Noble Metal Nanomaterials with Nontraditional Crystal Structures

Abstract

<jats:p> Noble metals (Ru, Os, Rh, Ir, Pd, Pt, Ag, and Au) are known for their extraordinary oxidant-resistant behavior, good electrical and thermal conductivity, high work function, and brilliant luster. All occur in close-packed crystal structures: Ru and Os in hexagonal close-packed (hcp) and the rest in face-centered cubic (fcc) structures, both possessing high-symmetry structures and, therefore, a high degree of stabilization. Numerous studies in the literature have attempted to stabilize these metals away from their conventional crystal structures with the aim of realizing new properties. While obtaining conventional fcc metals in hcp structure or vice versa has been the subject of most studies, there are also examples of fcc metals crystallizing in lower-symmetry structures such as monoclinic. The nonnative crystal structures are generally realized during the crystallite growth itself, with a few exceptions in which a posttreatment was required for lattice transformation. In most cases, the new crystal structures pertain to the nanometer-length scale in the form of nanoparticles, nanoplates, nanoribbons, and nanowires, but there are good examples from microcrystallites as well. In this article, we review this active area of research, focusing on ambient stable crystal systems with some account of their interesting properties as reported in recent literature. </jats:p>

Noble Metal Nanomaterial-Based Biosensors for Electrochemical and Optical Detection of Viruses Causing Respiratory Illnesses

“…Noble metals are metallic elements (e.g., ruthenium, rhodium, palladium, platinum, gold, and silver) with outstanding resistance to high temperatures and chemical reactions (Hämäläinen et al, 2014 ; Sow et al, 2020 ). Noble metal nanomaterials have attracted scientific and technology research because of their small size (0.1–100 nm) and unique chemical and physical properties.…”

Изучение ГЦК-ОЦК фазового перехода в сплаве Au-Fe

“…Отметим, что изменение структуры наночастиц при уменьшении их размера было экспериментально обнаружено для многих однокомпонентных веществ и сплавов [33][34][35][36]. Например, в [33] было обнаружено, что при уменьшении размера наночастицы железа структура в ней изменяется из ОЦК-на ГЦК-структуру, которая стабильна для макрожелеза только при высоких температурах.…”

“…В [35] было экспериментально показано, что для сплава Au-Fe, подвергнутому ГЦК-ОЦК-переходу, высокотемпературная ГЦК-фаза имеет стабильный мелкий размер, меньший, чем ее низкотемпературная ОЦК-фаза. В обзоре [36] указаны экспериментальные работы, в которых были получены наночастицы Au, имеющие стабильные кристаллические структуры, которые были отличны от ГЦК-структуры.…”

Phase Control of Noble Monometallic and Alloy Nanomaterials by Chemical Reduction Methods

“…[10][11][12][13][14][15][16][17][18] In contrast, crystal structure control is not well developed compared with other parameters, although crystal structure, which describes the ordered arrangement of atoms in a solid, is the most powerful parameter in changing the physicochemical properties of materials. [19][20][21][22][23][24] Most bulk monometals and solid-solution alloys adopt one of the three simple structures, face-centered cubic (fcc), hexagonal close-packed (hcp), or body-centered cubic (bcc), and these structures depend on the elements and compositions. The phase diagrams of bulk metals show that some metals and alloys adopt a different structure at high temperatures.…”

“…Until now, several reviews about the crystal phase control of monometallic and alloy nanomaterials have been reported. [19][20][21][22][23][24] However, the mechanisms behind the syntheses, which are important for the further development of novel phasecontrolled metal nanomaterials, have not been well summarized and discussed. In this review, the recent development of the phase-controlled synthesis of monometallic and alloy nanomaterials with chemical reduction methods is introduced.…”