Performance of 4,5-diphenyl-1H-imidazole derived highly selective 'Turn-Off' fluorescent chemosensor for iron(III) ions detection and biological applications

Two fluorescent chemosensors, denoted as chemosensor 1 and chemosensor 2, were synthesized and subjected to comprehensive characterization using various techniques. The characterization techniques employed were Fourier-transform infrared (FTIR), proton (1 H)- and carbon-13 (13 C)-nuclear magnetic resonance (NMR) spectroscopy, electrospray ionization (ESI) mass spectrometry, and single crystal X-ray diffraction analysis. Chemosensor 1 is composed of a 1H-imidazole core with specific substituents, including a 4-(2-(4,5-c-2-yl)naphthalene-3-yloxy)butoxy)naphthalene-1-yl moiety. However, chemosensor 2 features a 1H-imidazole core with distinct substituents, such as 4-methyl-2-(4,5-diphenyl-1H-imidazole-2-yl)phenoxy)butoxy)-5-methylphenyl. Chemosensor 1 crystallizes in the monoclinic space group C2/c. Both chemosensors 1 and 2 exhibit a discernible fluorescence quenching response selectively toward iron(III) ion (Fe3+ ) at 435 and 390 nm, respectively, in dimethylformamide (DMF) solutions, distinguishing them from other tested cations. This fluorescence quenching is attributed to the established mechanism of chelation quenched fluorescence (CHQF). The binding constants for the formation of the 1 + Fe3+ and 2 + Fe3+ complexes were determined using the modified Benesi-Hildebrand equation, yielding values of approximately 2.2 × 103 and 1.3 × 104  M-1 , respectively. The calculated average fluorescence lifetimes for 1 and 1 + Fe3+ were 2.51 and 1.17 ns, respectively, while for 2 and 2 + Fe3+ , the lifetimes were 1.13 and 0.63 ns, respectively. Additionally, the applicability of chemosensors 1 and 2 in detecting Fe3+ in live cells was demonstrated, with negligible observed cell toxicity.

Chelating Effect of Siderophore Desferrioxamine-B on Uranyl Biomineralization Mediated by Shewanella putrefaciens

In contaminated water and soil, little is known about the role and mechanism of the biometabolic molecule siderophore desferrioxamine-B (DFO) in the biogeochemical cycle of uranium due to complicated coordination and reaction networks. Here, a joint experimental and quantum chemical investigation is carried out to probe the biomineralization of uranyl (UO22+, referred to as U(VI) hereafter) induced by Shewanella putrefaciens (abbreviated as S. putrefaciens) in the presence of DFO and Fe3+ ion. The results show that the production of mineralized solids {hydrogen-uranium mica [H2(UO2)2(PO4)2·8H2O]} via S. putrefaciens binding with UO22+ is inhibited by DFO, which can both chelate preferentially UO22+ to form a U(VI)-DFO complex in solution and seize it from U(VI)-biominerals upon solvation. However, with Fe3+ ion introduced, the strong specificity of DFO binding with Fe3+ causes re-emergence of biomineralization of UO22+ {bassetite [Fe(UO2)2(PO4)2·8(H2O)]} by S. putrefaciens, owing to competitive complexation between Fe3+ and UO22+ for DFO. As DFO possesses three hydroxamic functional groups, it forms hexadentate coordination with Fe3+ and UO22+ ions via these functional groups. The stability of the Fe3+-DFO complex is much higher than that of U(VI)-DFO, resulting in some DFO-released UO22+ to be remobilized by S. putrefaciens. Our finding not only adds to the understanding of the fate of toxic U(VI)-containing substances in the environment and biogeochemical cycles in the future but also suggests the promising potential of utilizing functionalized DFO ligands for uranium processing.

Conjugated Polymer-Based Hydrogel Film for a Fast and Sensitive Detection of Fe(Ⅲ) in Vegetables

Fluorescent film sensors are ideal for the real-time outdoor detection of heavy metal ions of Fe3+, but they are limited because of their low sensitivity and long response time due to their special structure. In this work, we constructed a fluorescent hydrogel for the specific detection of Fe3+, utilizing poly(9-fluorenecarboxylic acid) (PFCA) as the sensing moiety and sodium alginate (SA) as the cross-linking substrate, which exhibited a rapid and selective recognition of Fe3+ among a panel of 16 anions and 21 cations. It can sense Fe3+ at 0.1 nM immediately owing to the porous network structure of the PFCA-SA film that provided enhanced ion transport channels and active sites, and the "molecular line effect" of polymer PFCA. Moreover, we successfully applied this platform to detect Fe3+ in four different vegetable samples. This work provides an innovative and effective strategy for fabricating green and sustainable fluorescent sensors.

[The role of iron-uptake factor PiuB in pathogenicity of soybean pathogen Xanthomonas axonopodis pv. glycines]

Iron is an essential element for living organisms that plays critical roles in the process of bacterial growth and metabolism. However, it remains to be elucidated whether piuB encoding iron-uptake factor is involved in iron uptake and pathogenicity of Xanthomonas axonopodis pv. glycines (Xag). To investigate the function of piuB, we firstly generated a piuB deletion mutant (ΔpiuB) by homologous recombination. Compared with the wild-type, the piuB mutant exhibited significantly reduced growth and virulence in host soybean. The mutant displayed markedly increased siderophore secretory volume, and its sensitivity to Fe3+, Cu2+, Zn2+ and Mn2+ was significantly enhanced. Additionally, the H2O2 resistance, exopolysaccharide yield, biofilm formation, and cell mobility of ΔpiuB were significantly diminished compared to that of the wild-type. The addition of exogenous Fe3+ cannot effectively restore the above characteristics of ΔpiuB. However, expressing piuB in trans rescued the properties lost by ΔpiuB to the levels in the wild-type. Taken together, our results demonstrated that PiuB is a potential factor for Xag to assimilate Fe3+, and is necessary for Xag to be pathogenic in host soybean.

Upconversion luminescence nanosensor for detection of Fe3+ and phosphate ion based on the inner-filter effect

In this work, an upconversion luminescence (UCL) nanosensor for fast detection of ferric ion (Fe3+) and phosphate ion (Pi) is developed based on the inner-filter effect (IFE) between NaYF4:Yb/Er upconversion nanoparticles (UCNPs) and Fe3+-hypocrellin B (HB) complex. Fe3+-HB complex has strong absorption band (450-650 nm), which overlaps with the green emission peak of UCNPs at 545 nm. By adding Fe3+ and Pi, the UCNPs-HB system produces the red-shift change of absorption spectrum, which leads to the "on-off-on" process of IFE. So, with the specific recognition ability of HB for Fe3+ and the competitive complexation of Pi for Fe3+, the proposed nanosensor utilizes the UCL change to achieve the detection of the targets. For the detections of Fe3+, the linear range is 10-600 μM with a limit of detection (LOD) of 2.62 μM, and for Pi, the linear range is 5-100 μM with a LOD of 1.25 μM. The results for selectivity, precision, and recovery test are also satisfactory. Furthermore, the real sample detection shows that the proposed nanaosensor has a great potential in environmental and biological systems. An upconversion luminescence (UCL) nanosensor based on the inner-filter effect (IFE) between upconversion nanoparticles (UCNPs) and Fe3+-hypocrellin B (HB) complex for the detection of Fe3+ and phosphate ion has been proposed, which is promising to be a convenient and sensitive assay for monitoring Fe3+ and phosphate ion in different environments and biological systems.

Paper test strip for fluorescence detection of iron ion based on nitrogen, zinc and copper codoped carbon dots

In this study, a test strip for fluorometric analysis of iron ion (Fe3+) was constructed based on nitrogen, zinc and copper codoped carbon dots (NZC-CDs) as fluorescence probes. NZC-CDs were synthesized by hydrothermal method. The morphology, size, components, crystal state and optical properties of NZC-CDs were characterized by transmission electron microscope (TEM), Fourier-transform infrared (FT-IR), x-ray photoelectron spectroscopy (XPS), x-ray diffraction (XRD), UV-vis absorption and fluorescence spectroscopy techniques, respectively. NZC-CDs exhibited bright blue fluorescence under UV lamp with a quantum yield at 17.76%. The fluorescence of NZC-CDs was quenched by Fe3+possibly due to the static quenching. The possible fluorescence quenching mechanism was also discussed. The quenching fluorescence was linear with the concentration of Fe3+in the range of 2.5-400μM with a low detection limit of 0.5μM. For the convenient detection, the test strips based on filter paper were employed for Fe3+assay. Moreover, the present approach was successfully applied in the determination of Fe3+in real samples including black fungus, duck blood and pork liver. The sensing method had the potential application in more food analysis.

