A Self-Templated Route to Hollow Silica Microspheres

Abstract

A simple, mild, and effective self-templated approach has been developed to directly convert solid SiO2 microspheres into hollow structures. The reaction involves initial partial dissolution of silica cores in a NaBH4 solution and subsequent shell formation due to the redeposition of the silicate species back onto the colloid surfaces. The increasing concentration of NaBO2 as the result of the slow decomposition of NaBH4 in water is found to be responsible for the regrowth of the silica shell. This method allows the production of hollow silica spheres with sizes ranging from ∼70 nanometers to several micrometers, largely determined by the size of the starting silica colloids. The solid-to-hollow transformation mechanism is investigated in detail by transmission electron microscopy (TEM), scanning electron microscopy (SEM), Fourier Transform Infrared (FTIR) spectrometry, X-ray absorption spectroscopy (XAS), N2 adsorption−desorption, and X-ray diffraction (XRD). We also study the reaction conditions that allow control over the wall thickness, surface morphology, and shell porosity.

The Development of a Highly Sensitive Fiber-Optic Oxygen Sensor

“…The relative fluorescence intensity of the Pd(II)-doped oxygen sensor with porous silica nanoparticles drops rapidly when oxygen concentration changes from 0%-20%, and it is clear that this sensor has high sensitivity. It also has better oxygen diffusivity and surface-area-to-volume ratio than the composite xerogel because the porous silica nanoparticles have large surface areas [21][22][23][24]. This high surface-area-to-volume ratio has the potential of providing very high sensitivity in optical sensing applications.…”

“…In this study, we have chosen a Pd(II) complex (PdTFPP). Recently, the important properties of porous silica nanostructures have been receiving much research attention, especially for biology, catalysis, health sciences, and many industrial applications [21][22][23][24]. Because a high surface-to-volume ratio is an important property for optical oxygen sensors, our lab presents a highly sensitive optical oxygen sensor based on the tris(4,7-diphenyl-1,10-phenanthroline)ruthenium(II) ([Ru(dpp) 3 ] 2+ ) and porous silica nanoparticles embedded in a TEOS/Octyl-triEOS composite xerogel.…”

Covalent combination of polyoxometalate and graphitic carbon nitride for light-driven hydrogen peroxide production

“…All solvents used were of analytical grade and were purchased from Fisher. Closepacked silica nanospheres [18] and K 7 [PW 11 O 39 ]·13H 2 O (K-PW 11 ) [19a] were synthesized and characterized in accordance with the literature.…”

Fabrication of Polyaniline: Nail/Spindle‐Shaped Morphology

“…[13] When SDS is used as the dispersing agent, the dispersity of the aniline oligomers can be enhanced but some aggregated granules are still observed, [17] as shown in Figure 1c and 1d (Run 2). However, when PVP was used to stabilize aniline, both round plates and nail/spindle structures were observed (Figure 1e and 1f, Run 4), suggesting the efficient dispersity of the PANI through hydrogen bonding interactions between the carbonyl groups of the PVP and the amino groups of the aniline, [18] which avails the further self-assembly of the PANI.…”

“…These insoluble phenazine-like planar molecules then deposit from the water and stack together, [13,14] to assemble into micrometer-sized, round, plate-like crystal templates with spiral dislocations in the presence of APS. [16] Amino groups located at the plate surfaces then interact with the PVP molecules through hydrogen bonding [18] to ensure the uniformity and dispersity of these plates. In stage II (10 to 30 min), the pH value in the system quickly decreases below 4.0 due to the continuous release of hydrogen ions by the PANI oligomers, and then anilinium cations become the primary reactants.…”