Fluorometric Sensor Research Articles

A Brief Overview of Nanozyme-Based Colorimetric and Fluorometric Sensors for Early Diagnosis of COVID-19

Currently, there are several methods for diagnosis of COVID-19 such as real-time reverse transcription-polymerase chain reaction, hematology examination, polymerase chain reaction, diagnostic guidelines based on clinical features, Chest CT scans, etc. However, yet actual testing methods to identify SARS-CoV-2 are limited. Besides, diagnosis of this new pandemic over SARS, MERS, and H1N1 is one of the most challenges of this field due to their very similar clinical characteristics. To overcome these difficulties, recently, nanozmyes-based systems have been applied for fast, accurate, reliable, and cost-effective early diagnosis of COVID-19. The aim of this review is quick overview of the nanozyme-based sensing and detection colorimetric and fluorometric methods toward early diagnosis of COVID-19. In this regard, the historical background of COVID-19 and its current diagnostic methods were reviewed. Afterward, the nanozymes were introduced and their biomedical applications were discussed. Finally, the recent progress of early diagnosis of COVID-19 based on nanozymatic systems was reviewed.

Targeting phosphoinositide signaling in cancer: relevant techniques to study lipids and novel avenues for therapeutic intervention.

Phosphoinositides serve as essential players in numerous biological activities and are critical for overall cellular function. Due to their complex chemical structures, localization, and low abundance, current challenges in the phosphoinositide field include the accurate measurement and identification of specific variants, particularly those with acyl chains. Researchers are intensively developing innovative techniques and approaches to address these challenges and advance our understanding of the impact of phosphoinositide signaling on cellular biology. This article provides an overview of recent advances in the study of phosphoinositides, including mass spectrometry, lipid biosensors, and real-time activity assays using fluorometric sensors. These methodologies have proven instrumental for a comprehensive exploration of the cellular distribution and dynamics of phosphoinositides and have shed light on the growing significance of these lipids in human health and various pathological processes, including cancer. To illustrate the importance of phosphoinositide signaling in disease, this perspective also highlights the role of a family of lipid kinases named phosphatidylinositol 5-phosphate 4-kinases (PI5P4Ks), which have recently emerged as exciting therapeutic targets for cancer treatment. The ongoing exploration of phosphoinositide signaling not only deepens our understanding of cellular biology but also holds promise for novel interventions in cancer therapy.

Naphthalene Diimide-Based Orange Emitting Luminogen: A Fluorometric Probe for Thiol Sensing through the Click Reaction.

Fluorometric sensors have gained considerable attention in various fields, including environmental monitoring, biomedical research, and clinical diagnostics. This article delineates the fabrication of an orange emitting naphthalene diimide (NDI) derivative consisting of maleimide moiety (NDI-mal) for fluorometric sensing of thiols. Spherical shaped organic nanoparticles (∼100-150 nm) were constructed by NDI-mal in dimethyl sulfoxide (DMSO)/dimethylformamide (DMF)-water through J-type aggregation. NDI-mal displayed self-assembly driven aggregation-induced emission (AIE) through excimer formation at λem= 588 nm at fw = 99 vol % DMSO/DMF-water. Naphthyl residue at both terminals of NDI-mal facilitates intramolecular charge transfer (ICT) from the donor naphthyl residue to the acceptor NDI core. The fluorescence intensity of NDI-mal fluorescent organic nanoparticles (FONPs) got quenched in the presence of thiols due to thiol-maleimide adduct formation (Michael addition). NDI-mal FONPs selectively probed thiol functionalized small molecules (4-aminothiophenol), biomolecules (glutathione (GSH)), and proteins (reduced BSA) with high sensitivity having a limit of detection of 15.3 nM, 6.0 nM, and 9.2 ng/mL, respectively. Importantly, thiol sensing was selective against analogous small molecules, biomolecules, and proteins devoid of thiol moieties. Cellular imaging demonstrated selective diagnosis of cancer cells by NDI-mal FONPs through quenching of its emission upon interaction with thiols in B16F10 cells due to the high abundance of GSH in cancer cells compared to NIH3T3 cells. NDI-mal FONPs emitted their native fluorescence inside cells subjected to reactive oxygen species mediated thiol oxidation via Fenton's reaction. Notably, GSH-maleimide adduct formation by NDI-mal FONPs displayed notable therapeutic efficacy against cancer cells having ∼2.4-fold higher killing of B16F10 in comparison to NIH3T3 cells possibly through oxidative stress induced apoptosis owing to the depletion in the GSH level. Thus, NDI-mal AIE-gen successfully emerged as a selective and sensitive probe toward thiols through thiol-maleimide click chemistry with therapeutic ability against cancer cells in the absence of systematic intervention.