Combination of ferroptosis and pyroptosis dual induction by triptolide nano-MOFs for immunotherapy of Melanoma

Immunotherapy has good potential to eradicate tumors in the long term. However, due to the low immunogenicity of tumor cells, current cancer immunotherapies are not effective. To address this limitation, we constructed a BSA-FA functionalized iron-containing metal-organic framework (TPL@TFBF) that triggers a potent systemic anti-tumor immune response by inducing ferroptosis and pyroptosis in tumor cells and releasing large quantities of damage-associated molecular patterns (DAMPs) to induce immunogenicity, and showing excellent efficacy against melanoma lung metastases in vivo. This nanoplatform forms a metal-organic framework through the coordination between tannic acid (TA) and Fe3+ and is then loaded with triptolide (TPL), which is coated with FA-modified BSA. The nanoparticles target melanoma cells by FA modification, releasing TPL, Fe3+ and TA. Fe3+ is reduced to Fe2+ by TA, triggering the Fenton reaction and resulting in ROS production. Moreover, TPL increases the production of intracellular ROS by inhibiting the expression of nuclear factor erythroid-2 related factor (Nrf2). Such simultaneous amplification of intracellular ROS induces the cells to undergo ferroptosis and pyroptosis, releasing large amounts of DAMPs, which stimulate antigen presentation of dendritic cells (DCs) and the proliferation of cytotoxic T lymphocytes (CD4+/CD8 + T cells) to inhibit tumor and lung metastasis. In addition, combining nanoparticle treatment with immune checkpoint blockade (ICB) further inhibits melanoma growth. This work provides a new strategy for tumor immunotherapy based on various combinations of cell death mechanisms.

Integration of N, P-doped carbon quantum dots with hydrogel as a solid-phase fluorescent probe for adsorption and detection of Fe3

In this work, a novel nitrogen-phosphorus co-doped carbon quantum dots (N, P-CQDs) hydrogel was developed utilizing the as-synthesized N, P-CQDs and acrylamide (AM) with the existence of ammonium persulfate and N, N'-methylene bisacrylamide (N-MBA). In consistent with pure N, P-CQDs, the N, P-CQDs hydrogel also shows a dramatic fluorescence property with maximum emission wavelength of 440 nm, which can also be quenched after adsorbing iron ions (Fe3+). When the concentration of Fe3+is 0-6 mmol l-1, a better linear relationship between Fe3+concentration and the fluorescence intensities can be easily obtained. Additionally, the N, P-CQDs hydrogel exhibits better recyclability. This confirms that the N, P-CQDs hydrogel can be used for adsorbing and detecting Fe3+in aqueous with on-off-on mode. The fluorescence quenching mainly involves three procedures including the adsorption of Fe3+by hydrogel, integration of Fe3+with N, P-CQDs and the transportation of conjugate electrons in N, P-CQDs to the vacant orbits of Fe3+and the adsorption process follows a pseudo-second-order kinetic model confirmed in the Freundlich isotherm model. In conclusion, this work provides a novel route for synchronously removing and detecting the metal ions in aqueous by integrating N, P-CQDs with hydrogel with better recyclability.

Colorimetric Chemosensor for Cu2+ and Fe3+ Based on a meso-Triphenylamine-BODIPY Derivative

Optical chemosensors are a practical tool for the detection and quantification of important analytes in biological and environmental fields, such as Cu2+ and Fe3+. To the best of our knowledge, a BODIPY derivative capable of detecting Cu2+ and Fe3+ simultaneously through a colorimetric response has not yet been described in the literature. In this work, a meso-triphenylamine-BODIPY derivative is reported for the highly selective detection of Cu2+ and Fe3+. In the preliminary chemosensing study, this compound showed a significant color change from yellow to blue-green in the presence of Cu2+ and Fe3+. With only one equivalent of cation, a change in the absorption band of the compound and the appearance of a new band around 700 nm were observed. Furthermore, only 10 equivalents of Cu2+/Fe3+ were needed to reach the absorption plateau in the UV-visible titrations. Compound 1 showed excellent sensitivity toward Cu2+ and Fe3+ detection, with LODs of 0.63 µM and 1.06 µM, respectively. The binding constant calculation indicated a strong complexation between compound 1 and Cu2+/Fe3+ ions. The 1H and 19F NMR titrations showed that an increasing concentration of cations induced a broadening and shifting of the aromatic region peaks, as well as the disappearance of the original fluorine peaks of the BODIPY core, which suggests that the ligand-metal (1:2) interaction may occur through the triphenylamino group and the BODIPY core.

A Ratiometric Fluorescent Probe Based on RhB Functionalized Tb-MOFs for the Continuous Visual Detection of Fe3+ and AA

In this study, a red-green dual-emitting fluorescent composite (RhB@MOFs) was constructed by introducing the red-emitting organic fluorescent dye rhodamine B (RhB) into metal-organic frameworks (Tb-MOFs). The sample can be used as a ratiometric fluorescent probe, which not only avoids errors caused by instrument and environmental instability but also has multiple applications in detection. The results indicated that the RhB@MOFs exhibited a turned-off response toward Fe3+ and a turned-on response for the continuous detection of ascorbic acid (AA). This ratiometric fluorescent probe possessed high sensitivity and excellent selectivity in the continuous determination of Fe3+ and AA. It is worth mentioning that remarkable fluorescence change could be clearly observed by the naked eye under a UV lamp, which is more convenient in applications. In addition, the mechanisms of Fe3+- and AA-induced fluorescence quench and recovery are discussed in detail. This ratiometric probe displayed outstanding recognition of heavy metal ions and biomolecules, providing potential applications for water quality monitoring and biomolecule determination.

Hydrothermal Synthesis of Molybdenum Disulfide Quantum Dots for Highly Sensitive Detection of Iron Ions in Protein Succinate Oral Solution

In this paper, a molybdenum disulfide fluorescent probe with an Fe³⁺ fluorescent system was first synthesized by the hydrothermal method for the detection of iron ion concentration in oral solution of protein succinate. It was characterized by infrared, fluorescence, X-ray photoelectron spectroscopy, scanning electron microscopy, and transmission electron microscopy. The probes were found to have good stability, photobleaching, and storage stability. The effects of dilution, pH, reaction time, and iron ion concentration on the fluorescent system were also investigated. The relative fluorescence intensity [(I₀ - I)/I₀] showed a good linear relationship with the iron ion concentration in the range of 0-50 μM, with the linear equation [(I₀ - I)/I₀] = 0.0148[Fe³⁺] + 0.0833 (r² = 0.9943, n = 11) and the detection limit of 2.43 μM. The reaction mechanism was also explored, as well as its ion selectivity, reversibility, accuracy, precision, and concentration of Fe ions in the actual sample. It was found that the probe can selectively detect Fe ions with a certain degree of reversibility, accuracy, precision, and ideal recovery, and it can be used for the determination of Fe³⁺ in proteosuccinic acid oral solution.

The Ultrasensitive Detection of Aflatoxin M1 Using Gold Nanoparticles Modified Electrode with Fe3+ as a Probe

The increasing incidence of diseases caused by highly carcinogenic aflatoxin M₁ (AFM₁) in food demands a simple, fast, and cost-effective detection technique capable of sensitively monitoring AFM₁. Recent works predominantly focus on the electrochemical aptamer-based biosensor, which still faces challenges and high costs in experimentally identifying an efficient candidate aptamer. However, the direct electrochemical detection of AFM₁ has been scarcely reported thus far. In this study, we observed a significant influence on the electrochemical signals of ferric ions at a gold nanoparticle-modified glassy carbon electrode (AuNPs/GCE) by adding varying amounts of AFM₁. Utilizing ferricyanide as a sensitive indicator of AFM₁, we have introduced a novel approach for detecting AFM₁, achieving an unprecedentedly low detection limit of 1.6 × 10^-21 g/L. Through monitoring the fluorescence quenching of AFM₁ with Fe³⁺ addition, the interaction between them has been identified at a ratio of 1:936. Transient fluorescence analysis reveals that the fluorescence quenching process is predominantly static. It is interesting that the application of iron chelator diethylenetriaminepentaacetic acid (DTPA) cannot prevent the interaction between AFM₁ and Fe³⁺. With a particle size distribution analysis, it is suggested that a combination of AFM₁ and Fe³⁺ occurs and forms a polymer-like aggregate. Nonetheless, the mutual reaction mechanism between AFM₁ and Fe³⁺ remains unexplained and urgently necessitates unveiling. Finally, the developed sensor is successfully applied for the AFM₁ test in real samples, fully meeting the detection requirements for milk.

