Sensitive determination of iron(III) by gold electrode modified with 2-mercaptosuccinic acid self-assembled monolayer

Facile Synthesis of N-Doped CDs from Ridge Gourd Seeds for the Sensitive Detection of Fe3+ Ions

This study reports the synthesis of nitrogen-doped carbon dots (N-CDs) from ridge gourd seeds via a hydrothermal process. The optical and physicochemical properties of the synthesized N-CDs were characterized using various techniques, including UV-Visible, fluorescence (FL), FT-IR, X-ray diffractometer (XRD), TEM, and XPS. The resulting N-CDs had an average size of 4.72 ± 0.2 nm, high monodispersity, and a quantum yield of 11.8%, which is related to efficient light emission. These N-CDs were highly dispersible in water and exhibited excitation-independent FL at varying excitation wavelengths. They showed excellent stability under diverse conditions, such as variations in pH, high ionic strengths, and prolonged light exposure, which enhances their use in potential applications. As FL probes, the N-CDs demonstrated the selective and sensitive detection of Fe3+ ions, with a significant FL quenching response. A strong linear correlation (R2 = 0.9899) was observed for Fe3+ concentrations in the range of 0-20 µM, with a detection limit of 67.3 nM. Notably, the FL quenching could be reversed by adding EDTA, which is a chelating agent for Fe3+, indicating the potential for reversible sensing applications. The biocompatibility of the N-CDs was assessed via an MTT assay on HCT 116 cells, which revealed low cytotoxicity (94.3 ± 1.8% viability at 75 µg/mL). These findings suggest that N-CDs are safe for in biological applications and hold great promise for use in biosensing, bioimaging, and environmental monitoring.

Advancements in Portable Voltammetry: A Promising Approach for Iron Speciation Analysis

Iron, a crucial element in our environment, plays a vital role in numerous natural processes. Understanding the presence and concentration of iron in the environment is very important as it impacts various aspects of our planet's health. The on-site detection and speciation of iron are significant for several reasons. In this context, the present work aims to evaluate the applicability of voltammetry for the on-site determination of iron and its possible speciation using a portable voltammetric analyzer. Voltammetry offers the advantage of convenience and cost-effectiveness. For iron (III) determination, the modification of a glassy carbon electrode (GCE) with an antimony-bismuth film (SbBiFE) using the acetate buffer (pH = 4) as a supporting electrolyte was used. The technique adopted was Square Wave Adsoptive Cathodic Stripping Voltammetry (SW-AdCSV), and we used 1-(2-piridylazo)-2-naphthol (PAN) as the iron (III) ligand. Linearity, repeatability, detection limit, and accuracy were determined using synthetic solutions; then, a Standard Reference Material (SRM) of 1643f Trace Elements in Water (iron content: 93.44 ± 0.78 µg L-1) was used for validation measurements in the real matrix. the accuracy of this technique was found to be excellent since we obtained a recovery of 103.16%. The procedure was finally applied to real samples (tap, lake, and seawater), and the results obtained were compared via Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES). The amount of iron found was 207.8 ± 6.6 µg L-1 for tap water using voltammetry and 200.9 ± 1.5 µg L-1 with ICP-OES. For lake water, 171.7 ± 3.8 µg L-1, 169.8 ± 4.1 µg L-1, and 187.5 ± 5.7 µg L-1 were found using voltammetry in the lab both on-site and using ICP-OES, respectively. The results obtained demonstrate the excellent applicability of the proposed on-site voltammetric procedure for the determination of iron and its speciation in water.

