Gold Skeleton Research Articles

Swim into the light

Robotics A bio-inspired swimming robot that mimics a ray fish can be guided by light. Park et al. built a 1/10th-scale version of a ray fish with a microfabricated gold skeleton and a rubber body powered by rat heart muscle cells. The cardiomyocytes were genetically engineered to respond to light cues, so that the undulatory movements propelling the robot through water would follow a light source. Science , this issue p. [158][1] [1]: /lookup/doi/10.1126/science.aaf4292

Phototactic guidance of a tissue-engineered soft-robotic ray.

Inspired by the relatively simple morphological blueprint provided by batoid fish such as stingrays and skates, we created a biohybrid system that enables an artificial animal--a tissue-engineered ray--to swim and phototactically follow a light cue. By patterning dissociated rat cardiomyocytes on an elastomeric body enclosing a microfabricated gold skeleton, we replicated fish morphology at 1/10 scale and captured basic fin deflection patterns of batoid fish. Optogenetics allows for phototactic guidance, steering, and turning maneuvers. Optical stimulation induced sequential muscle activation via serpentine-patterned muscle circuits, leading to coordinated undulatory swimming. The speed and direction of the ray was controlled by modulating light frequency and by independently eliciting right and left fins, allowing the biohybrid machine to maneuver through an obstacle course.

ChemInform Abstract: Highly Efficient Heterogeneous Aerobic Cross‐Dehydrogenative Coupling via C—H Functionalization of Tertiary Amines Using a Nanoporous Gold Skeleton Catalyst.

AbstractZero‐valent nanoporous gold is shown to be a robust and green heterogeneous catalyst for α‐C—H functionalization of various tertiary amines.

Electrochemical Biosensor Based on Nanoporous Au/CoO Core-Shell Material with Synergistic Catalysis.

An ultrathin CoO layer is deposited on the skeleton surfaces of a nanoporous gold (NPG) film by using atomic layer deposition, creating a flexible electrode. Detailed characterization demonstrates the superior performance of the flexible NPG/CoO hybrids for electrochemical catalysis. The NPG/CoO hybrid not only achieves high catalytic activity for glucose oxidation and H2O2 reduction, but also exhibits a linear dependence of the electrical signal on the concentration of glucose and H2O2 molecules in the electrolyte. Meanwhile, the sensitivity for H2O2 reduction can be as high as 62.5 μA mm(-1) cm(-2) with linear dependence on the concentration in the range of 0.1-92.9 mm. The high sensitivity is proposed to result from the synergistic effect of Au and CoO at the interfaces, and the high conductivity of the gold skeleton with a large surface area. The superior electrochemical performance of this hybrid electrode is promising for future potential applications in various transitional-metal-oxide-based electrochemical electrodes.

Hydrogen evolution at nanoporous gold/tungsten sulfide composite film and its optimization

Development of efficient and economical electrochemical systems for water splitting is a key part of renewable energy technology. Amorphous films of tungsten sulfide have been deposited by electrochemical reduction of tetrathiotungstate ions (WS42−) on dealloyed nanoporous gold (NPG) for electrochemical hydrogen evolution reaction (HER). The electrocatalytic performance has been proved to be sensitive to the thickness of the deposited layer, with an optimal deposition time of 600s identified. The bi-continuous nanoporous morphology of the composites has been confirmed by transmission electron microscopy (TEM), and is beneficial for high exposure of catalytic sites and electrolyte access to the electrode surface. High-resolution TEM (HRTEM) has been employed to characterize the strong adhesion between the ultrathin film (less than 1nm) and gold skeleton, allowing rapid charge transfer and long-term stability. The measured Tafel slope of 74mVdec−1 implies an underlying Volmer-Heyrovsky HER mechanism.

Highly efficient heterogeneous aerobic cross-dehydrogenative coupling via C-H functionalization of tertiary amines using a nanoporous gold skeleton catalyst.

We report for the first time that zero-valent nanoporous gold (AuNPore) is a robust and green heterogeneous catalyst for α-C-H functionalization of various tertiary amines. AuNPore combines with molecular oxygen at 80 °C or tert-butyl hydrogen peroxide at room temperature and catalyses the heterogeneous cross-dehydrogenative coupling (CDC) reaction efficiently to afford the corresponding C-C and C-heteroatom coupling products in good to excellent yields with excellent reusability.

Determination of hydrogen peroxide using a Prussian Blue modified macroporous gold electrode

We describe an electrochemical sensor for hydrogen peroxide (H2O2) that is making use of Prussian Blue (PB) electrodeposited on a macroporous (mp) gold skeleton electrode. An mp-Cu film was first prepared as a template and the converted into an mp-Au film through a replacement reaction without destructing the structure. Next, a layer of PB was electrochemically deposited on the surface of the mp-Au film. The surface morphology of the electrode was characterized by scanning electron microscopy. Attenuated total reflection infrared spectroscopy and X-ray photoelectron spectroscopy were applied to confirm the structural features. The mp-PB/Au film electrode displays high electro-catalytic activity for the reduction of H2O2 at a working potential of −50 mV (vs. Ag/AgCl) and is very stable. It has a linear response to H2O2 in the 50 μM to 11.3 mM concentration range and a sensitivity of 767 μA∙mM−1 cm−2. The electrode also revealed good selectivity in the presence of electro-active species such as ascorbic acid and uric acid.