Synthesis of glutamine-based green emitting carbon quantum dots as a fluorescent nanoprobe for the determination of iron (Fe3+) in Solanum tuberrosum (potato)

Herein, we reported the use of N-doped green-emitting carbon quantum dots (N-CQDs) as a fluorescent probe for determining of Fe³⁺ ions in Solanum tuberosum for the first time. The N-CQDs were synthesised through an efficient, one-step, and safe hydrothermal technique using citric acid as the carbon source and glutamine as a novel nitrogen source. The temporal evolution of the optical properties was investigated by varying the synthetic conditions with respect to temperature (160 °C, 180 °C, 200 °C, 220 °C and 240 °C) and citric acid: glutamine precursor ratio (1:1, 1:1.5, l.2,1:3 and 1:4). The N-CQDs was characterised using Fourier-Transform Infra-red Spectroscopy (FTIR) High-resolution transmission electron microscope (HRTEM), ultraviolet-visible spectroscopy (UV-vis) and X-Ray diffraction analysis (XRD) while its stability was evaluated in different media; NaCl, Roswell Park Memorial Institute (RPMI) and Phosphate Buffered Saline (PBS), and at different pHs. The N-CQDs displayed green (525 nm) emission and were spherical with an average particle diameter of 3.41 ± 0.76 nm. The FTIR indicated carboxylic, amino, and hydroxyl functional groups. The as-synthesised N-CQDs were stable in NaCl (up to 1 M), RPMI, and PBS without any significant change in its fluorescent intensity. The pH evaluation showed pHs 6 and 7 as the optimum pHs, while the fluorometric analysis showed selectivity towards Fe ³⁺ in the presence and absence of interfering ions. The detection limit of 1.05 μM was calculated, and the photoluminescence mechanism revealed static quenching. The as-synthesised N-CQDs was used as a fluorescent nanoprobe to determine the amount of Fe³⁺ in Solanum tuberosum (Potatoes) tubers. The result showed a high level of accuracy (92.13-96.20%) when compared with an established standard analytical procedure with excellent recoveries of 99.23-103.9%. We believe the as-synthesised N-CQDs can be utilised as a reliable and fast fluorescence nanoprobe for the determining of Fe³⁺ ions.

Excitation-Wavelength-Dependent Luminescence of Chemically and Physically Mixed Europium and Terbium Phosphonates: Color-Tunable Luminescence, Near-White-Light Emission, and Selective Fe3+ Detection

Molecular lanthanide phosphonates [Ln₂ (H₃ tpmm)₂ (H₂ O)₆ ] ⋅ xH₂ O (Ln=Eu, EuP; Ln=Tb, TbP) were synthesized. Single-crystal X-ray diffraction confirmed that EuP has a sandwich-like dinuclear structure, in which the Eu(III) center adopts a {EuO₈ } distorted dodecahedral geometry. XRPD patterns prove that TbP and EuP are isomorphous and isostructural. EuP and TbP are highly thermally stable approaching 450 °C and exhibit red- and green-light emissions from the characteristic 4 f-4 f transition of the Eu³⁺ and Tb³⁺ , respectively. Interestingly, luminescence modulation is achieved for the chemically mixed Eu/Tb phosphonate analogues, c-Eu_x Tb_{2 -x} P (x=1.5, 1, 0.5), and physically mixed Eu/Tb phosphonate materials, p-yEuP : zTbP (y : z=3 : 1, 1 : 1, 1 : 3), with varying the excitation wavelength. Of particular note, near-white-light emission is also achieved for c-EuTbP, p-EuP : TbP, and p-EuP : 3TbP when excited at 365 nm. Therefore, these dinuclear molecular lanthanide phosphonates emitting excitation wavelength and Eu³⁺  : Tb³⁺ ratio dependent luminescence might be potential candidates for color-tunable luminescence materials and white-light-emitting materials. On the other hand, the bright green-light emission makes TbP to be an excellent reusable luminescence sensor for selective detection of Fe³⁺ with Stern-Volmer quenching constant (K_SV ) of 9.66×10³  M^-1 and detection limit (DL) of 0.42 μM through absorption competition caused luminescence quenching effect.

DTPA-Bound Planar Catechin with Potent Antioxidant Activity Triggered by Fe3+ Coordination

In diseases related to oxidative stress, accumulation of metal ions at the site of pathogenesis results in the generation of reactive oxygen species (ROS) through the reductive activation of oxygen molecules catalyzed by the metal ions. If these metals can be removed and the generated ROS can be strongly scavenged, such diseases can be prevented and treated. Planar catechins exhibit stronger radical scavenging activity than natural catechins and can efficiently scavenge hydroxyl radicals generated by the Fenton reaction without showing pro-oxidant effects, even in the presence of iron ions. Hence, in the current study, we designed a compound in which diethylenetriaminepentaacetic acid (DTPA), a metal chelator, was bound to a planar catechin with enhanced radical scavenging activity by immobilizing the steric structure of a natural catechin to be planar. This compound showed almost no radical scavenging activity due to intramolecular hydrogen bonding of DTPA with the planar catechins; however, when coordinated with Fe³⁺, it showed more potent radical scavenging activity than planar catechins. Owing to its potent antioxidant activity triggered by metal coordination and its inhibition of ROS generation by trapping metal ions, this compound might exert excellent preventive and therapeutic effects against oxidative stress-related diseases.

Energy-efficient Preparation of Amino and Sulfhydryl Functionalized Biomass Carbon Dots via a Reverse Microemulsion for Specific Recognition of Fe(3+) and L-cysteine

Amino- and sulfhydryl- functionalized biomass carbon dots (BCDs) were prepared by one-pot reverse microemulsion for specific recognition of ferric ions (Fe³⁺) and L-cysteine (L-Cys). Green grapefruit peel was used as the carbon source while aminosilane and mercaptosilane were used as N- and S-supplier. Following the adsorption of Fe³⁺ on the surfaces of BCDs-NH₂ and BCDs-SH, the fluorescence responses was quenched step by step, while adding L-Cys to the BCDs-NH₂/Fe³⁺ system restored the fluorescence. The BCDs-NH₂ and BCDs-SH system exhibited extremely low limits of detection for Fe³⁺ of 3.2 and 3.0 nM, respectively, within a wide linear ranges of 0.006-200 μM and 0.004-200 μM, respectively. The BCDs-NH₂/Fe³⁺ systems were used as an optosensor for L-Cys in the concentration ranges of 0.08-30 and 30-1000 μM with a detection limit of 65 nM. Developed BCDs-NH₂ and BCDs-SH were able to respond to Fe³⁺ in water samples with satisfactory recoveries of 100.1%-103.1% and 94.6%-108.5%, respectively, and the BCDs-NH₂/Fe³⁺ system was also able to respond to BCDs-NH₂/Fe³⁺ in actual lake water samples with recoveries from 87.3% to 98.8%. Meanwhile, The BCDs-NH₂ exhibited good photoluminescence and stability, and the with a fluorescence quantum yield was as high as 25%. This work demonstrates the feasibility of using such materials to remove hazardous ions from water and employing the resulting complexes for optosensing in a sustainable manner.

Fluorescent copper conjugated curcumin cysteine nanoprobe for selective determination of Fe3+ and G-quadruplex DNA

The synthesis of fluorescent copper-curcumin-cysteine (Cu-CC) as a sensing platform is reported. The synthesized probe has been confirmed by UV-visible spectroscopy, FT-IR, XRD, SEM, and TEM characterization techniques, respectively. The mechanistic aspects of selective sensing of Fe³⁺ and detection of different G-quadruplex DNA have been illustrated based on the "turn-off-on" concept of a regeneratable fluorescence sensing probe at λ_ex 450 nm. Interestingly, we have noticed a high selectivity to Fe³⁺ ion by the developed Cu-CC sensing probe in comparison with other metal ions. Furthermore, the restoration of fluorescence of the sensing probe in the presence of different DNA sequences is illustrating a cost-effective, convenient, and reliable detection methodology of DNA detection. It is highly sensitive for the determination of Pu27, promoter c-MYC quadruplex DNA in a wide linear range of 100-700 nM having a detection limit of 13.1 nM (RSD: 0.15%) and sensitivity of 37.2 cps/nM. Whereas, the Pu18 and H-telo telomeric DNA sequences are showing a narrow linear range, i.e., 10 nM-200 nM and 10 nM-180 nM, respectively. The real-world sample analysis performance of the regeneratable sensing probe for Pu27 DNA detection in fresh human blood serum samples is showing a satisfactory result.

Synthesis, Adsorption Isotherm and Kinetic Study of Alkaline- Treated Zeolite/Chitosan/Fe(3+) Composites for Nitrate Removal from Aqueous Solution-Anion and Dye Effects

In the present study, alkaline-treated zeolite/chitosan/Fe³⁺ (ZLCH-Fe) composites were prepared and analyzed using scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR) and pH of zero point of charge (pH_zpc) to remove nitrates from water. The process was carried out using an adsorption method with a varied initial pH, adsorbent dosage, initial nitrate concentration and contact time. The pH_zpc demonstrated that the ZLCH-Fe surface had a positive charge between 2 and 10, making it easier to capture the negative charge of nitrate. However, the optimal pH value is 7. After 270 min, the maximum adsorption capacity and percent removal reached 498 mg/g and 99.64%, respectively. Freundlich and pseudo-second-order were fitted to the adsorption isotherm and kinetic models, respectively. An evaluation was conducted on the effects of anions-SO₄^2- and PO₄^3--and dyes-methylene blue (MB) and acid red 88 (AR88)-upon nitrate removal. The results indicated that the effect of the anion could be inhibited, in contrast to dye effects. However, the optimal pH values were changed to 10 for MB and 2 for AR88, resulting in a hydrogel formation. This might be indicated by the protonation of hydroxyl and amino groups resulting from a chitosan nitrate reaction in the AR88 solution.

