Addition Of Fe2 Research Articles

Analyzing the Role of Fe0 and Fe3+ in the Formation of Expanded Clay Aggregates.

The effect of the addition of Fe0 and Fe3+ on the formation of expanded clay aggregates was studied using iron-free kaolin as an aluminosilicates source. Likewise, the incorporation of cork powder as a source of organic carbon and Na2CO3 as a flux in the mixtures was investigated in order to assess its effect in combination with the iron phases. An experimental protocol, statistically supported by a mixture experiments/design of experiments approach, was applied to model and optimize the bloating index, density, absorption capacity, and mechanical strength. The process of expansion and pore generation and the associated decrease in density required the addition of iron, such that the optimum mixtures of these properties presented between 25 and 40 wt.% of Fe0 or Fe3+, as well as the incorporation of 3.5-5 wt.% of organic carbon. The addition of Fe3+ produced a greater volumetric expansion (max. 53%) than Fe0 (max. 8%), suggesting that the formation of the FeO leading to this phenomenon would require reducing and oxidizing conditions in the former and the latter, respectively. The experimental and model-estimated results are in good agreement, especially in the aggregates containing Fe0. This reinforces the application of statistical methods for future investigations.

Difunctional Fluorescent Probes for Iron and Hydrogen Sulfide Detection Based on Diphenyl Derivative.

In order to better monitor the content of Fe3+ and H2S in the biological environment, two new fluorescent probes were designed and synthesized. With the addition of Fe3+, the strong fluorescence emission of two probes was significantly quenched due to the paramagnetic effect of Fe3+. With the further addition of S2-, the fluorescence intensity was quickly restored. Two probes showed high selectivity and strong sensitivity for the detection of Fe3+ and S2-, and the fluorescence intensity "ON-OFF-ON" was accompanied with the interaction process. At the same time, two probes displayed good anti-interference ability which was not interfered by the existence of other ions. In addition, two probes illustrated fast response time to Fe3+, S2- and small cytotoxicity to cells. Therefore, two probes can provide a potential ideal tool for detecting Fe3+ and H2S in organisms and the environment.

One-pot synthesis of environmentally-friendly carbon quantum dots for “on-off” rapid fluorescent sensing of folic acid, Fe3+, and Ca2+

Detecting abnormal levels of folic acid (FA), Fe3+, and Ca2+ in the human body is crucial due to their association with various diseases. Orange peel carbon quantum dots (OP-CQDs) with blue fluorescence (λex = 370 nm, λem = 440 nm) were synthesized using a one-step hydrothermal method when waste biomass orange peel was utilized as the carbon source. An “on-off” fluorescence sensor, referred to as OP-CQDs-FA-Fe3+/Ca2+, was developed for quantitative analysis of the drug FA, as well as the metal ions Fe3+ and Ca2+. Additionally, the sensor was utilized for fluorescence imaging of HepG2 liver cancer cells, demonstrating its exceptional biocompatibility. The concentration of FA displayed a linear relationship in the range of 5.00–90.00 μmol L−1 and 0.30–2.50 mmol L−1, with a limit of detection (LOD) of 0.15 μmol L−1. The spiked recovery in folic acid tablets ranged from 95.70% to 104.50%. The addition of Fe3+ or Ca2+ leads to a reduction or restoration of the fluorescence intensity in the OP-CQDs-FA system, resulting in an “on-off” sensor mode. The spiked recoveries in human serum samples were 100.15%–100.48% for Fe3+ and 98.05%–98.18% for Ca2+. This study highlights the considerable potential of OP-CQDs for ion detection, drug analysis, and cell imaging.

