An effective procedure used metal-organic framework for determination of cadmium ions in real tap water and human blood plasma samples.

A newly developed 2H5MA-MOF sensor by covalently linking NH2-MIL-53(Al) with 2'-Hydroxy-5'-methylacetophenon, designed for highly sensitive and selective detection of Cd2+ ions using fluorometric methods. Detailed structural and morphological analyses confirmed the sensor's unique properties. It demonstrated an impressive linear detection range from 0 to 2 ppm, with an exceptionally low detection limit of 5.77 × 10-2 ppm and a quantification limit of 1.75 × 10-1 ppm, indicating its high sensitivity (R2 = 0.9996). The sensor also responded quickly, detecting Cd2+ within just 30 s at pH 4. We successfully tested it on real samples of tap water and human blood plasma, achieving recovery rates between 96 % and 104 %. The accuracy of these findings was further validated by comparison with ICP-OES. Overall, the 2H5MA-MOF sensor shows great potential for fast, ultra-sensitive, and reliable detection of Cd2+ ions, making it a promising tool for environmental and biomedical applications.

Machine learning-assisted fluorescence visualization for sequential quantitative detection of aluminum and fluoride ions.

The presence of aluminum (Al3+) and fluoride (F-) ions in the environment can be harmful to ecosystems and human health, highlighting the need for accurate and efficient monitoring. In this paper, an innovative approach is presented that leverages the power of machine learning to enhance the accuracy and efficiency of fluorescence-based detection for sequential quantitative analysis of aluminum (Al3+) and fluoride (F-) ions in aqueous solutions. The proposed method involves the synthesis of sulfur-functionalized carbon dots (C-dots) as fluorescence probes, with fluorescence enhancement upon interaction with Al3+ ions, achieving a detection limit of 4.2 nmol/L. Subsequently, in the presence of F- ions, fluorescence is quenched, with a detection limit of 47.6 nmol/L. The fingerprints of fluorescence images are extracted using a cross-platform computer vision library in Python, followed by data preprocessing. Subsequently, the fingerprint data is subjected to cluster analysis using the K-means model from machine learning, and the average Silhouette Coefficient indicates excellent model performance. Finally, a regression analysis based on the principal component analysis method is employed to achieve more precise quantitative analysis of aluminum and fluoride ions. The results demonstrate that the developed model excels in terms of accuracy and sensitivity. This groundbreaking model not only showcases exceptional performance but also addresses the urgent need for effective environmental monitoring and risk assessment, making it a valuable tool for safeguarding our ecosystems and public health.

Unveiling Potassium and Sodium Ion Dynamics in Living Plants with an In-Planta Potentiometric Microneedle Sensor.

Potassium and sodium ions (K+ and Na+) play crucial roles in influencing plant growth and health status. Unfortunately, current strategies to determine the concentrations of such ions are destructive for the plants because it is necessary to collect/extract the sap for further analysis and produce either scattered or delayed results. Here, we introduce a new potentiometric dual microneedle sensor for nondestructive, real-time, and continuous monitoring of K+ and Na+ concentrations in living plants. The developed sensors show a response time <5 s, close-to-Nernstian slope (∼55 mV dec-1), resiliency to five insertions on the stem, good repeatability (max. %RSD = 0.3%) and reversibility (max. %RSD = 3%), appropriate continuous operation for 24 h, and linear range of responses that cover expected plant physiological levels (5-50 mM for Na+ and 50-120 mM for K+). Moreover, the accuracy was successfully investigated by comparing the results provided by the microneedle sensors to those obtained by a standard reference method (e.g., ion chromatography). Finally, we demonstrate that the developed analytical device is capable of tracking K+ and Na+ transportation from the hydroponic solution to the stem within 5-10 min. This research will contribute to establishing a new generation of analytical platforms for smart agriculture offering real-time information.

Highly sensitive detection of Pb2+ with a non-contact, near-infrared responsive hydrogel-functionalized optical fiber sensor.

