Environmental Water Samples Research Articles

D-π-A-π-D-Configured Imidazole-Tethered Benzothiadiazole-Based Sensor for the Ratiometric Discrimination of Picric Acid: Applications in Latent Fingerprint Imaging.

A tetraphenyl imidazole-appended benzothiadiazole-based fluorogenic probe (4,7-bis(4-(1,4,5-triphenyl-1H-imidazol-2-yl)phenyl)benzo[c][1,2,5]thiadiazole (BIPT)) has been successfully synthesized and characterized by NMR and high-resolution mass spectrometry (HRMS) spectral analyses. A low limit of detection (LOD) can be achieved to detect picric acid (PA; 7.89 nM). When benzothiadiazole acceptors are incorporated in the D-A-D probe, it can produce a large Stokes shift (206 nm) as a result. Fascinatingly, the fluorescence signals of BIPT were ratiometrically induced by the interaction with PA and exhibited an apparent emission shift from pink to green. The detection process of BIPT is triggered by an intermolecular charge transfer process, as the charge transfer takes place from the electron-rich imidazole to the electron-deficient PA. Moreover, fluorescence detection of PA has been employed in paper strips. Advantageously, sensor BIPT can potentially be applied to contact mode and real-time detection of PA in environmental water samples. Additionally, the BIPT sensor has been successfully employed for latent fingerprint imaging. The study provides clear insights into the rational design of chemosensors for sensing and real-time applications.

Microelectrode Voltammetric Analysis of Low Concentrations of Se(IV) Ions in Environmental Waters.

The current research is an attempt to analyze on-site selenium(IV) ions in environmental water samples using an eco-friendly miniaturized sensor developed by deposition of a very thin amount of metallic bismuth in a solid Bi electrode tightly closed in miniaturized housing. Numerous experimental variables are optimized, including the composition of the supporting electrolyte and its pH, as well as activation and accumulation conditions. Under optimized measurement conditions, the method shows high sensitivity, permitting a very low limit of detection equal to 7 × 10-10 mol L-1 to be achieved in a short accumulation time of 50 s. The performance of this microsensor was investigated against numerous interference factors and its good anti-interference capability was demonstrated. A series of voltammetric experiments by differential pulse cathodic stripping voltammetry (DPCSV) were carried out and they proved that the miniaturized sensor is characterized by very good accuracy and precision as well as long-term stability. The solid bismuth microelectrode displays a good voltammetric response in the analysis of diverse samples with a complex matrix and demonstrates a good recovery rate.

EVALUATION OF GREENNESS PROFILES OF VARIOUS DEVELOPED METHODS FOR THE DETERMINATION OF COMMONLY USED NONSTEROIDAL ANTI-INFLAMMATORY DRUGS (NSAIDs) IN ENVIRONMENTAL WATERS

Objective: In our study, it was aimed to make a comparative analysis of the environmental impact profiles of two approaches including Gas Chromatography (GC) and Liquid Chromatography (LC) methods, which are frequently used techniques for the determination of non-steroidal anti-inflammatory drugs (NSAIDs) and their metabolites in environmental water samples. Material and Method: The evaluation of the methods' environmental impact was performed using National Environmental Methods Index Label (NEMI), Analytical Eco-scale, Analytical GREEnness Metric (AGREE), and Green Analytical Procedure Index (GAPI). Result and Discussion: The routine analysis of NSAIDs in environmental waters is carried out, resulting in a significant volume of chemical waste. In recent times, there has been a growing significance attributed to environmentally conscious analytical methodologies and the evaluation of methodologies through a green lens to confront this challenge. There is no statistically significant difference in terms of environmental impact profile was observed between the two methods compared.