Nanoporous gold supported cobalt oxide microelectrodes as high-performance electrochemical biosensors

Tremendous demands for electrochemical biosensors with high sensitivity and reliability, fast response and excellent selectivity have stimulated intensive research on developing versatile materials with ultrahigh electrocatalytic activity. Here we report flexible and self-supported microelectrodes with a seamless solid/nanoporous gold/cobalt oxide hybrid structure for electrochemical nonenzymatic glucose biosensors. As a result of synergistic electrocatalytic activity of the gold skeleton and cobalt oxide nanoparticles towards glucose oxidation, amperometric glucose biosensors based on the hybrid microelectrodes exhibit multi-linear detection ranges with ultrahigh sensitivities at a low potential of 0.26 V (versus Ag/AgCl). The sensitivity up to 12.5 mA mM⁻¹ cm⁻² with a short response time of less than 1 s gives rise to ultralow detection limit of 5 nM. The outstanding performance originates from a novel nanoarchitecture in which the cobalt oxide nanoparticles are incorporated into pore channels of the seamless solid/nanoporous Au microwires, providing excellent electronic/ionic conductivity and mass transport for the enhanced electrocatalysis.

Thermally Stable Nanoporous Gold-Alumina Core-Shell with Tunable Optical Transmission

Tuning localized surface plasmon resonance (LSPR) of nanoporous metals is crucial to manipulate light within tiny volumes for the implementation of optical devices at the nanoscale. Herein, nanoporous gold-alumina core-shell films with constant gold skeleton and variable alumina sheaths are fabricated by means of chemical corrosion and subsequent atomic layer deposition. Optical transmission properties of these composite films can be tailored due to LSPR excitations of the three-dimensional gold skeleton and alterable alumina shells as the surrounded dielectrics. The widely tunable light transmission and significantly improved stability are thus suggested to incorporate nanoporous gold-alumina core-shells into promising nano-devices with reliable performance.

Nanoporous gold–alumina core–shell films with tunable optical properties

Tuning of the localized surface plasmon resonance (LSPR) of nanoporous metals is at theheart of manipulating light within extremely small volumes for the implementation ofoptical devices at the nanoscale. In this work, nanoporous gold–alumina core–shellfilms with fixed gold skeletons and different thicknesses of alumina shells arefabricated using chemical corrosion and subsequent atomic layer deposition. Opticaltransmission of the nanoporous composite films can be tailored through LSPRexcitations of the three-dimensional gold skeleton and the alterable alumina shells asthe covering dielectric. A 92 nanometer red-shift of the LSPR band is attainedvia its dielectric medium dependence and the comparable decay length withpore size. The widely tunable optical transmission and significantly improvedstability thus suggest incorporating nanoporous gold–alumina into promisingnano-devices with reliable performance. Low temperature surface decoration (<100 °C) provides a universal route to tune the optical properties while retaining the spatialgeometry of the metallic nanostructures.

Alumina coating of ultrafine nanoporous gold at room temperature and their optical properties

Amorphous alumina is deposited on chemically etched nanoporous gold films using atomic layer deposition at room temperature. Nanoporous gold with ultrafine pores of 7 nm in diameter is uniformly coated with alumina film as thin as 1.4 nm. Localized surface plasmon resonance of gold skeleton exhibits a detectable red-shift in the optical transmittance spectra, the magnitude of which depends on the thickness of the alumina layer. The tunable optical properties of nanoporous gold–alumina composites provide one possibility for implementing miniaturized optical devices with high performances.

Gold phosphine cluster compounds: Chemical and crystallographic difficulties

Compared with most routine structure determinations, analyses of gold cluster compounds are very measuring-time, computer-time, and man-time consuming, and give less accurate results. However, they are equally useful and relevant as far as chemical information is concerned, even when only the gold skeleton and its connectivity with the ligands have been determined. TheR value is a poor guide to the value of a structure determination of this kind. One may even question whether one should take all possible precautions (change X-ray tubes, measure crystal faces, measure high-order reflection intensities) and try to locate light atoms, or perform three or more incomplete analyses of different compounds; certainly the latter gives more chemical information. Of course, none of the difficulties summarized in this note are unique for gold cluster compounds; the conclusions given here are valid generally.

Increasing the vertical dimension of occlusion

A procedure for creating a balanced occlusion with cast gold crowns has been described. The procedure has several advantages. 1. When the gold skeleton crowns have been placed in the mouth and centric relation has been obtained, it is equivalent to having located the anatomic hinge axis of the mandible accurately. There is no fear that an error will develop when it is transferred to the articulator. 2. When the interfering spots on the gold skeleton crowns have been ground so the anterior teeth can come into edge to edge contact in right and left and forward mandibular positions, the dictates of the jaw movements have been carried out, and the precise degree of the vertical opening necessary has been established. 3. If there is a functional irregularity on one or both sides, the physiologic movement (including the Bennett movement) will have been accounted for because the data was obtained in the mouth which is the perfect articulator—the one no man can duplicate. 4. When the voids in the occlusal surfaces of the gold skeleton castings are filled with casting wax and chewed in, the small spines that jut into the voids permit the maintenance of the steepness of cusps and facilitate the final carvings of the occlusal surfaces when removed from the mouth. When the gold occlusal surfaces are cast directly to the gold skeleton crowns, the crowns are completed, as is the problem of the increase of the vertical dimension of occlusion. It is to be hoped that the simplicity of this method will be a stimulant for the practice of a much neglected phase of dentistry.