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Explora: Environment
and Resource Experimental application of GQDs for nuclear materials removal

1.3. GQDs as smart nanomaterials 2. Materials and methods

Recently, some studies have demonstrated that carbon dots 2.1. Reagents
have various applications, including the ability to be used
in the manufacture of smart packaging, as they possess All reagents and solvents used were purchased from
antimicrobial, antioxidant, flexible, resistant, and moisture- Sigma-Aldrich, United States, while the radioactive
impervious properties. 18-20 Similarly, GQDs have also been material was donated by the Nuclear Energy Research
applied in several areas, mainly as nanomaterials in the Institute, Brazil.
removal of radioactive substances after the detonation of 2.2. Development of GQDs
a dirty bomb, presenting a viable approach to mitigate and
reduce the consequences. 21-22 The method employed for synthesizing GQD dispersions
was adapted from a previously documented study. In
29
A study carried out by our research group summary, this process involved using a graphite rod as
demonstrated that it is feasible to use the surface area of the anode and a platinum wire as the cathode. For the
GQDs to absorb uranium-238 in Alamine 336 solution. electrolyte, a mixture of 63.5 mL of 0.2 M citric acid and
In fact, its results corroborated that GQDs can be used as 36.5 mL of 0.2 M sodium citrate was prepared, resulting
smart devices to reduce the volume of radioactive waste, in 100 mL of electrolyte solution. The electrochemical
assisting the entire cycle of the radioactive industry (and oxidation was carried out for 24 h at a steady current of
its various interfaces) in dealing with the critical issue of 190 mA, utilizing an ICEL PS-1500 (Icel Manaus, Brazil)
the final disposal of radioactive waste. 23,24 Furthermore, it
demonstrates the use of graphene in the adsorptive removal adjustable power supply. After electrolysis, the resultant
of uranium ions from wastewater. Graphene was able to dispersion was filtered to eliminate larger particles. This
attract heavy and toxic metal ions, including radioactive filtered mixture was then concentrated by drying at 60°C
elements, such as uranium, due to its large surface area, until the volume was reduced to 10 mL. Subsequently,
electronic properties, tunable surface characteristics, and 50 mL of ethanol was added, and the upper phase, which
resistance. 25 contained the purified GQDs, was separated. These
purified GQDs were further dried at 60°C until they were
Due to the properties of GQDs, which include ready for use.
chemical stability, high surface area, and quantum
confinement effects, their unique electronic properties, 2.3. Characterizations
coupled with the ability to functionalize their surface 2.3.1. Dynamic light scattering (DLS) for size analysis
with various groups, make them suitable for interaction
with a wide range of substances, including radioactive The size distribution, average size, and polydispersity index
materials. The potential mechanism by which GQDs (PDI) of GQDs were analyzed using DLS with a Zetasizer
can remove radioactive materials involves adsorption. Nano ZS (Malvern Instruments, United Kingdom). This
The high surface area of GQDs provides an extensive assessment was conducted in triplicate at 25°C using a
platform for the adsorption of radioactive isotopes. quartz cuvette of 12 mm² and a laser incidence angle
Functionalization of GQDs can be tailored to enhance of 173° relative to the sample. Results were reported as
their affinity for specific radioactive isotopes, thereby mean ± standard deviation. To address challenges in
increasing the efficiency of adsorption. In addition, GQDs analyzing GQDs with DLS, a highly diluted solution
offer a more targeted approach, potentially reducing the (1:400,000) in Milli-Q water was utilized.
volume of secondary waste and increasing the efficiency
of decontamination. 23,26-28 2.3.2. Raman spectroscopy
Given the current global context, particularly Raman spectra were acquired using a Horiba-Jobin-Yvon
the escalation of wars and guerrilla activities, there T64000 triple (Horiba Jobin-Yvon, Japan) spectrometer
is a heightened risk of dirty bomb deployment and equipped with a confocal attachment and a liquid nitrogen-
increased vulnerability of nuclear power plants to cyber- cooled CCD detector. A green line (532.0 nm) from a
attacks. This situation necessitates the consideration solid-state laser (LAS-532-100-HREV [Q-BAIHE, China])
of materials that can swiftly decontaminate surfaces at 14 mW was used for excitation. The laser was focused
exposed to radioactive substances, thereby facilitating on the sample through an Olympus MPLN ×100 objective
rapid reutilization of these areas. Accordingly, this study lens, with the confocal attachment limiting the scattering
assesses the potential of GQDs as a nanomaterial candidate spot. Spectra collection was done in two modes: (i) at
for the decontamination of surfaces contaminated with various points on the sample surface and (ii) by altering
radioactive materials. the position vertically centered on a particle.

Volume 1 Issue 1 (2024) 3 doi: 10.36922/eer.3403