Multi-criteria decision analysis: technique for order of preference by similarity to ideal solution for selecting greener analytical method in the determination of mifepristone in environmental water samples

This work proposes the use of multi-criteria decision analysis (MCDA) to select a more environmentally friendly analytical procedure. TOPSIS, which stands for Technique for Order of Preference by Similarity to Ideal Solution, is an example of a MCDA method that may be used to rank or select best alternative based on various criteria. Thirteen analytical procedures were used in this study as TOPSIS input choices for mifepristone determination in water samples. The input data, which consisted of these choices, was described using assessment criteria based on 12 principles of green analytical chemistry (GAC). Based on the objective mean weighting (MW), the weights for each criterion were assigned equally. The most preferred analytical method according to the ranking was solid phase extraction with micellar electrokinetic chromatography (SPE-MEKC), while solid phase extraction combined with ultra-high performance liquid chromatography tandem mass spectrometry (SPE-UHPLC-MS/MS) was ranked last. TOPSIS ranking results were also compared to the green metrics NEMI, Eco-Scale, GAPI, AGREE, and AGREEprep that were used to assess the greenness of thirteen analytical methods for mifepristone determination. The results demonstrated that only the AGREE metric tool correlated with TOPSIS; however, there was no correlation with other metric tools. The analysis results suggest that TOPSIS is a very useful tool for ranking or selecting the analytical procedure in terms of its greenness and that it can be easily integrated with other green metrics tools for method greenness assessment.

Magnetic Poly(Amidoamine) Dendrimer for the Dispersive Solid Phase Extraction of Nitrophenols from Environmental Water Samples.

A fast and simple dispersive solid phase extraction method is described for nitrophenols determination in water samples by using gas chromatography-nitrogen phosphorous detector. Firstly, the Poly(amidoamine) grafted Fe3O4 magnetic nanoparticles were synthesized in different generations by successive addition of butyl acrylate and ethylenediamine. After characterization, the prepared dendrimer was utilized as an adsorbent for magnetic solid phase extraction of 2-nitrophenol, 3-nitrophenol, and 4-nitrophenol to benefit large number of surface amine interaction sites. The effects of the different parameters influencing the sample preparation efficiency were investigated. The proposed method showed linearity in the ranges of 0.04-700 and 0.05-700µg/dm3 for nitrophenols. The obtained limits of detection and quantification under optimized conditions were 0.01-0.02 and 0.04-0.05µg/dm3, respectively. The relative standard deviations (n = 5) were less than 3.8% (at 10µg/dm3). Moreover, the calculated enrichment factors were above 200. In addition, the relative recoveries for a spiked river water sample were satisfactory.

A novel colormetric and light-up fluorescent sensor from flavonol derivative grafted cellulose for rapid and sensitive detection of Hg2+ and its applications in biological and environmental system

Mercury ion (Hg2+) is one of harmful heavy metal ions that can accumulate inside the human organism and cause some health problems. In the article, a highly effective fluorescent probe named EC-T-PCBM was prepared by grafting flavonol derivatives onto ethyl cellulose for the specific recognition of Hg2+. EC-T-PCBM exhibited a remarkable fluorescence light-up response toward Hg2+ with excellent sensitivity. EC-T-PCBM possessed several prominent sensing properties for Hg2+, such as low detection limit (43.9 nM), short response time (5 min), and wide detection pH range (6–9). The response mechanism of EC-T-PCBM to Hg2+ has been verified through 1H NMR titration and DFT computation. Additionally, EC-T-PCBM not only can be used for accurately determining trace amount of Hg2+ in actual environmental water samples, but also can serve as a portable and rapid device by loading it on test strips for sensitive and selective visualization of Hg2+. More importantly, the confocal fluorescence imaging of onion cells suggested the favorable cell membrane permeability of EC-T-PCBM and its prominent ability to continuously monitor the enrichment from Hg2+ within fresh plant tissues.

