Single crystal gold clusters (10 nm in size) have been collectively manipulated on mono- and bi-layered MoS2 islands (up to 20 µm) grown on SiO2 using AFM. On the monolayer the clusters tend to move in a direction corresponding to the zigzag alignment of the Mo and S atoms, and assemble into long striation patterns parallel to the scan direction. The distance between consecutive stripes is inversely proportional to the cluster concentration and size. A more detailed observation based on SEM shows that within each stripe the clusters remain separated by gaps of few nm in width possibly caused by electrostatic repulsion and/or the roughness of the SiO2 substrate (~2 nm). The stripes also proved to be thermally stable, preserving their superstructures up to 823 K. On the bilayer gold clusters are much less prone to move and assemble into stripes. These results suggest that the formation of nanostructures resulting from collective manipulation of metal clusters can be oriented by a properly chosen scan path in a rather straightforward way (as compared to one-by-one displacement of single clusters). The goal of forming µm-long but nm-thin wires with a geometrically defined shape could be easily reached with the use of smoother substrates or TMD materials with lesser charge transfer to metals adsorbed on them.

A facile one-pot and environmentally friendly method was developed to synthesize multi-branched flowerlike gold (Au) nanostructures by reducing chlorate gold (HAuCl4) with hydrogen peroxide (H2O2) in the presence of sodium citrate. The multibranched Au nanostructures were characterized by transmission electron microscopy and Ultraviolet-visible (UV-vis) absorption spectroscopy. The molar ratio of sodium citrate to HAuCl4 and the concentrations of the reacted reagents play important roles in the formation of multibranched Au nanostructures. The multibranched Au nanostructures with sharp tips exhibit excellent surface-enhanced Raman scattering (SERS) ability of 4-aminothiophenol (PATP). The experimental and simulated results both confirm that the photoinduced catalytic coupling reaction of PATP transformation to 4,4′-dimercaptoazobenzene occurs on the surface of multibranched Au nanostructures at a high power during the SERS measurement. It is believed that these multibranched Au nanostructures may find potential applications in SERS, biosensors, and the photoinduced surface catalytic application fields.

In this study, feasibility of spark discharge technique to generate mixed metal nanoparticles is demonstrated. Two immiscible metals Au and Zn are selected to prepare AuZn mixed nanoparticles. Ignition of spark between Au and Zn electrodes under normal pressure, in the presence of carrier gas, leads to formation of mixed nanoparticles by condensation and nucleation. Online particle size-distribution is monitored by a scanning mobility particle sizer on changing carrier gas flow rate and capacitor charging current during co-sparking between Au and Zn electrodes. The technique provides flexibility to generate binary mixture of AuZn nanoparticles in the size range of 10-80 nm. Distribution of Au and Zn in the prepared mixed nanoparticles is mapped by scanning electron microscopy and high resolution electron microscopy.

Lung surfactant (LS), a thin layer of phospholipids and proteins inside the alveolus of the lung is the first biological barrier to inhaled nanoparticles (NPs). LS stabilizes and protects the alveolus during its continuous compression and expansion by fine-tuning the surface tension at the air-water interface. Previous modelling studies have reported the biophysical function of LS monolayer and its role, but many open questions regarding the consequences and interactions of airborne nano-sized particles with LS monolayer remain. In spite of gold nanoparticles (AuNPs) having a paramount role in biomedical applications, the understanding of the interactions between bare AuNPs (as pollutants) and LS monolayer components still unresolved. Continuous inhalation of NPs increases the possibility of lung ageing, reducing the normal lung functioning and promoting lung malfunction, and may induce serious lung diseases such as asthma, lung cancer, acute respiratory distress syndrome, and more. Different medical studies have shown that AuNPs can disrupt the routine lung functions of gold miners and promote respiratory diseases. In this work, coarse-grained molecular dynamics simulations are performed to gain an understanding of the interactions between bare AuNPs and LS monolayer components at the nanoscale. Different surface tensions of the monolayer are used to mimic the biological process of breathing (inhalation and exhalation). It is found that the NP affects the structure and packing of the lipids by disordering lipid tails. Overall, the analysed results suggest that bare AuNPs impede the normal biophysical function of the lung, a finding that has beneficial consequences to the potential development of treatments of various respiratory diseases.

