Colorimetric Detection of Chromium(VI) Ions in Water Using Unfolded-Fullerene Carbon Nanoparticles

Chromium Detection in Water Using Optical Methods: A Study of Reagent and Reagentless Approaches

Water contaminated with chromium (Cr) poses significant risks to public health and the environment, necessitating reliable detection techniques. This review study uniquely provides a comprehensive analysis of optical methods for detecting Cr pollution in water, focusing on both reagent-based and reagentless approaches, as well as various sensing platforms. Unlike existing reviews that primarily focus on electrochemical and colorimetric/fluorimetric methods, this work highlights the untapped potential of optical technologies, such as colorimetry, SPR, UV-Vis spectroscopy, and more, in detecting distinct Cr species, including reagent and reagentless based approaches. The findings demonstrate the high sensitivity and specificity of optical methods. Reagent-based approaches offer exceptional sensitivity but involve complex preparation and potential secondary contamination. In contrast, reagentless methods, while requiring sophisticated calibration, are more environmentally friendly and simpler to implement. Future directions emphasize the development of portable, cost-effective optical devices, improved Cr species differentiation, and integration with real-time data processing and remote sensing for enhanced field monitoring. This study informs researchers and policymakers about the latest advancements in optical detection techniques and their potential to enhance water quality monitoring.

A Polycaprolactone-Capped ZnO Quantum Dots-Based Fluorometric Sensor for the Detection of Fe3+ Ions in Seawater

Fe3+ ion plays a very active role in life, agriculture, and industry. Human health and the environment are seriously affected by the abnormal presence or excess of this cation. Therefore, the development of a fast, reliable, sensitive, and simple fluorescent probe to detect this cation is crucial. In the present paper, polycaprolactone-capped zinc oxide quantum dots were prepared for the determination of Fe3+ ions. The proposed fluorescent chemosensor exhibited a fluorometric and strong quenching effect toward Fe3+ ions at two wavelengths (303 and 602 nm). The limit of detection (LOD) was calculated as 0.410, and 0.333µM at the mentioned wavelengths. Also, the binding stoichiometric ratio was calculated as 1:1 by Job's plot. The findings indicated that the PCL@ZnO colorimetric chemosensor could be successfully applied with reliable, and good accuracy for the detection of Fe3+ ions in real seawater samples.

Cancer Incidence Relation to Heavy Metals in Soils of Kyzylorda Region of Kazakhstan

OBJECTIVE

The purpose of this study was to investigate the relationship of soil pollution factors such as heavy metal ions with the incidence of cancer in the Kyzylorda region of Kazakhstan.

METHODS

Concentrations of heavy metal ions in the soils of different sites of Kyzylorda region, Kazakhstan, were sampled and correlated with incidence of cancer in 2021.

RESULTS

Chromium content in the soil exceeded maximum permissible concentration (MPC) in the samples for all sites except Kazaly and Shieli, and the highest excess of 2.8 MPC was found in Terenozek. Content of copper, lead, and cobalt ions was also increased and varied in the range 1.9-15.4, 1.2-4, and 1.2-2.44 MPC, respectively. In addition, lung cancer incidence was statistically significantly correlated with soil concentration to MPC ratio of copper, cobalt, and lead; colorectal cancer was correlated with soil concentration of chromium. Cases of invasive cancer and mutations were recorded Terenozek and Kyzylorda areas.

CONCLUSION

The higher the soil concentration correlate with higher cancer incidence in Kyzylorda region, Kazakhstan.

Seed Priming with Zinc Oxide Nanoparticles to Enhance Crop Tolerance to Environmental Stresses

Drastic climate changes over the years have triggered environmental challenges for wild plants and crops due to fluctuating weather patterns worldwide. This has caused different types of stressors, responsible for a decrease in plant life and biological productivity, with consequent food shortages, especially in areas under threat of desertification. Nanotechnology-based approaches have great potential in mitigating environmental stressors, thus fostering a sustainable agriculture. Zinc oxide nanoparticles (ZnO NPs) have demonstrated to be biostimulants as well as remedies to both environmental and biotic stresses. Their administration in the early sowing stages, i.e., seed priming, proved to be effective in improving germination rate, seedling and plant growth and in ameliorating the indicators of plants' well-being. Seed nano-priming acts through several mechanisms such as enhanced nutrients uptake, improved antioxidant properties, ROS accumulation and lipid peroxidation. The target for seed priming by ZnO NPs is mostly crops of large consumption or staple food, in order to meet the increased needs of a growing population and the net drop of global crop frequency, due to climate changes and soil contaminations. The current review focuses on the most recent low-cost, low-sized ZnO NPs employed for seed nano-priming, to alleviate abiotic and biotic stresses, mitigate the negative effects of improper storage and biostimulate plants' growth and well-being. Taking into account that there is large variability among ZnO NPs and that their chemico-physical properties may play a role in determining the efficacy of nano-priming, for all examined cases, it is reported whether the ZnO NPs are commercial or lab prepared. In the latter cases, the preparation conditions are described, along with structural and morphological characterizations. Under these premises, future perspectives and challenges are discussed in relation to structural properties and the possibility of ZnO NPs engineering.