Most sensors use acidic eluent to realize the desorption of Pb2+, which inevitably causes damage to the sensing membrane. A near-infrared responsive hydrogel sensing membrane (PNIPAm/PVA/GO) was prepared by free radical polymerization, which was modified on U-shaped optical fiber sensors for the selective determination of Pb2+. Graphene oxide (GO) is the functional recognition monomer, and the double-crosslinked network of polyvinyl alcohol (PVA) and Poly(N-isopropylacrylamide) (PNIPAm) acts as the mechanical stress skeleton while increasing the Pb2+ adsorption sites and inhibiting the agglomeration of GO. The "self-healing" of the sensing membrane achieves non-destructive desorption without causing secondary pollution to the environment by utilizing the high photothermal conversion efficiency of GO and the temperature response characteristics of PNIPAm. The sensor exhibited a sensitivity of 0.2191 nm/ppb in the 0-100 ppb range; the limit of detection was calculated to be 0.27 ppb. The experimental results show that the sensor has good reproducibility, stability, and selectivity. Further, the proposed signal analysis method based on convolutional neural networks realizes the measurement of Pb2+ at different pH values. This method can effectively solve the problem of increased selectivity while leading to desorption difficulties and provides a new idea for realizing green, clean, and efficient detection of Pb2+.

Nitrogen and Sulfur Co-doped Carbon Dots for Ratiometric Fluorometric Determination of Mercury Ions.

Nitrogen and sulfur co-doped carbon dots (N, S-CDs) were prepared for dual-channel ratiometric fluorescence determination of mercury ions (Hg2+). The dual-emission N, S-CDs were synthesized using a simple one-pot hydrothermal treatment. When excited with visible light, N,S-CDs exhibited two emission peaks at 390 and 500 nm. Notably, the presence of Hg2+ caused a considerable decrease in the fluorescence of N, S-CDs at 500 nm, mainly due to the static quenching effect. In comparison, the fluorescence at 390 nm was almost unchanged. With a limit of detection (LOD) of 0.21 µM for Hg2+, the N, S-CDs were successfully applied to the unlabeled ratiometric fluorescence determination of Hg2+ in actual water samples with good recoveries (94.5-107.8%). In conclusion, this developed ratiometric fluorescent sensor provides a reliable, environmentally friendly, rapid, and efficient platform for detecting Hg2+ in environmental applications.

Emerging insights into the application of metal-organic framework (MOF)-based materials for electrochemical heavy metal ion detection.

Heavy metal ions are one of the main sources of water pollution, which has become a major global problem. Given the growing need for heavy metal ion detection, electrochemical sensor stands out for its high sensitivity and efficiency. Metal-organic frameworks (MOFs) have garnered much interest as electrode modifiers for electrochemical detection of heavy metal ions owing to their significant specific surface area, tailored pore size, and catalytic activity. This review summarizes the progress of MOF-based materials, including pristine MOFs and MOF composites, in the electrochemical detection of various heavy metal ions. The synthetic methods of pristine MOFs, the detection mechanisms of heavy metal ions and the modification strategies of MOFs are introduced. Besides, the diverse applications of MOF-based materials in detecting both single and multiple heavy metal ions are presented. Furthermore, we present the current challenges and prospects for MOF-based materials in electrochemical heavy metal ion detection.

Synthesis of fluorometric carbon nano dots(CNDs) for selective sensing of biologically important Fe3+ and Cu2+ metal ions and evaluating their antioxidant capacity.

