Synthesis of Metal Nanostructures Using Supercritical Carbon Dioxide: A Green and Upscalable Process

Abstract

Metallic nanostructures have numerous applications as industrial catalysts and sensing platforms. Supercritical carbon dioxide (scCO2) is a green medium for the scalable preparation of nanomaterials. Supercritical fluid reactive deposition (SFRD) and other allied techniques can be employed for the mass production of metal nanostructures for various applications. The present article reviews the recent reports on the scCO2‐assisted preparation of zero‐valent metal nanomaterials and their applications. A brief description of the science of pure supercritical fluids, especially CO2, and the basics of binary mixtures composed of scCO2 and a low volatile substance, e.g., an organometallic precursor are presented. The benefits of using scCO2 for preparing metal nanomaterials, especially as a green solvent, are also being highlighted. The experimental conditions that are useful for the tuning of particle properties are reviewed thoroughly. The range of modifications to the classical SFRD methods and the variety of metallic nanomaterials that can be synthesized are reviewed and presented. Finally, the broad ranges of applications that are reported for the metallic nanomaterials that are synthesized using scCO2 are reviewed. A brief summary along with perspectives about future research directions is also presented.

Dióxido de Carbono Supercrítico: Uma Alternativa para uma Síntese Mais Sustentável

“…No caso particular da síntese de nanopartículas, especialmente nanopartículas metálicas, a capacidade extraordinária do CO 2 em conseguir penetrar e difundir--se por entre os poros dos materiais de partida, possibilita a deposição de nanopartículas com uma elevada dispersividade e controlo das propriedades morfológicas (ex. porosidade, densidade), algo que através das vias convencionais é muito difícil de conseguir controlar, garantindo uma boa reprodutibilidade [13][14][15].…”

Supercritical Fluid-Assisted Fabrication of Pd Nanoparticles/Graphene Using a Choline Chloride–Oxalic Acid Deep Eutectic Solvent for Enhancing the Electrochemical Oxidation of Glycerol

“…Thus, ChCl-oxalic acid DES was chosen as a solvent and a reducing agent to prepare the nanomaterials in this study. Compared to a traditional organic solvent, a supercritical fluid (SCF) is an attractive alternative for nanoparticle synthesis because such solvents are usually nontoxic, nonflammable, inexpensive, and easily separated. , The size and structures of nanoparticles can be readily controlled by utilizing the unique properties associated with such solvents in their supercritical state. When the substance reaches the supercritical state, the properties such as density, dielectric constant, and solubilizing capacity are drastically changed.…”

“…Supercritical carbon dioxide (scCO 2 ) is the most commonly used solvent because it is environmentally friendly, nonflammable, chemically inert, and relatively inexpensive. Moreover, many organometallic precursors with long alkyl chains that cannot typically be utilized in supercritical water (scH 2 O) or supercritical ethanol (scEtOH) can be solubilized in scCO 2 because the scCO 2 has a similar density to the liquid carbon dioxide, which retains equal solvation power. ,− Pd nanomaterials have proven to be excellent catalysts in many reactions, including organic coupling reactions, fuel cells, hydrogen storage, and sensing. Owing to the wide range of applications of this element, many techniques for the synthesis of Pd nanostructures have been developed, including deposition using a supercritical fluid.…”

Solute Diffusion into Polymer Swollen by Supercritical CO2 by High-Pressure Electron Paramagnetic Resonance Spectroscopy and Chromatography

“…Since pioneering reports by Berens [ 1 ] and Sand [ 2 ], the impregnation of polymers using supercritical fluids (SCFs) has remained of great interest in many applications, such as the loading of biocompatible materials with drugs [ 3 , 4 , 5 ] and food packaging materials with antioxidants, antimicrobials, etc. [ 6 , 7 ]; supercritical polymer dyeing [ 8 , 9 , 10 , 11 , 12 , 13 ]; fabrication of nanocomposites [ 14 , 15 , 16 , 17 ]; and polymer blends [ 18 , 19 , 20 ], just to name a few. SCFs make these approaches to polymer modification efficient and environmentally friendly.…”