multi-walled carbon nanotubes for tracing small amounts of Cr(III) and Cr(VI) in
various water samples, with a detection limit of 0.094 nM. An in situ preparation
technique was reported by Chen et al. (2004) for gold nanoparticles in poly(Nisopropylacrylamide) gels. The thus obtained gold nanoparticles/poly(N-isopropylacrylamide gels offered similar optical properties as of the bare gold
nanoparticles. Only 9% increase in its fluorescence intensity was observed in the
presence of 500 mM NaCl, supporting its characteristics of good salinity resistance.
For the detection of Hg
2+ in samples, the sensing approach was successfully
applied. The developed gold nanoparticles/poly(N-isopropylacrylamide) gels was
observed to possess good thermosensitive properties and showed possibility to be
also applied and designed as a temperature sensor relied on the change in the
fluorescence intensity. Xie et al. [89] reported a selective and sensitive approach for
Hg
2+ sensing using Bovine serum albumin (BSA) templated gold nanoparticles.
There was about 17% gold on the surface of BSA-Au, the red fluorescence of
Bovine serum albumin (BSA) templated gold nanoparticles was quenched by the
unique metal affinity between Hg
2+ and Au
+ in a few seconds. A method for in situ
synthesis of fluorescent gold nanoparticles on bovine serum albumin/poly(ethyleneoxide) (PEO) electrospun membrane was reported by Cai et al. [13], and it was
applied in the detection of Hg
2+ . On the surface of BSA/PEO fibrous membrane
nanoparticles were immobilized and emitted bright red fluorescence under visible
light irradiation. A rapid quenching of the red fluorescence signal was carried out
by Hg
2+ due to the relatively large specific surface of nanofibers and strong affinity
between Hg
2+ and Au
+
. Guo et al. [39] reported that denatured bovine serum
albumin-Ag nanocatalyst could be assembled as a chemical sensing material for the
detection of Hg
2+ . Recently, Wang et al. [87, 88] demonstrated a novel fluorescence
enhancement technique for the determination of Hg
2+ using carbon nanotubes and
DNA-Ag nanocatalysts. For the determination of copper ions, an electrochemical
sensor possessing a limit of detection below 1 pM was developed. Modification of
electrodes were first carried out using gold nanoparticles, followed by modification
of gold colloid surface with cysteine for the detection of copper. For the detection
of Hg
2+ and Ag
+
, Freeman et al. [33] developed and reported a multiplex assay
using an electron-transfer-quenching route. Modifications of quantum dots of different sizes were carried out with thymine or cytosine bases. The formation of T–T
and C–C base pairs was induced by Hg
2+ /Ag
+ ions. Development of several optical
sensors has been carried out based on photoluminescent-quenching principles.
A gold nanoparticle–rhodamine 6G-based fluorescent sensor ave been reported by
Chen et al. [20, 21] for the detection of Hg
2+ in aqueous solution with a lower
detection limit of 0.012 ppb. Similar assays involved monitoring photoluminescent
intensity before and after Hg
2+ addition, with photoluminescence increasing with
increasing Hg
2+ . However, this assay was sensitive only to 2.0 ppb [43]. He et al.
[41] also demonstrated a homogeneous assay to detect Cu
2+ , based on modulating
photoluminescent-quenching efficiency between a perylene bisimide chromophore
and gold nanoparticles in the presence of Cu
2+ .
Cyanide, a highly toxic ion, inhibits the cytochrome C oxidase activity in
mitochondria and obstructs respiration in cells. Recently, gold nanoparticles have
262
R. Khan et al.
various water samples, with a detection limit of 0.094 nM. An in situ preparation
technique was reported by Chen et al. (2004) for gold nanoparticles in poly(Nisopropylacrylamide) gels. The thus obtained gold nanoparticles/poly(N-isopropylacrylamide gels offered similar optical properties as of the bare gold
nanoparticles. Only 9% increase in its fluorescence intensity was observed in the
presence of 500 mM NaCl, supporting its characteristics of good salinity resistance.
For the detection of Hg
2+ in samples, the sensing approach was successfully
applied. The developed gold nanoparticles/poly(N-isopropylacrylamide) gels was
observed to possess good thermosensitive properties and showed possibility to be
also applied and designed as a temperature sensor relied on the change in the
fluorescence intensity. Xie et al. [89] reported a selective and sensitive approach for
Hg
2+ sensing using Bovine serum albumin (BSA) templated gold nanoparticles.
There was about 17% gold on the surface of BSA-Au, the red fluorescence of
Bovine serum albumin (BSA) templated gold nanoparticles was quenched by the
unique metal affinity between Hg
2+ and Au
+ in a few seconds. A method for in situ
synthesis of fluorescent gold nanoparticles on bovine serum albumin/poly(ethyleneoxide) (PEO) electrospun membrane was reported by Cai et al. [13], and it was
applied in the detection of Hg
2+ . On the surface of BSA/PEO fibrous membrane
nanoparticles were immobilized and emitted bright red fluorescence under visible
light irradiation. A rapid quenching of the red fluorescence signal was carried out
by Hg
2+ due to the relatively large specific surface of nanofibers and strong affinity
between Hg
2+ and Au
+
. Guo et al. [39] reported that denatured bovine serum
albumin-Ag nanocatalyst could be assembled as a chemical sensing material for the
detection of Hg
2+ . Recently, Wang et al. [87, 88] demonstrated a novel fluorescence
enhancement technique for the determination of Hg
2+ using carbon nanotubes and
DNA-Ag nanocatalysts. For the determination of copper ions, an electrochemical
sensor possessing a limit of detection below 1 pM was developed. Modification of
electrodes were first carried out using gold nanoparticles, followed by modification
of gold colloid surface with cysteine for the detection of copper. For the detection
of Hg
2+ and Ag
+
, Freeman et al. [33] developed and reported a multiplex assay
using an electron-transfer-quenching route. Modifications of quantum dots of different sizes were carried out with thymine or cytosine bases. The formation of T–T
and C–C base pairs was induced by Hg
2+ /Ag
+ ions. Development of several optical
sensors has been carried out based on photoluminescent-quenching principles.
A gold nanoparticle–rhodamine 6G-based fluorescent sensor ave been reported by
Chen et al. [20, 21] for the detection of Hg
2+ in aqueous solution with a lower
detection limit of 0.012 ppb. Similar assays involved monitoring photoluminescent
intensity before and after Hg
2+ addition, with photoluminescence increasing with
increasing Hg
2+ . However, this assay was sensitive only to 2.0 ppb [43]. He et al.
[41] also demonstrated a homogeneous assay to detect Cu
2+ , based on modulating
photoluminescent-quenching efficiency between a perylene bisimide chromophore
and gold nanoparticles in the presence of Cu
2+ .
Cyanide, a highly toxic ion, inhibits the cytochrome C oxidase activity in
mitochondria and obstructs respiration in cells. Recently, gold nanoparticles have
262
R. Khan et al.