The Addition of Co into CuO-ZnO Oxides Triggers High Antibacterial Activity and Low Cytotoxicity

In the present work, a simple two-step method is proposed for mixed oxide synthesis aimed at the achievement of antibacterial nanomaterials. In particular, Cu, Zn and Co have been selected to achieve single-, double- and triple-cation oxides. The synthesized samples are characterized by XRD, IR, SEM and EDX, indicating the formation of either crystalline or amorphous hydrocarbonate precursors. The oxides present one or two crystalline phases, depending on their composition; the triple-cation oxides form a solid solution of tenorite. Also, the morphology of the samples varies with the composition, yielding nanoparticles, filaments and hydrangea-like microaggregates. The antibacterial assays are conducted against E. coli and indicate an enhanced efficacy, especially displayed by the oxide containing 3% Co and 9% Zn incorporated into the CuO lattice. The oxides with the highest antibacterial properties are tested for their cytotoxicity, indicating a low toxicity impact, in line with literature data.

CuO Nanoparticles and Microaggregates: An Experimental and Computational Study of Structure and Electronic Properties

The link between morphology and properties is well-established in the nanoparticle literature. In this report, we show that different approaches in the synthesis of copper oxide can lead to nanoparticles (NPs) of different size and morphology. The structure and properties of the synthesized NPs are investigated with powder X-ray diffraction, scanning electron microscopy (SEM), and diffuse reflectance spectroscopy (DRS). Through detailed SEM analyses, we were able to correlate the synthetic pathways with the particles' shape and aggregation, pointing out that bare hydrothermal pathways yield mainly spheroidal dandelion-like aggregates, whereas, if surfactants are added, the growth of the nanostructures along a preferential direction is promoted. The effect of the morphology on the electronic properties was evaluated through DRS, which allowed us to obtain the electron bandgap in every system synthesized, and to find that the rearrangement of threaded particles into more compact structures leads to a reduction in the energy difference. The latter result was compared with Density Functional Theory (DFT) computational models of small centrosymmetric CuO clusters, cut from the tenorite crystal structure. The computed UV-Vis absorption spectra obtained from the clusters are in good agreement with experimental findings.

Optical Chemical Sensors: Design and Applications

More than ever, optical chemical sensing is a thriving research field with a strong outlook in terms of future development and penetration into growing industrial markets [...].

A novel colorimetric assay for sensitive detection of kanamycin based on the aptamer-regulated peroxidase-mimicking activity of Co3O4 nanoparticles

Kanamycin is used widely in livestock farming due to its antimicrobial properties and low cost, but has led to antibiotic residues in food, which can damage human health. Therefore, there is an urgent need for convenient technology that can be used to detect kanamycin rapidly. We found that Co₃O₄ nanoparticles (NPs) possessed peroxidase-like activity that catalyzed the oxidation of 3,3',5,5'-tetramethylbenzidine to change color. Interestingly, a target-specific aptamer could regulate the catalytic activity of Co₃O₄ NPs and inhibit this effect through aptamer-target binding. On the basis of a colorimetric assay combined with an aptamer-regulatory mechanism, the linear range for quantitative detection of kanamycin was 0.1-30 μM, the minimum limit of detection was 44.2 nM, and the total time needed for detection was 55 min. Moreover, this "aptasensor" displayed excellent selectivity and could be applied to detect KAN in milk samples. Our sensor might have promising applications for kanamycin detection in animal husbandry and agricultural products.