In this research, CNDs were prepared by a green and cost effective method using Cinnamomum Tamala (bay leaf) as carbon sources. TEM, UV, FTIR, ZETA Potential, PL and Fluorescence methods were used to characterize the produced CNDs and the average particle size is 3.42 nm. This research was conducted on the development of fluorescent sensors for various metal ions, including Fe3+, Cu2+, Zn2+, Ni2+, Pb2+, Cr3+, Mg2+, Na+ 1 and Cd2+. The CNDs demonstrated selective sensing of biologically important Fe+ 3 and Cu+ 2 metal ions. The CNDs antioxidant assay was tasked with DPPH• radical scavenging properties. CNDs made from Cinnamomum Tamala had the highest DPPH free radical scavenging activity at 100 mg/L (42.06%) with the IC50 of 130.68 mg/L. The outcome implies that Indian spices are among the best materials for optical metal ion detection and sensing, and they also have therapeutic benefits.

Highly efficient removal and real-time visual detection of fluoride ions using ratiometric CAU-10-NH2@RhB: Probe design, sensing performance, and practical applications.

The extensive use of fluoride in agriculture, industry, medicine, and daily necessities has raised growing concerns about fluoride residue. To date, real-time visual detection and efficient removal of fluoride ions from water remain greatly desirable. Herein, nano-CAU-10-NH2@RhB is introduced as a ratiometric fluorescent probe and efficient scavenger for the intelligent detection and removal of fluoride ions. CAU-10-NH2@RhB is readily obtained through one-pot synthesis and exhibits high sensitivity and selectivity for real-time fluoride ion detection, with a naked-eye distinguishable color change from pink to blue. A portable device for point-of-care testing was developed based on color hue analysis readout using a smartphone. A quantitative response was achieved across a wide concentration range, with a detection limit of 54.2 nM. Adsorption experiments suggest that nano-CAU-10-NH2@RhB serves as an efficient fluoride ion scavenger, with a fluoride adsorption capacity of 49.3 mg/g. Moreover, the mechanistic study revealed that hydrogen bonds formed between fluoride ions and amino groups of CAU-10-NH2@RhB are crucial for the detection and adsorption of fluoride ions. This analysis platform was also used for point-of-care quantitative visual detection of fluoride ions in food, water, and toothpaste.

An ultrasensitive electrochemical method for rapid detection of mercury based on nanoporous gold capped with a novel Zr-MOF-SH/reduced graphene oxide aerogel composites.

In this work, an ultrasensitive electrochemical sensor based on Zr-MOF-SH/rGA/NPG was developed for the first time for the rapid determination of mercury ions. First, nanoporous gold (NPG) film was covered on the glassy carbon electrode (GCE) to offer a desirable substrate. Then, Zr-MOF-SH/rGA composites were dropped on the NPG film to form a modified electrode. Mercapto functionalized MOFs (Zr-MOF-SH) showed strong adsorption capability toward mercury ions, and the unique structure of reduced graphene oxide aerogel (rGA) provided various sites for coupling with Zr-MOF-SH as well as improved the electrochemical activity. As a consequence of the synergistic effect of Zr-MOF-SH, rGA, and NPG, the optimized Zr-MOF-SH/rGA/NPG/GCE sensor showed excellent detection performance toward mercury ions with a linear range from 0 to 200 nM and a low limit of detection of 1.4 nM. Meanwhile, the fabricated electrochemical sensor exhibited outstanding stability, reproducibility, and anti-interference ability. To verify the practical applicability, the Zr-MOF-SH/rGA/NPG/GCE was applied for the determination of mercury ions in real rice samples with desirable recovery rates ranging from 98.8% to 108.3%.

Enhanced Stability and Detection Range of Microbial Electrochemical Biotoxicity Sensor by Polydopamine Encapsulation.

With the rapid development of modern industry, it is urgently needed to measure the biotoxicity of complex chemicals. Microbial electrochemical biotoxicity sensors are an attractive technology; however, their application is usually limited by their stability and reusability after measurements. Here, we improve their performance by encapsulating the electroactive biofilm with polydopamine (PDA), and we evaluate the improvement by different concentrations of heavy metal ions (Cu2+, Ag+, and Fe3+) in terms of inhibition ratio (IR) and durability. Results indicate that the PDA-encapsulated sensor exhibits a more significant detection concentration than the control group, with a 3-fold increase for Cu2+ and a 1.5-fold increase for Ag+. Moreover, it achieves 15 more continuous toxicity tests than the control group, maintaining high electrochemical activity even after continuous toxicity impacts. Images from a confocal laser scanning microscope reveal that the PDA encapsulation protects the activity of the electroactive biofilm. The study, thus, demonstrates that PDA encapsulation is efficacious in improving the performance of microbial electrochemical biotoxicity sensors, which can extend its application to more complex media.