In situ, real-time monitoring of a dehydration of poly(vinyl alcohol) (PVA) film is researched. The technique based on the incorporation plasmonic nanocages (NCs) between the two identical layers of PVA, (PVA)/NCs/(PVA) film, and its sensitivity to the variation of the refractive index of the surrounding PVA film via desorption water. The dehydration time increases from 180 (s) to 1800 (s) as the content of the PVA in the films increases twice, from (PVA)/NCs/(PVA) to (PVA)2/NCs/(PVA)2. Such effect could be explained by different rate of the molecules desorption from the PVA based films. Specifically, the dehydration rate is of 0.22 (vol% per s) and 0.026 (vol% per s) for (PVA)/NCs/(PVA) and (PVA)2/NCs/(PVA)2 films, respectively. The dehydration rate constant reduces from -50×10-4 (s-1) to -4.3 ×10-4 (s-1) as the content of PVA increases from (PVA)/NCs/(PVA) to (PVA)2/NCs/(PVA)2 films, respectively.

Aerogels are light-weight porous materials that can tolerate the processing steps required for designing and creating an electric circuit such that the aerogel can be utilized as a substrate for device fabrication. Previous studies have shown the biostability and biocompatibility of polyurea crosslinked silica aerogels both in vivo and in vitro and have demonstrated the potential use of aerogels in biomedical applications. In vitro studies have shown that in the presence of an applied electric field neurites regeneration rate was greater on crosslinked silica aerogels than on tissue culture petridish used as a positive control. Currently, epineural suturing and nerve grafting are the gold standards for surgical reconstruction of injured nerves. However, because they rely on passive mechanisms for reapproximating the distal and proximal terminals they often lead to partial or no recovery leaving room for improvement. The present study investigates the feasibility of a wireless aerogel–based electrically-stimulating implant intended for nerve repair applications. Here the authors report on RF coupling between a secondary coil and a primary coil to wirelessly energize an interdigitated electrode array consisting of eleven interlocking fingers, created on a silica aerogel substrate. The coupling strength was tested both in air and in an animal model, as a function of distance and will be reported. This study focuses on in vivo evaluation and feasibility assessment of a novel active 3-D aerogel-based peripheral nerve repair device. The device utilizes induced EMF to establish a current (hence electrical stimulation) in predetermined pathways where nerve stumps will be confined to. Fundamental differences between in vitro and in vivo models necessitate the in vivo approach. The novel inductively-powered electrical stimulation aerogel-based device utilizes previously established 3-D confinement method for immobilization of nerve stumps, taking advantage of the mesoscopic surface roughness, unique to aerogels. The technique is tested on a mechanically strong, lightweight, porous, and biostable aerogel. Lithographic techniques, gold (Au) thin film metallization, and Faraday induction is used for circuit design, development, and activation.

There is a huge variety of modular product designs for smartphones (concept studies, prototypes, products on the market), and a similarly high variety of circular economy aspects related to these different design approaches. Modularity requires initially more material input but pays off as the consumer is embracing the possibilities of modularity. Key materials for modularity features are gold, beryllium, and neodymium, etc.

On the example of smartphones modularity as a strategy for circular design is analyzed in detail. Modularity of products is a design trend, which is supposed to facilitate reparability, recyclability, and/or upgradeability. However, modularity requires some design changes. The most evident design change is the need for connectors to provide mechanical and electrical contact between individual modules. Depending on the nature and use scenario of a connector reliability, robustness, wear resistance, and non-reactive surfaces are required. The paper explains different modularity approaches for smartphones, some of these being already available in the market, others are still in a conceptual phase. Analyzing technologies for modularity leads to a group of “modularity materials,” which are essential for such circular design approaches, but at the same time are among those materials with a large environmental footprint or limited recyclability. A life cycle assessment of a modular smartphone shows a roughly 10% higher environmental life cycle impact compared with a conventional design. This needs to be compensated by reaping the circular economy benefits of a modular design, i.e., higher likeliness of getting a broken device repaired, extending the lifetime through hardware upgrades and refurbishment.

