Detection In Real Water Samples Research Articles

Hierarchical flower-like ytterbium benzene-1,3,5-tricarboxylate metal organic framework for simultaneous sensitive electrochemical detection of Cd2+, Pb2+ and Cu2+

Hierarchical electrochemical sensors with specific recognition function have been widely applied for trace amounts detection of metal ions, showing great significance for monitoring environmental quality. Herein, a novel flower-like ytterbium benzene-1,3,5-tricarboxylate metal-organic framework (Yb-MOF-1) was prepared by a one-step solvothermal method, which was then cast on a glassy carbon electrode to construct a sensing platform. Compared to the traditional rod-like Yb-MOF-2 prepared at a lower pH (pH = 4.26), the Yb-MOF-1 assembled from ultrathin nanosheets has a large surface area (462.356 m²/g), showing simultaneous electrochemical detection performance towards Cd2+, Pb2+ and Cu2+ in aqueous solution with detection limits of 9.22, 1.69, 15.15 nM, respectively. The experimental results demonstrate its good anti-interference and repeatability. The reliable practical application of Yb-MOF-1 for Cd2+, Pb2+ and Cu2+ detection in real water samples shows good recovery rates ranging from 95.8 % to 103.5 %, proving the effective strategy in exploring efficient electrochemical sensing materials.

Nanostructured TiO2-X/CuXO-based electrochemical sensor for ultra-sensitive glyphosate detection in real water samples

Glyphosate, a widely employed non-selective pesticide for enhancing crop productivity through weed control, poses significant health and environmental concerns due to its potential link to chronic diseases, cancers, and disruptions in natural symbiotic relationships. Quantifying glyphosate values becomes imperative for effective monitoring and mitigation of associated risks. In response, a novel electrochemical sensor was developed utilizing nanostructured TiO2 films modified with Ti3+ ions and copper oxides for precise detection and quantification of glyphosate in real water samples. The nanotubular structure, synthesized via potentiostatic anodization, underwent further modification through cathodic reduction of Ti3+ ions and copper electrodeposition. Under optimal experimental conditions, the sensor exhibited a notable ability to detect glyphosate traces by inhibiting peak current in Differential Pulse Voltammetry (DPV). It achieved low limits of detection (LOD = 0.34 pmol/L) and quantification (LOQ = 0.70 pmol/L) within a linear working range of 0.55 to 1000.00 pmol/L. The sensor demonstrated robust stability and excellent precision (repeatability and intermediate precision) without significant variations in analytical response and yielded recovery rates ranging from 91.06 to 99.38 %. These promising results underscore the sensor’s potential application for detecting glyphosate in real aquatic matrices, contributing to effective environmental monitoring and health protection.

A platform for microplastic assessment in aquatic environments based on the protein corona-induced aggregation effect

The environmental hazards of microplastics have received widespread attention. However, the in-situ detection of microplastics, particularly in aquatic environments, has been challenged by the limitations of detection methods, the large-scale instruments, and small size. Herein, a photoelectrochemical sensor based on the protein corona-induced aggregation effect is designed for the detection of polystyrene microplastics. The sensor has advantages of high sensitivity, reproducibility, and detection capability. A linear detection range of 0.5–500 μg mL−1, a method detection limit of 0.06 μg mL−1, and a limit of quantification of 0.14 μg mL−1 are achieved. Furthermore, the relative standard deviations of intra-day and inter-day precision, ranging from 0.56% to 4.63% and 0.84%–3.36% are obtained. A digital multimeter was employed to construct a platform for the real-time detection in real water samples, streamlining the detection process and yielding clear results. We believe this sensor provides new insight for the in-situ real-time detection of microplastics and has broad applications for the analysis of microplastic pollution in aquatic environments.