Multifunctional N,S-doped and methionine functionalized carbon dots for on-off-on Fe3+ and ascorbic acid sensing, cell imaging, and fluorescent ink applying

Fluorescent carbon dots (CDs) have been identified as potential nanosensors and attracted tremendous research interests in wide areas including anti-counterfeiting, environmental and biological sensing and imaging in considering of the attractive optical properties. In this work, we present a CDs based fluorescent sensor from polyvinylpyrrolidone, citric acid, and methionine as precursors by hydrothermal approach. The selective quantifying of Fe3+ and ascorbic acid (AA) are based on the fluorescent on-off-on process, in which the fluorescent quenching is induced by the coordination of the Fe3+ on the surface of the CDs, while the fluorescence recovery is mainly attributed to redox reaction between Fe3+ and AA, breaking the coordination and bringing the fluorescence back. Inspired by the good water solubility and biocompatibility, significant photostability, superior photobleaching resistance as well as high selectivity, sensitivity, and interference immunity, which are constructed mainly from the N,S-doping and methionine surface functionalization, the CDs have not only been employed as fluorescence ink in multiple anti-counterfeiting printing and confidential document writing or transmitting, but also been developed as promising fluorescence sensors in solution and solid by CDs doped test strips and hydrogels for effectively monitoring and removing of Fe3+ and AA in environmental aqueous solution. The CDs have been also implemented as effective diagnostic candidates for imaging and tracking of Fe3+ and AA in living cells, accelerating the understanding of their function and importance in related biological processes for the prevention and treatment specific diseases.

Electronic Supplementary Material

Supplementary material (fluorescence spectra: UV and Xe irradiation, TG, thermo stability, ionic strength, relationship between fluorescence responses at different concentrations of Fe3+ and AA, reaction time-dependent fluorescent responses; XPS spectra of CDs + Fe3+ and Fe3+@CDs + AA; structural characterization; equations about fluorescence lifetime, quantum yield and LOD; comparison of the CDs for the detection of Fe3+ and AA with reported methods; detection of Fe3+ and AA in real samples; absorption of Fe3+ in environmental samples and MTT assay results) is available in the online version of this article at 10.1007/s12274-022-5107-7.

Sensitive, Selective and Reliable Detection of Fe3+ in Lake Water via Carbon Dots-Based Fluorescence Assay

In this study, C-dots were facilely synthesized via microwave irradiation using citric acid and ethylenediamine as carbon precursors. The fluorescence emissions of the C-dots could be selectively quenched by Fe³⁺, and the degree of quenching was linearly related to the concentrations of Fe³⁺ presented. This phenomenon was utilized to develop a sensitive fluorescence assay for Fe³⁺ detection with broad linear range (0–250, 250–1200 μmol/L) and low detection limit (1.68 μmol/L). Most importantly, the assay demonstrated high reliability towards samples in deionized water, tap water and lake water, which should find potential applications for Fe³⁺ monitoring in complicated environments.

Rice Husk-Derived Carbon Quantum Dots-Based Dual-Mode Nanoprobe for Selective and Sensitive Detection of Fe3+ and Fluoroquinolones

Herein, eco-friendly, water-soluble, and fluorescent carbon quantum dots (CQDs) with an average size of 8.3 nm were synthesized from rice husk (RH) using the hydrothermal method, and the CQDs were labeled as rice husk CQDs (RH-CQDs). The composition and surface functionalities were studied using X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and Raman spectroscopy. A study on the impact of pH and irradiation time on fluorescence affirmed the stability of RH-CQDs. The as-synthesized nanosensor has high selectivity and sensitivity for Fe³⁺ ions. Several photophysical studies were performed to investigate the interaction between RH-CQDs and Fe³⁺. Using the time-correlated single-photon technique, it is determined that the average lifetime value of RH-CQDs significantly decreases in the presence of Fe³⁺, which supports a dynamic quenching mechanism. The developed sensor exhibited excellent sensitivity with a detection limit in the nanomolar range (149 nM) with a wide linear range of 0-1300 nM for Fe³⁺ ions. The prepared nanosensor was also used to detect Fe³⁺ in a tablet supplement with high recoveries. Moreover, the RH-CQD nanoprobe was used to detect other analytes (fluoroquinolones) using the fluorescence enhancement technique. It showed high selectivity and sensitivity toward ofloxacin (OFX) and ciprofloxacin (CPX). The detection limits calculated were 150 nM and 127 nM with a linearity range of 50-1150 nM for OFX and CPX, respectively. The enhancement of the average lifetime value and quantum yield in the presence of OFX and CPX favors the increased fluorescence property of RH-CQDs through hydrogen bonding and charge transfer. In this work, the integration of two different mechanisms (fluorescence quenching and fluorescence enhancement) was followed to construct a single sensing platform for accurate quantification of dual-mode nanosensors for the detection of metal ions and fluoroquinolones by the excited-state electron transfer and hydrogen bonding mechanism, respectively. This strategy also stimulates the detection of more than one analyte.

Facile Synthesis of Green Fluorescent Carbon Dots and Their Application to Fe3+ Detection in Aqueous Solutions

Carbon dots (CDs), a class of fluorescent nanomaterials, have attracted widespread attention from researchers. Because of their unique chemical properties, these high-quality fluorescent probes are widely used for ion and molecule detection. Excess intake of many ions or molecules can cause harm to the human body. Although iron (in the form of Fe³⁺ ions) is essential for the human body, excess iron in the human body can cause many diseases, such as iron poisoning. In this study, we have synthesized fluorine and nitrogen co-doped carbon dots (FNCDs) by a hydrothermal method. These FNCDs exhibited good stability, selectivity, and anti-interference ability for Fe³⁺. Fe³⁺ could be detected in the range of 0.2–300 μM, and their detection limit is up to 0.08 μM. In addition, the recovery and relative standard deviation measured by the standard addition recovery method were not higher than 107.5% and 1.1%, respectively, indicating that FNCDs have good recovery and accuracy for Fe³⁺ detection.

Electrochemical Detection of Alpha-Fetoprotein Based on Black Phosphorus Nanosheets Modification with Iron Ions

Black phosphorus nanosheets (BPNSs) were synthesized with liquid exfoliation combined with the ultrasonic method and loaded with Fe³⁺ by simply mixing. The morphology, structure and electrochemical properties of the synthesized Fe³⁺/BPNSs were characterized by transmission electron microscopy (TEM), atomic force microscopy (AFM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and cyclic voltammetry (CV), etc. The load of Fe³⁺ can improve the electrochemical performance of BPNSs and enhance the sensitivity of the detection. Additionally, Fe³⁺/BPNSs display good biocompatibility. In this study, immunosensors based on Fe³⁺/BPNSs were constructed to detect alpha-fetoprotein (AFP). The detection is due to the specific binding between the AFP antigen and antibody on the surface of the immunosensors, which can reduce the current response of Fe³⁺/BPNSs. The immunosensors have a good linear relationship in the range of 0.005 ng·mL⁻¹ to 50 ng·mL⁻¹, and the detection limit is 1.2 pg·mL⁻¹. The results show that surface modification with metal ions is a simple and effective way to improve the electrochemical properties of BPNSs, which will broaden the prospects for the future application of BPNSs in the electrochemical field.

Carboxyl-Rich Carbon Dots as Highly Selective and Sensitive Fluorescent Sensor for Detection of Fe3+ in Water and Lactoferrin

As lactoferrin (LF) plays an essential role in physiological processes, the detection of LF has attracted increasing attention in the field of disease diagnosis. However, most current methods require expensive equipment, laborious pretreatment, and long processing time. In this work, carboxyl-rich carbon dots (COOH-CDs) were facilely prepared through a one-step, low-cost hydrothermal process with tartaric acid as the precursor. The COOH-CDs had abundant carboxyl on the surface and showed strong blue emission. Moreover, COOH-CDs were used as a fluorescent sensor toward Fe3+ and showed high selectivity for Fe3+ with the limit of detection (LoD) of 3.18 nM. Density functional theory (DFT) calculations were performed to reveal the mechanism of excellent performance for Fe3+ detection. Meanwhile, COOH-CDs showed no obvious effect on lactobacillus plantarum growth, which means that COOH-CDs have good biocompatibility. Due to the nontoxicity and excellent detection performance for Fe3+, COOH-CDs were employed as a fluorescent sensor toward LF and showed satisfying performance with an LoD of 0.776 µg/mL, which was better than those of the other methods.

Preparation of Eu0.075Tb0.925-Metal Organic Framework as a Fluorescent Probe and Application in the Detection of Fe3+ and Cr2O72

Luminescent Ln-MOFs (Eu0.075Tb0.925-MOF) were successfully synthesised through the solvothermal reaction of Tb(NO3)3·6H2O, Eu(NO3)3·6H2O, and the ligand pyromellitic acid. The product was characterised by X-ray diffraction (XRD), TG analysis, EM, X-ray photoelectron spectroscopy (XPS), and luminescence properties, and results show that the synthesised material Eu0.075Tb0.925-MOF has a selective ratio-based fluorescence response to Fe3+ or Cr2O72-. On the basis of the internal filtering effect, the fluorescence detection experiment shows that as the concentration of Fe3+ or Cr2O72- increases, the intensity of the characteristic emission peak at 544 nm of Tb3+ decreases, and the intensity of the characteristic emission peak at 653 nm of Eu3+ increases in Eu0.075Tb0.925-MOF. The fluorescence intensity ratio (I653/I544) has a good linear relationship with the target concentration. The detection linear range for Fe3+ or Cr2O72- is 10-100 μM/L, and the detection limits are 2.71 × 10-7 and 8.72 × 10-7 M, respectively. Compared with the sensor material with a single fluorescence emission, the synthesised material has a higher anti-interference ability. The synthesised Eu0.075Tb0.925-MOF can be used as a highly selective and recyclable sensing material for Fe3+ or Cr2O72-. This material should be an excellent candidate for multifunctional sensors.