The generation of AuNPs was realized in presence of gold chloride (Au3+), and citrate solution as reducing agent. The production of AuNPs was proved by the color change in the solution; from yellow to red wine. Purified nanostructures synthesized at citrate/Au3+ molar ratio of 1.0/10.0 evidenced an absorption peak at 526 nm attributed to the localized surface Plasmon Resonance (LSPR) which suggested the formation of small gold nanoparticles (NPs). The decrease of citrate/Au3+ molar ratio at 1.0/3.0 provoked a growing of gold nanostructures, which was evidenced by a red shift in the SPR at 546nm. High Resolution Transmission Electron Microscopy technique evidenced the spherical form and sizes for both nanoparticles at the range 10-15 nm (small NPs) and 20-25 nm (big NPs), respectively. Electron Diffraction (ED) patterns for both sizes evidenced the (111), (200), (220), (311), and (222) reflections of face centered cubic (FCC) gold nanostructures. Studies of energy-dispersive X-ray Spectroscopy indicated peaks at 1.65, 2.12, 9.71, 11.58 and 13.38 keV for both nanostructures, which suggests the presence of gold into the crystalline structure of the nanoparticles. Interaction tests were carried out in presence of marine crustaceans and different concentrations of gold nanoparticles; including a control test. Both sizes evidenced to be toxic when the concentration and exposure time were increased.

We visually observed color changes of discontinuous gold surfaces on paper substrates through localized surface plasmon resonance (LSPR) at room temperature due to surface diffusion of gold nanostructures. Isolated nanoparticles and an uncompleted nanosheet of gold were obtained by thermal vapor deposition. After preservation for 8 months in air at room temperature, the particle sizes and shapes remarkably changed with color changes. The surface diffusion of the discontinuous gold on the paper would be derived from solid-state dieting, resulting in the growth of the nanosheet defect and coalescence of the nanoparticles. This is due to the total energy minimization of the surfaces of gold nanostructures and the paper and the interface between gold and the paper.

Data on the distribution of the precious metals (Au, Ag and the platinum=group elements Ru, Rh, Pd, Os, Ir, Pt) are rapidly accumulating as a consequence of the application of microbeam analytical techniques such as the electron microprobe, the proton microprobe, and the ion microprobe. The new data obtained with these techniques build on knowledge accumulated over the last 140 years using bulk analytical methods (e.g. spectrographic). The nature of the occurrence, the concentrations, and the variation in amount s of precious metals in minerals and mineral products are reviewed with comments as to the significance of the results with respect to industrial and environmental concerns. Future directions in mineral-specific analysis of trace precious-metal concentrations and applications outside of process mineralogy are discussed.

To investigate the effects of adding Au nanoparticles (AuNPs) to TiO2 films on the crystallization, phase transformation, and photocatalysis, films of both TiO2 and TiO2 embedded with AuNPs (Au–TiO2) with various characteristics were prepared by using the dip-coating method with preheating and post-heating treatments. The AuNPs acted as anatase nucleation agents and crystallized a lot of small anatase crystals with sizes of tens of nanometers, which suppressed the growth of anatase crystals that are large enough for them to transform into rutile crystals, resulting in repression of the transformation from anatase into rutile. The AuNPs affected the progress of the photocatalytic and adsorption reactions, resulting in improved photocatalytic activity. Of all the films we tested, the Au–TiO2 film preheated at 400 °C and post-heated at 400 °C (AT400-400), which consisted of small anatase crystals with high covalent character and high crystallinity, contained dispersed AuNPs with the smallest average crystallite size and showed the highest photocatalytic activity. This high activity resulted from the high reaction rate constants for adsorption and photocatalysis.

Single crystal Au microspheres, of 3 μm diameter, with sputter-deposited Ni surface layers, of 40 or 80 nm thickness, were tested in compression at three loading rates to investigate the role of thin passive layers on the mechanisms of plastic deformation of small-volume FCC ductile metal samples. The Ni layer resulted in an increase in the incipient yield force by about 10%. Micro-cracking of the Ni layer was observed to occur with incipient yielding. The estimated apparent activation volume of the incipient plastic deformation process was found to be nearly identical for the Ni-coated and the uncoated Au microspheres. This suggests that, while the stress required to initiate incipient plastic deformation was increased by the constraint imposed by the Ni layer, the subsequent plastic flow occurred by a dislocation nucleation and glide mechanism that is essentially the same as that occurring in an unconstrained Au microsphere.