Development of fluorescence nanosensor based on “off-on” effect of graphitic carbon nitride - gold nanoparticles system for amikacin quantification

A graphitic carbon nitride functionalized gold nanoparticles (g-C3N4/AuNPs) based fluorometric assay was developed for simple and rapid on-site amikacin determination. g-C3N4 fluorescence is reduced (turn-off) when they bind to AuNPs but recovers (turn-on) when amikacin binds to AuNPs and releases the g-C3N4. The assay is based on the effective property of AuNPs as absorbers in inner filter effect (IFE) systems. Under optimized conditions of 25 mM Na2SO4, pH 6.0, 3.0 mg mL−1 g-C3N4, and incubation time of 12 min, the proposed method achieved a low detection limit of 5 × 10−9 M (2.9 ppb), wide linear range from 10−8 to 10−6 M, high precision (RSD <5 %) and high selectivity over other ions including Ca2+, Mg2+, Fe2+, NO3−, and PO43− as well as several antibiotics, namely naproxen, levofloxacin, vancomycin, ceftriaxone, amoxicillin. The fluorometric sensor based on g-C3N4/AuNPs has produced good agreement quantifying amikacin in pharmaceutical samples, as cross-checked with LC-MS/MS method. The developed fluorometric sensor is promising for rapid on-site detection of other organic and inorganic substances with high sensitivity, selectivity, and minimal reagent consumption.

Hydrothermal fabrication of n-CeO2/p-CuS heterojunction nanocomposite for enhanced photodegradation of pharmaceutical drugs in wastewater under visible-light and fluorometric sensor for detection of uric acid

Hydrothermal fabrication of n-CeO2/p-CuS heterojunction nanocomposite for enhanced photodegradation of pharmaceutical drugs in wastewater under visible-light and fluorometric sensor for detection of uric acid

Fabrication of dual-functional heterostructured p-CuO/n-ZnS nanocomposite for enhanced visible-light active photocatalytic response and fluorometric sensor for selective sensing of thiol-containing amino acids

In this study, CuO, ZnS, and p-CuO/n-ZnS heterojunction composites were synthesized using a simple co-precipitation method for investigating their photocatalytic properties for dye degradation and fluorescence sensing of thiol-containing amino acids at room temperature. The synthesized CuO, ZnS, and p-CuO/n-ZnS heterostructures were analyzed using UV–vis, PL, XRD, and TEM. The results showed that the heterostructure exhibited enhanced absorption in the visible light range, and synthesized materials have spherical shape with an average particle size is 12 ± 5 nm. The photocatalytic activities of CuO, ZnS, and p-CuO/n-ZnS heterostructures were evaluated by the degradation of various dyes such as MB, MO, and MR under visible light irradiation. The p-CuO/n-ZnS heterostructure showed the best photocatalytic efficiency, with degradation rates of 98.3%, 94.2%, and 92.8% for MB, MO, and MR dyes, respectively, compared to CuO NPs (72.5%, 75.8%, and 73.5%) and ZnS NPs (76.2%, 79.1%, and 78.3%) within a 35 min of reaction. The enhanced photocatalytic efficiency of the p-CuO/n-ZnS heterostructure was attributed to its high charge separation efficiency, which remained stable for up to five cycles without any significant loss of activity. Furthermore, the p-CuO/n-ZnS heterostructure was used as a fluorescent sensor for detecting thiol-containing amino acids such as cysteine (Cys) and methionine (Met). The results showed that the heterostructure had good sensing performance for Cys and Met within the range of 1–100 μM, with a detection limit of 2.52 μM (Cys) and 5.14 μM (Met) based on the linear calibration range. Moreover, p-CuO/n-ZnS composite was used to detect Met in human serum and urine samples.

A Polycaprolactone-Capped ZnO Quantum Dots-Based Fluorometric Sensor for the Detection of Fe3+ Ions in Seawater.

