Route to Universally Tailorable Room-Temperature Liquid Metal Colloids via Phosphonic Acid Functionalization

Abstract

Eutectic gallium–indium nanoparticles (EGaIn NPs) were produced and subsequently functionalized with decylphosphonic acid under various conditions with the goal of producing highly stable room-temperature liquid metal colloids. Fourier transform infrared spectroscopy was used to determine phosphonic acid (PA) bonding modes (e.g., bidentate, tridentate) as a function of treatment conditions. The strongest bonding modes (i.e., predominantly tridentate) were found to take place under elevated temperature (reflux in hexanes), whereas lower bulk temperature processing such as bath or probe sonication produced largely weaker modes (bidentate). It is then shown that PA ligands can be chosen, which include click-chemistry reactive functionalities, opening up a universal route to chemically bespoke self-assembled monolayers on liquid metal colloids. These results carry important implications for robust functionalization of EGaIn NPs for use in inks, composites, and other materials.

Mechanoresponsive Polymerized Liquid Metal Networks

“…[28][29][30][31] Despite their impressive performance, these methods and materials suffer from at least one of the following limitations: low initial conductivity, low cyclic stability, low maximum strain, cumbersome fabrication, tenuous containment, and unwanted formation of metal oxide. [31][32][33] The oxide skin that spontaneously forms at the surface of liquid gallium alloys has been regarded as disadvantageous not only for its electrically insulating properties, but also because of its tendency to impart adhesion and non-Newtonian properties. [34] However, several examples have recently demonstrated beneficial uses of this oxide, including the stabilization of free-standing liquid metal structures [35] and the facile production of core-shell particles of liquid metal encapsulated by metal oxide through mechanical [36] or ultrasonic shearing.…”

“…[34] However, several examples have recently demonstrated beneficial uses of this oxide, including the stabilization of free-standing liquid metal structures [35] and the facile production of core-shell particles of liquid metal encapsulated by metal oxide through mechanical [36] or ultrasonic shearing. [33,37] Herein we introduce a material design strategy for a class of stretchable electronic materials which utilize the oxide shell of liquid gallium alloys to fabricate Polymerized Liquid Metal Networks (Poly-LMNs). These materials are composed of ligand-functionalized liquid metal particles connected through their oxide shells to form highly cross-linked particle-polymer networks consisting of >99 wt% liquid metal.…”

“…Control over both the surface energy and the mechanical properties of liquid metal coreshell particles has recently been demonstrated via straightforward chemical modification of their surface oxides. [32,38] Employing such modification, the current work utilizes a bifunctional ligand (11phosphonoundecylacrylate) chosen for its ability to covalently bind metal oxides through its phosphonic acid head group [33] while presenting a readily polymerizable acrylate tail group. Reactive eutectic gallium indium (EGaIn) particles were fabricated via bath sonication in the presence of excess ligand, yielding particles with average diameters on the order of 3 µm (Supplementary Figure S1).…”

Surface modification of liquid metal as an effective approach for deformable electronics and energy devices

“…This is because the ligands are chemisorbed with strong binding to the metal oxide surface. 31,32,[70][71][72][73] Likewise, when the bulk liquid metal was conducted using an ultrasonic process in a solvent containing molecules that have organo-phosphates or carboxylates, the oxide layer on the liquid metal particles (Ga 2 O 3 ) has strong binding with the phosphate group or carboxylic acid group 15,28,30,74 (Fig. 3(b) and (c)).…”

Nano‐Biomedicine based on Liquid Metal Particles and Allied Materials

“…To realize the applications in flexible electronics and biomedicine, nanoparticles with improved performances in yields, stability, small sizes, uniform distribution, and high purity are favored. Many solutions are proposed, including development of dynamic temperature control system, [ 95 ] screening of novel macromolecules, or ligands, such as brushed polyethylene glycol (bPEG), [ 96 ] aliphatic carboxylates with different chain lengths, [ 97 ] phosphonic acids, [ 98 ] alkoxysilane ligands, [ 99 ] and comb‐like polymers. [ 100 ]…”