detecting mercury (II) ions and has low toxicity too. Li et al. [94] monitored cerium
(III) using a color-evolution based paper sensor by incorporating fluorescent
nanoprobe (carbon dots) onto the cellulose paper substrate. Ramírez et al. [95]
quantified lead (II) by developing an electrochemical affinity biosensor that combines glassy carbon electrodes and an aqueous dispersion of single-walled carbon
nanotubes covalently modified with cysteine residues. The sensor demonstrated
high selectivity for lead in complex solutions. Dong et al. [96] reported a simple
and green sensing system for the detection of free residual chlorine in water based
on fluoroscence quenching of Graphene quantum dots. In the work done by [97] an
“on-off” fluorescence phosphorus/nitrogen dual-doped carbon quantum dots probe
was developed for the determination of Chromium (VI). Liu et al. [98] reported a
simple and effective way to fabricate a ratiometric fluorescence sensor based on
dual-emission carbon dots-gold nanoclusters functionalized with dithiothreitol for
detecting mercury ions in water samples. Tang et al. [99] developed an electrochemical sensor by combining DNAzyme with quantum dots to detect lead with a
limit of detection of 7.8 pM. Yang et al. [100] combined reduced graphene oxide
and gold nanoparticles for detection of organophosphate paraoxon-ethyl with a
detection limit of 0.5 nM. Cui et al. [101] developed electrochemical acetylcholinesterase biosensor for detection of organophosphorus based pesticides by
using adsorption properties of titanium oxide sol-gel, chitosan and reduced
graphene oxide based multi-layered immobilization matrix. Nie et al. [102] proposed label-free aptamer surface-enhanced Raman scattering sensor for detection
of trace malathion residue; silver nanoparticles were modified with positively
charged spermine which served as capture reagents for the aptamer. Yang et al.
[103] labelled a specific antibody against E. coli O157: H7 using carboxyl functionalized graphene quantum dots and generated a strong fluorescent signal with the
detection limit of 100 cfu/mL as minimum. Parimaladevi et al. [104] designed a
sensor using a graphene boosted silver nanoparticles platform through surface
enhanced Raman scattering technique which was able to detect the toxic components in real textile effluent. Parvathi et al. [105] reported another sensor for textile
effluents based on graphene oxide mediated surface enhanced Raman scattering on
gold/reduced-graphene oxide nanocomposites. Chen et al. [106] developed
reduced graphene oxide-modified electrodes toward electroanalytical determination
of sulfamethoxazole in aqueous environments. Wong et al. [107] simultaneously
determined three drugs: terbutaline, nimesulide, and methocarbamol by designing a
composite electrode based on graphite oxide-polyurethane modified with
beta-cyclodextrin.
5.5 Future Trends and Recommendations
Research shows that nanomaterials-based sensors have shown promising results
with enhanced sensitivity and response time. Unique properties of nanomaterials
like size-tunable and shape-dependent physicochemical properties, allow them to
Emerging Techniques and Materials for Water Pollutants Detection
289
(III) using a color-evolution based paper sensor by incorporating fluorescent
nanoprobe (carbon dots) onto the cellulose paper substrate. Ramírez et al. [95]
quantified lead (II) by developing an electrochemical affinity biosensor that combines glassy carbon electrodes and an aqueous dispersion of single-walled carbon
nanotubes covalently modified with cysteine residues. The sensor demonstrated
high selectivity for lead in complex solutions. Dong et al. [96] reported a simple
and green sensing system for the detection of free residual chlorine in water based
on fluoroscence quenching of Graphene quantum dots. In the work done by [97] an
“on-off” fluorescence phosphorus/nitrogen dual-doped carbon quantum dots probe
was developed for the determination of Chromium (VI). Liu et al. [98] reported a
simple and effective way to fabricate a ratiometric fluorescence sensor based on
dual-emission carbon dots-gold nanoclusters functionalized with dithiothreitol for
detecting mercury ions in water samples. Tang et al. [99] developed an electrochemical sensor by combining DNAzyme with quantum dots to detect lead with a
limit of detection of 7.8 pM. Yang et al. [100] combined reduced graphene oxide
and gold nanoparticles for detection of organophosphate paraoxon-ethyl with a
detection limit of 0.5 nM. Cui et al. [101] developed electrochemical acetylcholinesterase biosensor for detection of organophosphorus based pesticides by
using adsorption properties of titanium oxide sol-gel, chitosan and reduced
graphene oxide based multi-layered immobilization matrix. Nie et al. [102] proposed label-free aptamer surface-enhanced Raman scattering sensor for detection
of trace malathion residue; silver nanoparticles were modified with positively
charged spermine which served as capture reagents for the aptamer. Yang et al.
[103] labelled a specific antibody against E. coli O157: H7 using carboxyl functionalized graphene quantum dots and generated a strong fluorescent signal with the
detection limit of 100 cfu/mL as minimum. Parimaladevi et al. [104] designed a
sensor using a graphene boosted silver nanoparticles platform through surface
enhanced Raman scattering technique which was able to detect the toxic components in real textile effluent. Parvathi et al. [105] reported another sensor for textile
effluents based on graphene oxide mediated surface enhanced Raman scattering on
gold/reduced-graphene oxide nanocomposites. Chen et al. [106] developed
reduced graphene oxide-modified electrodes toward electroanalytical determination
of sulfamethoxazole in aqueous environments. Wong et al. [107] simultaneously
determined three drugs: terbutaline, nimesulide, and methocarbamol by designing a
composite electrode based on graphite oxide-polyurethane modified with
beta-cyclodextrin.
5.5 Future Trends and Recommendations
Research shows that nanomaterials-based sensors have shown promising results
with enhanced sensitivity and response time. Unique properties of nanomaterials
like size-tunable and shape-dependent physicochemical properties, allow them to
Emerging Techniques and Materials for Water Pollutants Detection
289