanomachine (PMN) with a spiky surface and thermally dependent viscosity tunability is proposed to facilitate mechanical motion in lysosomes for cancer mechanotherapy. The hybrid nanomachine is integrated with magnetic nanoparticles as the core and covered with gold nanotips. Physical simulations and experimental results prove that the spiky structure endows nanomachines with an obvious photomagnetic coupling effect in the NIR-II region through the alignment and orienting movement of plasmons on the gold tips. Using a coupling-enhanced magnetic field, PMNs are efficiently assembled into chain-like structures to further elevate energy conversion efficiency. Notably, PMNs with the thermal control of viscosity are efficiently propelled under simultaneously applied dual external energy sources in cell lysosomes. Enhanced mechanical destruction of cancer cells via PMNs is confirmed both in vitro and in vivo under photomagnetic treatment. This study provides a new direction for designing integrated nanomachines with active adaptability to physiological environments for cancer treatment.

First clinical experience of high-power ablation of atrial fibrillation with a novel contact force-sensing gold-tip catheter

BackgroundContact force (CF)-sensing catheters are commonly used in the field of radiofrequency (RF) ablation to treat atrial fibrillation (AF). Increasing ablation power (e.g., 50 W) has been suggested as a method to reduce procedure times whilst creating safe and lasting lesions.MethodsWe report the first clinical evidence of a 50 W point-by-point RF ablation in 25 consecutive patients with symptomatic AF using a novel CF-sensing catheter with a gold tip (AlCath Force, Biotronik). We collected and analyzed procedural and ablation parameters. The safety and efficacy of the catheter were evaluated.ResultsAltogether, 985 RF lesions in 25 patients were created with a mean number of 39.4 ± 16.3 lesions per patient. The total skin-to-skin procedure time was 116.1 ± 35.1 min, and the mean total area dose product was 10.9 ± 5.1 Gy*cm2. The mean RF time per procedure was 13.2 ± 6.6 min. The mean RF time per lesion was 20.2 ± 8.4 s. The mean CF was 15.7 ± 7.6 g. We observed a mean force time integral of 274.7 ± 11.1 gs (range: 53 to 496 gs). Acute procedural success, defined as entrance and exit block in all pulmonary veins, could be obtained in all cases. No procedure- or device-related serious adverse events were observed. No audible steam pops occurred. Optical inspection of the catheter after the procedure showed neither charring nor clotting.ConclusionsWe provide the first evidence for the safety and efficacy of 50 W ablation using the AlCath Force gold-tip catheter. These data must be supported by a larger multi-center study.

Dynamic bonding influenced by the proximity of adatoms to one atom high step edges

Low-temperature scanning tunneling microscopy is used here to study dynamic bonding of gold atoms on surfaces under low coordination conditions. In the experiments, using an atomically-sharp gold tip, a gold adatom is deposited onto a gold surface with atomic precision either on the first hollow site near a step edge, or far away from it. Classical molecular dynamics simulations at 4.2 K and density functional theory calculations serve to elucidate the difference in the bonding behavior between these two different placements, while also providing information on the crystalline classification of the STM tips based on their experimental performance.

Studies of carbohydrate-carbohydrate-interactions by atomic force microscopy employing functionalized 4-acetylthio-butyl glucopyranosides

By Fischer glycosylation both anomers of 4-chlorobutyl gluco-as well as galactopyranosides were obtained and transformed into the corresponding 4-acetylthio-butyl glycopyranosides. Dependent on the precursors two straightforward routes were followed to obtain the appropriate 3-O-sulfated derivatives. Unsubstituted and sulfated glucopyranosides were attached to gold surfaces a gold tips. Their interactions were studied using atomic force microscopy for simulations of intercellular glycoside-based interactions and discussed in-depth.