Distribution and virulence of Escherichia coli harboring cyclomodulins and supplementary virulence genes isolates from clinical and environmental samples

This study aimed to determine the prevalence of cyclomodulins (cdt, cnf, pks and cif) in Escherichia coli (E. coli) isolated from clinical and environmental samples, the presence of supplementary virulence genes (SVG), antibiotic resistance, and in vitro cytotoxicity. 413 E. coli were isolated from clinical (stool from obese subjects, normal weight subjects, children with diarrhea, and children without diarrhea; and urine from pregnant and non-pregnant women with urinary tract infections) and environmental (water and different foods) samples. PCR was performed to identify E. coli pathotypes, the four cyclomodulins, and 18 SVG; virulence score, cytotoxic assay, and antibiotic resistance assay were performed. Fifteen percent of E. coli were positive for cyclomodulins and were found in all isolation sources; however, in children with diarrhea, they were more frequent. The most frequent cyclomodulin was cdt. More DEC strains harbor cyclomodulins than non-DEC, and cyclomodulins were most frequent among aEPEC pathotype. SVG ehaC was associated with cyclomodulin-positive strains. Cyclomodulin-positive E. coli had a higher virulence score but no significant cytotoxic activity. They were slightly more resistant to antibiotics. In conclusion, cyclomodulins-positive E. coli was widely distributed in humans, food, and the environment, and they were associated with SVG ehaC, suggesting that these genes may play a role in the pathogenesis of the cyclomodulins. However, more research is needed.

Colorimetric detection of Fe2+ and Cr2O72− in environmental water samples based on dual-emitting RhB-embedded Zr-MOFs

Three dye-loaded tunable dual-emission colorimetric fluorescent probes RhB@UiO-66-Ph (R@U-P) were prepared by in-situ encapsulation method under solvothermal conditions. The resonance energy transfer between UiO-66-Ph and RhB made the dual emission of R@U-P easily tunable with the embedded dye content changing. The R@U-P composites achieved emission from purple light to red light, and served as probes to realize comparative detection of Fe3+, Fe2+ and Cr2O72− in water through colorimetric or quenching detection mode. Mechanism study indicates that the resonance energy transfer or electron transfer interactions between R@U-P composites and inorganic ions resulted in the relative changes of the two emission peaks and realized the selective detection of analytes. The preparation and application of R@U-P probes provide a promising strategy for the in-situ encapsulation dye to obtain two dual-emission composites for the comparative detection of Fe3+, Fe2+ and Cr2O72− in water samples.

A novel naphthalimide-appended salamo-type fluorescent sensor for continuous “on-off-on” detection of Cu2+ and CN− ions, sensing mechanisms and applications

A novel naphthalimide-appended salamo-type fluorescence sensor (E)-2-hydroxy-3-methoxybenzaldehyde O-(2-((((E)-1-(3-(1,3-dioxo-1H-benzo[de]isoquinolin-2(3H)-yl)-2-hydroxyphenyl)ethylidene)amino)oxy)ethyl) oxime (H2L) for continuous identification of copper(II) and cyanide ions was constructed. The sensor H2L exhibited relatively high selectivity for Cu2+ in a 1:1 stoichiometric manner, and the increase of Cu2+ led to quenching of blue fluorescence, with a minimum detection limit of 9.37 × 10−9 M. In addition, the complex generated by the sensor H2L with Cu2+ could in situ recognize CN−, the L-Cu2+ complex coordinates with CN− in a 1:1 stoichiometric manner and exhibits high selectivity, and the addition of CN− results in enhanced blue fluorescence. The time response and pH effect tests demonstrated the advantages of H2L such as fast response for the continuum recognition of Cu2+ with CN− and wide pH test range. Based on the above results, an attempt was made to determine Cu2+ with CN− in spiked environmental water samples with good recoveries.

