One-Pot Syntheses of Porous Hollow Silica Nanoreactors Encapsulating Rare Earth Oxide Nanoparticles for Methylene Blue Degradation

Abstract

In this study, a one-pot method for preparing porous hollow silica nanospheres (PHSNs) encapsulating rare earth metal oxide nanoparticles (NPs) is reported. The synthetic route employs charge-driven micelles as templates, which consists of negatively charged complex chains of bis-ligand-bound rare earth metal ions and positively charged diblock copolymer. By deposition of silica onto the micellar coronas and subsequent calcination, a series of M x O y @PHSNs (M = La, Ce, Eu, and Gd) were synthesized. The relevant characterizations confirm that these nanostructures consist of ∼30 nm hollow silica nanospheres and small-sized metal oxide NPs inside ∼12 nm cavities. Degradations of methylene blue and new coccine with H2O2 over M x O y @PHSNs reveal that the Ce x O y NP integrated PHSNs show the best catalytic properties among these M x O y @PHSNs, and incorporation of Cu x O y with Ce x O y further increases the activity for methylene blue degradation.

Coordination-Enhanced Synthesis for Hollow Mesoporous Silica Nanoreactors

“…Current synthetic methods for HMNs with NPs inside their cavities use target NPs as templates to deposit the desired nanosphere materials in microemulsion systems, ,− postsynthesis to load NPs inside presynthesized hollow nanospheres, ,,, or hard-templating methods including nanocasting, sacrificial templating such as Galvanic replacement and Kirkendall effect, shell formation by adsorption, , layer-by-layer deposition, and chemical deposition . Recently, a method, using metal ions containing charge-driven micelles as templates onto which silica is deposited, has been developed from our previous work to synthesize a series of metal-oxide NPs-encaged hollow mesoporous silica nanoreactors (M x O y @HMSNs). , Double ligands (L 2 EO 4 ), two dipicolinic acid ligands connected by a tetraethyleneoxide spacer, − were used to coordinate metal ions and further combine with a quaterized copolymer to form micelles by electrostatic attraction. However, the developed method is only applicable to transition- or rare-earth-metal systems and it has difficulties in incorporating noble, main group, and bimetallic NPs inside nanoreactors.…”

“…38 Recently, a method, using metal ions containing charge-driven micelles as templates onto which silica is deposited, has been developed from our previous work to synthesize a series of metal-oxide NPs-encaged hollow mesoporous silica nanoreactors (M x O y @HMSNs). 39,40 Double ligands (L 2 EO 4 ), two dipicolinic acid ligands connected by a tetraethyleneoxide spacer, 41−45 were used to coordinate metal ions and further combine with a quaterized copolymer to form micelles by electrostatic attraction. However, the developed method is only applicable to transition-or rare-earth-metal systems and it has difficulties in incorporating noble, main group, and bimetallic NPs inside nanoreactors.…”

Controlled Synthesis of Manganese Oxide Nanoparticles Encaged in Hollow Mesoporous Silica Nanoreactors and Their Enhanced Dye Degradation Activity

“…Although L 3 molecules are fully deprotonated at such a high pH value of 8.5, most Mn ions precipitate as metal hydroxides, prohibiting the formation of Mn ion bound micelles. The suitable pH range for the formation of metal ion-containing polymer micelles by triple ligands is wider than that by double ligands , because triple ligands can form coordination complex networks, which further increases the coordination stability between L 3 and metal ions, resulting in a wider pH range for micelles formation.…”

“…The influences of synthetic parameters on their structures and reaction conditions on dye degradations are also studied in this work. In the synthesis, triple ligands instead of our previous reported double ligands , are used to coordinate Mn ions to form negatively charged coordination complex networks, and the resulting negatively charged complex networks further combine with positively charged quaternized poly­(2-vinylpyridine)- b -poly­(ethylene oxide) (P2MVP 128 - b -PEO 477 ) copolymers to form metal ion bound polymer micelles. After silica deposition onto micellar coronas and subsequent calcination, HMSNs (∼30 nm) with ∼1.6 nm Mn x O y NPs inside their cavities (∼15 nm) are obtained.…”

Spherical Polyelectrolyte Brushes as Templates to Prepare Hollow Silica Spheres Encapsulating Metal Nanoparticles

“…Recently, Li et al prepared hollow mesoporous silica nanoreactors with small-size metal oxide nanoparticles by deposition of silica onto metal-containing charge-driven polymer micelles and subsequent calcination [16,24]. This method simultaneously forms hollow silica spheres and metal oxide nanoparticles in cavities, which is general for the preparation of hollow silica nanoparticles with metal oxide nanoparticles.…”