Binding of Alkenes and Ionic Liquids to B–H-Functionalized Boron Nanoparticles: Creation of Particles with Controlled Dispersibility and Minimal Surface Oxidation

Abstract

The interaction of B-H-functionalized boron nanoparticles with alkenes and nitrogen-rich ionic liquids (ILs) is investigated by a combination of X-ray photoelectron spectroscopy, FTIR spectroscopy, dynamic light scattering, thermogravimetric analysis, and helium ion microscopy. Surface B-H bonds are shown to react with terminal alkenes to produce alkyl-functionalized boron particles. The interaction of nitrogen-rich ILs with the particles appears, instead, to be dominated by boron-nitrogen bonding, even for an ILs with terminal alkene functionality. This chemistry provides a convenient approach to producing and capping boron nanoparticles with a protective organic layer, which is shown to protect the particles from oxidation during air exposure. By controlling the capping group, particles with high dispersibility in nonpolar or polar liquids can be produced. For the particles capped with ILs, the effect of particle loading on hypergolic ignition of the ILs is reported.

Experimental synthesis, functionalized modifications and potential applications of monoelemental zero-dimensional boron nanomaterials

“…With regard to the top-down synthesis approach, mechanical milling is extensively employed to prepare 0D boron nanomaterials. 68,69,[71][72][73][74][75][77][78][79][80]82,85,89 Mechanical milling is divided into different types, including dry ball milling, neat ionic-liquid (IL) milling, solvent milling, sonication-assisted milling, articial and machine grinding. The operation of mechanical milling is oen continuously conducted for a few, several and even dozens of hours at low temperature or room temperature (RT).…”

“…The milling process can be articially ground, or performed with a machine under xed rotation speeds, such as 300 rpm. 69,78 Milling rate and time of articial grinding are freely regulated, while those of machine milling are required to set a xed rotation rate and time, and the time to pause for machine resting. Except for IL, 68,69 other surface capping ligand molecules of 0D boron nanomaterials have been utilized during the solvent milling process, such as oleic acid, 72,73 poly(ethylene glycol) (PEG), 77 undecylenic acid (UND), 80 dopamine (DA), 80 and poly(vinyl pyrrolidone) (PVP).…”

“…69,78 Milling rate and time of articial grinding are freely regulated, while those of machine milling are required to set a xed rotation rate and time, and the time to pause for machine resting. Except for IL, 68,69 other surface capping ligand molecules of 0D boron nanomaterials have been utilized during the solvent milling process, such as oleic acid, 72,73 poly(ethylene glycol) (PEG), 77 undecylenic acid (UND), 80 dopamine (DA), 80 and poly(vinyl pyrrolidone) (PVP). 81 Sonication (700 W) in advance or aerwards at a low (5 C) temperature or RT is necessary for ball milling, which ensures a high dispersion of boron resource precursors or the produced 0D boron in the solvent.…”

“…As summarized in Table 1, the widely used surface capping ligand molecules during the synthesis process mainly refer to IL, PEG, PVP, oleic acid, undecylenic acid and dopamine. 68,69,72,73,77,80,81,127,128 Perez et al reported the synthesis of BNPs through the boron milling process. 128 Boron powder was dry-milled with tungsten carbide balls under an Ar atmosphere.…”

Borane–Aluminum Surface Interactions: Enhanced Fracturing and Generation of Boron–Aluminum Core–Shell Nanoparticles

“…Oleic acid (OA) binds well to both boron 32 and aluminum 14 nanoparticles and was found to impart reasonable dispersibility to the diborane-milled particles. Alkenes react with B−H-terminated boron nanoparticle surfaces, 18 and because mass spectrometry suggested ( Figure 1) that the borane-milled aluminum particles had both B and H in the surface layer, we also tried capping the particles by milling a sample of diborane-milled particles with 1-octene, using WC balls and a milling speed of either 100 or 300 rpm. Particles milled at 100 rpm with octene were actually less hexanes-dispersible than uncapped particles, forming clumps within 1 min; however, the sample produced by milling with octene at 300 rpm was highly dispersible in hexanes.…”