Page 49 - ACCB 2020

Nanotechnology for Combating Microbial Contamination. do Nascimento et al

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Figure 2: Schematic representation of (a) Hg detection mechanism by the interaction of Hg with OPD and
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non-aggregation of AuNPs; (b) detection system (AuNPs / OPD) in presence of several ions, showing the high
specifi city of OPD by Hg .
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Due to its high toxicity, the detection of Hg was also Certainly, the detection occurs by Cu quelation with
the aim of research teams that study the application of chelidamate chains from AuNPs. Due to quelation
AgNPs for water treatment. They can be used as a se- process, the colour of the AuNPs suspension changes
lective colorimetric sensor for the detection of Hg by from brown to blue (presence of free - Cu ), and later
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adding a solution at AgNPs dispersion followed by in- to colourless which indicates the total complexation of
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cubation at room temperature. Indeed, the presence of Cu . Apart from that, a precipitate also appears at the
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Hg at water would destroy AgNPs and release Ag , vial’s bottom (92). Likewise, Xin et al (93) developed
which is visually detected (90). The same approach was an electrode made with core-shell multiwalled carbon
tested for other cations, however, the visual colour chan- nanotubes / GO nanoribbons also coated with chitosan
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ging occurred only by Hg action. Although this appro- (CS), for bisphenol A (BPA) identifi cation at the water.
ach is free from complex and expensive equipment and The electrode was sensitive to BPA even in presence
+,
techniques; it is also limited by potential interference of several ions such as K Na , Ca , Mg , Al , Zn ,
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+
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from other cations during Hg detection. Besides that, Cu , indicating that technique is robust and could be
Ag+ released in water is also considered harmful for the applied at the fi eld.
environment as well as for human health.
4.4. Nanoparticles with antibacterial properties for
AgNPs were also applied as dual colorimetric sensors water decontamination
either for Hg detection as well as for hydrogen pe- Waterborne bacterial infections are a worldwide dile-
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roxide degradation by taking advantage of catalytic mma, especially because many types of microbes and
reduction properties of AgNPs (91). Similarly, Li et al their spores occur in water, sewage, and wastewater
(89) and Wang et al (91) used citrate to stabilize AuNPs (94). Therefore, water disinfection is an important is-
and AgNPs, respectively, during Hg detection. Indeed, sue even as its contaminant detection and degradation.
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H O was used as a catalytic agent for Hg detection. Due to the indiscriminate use of antibiotics, bacteria be-
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2 2
The advantage of this technique compared with that came more resistant. Moreover, traditional techniques
described above is the increased sensitivity towards for water disinfection such as ultraviolet irradiation and
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Hg concentrations in water, as well as progressive co- ozonation, promote local disinfection by a short time.
lour change from light- yellow to purple, which is due
to an increase in Hg concentration. Several NPs have been highlighted for water disinfec-
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tion including quantum dots, AgNPs, AuNPs, and CNSs
Other cations have been equally detected by AgNPs which are effi cient NPs to kill or immobilize bacteria
or AuNPs. Hereof, Alizadeh et al applied pyridines- and a few viruses (95). In this regard, Adams et al (96)
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functionalized AuNPs for Cu detection in water. investigated the antimicrobial activity of metal oxi-
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Rev. Asoc. Col. Cienc.(Col.), 2020; 32: 42-62.