New Fluorescent Probes for the Sensitive Determination of Glyphosate in Food and Environmental Samples

In this paper, a dual-functional probe, 2-(benzothiazol)-4-(3-hydroxy-4-methylphenyl) imino phenol (BHMH), was synthesized and characterized for the simultaneous detection of Cu2+ and Fe3+ in dimethyl sulfoxide/4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (DMSO/HEPES) (1:4, v/v, pH = 6.0). The limits of detections (LODs) for Cu2+ and Fe3+ were 9.05 and 48 nM, respectively. Based on the competitive coordination, the complex BHMH-Cu2+/Fe3+ exhibited good sensitivity and selectivity for glyphosate. The LODs of BHMH-Cu2+ and BHMH-Fe3+ for glyphosate were 0.41 and 0.63 μM, respectively. The probe quantitatively detected glyphosate in tap water, Songhua River water, local water and soil, and food samples. The colorimetric on-site glyphosate sensing through the probe BHMH-Cu2+ was also studied based on smartphones. BHMH and BHMH-Cu2+/Fe3+ exhibited outstanding imaging capabilities for Cu2+, Fe3+, and glyphosate in living cells with low cytotoxicity, especially the first time for glyphosate.

Cobalt-Doped Carbon Quantum Dots with Peroxidase-Mimetic Activity for Ascorbic Acid Detection through Both Fluorometric and Colorimetric Methods

In this work, we fabricated cobalt-doped carbon quantum dots (Co-CQDs) by a one-pot hydrothermal method with cobalt tetraphenylporphyrin and 1,2-ethanediamine as precursors. The morphology and structure of the Co-CQDs were characterized through transmission electron microscopy, X-ray diffraction spectra, Fourier transform infrared, and X-ray photoelectron spectra. The Co-CQDs emitted intense blue luminescence under ultraviolet irradiation and exhibited a typical excitation-dependent emission property. Moreover, they can act as a fluorescent probe for the detection of Fe³⁺ and ascorbic acid (AA) with high selectivity and sensitivity through an "on-off-on" mode. The limit of detection (LOD) of Fe³⁺ was measured as 38 μM (S/N = 3). The quenched emission of carbon quantum dots can be recovered with the addition of ascorbic acid (AA) to the Co-CQDs/Fe³⁺ system. The change of fluorescence was linear with the concentration of AA (0.6-1.6 mM) with the LOD of 18 μM. Furthermore, the Co-CQDs exhibited high oxidase-like catalytic behavior, which could convert transparent 3,3',5,5'-tetramethylbenzidine (TMB) into blue ox-TMB by dissolved oxygen. After adding ascorbic acid to the Co-CQDs/TMB system, the blue color of the solution faded due to the reduction of blue ox-TMB to colorless TMB. Based on this phenomenon, the Co-CQDs were capable of detecting AA (10-400 μM) with the LOD of 0.27 μM. The fluorometric and colorimetric assays based on the Co-CQDs for the AA detection were then successfully applied in fresh fruits. Furthermore, the high biocompatibility of the Co-CQDs against HeLa cells was verified by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) method. Thus, the Co-CQDs could be used as a powerful tool for the detection of AA in real samples through a dual-mode method.

Fabrication of carbon dots for sequential on-off-on determination of Fe3+ and S2- in solid-phase sensing and anti-counterfeit printing

Glutathione and 2-aminopyridine are used as carbon sources to prepare carbon dots (CDs) by a one-step hydrothermal reaction. The results show that the average particle diameter of CDs is 8.64 nm with uniform size distribution and the fluorescence quantum yield is 13.62%. We further demonstrate that novel CDs possess highly selective sensing of Fe³⁺ from 0.2 to 200 μM with a low detection limit (0.194 μM). Meanwhile, the fluorescence of CDs can be repeated many times by the addition of S^2-. Moreover, the CDs are used for biological imaging of living cells with well cell penetrability and low toxicity. Furthermore, it is successfully applied for anti-counterfeiting and information encryption. More interestingly, it can be doped with hydrogel and filter paper to prepare solid-phase sensors exhibiting high sensitivity and fast response, demonstrating their tremendous potential for the simple, rapid, and low-cost monitoring of Fe³⁺ and S^2-.

Improved hemostatic effects by Fe3+ modified biomimetic PLLA cotton-like mat via sodium alginate grafted with dopamine

The development of an excellent, bioabsorbable hemostatic material for deep wound remains a challenge. In this work, a biodegradable cotton-like biomimetic fibrous mat of poly (l-lactic acid) (PLLA) was made by melt spinning. Subsequently, SD composite was prepared by cross-linking sodium alginate (SA) with dopamine (DA). It was immobilized on the fibre surface, which inspired by mussel byssus. Finally, Fe3+ was loaded onto the 0.5SD/PLLA composite by chelation with the carboxyl of alginate and phenolic hydroxy of dopamine. The haemostasis experiment found that the hemostatic time 47 s in vitro. However, the bleeding volume was 0.097 g and hemostatic time was 23 s when 20Fe3+-0.5SD/PLLA was applied in the haemostasis of the rat liver. As a result of its robust hydrophilicity and bouffant cotton-like structure, it could absorb a large water from blood, which could concentrate the component of blood and reduce the clotting time. Furthermore, the addition of Fe3+ in the 0.5SD/PLLA had a significant effect on improve hemostatic property. It also displayed excellent antibacterial property for Escherichia coli and Staphylococcus aureus. Notably, it possesses superior hemocompatibility, cytocompatibility and histocompatibility. Hence, 20Fe3+-0.5SD/PLLA has high potential application in haemostasis for clinical settings due to its outstanding properties.

Surface Mechanism of Fe3+ Ions on the Improvement of Fine Monazite Flotation With Octyl Hydroxamate as the Collector

Froth flotation of fine minerals has always been an important research direction in terms of theory and practice. In this paper, the effect and mechanism of Fe³⁺ on improving surface hydrophobicity and flotation of fine monazite using sodium octyl hydroxamate (SOH) as a collector were investigated through a series of laboratory tests and detection measurements including microflotation, fluorescence spectrum, zeta potential, and X-ray photoelectron spectroscopy (XPS). Flotation tests have shown that fine monazite particles (−26 + 15 μm) cannot be floated well with the SOH collector compared to the coarse fraction (−74 + 38 μm). However, adding a small amount of Fe³⁺ to the pulp before SOH can significantly improve the flotation of fine monazite. This is because the addition of Fe³⁺ promotes the adsorption of SOH and greatly improves the hydrophobicity of the monazite surface. This can result in the formation of a more uniform and dense hydrophobic adsorption layer, as shown by the fluorescence spectrum and zeta potential results. From the XPS results, Fe³⁺ reacts with surface O atoms on the surface of monazite to form a monazite–O_surf–Fe group that acts as a new additional active site for SOH adsorption. A schematic model was also proposed to explain the mechanism of Fe³⁺ for improving surface hydrophobicity and flotation of fine monazite using octyl hydroxamate as a collector. The innovative point of this study is using a simple reagent scheme to float fine mineral particles rather than traditional complex processes.

A new sensor based on thieno[2,3-b]quinoline for the detection of In3+ , Fe3+ and F- by different fluorescence behaviors

Based on thieno[2,3-b]quinoline-2-carbohydrazide and salicylaldehyde, a novel fluorescent probe (L) was designed and synthesized. L could be used as a multifunctional sensor to sequentially detect In³⁺ and Fe³⁺ through fluorescence enhancement and fluorescence quenching in DMF/H₂ O buffer solutions. At the same time, L had good anti-interference ability, which could still detect In³⁺ and Fe³⁺ well in the presence of other metal ions. For F^- , it could be detected by enhancing the fluorescence change caused by the introduction of Al³⁺ . When other anions were present, the detection of F^- would not be interfered. The detection limits of In³⁺ , Fe³⁺ and F^- were 1.16×10^-10 M, 2.03×10^-8 M and 7.98×10^-9 M, respectively. The complexation model and sensing mechanism between L and In³⁺ , Fe³⁺ and F^- were confirmed by calculating structural optimization and energy optimization using Gaussian 09 software.

Simple and eco-friendly synthesis of crude orange-peel-derived carbon nanoparticles for detection of Fe3+ and ascorbic acid

Although fluorescence sensors based on carbon dots (CDs) have been developed widely, multicomponent detection using CDs without extra and tedious surface modification remains a challenge. Here, the crude carbon nanoparticles (CPs) as a fluorescence sensor were prepared through one-pot hydrothermal process using orange peel as the precursor. The method was simple, rapid, economical, and eco-friendly given that such extra steps as dialysis and lyophilization were not required. By adding ethanol into the reaction solvent, the fluorescence properties of orange-peel-derived CPs as well as their sensitivity of detecting Fe³⁺ with a limit of detection of 0.25 μM were improved. Additionally, orange-peel-derived CPs could be used as a fluorescence sensor for detection of ascorbic acid (AA) with a LOD of 5 μM. More importantly, the proposed fluorescence methods were successfully used to qualitatively and quantitatively analyze Fe³⁺ and AA in real samples. Recovery of Fe³⁺ from tap water was within the range 97.2-105.4%. Conversely, recovery of AA from vitamin C tablets and orange juices laid within the ranges 97.7-99.3% and 93.2-97.6%, respectively.

