Remediation for Heavy Metal Contamination 281

16.3 Application of Nanomaterials for Detection of Heavy Metal

Contamination

16.3.1 Nano-sensors for Detection of Heavy Metals

Nanotechnology is a rapidly developing area that has the potential to provide a new generation

of technically advanced environmental sensing instruments and devices. Researchers are currently

focusing their attention on creating integrated sensing devices with a low-cost technology that can

identify susceptible contaminants even at trace levels. Depending on various signal transduction

methods, nanosensors are divided into optical, nanobiosensers, electrochemical and Field-Effect

Transistor (FET) sensors. The introduction of nanostructures and nanomaterials into sensors

significantly improves the selectivity, sensitivity, multiplexed detection capabilities and mobility of

the devices. In addition, inorganic materials have been combined with proteins, DNA, microbes and

small molecules to selectively link heavy metals as a probe for recognition at the molecular level

(Maghsoudi et al. 2021).

16.3.1.1 Optical Sensors

16.3.1.1.1 Fluorescent Sensors

The principle of fluorescence sensing is related to alterations in physicochemical characteristics

of fluorophores induced by analytes, measured through changes in the intensity of fluorescence,

anisotropy and lifetime, all of which are associated with transferring of energy mechanisms (Sauer

2003). Organic dyes, toolboxes and Graphene Oxide (GO) are commonly used as fluorophores

in Foerster Resonance Energy Transfer sensors (FRET) because of their commercial availability.

They are cheap and can be manufactured in large quantities. This battery-powered sensor had high

sensitivity (2 ppt) and selectivity for mercury (Hg²⁺) over lead (Pb²⁺) and copper (Cu²⁺) (Darbha

et al. 2007) (Table 16.2).

Table 16.2. Fluorescent nanosensors for detecting heavy metal ions.

Nanosensor

Strategy of sensing

Metals

References

CNPs

The fluorescence was reduced by successful

chelation of functions with metal ions

Pd²⁺ and

Hg²⁺

Sharma et al. 2016

GSH-Mn-ZnS

QDs LDH NCs

Intensity of luminescence is reduced by nonradiative

recombination

Pb²⁺, Cd³⁺,

and Hg²⁺

Liu et al. 2017

N-CQDs

Nonradiative transfer of electrons causes quenching

of fluorescence

Hg²⁺

Zhang and Chen 2014

S-GQDs

The fluorescence intensity was reduced when Fe⁺³

and S-GQDs functioned coordinately

Fe³⁺

Li et al. 2014

PPVs@MSN

@CdTe NCs

The chelation of CdTe QDs with Cu⁺² causes a

change in luminescence from red to green

Cu²⁺

Sha et al. 2015

16.3.1.1.2 Plasmonic Sensors

Surface plasmon resonance is caused by a group of free conduction electrons in a noble metal

resonating with incoming electromagnetic radiation (Li et al. 2012). This kind of sensor detects

analytes in a direct, visible and rapid manner by reducing expenses. Different heavy metals,

like Cu²⁺, As³⁺, Hg²⁺ and Pb²⁺, have been monitored using the colorimetric detection technique

(Chai et al. 2010).

16.3.1.1.3 Surface-enhanced Raman Scattering (SERS) Sensors

Although SERS sensors are widely utilized for chemical and biological sensing as well as medical

diagnostics (Li et al. 2013a), only a few studies confirmed detection of heavy metal (Mulvihill et

al. 2008, Han et al. 2010) (Table 16.3). A glutathione-based SERS sensor was developed for As³⁺