An ICT-based highly fluorescent isoquinoline scaffold for selective Hg(II) detection in real-water samples: Development of a smart, low-cost RGB-Arduino electronic platform

Selective detection and quantification of Hg2+ ions is crucial to minimize health and environmental risks. Fluorescent organic small-molecule probes have been expeditiously utilized owing to their unique set of improved properties. However, isoquinoline core has not been extensively explored as a fluorescence platform partly due to synthetic challenges. Herein, a serendipitously discovered synthetic route to access a small yet highly functionalized novel isoquinoline-based probe, IQ is reported. The synthesis is achieved through the in-situ generation of ammonia, followed by intermolecular [5C + 1 N] aza-annulation reaction with a ketendithioacetal-based precursor, P-IQ. IQ displayed excellent recognition ability towards Hg2+ ions in H2O:ACN (99:1, v/v) via ICT-off fluorescent quenching behavior. Comparative FT-IR, 1H/13C NMR, mass spectral studies, and DFT analyses were carried out to validate the suggested mechanisms. Reversible studies confirm the secondary recognition effect of in-situ generated (IQ + Hg2+) complex on cysteine. The binding constant and LOD were estimated to be 3.7 × 104 M−1 and 0.86 µM, respectively. Further, IQ was utilized to evaluate the mercury ion content in real water samples demonstrating its effectiveness in water quality monitoring. The practical utility of IQ was further explored by developing TLC strips, Whatman filter-paper strips, and a low-cost, portable Arduino-based platform. Arduino microcontroller is interfaced with an RGB sensor to detect color changes and quantify mercury concentration w.r.t. RGB values.

A highly sensitive and selective rhodamine-semicarbazide based fluorescent sensor for Cu2+ detection in real water samples and fluorescence bioimaging in HepG2 cells

A colorimetric and fluorescent sensor, selective for Cu2+ ions, was synthesized in two steps using a rhodamine-based compound attached to the semicarbazide-picolylamine moiety (RBP). Spectroscopic measurements, including UV–Vis absorption and fluorescence emission, were conducted in the semi-aqueous medium containing acetonitrile/4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid, denoted as MeCN/HEPES buffer (2:8, v/v, pH 7.0). The sensor exhibited high selectivity towards Cu2+ ions compared to other cations and demonstrated remarkable sensitivity towards Cu2+ ions, with a limit of detection at the nanomolar level. The calculated transitions indicated a 1:1 stoichiometric binding of RBP to Cu2+ ions based on a 4-coordination mode involving additional chelation in the semi-aqueous medium. The sensing mechanism for the detection of Cu2+ ions was investigated using high-resolution mass spectroscopy. The sensor could be employed as a real-time chemosensor for monitoring Cu2+ ions. Furthermore, the sensor has the potential for utilization in the detection of Cu2+ ions in actual water samples with the high precision and accuracy, as indicated by the small relative standard derivation values. The 50th percentile cytotoxicity concentration of RBP was found to be 22.92 μM. Additionally, the fluorescence bioimaging capability of RBP was demonstrated for the detection of Cu2+ ions in human hepatocellular carcinoma (HepG2) cells.

A novel ratiometric fluorescence probe based on calix[4]arene functionalized polymer dots for bisphenol A detection in real water samples

Bisphenol A (BPA) is one of key raw materials used in the production of epoxy resins and plastics, which has toxicological effects on humans by disrupting cell functions through a variety of cell signaling pathways. Therefore, it is of great significance to develop a simple, rapid, and accurate BPA detection method in real water samples. In this study, a ratiometric fluorescence method based on yellow-emitting surface-functionalized polymer dots (PFBT@L Pdots) and blue-emitting carbon dots (Cdots) was described for the detection of BPA. Pdots as the detecting part were synthesized by using highly fluorescent hydrophobic Poly[(9,9-dioctylfluorenyl-2,7-diyl)-alt-co-(1,4-benzo-(2,1′,3)-thiadiazole)] (PFBT) polymer and (R)-5,11,17,23-Tetra-tert-butyl-25,27-bis[(diphenylphosphinoyl)methoxy]-26-(3-oxabutyloxy)-28-[(1-phenylethyl)- carbamoylmethoxy]calix [4]arene (L) functionalizing ligand, and Cdots as internal reference were prepared by hydrothermal treatment of citric acid and urea. In the presence of BPA, chemical binding of the phosphorus atoms of nearby PFBT@L Pdots with BPA hydroxyl functional groups led to the aggregation of the PFBT@L Pdots aggregation and quenching their yellow emission, but the blue emission of Cdots, on the other hand, remained stable. The proposed PFBT@L Pdots probe was successfully applied for the detection of BPA in real water samples, and the results were in good agreement with those obtained by HPLC-FLD. To the best of our knowledge, this is the first report that the calixarene has been utilized to modify Pdots.

