Gold Bulletin最新文献

The catalytic efficacy of monometallic (Pd NPs) vs bimetallic nanocatalyst (Au NPs and Pd NPs supported on rGO) towards the one-pot synthesis of spirooxindole derivatives has been compared under mild reaction conditions. The multicomponent reaction comprised of reaction of substituted isatins, malononitrile, and 1,3-dicarbonyl compounds to synthesise series of diverse spirooxindoles. The nano-Au–Pd@rGO catalyst showed enhanced catalytic activity in the synthesis of spirooxindoles when compared to that of the monometallic nano-Pd/rGO catalyst which may be indicative of potential synergistic effect in the bimetallic catalyst viz Au and Pd NPs facilitating the accelerated synthesis of spirooxindoles in excellent yields. This methodology has the advantages of utilisation of non-toxic solvent, higher product yields, and lower reaction times at room temperature. Also, higher yields for spirooxindoles in case of substituted carbonyl compounds were observed, an indicative of the gem-dialkyl effect responsible to favour higher yields for spirooxindoles synthesised with di-methyl substituted cyclohexan-diones with respect to the unsubstituted ones for both catalytic systems.

Additive Manufacturing (AM) allows to manufacture new designs and novel geometries interesting for jewelry and watchmaking items. However, pure gold and gold alloys are challenging materials to manufacture by Laser Powder Bed Fusion (LPBF). Due to the low absorptivity at 1 064 nm Infrared (IR) wavelength combined to high thermal conductivity, it is difficult to manufacture pure gold and gold-based alloys by this process. Recent evolutions in laser technology allowed to build a machine using a 515 nm “green” laser. By changing the wavelength (1 064 nm to 515 nm), absorptivity can be improved from 7 to 37%. This paper will focus on 18 karat gold single tracks analysis produced by both wavelengths on a steel substrate. Different melting states will be detailed and indexed in order to select, correctly, machine parameters for producing gold items. It will be shown that 515 nm laser is more adapted to the material than 1 064 nm laser for manufacturing gold alloys.

Nanotechnology is an emerging field with a multitude of applications in medicine, agriculture, and engineering. To date, several methods are used for the synthesis of metallic nanoparticles including chemical, physical, and green methods. The later method is preferred for the synthesis of NPs due to its safe nature, efficiency, and minimal toxicity. Recently, gold nanoparticles (AuNPs) have been attracting attention due to their excellent biocompatibility and diverse medical applications. A diverse group of microorganisms or their metabolites (bacteria, fungi, and yeast) have been utilized to synthesize AuNPs from their respective bulk salts. This review focuses on the resources exploited for biosynthesis of AuNPs, the current understanding about their synthesis, and the emerging trends, along with their mechanistic antimicrobial and anticancer applications. This review also highlights the current challenges and future potential applications of AuNPs.

Chloroalkanes have richer structures and cheaper costs than iodide/brominated compounds, while rarely used as electrophilic reagents for constructing C(sp³)–C(sp³) bonds due to their low reduction potential and strong bond dissociation energy. Recently, a new catalytic strategy involving dinuclear gold complexes has overcome this limitation. The photoinduced gold-catalyzed mode initiated the C(sp³)–Cl electrophilic activation, lead to the divergent conversion of chloroalkanes as chloroalkyl, alkyl cation and carbene equivalent precursor of carbon chain propagation, and involved a novel mechanism of inner-sphere SET process between dinuclear gold complex catalyst and chloroalkane.

Etching solutions of spent printed circuit boards contain a small amount of valuable metals like Au(III) and Pd(II). In order to meet the increasing demand for gold and palladium, it is necessary to recover these metals from the etching solutions. In this work, solvent extraction experiments were done to separate Au(III) from the synthetic hydrochloric acid solutions containing Pd(II), Cu(II), and Ni(II). Single Cyanex 272 and TBP and their mixture were employed to investigate the selective extraction of Au(III) from other metal ions in the HCl concentration range from 1 to 9 M. Single Cyanex 272 and the mixture of Cyanex 272 and TBP successfully separated Au(III) from the solution, while a small amount of Pd(II), Cu(II) and Ni(II) were co-extracted with Au(III) by TBP. The mixture of Cyanex 272 and TBP showed synergism for the extraction of Au(III). The dependence of Au(III) extraction on the mole fraction of TBP in the mixture was pronounced when HCl concentration was 1 and 3 M. The Au(III) loaded into the mixture was completely stripped by low concentration of thiourea and sodium thiosulfate. Pure gold metal was recovered from the thiourea stripping solution by chemical reduction with ascorbic acid. Complete reduction of Au(III) was possible at 80 °C for 30 min when the molar ratio of ascorbic acid to Au(III) was 20.