Highly Sensitive and Selective Recognition of Zn2⁺ and Fe2⁺ Ions Using a Novel Thiophene-Derived Hydrazone Dual Fluorometric Sensor.

The selective detection of Zn2⁺ and Fe2⁺ ions is critical in environmental and biological studies. Schiff base chemosensors hold promise, but exploration of thiophene-derived variants remains limited. This work introduces a novel thiophene-derived Schiff base sensor (TBH), synthesized through the condensation reaction of thiophene-2-carboxaldehyde with benzil-bis-hydrazone, for the selective detection of Zn2⁺ and Fe2⁺ ions. TBH exhibits remarkable selectivity, with a significant 185-fold fluorescence enhancement for Zn2⁺ and complete quenching 99% for Fe2⁺, allowing for distinct detection of both ions. Notably, TBH demonstrates high binding affinity towards Zn2⁺ and Fe2⁺, even in the presence of competing cations, forming stable 1:1 complexes. This finding is supported by absorption and emission titration studies and FT-IR analysis as well. This easily synthesized, rapid and cost-effective sensor offers a promising approach for sensitive and differentiated dual detection of Zn2⁺ and Fe2⁺ in environmental and biological systems.

A Review on Small Molecule Based Fluorescence Chemosensors for Bioimaging Applications.

This review provides a thorough examination of small molecule-based fluorescence chemosensors tailored for bioimaging applications, showcasing their unique ability to visualize biological processes with exceptional sensitivity and selectivity. It explores recent advancements, methodologies, and applications in this domain, focusing on various designs rooted in anthracene, benzothiazole, naphthalene, quinoline, and Schiff base. Structural modifications and molecular engineering strategies are emphasized for enhancing sensor performance, including heightened sensitivity, selectivity, and biocompatibility. Additionally, the review offers valuable insights into the ongoing development and utilization of these chemosensors, addressing current challenges and charting future directions in this rapidly evolving field.

A Terbium Ion-Based Dual-Ligand Fluorescent Probe for Highly Selective and Sensitive Detection of Cu2+ Ions.

In this study, a fluorescent probe (GMP-Tb-SSA) utilizing lanthanide coordination polymer nanoparticles, GMP-Tb, as a sensing platform, and 5-sulfosalicylic acid (SSA) as a cofactor ligand was proposed for the detection of copper ions (Cu2+). GMP-Tb was synthesized by the self-assembly of guanine monophosphate (GMP) and terbium ion (Tb3+), and SSA was introduced as a sensitizer into the GMP-Tb network. Cu2+ could efficiently inhibit the electron transfer from the ligand GMP to the central ion, Tb3+, leading to a significant quench of fluorescence of Tb3+. The method is highly selective with a linear range of 0 to 21 µM and a detection limit of 300 nM. It is not interfered by metal ions, amino acids, and other species, and can be successfully applied to the detection of Cu2+ in real water samples.

Highly sensitive and highly selective lead ion electrochemical sensor based on zn/cu-btc-nh2 bimetallic MOFs with nano-reticulated reinforcing microstructure.