Anthracene and tetraphenylsilane based conjugated porous polymer nanoparticles for sensitive detection of nitroaromatics in water

Conjugated porous polymers (CPPs) are a kind of promising sensing materials for the detection of nitroaromatic compounds, but their sensing applications in aqueous media are limited because of their poor dispersity or solubility in water. In this study, we prepared anthracene and tetraphenylsilane based CPPs named PSiAn by conventional Suzuki coupling and Suzuki-miniemulsion polymerization, respectively. The structure, morphology and porosity of the CPPs were characterized by Fourier Transform infrared spectroscopy (FT-IR), proton nuclear magnetic resonance (1H NMR), transmission electron microscope (TEM) and N2 sorption isotherm, respectively. Both of the CPPs have porous structure which is beneficial for the adsorption and diffusion of the analytes within them. The particle size of PSiAn nanoparticles prepared by Suzuki-miniemulsion polymerization is 10–40 nm from the TEM image, which facilitates the dispersion in the aqueous phase. Combined with the porosity and nanoparticle morphology, PSiAn nanoparticles realized the efficient photoluminescence (PL) sensing of nitroaromatic explosives in aqueous phase. The limit of detection (LOD) and limit of quantitation (LOQ) of PSiAn nanoparticles for 2,4,6-trinitrophenol (TNP) detection in the pure aqueous phase are 0.33 μM and 1.11 μM, respectively. Meanwhile, the good selectivity and anti-interference in presence of other nitro-compounds were observed. Furthermore, the spike/recovery test for the TNP detection in real water samples by PL sensing based on PSiAn nanoparticles indicates the quantitative recovery of TNP from 100.74 % to 101.00 %. The electrochemical test, ultraviolet–visible absorption spectra, excitation and emission spectra, and time-resolved PL spectra were investigated to explore the PL sensing mechanism. As a result, it is found that the fluorescence inner filter effect might be the predominant quenching mechanism during the detection of nitrophenolic compounds such as TNP and 4-nitrophenol (4-NP).

Pencil Graphite Electrocatalytic Sensors Modified by Pyrene Coated Reduced Graphene Oxide Decorated with Molybdenum Disulfide Nanoroses for Hydrazine and 4-Nitrophenol Detection in Real Water Samples.

Novel nanostructured platforms based on Pencil Graphite Electrodes (PGEs), modified with pyrene carboxylic acid (PCA) functionalized Reduced Graphene Oxide (rGO), and then decorated by chronoamperometry electrodeposition of MoS2 nanoroses (NRs) (MoS2NRs/PCA-rGO/PGEs) were manufactured for the electrocatalytic detection of hydrazine (N2H4) and 4-nitrophenol, pollutants highly hazardous for environment and human health. The surface morphology and chemistry of the MoS2NRs/PCA-rGO/PGEs were characterized by scanning electron microscopy (SEM), Raman, and X-ray photoelectron spectroscopy (XPS), assessing the coating of the PCA-rGO/PGEs by dense multilayers of NRs. N2H4 and 4-nitrophenol have been monitored by Differential Pulse Voltammetry (DPV), and the MoS2NRs/PCA-rGO/PGEs electroanalytical properties have been compared to the PGEs, as neat and modified by PCA-rGO. The MoS2NRs/PCA-rGO/PGEs demonstrated a higher electrochemical and electrocatalytic activity, due to their high surface area and conductivity, and very fast heterogeneous electron transfer kinetics at the interphase with the electrolyte. LODs lower than the U.S. EPA recommended concentration values in drinking water, namely 9.3 nM and 13.3 nM, were estimated for N2H4 and 4-nitrophenol, respectively and the MoS2NRs/PCA-rGO/PGEs showed good repeatability, reproducibility, storage stability, and selectivity. The effectiveness of the nanoplatforms for monitoring N2H4 and 4-nitrophenol in tap, river, and wastewater was addressed.