Plasmonic enhanced fluorescence via 3D printing spiral conical tapered gold tip bound to optical fiber

We build a 3D printing spiral conical tapered gold tip directly on the end face of an optical fiber as an efficient fluorescence enhancement device via the two-photon polymerization direct laser writing technology and magnetron sputtering technique. At an optimized geometry achieved via three-dimensional finite-difference time-domain numerical simulations, the gold tip allows the incident light coming from the optical fiber to efficiently excite the surface-plasmon polariton at the outer surface and trigger bright fluorescence of Rodamine dye molecules. The experimental results show that when the incident green laser light at 532 nm has an intensity of 0.5 µW, the fluorescence enhancement factor by the spiral tapered gold tip bound to fiber is about 38 times greater than the reference sample of the flat-cleaved gold film coated fiber. This 3D nanostructured gold-tip bound optical fiber may provide a promising way to improve detection sensitivity in fluorescence-based sensing platforms.

Parabola-Like Gold Nanobowtie on Sapphire Substrate as Nano-Cavity

Plasmonic metallic nanostructures have attracted much interest for their ability to manipulate light on a subwavelength scale and for their related applications in various fields. In this work, a parabola-like gold nanobowtie (PGNB) on a sapphire substrate was designed as a nano-cavity for confining light waves in a nanoscale gap region. The near-field optical properties of the innovative PGNB structure were studied comprehensively, taking advantage of the time-resolved field calculation based on a finite-difference time-domain algorithm (FDTD). The calculation result showed that the resonance wavelength of the nano-cavity was quite sensitive to the geometry of the PGNB. The values that related to the scattering and absorption properties of the PGNB, such as the scattering cross section, absorption cross section, extinction cross section, scattering ratio, and also the absorption ratio, were strongly dependent on the geometrical parameters which affected the surface area of the nanobowtie. Increased sharpness of the gold tips on the parabola-like nano-wings benefited the concentration of high-density charges with opposite electric properties in the narrow gold tips with limited volume, thus, resulting in a highly enhanced electric field in the nano-cavity under illumination of the light wave. Reduction of the gap size between the two gold nano-tips, namely, the size of the nano-cavity, decreased the distance that the electric potential produced by the highly concentrated charges on the surface of each gold nano-tip had to jump across, therefore, causing a significantly enhanced field in the nano-cavity. Further, alignment of the linearly polarized electric field of the incident light wave with the symmetric axis of the PGNB efficiently enabled the free electrons in the PGNB to concentrate on the surface of the sharp gold tips with a high density, thus, strongly improving the field across the nano-cavity. The research provides a new insight for future design, nanofabrication, and characterization of PGNBs for applications in devices that relate to enhancing photons emission, improving efficiency for energy harvesting, and improving sensitivity for infrared detection.

Comparing Commercial Metal-Coated AFM Tips and Home-Made Bulk Gold Tips for Tip-Enhanced Raman Spectroscopy of Polymer Functionalized Multiwalled Carbon Nanotubes.

Tip-enhanced Raman spectroscopy (TERS) combines the high specificity and sensitivity of plasmon-enhanced Raman spectroscopy with the high spatial resolution of scanning probe microscopy. TERS has gained a lot of attention from many nanoscience fields, since this technique can provide chemical and structural information of surfaces and interfaces with nanometric spatial resolution. Multiwalled carbon nanotubes (MWCNTs) are very versatile nanostructures that can be dispersed in organic solvents or polymeric matrices, giving rise to new nanocomposite materials, showing improved mechanical, electrical and thermal properties. Moreover, MWCNTs can be easily functionalized with polymers in order to be employed as specific chemical sensors. In this context, TERS is strategic, since it can provide useful information on the cooperation of the two components at the nanoscale for the optimization of the macroscopic properties of the hybrid material. Nevertheless, efficient TERS characterization relies on the geometrical features and material composition of the plasmonic tip used. In this work, after comparing the TERS performance of commercial Ag coated nanotips and home-made bulk Au tips on bare MWCNTs, we show how TERS can be exploited for characterizing MWCNTs mixed with conjugated fluorene copolymers, thus contributing to the understanding of the polymer/CNT interaction process at the local scale.

Enhancement of non-contact friction between metal surfaces induced by the electrical double layer

Casimir and electrostatic non-contact friction between two gold plates, and a gold tip and a gold plate, are calculated taking into account the contribution of the electrical double layer. It is shown that in an extreme-near field (d<10nm) the contribution from the electrical double layer leads to the enhancement of non-contact friction by many orders of magnitude in comparison to the result of the conventional theory without this contribution. Casimir and electrostatic friction dominate for short and large separations, respectively. The calculated electrostatic friction is in good agreement with experimental data. The results obtained open the way to detect the Casimir friction using Atomic Force Microscope.