Determination of trace amount of iron cations using electrochemical methods at N, S doped GQD modified electrode

In this work, nitrogen and sulfur co-doped graphene quantum dot-modified glassy carbon electrodes (N, S-GQD/GCE) were used for the recognition of iron cations in aqueous solutions. The dissolved cations are detected based on the faradaic reduction or oxidation current of Fe(III) and Fe(II) obtained at the N, S-GQD/GCE surface. Cyclic voltammetry (CV), square wave voltammetry (SWV), and hydrodynamic amperometry are used as suitable electrochemical techniques for studying electrochemical behavior and determination of Fe cations. Based on the obtained results, it is concluded that the presence of free electrons in the structure of N, S-GQD could facilitate electron transfer reaction between Fe(III) and electrode surface which with increased surface area results in increased sensitivity and lower limit of detection. By performing suitable experiments, the best condition for preparing the modified electrode and determining Fe(III) was selected. Under optimized conditions, the amperometric response is linear from 1 to 100 nM of Fe(III) with a detection limit of 0.23 nM. The validity of the method and applicability of the sensor is successfully tested by the determination of Fe(III) in drug and water real samples. This sensor opened a new platform based on doped nanoparticles for highly sensitive and selective detection of analytes.

Mercaptosuccinic-Acid-Functionalized Gold Nanoparticles for Highly Sensitive Colorimetric Sensing of Fe(III) Ions

The development of reliable and highly sensitive methods for heavy metal detection is a critical task for protecting the environment and human health. In this study, a qualitative colorimetric sensor that used mercaptosuccinic-acid-functionalized gold nanoparticles (MSA-AuNPs) to detect trace amounts of Fe(III) ions was developed. MSA-AuNPs were prepared using a one-step reaction, where mercaptosuccinic acid (MSA) was used for both stabilization, which was provided by the presence of two carboxyl groups, and functionalization of the gold nanoparticle (AuNP) surface. The chelating properties of MSA in the presence of Fe(III) ions and the concentration-dependent aggregation of AuNPs showed the effectiveness of MSA-AuNPs as a sensing probe with the use of an absorbance ratio of A530/A650 as an analytical signal in the developed qualitative assay. Furthermore, the obvious Fe(III)-dependent change in the color of the MSA-AuNP solution from red to gray-blue made it possible to visually assess the metal content in a concentration above the detection limit with an assay time of less than 1 min. The detection limit that was achieved (23 ng/mL) using the proposed colorimetric sensor is more than 10 times lower than the maximum allowable concentration for drinking water defined by the World Health Organization (WHO). The MSA-AuNPs were successfully applied for Fe(III) determination in tap, spring, and drinking water, with a recovery range from 89.6 to 126%. Thus, the practicality of the MSA-AuNP-based sensor and its potential for detecting Fe(III) in real water samples were confirmed by the rapidity of testing and its high sensitivity and selectivity in the presence of competing metal ions.

An Electrochemical Sensor Based on Gold and Bismuth Bimetallic Nanoparticles Decorated L-Cysteine Functionalized Graphene Oxide Nanocomposites for Sensitive Detection of Iron Ions in Water Samples

In this work, gold and bismuth bimetallic nanoparticles decorated L-cysteine functionalized graphene oxide nanocomposites (Au-BiNPs/SH-GO) were prepared and applied to selective detection of Fe(III) in lake and seawater samples by modifying onto glassy carbon electrodes. Bimetallic nanoparticles have various excellent properties and better catalytic properties because of the unique synergistic effect between metals. The modified electrode was characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and Raman spectroscopy. Under optimized conditions, current peak intensity increased linearly with increasing Fe(III) concentration over the range of 0.2-50 μM and a detection limit of 0.07 μM (S/N = 3). The Au-BiNPs/SH-GO/GCE was used for the determination of Fe(III) in lake and seawater samples with recoveries ranged from 90 to 103%. Those satisfactory results revealed the potential application of the Au-BiNPs/SH-GO electrochemical sensor for heavy metals detection in environmental monitoring.

Electrochemical behavior of inorganic–organic hybrid polyoxometalate ((Cys)3[PW12O40]) nanostructure self-assembled monolayer on polycrystalline gold electrode surfaces

The synergistic effect of HPW and Cys enhanced electrochemical activity of Au-(Cys)PW electrode.