Fe3+ ion plays a very active role in life, agriculture, and industry. Human health and the environment are seriously affected by the abnormal presence or excess of this cation. Therefore, the development of a fast, reliable, sensitive, and simple fluorescent probe to detect this cation is crucial. In the present paper, polycaprolactone-capped zinc oxide quantum dots were prepared for the determination of Fe3+ ions. The proposed fluorescent chemosensor exhibited a fluorometric and strong quenching effect toward Fe3+ ions at two wavelengths (303 and 602 nm). The limit of detection (LOD) was calculated as 0.410, and 0.333µM at the mentioned wavelengths. Also, the binding stoichiometric ratio was calculated as 1:1 by Job's plot. The findings indicated that the PCL@ZnO colorimetric chemosensor could be successfully applied with reliable, and good accuracy for the detection of Fe3+ ions in real seawater samples.

Machine-Based Algorithm: A Revolution We Need For Early Sepsis Diagnosis In Hospitals.

Dear Editor, Sepsis is a life-threatening medical emergency and one of the fundamental causes of early mortality within hospitals. WHO report of 2020 shows that nearly 11 million people worldwide die from sepsis yearly (1). It commonly affects neonates and children; however, pregnant women, the elderly, cancer patients, and bed-bound individuals are particularly at high risk of developing sepsis as well due to the immunosuppressant state of their condition. Sepsis is a clinical diagnosis; thus majorly depends upon a multitude of symptoms, clinical examinations, baseline investigations, and the expertise of the clinicians. Unfortunately, all these methods are highly non-specific, making the diagnosis difficult. Owing to its high mortality, the key to survival lies in the timely initiation of the therapy. Therefore, sepsis requires early diagnosis to help save the life of an affected individual. In this search, multiple systems and methods have been developed previously and used in various hospitals. It includes evaluating by SIRS criteria, detecting the levels of pro-inflammatory markers in the serum, and by newer techniques like diagnosing using electrochemical sensors like PCT (procalcitonin), optical and fluorometric sensors, and microfluidic sensors. These detect different biomarkers in the serum of the patients and thus help in rapid diagnosis. Regardless, the sensitivity and specificity of these systems remain low. ---Continue

Development of water-dispersible Dy(III)-based organic framework as a fluorescent and electrochemical probe for quantitative detection of tannic acid in real alcoholic and fruit beverages

Tannic acid (TA) is a water-soluble polyphenol and used in beverages, medical fields as clarifying and additive agents. In daily life, TA is unavoidable, and excessive consumption of tannin containing foods can harm health. Thus, rapid and sensitive quantification is highly necessary. Herein, an eco-friendly fluorometric and electrochemical sensing of TA was developed based on a dysprosium(III)-metal-organic framework (Dy(III)-MOF). An aqueous dispersion of Dy(III)-MOF exhibits strong dual emissions at 479 and 572 nm with an excitation at 272 nm, due to the 4f-4f electronic transition and “antenna effect”. Chromophore site of the functional ligand, and Dy(III) ion could potentially serve as a sensing probe for TA via quenching (fluorescence). The fluorometric sensor worked well in a wide linear range concentrations from 0.02 to 25 μM with a limit of detection (LOD) of 0.0053 μM. Secondly, the cyclic voltammetric of TA at Dy(III)-MOF modified screen-printed carbon electrode (SPCE) has been investigated. The Dy(III)-MOF/SPCE showed an anodic peak signal at +0.22 V with a five-fold stronger current than the control electrode surface. Under optimized sensing parameters, the Dy(III)-MOF/SPCE delivered wide linear concentrations from 0.01 to 200 μM with a LOD of 0.0023 μM (S/N = 3). Accessibility of real practical samples in alcoholic and juice-based beverages were quantified, resulting in superior recovery rates (98.13–99.53%), F-test, and t-test confirmed high reliability (<95% confidence level (n = 3)). Finally, practicability result of the electrochemical method was validated by fluorometric with a relative standard deviation (RSD) of 0.18–0.46 ± 0.17% (n = 3). The designed probe has proven to be a key candidate for the accurate analysis of TA in beverage samples to ensure food quality.

Pyridinic-N-rich carbon dots in IFE-based Turn-off Fluorometric detection of nerve agent Mimic- Diethyl chlorophosphate and multicolor cell imaging.