Synthesis and structural characterization of azine based oligoesteric chemosensors for Fe2+ ion detection

AbstractAzine‐based monomer and its three oligoesters were synthesized, characterized with IR, UV, GC‐MS, GPC, 1H NMR, 13C{1H} NMR, 31P NMR and applied to chemosensor applications. In the chemosensor study, fluorophores show selective and sensitive responses with Fe2+ ions in the DMF/H2O solution (1 : 1, pH: 7.4, fluorophore: 5 μM). The quenching of fluorescence intensity with the addition of Fe2+ ion gives the correlation coefficient (R2) value above 0.99286, exhibiting good binding stoichiometry nature of fluorophores with Fe2+ than the oligoesters. The high detecting capability of oligoesters is further ascertained by its higher LOD than the monomer (5.05×10−7). The binding constant values of fluorophores obtained from the Benesi‐Hildebrand plot show that the oligoesters have a higher binding ability (1.0012–1.0025 M−1) with Fe2+ ion than the monomer (1.0011 M−1). The conductivity nature of the oligoester gradually increased with the contact time of iodine. After 96hr of iodine doping, EMDAP exhibits higher conductivity (1.98×10−3 Scm−1) than the other oligoesters due to higher electron‐density nitrogen atoms in the structure. The EMDOP shows high dielectric constant value because of its π‐π interaction, loosely attached π electrons and high dipole moment values. All these experimental results are validated with the theoretical (DFT) approach by optimizing the structure of the fluorophore with B3LYP/6‐311++G(d,p) level basis set. The DFT approach also explains the mechanism of fluorescence quenching and the exact binding sites of fluorophores with Fe2+ ions.

Preparation and properties of lignin-based dual network hydrogel and its application in sensing

Ionic conductive hydrogels prepared from various biological macromolecules are ideal materials for the manufacture of human motion sensors from the perspective of resource regeneration and environmental sustainability. However, it is now difficult to develop conductive hydrogels including excellent self-healing and mechanical properties, mainly due to their inherent trade-off between dynamic cross-linked healing and stable cross-linked mechanical strength. In this work, alkali lignin-Polyvinyl alcohol-polyacrylic acid double network conductive hydrogels with high mechanical strength and good self-healing properties were prepared. We formed the primary network structure by hydrogen bonding interaction between polyvinyl alcohol, alkali lignin and polyacrylic acid, and the secondary network structure by coordination interaction with polyacrylic acid through the addition of Fe3+. The added lignin acts as a dynamic linkage bridge in a porous network mediated by multiple ligand bonds, imparting superior mechanical properties to the hydrogels. The relationships between the alkali lignin and iron ion dosage and the comprehensive properties of hydrogels (adhesion, antibacterial, self-healing, electrical conductivity and mechanical properties) were studied in detail. On this basis, the hydrogels explored the role of lignin in the regulation of hydrogels properties and revealed the self-healing and conductive mechanism.

Screening for chitin degrading bacteria in the environment of Saudi Arabia and characterization of the most potent chitinase from Streptomyces variabilis Am1

Forty-six promising chitinolytic isolates were recovered during a screening for chitinolytic bacteria in the environment of Saudi Arabia. The top three isolates belonged to the genus Streptomyces. Streptomyces variabilis Am1 was able to excrete the highest amount of chitinases, reaching the maximum at 84 h with 0.5% yeast extract and nitrogen source and 2% galactose as a carbon source. Purification of chitinase by DEAE-Cellulose and Sephadex G75 improved the specific activity to 18.6-fold and the recovery to 23.8% and showed a mass at 56 kDa. The optimal catalysis of the purified chitinase was at 40 °C and pH 8 with high thermostability and pH stability as reflected by a midpoint temperature value of 66.6 °C and stability at pH 4–9. The protein reagents SDS, EDTA, and EGTA significantly inhibited the enzyme and the EDTA-chelated chitinase restored its activity after the addition of Fe2+ ions suggesting a metallo-chitinase type with ferric ions as cofactors. Chitinase exerted high antifungal activity against some phytopathogenic fungi. Interestingly, the tested Streptomyces were able to produce chitosan nanocubes along with chitosan from chitin degradation which may be an additional power in their antifungal activity in nature. This work also reveals the importance of unexplored environments as a pool of promising microorganisms with biotechnological applications.