Evaluation of Micronutrient Sensors for Food Matrices in Resource-Limited Settings: A Systematic Narrative Review

In resource-limited settings, mass food fortification is a common strategy to ensure the population consumes appropriate quantities of essential micronutrients. Food and government organizations in these settings, however, lack tools to monitor the quality and compliance of fortified products and their efficacy to enhance nutrient status. The World Health Organization has developed general guidelines known as ASSURED (Affordable, Sensitive, Specific, User-friendly, Rapid and Robust, Equipment-free, and Deliverable to end-users) to aid the development of useful diagnostic tools for these settings. These guidelines assume performance aspects such as sufficient accuracy, reliability, and validity. The purpose of this systematic narrative review is to examine the micronutrient sensor literature on its adherence towards the ASSURED criteria along with accuracy, reliability, and validation when developing micronutrient sensors for resource-limited settings. Keyword searches were conducted in three databases: Web of Science, PubMed, and Scopus and were based on 6-point inclusion criteria. A 16-question quality assessment tool was developed to determine the adherence towards quality and performance criteria. Of the 2,365 retrieved studies, 42 sensors were included based on inclusion/exclusion criteria. Results showed that improvements to the current sensor design are necessary, especially their affordability, user-friendliness, robustness, equipment-free, and deliverability within the ASSURED criteria, and accuracy and validity of the additional criteria to be useful in resource-limited settings. Although it requires further validation, the 16-question quality assessment tool can be used as a guide in the development of sensors for resource-limited settings.

Speciation determination of iron and its spatial and seasonal distribution in coastal river

In this study, the speciation of iron (Fe), including total Fe (TFe) and acidified dissolved Fe (ADFe), was assessed by fast cathodic absorption stripping voltammetry, using a gold electrode and 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP) as a novel complexing agent for Fe. The validity and accuracy of this method were compared with the standard spectrophotometry and tested by the standard samples. Under optimized conditions, the Fe response was linear within the range of 0.01 to 1 μM with a detection limit of 1.2 nM. To further validate this method, the variation in concentrations of TFe and ADFe were investigated at twelve sampling stations in a local coastal river, in both the dry and wet season. Additionally, to further understand the interaction between Fe and environmental factors, the relationships between the concentration of Fe species and dissolved oxygen (DO) and salinity were also discussed.

Voltammetric determination of iron with catalytic system at a bismuth bulk annular band electrode electrochemically activated

A novel DPV procedure based on in situ activated bismuth bulk annular band electrode (BiABE) was applied for the determination of Fe(iii).

Electrochemical determination of Ga(III) through formation of Ga(III)-deferrioxamine B nanostructures on the glassy carbon electrode surface

Selective and sensitive determination of Ga(III) in the presence of Fe(III), as the main interfering ion is studied by using glassy carbon electrode modified with deferrioxamine B (GC-DFO). Characterization and analytical application are performed by different methods including cyclic and differential pulse voltammetry (CV and DPV), electrochemical impedance spectroscopy (EIS), and Field Emission Scanning Electron Microscopy (FESEM). The DPV measurements showed two reduction peaks around -0.630 and -0.830V. While the current of both peaks varied linearly with Ga(III) concentration of the accumulation solution, the latter was more sensitive and used for construction of the calibration curve. The experimental parameters are studied and optimized. A dynamic calibration curve (6.0×10(-11) to 1.4×10(-9)molL(-1)), including a linear part, from 6.0×10(-11) to 1.0×10(-9)molL(-1) with mean RSDs of 5.3% for n=3 at 4.0×10(-10)molL(-1) Ga(III), and a detection limit of 2.0×10(-11) mol L(-1) Ga(III) is observed at the optimized conditions. The validity of the method and applicability of the sensor are successfully tested by determining of Ga(III) in natural (river) waters, rice and coal samples. The experimental data are presented and discussed from which the new sensor is characterized.

