Synthesis of silica nanostructures by using wet-chemistry methods
Item
-
Title
-
Synthesis of silica nanostructures by using wet-chemistry methods
-
Identifier
-
d_2009_2013:a6481381c117:11708
-
identifier
-
12292
-
Creator
-
Zhang, Henan,
-
Contributor
-
Daniel L. Akins
-
Date
-
2013
-
Language
-
English
-
Publisher
-
City University of New York.
-
Subject
-
Chemistry | Inorganic chemistry | chemical etching | hollow | nanostructure | silica | surface tension
-
Abstract
-
For the sol-gel synthesis of silica particles under high pH catalytic conditions (pH>12) in water/ethanol solvent, we have deduced that the competing dynamics of chemical etching and sol-gel formation can explain the types of silica particles formed and their morphologies. We have demonstrated that emulsion droplets that are generated by adding tetraethyl orthosilicate (TEOS) to a water-ethanol solution serve as soft templates for hollow spherical silica (1∼2 microm). And if the emulsion is converted by the sol-gel process, one finds that suspended solid silica spheres of diameter of ∼900 nm are formed. Moreover, several other factors are found to play fundamental roles in determining the final morphologies of silica particles, such as by variation of the pH (in our case, using OH-) to a level where condensation dominates; by changing the volume ratios of water/ethanol; and using an emulsifier (specifically, CTAB).;For a sol-gel process occurring in a water/oil (w/o) system, the self-assembly of silica nuclei can be controlled by close control of synthesis conditions. We have synthesized ellipsoidal or spherical silica particles by a template-free scheme that involves controlling surface tension on silica nuclei through via use of different volume ratios of a w/o micellar system.;We have utilized wet-chemical etching of ellipsoidal silica nanoparticles to form silica nanoshells of a range of elliptical morphologies, with the thicknesses of the ellipsoidal silica nanoshells controlled through via variation of synthesis conditions. A mechanism has been proposed to explain how the nanoshells are formed, and we demonstrate that the porosity of the silica ellipsoid plays a role in generating silica shells. Moreover, silica materials with the unique structures might be adjusted to meet practical application requirements.
-
Type
-
dissertation
-
Source
-
2009_2013.csv
-
degree
-
Ph.D.
-
Program
-
Chemistry