Construction of visible-light-response photocatalysis-self-Fenton system for the efficient degradation of amoxicillin based on industrial waste red mud/CdS S-scheme heterojunction

The photo-Fenton process is recognized as an effective water treatment method due to its superior efficiency and technical feasibility, but the application of photo-Fenton is limited by the addition of Fe2+/Fe3+ and hydrogen peroxide (H2O2). Herein, we construct a red mud/cadmium sulfide (RM/CdS) S-scheme heterojunction photocatalysis-self-Fenton system with decorating Aluminum oxide plant waste RM particles on the surface of CdS nanospheres, which can generate H2O2 in situ and simultaneously activate H2O2 to produce hydroxyl radicals (OH) active species, exhibiting efficient degradation of amoxicillin (AMX) antibiotic pollutant under visible light irradiation. Moreover, the formation of RM/CdS S-scheme heterojunction promotes the spatial separation of the charge carriers by the built-in electric field (IEF) at the interface between RM and CdS. This research presents a novel design route for the construction of S-scheme photocatalysis-self-Fenton system in the efficient treatment of wastewater based on the industrial wastes.

Reconstruction of CoNx /NC Catalyst during Oxygen Evolution Reaction by Fe3+ Modulation for Enhanced Activity and Stability.

The surface reconstruction of transition metal-based catalysts has been demonstrated to be beneficial for oxygen evolution reaction (OER). However, regulating the activity and stability of the components derived from reconstruction is challenging. Here, a strategy of Fe3+ ion modulating the reconstruction components of CoN0.4 on a nitrogen-doped carbon carrier(CoN0.4 /NC) electrocatalyst for promoted OER activity and stability is reported. During the OER process, the cobalt nitride components on the surface of CoN0.4 /NC catalyst were converted into CoOOH and Co4+ species. The addition of Fe3+ stabilized the CoOOH phase and facilitated the formation of Fe-CoOOH active phase, enhancing the activity and stability of CoN0.4 /NC. The Fe10 -CoN0.4 /NC catalyst achieved a current density of 10 mA cm-2 at a low overpotential of 300 mV (vs. RHE) with a Tafel slope of 68.12 mV dec-1 . The overpotential of Fe10 -CoN0.4 /NC was 122 mV lower than that of the CoN0.4 /NC catalyst and was comparable to commercial RuO2 catalyst. This study develops a novel technology for regulating the production of reconstructed species using Fe3+ ions.

Electro-Fenton oxidation of printing and dyeing wastewater with CO2 activated CuFeC and CuMnC aerogel cathode

An electro-Fenton (EF) system with CuFeC and CuMnC aerogel cathodes was proposed without an additional Fe2+ or H2O2 for the efficient degradation of actual printing and dyeing wastewater (PDW). The CO2 activated CuFeC aerogel as the cathode showed the highest chemical oxygen demand (COD) removal efficiency compare to other cathodes. Structural characterization revealed that CO2 activation significantly enlarged the cathode porosity and surface area to increase the exposure of active sites to catalysis. During a 60 min experiment, the COD removal in the EF system with CO2–activated CuFeC and CuMnC aerogel cathodes reached 72.8 % and 51.5 %, respectively. The high COD removal of PDW with CO2-activated CuFeC aerogel could be achieved at a wide range of pH values (3~8). The enhanced mineralization efficiency of the CuFeC aerogel was mostly attributed to the synergistic effect between Fe and Cu, which benefited the oxygen reduction reaction (ORR) ability to produce more H2O2 and generate more in-situ ·OH. The possible oxidation pathway of 2, 4, 6-trichlorophenol was proposed via an intermediate study. Moreover, the CO2–activated CuFeC aerogel presented low Fe and Cu leaching in an acidic solution and a long operational life span. This material can provide a feasible way for actual PDW purification through the EF process.