Preparation and characterization of metal-tea polysaccharide complexes and their inhibition on α-glucosidase

The preparation method and the sources of metal elements may affect the activity of the metal-polysaccharide complex. In this study, four Fe-tea polysaccharide complexes were prepared and three tea polysaccharides (TPSs) from different seasons were extracted. Moreover, the binding mode of TPSs with internal and external metallic elements as well as their inhibitory effect on α-glucosidase was explored. The results revealed that the binding mode (-C-O-Fe and -C-Fe) of the Fe-TPS complex prepared at pH 5.0 was closer to TPS with internal metallic elements. The TPS with the least amount of internal metallic elements (61.72 mg/g) exhibited a high inhibitory activity on α-glucosidase (37.90%). The inhibitory activity of Fe-TPS on α-glucosidase was lower than that without Fe. But the quenching effect and the inhibition type of TPSs on α-glucosidase were not affected by metallic elements. Therefore, the metallic elements have the potential to reduce the hypoglycemic activity of TPS. PRACTICAL APPLICATIONS: In this paper, TPS was extracted from crude tea in different seasons, and the effects of metallic elements in TPS on hypoglycemic activity, physicochemical properties, and structure of TPS were discussed. TPS metal complexes were prepared by adding Fe³⁺ or removing metallic elements, and the differences of internal metallic elements in TPS were discussed. It is of great academic significance to use tea pruned leaves and crude tea as potential resources to develop polysaccharide hypoglycemic products and to reveal the relationship between TPS metal ions and their structure and activity. In addition, it has guiding value for consumers to choose tea-producing regions and growers to choose chemical fertilizer.

Facile synthesis of N-doped carbon dots for direct/indirect detection of heavy metal ions and cell imaging

In this study, an approach for the facile, rapid, energy-saving, and sensitive determination of Fe³⁺ and Cr(VI) was developed. L-arginine/D-glucose carbon quantum dots (Arg/Glu-CQDs), with a photoluminescence quantum yield of 21%, were synthesized from L-arginine and D-glucose through a facile, hydrothermal process. The maximum emission wavelength of Arg/Glu-CQDs was observed at 450 nm, under an excitation wavelength of 365 nm. In addition, Arg/Glu-CQDs exhibited a sensitive and selective response to Fe³⁺ compared to Fe²⁺ and other metal ions. The Arg/Glu-CQDs' fluorescence was noticeably quenched through the inner filter effect (IFE) when Arg/Glu-CQDs were mixed with Fe³⁺. Accordingly, the Arg/Glu-CQDs/Fe²⁺ system could selectively detect Cr(VI); Cr(VI) could oxidize Fe²⁺ to Fe³⁺ and quench the fluorescence. The fluorescence sensor system (i.e., the Arg/Glu-CQDs/Fe²⁺ system) showed high sensitivity and excellent selectivity for the detection of Fe³⁺ and Cr(VI) in river water samples. Satisfactory detection efficiencies ranging from 97.07 to 103.46% were obtained. The cytotoxicity of Arg/Glu-CQDs was evaluated through an MTT assay using A549 cells as the target, to extend the application of Arg/Glu-CQDs to biological systems; the MTT assay indicated that the Arg/Glu-CQDs is non-cytotoxicity. Arg/Glu-CQDs were also successfully imaged in A549 cells indicating further application possibilities in bioimaging. Graphical abstract.

A Multi-response Aluminum Metal-organic Frameworks for Fluorescence Sensing of Fe3+, Sr2+, SiO32-and Toluene

A new Aluminum metal-organic frameworks(Al-MOF) based on tricarboxylate ligands(L){L = 2,2',2'-([1,3,5]-triazine-2,4,6-triimino)tribenzoic acid)} has been designed and synthesized. It can be served as a platform of multi-responsive fluorescence sensor for Fe³⁺, Sr²⁺and SiO₃^2-in water, which is mainly due to the significant enhancement effect of these ions on the fluorescence intensity of Al-MOF. Especially, Fe³⁺ions are rarely able to induce MOFs fluorescence enhancement. The limit of detection for three kinds of ions is 6.62* 10^-6M, 5.37* 10^-6M, 6.85* 10^-10M respectively. Meanwhile, It can also be used as a multi-response fluorescence probe to detect toluene in DMF solution, limit of detection is 9.16* 10^-3M respectively. The structure of Al-MOF was characterized by FTIR,¹H NMR, SEM, TAG, PXRD and element analysis. The PXRD showed that the structure of Al-MOF remained the high water stability and pH stability. The application of water samples and vegetables showed that Al-MOF had high sensitive detection for Fe³⁺ions.

The Diagnostic Value of Fe3+ and Inflammation Indicators in the Death of Sepsis Patients: A Retrospective Study of 428 Patients

Background

Studies have shown that a variety of blood inflammatory markers can be used to assess the criticality of patients with sepsis. In this study, the blood inflammatory factors related to the sepsis survival group and the death group were compared and analyzed, which can be used by clinicians to adjust sepsis patient treatment.

Methods

This study used retrospective methods to analyze the medical records of 428 patients with sepsis. The test of blood samples includes the patient's age, gender, hospital stays, the concentration of procalcitonin (PCT), absolute neutrophil count (ANC), absolute lymphocyte count (ALC), neutrophil-to-lymphocyte ratio (NLR), D-dimer (DD), Fe³⁺, and hemoglobin (Hb) in the venous blood of patients with sepsis. The detection of PCT methods adopts the sandwich immunofluorescence (IF). ROC curve was used for the diagnosis and analysis of various factors of sepsis.

Results

Among all the patients with sepsis, 133 patients died, with a mortality rate of 31.07%. Analysis of related inflammatory indicators and the patient's baseline parameters showed the patients age, the values of PCT, ANC, NLR, and DD in death group were statistically higher than those in survival group (all p values were <0.05). However, the concentration of Fe³⁺ and ALC show an opposite trend between the two groups. Regression analysis results showed the patient's gender, Fe³⁺, PCT, ANC, and DD are all independent prognostic factors for patients with sepsis. The results of the ROC curve of related diagnostic indicators show that DD has the best area under curve (AUC=0.700), the most sensitive index is ANC (74.44), and the most specific index is PCT (89.80). The results of the two-by-two combined diagnosis of the four indicators showed that the PCT+DD group had better AUC (0.748) and specificity (78.23), and the Fe³⁺+DD group had the best sensitivity (75.89).

Conclusion

In this study, the patient's gender and the inflammation-related markers of Fe³⁺, PCT, ANC, and DD can be used as independent risk factors affecting the prognosis of patients with sepsis. The combination of PCT+DD and Fe³⁺+DD has high diagnostic value for patients with sepsis.

Iron Homeostasis and Metabolism: Two Sides of a Coin

Iron is an ancient, essential and versatile transition metal found in almost all living organisms on Earth. This fundamental trace element is used in the synthesis of heme and iron-sulfur (Fe-S) containing proteins and other vital cofactors that are involved in respiration, redox reactions, catalysis, DNA synthesis and transcription. At the same time, the ability of iron to cycle between its oxidized, ferric (Fe³⁺) and its reduced, ferrous (Fe²⁺) state contributes to the production of free radicals that can damage biomolecules, including proteins, lipids and DNA. In particular, the regulated non-apoptotic cell death ferroptosis is driven by Fe²⁺-dependent lipid peroxidation that can be prevented by iron chelation or genetic inhibition of cellular iron uptake. Therefore, iron homeostasis must be tightly regulated to avoid iron toxicity. This review provides an overview of the origin and chemistry of iron that makes it suitable for a variety of biological functions and addresses how organisms evolved various strategies, including their scavenging and antioxidant machinery, to manage redox-associated drawbacks. Finally, key mechanisms of iron metabolism are highlighted in human diseases and model organisms, underlining the perils of dysfunctional iron handlings.

Subsequent monitoring of ferric ion and ascorbic acid using graphdiyne quantum dots-based optical sensors

Graphdiyne (GDY) as an emerging carbon nanomaterial has attracted increasing attention because of its uniformly distributed pores, highly π-conjugated, and tunable electronic properties. These excellent characteristics have been widely explored in the fields of energy storage and catalysts, yet there is no report on the development of sensors based on the outstanding optical property of GDY. In this paper, a new sensing mechanism is reported built upon the synergistic effect between inner filter effect and photoinduced electron transfer. We constructed a novel nanosensor based upon the newly-synthesized nanomaterial and demonstrated a sensitive and selective detection for both Fe³⁺ ion and ascorbic acid, enabling the measurements in real clinical samples. For the first time fluorescent graphdiyne oxide quantum dots (GDYO-QDs) were prepared using a facile ultrasonic protocol and they were characterized with a range of techniques, showing a strong blue-green emission with 14.6% quantum yield. The emission is quenched efficiently by Fe³⁺ and recovered by ascorbic acid (AA). We have fabricated an off/on fluorescent nanosensors based on this unique property. The nanosensors are able to detect Fe³⁺ as low as 95 nmol L^-1 with a promising dynamic range from 0.25 to 200 μmol L^-1. The LOD of AA was 2.5 μmol L^-1, with range of 10-500 μmol L^-1. It showed a promising capability to detect Fe³⁺ and AA in serum samples. Graphical abstract.

