distinct advantage that a reference electrode is not required for operation, unlike
many other types of ion sensors. Asadnia et al. showed that such devices coated
with plasticised poly(vinyl chloride) based membranes containing an ionophore can
be used to detect Hg
2+ [5] and Ca
2+ [6] ions in water.
5 Nanoparticles in Environmental Monitoring
Owing to their unique physicochemical characteristics and vast applications, currently, metal nanoparticles have attracted a great deal of attention. Metal
nanoparticles exhibit properties such as ultra-small size, strong fluorescence and
low toxicity. These are considered as a kind of novel fluorescence probe for the
development of optical sensors. Nanoparticles possess a broad range of application
in the field of environmental, pharmaceutical, cosmetics, energy, optoelectronic and
catalytic. Recently, in the field of environmental monitoring nanoparticles have
been widely applied for the analysis of toxins, metal ions, and organic pollutants.
Water and wastewater treatment approach using nanoparticles have gained
increasing attention owing to their specific properties such as large surface area,
antimicrobial activity [31], photocatalytic activity [35], and chemical stability [96].
In addition to this, they also possess potential application in environmental monitoring. Nanoparticles provide with advantages as nanosensors in rapid and
high-output detection technique. Extremely small size and exceptional nanoscale
properties make nanoparticles useful for the new-generation environmental monitoring. The recent progress in their applications in environmental monitoring,
involves pH sensing, the detection of heavy metals and inorganic anions.
The main reason behind the pH sensing ability of metal nanoparticle is its
response characteristics towards pH. It was recently reported by Wang et al. [87,
88] and Chen et al. [18] that copper and gold/copper nanoparticles could be
effectively used as reversible fluorescence indicators for pH sensing The response
behaviours for the pH change were opposite to that of reported by Qu et al. [67].
Results showed that the fluorescence signal was gradually declined with the
increase in pH value.
Ecological pollution by heavy metal is a great matter of concern worldwide.
Heavy metals when present in high concentration can pose adverse effects on the
receiving ecosystem as well as on human health. This highlights the importance of
heavy metal ion monitoring of the environment. For serving this purpose a large
number of selective heavy metal ion sensors have been developed from nanoparticles. Darbha et al. [26] reported a gold nanoparticles-based sensor for the easy,
rapid and reliable screening of Hg
2+ ions in aqueous solutions, with a sensitivity
of 5 ng/ml (ppb). Yang et al. [92] demonstrated visual detection of Cu
2+ by
L-cysteine-functionalized gold nanoparticles in aqueous solution. In the presence of
Cu
2+ , the gold nanoparticles solution changed from red to blue. This colorimetric
nanosensor allows rapid, quantitative detection of Cu
2+ with a sensitivity of 105 M.
Peng et al. [64] developed a fluorescent-based microfluidic chip using magnetic
Materials in Emerging Water Pollutants Detection
261
many other types of ion sensors. Asadnia et al. showed that such devices coated
with plasticised poly(vinyl chloride) based membranes containing an ionophore can
be used to detect Hg
2+ [5] and Ca
2+ [6] ions in water.
5 Nanoparticles in Environmental Monitoring
Owing to their unique physicochemical characteristics and vast applications, currently, metal nanoparticles have attracted a great deal of attention. Metal
nanoparticles exhibit properties such as ultra-small size, strong fluorescence and
low toxicity. These are considered as a kind of novel fluorescence probe for the
development of optical sensors. Nanoparticles possess a broad range of application
in the field of environmental, pharmaceutical, cosmetics, energy, optoelectronic and
catalytic. Recently, in the field of environmental monitoring nanoparticles have
been widely applied for the analysis of toxins, metal ions, and organic pollutants.
Water and wastewater treatment approach using nanoparticles have gained
increasing attention owing to their specific properties such as large surface area,
antimicrobial activity [31], photocatalytic activity [35], and chemical stability [96].
In addition to this, they also possess potential application in environmental monitoring. Nanoparticles provide with advantages as nanosensors in rapid and
high-output detection technique. Extremely small size and exceptional nanoscale
properties make nanoparticles useful for the new-generation environmental monitoring. The recent progress in their applications in environmental monitoring,
involves pH sensing, the detection of heavy metals and inorganic anions.
The main reason behind the pH sensing ability of metal nanoparticle is its
response characteristics towards pH. It was recently reported by Wang et al. [87,
88] and Chen et al. [18] that copper and gold/copper nanoparticles could be
effectively used as reversible fluorescence indicators for pH sensing The response
behaviours for the pH change were opposite to that of reported by Qu et al. [67].
Results showed that the fluorescence signal was gradually declined with the
increase in pH value.
Ecological pollution by heavy metal is a great matter of concern worldwide.
Heavy metals when present in high concentration can pose adverse effects on the
receiving ecosystem as well as on human health. This highlights the importance of
heavy metal ion monitoring of the environment. For serving this purpose a large
number of selective heavy metal ion sensors have been developed from nanoparticles. Darbha et al. [26] reported a gold nanoparticles-based sensor for the easy,
rapid and reliable screening of Hg
2+ ions in aqueous solutions, with a sensitivity
of 5 ng/ml (ppb). Yang et al. [92] demonstrated visual detection of Cu
2+ by
L-cysteine-functionalized gold nanoparticles in aqueous solution. In the presence of
Cu
2+ , the gold nanoparticles solution changed from red to blue. This colorimetric
nanosensor allows rapid, quantitative detection of Cu
2+ with a sensitivity of 105 M.
Peng et al. [64] developed a fluorescent-based microfluidic chip using magnetic
Materials in Emerging Water Pollutants Detection
261