Precise preparation of highly monodisperse ZrO2@SiO2 core–shell nanoparticles with adjustable refractive indices

Abstract

This paper describes a straightforward method to precisely prepare monodisperse ZrO 2 @SiO 2 core-shell nanoparticles (CSNs) by sol-gel polymerization of TEOS in the presence of ZrO 2 cores without additional capping agents. We studied the morphology and composition of CSNs by Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and X-ray Diffraction (XRD). It has been found that the citric acid groups adsorbed onto the ZrO 2 surface during the preparation of ZrO 2 as well as the slow hydrolysis and condensation of TEOS in isopropanol are crucial for the selective growth of silica on the surface of ZrO 2 cores. The thickness of the silica shell can be facilely controlled from about 4 to 30 nm by varying the concentration of TEOS, with the refractive indices of the prepared CSNs tuned accordingly from about 1.2 to 1.9. The coated silica shell, which can be well dispersed in solvents such as methanol and ethanol, can improve the dispersibility of pure ZrO 2 nanoparticles which can only be dispersed in water. Moreover, the formation of the silica shell improved the chemical reactivity of pure ZrO 2 nanoparticles. After modifying with methyltriethoxysilane (MTES), the CSNs can be well dispersed in various organic solvents, such as dimethylbenzene, chloroform and isoamyl alcohol, which may find applications in optically transparent resins with controllable refractive index or organic silicon packaging materials with high refractive index for LED and so on. Additionally, other silane coupling agents can also be applied to modify the surface chemical properties of CSNs, which may provide more potential applications.

Morphology and properties of silica-based coatings with different functionalities for Fe3O4, ZnO and Al2O3 nanoparticles

“…2d shows the iron oxide nanoparticles coated under the same conditions with TEOS (yielding silica coatings (SiO 2 )). A thinner uniform silica coating was formed with a low ammonia concentration, whereas large aggregates were formed with a high ammonia concentration, which was consistent with the results obtained by Wu et al 22 and Yang et al 28 A four-fold increase in the silane concentration did not affect the coating thickness for the APTES, MTMS and OTES silanes (Fig. 2d).…”

Synthesis and thermal stability of ZrO2@SiO2 core–shell submicron particles

“…Such particles are of signicant interest for photonic applications in the visible range, such as structural colors, 19 and the design of optical materials with adjustable refractive index. 24 Furthermore, sol-gel derived zirconia particles exhibit a phase transition from the metastable tetragonal (t) phase to the monoclinic (m) phase upon thermal treatment. 35,36,[42][43][44] As this t / m transition is associated with a volume expansion of 5% (ref.…”

“…With increasing shell thickness some narrowing of the particle size distribution was observed, as reported previously. 23,24 Further, the HAADF-STEM images in Fig. 2(d)-(f) reveal that calcining the ZrO 2 @SiO 2 particles at 450 C for 3 h decreased the initial silica shell thicknesses to $10, $30, and $50 nm, respectively.…”

“…Silica coatings can be grown on various inorganic materials, including metals, 15,22 semiconductors, 12 and high band gap metal oxides. [23][24][25] Usually, the Stöber method is adapted to grow silica shells with well-controlled thickness. In general, silica encapsulation decreases the particles' initial polydispersity and surface roughness.…”

A Highly Controlled Organic–Inorganic Encapsulation Nanocomposite with Versatile Features toward Wearable Device Applications

“…[24][25][26] Expressing high RI, high strength, high toughness, and low photocatalysis, ZrO 2 is mainly used in the preparation of medical ceramics, [27] specialized steel, [28] optical glass, [29] and communication fibers. [30] Such multifaceted properties of ZrO 2 NPs have been exploited in conjunction with epoxy resin, [31] silicone resin [32] or acrylic resin as the encapsulation for the LED chip can reduce the light loss of LED [33] and the blue light ratio in the emission spectrum [34,35] for healthy lighting. [36] Most importantly, ZrO 2 as fillers has better moisture resistance and corrosion resistance under extreme conditions.…”