Ultrasensitive electrochemical sensors based on Cu and Cu@Ag nanorods for simultaneous heavy metal detection

This work reports the development of ultrasensitive miniaturized electrochemical device for heavy metal sensing. A laser engraver based patterning of fluorine-doped tin oxide (FTO) sheet was done to draw an etched pattern forming a miniaturized 3-electrode configuration. A layer of Ag/AgCl ink served as pseudo-reference electrode. The sensing electrode was coated using low-cost Cu nanorods (CuNRs) grown radially along the {110} surface with aspect ratio of 8.0 and Cu@Ag core-shell nanorods (Cu@AgNRs) formed via galvanic displacement for simultaneous electrocatalytic detection of heavy metal ions (Pb(II), Cd(II), Hg(II), and Zn(II)) present in water. The electroactive surface area of the prepared devices is 0.026, 0.093 and 0.125 cm2 for bare FTO, CuNRs/FTO and Cu@AgNRs/FTO, respectively. Bimetal Cu@AgNRs/FTO sensor exhibited the lowest limit of detection of 1, 2, 5 and 6 nM, respectively, detecting Cd(II), Pb(II), Zn(II), and Hg(II) ions, and it was 2, 2, 3 and 4 nM, respectively, for simultaneous detection of Zn(II), Pb(II), Cd(II) and Hg(II). The Cu@AgNRs/FTO based device showed distinct peak-to-peak separation by 0.40, 0.25 and 0.51 V for Zn(II)-Cd(II), Cd(II)-Pb(II) and Pb(II)-Hg(II), respectively. This device was highly sensitive (583.6–1261.8 μA․μM−1․cm−2) for heavy metal detection over CuNRs/FTO (15.9–107.4 μA․μM−1․cm−2). The Cu@AgNRs/FTO based sensors demonstrated good reproducibility (relative standard deviation ≤ 5%) with recovery (>90%) in the case of all target heavy metals simultaneously present in environmental water samples. Hence, the Cu nanorods based miniaturized sensing platforms developed in the present study for simultaneous heavy metal detection are potential low-cost alternatives providing a repeatability of upto 4 cycles unlike the commercial screen-printed electrodes.

A novel self-enhanced ECL-RET aptasensor based on the bimetallic MOFs with homogeneous catalytic sites for kanamycin detection

The inappropriate use of antibiotics undoubtedly poses a potential threat to public health, creating an increasing need to develop highly sensitive tests. In this study, we designed a new type of porphyrin metal-organic frameworks (Fe TCPP(Zn) MOFs) with homogeneous catalytic sites. The ferric-based metal ligands of Fe TCPP(Zn) MOFs acted as co-reaction accelerators, which effectively improved the conversion efficiency of H2O2 on the surface of MOFs, then increased the concentration of •OH surrounding porphyrin molecules to achieve self-enhanced electrochemiluminescence (ECL). Based on this, an aptasensor for the specific detection of kanamycin (KAN) in food and environmental water samples was constructed in combination with resonance energy transform (RET), in which Fe TCPP(Zn) MOFs were used as luminescence donor and AuNPs were used as acceptor. Under the best conditions, there was a good linear relationship between the ECL intensity and the logarithm of KAN concentration with a detection limit of 0.28 fM in the range of 1.0 × 10−7–1.0 × 10−13 M, demonstrating satisfactory selectivity and stability. At the same time, the complexity of the detection environment was reduced, which further realized the reliable analysis of KAN in milk, honey and pond water. Overall, this innovative self-enhanced ECL strategy provides a novel approach for constructing efficient ECL systems in MOFs, and also extends the application of MOFs to the analysis and detection of trace antibiotics in food and the environment.

Continuous Detection of Cobalt Ions and Pyrophosphates by NAC-CdTe Quantum Dots Fluorescence Probes.