The reprocessing of tailings or gold mine waste dumps to extract gold has become an attractive proposition for mining houses worldwide because of the availability of gold which was not easily recovered using old technologies. This study seeks to exploit the novel properties of nanostructured materials in enhancing gold extraction from gold mine tailings. The beneficiation of slimes or tailings involved taking samples for mineralogical studies, synthesis of a novel adsorbent medium (nano C-MgO) prepared by using both chemical and mechano-synthesis methods, oxidative pre-treatment of flotation concentrates, cyanidation and final recovery of the precious metal from solution in a Carbon in Column (CIC) system. The nanocomposite adsorbent was studied by powder X-ray Diffraction (XRD) for structural analysis, Field Emission Scanning Electronic Microscopy (FESEM) for surface morphology, Energy-dispersive X-ray spectroscopy (EDX) for elemental analysis and Fourier Transform Infrared (FTIR) spectroscopy for chemical structure analysis. The Brunauer-Emmett-Teller (BET) Surface Area Analysis procedure was employed to determine the total specific surface area of the nano-adsorbent. Representative tailings samples of 100-500 g were obtained for different analytical investigations using a riffle splitter. The tailings grade was analysed using the Atomic Absorption Spectroscopy (AAS) technique and was found to be an average of 0.5 g/tonne. A comparative Pseudo-Equilibrium test showed that the novel C-MgO nano adsorbent had an average of 84% recovery against 70 % for convectional activated carbon. The average crystalline size of 4.5 -11nm for the majority of MgO nanoparticles was obtained using Debye-Scherrer formula. FESEM confirmed that nano MgO was porous in nature and highly agglomerated whilst EDX exhibited the successful synthesis of the nano-composite product. This work also shows that the nano-adsorbent presents a huge potential for application in the conventional processes for gold adsorption.

Recently the use of nanomaterials for the diagnosis and detection of malignant diseases has increased due to the versatility and properties of these nanostructures. For this work 60 nm commercial gold nanoparticles (TED PELLA inc.) and Nanostars manufactured by chemical synthesis (precursor reagent: HAuCl4, cationic surfactant: CTAB) of 117 nm were used for coating. Malachite green Isotyocianate (MGITC), mPEG-SH and ortho-pyridyldisulfide-polyethylene glycol-N-succinimidyl propionate (OPSS-PEG-NHS) was used. A SERS active nanoparticle complex was obtained by addition of a solution of MGITC to the gold nanoparticles colloidal solution in a 1:6 ratio. Later, an mPEG-SH solution was added to the mix. The nanoparticle-MGITC-mPEG-SH complex stability was revised using a UV-Vis spectrophotometer and a JEOL JEM 1000 transmission electron microscope. The SERS spectra were registered with a Raman Thermoscientific DXR microscopy system. Amplified bands associated with OPSS-PEG-NHS were identified in 389, 622, 859, 929, 1080, 1283, 1360, 1443, 1490 and 1450 cm-1. The results indicate that through this methodology it is possible to identify gold nanomaterials coated with polymer through the Raman technique. In addition, greater amplification is observed with the use of nanostars compared to gold spheres. Finally, these nanomaterials are available for the marking of specific membrane for the study of different types of cancer by the SERS technique.

