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Bioremediation for Sustainable Environmental Cleanup

Table 16.3. SERS nanosensors for detecting heavy metal ions.

Nanosensor

Sensing strategy

Metals

References

AuNPs/rGO

colloid

The Pb²⁺ accelerated breakdown of AuNPs causes a reduction in

the Raman signal of graphene.

Pb²⁺

Zhao et al. 2016

AuNRs

Hg–Au production causes compositional and morphological

alterations in the NRs, resulting in blue shifts in the SPR peak.

Hg²⁺

Schopf et al. 2017

AgNPs

conjugates

Aggregation of AgNPs caused by glycine coordination with Hg²⁺

and Cu²⁺ resulted in higher Raman band intensity.

Cu²⁺ and

Hg²⁺

Li et al. 2013b

Flu-PBADiol-

Au@AgNPs

Raman signals are quenched attributable to the boronate ester

being cleaved by F.

F^–

Zhang et al. 2017

AuNPs

Anti aggregation related to autocatalytic action results in OPDA

oxidation to poly-OPDA or OPDAox by metal NPs.

Hg²⁺, Pb²⁺

and Cr⁴⁺

Patil et al. 2017

detection that can selectively bind to As³⁺ ions via the As-O link (Han et al. 2010). SERS provides

information on the existence of a chemical element as well as its chemical composition, which is

significant in metal ion toxicological studies since different heavy metals complexes have different

degrees of toxicity in humans and animals.

16.3.1.2 Nano Biosensing

Due to its vast potential for developing and fabricating future multifunctional nano sensing

systems, nanobiosensing is an emerging multidisciplinary research area that goes hand in hand with

biotechnology and molecular biology. This has made it easier to equip sensors with multiplexing

capabilities so that they can detect diverse analytes simultaneously.

(i) Aptasensors: Aptamer-based DNA sensors or aptasensors are a stable and extremely sensitive

technology because of their strong affinity to a wide range of binding sites. Single-stranded

DNA (ssDNA) or RNA molecules are known as aptamers. When compared to antibodies and

other biorecognition elements, they represent the next category of potential biorecognition

elements. These are usually utilized in manufacturing low-cost Hg²⁺ ion detection nanosensors

with an attached battery-powered visual reader connected to a smartphone’s existing camera

module.

(ii) DNA-nano sensors: The use of particular, pre-defined DNA sequences has been proposed

as a potential synthesis method for metal nanoparticles with a regulated shape and size. The

development of fluorescent nanoclusters is aided by both single-stranded DNA (ssDNA) (Petty

et al. 2004) and double-stranded DNA (dsDNA) (Rotaru et al. 2010) sequences. Mercury (Hg²⁺)

and Silver (Ag⁺) ions are detected using DNA nanosensors. Silver ions (Ag⁺) have a strong

affinity for cytosine-rich DNA; for this reason DNA nanosensors have been developed for

visual detection of Ag in tap water and river samples (Kumar and Guleria 2020). The affinity

of the thiamine rich oligonucleotide for Hg, which inhibits elongation of DNA, is applied in the

detection procedure of mercury (Hg²⁺) (Kumar and Guleria 2020).

16.3.1.3 Chemically Synthesized Nanomaterial-based Sensors

Electrochemical sensors have received a lot attention recently because of their characteristic ability to

provide label-free detection and are widely recognized for their sensitivity and mobility (Table 16.4).

Conducting wires are used to capture the electrochemical sensor signals. While heavy metals have

different redox potentials, bare electrodes without chemical detection probes are used to select specific

heavy metal ions. Voltammetry, conductometry, potentiometry, amperometry and impedemetry are

some of the transducing methods utilized in electrochemical sensing (Kimmel et al. 2012). Mercury-

based electrodes were first to be known for electrochemical detection of heavy metals (Varun and

Daniel 2018).