In this work, a simple and sensitive N-acetyl-L-cysteine (NAC)-covered CdTe quantum dots (NAC-CdTe QDs) fluorescence probe for continuous detection of Co2+ and pyrophosphate ions (PPi, P2O74-) was synthesized. The fluorescence of the quantum dots was significantly quenched by Co2+ through the coordination of Co2+ and the carboxyl groups on the NAC-CdTe quantum dots. Interestingly, the combination of NAC-CdTe quantum dots with Co2+ yields a new fluorescence probe of Co2+-modified NAC-CdTe QDs (Co2+@NAC-CdTe). The addition of PPi restored the fluorescence due to the competition between PPi and carboxyl groups with Co2+ causing Co2+ to detach from the surface of Co2+@NAC-CdTe quantum dots. Thus, a sensitive and reversible detection of Co2+ and PPi had been successfully established. The Co2+@NAC-CdTe quantum dots fluorescence probe exhibits excellent selectivity and high sensitivity toward PPi detection with low detection limit of 0.28μM. In addition, the novel fluorescence probe was successfully applied to detect the concentration of PPi in environmental water samples and in-vitro cells imaging.

Synergistic optical sensing: Selective colorimetric analysis of copper in environmental and biological samples

A groundbreaking optical sensing membrane has been engineered for the accurate assessment of copper ions. The pliable poly(vinyl chloride) membrane is formulated through the integration of sodium tetraphenylborate (Na-TPB), 4-(2-hydroxy-4-nitro azobenzene)-2-methyl-quinoline (HNAMQ), and tri-n-octyl phosphine oxide (TOPO), in conjunction with o-nitrophenyl octyl ether (o-NPOE). The sensor membrane undergoes a thorough investigation of its composition to optimize performance, revealing that HNAMQ serves a dual role as both an ionophore and a chromoionophore. Simultaneously, TOPO contributes to enhancing the complexation of HNAMQ with copper ions. Demonstrating a linear range for Cu2+ ions spanning from 5.0 × 10−9 to 7.5 × 10−6 M, the proposed sensor membrane showcases detection and quantification limits of 1.5 × 10−9 and 5.0 × 10−9 M, respectively. Rigorous assessments of potential interferences from other cations and anions revealed no observable disruptions in the detection of Cu2+. With no discernible HNAMQ leaching, the membrane demonstrates rapid response times and excellent durability. The sensor exhibits remarkable selectivity for Cu2+ ions and can be regenerated through exposure to 0.05 M EDTA. Successful application of the sensor in determining the presence of Cu2+ in biological (blood, liver and meat), soil, food (coffee, black tea, sour cherry juice, black currant, and milk powder) and environmental water samples underscores its efficacy.

Sacrificial template synthesis of hollow sulfonate group functionalized microporous organic network for efficient solid phase extraction of sulfonamide antibiotics from milk and honey samples

The highly conjugated and hydrophobic characteristics of microporous organic networks (MONs) have largely impeded their broad applications in sample pretreatment especially for the polar or ionic analytes. In this work, a novel uniform hollow shaped sulfonate group functionalized MON (H-MON-SO3H-2) was synthesized via the sacrificial template method for the efficient solid phase extraction (SPE) of sulfonamides (SAs) from environmental water, milk, and honey samples prior to HPLC analysis. H-MON-SO3H-2 exhibited large specific surface area, penetrable space, good stability, and numerous hydrogen bonding, electrostatic, hydrophobic and π-π interaction sites, allowing sensitive SPE of SAs with wide linear range (0.150-1000 μg L−1), low limit of detection (0.045-0.188 μg L−1), good precisions (intra-day and inter-day RSD < 7.3%, n = 5), large enrichment factors (95.7-98.5), high adsorption capacities (250.4-545.0 mg g−1), and satisfactory reusability (more than 80 times). Moreover, the established method was successfully applied to extract SAs from spiked samples with the recoveries of 86.1-104.3%. This work demonstrated the great potential of H-MON-SO3H-2 in the efficient SPE of trace SAs in complex environmental water and food samples and revealed the prospect of hollow MONs in sample pretreatment.