Fluorometric sensors for the detection of nerve agent mimics have received a lot of interest nowadays due to their high sensitivity and selectivity, ease of operation, and real-time monitoring. Pyridinic-N-rich carbon dots (NCDs) prepared through microwave-assisted pyrolysis of l-Malic acid and urea have been explored first time in this work as a novel turn-off fluorescent probe for the sensitive and selective detection of diethyl chlorophosphate (DCP), a nerve agent mimic. The as-prepared carbon dots contained a large amount of pyridinic nitrogen on their surface, which can modulate the photoluminescence properties of the NCDs. The blue emissive NCDs possessed both excitation wavelength-dependent and independent emission behavior. The detection of DCP was premised on quenching of the fluorescence emission intensity of NCDs in the presence of similar chemical reagents (e.g., trimethyl phosphate, triethyl phosphate, triethyl phosphonoacetate, triphenyl phosphate, diphenyl phosphate, tributyl phosphate). Fluorescence quenching of the NCDs in the presence of DCP has been attributed to the inner filter effect (IFE). From the linear Stern-Volmer plot (R2=0.9992), the limit of detection (LOD) was found to be 84μM for sensing DCP for the concentration ranging between 3 and 15mM. The biocompatibility of NCDs was assessed through cytotoxicity assay on MDA-MB-231 breast cancer cells. Fluorescence imaging demonstrated that NCDs have low cytotoxicity and can be employed successfully in cell imaging.

A novel diarylethene-based fluorescence sensor for Zn2+ detection and its application

A series of fluorometric sensors of Zn2+ have been synthesized due to the significant function of Zn2+ in the human body and environment. However, most of probes reported for detecting Zn2+ have high detection limit or low sensitivity. In this paper, an original Zn2+ sensor, namely 1o, was synthesized by diarylethene and 2-aminobenzamide. When Zn2+ was added, the fluorescence intensity of 1o increased by 11 times within 10 s, along with a fluorescence color change from dark to bright blue, and the detection limit (LOD) was calculated to be 0.329 μM. According to Job’s plot curves, the binding mode of 1o and Zn2+ was measured as 1:1, which was further proved by 1H NMR spectra, HRMS and FT-IR spectra. The logic circuit was designed to take advantage of the fact that the fluorescence intensity of 1o can be controlled by Zn2+, EDTA, UV and Vis. In addition, Zn2+ in actual water samples were tested, in which the recovery rate of Zn2+ was between 96.5 % and 109 %. Furthermore, 1o was successfully made into a fluorescent test strip, which could be used to detect Zn2+ in the environment economically and conveniently.

Role of Noncovalent Interactions in N,P-Functionalized Luminescent Carbon Dots for Ultrasensitive Detection of Moisture in D2O: Boosting Visible-NIR Light Sensitivity.

It is highly desirable to design cost-efficient and eco-friendly fluorometric sensors that can efficiently detect water contamination in D2O and other expensive organic solvents. Herein, we have synthesized N,P-codoped carbon dots (N,P-CDs) from o-phenylene diamine (o-PDA) and H3PO4 through the bottom-up carbonization method. Heteroatom co-doping increases the absorption cross section in the visible-NIR range, followed by the formation of stable emissive states in longer-wavelength regions. We have critically investigated the noncovalent interactions (especially H-bonding interactions) of various surface functional groups with surrounding solvent media through a detailed structure-property correlation. Based on the sensitivity of noncovalent H-bonding interactions to the stability of longer-wavelength emissive domains, we have utilized these N,P-CDs as cost-effective fluorometric sensors of water/moisture contamination in D2O especially under visible-NIR light; the optical sensitivity reaches up to 0.1 volume (%) level. The detailed sensing mechanism has been further supported by a computational study through a simple visualization approach by mapping and analyzing all possible noncovalent interactions between the CDs and the solvent medium.

A simple paper-based nickel nanocluster-europium mixed ratio fluorescent probe for rapid visual sensing of tetracyclines

In this work, a ratiometric fluorometric sensor based on nickel nanoclusters (NiNCs)-europium complex (NiNCs-Eu3+) was constructed for the highly selectivity detection of tetracyclines (TCs) in water samples. In the presence of TCs, the blue fluorescence of the sensor NiNCs-Eu3+ was quenched at 430 nm and the characteristic red fluorescence of Eu3+-TCs appeared at 620 nm because of the combined help of inner filter effect (IFE) and antenna effect. Under the optimized conditions (100 mM Eu3+ (100 µL); temperature (25℃); reaction time (10 min), HEPES buffer solution (pH = 7.0)), the sensor offered a wide detection range of tetracycline (TC) and oxytetracycline (OTC) from 0.1 to 50 μM with the detection limit (LOD) of 25 nM and 21 nM, respectively. Moreover, the sensor was able to detect of TC and OTC in tap and lake water with high recovery rate (89.10%-97.60%). In addition, the portable paper-based sensor was constructed using filter paper embedded with NiNCs-Eu3+. The distinct fluorescent color of the paper-based sensor varied from bright blue to red against different concentrations of TC and OTC. These above findings demonstrated the potential for wide application of as-prepared ratio metric fluorescence sensor for visual detection of TCs in water samples.

