Synthetic Routes and Formation Mechanisms of Spherical Boron Nitride Nanoparticles

Abstract

A new concept is proposed to explain the formation of spherical boron nitride (BN) nanoparticles synthesized by the chemical vapor deposition (CVD) reaction of trimethoxyborane (B(OMe)3) with ammonia. The intermediate phases formed during the CVD under different reaction conditions are analyzed by X‐ray diffraction, electron microscopy, thermogravimetry, and spectroscopy techniques. The transition mechanism from an intermediate B(OMe)3–xH3–xN (x < 2) phase having single BN bonds to the BN nanoparticles is elucidated. This particularly emphasizes the CVD temperature effect governing the conversion of the NH···OB hydrogen bonds in (OMe)3B · NH3 into the NB bonds in B(OMe)3–xH3–xN. The spherical morphology strongly depends on the remnant impurity oxygen formed upon Me2O group elimination in the intermediate. Two types of spherical BN nanoparticles primarily attractive for immediate commercialization (with C and H impurities at a level less than 1 wt %) are synthesized by the adjustment of experimental parameters: high oxygen‐containing (∼6.3 wt %) BN spheres with a diameter of ∼90 nm and a specific surface area of 26.8 m2 g−1; and low oxygen‐containing (<1 wt %) BN spheres with a diameter of ∼30 nm and a surface area of 52.7 m2 g−1. Finally, the regarded synthetic techniques are fully optimized in the present work.

Chitosan-coated boron nitride nanospheres enhance delivery of CpG oligodeoxynucleotides and induction of cytokines

“…39 The BNNS spectrum showed a strong band at around 1400 cm -1 , along with a less intense band at 780 cm -1 , which are assigned to the (B-N) and (B-N-B) vibrations, respectively. 37 These data show that the BNNS-CS complexes clearly have the peak characteristic of both BNNS and chitosan, and demonstrate the presence of chitosan in the BNNS-CS complexes, thereby confirming the success of coating. Therefore, we conclude that the negatively charged CpG oligodeoxynucleotides were able to bind electrostatically to positively charged BNNS-CS complexes.…”

“…37 They were spherical in shape, and the average size was approximately 150 nm ( Figure 2). To obtain a positively charged surface and facilitate attachment of CpG oligodeoxynucleotides onto BNNS, we used chitosan to modify the charge of the BNNS because, to our knowledge, chitosan is the only biodegradable and biocompatible cationic polysaccharide.…”

“…37 Chitosans with a molecular mass of 60-120 kDa (CS-L), 110-150 kDa (CS-M), and 140-220 kDa (CS-H) were purchased from Sigma-Aldrich (St Louis, MO, USA) and dissolved in 1% acetic acid to a concentration of 5 mg/mL. A working solution was prepared by diluting these stocks with Milli-Q water ( Millipore, Bedford, MA, USA).…”

Polyethyleneimine-functionalized boron nitride nanospheres as efficient carriers for enhancing the immunostimulatory effect of CpG oligodeoxynucleotides

“…35 The as-prepared BNNS showed a uniform spherical shape with an average diameter of approximately 150 nm (Figure 2A). In addition, well-ordered channels were clearly observed from the high-resolution transmission electron micrograph of the BNNS ( Figure 2B).…”

“…35 PEI was diluted with Milli-Q water to a concentration of 10% (v/v) prior to use. Working solutions were prepared from the stock by dilution with Milli-Q water.…”