Enhancing electrochemiluminescence for chloramphenicol detection based on the synergistic effect of doped Ti3C2 with ultrasound

Chloramphenicol (CAP) is known to be harmful to the environment and food, posing a threat to human health. Developing an effective and convenient method for detecting CAP is crucial. An electrochemiluminescence (ECL) biosensor has been designed for sensitive detection of CAP. The improved ECL behavior was attributed to the synergistic effect of N and P co-doped Ti3C2-Apt1 (N, P-Ti3C2-Apt1) nanoprobes and high intensity focused ultrasound (HIFU) pretreatment. The doping of N and P could improve the electrochemical performance of Ti3C2. HIFU pretreatment generated more reactive oxygen species (ROS) in the luminol-O2 system. N, P-Ti3C2 could aggregate and catalyze ROS, causing an increase in ECL intensity. Furthermore, N, P-Ti3C2 as a carrier loaded more aptamer, which could recognize CAP with high specificity. The detection limit was 0.01 ng/mL. This biosensor has been successfully applied in milk and environmental water samples, highlighting its potential in the field of food and environmental analysis.

Synergistic activation of lamellar bismuth selenide anchored functionalized carbon nanofiber for detecting hazardous carbendazim in environmental water samples

Pesticides pollute natural water reservoirs through persistent accumulation. Therefore, their toxicity and degradability are serious issues. Carbendazim (CBZ) is a pesticide used against fungal infections in agricultural crops, and its overexploitation detrimentally affects aquatic ecosystems and organisms. It is necessary to design a logical, efficient, and field-deployable method for monitoring the amount of CBZ in environmental samples. Herein, a nano-engineered bismuth selenide (Bi2Se3)/functionalized carbon nanofiber (f-CNF) nanocomposite was utilized as an electrocatalyst to fabricate an electrochemical sensing platform for CBZ. Bi2Se3/f-CNF exhibited a substantial electroactive surface area, high electrocatalytic activity, and high conductivity owing to the synergistic interaction of Bi2Se3 with f-CNF. The structural chemical compositions and morphology of the Bi2Se3/f-CNF nanocomposite were confirmed by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and field-emission scanning electron microscopy (FESEM). Electrochemical analysis was carried out using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and differential pulse voltammetry (DPV). The voltammetry and impedance experiments exposed that the Bi2Se3/f–CNF–modified GCE has attained adequate electrocatalytic function with amended features of electron transportation (Rct = 35.93 Ω) and improved reaction sites (0.082 cm2) accessible by CBZ moiety along with exemplary electrochemical stability (98.92%). The Bi2Se3/f-CNF nanocomposite exhibited higher sensitivity of 0.2974 μA μM−1cm−2 and a remarkably low limit of detection (LOD) of 1.04 nM at a broad linera range 0.001–100 μM. The practicability of the nanocomposite was tested in environmental (tap and pond water) samples, which supports excellent signal amplification with satisfactory recoveries. Hence, the Bi2Se3/f-CNF nanocomposite is a promising electrode modifier for detecting CBZ.

Construction of Nickel Tungsten Oxide Anchored Carbon Nanofibers Modified with Glassy Carbon Electrode for Enhanced Electrochemical Detection of Metronidazole in Urine and Environmental Water Sample

Metronidazole (MTD) is an antibiotic that is commonly used to treat pathogens and protozoal infections, which have a highly harmful impact on human health and domestic animals. Hence, the detection of MTD is highly necessary to avoid environmental pollution. The hydrothermal technique has been utilized to prepare Nickel Tungsten oxide (NiWO4) nanosheets which were anchored with the carbon nanofiber (CNF) to produce CNF/NiWO4 nanocomposite, the nanocomposite coated on the glassy carbon electrode (GCE) and applied to the electrochemical detection of MTD. Besides, field emission scanning electron microscope (FESEM), transmission electron microscope (TEM), energy dispersive X-ray analysis (EIS), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction analysis (XRD), and X-ray photoelectron spectroscopy. Moreover, electrochemical impedance spectroscopy (EIS), cyclic voltammetry studies (CV), and differential pulse voltammetry (DPV) were also handled for the identification of the electrochemical behavior of the GCE/CNF/NiWO4 electrode responses. Finally, the CNF/NiWO4 electrode shows a low detection limit of 0.4 μM, a wide linear response range of 0.01–650 μM, and a higher sensitivity of 0.274 μA μM−1 cm−2, with better repeatability, reproducibility, and excellent stability. Finally, the prepared GCE/CNF/NiWO4 electrodes were employed to detect MTD in tap water and urine samples with acceptable recoveries.