Dual-emitting N-doped carbon dots/AuNCs nanohybrids as an efficient ratiometric fluorescent probe and a paper sensor for Pb2+ sensing

Ratiometric fluorescent sensors could effectively eliminate the interference of spontaneous fluorescence or instrument fluctuation to improve the analysis sensitivity and accuracy. In this work, a dual-emission nitrogen-doped carbon dots/AuNCs (NCDs-AuNCs) nanohybrid was fabricated under mild conditions by the hydrothermal method, without additional coupling agents, which is facile and environmentally friendly. The prepared nanohybrid was employed for the sensitive detection of Pb2+. The sensor exhibited dual emission peaks at 460 and 625 nm with efficient fluorescence resonance energy transfer under a single excitation wavelength of 360 nm, in which the red fluorescence of AuNCs was enhanced and the blue fluorescence of NCDs was slightly quenched with the presence of Pb2+. The quantitative analysis of Pb2+ was performed upon the change of both fluorescence intensities. The sensor was successfully used for Pb2+ detection in real water samples with satisfactory spiking recoveries in a range of 91.0%–101.3% and low relatively standard deviations (RSDs < 3%), which exhibited good selectivity and anti-interference ability. In addition, a paper-based sensor was fabricated by immobilizing the nanohybrids on filter paper, which enables the visual semi-quantitative determination of Pb2+ by the naked eye through the color transition from blue to pink. The prepared NCDs-AuNCs nanohybrids showed great application potential in environmental water monitoring in an efficient and green way.

Ultrasensitive rapid detection of antibiotic resistance genes by electrochemical ratiometric genosensor based on 2D monolayer Ti3C2@AuNPs

As an important emerging pollutant, antibiotic resistance genes (ARGs) monitoring is crucial to protect the ecological environment and public health, but its rapid and accurate detection is still a major challenge. In this study, a new single-labeled dual-signal output ratiometric electrochemical genosensor (E-DNA) was developed for the rapid and highly sensitive detection of ARGs using a synergistic signal amplification strategy of T3C2@Au nanoparticles (T3C2@AuNPs) and isothermal strand displacement polymerase reaction (ISDPR). Specially, two-dimensional monolayer T3C2 nanosheets loaded with uniformly gold nanoparticles were prepared and used as the sensing platform of the E-DNA sensor. Benefiting from excellent conductivity and large specific surface area of Ti3C2@AuNPs, the probe immobilization capacity of the E-DNA sensor is doubled, and electrochemical response signals of the E-DNA sensor were significantly improved. The proposed single-labeled dual-signal output ratiometric sensing strategy exhibits three to six times higher sensitivity for the sul2 gene than the single-signal sensing strategy, which significantly reduces cost meanwhile retaining the advantages of high sensitivity and reliability offered by conventional dual-labeled ratiometric sensors. Coupled with ISDPR amplification technology, the E-DNA sensor has a wider linear range from 10 fM to 10 nM and a limit of detection as low as 2.04 fM (S/N=3). More importantly, the E-DNA sensor demonstrates excellent specificity, good stability and reproducibility for target ARGs detection in real water samples. The proposed new sensing strategy provides a highly sensitive and versatile tool for the rapid and accurate quantitative analysis of various ARGs in environmental water samples.

Molecularly imprinted polymers-isolated AuNP-enhanced CdTe QD fluorescence sensor for selective and sensitive oxytetracycline detection in real water samples

A molecularly imprinted polymers (MIPs)-isolated AuNP-enhanced fluorescence sensor, AuNP@MIPs-CdTe QDs, was developed for highly sensitive and selective detection of oxytetracycline (OTC) in aqueous medium. The developed sensor combined the advantages of strong fluorescence signal of metal-enhanced fluorescence (MEF), high selectivity of MIPs, and stability of CdTe QDs. The MIPs shell with specific recognition served as an isolation layer to adjust the distance between AuNP and CdTe QDs to optimize the MEF system. The sensor demonstrated the detection limit as low as 5.22 nM (2.40 μg/L) for a concentration range of 0.1–3.0 μM OTC and good recovery rates of 96.0–103.0% in real water samples. In addition, high specificity recognition for OTC over its analogs was achieved with an imprinting factor of 6.10. Molecular dynamics (MD) simulation was utilized to simulate the polymerization process of MIPs and revealed H-bond formation as the mainly binding sites of APTES and OTC, and finite-difference time-domain (FDTD) analysis was employed to obtain the distribution of electromagnetic field (EM) for AuNP@MIPs-CdTe QDs. The experimental results combined with theoretical analyses not only provided a novel MIP-isolated MEF sensor with excellent detection performance for OTC but also established a theoretical basis for the development of a new generation of sensors.