Synthesis of functional noble metal nanoparticles (AuNPs, AgNPs, and PdNPs) and its multi-metallic analogues have received greater attentions for selective applications. The selective applications of the these nanoparticles essentially requires the processability of as synthesized nanoparticles in the medium of desired polarity index that manifest the potential exploration of nanomaterial based design in targeted area. The use of conventional reducing and stabilizing agents during routine synthesis of such nanoparticles are not suitable with the system of practical significance and require additional reagents that limit the optimum activity of nanomaterial in targeted design. According there is a challenging issue in the synthesis of noble metal nanoparticles that allow the controlled synthesis of such nanoparticles involving same starting material with option to control the processability of as generated nanomaterial in the system of desired polarity index. The present report is focused on such challenging issues. We have found that 3-aminopropyltrimethoxysilane (3-APTMS) capped noble metal cations can be precisely converted into respective monometallic, bimetallic and trimetallic analogues and can be made processable in water at one end having controlled option to reversed the processability of the same in the toluene as a function of small organic reducing agents. The organic reducing agents not only convert 3-APTMS-capped noble cations into respective nanoparticles but also control the processability of the as generated nanoparticles in the systems of desired polarity index. The similar process also allows the synthesis of function bimetallic and tri-metallic nanoparticles. The role of cyclohexanone, formaldehyde and acetone in the presence of 3-APTMS is reported.

Nanoporous metals obtained by dealloying have attracted significant attention for their unusual catalytic properties, and as model materials for fundamental studies of structure–property relationships in a variety of research areas. There has been a recent surge in the use of these metals for biomedical and bioanalytical applications, where many exciting opportunities exist. The goal of this article is to provide a review of recent progress in using nanoporous metals for biological applications, including as biosensors for detecting biomarkers of disease and multifunctional neural interfaces for monitoring and modulating the activity of neural tissue. The article emphasizes the unique properties of nanoporous gold and concludes by discussing its utility in addressing important challenges in biomedical devices.

The size and strain-rate dependence of plastic deformation in Au microspheres of diameter ranging from 0.8 to 6.0 µm was investigated at room-temperature using flat-punch micro-compression testing. The contact yield stress was observed to increase with decreasing microsphere diameter. The apparent activation volume, V*, associated with the rate dependent plastic deformation remained essentially constant between 4 and 6b 3 for 0.8 and 1.0 µm spheres over strains up to 20% whereas it increased from 12 to 42b 3 for the larger 3.0 and 6.0 µm diameter specimens. The initiation of plastic deformation within the microspheres was also found to be highly dependent upon sphere diameter and strain rate with associated V*, and apparent activation energy, Q*, values of 0.4b 3 and 0.02 eV for 0.8 µm diameter spheres increasing to 4.1b 3 and 0.16 eV for 6.0 µm diameter spheres. These values indicate that initial plasticity is controlled by heterogeneous nucleation events that are consistent with a surface self-diffusion mechanism.

Conventional metallic antibacterial materials release metal ions and reactive oxygen species (ROS) for killing bacteria. Herein, we found that nanoporous gold (NPG) exhibits antibacterial activity (AA) at an intermediate relative humidity (RH) of 60% against Escherichia coli and Staphylococcus epidermidis in contrast to the inert behavior of bulk gold. The dependence of AA on RH, morphological observations of bacteria on NPG, and transcriptomic analyses of NPG-treated Escherichia coli were investigated. These observations collectively suggest that biological processes in cell walls containing peptidoglycan and cell membranes are significantly disrupted by direct contact with NPG. Metal ions and ROS were not detected, and therefore are not responsible for the present antibacterial properties of NPG. The catalytic nature of NPG may be responsible for its AA, probably because of lattice distortion at the surface of nanosized ligaments with large curvature.

Gold/albumin core/shell nanoparticles (Au/AlbNPs) was prepared by a novel aggregation/crosslinking technique and characterized by several spectroscopic and microscopy methods. Albumin, in presence of gold nanoparticles (AuNPs), is aggregated by the addition of ethanol and further stabilized by radiation-induced crosslinking using a 60Co source. Nanoconstructs are characterized to determine size, morphology and optical characteristics. The Au/AlbNPs were prepared in different ethanol and albumins concentrations. Results showed that it is possible to obtain Au/AlbNPs using ethanol 30 %v/v, albumin in different concentrations and an irradiation dose of 10 kGy. Au/AlbNP plasmon peak shifted to 530 nm, keeping the typical plasmon peak shape. The size of Au/AlbNPs is approximately double respect to the naked AuNPs and they show core/shell type morphology. The main amide peaks of albumin in FTIR spectrum can be found in the spectrum of nanoconstructs.