2 research outputs found
Ultrathin Silica Membranes with Highly Ordered and Perpendicular Nanochannels for Precise and Fast Molecular Separation
Membranes with the ability of molecular/ionic separation offer potential in many processes ranging from molecular purification/sensing, to nanofluidics and to mimicking biological membranes. In this work, we report the preparation of a perforative free-standing ultrathin silica membrane consisting of straight and parallel nanochannels with a uniform size (βΌ2.3 nm) for precise and fast molecular separation. Due to its small and uniform channel size, the membrane exhibits a precise selectivity toward molecules based on size and charge, which can be tuned by ionic strength, pH or surface modification. Furthermore, the ultrasmall thickness (10β120 nm), vertically aligned channels, and high porosity (4.0 Γ 10<sup>12</sup> pores cm<sup>β2</sup>) give rise to a significantly high molecular transport rate. In addition, the membrane also displays excellent stability and can be consecutively reused for a month after washing or calcination. More importantly, the membrane fabrication is convenient, inexpensive, and does not rely on sophisticated facilities or conditions, providing potential applications in both separation science and micro/nanofluidic chip technologies
Highly Ordered Binary Assembly of Silica Mesochannels and Surfactant Micelles for Extraction and Electrochemical Analysis of Trace Nitroaromatic Explosives and Pesticides
The
rapid and sensitive detection of nitroaromatic compounds is of great
significance for human health, the environment, and public security.
The present work reports on the extraction and electrochemical analysis
of trace nitroaromatic compounds, such as explosives and organophosphate
pesticides (OPs), using the indium tin oxide (ITO) electrodes modified
with a highly ordered and aligned binary assembly of silica mesochannels
and micelles (BASMM). With a pore diameter of ca. 2β3 nm, silica
mesochannels (SMs) perpendicularly oriented to the ITO electrode surface
can provide hard and robust supports to confine the soft cylindrical
micelles formed by the aggregation of cationic surfactants, namely,
cetyltrimethylammonium bromide (CTAB). Due to the organized self-assembly
of hydrocarbon tails of CTAB surfactants, each micelle has a hydrophobic
core, which acts as an excellent adsorbent for rapid extraction and
preconcentration of trace nitroaromatic compounds from aqueous solutions
via the hydrophobic effect. Furthermore, the cylindrical micelles
are directly in contact with the underlying electrode surface, to
which extracted compounds can freely diffuse and then be reduced therein,
thus allowing their determination by means of voltammetry. Using the
BASMM/ITO sensor, electrochemical analysis of trace nitroaromatic
explosives, including 2,4,6-trinitrotoluene (TNT), 2,4,6-trinitrophenol,
2,6-dinitrotoluene, 3-nitrophenol, and nitrobenzene, and OPs, such
as paraoxon, methyl parathion, and fenitrothion, was achieved with
a fast response, wide linear range, high sensitivity, and low detection
limit at the ppb level. TNT and paraoxon in real apple, tea, and water
samples were also determined. By combining the heterogeneous extraction
and determination in one ordered binary nanostructure, the BASMM sensor
provides a very simple, rapid, and cost-effective way for analysis
of nitroaromatic compounds and can be extended to a wide range of
lipophilic yet redox-active analytes