Metal‐Enhanced Fluorescence due to Salicylaldehyde‐Silver Nanoparticle Interactions for Fe3+ Sensing

AbstractSilver nanoparticles were synthesized using alkaline salicylaldehyde (SL) in the presence of silver nitrate. SL was oxidized to quinone form, while silver(I) was converted to silver (0). The solution was highly fluorescent, (quantum yield 7 %, λex 290 nm, λmax 424 nm), where silver (0) exhibited metal‐enhanced fluorescence and quinone acted as the fluorophore. The fluorescence was selectively quenched with the addition of Fe3+. No other metal shows such drastic fluorescence quenching. Thus, silver‐enhanced fluorescence is used to detect iron selectively and sensitively (limit of detection 2×10−9 M, linear detection ranges from 10−4 M to 8×10−9 M). The detection of iron was also done at various water of natural sources (drinking water tap water, rainwater, and Ganga River water). The iron concentration was quite similar to atomic absorption spectroscopy. The enhancement of fluorescence of the sliver atom is attributed to enhanced photonic mode density, related to the lightning rod effect. The quenching of silver‐enhanced fluorescence was attributed to the destruction of the capping agent due to SL‐iron complexation. The variation of distance between the fluorophore and metalized surface was anticipated for the alteration of fluorescence with and without the Fe3+ion.

Rapid oxidation of acetaminophen with zero-valent copper induced hydrogen peroxide process in presence of ferric ion and chloride ion

Zero-valent copper-triggered hydrogen peroxide (Cu0/H2O2) process was widely used for the degradation of pollutants, while its oxidation efficacy was restrained by the interaction of Cu+ with O2 as well as the dismutation of Cu+. In this study, both ferric ion (Fe3+) and chloride ion (Cl−) were introduced into the Cu0/H2O2 (Fe3+/Cl−/Cu0/H2O2) system, and the removal of acetaminophen was immensely enhanced. In the Fe3+/Cl−/Cu0/H2O2, Fe3+ was converted to Fe2+ via the reaction of Fe3+ with Cu0 and Cu+, and the reaction between Cu+ and Fe3+ receded the reaction of Cu+ with O2, promoting the formation of reactive oxygen species; Cl− integrated with Cu+ to form the Cu-Cl chelate, and Cl− helped the comproportionation of Cu0 and Cu2+ to form CuCl, which decreased the reaction of Cu+ with O2 and promoted the generation of reactive oxygen species. Both the addition of Fe3+ and Cl− in the Cu0/H2O2 process greatly improved the utilization of Cu0. •OH, Various reactive oxygen species such as •OH, FeIVO2+ and reactive chlorine species were identified in the Fe3+/Cl−/Cu0/H2O2 process. There into, Fe2+ stimulated H2O2 to form •OH and FeIVO2+, and Cu+ triggered H2O2 to form •OH rather than Cu3+, and partial •OH was transferred to reactive chlorine species via the interaction of •OH with Cl−. After increasing the solution pH to > 7.0 and leaching solution, the total copper of reaction solution was below 0.455 mg/L. These results suggested that the Fe3+/Cl−/Cu0/H2O2 process was feasible, effective and environmentally safe, and the research offered a theory instruction for the application of Fe3+ and Cl−-enhanced Cu0/H2O2 process in pollutants decomposition.

Iron-mediated oxidative stress induces PD-L1 expression via activation of c-Myc in lung adenocarcinoma.

Introduction: The PD-1/PD-L1 axis is hijacked by lung adenocarcinoma (LUAD) cells to escape immune surveillance. PD-L1 expression in LUAD is affected, among others, by the metabolic trafficking between tumor cells and the tumor microenvironment (TME). Methods: Correlation between PD-L1 expression and iron content within the TME was established on FFPE LUAD tissue samples. The effects of an iron rich microenvironment on PD-L1 mRNA and protein levels were assessed in vitro in H460 and A549 LUAD by using qPCR, western blot and flow citometry. c-Myc knockdown was performed to validate the role of this transcription factor on PD-L1 expression. The effects of iron-induced PD-L1 on T cell immune function was assessed by quantifying IFN-γ release in a co-colture system. TCGA dataset was used to analyse the correlation between PD-L1 and CD71 mRNA expression in LUAD patients. Results: In this study, we highlight a significant correlation between iron density within the TME and PD-L1 expression in 16 LUAD tissue specimens. In agreement, we show that a more pronounced innate iron-addicted phenotype, indicated by a higher transferrin receptor CD71 levels, significantly correlates with higher PD-L1 mRNA expression levels in LUAD dataset obtained from TCGA database. In vitro, we demonstrate that the addition of Fe3+ within the culture media promotes the significant overexpression of PD-L1 in A549 and H460 LUAD cells, through the modulation of its gene transcription mediated by c-Myc. The effects of iron lean on its redox activity since PD-L1 up-regulation is counteracted by treatment with the antioxidant compound trolox. When LUAD cells are co-cultured with CD3/CD28-stimulated T cells in an iron-rich culture condition, PD-L1 up-regulation causes the inhibition of T-lymphocytes activity, as demonstrated by the significant reduction of IFN-γ release. Discussion: Overall, in this study we demonstrate that iron abundance within the TME may enhance PD-L1 expression in LUAD and, thus, open the way for the identification of possible combinatorial strategies that take into account the iron levels within the TME to improve the outcomes of LUAD patients treated with anti-PD-1/PD-L1-based therapies.