Optical sensor: a promising strategy for environmental and biomedical monitoring of ionic species

In this review, we cover the recent developments in fluorogenic and chromogenic sensors for Cu²⁺, Fe²⁺/Fe³⁺, Zn²⁺and Hg²⁺.

ω-Thio nitrilotriacetic chemically modified gold electrode for iron determination in natural waters with different salinity

The preparation, characterization and analytical application of a chemically modified gold electrode (CME), based on ω-thio nitrilotriacetic acid derivative (N-[5-[[[[20-(acetylthio)-3,6,9-trioxaeicos-1-yl]oxo]carbonyl]amino]-1carboxypentyl]iminodiacetic acid) self-assembled monolayer (SAM), have been described. The electrode has been characterized by electrochemical techniques and tested for its response towards metallic ions, demonstrating to be effective for the determination of ionized iron at sub-μg L(-1) level by differential pulse cathodic stripping voltammetry (DPCSV). The analytical response towards iron in natural water (tap water, marine water) and the interference of ions usually present and chelating agents (humic acids and EDTA as model ligand of high complexing capacity) have been evaluated.

Spectral properties of 4-(4-hydroxy-1-naphthylazo)benzenesulfonic acid and its application for colorimetric determination of trace Fe3+

A multifunctional dye, 4-(4-hydroxy-1-naphthylazo)benzenesulfonic acid was identified and synthesized and used to determine trace Fe³⁺ in three real environmental water samples. The mechanism of action between the dye and Fe³⁺ ion is discussed in detail.

Determination of iron(III) based on the fluorescence quenching of rhodamine B derivative

A new method for determination of iron(III) has been developed using a kind of rhodamine B derivative fluorescent probe, rhodamine amide (RHA), in acidic HAc-NaAc buffer solution. In this approach, the heavy atom effect of I₃(-) was applied to quench the fluorescence of RHA. When iron(III) and KI coexisted in HAc-NaAc buffer solution, iron(III) reacted with the excess KI to produce I₃(-) that quenched the fluorescence of RHA through the formation of a non-fluorescence compound. The results showed that the fluorescence intensity decrease of RHA presented a good linear relationship with the iron(III) concentrations in the range from 0.5 to 5.0 μmol L(-1) with the correlation coefficient of 0.9970, and the detection limit was 0.3 μmol L(-1) iron(III). The approach was applied to determination of iron(III) in water samples, and the recovery was found to be from 80.7% to 100. 8%.

Gold-deferrioxamine nanometric interface for selective recognition of Fe(III) using square wave voltammetry and electrochemical impedance spectroscopy methods

Deferrioxamine, a bacterial hydroxamic siderophore having high binding affinity for Fe(III), is used in its immobilized form, as self-assembled monolayer on Au, for accumulation and recognition of Fe(III) from the solution phase. The accumulated Fe(III) is detected via both active mode based on faradaic reduction current of Fe(III), and inactive mode based on impedimetric effect of accumulated Fe(III) against redox reaction of a suitable probe. Appropriate electrochemical techniques, square wave voltammetry and electrochemical impedance spectroscopy, are used for the transduction of analytical signals obtained by this sensor. Then, the parameters influencing the sensor response are optimized. In the best conditions, a linear response, from 1.0×10(-10) to 1.0×10(-7)M Fe(III) in logarithmic scale with a detection limit of 2.0×10(-11)M, and mean relative standard deviation of 1.7% for n=4 is observed. The results show that the sensor can be used for determination of Fe(III) in the presence of various inorganic ions and biological species. Validity of the method and applicability of the sensor are successfully tested by determination of Fe(III) in various real samples including plant tissue (corn leaves), industrial alloy (Ferrotitanium), and pharmaceutical samples (Venofer(®) ampoule, Ironorm(®) capsule, and V.M. Protein(®) powder).