Graphene oxide-assisted synthesis of bismuth nanosheets for catalytic stripping voltammetric determination of iron in coastal waters

Whole-Cell Biosensor for Iron Monitoring as a Potential Tool for Safeguarding Biodiversity in Polar Marine Environments

Iron is a key micronutrient essential for various essential biological processes. As a consequence, alteration in iron concentration in seawater can deeply influence marine biodiversity. In polar marine environments, where environmental conditions are characterized by low temperatures, the role of iron becomes particularly significant. While iron limitation can negatively influence primary production and nutrient cycling, excessive iron concentrations can lead to harmful algal blooms and oxygen depletion. Furthermore, the growth of certain phytoplankton species can be increased in high-iron-content environments, resulting in altered balance in the marine food web and reduced biodiversity. Although many chemical/physical methods are established for inorganic iron quantification, the determination of the bio-available iron in seawater samples is more suitably carried out using marine microorganisms as biosensors. Despite existing challenges, whole-cell biosensors offer other advantages, such as real-time detection, cost-effectiveness, and ease of manipulation, making them promising tools for monitoring environmental iron levels in polar marine ecosystems. In this review, we discuss fundamental biosensor designs and assemblies, arranging host features, transcription factors, reporter proteins, and detection methods. The progress in the genetic manipulation of iron-responsive regulatory and reporter modules is also addressed to the optimization of the biosensor performance, focusing on the improvement of sensitivity and specificity.

Designing a label-free electrochemical aptasensor based on polypyrrole-l-cysteine-reduced graphene oxide nanocomposite for detection of 25-hydroxyvitamin D3

Reliable and precise quantification of 25-hydroxyvitamin D3 in clinical samples is vital because vitamin D3 deficiency lead to several disorders, such as mental illness, osteoporosis, and coronavirus disease. Herein, we report the fabrication of a novel electrochemical aptasensor using a nanocomposite, including reduced graphene oxide, pyrrole, and l-cysteine, for the sensitive detection of 25-hydroxyvitamin D3 . Subsequently, the aptamer of 25-hydroxyvitamin D3 was immobilized on the surface of the modified electrode. Differential pulse voltammetry signals were utilized for studying the binding and measurement of 25-hydroxyvitamin D3 based on the oxidation peak. Under the optimum conditions, the designed electrochemical aptasensor exhibited a linear detection range of 0.001-150 nM, with a limit of detection of 0.006 nM. Furthermore, the proposed aptasensor selectively detected 25-hydroxyvitamin D3 compared to other analogs. Moreover, this aptasensor was successfully applied for the detection of 25-hydroxyvitamin D3 in human serum samples, which were quantified by the enzyme-linked immunosorbent assay method. The acceptable recoveries of 82.67%-111.07% demonstrated that this proposed electrochemical aptasensor can be a promising alternative for clinical methods of vitamin D determination.

Two-Dimensional Metal Nanostructures: From Theoretical Understanding to Experiment

This paper reviews recent studies on the preparation of two-dimensional (2D) metal nanostructures, particularly nanosheets. As metal often exists in the high-symmetry crystal phase, such as face centered cubic structures, reducing the symmetry is often needed for the formation of low-dimensional nanostructures. Recent advances in characterization and theory allow for a deeper understanding of the formation of 2D nanostructures. This Review firstly describes the relevant theoretical framework to help the experimentalists understand chemical driving forces for the synthesis of 2D metal nanostructures, followed by examples on the shape control of different metals. Recent applications of 2D metal nanostructures, including catalysis, bioimaging, plasmonics, and sensing, are discussed. We end the Review with a summary and outlook of the challenges and opportunities in the design, synthesis, and application of 2D metal nanostructures.

Electrochemical sensor based on N-CQDs/AgNPs/β-CD nanomaterials: Application to simultaneous selective determination of Fe(Ⅱ) and Fe(Ⅲ) irons released from iron supplement in simulated gastric fluid

Simultaneous selective determination of Fe (Ⅱ) and Fe (Ⅲ) is of great significance to the study of iron ion tracking and release of iron supplement in gastric fluid. In this paper, a composite material (N-CQDs/AgNPs/β-CD) was prepared by a one-pot method. The various characterizations confirmed the silver nanoparticles (AgNPs) grew in situ on the surface of nitrogen-doped carbon quantum dots (N-CQDs), and the β-cyclodextrin (β-CD) and AgNPs linked together by Ag-O bonds finally presented gourd-like nanoparticles on the surface of N-CQDs. Then, N-CQDs/AgNPs/β-CD modified glassy carbon electrode (GCE) was applied to detect Fe(II) and Fe(III) simultaneously. The cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) results confirmed that N-CQDs/AgNPs/β-CD enhanced electrode performances because of the synergistic effect between N-CQDs, AgNPs and β-CD. The sensor was successfully applied for the determination by differential pulse voltammetry (DPV) of Fe(II) and Fe(III) released from four iron supplementations in simulated gastric fluid (SGF).