Nitrogen-Doped Carbon Quantum Dots from Poly(ethyleneimine) for Optical Dual-Mode Determination of Cu2+ and l-Cysteine and Their Logic Gate Operation

In this work, nitrogen-doped carbon quantum dots from poly(ethyleneimine) (PQDs) were synthesized by a low-cost and facile one-step hydrothermal method without other reagents. A quantum yield (QY) of up to 23.2% with maximum emission at 460 nm under an excitation wavelength of 340 nm was ascribed to the high nitrogen doping (20.59%). The PQDs selectively form a blue complex with Cu²⁺ accompanied by strong quenching of the fluorescence emission. Meanwhile, the PQD-Cu²⁺ complex exhibited selective fluorescence recovery and color disappearance on exposure to l-cysteine (Cys). The electron transfer from amino or oxygen groups on the PQDs to Cu²⁺ leads to fluorescence quenching, and a chromogenic reaction of the cuprammonium complex results in a color change. The strong affinity between Cys and Cu²⁺ causes the detachment of Cu²⁺ from the surface of PQDs, so the color of the solution disappears and the fluorescence of PQDs recovers. Under the optimized condition, the proposed sensor was applied to detect Cu²⁺ in the linear range of 0-280 μM. A detection limit of 4.75 μM is achieved using fluorescence spectroscopy and 4.74 μM by monitoring the absorbance variation at 272 nm. For Cys detection, the linear range of 0-800 μM with detection limits of 28.11 μM (fluorescence determination) and 19.74 μM (peak shift determination at 272 nm) was obtained. Meanwhile, the PQD-Cu²⁺ system exhibits distinguishable responses to other biothiols such as l-glutathione (GSH) and dl-homocysteine (Hcy). Based on the multimode signals, an "AND" logic gate was constructed successfully. Interestingly, besides Cu²⁺, Fe³⁺ can also quench the fluorescence of PQDs and the PQD-Fe³⁺ system exhibits superior selectivity for Cys detection. Most importantly, the proposed assay is not only simple, cheap, and stable but also suitable for detecting Cu²⁺ and Cys in some real samples.

Magnetic and Biocompatible Fullerenol/Fe(III) Microcapsules with Antioxidant Activities

Fullerene C₆₀ (refers to C₆₀ hereafter) has a unique three-dimensional architecture and intriguing physicochemical properties. It has great potential applications in materials chemistry and life science. However, a big obstacle for the widespread application of C₆₀ lies in the limited strategies to make supramolecular structures with diverse morphologies and functions. Herein, we report a strategy to prepare C₆₀-based, magnetic microcapsules which can be used as external antioxidants to effectively attenuate oxidative stress. The microcapsules are composed of fullerenol, a highly water-soluble C₆₀ multiadduct, and iron ions (Fe³⁺) released from a rusty nail. They can be easily obtained through coordination between the hydrophilic functional groups in fullerenol and Fe³⁺ with polystyrene microspheres as templates. The fullerenol/Fe³⁺ microcapsules have good colloidal stability both in water and serum. Their biocompatibility has been confirmed by in vitro tests on HEK293 and Hela cells. Electron spin resonance measurements indicate that the fullerenol/Fe³⁺ microcapsules can effectively scavenge hydroxyl radicals (OH·^-) produced by H₂O₂, which greatly improves the living environment of the cells. The fullerenol/Fe³⁺ microcapsules exhibit ferromagnetic properties and can respond to the external magnetic field, enabling magnetic manipulation, and/or separation in practical applications.

Fe3+-Sensitive Carbon Dots for Detection of Fe3+ in Aqueous Solution and Intracellular Imaging of Fe3+ Inside Fungal Cells

In this article, the Fe3+-sensitive carbon dots were obtained by means of a microwave-assisted method using glutamic acid and ethylenediamine as reactants. The carbon dots exhibited selective response to Fe3+ ions in aqueous solution with a turn-off mode, and a good linear relationship was found between (F0-F)/F0 and the concentration of Fe3+ in the range of 8-80 μM. As a result, the as-synthesized carbon dots can be developed as a fluorescent chemosensor for Fe3+ in aqueous solution. Moreover, the carbon dots can be applied as a fluorescent agent for fungal bioimaging since the fungal cells stained by the carbon dots were brightly illuminated on a confocal microscopy excited at 405 nm. Furthermore, an increase in the concentration of intracellular Fe3+ could result in fluorescence quenching of the carbon dots in the fungal cells when incubated in the Tris-HCl buffer solution containing Fe3+. However, due to EDTA might hinder Fe(III) to enter the fungal cells, incubation in Fe(III)-EDTA complex solution exerted negligible effect on the fluorescence of fungal cells labeled by the carbon dots. Therefore, the carbon dots can serve as a potential probe for intracellular imaging of Fe3+ inside fungal cells.

A Novel Ruthenium(II) Polypyridyl Complex Bearing 1,8-Naphthyridine as a High Selectivity and Sensitivity Fluorescent Chemosensor for Cu2+ and Fe3+ Ions

A novel ruthenium(II) polypyridyl complex bearing 1,8-naphthyridine was successfully designed and synthesized. This complex was fully characterized by EI-HRMS, NMR, and elemental analyses. The recognition properties of the complex for various metal ions were investigated. The results suggested that the complex displayed high selectivity and sensitivity for Cu²⁺ and Fe³⁺ ions with good anti-interference in the CH₃CN/H₂O (1:1, v/v) solution. The fluorescent chemosensor showed obvious fluorescence quenching when the Cu²⁺ and Fe³⁺ ions were added. The detection limits of Cu²⁺ and Fe³⁺ were 39.9 nmol/L and 6.68 nmol/L, respectively. This study suggested that this Ru(II) polypyridyl complex can be used as a high selectivity and sensitivity fluorescent chemosensor for Cu²⁺ and Fe³⁺ ions.

Live-Cell Imaging of Physiologically Relevant Metal Ions Using Genetically Encoded FRET-Based Probes

Essential biochemical reactions and processes within living organisms are coupled to subcellular fluctuations of metal ions. Disturbances in cellular metal ion homeostasis are frequently associated with pathological alterations, including neurotoxicity causing neurodegeneration, as well as metabolic disorders or cancer. Considering these important aspects of the cellular metal ion homeostasis in health and disease, measurements of subcellular ion signals are of broad scientific interest. The investigation of the cellular ion homeostasis using classical biochemical methods is quite difficult, often even not feasible or requires large cell numbers. Here, we report of genetically encoded fluorescent probes that enable the visualization of metal ion dynamics within individual living cells and their organelles with high temporal and spatial resolution. Generally, these probes consist of specific ion binding domains fused to fluorescent protein(s), altering their fluorescent properties upon ion binding. This review focuses on the functionality and potential of these genetically encoded fluorescent tools which enable monitoring (sub)cellular concentrations of alkali metals such as K⁺, alkaline earth metals including Mg²⁺ and Ca²⁺, and transition metals including Cu⁺/Cu²⁺ and Zn²⁺. Moreover, we discuss possible approaches for the development and application of novel metal ion biosensors for Fe²⁺/Fe³⁺, Mn²⁺ and Na⁺.

Green synthesis of carbon dots using the flowers of Osmanthus fragrans (Thunb.) Lour. as precursors: application in Fe3+ and ascorbic acid determination and cell imaging

In this work, dried flowers of Osmanthus fragrans Lour. were applied as green precursors to synthesize carbon dots (CDs) by a green hydrothermal method for the first time. The CDs showed strong blue fluorescence at 410 nm under 340-nm excitation with a quantum yield of approximately 18.53%. Furthermore, the CDs were applied for the sensitive detection of Fe³⁺. The linear response of Fe³⁺ ranged from 10 nM to 50 μM with a limit of detection as low as 5 nM. In addition, other ions were used as competitive substances to explore the selectivity of CDs for Fe³⁺. The fluorescence quenching effect of Fe³⁺ was much stronger, which demonstrated that the CDs had high selectivity for Fe³⁺ and they can be employed for the selective detection of Fe³⁺. The potential fluorescence quenching mechanism between CDs and Fe³⁺ was identified as the inner filter effect. The CDs were then used as a fluorescent sensor for the detection of Fe³⁺ in water samples and human serum; the recovery range was 93.76-113.80% (relative standard deviation less than 0.79%). These results indicate that the CDs can be applied for the sensitive and selective detection of Fe³⁺ in real samples. Moreover, on the basis of the redox reaction between Fe³⁺ and ascorbic acid (AA), the CD-Fe³⁺ system can be used as a fluorescent "off-on" sensor for the detection of AA with a limit of detection of 5 μM. What is more, because of their low toxicity and biocompatibility, the CDs can also be used for cell imaging and acted as a fluorescent probe for fluorescence imaging of Fe³⁺ and AA in living cells. These results demonstrate that the CDs have great potential for application in the fields of sensing, bioimaging, and even disease diagnosis.