Metaphor in Children's Poetry Composed by Mahmoud Kianoush and Soleiman al-Issa

Mahmoud Kianoush, known as the Father of children's poetry in Iran, is one of the contemporary poets who composes simple and straightforward poems. Kianoush's poetry is the reflection of his thoughts and contemplation on the innate relationship between human and nature. Kianoush is a poet whose mind is abundant with people's issues. Among his works, there are 8 books which are specifically written as poems for children and young adults: The Language of Things, Indian Green Parrot, Gold Tip - Silver Wing, Garden of Stars, World's Children, Seven-Colored Arch, the Sun of our House, and Poem by Poem. Considering literary status, Kianoush's poetry can be considered among the most eminent kinds of poetry. The figures of his poetry include imagery especially simile, metaphor, and personification. Soleiman al-Issa is one of the outstanding Syrian poets whose predominant themes are motherland and ethnic sentiments. He has dedicated a major part of his odes (poems) to children especially to suffering Arab children. In his odes, Soleiman al-Issa uses some types of imagery which are easily understood by children. The variety of nominal, verbal, explicit, and implicit metaphors are especially noticed in his poetry. Also, he uses Personification which creates synesthesia and enlivens his poems. Focusing on metaphors, the present study aims to analyze and investigate children's poetry composed by the two Persian and Arab poets, Mahmoud Kianoush and Soleiman al-Issa.

B-PO04-016 A NOVEL IRRIGATED GOLD-TIP FORCE SENSING ABLATION SYSTEM DEMONSTRATES CREATION OF SAFE AND EFFECTIVE HIGH-POWER RF LESIONS IN PRE-CLINICAL TESTING

A novel irrigated, ablation catheter with a beveled, gold tip and 3-D optical force sensor has been developed. Gold provides more uniform heating, while beveling enhances stability at the tissue interface. Irrigation ports (12) are strategically placed to maximize catheter tip cooling. Evaluate the safety of the irrigated AcQBlate Force Sensing System (Acutus Medical, Carlsbad, CA) in an acute and chronic animal study. In anesthetized swine (n=6) a GLP study of ablation in the left and right atrium was performed using a high-power short duration (HPSD) protocol (30W - 50W). Acute effectiveness was determined by EGM attenuation, impedance change, and evidence of functional block (FB). Acute animals were euthanized post-ablation (n=2), and chronic animals were survived for 30 days (n=4). All animals underwent histopathologic assessment at terminal study. Charge density activation mapping (AcQMap) was performed pre- and post-ablation and prior to chronic animal termination. The mean number of ablations/animal was 42.2 ± 7.7 and effective lesions were demonstrated in all animals. Evidence of FB was demonstrated in 100% of contact and non-contact maps. Histology verified transmural lesions in each animal. All safety endpoints were met. There was no evidence of systemic emboli, steam pops or major complications related to RF energy delivery. Cardiac perforation occurred in 1 acute animal not related to RF energy delivery. The AcQBlate Force Sensing System created safe and effective lesions at HPSD in the animal model. Future research should focus on the impact of gold as a thermal conductor in RF ablation.

Chirality Nanosensor with Direct Electric Readout by Coupling of Nanofloret Localized Plasmons with Electronic Transport.

The detection of enantiopurity for small sample quantities is crucial, particularly in the pharmaceutical industry; however, existing methodologies rely on specific chiral recognition elements, or complex optical systems, limiting its utility. A nanoscale chirality sensor, for continuously monitoring molecular chirality using an electric circuit readout, is presented. This device design represents an alternative real-time scalable approach for chiral recognition of small quantity samples (less than 103 adsorbed molecules). The active device component relies on a gold nanofloret hybrid structure, i.e., a high aspect ratio semiconductor-metal hybrid nanosystem in which a SiGe nanowire tip is selectively decorated with a gold metallic cap. The tip mechanically touches a counter electrode to generate a nanojunction, and upon exposure to molecules, a metal-molecule-metal junction is formed. Adsorption of chiral molecules at the gold tip induces chirality in the localized plasmonic resonance at the electrode-tip junction and manifests in an enantiospecific current response.