A urea-modified tryptophan based in situ reducing and stabilizing agent for the fabrication of gold nanoparticles as a Suzuki-Miyaura cross-coupling catalyst in water

Micro-interdigitated electrodes genosensor based on Au-deposited nanoparticles for early detection of cervical cancer

Genosensor-based electrodes mediated with nanoparticles (NPs) have tremendously developed in medical diagnosis. Herein, we report a facile, rapid, low cost and highly sensitive biosensing strategy for early detection of HPV 18 using gold-nanoparticles (AuNPs) deposited on micro-IDEs. This study represents surface charge transduction of micro-interdigitated electrodes (micro-IDE) alumina insulated with silica, independent and mini genosensor modified with colloidal gold NPs (AuNPs), and determination of gene hybridization for early detection of cervical cancer. The surface of AuNPs deposited micro-IDE functionalized with optimized 3-aminopropyl-triethoxysilane (APTES) followed by hybridization with deoxyribonucleic acid (DNA) virus to develop DNA genosensor. The results of ssDNA hybridization with the ssDNA target of human papillomavirus (HPV) 18 have affirmed that micro-IDE functionalized with colloidal AuNPs resulted in the lowest detection at 0.529 aM. Based on coefficient regression, micro-IDE functionalized with AuNPs produces better results in the sensitivity test (R2 = 0.99793) than unfunctionalized micro-IDE.

Recent applications of nanoparticles in organic transformations

A variation in the size of metal nanoparticles leads to a difference in their properties. As the size of metal nanoparticles decreases, the surface area increases which leads to an increase in the reactivity of metal nanoparticles. Metals like Au, Ag, Pd, and Pt have interesting properties when used in nanometric dimensions. They function efficiently in significant industrial processes as electrocatalysts and photocatalysts in various organic reactions. Recently, the green biosynthesis of nanoparticles has attracted the attention of researchers. With environmental pollution rising over the past few decades, metal nanoparticle catalysts could be the key to subdue the toxic effects. Being versatile, they can be used to degrade pollutants, develop solar cells, convert toxic nitroaromatic compounds, significantly reduce CO₂ emissions per unit of energy, and many more. Owing to their unique properties, nanoparticles have wide applications in biomedicine, for example, gold cages are promising agents for cancer diagnosis and therapy. Transition metal-oxide nanoparticles have been considered one of the best supercapacitor electrodes with high electrochemical performance. In this review, we have summarised fundamental concepts of metal nanoparticles over the last decade's main emphasis from 2010 to 2021. It focuses on the exceptional use of these nanocatalysts in various organic reactions. Additionally, we have also discussed the utility of these reactions and their crucial role in solving the problems of today. Through this article, we hope to provide the necessary framework needed to further advance the applications of metal nanoparticles as catalysts.

Proof of Concept: Interface of Recyclable Organogels with Embedded Palladium Nanoparticles Catalyzing Suzuki-Miyaura Coupling in Water at Room Temperature

A sustainable approach for C-C cross-coupling reaction at room temperature in water has been developed to avoid tedious Pd separation, reduce the carbon footprint, and save energy. Another important aspect is the catalyst recycling and easy product separation. α,γ-Hybrid peptides were designed to selectively use as a ligand for C-C cross-coupling catalysts as well as to form organogels. The peptides form antiparallel sheet-like structures in the solid state. The peptide containing m-aminobenzoic acid, glycine, and dimethylamine forms a whitish gel in toluene, and co-gelation with Pd(OAc)₂ results in light brown gel, which acts as a biphasic catalyst for Suzuki-Miyaura cross-coupling at room temperature in water by mild shaking. The organic-inorganic hybrid gel was characterized by rheology, field-emission scanning electron microscopy, transmission electron microscopy, and energy-dispersive X-ray analyses. On completion of the cross-coupling reaction, the basic aqueous layer (containing products) above the gel can be simply decanted and the intact organic-inorganic hybrid gel can be recycled by topping-up fresh reactants multiple times. The reaction permitted a range of different substitution patterns for aryl and heterocyclic halides with acid or phenol functional groups. Both electron-donating- and electron-withdrawing-substituted substrates exhibited good results for this transformation. The findings inspire toward a holistic green technology for Suzuki-Miyaura coupling reaction and an innovative avenue for catalyst recycling and product isolation.

Gold-Catalyzed Cross-Coupling Reactions: An Overview of Design Strategies, Mechanistic Studies, and Applications

Transition-metal-catalyzed cross-coupling reactions are central to many organic synthesis methodologies. Traditionally, Pd, Ni, Cu, and Fe catalysts are used to promote these reactions. Recently, many studies have showed that both homogeneous and heterogeneous Au catalysts can be used for activating selective cross-coupling reactions. Here, an overview of the past studies, current trends, and future directions in the field of gold-catalyzed coupling reactions is presented. Design strategies to accomplish selective homocoupling and cross-coupling reactions under both homogeneous and heterogeneous conditions, computational and experimental mechanistic studies, and their applications in diverse fields are critically reviewed. Specific topics covered are: oxidant-assisted and oxidant-free reactions; strain-assisted reactions; dual Au and photoredox catalysis; bimetallic synergistic reactions; mechanisms of reductive elimination processes; enzyme-mimicking Au chemistry; cluster and surface reactions; and plasmonic catalysis. In the relevant sections, theoretical and computational studies of Au^I /Au^III chemistry are discussed and the predictions from the calculations are compared with the experimental observations to derive useful design strategies.