Chemical precipitation–based treatment of acidic wastewater generated by chemical decontamination of radioactive concrete

Radionuclide-contaminated concrete can be turned into non-radioactive industrial waste through the sequential application of thermomechanical and chemical treatments. Herein, we examine the removal of 137Cs, 90Sr, and 60Co from complex acidic wastewater generated by chemical treatment, revealing that wastewater radioactivity due to these nuclides can be decreased to below the discharge criteria through the injection of potassium ferrocyanide and co-precipitation with BaSO4. In these processes, the concentration of Fe3+ in the wastewater significantly enhanced the removal of 137Cs via metal-ferrocyanide precipitation with effective hydroxide precipitation for 60Co, whereby additional Fe3+ was needed after the injection of potassium ferrocyanide. In the case of 90Sr, the nuclide formed an isomorphous sulphate by rapidly combining with Ba2+ in the BaSO4 lattice structure before particle growth. Furthermore, a large amount of BaSO4 will be required relatively to separate very low radioactivity of 90Sr, compared with high initial radioactivity. Thus, our work provides guidelines for reducing the volume of radioactive waste generated during nuclear facility decommissioning and should therefore help to decrease decommissioning cost.

Effect of dissolved unavoidable ions (Fe3+) from iron-containing gangue minerals on dispersion behavior of zinc oxide ore

With the decrease in zinc mineral resources, the secondary resource utilization of zinc tailings has attracted more attention all over the world. However, zinc oxide tailings contain many soluble minerals (limonite, pyrite), resulting in many metal ions interacting with the mineral surface. The effect of unavoidable ions (Fe3+) has become one of the challenges for the efficient separation and recovery of fine zinc oxide. Therefore, it is necessary to identify the effect of Fe3+ on the dispersion behavior of zinc oxide in order to improve the sorting efficiency and effective recycle of secondary resources. This study investigated the effect of Fe3+ on the dispersion behavior of fine smithsonite (zinc oxide). The turbidity experimental results showed that the turbidity of smithsonite was well dispersed in the deionized water, and decreased continuously with the addition of Fe3+. The smithsonite dispersion behavior was damaged by 5 × 10−4 mol/L Fe3+ from pH = 4 to 12. The results of zeta potential showed that the isoelectric point of smithsonite shifted positively from pH = 7.5 to 9.5. X-ray photoelectron spectroscopy (XPS) and solution chemistry analysis indicated that smithsonite was subjected to the action of Fe3+ to generate metal hydroxyl complexes or precipitates. The inter-particle interaction potential barrier of smithsonite at pH = 4 and 10 was 5.745 × 10−19 J and 2.31 × 10−19 J by calculations of DLVO theory, respectively. However, the potential energy of inter-particle interaction between smithsonite particles was less than zero in the presence of Fe3+, which indicated that the presence of iron ions disrupts the dispersion behavior of smithsonite. This study could provide theoretical guidance for the efficient recovery of secondary zinc resources from zinc oxide tailings.