Colorimetric and Fluorescent Sensing of Copper Ions in Water through o-Phenylenediamine-Derived Carbon Dots

Fluorescent nitrogen and sulfur co-doped carbon dots (NSCDs) were synthesized using a simple one-step hydrothermal method starting from o-phenylenediamine (OPD) and ammonium sulfide. The prepared NSCDs presented a selective dual optical response to Cu(II) in water through the arising of an absorption band at 660 nm and simultaneous fluorescence enhancement at 564 nm. The first effect was attributed to formation of cuprammonium complexes through coordination with amino functional groups of NSCDs. Alternatively, fluorescence enhancement can be explained by the oxidation of residual OPD bound to NSCDs. Both absorbance and fluorescence showed a linear increase with an increase of Cu(II) concentration in the range 1-100 µM, with the lowest detection limit of 100 nM and 1 µM, respectively. NSCDs were successfully incorporated in a hydrogel agarose matrix for easier handling and application to sensing. The formation of cuprammonium complexes was strongly hampered in an agarose matrix while oxidation of OPD was still effective. As a result, color variations could be perceived both under white light and UV light for concentrations as low as 10 µM. Since these color changes were similarly perceived in tap and lake water samples, the present method could be a promising candidate for simple, cost-effective visual monitoring of copper onsite.

Syntheses of APTMS-Coated ZnO: An Investigation towards Penconazole Detection

Extrinsic chemiluminescence can be an efficient tool for determining pesticides and fungicides, which do not possess any intrinsic fluorescent signal. On this basis, (3-aminopropyl) trimethoxysilane (APTMS)-coated ZnO (APTMS@ZnO) was synthesized and tested as an extrinsic probe for the fungicide penconazole. Several synthetic routes were probed using either a one-pot or two-steps method, in order to ensure both a green synthetic pathway and a good signal variation for the penconazole concentration. The synthesized samples were characterized using X-ray diffraction (XRD), infrared (IR), Raman and ultraviolet-visible (UV-Vis) spectroscopy, scanning electron microscopy (SEM) imaging and associated energy-dispersive X-ray (EDX) analysis. The average size of the synthesized ZnO nanoparticles (NPs) is 54 ± 10 nm, in line with previous preparations. Of all the samples, those synthesized in two steps, at temperatures ranging from room temperature (RT) to a maximum of 40 °C, using water solvent (G-APTMG@ZnO), appeared to be composed of nanoparticles, homogeneously coated with APTMS. Chemiluminescence tests of G-APTMG@ZnO, in the penconazole concentration range 0.7-1.7 ppm resulted in a quenching of the native signal between 6% and 19% with a good linear response, thus indicating a green pathway for detecting the contaminant. The estimated detection limit (LOD) is 0.1 ± 0.01 ppm.

Green synthesis of carbon quantum dots and their environmental applications

Green synthesis of scalable, high-quality, fluorescent carbon quantum dots (CQDs) from natural biomass remains attractive due to their outstanding environmental application. CQDs are an emerging class of zero-dimensional carbon nanomaterials (<10 nm) that have recently attracted much attention due to their strong optical properties, biocompatibility, nontoxicity, uniform particle size, high photostability, low-cost synthesis, and highly tunable photoluminescence. The unique properties of CQDs possess a broad range of prospective applications in a number of fields such as metal ions detection, photocatalysis, sensing, medical diagnosis, bioimaging, and drug delivery. CQD nanostructures are synthesized using various techniques such as hydrothermal method, laser ablation, microwave irradiation, electrochemical oxidation, reflux method, and ultrasonication. However, this type of fabrication approach requires several chemical reactions including oxidation, carbonization, and pyrolysis. Green synthesis of CQDs has several advantages such as the use of low-cost and non-toxic raw materials, renewable resources, simple operations, and being environment-friendly. This review article will discuss the physicochemical properties of CQDs techniques used in the production of CQDs, and the stability of CQDs along with their applications in wastewater treatment and biomedical fields.

A sensitive surface-enhanced resonance Raman scattering sensor with bifunctional negatively charged gold nanoparticles for the determination of Cr(VI)

Hexavalent chromium (Cr(VI)) pollution in the water system has seriously endangered human health and the environment. Herein, we propose a rapid, simple and sensitive surface-enhanced resonance Raman scattering (SERRS) sensor with the bifunctional negatively charged gold nanoparticles ((-)AuNPs) which employ as not only the oxidoreductase-like nanozyme but also the substrate to determine Cr(VI). (-)AuNPs effectively promoted the conversion of 3,3',5,5'-tetramethylbenzidine (TMB) into the blue product of 3,3',5,5'-tetramethylbenzidine diamine (oxTMB) in the presence of Cr(VI) and generated a strong SERRS signal at 1611 cm^-1. According to this principle, the Raman intensity difference at 1611 cm^-1 exhibited a satisfactory linear relationship with the logarithm of the Cr(VI) concentration from 10^-5 to 10^-9 M with a low limit of detection (LOD) of 0.4 nM. In addition, the possible SERRS enhancement mechanism, selectivity and reproducibility were also investigated. What's more, the SERRS platform was successfully applied in the complicated water samples, which was anticipated to become a promising analytical method for monitoring of Cr(VI) in the environment.