One-step synthesis of novel carbon dots through cross amide formation of benzene-1,3,5-triamine and trimethyl 1,3,5-benzenetricarboxylate for fluorescence Hg2+ detection

Herein, we rationally designed and synthesized novel green-emitting fluorescent carbon dots (CDs) through cross amide formation of two precursors, benzene-1,3,5-triamine trihydrochloride and trimethyl 1,3,5-benzenetricarboxylate, under hydrothermal treatment. The average particle size of the CDs was ∼2.7 nm with graphitic carbon structures. The obtained CDs showed good photoluminescent properties with a quantum yield of up to 11.2%. The carbon dots showed good fluorescence sensitivity and selectivity for Hg2+, and the LOD and LOQ values were 17.5 pM and 58.3 pM in the range of 0.1–0.8 μM, which could be successfully applied to Hg2+ detection in real water samples as well as intracellular Hg2+ fluorescence detection.

A fluorescent “off-on-off” probe based on a new bis(salamo)-like compound for the sensitive and rapid detection of phosphates

A new bis(salamo)-like compound H3L was designed and synthesized. With the addition of Zn2+ ions to the H3L solution, the fluorescence intensity increased significantly and the color changed from blue-cyan to bright green. Based on ESI-MS, UV–Vis spectroscopy and DFT calculations, a plausible mechanism for the interaction of the compound H3L with Zn2+ ions is proposed. The in situ complex sensor l-Zn2+ formed by the coordination of the compound H3L with Zn2+ions has been used for various anion recognition. The results showed that the sensor l-Zn2+ has high selectivity and sensitivity to phosphates. The fluorescence experiments of the compound H3L and sensor l-Zn2+ at different pH values showed that fluorescence response is good in neutral and weak base environment. Simple test paper strips and the detection in real water samples were applied for the detection of phosphates in complex environment.

Smartphone‐Assisted Electrochemical Sensor Based on Mg0.5Co2.5(PO4)2 and Carbon Black for Trace Bisphenol A Detection

AbstractBisphenol A (BPA) widely recognized as an endocrine disruptor can induce serious threats to human health such as sexual anomalies and cancer. Unfortunately, BPA has been increasingly used since 1950s; specifically during the manufacturing of polycarbonates and plastics such as food containers and water bottles. Thus, there is an urgent need to develop low‐cost, simple, portable and sensitive sensors for in‐situ detection of this contaminant in food and water. The combination of nanostructured carbon materials and metal/metal oxide nanoparticles can result in materials with unique physicochemical properties as well as excellent catalytic behaviors. Herein, we propose a smartphone‐assisted electrochemical sensor based on the combination of Mg0.5Co2.5(PO4)2 and carbon black (CB) modified screen‐printed electrode (SPE) for a rapid and sensitive determination of BPA. Structural characterization confirmed the formation of Mg0.5Co2.5(PO4)2/CB nanocomposite on SPE surface. Very low oxidation potential of BPA was observed during the differential pulse voltammetry (DPV) experiments at 0.16 V vs. Ag/AgCl. The sensor revealed two‐step linear response from 0.5–6.5 μm and from 16.5–100 μm with a lower limit of detection (LOD) of 0.15 μm. A good reproducibility, excellent stability, and high interference‐free ability were obtained. Furthermore, the developed sensor showed satisfactory recoveries for BPA detection in real water samples.