Evaluation of persulfate enhanced electrocoagulation (EC/PS) for bio-treated landfill leachate: Organics transformation pathways and carbon flow quantitative analysis

The sulfate radical-based advanced oxidation processes (SR-AOPs) have shown promise in treating bio-treated landfill leachate (BLL). However, little is known about the dissolved organic matter (DOM) transformation and reaction mechanisms at the molecular level after treating BLL using SR-AOPs. This study investigates the DOM degradation and transformation pathways during both electrocoagulation (EC) and persulfate enhanced electrocoagulation (EC/PS) of real BLL samples. The results indicate that the removal efficiency of chemical oxygen demand (COD) and total organic carbon (TOC) were enhanced to 46.34% and 36.39%, respectively, once persulfate is coupled with EC. Additionally, the removal of fluorescent contaminants in BLL significantly enhanced after treatment with EC/PS to 91.57%, 80.99%, and 39.10% for biogenic humic-like components C1, C2, and C3, respectively. A decrease in the proportion of macromolecular and aromatic matters was observed after the EC/PS process. The degree of oxidation of DOM was reduced, and the compounds with unstable structure and high biodegradability became the main compounds in the EC/PS effluent. The analysis of sediments generated by EC and EC/PS showed a similar composition of FeOOH and Fe3O4, although there was additional Fe2(SO4)3 in the EC/PS sludge. The degraded organics in the solution and sediment phase were quantified by material flow analysis, indicating that the precipitation was the main contributor to DOM removal during the EC/PS process. These findings aid in understanding the role of PS in the EC/PS process during real landfill leachate treatment and reevaluate the advantages and limitations of PS as an oxidant.

Fabrication of antibacterial Fe3+-carboxymethylcellulose-polyacrylamide-Ag nanoparticles hydrogel coating for urinary catheters

Catheter-associated urinary tract infections (CAUTIs) are one of the most common hospital-acquired infections. In this study, a new Fe3+-carboxymethylcellulose (CMC)-polyacrylamide (PAAm) - Ag nanoparticles (AgNPs) interpenetrating hydrogel coating with antibacterial properties on the surfaces of latex urinary catheters was prepared with a simple dipping method. The morphology, chemical composition, surface roughness, and contact angles of the coated urinary catheters were characterized by using SEM, EDS, ATR-FTIR, XPS, AFM, and contact angle instruments, respectively. The antibacterial performance of the coated urinary catheters was characterized by the inhibition zone tests. Furthermore, the toxicity profile of the coated urinary catheters was also evaluated in vitro via MTT assay and hemolysis test. The experimental results showed that the Fe3+-CMC-PAAm-AgNPs hydrogel-coated urinary catheters had strong antibacterial effects. The concentration of AgNPs after the release of 30 days was still higher than the effective antibacterial concentration of the total Ag (0.1 ppb) and was lower than the toxic concentration of human cells (10 ppm). The inhibition zone tests of the coated urinary catheter against E. coli (ATCC25922) showed that both the CMC-PAAm-AgNPs hydrogel coatings and the Fe3+-CMC-PAAm-AgNPs hydrogel coatings had clear inhibition zones in the culture medium. The addition of Fe3+ exhibited synergistic antibacterial effects with AgNPs. Moreover, the coatings also showed admirable biocompatibility and hemocompatibility. The synergistic antibacterial mechanism was also proposed. The novel Fe3+-CMC-PAAm-AgNPs hydrogel coatings for urinary catheters would have great potential in reducing CAUTIs.

Rational Design of a Stable Fe‐rich Ni‐Fe Layered Double Hydroxide for the Industrially Relevant Dynamic Operation of Alkaline Water Electrolyzers

AbstractNickel‐iron layered double hydroxides (Ni‐Fe LDHs) consist of stacked Fe3+‐doped positively charged Ni‐hydroxide layers containing charge‐balancing anions and water molecules between the layers. Although Ni‐Fe LDHs are highly active in the oxygen evolution reaction (OER) under alkaline conditions, their poor operational stability remains an issue. Herein, based on density functional theory calculations, it is proposed that the inclusion of a higher Fe content (>40%) than the theoretical Fe3+ limit (≈25%) permitted by Ni‐Fe LDHs can lead to improved structural stability. An Fe‐rich Ni‐Fe LDH electrode is therefore prepared via a growth strategy based on the controlled oxygen corrosion of an Fe substrate, by enabling the incorporation of additional Fe2+ into the Ni2+‐Fe3+ LDH structure. Indeed, microstructural and elemental analysis confirm the presence of additional Fe2+. This Fe‐rich Ni‐Fe LDH electrode not only offers a low OER overpotential (≈270 mV at 200 mA cm−2) but also exhibits an excellent operational stability under dynamic operating environments without any significant performance degradation or metal ion dissolution. Finally, the practical feasibility of the Fe‐rich Ni‐Fe LDH electrode is demonstrated in a single‐cell (34.56 cm2) operation. These findings are expected to aid in the development of reliable OER electrodes for use in commercial water electrolyzers.