Microwave-Assisted Rapid Synthesis of Luminescent Tryptophan-Stabilized Silver Nanoclusters for Ultra-Sensitive Detection of Fe(III), and Their Application in a Test Strip

A new preparation method for extreme fluorescent green emission tryptophan-stabilized silver nanoclusters (Tryp-AgNCs) is presented in this scientific research. The produced silver nanoclusters are dependent on tryptophan amino acid which contributes to normal growth in infants and the sublimation and recovery of human protein, muscles, and enzymes. Herein, we have introduced a green method by using microwave-assisted rapid synthesis. The subsequent silver nanoclusters (AgNCs) have excitation/emission peaks at 408/498 nm and display a considerable selectivity to Fe(III) ions. The tryptophan amino acid molecule was used in the synthesis process as a reducing and stabilizing agent. The Tryp-AgNCs’ properties were investigated in terms of morphology, dispersity, and modification of the synthesized particles using different advanced instruments. The luminescent nanoclusters traced the Fe(III) ions by the luminescence-quenching mechanism of the Tryp-AgNCs luminescence. Therefore, the extreme selectivity of the prepared nanoclusters was exhibited to the Fe(III) ions, permitting the sensitive tracing of ferric ions in the lab and in the real environmental samples. The limit of detection for Fe(III) ions based on Tryp-AgNCs was calculated to be 16.99 nM. The Tryp-AgNCs can be efficiently applied to a paper test strip method. The synthesized nanoclusters were used efficiently to detect the Fe(III) ions in the environmental samples. Moreover, we examined the reactivity of Tryp-AgNCs on various human tumor cell lines. The results show that the Tryp-AgNCs exhibited their activity versus the cancer cells in a dose-dependent routine for the perceived performance versus the greatest-used cancer cell lines.

Rapid and efficient colorimetric sensing of clindamycin and Fe3+ using controllable phyto-synthesized silver/silver chloride nanoparticles by Syzygium cumini fruit extract

Abstract

The first evidence of a green, single-step, and additive-free process for the fabrication of silver/silver chloride nanoparticles (Ag/AgCl NPs) by fruit extract of Syzygium cumini (S. cumini) without the usage of any stabilizer and halide source was provided. The formation of nanoparticles was optimized to control the shape, size, and stability via various pHs of the reaction mixture, the quantity of fruit extract, temperature, concentrations of silver ion, and reaction time. The optimal conditions were determined: pH = 7.0, the quantity of the leaf extract = 3.0 mL, silver ion concentration = 1.0 mM, temperature = 60 °C, and incubation time = 40 min. As an application in colorimetric sensing, the ability of the prepared Ag/AgCl NPs to sense clindamycin and Fe3+ ion in an aqueous medium was investigated. The SPR band and color of the solution of Ag/AgCl NPs undergo dramatic changes in exposure to clindamycin with new SPR peaks appearing at 500 nm, accompanied by a color change from yellow to pink due to the aggregation of NPs. Under the optimized pH of 3.0, this sensor was shown a linear dynamic range from 10.0 to 100.0 µM with a LOD of 1.2 µM and good linear relationships (R2 = 0.99) for clindamycin. On the other hand, the quenching of the SPR peak at 412 nm was used to monitor the Fe3+ ions with wide linear ranges of 10.0–350.0 µM under the optimized pH (pH = 9) with a LOD of 5.6 µM. In addition, the proposed sensor displayed applicability in the real sample containing clindamycin (in capsules and injection ampoules) and Fe3+ ions (in water samples) detection.

Graphical Abstract

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.

Broadband saturated absorption properties of bismuthene nanosheets

The nonlinear absorption properties of two-dimensional bismuthene nanosheets have great value for application in the photonics field. In this work, bismuthene nanosheets with a thickness of around 4 nm were prepared using the liquid phase exfoliation (LPE) method. The infrared waveband nonlinear absorption properties of bismuthene nanosheets were investigated using the open aperture Z-scan technique with four wavelengths of 950, 1064, 1200, and 1500 nm, respectively. Bismuthene nanosheets exhibited broadband saturated absorption (SA) properties at the infrared band. The lower saturated intensity indicated the advantages of bismuthene as a saturated absorber in the application of ultra-fast lasers in the infrared band.

