I. Combined cloud point extraction and Tween 20-stabilized gold
nanoparticles for colorimetric assay of silver nanoparticles in
environmental water
This study investigated a simple, sensitive and selective method for the colorimetric
assay of silver nanoparticles (AgNPs) using Triton X-114-based cloud point extraction
(CPE) as a preconcentration step and Tween 20-stabilized gold nanoparticles
(Tween-AuNPs) as a colorimetric probe. After heating beyond the cloud point
temperature of Triton X-114, a solution containing Triton X-114 micelles and AgNPs
separated into a surfactant-rich phase (small volume) and a dilute aqueous phase.
AgNPs partitioned into a Triton X-114-rich phase through a hydrophobic interaction
between Triton X-114 micelles and AgNPs. After phase separation, the concentrated
AgNPs oxidized to form Ag+ upon adding H2O2. The generated Ag+ triggered the
aggregation of Tween 20-AuNPs in a high-ionic-strength solution because the reduction
of Ag+ on the AuNP surface enabled Tween 20 (stabilizer) to be removed from the NP
surface. The efficiency of Triton X-114-based CPE of the AgNPs was found to be
iv
insensitive to their size and coating type. Under optimal extraction and detection
conditions, the selectivity of this method for AgNPs was considerably higher than for
other nanomaterials. The minimum detectable concentrations for 7, 22, and 54 nm
AgNPs were measured to be 0.1, 420, and 600 ng/mL, respectively. This method was
successfully applied to the analysis of 7 nm AgNPs in drinking water, tap water and
seawater.
Keyword: silver nanoparticles, gold nanoparticles, cloud point extraction, Tween-20,
colorimetric assay
II. Functionalized silver nanoparticles as an extracting and preconcentrating
agent for detection of mercury ions
In this research we provided highly sensitive and selective for fluorescence assay of
combined polythymine oligonucleotide (PolyT) with silver nanoparticles (AgNPs) as an
extracting agent to detect mercury ion in environmental water. According to previous
researches, PolyT will form a hairpin structure in the presence of Hg2+, this structure
provide several 3-D grooves that the fluorescent dye can inlay with it. SYBR Green I
(SG) is a staining dye for DNA, when binding with single strand DNA, it shows low
fluorescence. On the contrast, SG inlay with grooves of hairpin structure, it shows
v
11-fold of fluorescence signal. Hence, we used SG as a fluorescence probe for Hg2+. We
modified thiol group at the 5¡¦ of PolyT DNA, because of forming silver sulfur bond,
PolyT will able to modified on the surface of AgNPs. PolyT33SH-AgNPs are the
extracting and concentrating agent in Hg2+ solution, by the centrifugation, we collected
the PolyT33SH-AgNPs. For the purpose of releasing PolyT from AgNPs¡¦ surface, we
adding H2O2 to oxidize the AgNPs into Ag+. By mixing buffer and SG into previous
solution, mercury ion could be detected. In this study, we successfully detecting Hg2+
in the aqueous solution contained drinking water and tap water. The detection limit in
drinking water is 20 pM, which is below Environmental Protection Agency limit for
Hg2+ in drinkable water (10 nM), the linear range is from 50-600 pM. On the other hand,
the detection limit in tap water is 50 pM, linear range is from 100-700 pM.
Keyword: silver nanoparticles, mercury ion, PolyT, SYBR Green I, thymine
| Identifer | oai:union.ndltd.org:NSYSU/oai:NSYSU:etd-0709111-234005 |
| Date | 09 July 2011 |
| Creators | Wu, Zong-Han |
| Contributors | Shiuh Jen Jiang, Wei-Lung Tseng, Po-Yu Chen |
| Publisher | NSYSU |
| Source Sets | NSYSU Electronic Thesis and Dissertation Archive |
| Language | Cholon |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0709111-234005 |
| Rights | withheld, Copyright information available at source archive |
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