A Rhodamine B-Salicylic Acid Compound with Colorimetric /Fluorescent Dual Channel Response for the Identification of Fe3+

In this paper, a rhodamine B-salicylic acid based binary compound probe RB-SA was designed and synthesized, and its structure was characterized by 1HNMR and 13CNMR. The probe provides a colorimetric/fluorescent dual-channel response to Fe3+ in the aqueous phase. Under the induction of Fe3+, the spirolactam ring of the probe RB-SA changed from closed loop to open loop, and a new absorption peak appeared at 560 nm and the solution color changed from colorless to red, while the fluorescence signal turned on, and the fluorescence intensity at 587 nm increased linearly with the addition of Fe3+. It was shown that the probe RB-SA exhibited high sensitivity to Fe3+, with a minimum detection limit (LOD) of 5.19 nM and a complexation constant of 1.03 × 104 M-1 based on fluorescence spectroscopy titration data.

Synchronous Fe3+-Enhanced Colorimetric and Liquid SERS-Based Detection of Dopamine Using Core–Shell Plasmonic Nanoparticles

Reliable and direct detection of dopamine (DA), which is a crucial neurotransmitter, is required to diagnose dopamine-related diseases. However, the plasmonic colloidal sensing systems without prefunctionalization (e.g., aptamer, receptor, antibody, etc.) have not been well-established for trace DA detection yet. Herein, we develop a synchronous colorimetric and liquid-surface-enhanced Raman scattering (SERS) sensing system for the sensitive and selective detection of DA neurotransmitters using Au–Ag core–shell nanoparticles (Au@Ag CSNPs). The DA-mediated aggregation of Au@Ag CSNPs changed their plasmon resonance, leading to a distinct color change of the CSNP dispersion and generation of strong electromagnetic “hot spots” in the clustered CSNPs. Notably, the addition of Fe3+ ions to the CSNP dispersion intensified the DA-mediated aggregation of CSNPs, which significantly improved the colorimetric response and liquid-SERS detection of DA in the nanomolar range. Notably, the dual-mode sensing system without prefunctionalization demonstrated highly selective detection of the DA analyte against similar catecholamines (such as norepinephrine and epinephrine), which can be potentially applied to the selective discrimination of trace DA in real samples.

Exploring the highly selective Fe(III) and Al(III) triggered “OFF-ON” ellagic acid based fluorescent sensor: Spectroscopic, structural elucidations and dual-response mechanism

Owing to the favorable efficiency and low cost, dual-response fluorescent sensors play critical roles in the development of fluorescence assay systems. In this paper, the dual-response fluorescent of ellagic acid was reported both turn-off to Fe3+ and turn-on to Al3+, as well as the effects of pH by UV–vis absorption and fluorescence emission spectroscopy. The addition of Fe3+ changed the color of the ellagic acid solution from colorless to grey-green, and the fluorescence emission was quenched. In contrast, the addition of Al3+ changed the colorless solution to light yellow, and the fluorescence emission was significantly enhanced. The coordination constants of EA to Fe3+ and Al3+ were determined to be 3.42 × 104 M−1 and 2.83 × 105 M−1, respectively, according to Job's plot. By comparing the reaction with urolithin and its derivatives, the fluorescence emission mechanism of the ellagic acid reaction with Fe3+ and Al3+ was elucidated. The detection limits of EA for Fe3+ and Al3+ were 9.80 × 10−7 and 1.90 × 10−7 M, respectively.