Bismuthene nanosheets were exfoliated by the LPE method. And the SA properties have been studies by open aperture Z-scan method. The results showed bismuthene nanosheets display broadband saturated properties in near-infrared wavelengths.

Colloidal chemical bottom-up synthesis routes of pnictogen (As, Sb, Bi) nanostructures with tailored properties and applications: a summary of the state of the art and main insights

Adjusting the colloidal chemistry synthetic parameters for pnictogen nanostructures leads to a fine control of their physical properties and the resulting performance in applications. Image adapted from Slidesgo.com.

High-Yield Production of Water-Soluble MoS2 Quantum Dots for Fe3+ Detection and Cell Imaging

Uniform water-soluble MoS2 quantum dots (WS-MSQDs) were synthesized via a sequential combination of sintering/etching/exfoliation method and solvothermal route. The obtained WS-MSQDs with average size of approximately 3.4 nm exhibited sufficient water solubility and remarkable fluorescence properties. The WS-MSQDs were utilized as a probe for detection of Fe3+ ions with high selectivity and specificity. Furthermore, the WS-MSQDs exhibited high fluorescence stability under different conditions. Finally, the WS-MSQDs were successfully applied for the fluorescence imaging of Fe3+ in living cells, which exhibited practical potential for biomedical applications.

Solar Degradation of Sulfamethazine Using rGO/Bi Composite Photocatalysts

Heterogeneous photocatalysts for water decontamination were obtained by the optimized synthesis of bismuth-functionalized reduced graphene oxide (rGO/Bi) using the Hummer method and microwave treatment. Sulfamethazine (SMZ) was used as model pollutant to evaluate the photocatalytic efficacy. Photocatalysts were characterized by VP-SEM, HRTEM, XDR, XPS, RAMAN, and FTIR analyses, which confirmed the effective reduction of GO to rGO and the presence of bismuth as a crystalline phase of Bi2O3 polydispersed on the surface. Their performance was influenced by the rGO/Bi ratio, microwave temperature, and treatment time. The as-obtained 5%rGO/Bi composite had the highest photocatalytic activity for SMZ degradation under visible light irradiation (λ > 400 nm), achieving 100% degradation after only 2 h of treatment. The degradation yield decreased with higher percentages of rGO. Accordingly, the rGO/Bi catalysts efficiently removed SMZ, showing a high photocatalytic activity, and remained unchanged after three treatment cycles; furthermore, cytotoxicity tests demonstrated the nontoxicity of the aqueous medium after SMZ degradation. These findings support the potential value of these novel composites as photocatalysts to selectively remove pollutants in water treatment plants.

A micellized fluorescence sensor based on amplified quenching for highly sensitive detection of non-transferrin-bound iron in serum

A novel, micelle-based fluorescence system capable of selective and sensitive signal transduction for non-transferrin-bound iron (NTBI) in serum was devised. We demonstrated that an aggregated fluorogenic core in a micelle induces amplified fluorescence quenching, which differentiates this sensing platform from the numerous fluorescence-based tools previously developed for sensitive detection.

Dual-binding pyridine and rhodamine B conjugate derivatives as fluorescent chemosensors for ferric ions in aqueous media and living cells

Two new pyridine-type rhodamine B chemosensors (RBPO and RBPF) used to detect Fe3+ have been designed and synthesized, and the sensing behavior towards various metal ions was evaluated via UV-vis and fluorescence spectroscopic techniques. Both RBPO and RBPF not only have good spectral responses to Fe3+ in an EtOH/H2O solution (3 : 1, v/v, HEPES, 0.5 mM, pH = 7.33) with low detection limits and high binding constants, but also suffer from less interference from common metal cations. The two chemosensors are further proven to be practical in sensitively monitoring trace Fe3+ in real water specimens. Intracellular imaging applications demonstrated that RBPO and RBPF can be used as two fluorescent chemosensors for the detection of Fe3+ in living human breast adenocarcinoma (MCF-7) cells.