Functionalized vanadium disulfide quantum dots as a novel dual-mode sensor for ultrasensitive and highly selective determination of rutin

A reliable electrochemical and fluorometric sensor was proposed for ultrasensitive and selective determination of rutin. It consists of vanadium disulfide quantum dots (VS2 QDs) functionalized with hydropropyl-β-cyclodextrin (β-CD). The as-fabricated sensor was characterized using Transmission electron microscope (TEM), UV–vis spectroscopy, fluorescence spectroscopy, Fourier transform infrared spectroscopy (FTIR), energy dispersive X-ray (EDX), cyclic voltammetry (CV), and differential pulse voltammetry (DPV). The electrochemical method is based on the direct oxidation of rutin at β-CD-VS2 QDs/GCE, while the fluorometric method is based on the quenching of β-CD-VS2 QDs fluorescence emission via inner-filter effect (IFE). It was found that the fluorescence emission was decreased with rutin addition in the concentration range of 0.058–45.0 µM with a detection limit (S/N = 3) of 18.0 nM. For the electrochemical analysis, the current response (Ipa) was increased with rutin addition in the concentration range of 0.005–1.4 × 10−8 M with a detection limit (S/N = 3) of 1.6 nM. The proposed dual-mode sensor exhibits many advantages including low detection limit, simplicity, cost-effectiveness, and allows for convenient operation, thereby rendering it a promising and reliable for the detection of rutin in various matrices.

Natural Nitrogen-Doped Carbon Dots Obtained from Hydrothermal Carbonization of Chebulic Myrobalan and Their Sensing Ability toward Heavy Metal Ions.

Chebulic Myrobalan is the main ingredient in the Ayurvedic formulation Triphala, which is used for kidney and liver dysfunctions. Herein, natural nitrogen-doped carbon dots (NN-CDs) were prepared from the hydrothermal carbonization of Chebulic Myrobalan and were demonstrated to sense heavy metal ions in an aqueous medium. Briefly, the NN-CDs were developed from Chebulic Myrobalan by a single-step hydrothermal carbonization approach under a mild temperature (200 °C) without any capping and passivation agents. They were then thoroughly characterized to confirm their structural and optical properties. The resulting NN-CDs had small particles (average diameter: 2.5 ± 0.5 nm) with a narrow size distribution (1-4 nm) and a relatable degree of graphitization. They possessed bright and durable fluorescence with excitation-dependent emission behaviors. Further, the as-synthesized NN-CDs were a good fluorometric sensor for the detection of heavy metal ions in an aqueous medium. The NN-CDs showed sensitive and selective sensing platforms for Fe3+ ions; the detection limit was calculated to be 0.86 μM in the dynamic range of 5-25 μM of the ferric (Fe3+) ion concentration. Moreover, these NN-CDs could expand their application as a potential candidate for biomedical applications and offer a new method of hydrothermally carbonizing waste biomass.

High-frequency monitoring through in-situ fluorometric sensors: A supporting tool to long-term ecological research on lakes