Cancer was the world’s second major cause of death. Several treatments were available, including chemotherapy, radiotherapy, immunotherapy, and surgery. However, they are restricted due to their risk to normal cells, their ability to destroy the immune system, and conferring increased risk of secondary cancer development. Nanotechnology was extensively researched and used in cancer treatment because nanoparticles could play an essential role in drug delivery. Furthermore, nanoparticle drug delivery systems have been shown to help overcome cancer-related drug resistance. Gold nanoparticles have unique physical, chemical, and biological properties, making them suitable candidates for non-toxic drug carriers. Because of their nanorange size, surface modifications of gold nanoparticles could improve their stability, minimize nanoparticle aggregation, and enhance attachment to anti-cancer agents and target cells, further increasing their ability to penetrate cell membranes and reduce toxicity. This review aims to discuss the current research in targeting drug delivery for anti-cancer agents using gold nanoparticles. By conducting a literature search through the PubMed and Scopus database up to April 2022 using the term gold nanoparticles, targeted drug delivery, chemotherapy, gene therapy, and cancer, this review summarized report on the implementation of gold nanoparticles for targeted drug-delivery systems for cancer therapeutics. The targeting ligands included folic acid, aptamers, hyaluronic acid, glutathione, peptides, and antibodies. According to the findings of studies, implementing gold nanoparticles as nanocarriers significantly improves drug delivery of anti-cancer agents to cancer cells without affecting other untargeted cells. Enhanced cell uptake, increase in drug toxicity, inhibition of tumor growth, and selective drug target are also reported to be the advantages of gold nanoparticle-based targeted drug delivery carriers.

Protein oligomerization contributes to Alzheimer’s disease development (AD). A nanoparticle that can speed up the oligomerization of proteins is generally considered harmful. Gold nanoparticles (AuNPs) have been reported to be making headway in biological platforms, but they may also have the capacity to stimulate protein oligomerization. Our goal herein was to investigate the neurotoxicity and oligomerization of amyloid-β-1-42 (Aβ_1-42) in the presence of AuNPs. The precipitation approach was used to create AuNPs, which were then analyzed using transmission electron microscopy (TEM), ThT, Congo red, and CD spectroscopy. The results demonstrated that the 50-nm-sized fabricated AuNPs guided acceleration in Aβ_1-42. In addition, cytotoxicity studies on PC 12 cells showed that Aβ_1-42 with AuNPs were less toxic than untreated oligomers Aβ_1-42 in terms of inducing cell death, oxidative apoptosis, stress, and membrane leakage. In conclusion, our investigation sheds light on how AuNPs stimulate the development of cytotoxic oligomers by binding to proteins in Alzheimer’s disease.

In this study, carbon quantum dots (CQDs) were first synthesized using a hydrothermal method, and then, Au@SiO₂ core-shell nanomaterials were synthesized using layer-by-layer assembly. CQDs were adsorbed on the surface of Au@SiO₂ nanoparticles through self-assembly to form Au@SiO₂/CQDs nanocomposite materials. Transmission electron microscopy and X-ray diffraction were used to characterize the size, shape, element composition, and structure of nanocomposites; ultraviolet-visible absorption spectroscopy and fluorescence spectroscopy were used to analyze the optical properties of nanocomposites. The results show that Au@SiO₂/CQD nanomaterials have a core-shell structure with good morphology and exhibit excellent luminescence characteristics. The electrochemical performance of nanocomposites was characterized using electrochemical means, and a hydrogen peroxide sensor was constructed for the sensitive detection of hydrogen peroxide, thus realizing the rapid and sensitive detection of hydrogen peroxide at levels as low as 0.2 mM. The electrode GCE modified with Au@SiO₂/CQDs exhibits good selectivity and stability in the detection of hydrogen peroxide.