Reed-derived fluorescent carbon dots as highly selective probes for detecting Fe3+ and excellent cell-imaging agents

A kind of highly selective and sensitive fluorescent probe for detecting Fe3+, carbon dots (CDs), was prepared with renewable reed naturally containing C, N, O, and S elements as a green and eco-friendly carbon source by a simple hydrothermal process. The fluorescence of CDs without purification and surface modification can be quenched by Fe3+ in a wide concentration range of 0 to 362 μmol L-1 (concentration of Fe3+), with detection limits as low as 0.014 μmol L-1 in 0-50 μmol L-1. Characterizations, such as TEM, XPS, Raman and FTIR, confirmed that the static quenching mechanism involved the generation of non-luminescent complexes between Fe3+ and functional groups (carboxyl group, sulfur-oxyl group and hydroxyl group) on the surface of CDs and with the aggregation of CDs. More importantly, CDs had good biocompatibility and nontoxicity according to an MTT cell-viability assay, and cells labeled with CDs emitted blue, green and red color fluorescence. Thus, the static quenching mechanism was confirmed. So, this reed-derived natural CD solution can be utilized in detecting Fe3+, culture cells, and cell imaging.

Self-Assembly Fluorescent Cationic Cellulose Nanocomplex via Electrostatic Interaction for the Detection of Fe3+ Ions

In this work, an aggregation-induced emission (AIE) sensor for the detection of Fe3+ ions was fabricated through the electrostatic interaction between 1,1,2-triphenyl-2-[4-(3-sulfonatopropoxyl)-phenyl]-ethene sodium salt (SPOTPE) and quaternized cellulose (QC). The structure and properties of the SPOTPE/QC nanocomplex were studied by using ¹H NMR, spectrofluorophotometer, transmission electron microscopy (TEM), and dynamic laser light scattering (DLS). An aqueous solution of SPOTPE and QC resulted in a remarkably enhanced cyan fluorescence in comparison to that of the SPOTPE solution. Strong through-space electrostatic interaction between SPOTPE and QC is the main cause for the fluorescence emerging. The fluorescence of the SPOTPE/QC solutions show good stability over a wide pH range of 5.0⁻10.0. When introducing Fe3+ ions into the SPOTPE/QC solution, the fluorescence quenched within 5 s. SPOTPE/QC solutions exhibited high selectivity and sensitivity for the detection of Fe3+ ions with ignored interferences from other ions, and the detection limit was determined to be 2.92 × 10-6 M. The quenching mechanism was confirmed to be the consequence of the binding interactions between Fe3+ ions and SPOTPE/QC complex.

Graphene-derived nanomaterials as recognition elements for electrochemical determination of heavy metal ions: a review

This review (with 155 refs.) summarizes the progress made in the past few years in the field of electrochemical sensors based on graphene-derived materials for the determination of heavy metal ions. Following an introduction of this field and a discussion of the various kinds of modified graphenes including graphene oxide and reduced graphene oxide, the review covers graphene based electrodes modified (or doped) with (a) heteroatoms, (b) metal nanoparticles, (c) metal oxides, (d) small organic molecules, (e) polymers, and (f) ternary nanocomposites. Tables are provided that afford an overview of representative methods and materials for fabricating electrochemical sensors. Furthermore, sensing mechanisms are discussed. A concluding section presents new perspectives, opportunities and current challenges. Graphical Abstract Schematic illustration of electrochemical sensor for heavy metal ion sensing based on heteroatom-doped graphene, metal-modified graphene, metal-oxide-modified graphene, organically modified graphene, polymer-modified graphene, and ternary graphene based nanocomposites.

Development of rhodamine-based fluorescent probes for sensitive detection of Fe3+ in water: spectroscopic and computational investigations

Four novel rhodamine-based fluorescent probes (RE1–RE4) were designed and synthesized for sensitive detection of Fe³⁺ in water.

Determination of iron in seawater: From the laboratory to in situ measurements

The marine biogeochemistry of iron plays a significant role in regulating climate change. Trace dissolved iron in oceanic surface water can limit phytoplankton growth which in turn limits the carbon dioxide flux at the air/sea interface. To better understand the relationship between iron and its different species with phytoplankton, as well as the biogeochemical cycle of iron in seawater, accurate, sensitive, and in situ methods are needed for iron determination. This paper reviews the methods for determining iron in seawater from the laboratory, shipboard to in situ measurements, including such strategies as atomic spectrometry, spectrophotometry, chemiluminescence, and voltammetry, which will provide the foundation for developing reliable long-term iron monitoring and sensing platforms in the future.

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.

A novel luminescent hybrid material based on zinc complexes and graphene oxides for detection of Fe3+ in aqueous media

A novel GOS-modified zinc complex probe with water dispersibility is designed to detect Fe³⁺ in aqueous media (Stern–Volmer constant K_SV = 4 × 10⁶ L mol⁻¹).

Controlled synthesis of dendritic gold nanostructures by graphene oxide and their morphology-dependent performance for iron detection in coastal waters

Dendritic gold nanostructures were controllably synthesized by graphene oxide for voltammetric determination of Fe(iii) in coastal waters.