Identifying ultra-trace amounts of divalent lead ions (Pb2+) with high response and selectivity, continues to be a pressing issue in identifying environmental pollutants and preventing health complications. This paper details how the in-situ electrodeposited Zn/Cu-BTC-NH2 metal-organic frameworks (MOFs) boosts Pb2+ concentration for amino adsorption and facilitates ion transfer between Cu element and Pb2+. The modified coating of the glassy carbon electrode (GCE) exhibits a unique nano-reticulated structure loaded with octahedron particles, the nano-reticulated structure ensures the structural strength of the modified electrode layer, while the loaded octahedral particles enhancing electrocatalytic activity. The ultra-trace detection of Pb2+ at concentrations below µg·L-1 is accomplished by using the square wave anodic stripping voltammetry (SWASV) method, the fabricated Zn/Cu-BTC-NH2 modified electrode signifies a detection threshold of 0.021 µg L-1 and a clearly ascending linear interval prior to the rise in Pb2+ concentration to 120 µg L-1. The reported electrochemical method for the precise identification of Pb2+ in water-based solutions offers a practical approach for modifying MOFs materials and detecting heavy metal ions.

Highly sensitive hydrolytic nanozyme-based sensors for colorimetric detection of aluminum ions.

Hydrolytic nanozyme-based visual colorimetry has emerged as a promising strategy for the detection of aluminum ions. However, most studies focus on simulating the structure of natural enzymes while neglecting to regulate the rate of hydrolysis-related steps, leading to low enzyme-like activity for hydrolytic nanozymes. Herein, we constructed a ruthenium dioxide (RuO2) in situ embedded cerium oxide (CeO2) nanozyme (RuO2/CeO2) with a Lewis acid-base pair (Ce-O-Ru-OH), which can simulate the catalytic behavior of phosphatase (PPase) and can be quantitatively quenched by Al3+ to achieve accurate and sensitive Al3+ colorimetric sensing detection. The incorporation of Ru into CeO2 nanorods accelerates the dissociation of H2O, followed by subsequent combination of hydroxide species to Lewis acidic Ce-O sites. This synergistic effect facilitates substrate activation and significantly enhances the hydrolysis activity of the nanozyme. The results show that the RuO2/CeO2 nanozyme exhibits a limit of detection as low as 0.5 ng/mL. We also demonstrate their efficacy in detecting Al3+ in various practical food samples. This study offers novel insights into the advancement of highly sensitive hydrolytic nanozyme engineering for sensing applications.

Detecting Pb2+ in aqueous environment and live cells by amphiphilic pillar[5]arene-assembled supramolecular sensor based on host-guest charge transfer mechanism.

Water-soluble fluorescent chemosensors for lead ion are highly desirable in environmental detection and bioimagery. Based on a water-soluble pillar[5]arene WP5 and imidazolium terminal functionalized 2,2'-bibenzimidazole derivative BIHB, we report a host-guest charge transfer assembly BIHB-2WP5 for sensitive and selective detection of Pb2+ in pure aqueous media. As a result of its high electron-rich cavity, WP5 can bind electron-deficiency guest BIHB with various host/guest stoichiometry to easily tune the microtopography of assembly from nanoparticle to nanocube. In view of the good biocompatibility and sensitivity, the supramolecular assembly BIHB-2WP5 was used as a fluorescent probe for the detection of Pb2+ in living cells and a smartphone Pb2+ detection device was constructed for the in situ test.

Recent advances in isatin-based chemosensors: A comprehensive review.

A comprehensive review presents an illuminating exploration of the vast potential of isatin, an easily accessible organic compound. This review is a valuable resource, offering a concise yet comprehensive account of the recent breakthroughs in isatin applications in medicinal chemistry, fluorescence sensing, and organic synthesis. Moreover, it dives into the exciting advancements in isatin-based chemosensors, demonstrating their remarkable ability to detect and recognize diverse cations and anions with exceptional precision. Researchers and scientists in the fields of sensing and organic chemistry will find this review indispensable for sparking innovation and developing cutting-edge technologies with significant real-world impact.

Ionic Organic Network-based C3-symmetric@Triazine core as a selective Hg+2 sensor.