Fe3+ Facilitates Endocytic Internalization of Extracellular Aβ1-42 and Enhances Aβ1-42-Induced Caspase-3/Caspase-4 Activation and Neuronal Cell Death

Amyloid β (Aβ) peptide is a critical causative factor in Alzheimer's disease (AD) and of a variety of fragmented Aβ peptides Aβ_1-42 thought to exhibit the most neurotoxic effect. The present study investigated the effects of Fe³⁺ on Aβ_1-42 internalization and Aβ_1-42-induced caspase activation and neurotoxicity using mouse hippocampal slices and cultured PC-12 cells. Extracellularly applied Aβ_1-42 increased the cell-associated Aβ_1-42 levels in a concentration-dependent manner, and the effect was enhanced by adding Fe³⁺. Fe³⁺-induced enhancement of the cell-associated Aβ_1-42 levels was significantly inhibited by the endocytosis inhibitors dynasore and methyl-β-cyclodextrin. Aβ_1-42 reduced PC-12 cell viability in a concentration-dependent manner, and further reduction of the cell viability was obtained with Fe³⁺. Aβ_1-42-induced reduction of cell viability was not affected by A187, an antagonist of amylin-3 receptor. Aβ_1-42 activated caspase-3, caspase-4, and caspase-8 to a variety of degrees and Fe³⁺ further enhanced Aβ_1-42-induced activation of caspase-3 and caspase-4. Taken together, these results indicate that Fe³⁺ accelerates endocytic internalization of extracellular Aβ_1-42, enhances Aβ_1-42-induced caspase-3/caspase-4 activation, and promotes Aβ_1-42-induced neuronal cell death, regardless of amylin receptor.

Using Magnetic Ions to Probe and Induce Magnetism of Pyrophosphates, Bacteria, and Mammalian Cells

Magnetic isolation using magnetic nanoparticles (MNPs) as trapping probes have been widely used in sample pretreatment to shorten analysis time. Nevertheless, to generate MNPs is time-consuming. Furthermore, the generated MNPs have to be further functionalized to gain the capability of recognizing their target species. Thus, an alternative approach that can impose magnetism to nonmagnetic species by simply using magnetic ions as the probes is developed in this study. That is, we employ magnetic ions (Fe³⁺, Co²⁺, and Ni²⁺) that can interact with nonmagnetic species containing oxygen-containing functional groups as the probes. Pyrophosphate (PPi), bacteria, and mammalian cells were selected as the model samples. Our results show that the as-prepared magnetic ion-PPi conjugates gain sufficient magnetism and can be readily aggregated by applying an external magnetic field. Moreover, the magnetic trapping is reversible. The PPi-containing conjugates can lose their magnetic property simply using ethylenediaminetetraacetic acid or aluminum ions as competing agents to remove or to replace, respectively, the conjugated magnetic ions. In addition, bacteria and mammalian cells that possess abundant oxygen-containing functional groups on their cell surfaces can be selectively probed by magnetic ions and gain sufficient magnetism for magnetic isolation from complex serum samples.

Influence of Sb5+ as a Double Donor on Hematite (Fe3+) Photoanodes for Surface-Enhanced Photoelectrochemical Water Oxidation

To exploit the full potential of hematite (α-Fe₂O₃) as an efficient photoanode for water oxidation, the redox processes occurring at the Fe₂O₃/electrolyte interface need to be studied in greater detail. Ex situ doping is an excellent technique to introduce dopants onto the photoanode surface and to modify the photoanode/electrolyte interface. In this context, we selected antimony (Sb⁵⁺) as the ex situ dopant because it is an effective electron donor and reduces recombination effects and concurrently utilize the possibility to tuning the surface charge and wettability. In the presence of Sb⁵⁺ states in Sb-doped Fe₂O₃ photoanodes, as confirmed by X-ray photoelectron spectroscopy, we observed a 10-fold increase in carrier concentration (1.1 × 10²⁰ vs 1.3 × 10¹⁹ cm^-3) and decreased photoanode/electrolyte charge transfer resistance (∼990 vs ∼3700 Ω). Furthermore, a broad range of surface characterization techniques such as Fourier-transform infrared spectroscopy, ζ-potential, and contact angle measurements reveal that changes in the surface hydroxyl groups following the ex situ doping also have an effect on the water splitting capability. Theoretical calculations suggest that Sb⁵⁺ can activate multiple Fe³⁺ ions simultaneously, in addition to increasing the surface charge and enhancing the electron/hole transport properties. To a greater extent, the Sb⁵⁺- surface-doped determines the interfacial properties of electrochemical charge transfer, leading to an efficient water oxidation mechanism.

A Resumable Fluorescent Probe BHN-Fe3O4@SiO2 Hybrid Nanostructure for Fe3+ and its Application in Bioimaging

A multifunctional fluorescent probe BHN-Fe₃O₄@SiO₂ nanostructure for Fe³⁺ was designed and developed. It has a good selective response to Fe³⁺ with fluorescence quenching and can be recycled using an external magnetic field. With adding EDTA (2.5 × 10^-5 M) to the consequent product Fe³⁺-BHN-Fe₃O₄@SiO₂, Fe³⁺ can be removed from the complex, and its fluorescence probing ability recovers, which means that this constituted on-off type fluorescence probe could be reversed and reused. At the same time, the probe has been successfully applied for quantitatively detecting Fe³⁺ in a linear mode with a low limit of detection 1.25 × 10^-8 M. Furthermore, the BHN-Fe₃O₄@SiO₂ nanostructure probe is successfully used to detect Fe³⁺ in living HeLa cells, which shows its great potential in bioimaging detection.

Study of DNA damage caused by dipyrone in presence of some transition metal ions

The DNA damage in the presence of dipyrone (used as its sodium salt, NaDip) and some transition metal ions in an air saturated ([O₂] ≈ 0.25 mM) non-buffered solution at T = (25.0 ± 0.5)°C was investigated by agarose gel electrophoresis. As metal ions Cu²⁺, Fe³⁺, Ni²⁺ and Mn³⁺ were selected and evaluated in the present study because of the important role they play in a biological system. pUC19 plasmid DNA damage-induced by NaDip (80-600 μM) was observed in the presence of 100 μM Cu²⁺. The damage was proportional to the NaDip concentration provided that the order of addition of reagents (pUC19 plasmid DNA + Cu²⁺ + NaDip) is obeyed. Addition in the reaction medium of ligands for Cu²⁺ and Cu⁺, respectively EDTA and neocuproine, promoted total inhibition or reduction of the pUC19 plasmid DNA damage suggesting the involvement of the Cu²⁺/Cu⁺ cycle. Besides, the decrease in the pUC19 plasmid DNA damage after addition of catalase (1.0 × 10^-4 mg μL^-1) in the same reaction medium indicates that H₂O₂ is also involved in the damage process. In NaDip concentration range (80-600 μM), and under same the experimental conditions, it was not possible to conclude whether there was pUC19 plasmid DNA damage caused by 10 μM Fe³⁺. No damage was observed in the presence of Mn³⁺ or Ni²⁺. Although the technique used in this study is sensitive to detect the pUC19 plasmid DNA damage it was not possible to identify in which DNA base this damage occurs. Further studies with other techniques should be made to unambiguously identify the oxidative intermediates that are responsible for the DNA damage. As far as we know, this is the first study dealing with the pUC19 plasmid DNA damage-induced by NaDip in presence of copper, iron, nickel and manganese ions.

Facile synthesis of N-rich carbon quantum dots from porphyrins as efficient probes for bioimaging and biosensing in living cells

N-rich metal-free and metal-doped carbon quantum dots (CQDs) have been prepared through one-step hydrothermal method using tetraphenylporphyrin or its transition metal (Pd or Pt) complex as precursor. The structures and morphology of the as-prepared nanoparticles were analyzed by X-ray diffraction, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, and Fourier transform infrared spectra. Three kinds of nanocomposites show similar structures except for the presence of metal ions in Pd-CQDs and Pt-CQDs indicated by X-ray photoelectron spectroscopy. All of them display bright blue emission upon exposure to ultraviolet irradiation. The CQDs exhibit typical excitation-dependent emission behavior, with the emission quantum yield of 10.1%, 17.8%, and 15.2% for CQDs, Pd-CQDs, and Pt-CQDs, respectively. Moreover, the CQDs, Pd-CQDs, and Pt-CQDs could serve as fluorescent probes for the specific and sensitive detection of Fe3+ ions in aqueous solution. The low cytotoxicity of CQDs is demonstrated by MTT assay against HeLa cells. Therefore, the CQDs can be used as efficient probes for cellular multicolor imaging and fluorescence sensors for the detection of Fe3+ ions due to their low toxicity, excellent biocompatibility, and low detection limits. This work provides a new route to synthesize highly luminescent N-rich metal-free or metal-doped CQDs for multifunctional applications.