‘Turn-ON’ furfurylamine-based fluorescent sensor for Cd2+ ion detection and its application in real water samples

The ability of the new furfurylamine-derived Schiff base ligand (E)-4-chloro-2-((((5-methylfuran-2-yl)methyl)imino)methyl)phenol (CFMP) to recognize metal ions as a chemosensor has been studied. According to thorough research on the several facets of metal sensing phenomena, the Schiff base ligand CFMP demonstrated selective colorimetric and fluorescence sensing behavior towards the Cd2+ ion in a methanol–water system with strong binding nature, which was easily visible to the human eye. Job's plot titrations were used to determine the metal–ligand complex's stoichiometry, and LCMS data served as further confirmation. The CFMP has a low detection limit (LOD) of 0.2345 µM and shown outstanding fluorescence sensing activity in buffer fluid with a pH of 7.2. Investigations into the fluorescence characteristics of the CFMP and the metal complex in the solution state revealed an improvement in fluorescence emission intensity following complexation. Additionally, utilizing electronic absorption spectroscopic techniques on samples of lake and tap water, the use of Cd2+ ion detection in real water samples was investigated.

Highly stable ammonium ion-selective electrodes based on one-pot synthesized gold nanoparticle-reduced graphene oxide as ion-to-electron transducers

An effective transducer for all-solid-state ion-selective electrodes (SC-ISEs) was developed based on gold nanoparticle-reduced graphene oxide (AuNP-rGO) hybrid material. The AuNP-rGO composite was synthesized via a simple, eco-friendly, and one-pot method with sodium citrate as the reducing agent and the stabilizer. The nanocomposite was deposited on the GC substrate via the drop-casting method and then covered with an ammonium ion-selective membrane (NH4+-ISM) to form the potentiometric electrode. The AuNP-rGO layer possessed a large surface area, high capacitance, and good hydrophobicity; thereby effectively enhancing the potential stability of the electrode without the formation of an aqueous layer. The electrode also exhibited a rapid potential response (<10 s) to NH4+ ions, an excellent Nernstian response with a slope of 56.94 (±1.57) mV/decade, a detection range of 10-5 − 10-2 M, and a detection limit of 3.80 × 10-6 M. The proposed electrode also exhibited outstanding properties including insensitivity to interferences (light, oxygen, carbon dioxide, and redox species), good reproducibility, and long operating life. The electrode has been successfully applied for NH4+ detection in real water samples, which makes it a promising alternative for developing effective and robust SC-ISEs.

A chemiluminescence biosensor based on the peroxidase-like property of molybdenum disulfide/zirconium metal-organic framework nanocomposite for diazinon monitoring

BackgroundOrganophosphorus pesticides are widely used in agriculture owing to their high effectiveness as insecticides. Among these, diazinon is a common environmental contaminant that acts as an acetylcholinesterase (AChE) enzyme inhibitor. As the current methods are too expensive and time-consuming for routine analysis of diazinon, its trace monitoring by rapid and sensitive methods is critical to protect the environment and human health. ResultsA biosensor was introduced for the indirect detection of diazinon using a molybdenum disulfide/zirconium metal-organic framework (MoS2@MIP-202(Zr)) nanocomposite. The probe is based on the peroxidase mimic of the prepared nanocomposite on NaHCO3–H2O2 chemiluminescence system as well as the inhibitory effect of diazinon on the enzymatic activity of AChE. The chemiluminescence signal is gradually decreased with an increase in diazinon concentration, and there is a linear relationship between the analytical signal and diazinon concentration. Under the optimum conditions, the calibration plot is linear in the concentration range of 0.5–300.0 nmol L−1. The limit of detection and quantification limit of the method are 0.12 and 0.40 nmol L−1, respectively. The inter-day and intra-day relative standard deviations (% RSD n = 5, diazinon concentration; 100 nmol L−1) are 3.66 and 1.35%, respectively. The method was used for diazinon detection in real water samples, and the high relative recovery values for the spiked samples along with satisfactory results of a certified reference material analysis confirmed that the method is accurate and free from the matrix effect. Significance and noveltyA nano-probe based on the peroxidase-like property of MoS2@MIP-202(Zr) nanocomposite was developed for the first time for indirect detection of residue levels of diazinon in water samples. The high stability of the nanocomposite makes it a good alternative for natural peroxidase enzymes such as horseradish peroxidase with low stability.

