Gold Bulletin最新文献

Most traditional ceramic glazes employ high amounts of transition metal colorants that are toxic to the environment and can cause health issues in humans through surface leaching. Gold nanoparticles (Au-NPs) have been found to be environmentally friendly and non-toxic alternative metal colorant in ceramic glazes. The plasmon band observed with Au-NPs can result in vibrant solutions by manipulating NP size, shape, and concentration; however, the effects of traditional firing in both reductive and oxidative kilns on Au-NPs are poorly understood. Aside from ancient art processes whose mechanisms have not been fully explored, the use of Au-NPs as suspended ceramic glaze colorants remains somewhat unexplored. Au-NPs have been previously reported to diminish in size during sintering and possess significant differences in concentration with respect to reduction and oxidation firing atmospheres. As a means of studying possible degradation/renucleation processes within the glaze during firing, a systematic study introducing different diameter Au-NPs into the glaze materials was conducted with transmission electron microscopy and reflectance spectroscopy used to probe possible mechanisms which showed changes to Au-NP diameter and color intensity, making this work applicable to industry and art current practices.

Golden inverse opals additionally decorated with 15.5?±?1.5?nm gold nanoparticles are proposed as reusable substrates for surface-enhanced Raman spectroscopy (SERS). Gold nanoparticles are found to be uniformly distributed making an input of enhancement ability of spectral characteristics with the colloidal system by ten times. This technique is demonstrated to be efficient in spectral features tuning via a combination of different gold derivatives. Two lasers served for resonant, pre-resonance, and non-resonance signal analyses. Reusability of the Au-Au composite films is demonstrated for methylene blue as a stable dye deposited onto the SERS chips using a 632.8-nm resonant laser for exciting. The enhancement factor for methylene blue achieved 10⁸ and for rohodamine 6G was of about 10⁵. It was observed that rinsing of Au-Au nanocomposite SERS films with distilled water and heating up to 100?°C followed by dropping on a new portion of Au colloids onto the platform regenerates the substrates.

A self-terminated electrochemical atomic layer deposition process is developed to fabricate Au monolayer (ML) film layer-by-layer. It is found that the under potential deposited hydrogen (H_upd) provides perfect termination after each ML deposition and the further ML growth can be replicated after a surface activation using a positive potential to remove the H_upd layer. Voltammetric measurements, deposition current analysis, and EQCM show clear characteristics of UPD hydrogen surface termination and the ML deposition. Both XRR and HREED confirm the Au ML film formation. Moreover, the Au ML film appears to be effective for surface enhanced Raman effect of GO on the Au ML film.

Cancer therapy using minimal invasive technique has been a challenge since decades. In the present research, the concept of photodynamic cancer therapy (PDT) has been applied on biologically synthesized nanoparticles for the treatment of skin melanoma (B16F10) and epidermoid carcinoma (A431) cells. The biologically synthesized nanoparticles have been conjugated with a photosensitizer drug 5-aminolevulinic (5-ALA) acid to treat cancer cells by activating the protoporphyrin IX (PpIX) formation through irradiation. Bacterial strain Escherichia coli was used for the synthesis of gold nanoparticles. The size and characteristics of nanoparticles were studied with scanning electron microscope, dynamic light scattering and zeta potential analysis. The gold nanoparticles were encapsulated with polyethylene glycol (PEG) and tagged with 5-aminolevulinic acid, a photosensitizer drug. The drug was activated using a halogen lamp to enhance the production of reactive oxygen species (ROS) molecules. The cytotoxicity of pure nanoparticles and conjugated nanoparticles were assessed on skin melanoma and epidermoid carcinoma cell lines and compared against standard drug 5-ALA, and the production of ROS molecules was measured using a 2,7 dichlorofluorescein-diacetate (DCFH-DA) probe. The results indicated that pure gold nanoparticles had greater cytotoxicity on cells compared to 5-ALA and gold-5-ALA conjugate. But when the cells were subjected to irradiation, the gold-5-ALA conjugate showed higher cytotoxicity than 5-ALA and pure nanoparticles. The cytotoxic levels of gold-5-ALA conjugates were doubled which indicated greater reactive oxygen molecule production compared to other samples.

Bimetallic core-shell nanostructures have been attracted tremendous attention due to their ability to form novel materials with unique chemical, optical, and physical properties. Here, we have studied the influence of core size of Au/Ag bimetallic core-shell nanostructures on the Raman enhancement efficiency with the Raman-active probe methylene blue. The surface-enhanced Raman scattering intensity is increased with increase in the core size of Au/Ag bimetallic core-shell nanoparticles. Interestingly, the enhancement factor is found to be 6.58?×?10⁷ for the Au₁₀₀/Ag core-shell nanoparticles and allows easy detection of analyte methylene blue. Thus, surface-enhanced Raman scattering properties of the metal nanoparticles are significantly enhanced due to the Au/Ag core-shell structures and the enhancement factor is dependent on the size of the core of the bimetallic nanoparticles.

An evaluation of the improvement in radiotherapy obtained using gold nanoparticles embedded in the tumor tissues is presented for traditional treatments using X-rays and electrons and for innovative proton therapy. The possible nanoparticles’ preparation via physical, by laser ablation in liquids, and chemical techniques is presented. The use of functionalized gold nanoparticles is discussed and results from the study of uptake and decay from mice living systems are reported.

The improvement obtainable in medical images and in the dose distribution enhancement in disease tissues with respect to healthy ones is investigated.

In the present work, well-dispersed gold nanoparticles (AuNPs) were synthesised by the reduction of HAuCl_4.xH₂O using silk fibroin as a reducing agent. UV-visible spectroscopy confirmed the formation of AuNPs by showing surface plasmon resonance (SPR) at 526–518?nm. The FT-IR study revealed that the hydroxyl groups in the Tyr residue and the carboxyl groups in the Asp and/or Glu residues were the most active functional groups for the conversion of Au ion reduction. The transmission electron microscope (TEM) images showed that the formed nanoparticles were uniformly embedded in the silk fibroin solution. The AuNPs are spherical in shape with smooth edges and around 5–8?nm in diameter. Also, these possess very good stability and dispersity and can be stored for a long period. Further, the X-ray diffraction (XRD) study confirmed the nanocrystalline phase of the gold with cubic crystal structure. The biogenic gold nanoparticles displayed antibacterial activity against Gram-positive and Gram-negative bacteria, and also showed promising anticancer properties.

Gold alloys, used in the production of both hollow and solid gold chains, influence the optical and mechanical properties of various gold products. Also, the microstructure of the alloys strongly influences the mechanical properties, which have a key role in both the machinability and quality of the plates. In the present work, different compositions of gold alloys and various industrial deformation processes (annealing and rolling steps) were analyzed and optimized. The change in the production parameters and in the compositions of the alloys may lead to the formation of different levels of residual stresses within the material, which can generate a variation in the behavior of gold sheets. The microstructures after the different production processes were analyzed by OM and SEM observations, whereas the variation of mechanical properties by microhardness tests. The residual stresses were evaluated using XRD analysis and the corrosion resistance by potentiodynamic polarization tests. The results showed that with the optimized process, a higher homogeneity of the microstructure, with an increase of the quality of semi-finished products and without ruptures under roller trains, was obtained. Moreover, the grain refiner was changed and a totally non-magnetic gold alloy was developed. Finally, to improve the weldability of the final chains, a different gold welding alloy, with a lower melting point, was developed and optimized.