The C3-symmetry ionic polymer PPyTri has been designed with multi-walled carbon nanotubes (MWCNTs) or graphene nanoplatelets (GNPs) and studied as an ultrasensitive electrochemical sensor for trace Hg(II) detection. The synthesis approach incorporated attaching three pyridinium cationic components with chloride anions to the triazine core. The precursors, BPy, were synthesized using a condensation process involving 4-pyridine carboxaldehyde and focused nicotinic hydrazide. The polymer PPyTri was further modified with either MWCNTs or GNPs. The resulting ionic polymer PPyTri and its fabricated nanocomposites were characterized using infrared (IR), nuclear magnetic resonance (NMR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and powder X-ray diffraction (XRD). The analysis revealed that both the polymer and its nanocomposites have semi-crystalline structures. The electroactivity of the designed nanocomposites toward Hg + 2 ions revealed that among the nanocomposites and bare copolymer, the glassy carbon electrode (GCE) adapted with the PPyTri GNPs-5% exhibited the greatest current response over a wide range of Hg + 2 concentrations. The nanocomposite-modified electrode presented an excellent sensitivity of 83.33 µAµM - 1 cm - 2, a low detection limit of 0.033 nM, and a linear dynamic range of 0.1 nM to 0.01 mM (R2 = 0.9945).

Hectorite/Phenanthroline-Based Nanomaterial as Fluorescent Sensor for Zn Ion Detection: A Theoretical and Experimental Study.

The development of fluorescent materials that can act as sensors for the determination of metal ions in biological fluids is important since they show, among others, high sensitivity and specificity. However, most of the molecules that are used for these purposes possess a very low solubility in aqueous media, and, thus, it is necessary to adopt some derivation strategies. Clay minerals, for example, hectorite, as natural materials, are biocompatible and available in large amounts at a very low cost that have been extensively used as carrier systems for the delivery of different hydrophobic species. In the present work, we report the synthesis and characterization of a hectorite/phenanthroline nanomaterial as a potential fluorescent sensor for Zn ion detection in water. The interaction of phenanthroline with the Ht interlaminar space was thoroughly investigated, via both theoretical and experimental studies (i.e., thermogravimetry, FT-IR, UV-vis and fluorescence spectroscopies and XRD measurements), while its morphology was imaged by scanning electron microscopy. Afterwards, the possibility to use it as sensor for the detection of Zn2+ ions, in comparison to other metal ions, was investigated through fluorescent measurements, and the stability of the solid Ht/Phe/Zn complex was assessed by different experimental and theoretical measurements.

Multifunctional Antimonene-Silver Nanocomposites for Ultra-Multi-Mode and Multi-Analyte Sensing, Parallel and Batch Logic Computing, Long-Text Information Protection.

To simulate life's emergent functions, mining the multiple sensing capabilities of nanosystems, and digitizing networks of transduction signals and molecular interactions, is an ongoing endeavor. Here, multifunctional antimonene-silver nanocomposites (AM-Ag NCs) are synthesized facilely and fused for molecular sensing and digitization applications (including ultra-multi-mode and multi-analyte sensing, parallel and batch logic computing, long-text information protection). By mixing surfactant, AM, Ag+ and Sodium borohydride (NaBH4) at room temperature for 5 min, the resulting NCs are comprised of Ag nanoparticles scattered within AM nanosheets and protected by the surfactant. Interestingly, AM-Ag NCs exhibit ultra-multi-mode sensing ability for multiplex metal ions (Hg2+, Fe3+, or Al3+), which significantly improved selectivity (≈2 times) and sensitivity (≈400 times) when analyzing the combined channels. Moreover, multiple sensing capabilities of AM-Ag NCs enable diverse batch and parallel molecular logic computations (including advanced cascaded logic circuits). Ultra-multi-mode selective patterns of AM-Ag NCs to 18 kinds of metal ions can be converted into a series of binary strings by setting the thresholds, and realized high-density, long-text information protection for the first time. This study provides new ideas and paradigms for the preparation and multi-purpose application of 2D nanocomposites, but also offers new directions for the fusion of molecular sensing and informatization.