A Small Molecule Fluorescent Probe for the Detection of Zn2+ and Alcoholic Strength in Chinese Baijiu

AbstractIn this study, a novel fluorescent probe DZ was designed by derivatizing from naphthaldehyde and benzoyl hydrazine. The probe exhibited a low detection limit of 1.75×10−8 mol/L for Zn2+ in ethanol systems. Due to its typical aggregation‐induced emission phenomenon, DZ showed exceptional efficacy in detecting the alcoholic strength of Chinese Baijiu, allowing for accurate differentiation between beverages with various alcohol contents in water/ethanol mixtures. In addition, DZ had been successfully utilized for the detection of Zn2+ in both test paper and environmental water samples.

Factorial design-aided study of different fluorogenic approaches for determination of the preservative natamycin in various matrices

Natamycin (NATA) is a widely used food preservative. It is a non-fluorescent compound; hence, a derivatization reaction to produce a fluorescent derivative was necessary for its analysis. In this context, two derivatization reactions were applied to develop two spectrofluorimetric methods for determining NATA. Method I relies on Hantzsch condensation reaction between the primary amine group of NATA and acetylacetone-formaldehyde (AAF) reagent to produce a highly fluorescent dihydropyridine derivative that is measured at λem/λex of 481/415 nm, while Method II based on the reaction of the primary amine group of NATA with o-phthalaldehyde in the presence of N-acetylcysteine which resulted in isoindole fluorophore derivative that can be monitored at λem/λex of 433/338 nm. The experimental variables of both methods were optimized using full-factorial designs. Under the optimum conditions, the proposed methods enabled the determination of NATA over concentration ranges of 50.0–500.0 ng mL−1 (LOD = 13 ng mL−1) for Method I and 0.50–10.0 μg mL−1 (LOD = 0.16 μg mL−1) for Method II. Both methods were efficiently applied to assay NATA in ophthalmic eye drops. The application was extended to include bread and environmental water samples based on the nano-scale sensitivity of Method I.

The space-charge region at CsPbBr3 NC⊆Pb-MOF p-n junction by self-sacrificing MOFs to selective detect NH3·H2O or Fe3+

The rational design of p-n heterojunction is highly desirable to optimize electron distribution and photocarriers’ transfer pathway at space-charge region, which would influence the fluorescence detection. Herein, the inorganic perovskite CsPbBr3 nanocrystals (CPB NCs) have been encapsulated into Pb-centered MOFs via simple wet-chemical self-sacrifice to construct a “turn-off” sensor for the sensitive detection of NH3·H2O or Fe3+ in aqueous solution. The Mott-Schottky plots (M-S), ultraviolet photoelectron spectroscopy (UPS) and density functional theory (DFT) calculation have proved the formation of p-n junction between the derived CsPbBr3 and parent Pb-MOF. The CPB⊆Pb-MOF heterojunction has provided a strong platform to maintain high fluorescence performance and stability in aqueous solution as sensor. It is found that the static quenching process has affected the detection of Fe3+. More importantly, the occurrence of dynamic quenching with electron transfer is also verified by fluorescence lifetime, in-situ X-ray photoelectron spectroscopy (XPS) analysis. The phase transfer has taken major reason when being introduced by NH3·H2O. Fortunately, the 0.4CPB⊆Pb-MOF has exhibited best analytical performance for NH3·H2O or Fe3+. What’s more, it has been manufactured for the visual detection for NH3·H2O or Fe3+ in the real environmental water samples. Thereby, this perovskite based water detection system would broaden the application in point-to-point precise diagnostics.