Surfaces and Interfaces of Liquid Metal Core–Shell Nanoparticles under the Microscope

Abstract

Eutectic gallium indium (EGaIn), a Ga‐based liquid metal alloy holds great promise for designing next‐generation core–shell nanoparticles (CSNs). A shearing‐assisted ligand‐stabilization method has shown promise as a synthetic method for these CSNs; however, determining the role of the ligand on stabilization demands an understanding of the surface chemistry of the ligand–nanoparticle interface. EGaIn CSNs are created and functionalized with aliphatic carboxylates of different chain length, allowing a fundamental investigation on ligand stabilization of EGaIn CSNs. Raman and diffuse reflectance Fourier transform spectroscopies (DRIFTS) confirm reaction of the ligand with the oxide shell of the EGaIn nanoparticles. Changing the length of the alkyl chain in the aliphatic carboxylates (C2–C18) may influence the size and structural stability of EGaIn CSNs, which is easily monitored using atomic force microscopy (AFM). No matter how large the carboxylate ligand, there is no obvious effect on the size of the EGaIn CSNs, except the particle size getting more uniform when coated with longer chain carboxylates. The AFM force–distance measurements are used to measure the stiffness of the carboxylate‐coated EGaIn CSNs. In corroboration with DRIFTS analysis, the stiffness studies show that the alkyl chains undergo conformational changes upon compression.

Analytical Methods for Characterization of Nanomaterial Surfaces

“…Foster and coworkers used AFM to study the role of the ligand on the size and stability of core−shell eutectic gallium indium (EGaIn) nanoparticles. 132 The EGaIn nanoparticles were protected by a carboxylic acid of varying alkyl chain length (C2−C18). The analysis by AFM showed large variation in particle size distribution except for C8 and C18, and the C2 sample showed a bimodal size distribution (Figure 9E(a)).…”

“…Foster and coworkers used AFM to study the role of the ligand on the size and stability of core–shell eutectic gallium indium (EGaIn) nanoparticles . The EGaIn nanoparticles were protected by a carboxylic acid of varying alkyl chain length (C2–C18).…”

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 ]…”

Transformable Gallium‐Based Liquid Metal Nanoparticles for Tumor Radiotherapy Sensitization

“…This process not only facilitates the control of particle size but also the formation of a core-shell structure. [27][28][29] Alg is a water-soluble natural polysaccharide with good biocompatibility and biodegradability, and thus, Alg is commonly used for drug and vaccine delivery. It can gradually degrade to water and carbon dioxide without delayed side effects in vivo.…”