MnO2 nanosheet-assisted ratiometric fluorescence probe for the detection of sulfide based on silicon nanoparticles and o-phenylenediamine

A ratiometric fluorescence probe was fabricated based on MnO2 nanosheets, silicon nanoparticles (Si NPs), and o-phenylenediamine (OPD) for sulfide detection. In this system, the MnO2 nanosheets play three crucial roles, i.e., fluorescence quencher of the Si NPs, oxidizing of non-fluorescence OPD to produce a fluorescence substance 2, 3-diaminophenazine (OPDox), and sulfide recognition unit. The MnO2 nanosheets were reduced and lost fluorescence quenching capacity and the oxidase-like characteristics after the addition of sulfide, so that the production of OPDox was restricted and the fluorescence of the Si NPs recovered. Therefore, the fluorescence intensity ratio of OPDox at 565 nm to Si NPs at 450 nm was employed as the signal output to construct a novel ratiometric fluorescence sensor for sulfide detection. Under optimal conditions, a linear relationship was noticed between F565/F450 ratio and the sulfide concentration in the range of 2–20 μM with a 0.31 μM detection limit. Moreover, the proposed strategy demonstrates practicability for sulfide detection in real water samples with satisfactory recoveries of 96.0–106%.

Selective and sensitive fluorescence detection of Pd (II) in 100% water and imaging application in living cells

• A novel quinoline-benzimidazole conjugate was designed and synthesized. • Pd 2+ -selective detection in pure water was achieved based on a quinoline-based fluorescent platform. • The present senor was successfully used for Pd 2+ detection in real water samples and fluorescence imaging in living cells. A novel quinoline-based fluorescent chemosensor ( QB-3 ) for Pd 2+ was designed and achieved a good sensing performance in 100% pure water. The QB-3 showed a selective and fast fluorescence quenching response in the presence of Pd 2+ without significant competition interferences from others metal ions. The fluorescence intensity at 411nm showed a linear decrease with the addition of the Pd 2+ concentration in the range of 0–5 μM. It was found that the detection of limit was 0.089 μM (S/N = 3), lower than the threshold limit WHO recommended. Job's plot investigation revealed a 2:1 stoichiometry between the QB-3 and Pd 2+ , and the complex was confirmed by mass spectral analysis. The DFT calculation predicted that an electron transfer process toward Pd 2+ in the complex may be responsible for the fluorescence quenching of QB-3 . The practical application in real water samples and fluorescence imaging in living cells was also achieved. A quinoline-based fluorescent chemosensor for Pd 2+ -selective detection in 100% pure water was developed, and successfully applied in practical water samples analysis and fluorescence imaging in living cells.

Development of portable whole-cell biosensing platform with lyophilized bacteria and its application for rapid on-site detection of heavy metal toxicity without pre-resuscitation

The high toxicity of heavy metals necessitates monitoring technology that allows rapid adaptation and deployment. Microbial whole-cell biosensors have become a priority because of their excellent performance. However, traditional methods have several limitations, including long assay time, poor portability, and the lack of ready-to-use on-site devices. In this study, a novel portable whole-cell biosensing platform was developed by integrating a simple handheld fiber-optic dissolve oxygen sensor and bacterial culture or lyophilized bacteria. Based on the oxygen consumption inhibition mechanism, this platform achieved rapid acute toxicity measurement of heavy metal ions through inhibit Escherichia coli (E.coli) respiration. Under the optimal conditions, the limit of detection and IC50 of Hg2+ using E. coli culture were 5.62 μM and 11.64 μM, respectively. Interestingly, the lyophilized E. coli could be directly applied for Hg2+ toxicity detection without pre-resuscitation, where an IC50 of 31.28 μM was obtained, and the whole detection process was only 18 min. The lyophilized E. coli could be stored long-term at −80 °C without significant loss of activity and detection performance. The portable whole-cell biosensing platform demonstrated a high potential for rapid on-demand toxicity detection in real water samples. The developed strategy is not only fast, portable, and easily storable, but also highly suited for on-site ready-to-use, and high-frequency toxicity detection of heavy metal ions in the field.