Lake Maggiore is a site of the Long-Term Ecosystem Research (LTER) network, belonging to the deep subalpine Lake District in Northern Italy. Studies on the physical, chemical, and biological features of the lake have been performed continuously since the 1980s. The lake recovered from eutrophication reaching the present oligotrophic condition. In the last decade, climate change represents the main driving factor for the long-term evolution of the lake, affecting its hydrodynamics, nutrient status, and biological communities. In 2020 a high-frequency monitoring (HFM) system was deployed, with the aim to integrate long-term monitoring based on discrete sampling and analysis. The system consists of a buoy equipped with sensors for limnological variables and algal pigments. The high-frequency monitoring program is part of a cross-border project between Italy and Switzerland focusing on lake quality monitoring as a critical input for successful lake management. In this paper we focus on Chlorophyll-a data, with the aim to test whether in-situ fluorescence measurements may provide a reliable estimate of lake phytoplankton biovolume and its seasonal dynamic. Sensor’s performance was regularly tested comparing chlorophyll-a data taken by the in-situ fluorescent sensors (Cyclops7, Turner Design), data from laboratory fluorescence analysis (FluoroProbe, BBE Moldaenke), values obtained from chlorophyll-a analysis by UV-VIS spectrophotometry and data from phytoplankton microscopy analysis. We found a general good agreement between the Chlorophyll-a data obtained with the different methods, confirming the use of in-situ sensors as a reliable approach to measure algal pigments, especially to assess their variability in the short-term, but also to describe the seasonal pattern of phytoplankton biovolume. However, phytoplankton community composition played a substantial role in the performance of the different methods and in the reliability of in-situ data as a tool to assess algal biovolume. This study demonstrates that high-frequency monitoring (HFM), used in conjunction with discrete chemical and biological monitoring, represents an important advance and support in the long-term monitoring of freshwaters and is a useful tool to detect ecological changes. Regular checking and validation of the sensor readings through laboratory analyses are important to get trustworthy data.

Optical sensor arrays for the detection and discrimination of natural products.

Covering: up to the end of 2022Natural products (NPs) have found uses in medicine, food, cosmetics, materials science, environmental protection, and other fields related to our life. Their beneficial properties along with potential toxicities make the detection and discrimination of NPs crucial for their applications. Owing to the merits of low cost and simple operation, optical sensor arrays, including colorimetric and fluorometric sensor arrays, have been widely applied in the detection of small molecule NPs and discrimination of structurally similar small molecule NPs or complex mixtures of NPs. This review provides a brief introduction to the optical sensor array and focuses on its progress toward the detection and discrimination of NPs. We summarized the design principle of sensor arrays toward various NPs (i.e., saccharides and polyhydroxy compounds, organic acids, flavonoids, organic sulfur compounds, amines, amino acids, and saponins) based on their functional groups and characteristic chemical properties, along with representative examples. Moreover, the challenges and potential directions for further research of optical sensor arrays for NPs are proposed.

CsPbBr3 perovskite quantum dot decorated ZIF-8 MOF: a selective dual recognition fluorometric visual probe for 4-nitroaniline and rhodamine blue.

The uses of highly luminescent perovskite quantum dots in real analytical detection were limited by their supersensitive nature. Here, we have designed a CsPbBr3 perovskite based fluorometric sensor by integrating them with a zeolitic imidazole framework (ZIF-8) via an in situ one step technique and established its stability in aqueous and other polar solvents. The CsPbBr3@ZIF-8 luminescence sensor functioned excellently for the trace detection of 4-nitroaniline and rhodamine blue dye molecules with a detection limit value of 8.367 ppb and 0.088 ppm, respectively. A comprehensive investigation found that the quenching of the fluorescence signal occurred via fluorescence resonance energy transfer (FRET) for rhodamine blue dye and a H-bonding interaction induced trap density mediated quenching mechanism was responsible for 4-NA detection. The potential of this suggested sensor as a cheap portable test paper probe for analyte detection was also explored. This study introduces CsPbBr3 as a cutting-edge sensing platform for industrial pollutants such as dye molecules and nitroaromatics.

An AIE active fluorescence sensor for measuring Fe3+ in aqueous media and an iron deficiency anemia drug.

In this study, a new tetraphenylethene derivative bearing triazole and pyridine moieties (TPE-TAP) was synthesized using click chemistry. The fluorescence sensing properties of TPE-TAP were investigated in almost 100% aqueous media. For this purpose, first of all, structural characterization of the newly synthesized compound TPE-TAP was performed by NMR and HRMS analyses. Then, the optical behavior of TPE-TAP was investigated in different ratios of a THF-water mixture (0-98%). The obtained results showed that the best fluorescence for TPE-TAP was observed in the presence of 98% water in the medium. Then, the ion selectivity of TPE-TAP was determined using 19 different cations in the THF-water medium (2 : 98 v/v%). It was observed that among the cations studied, only Fe3+ quenched the fluorescence of TPE-TAP. The detection limit and binding constant values of TPE-TAP for Fe3+ were calculated as 1.3 μM and 26.65 M-2, respectively, from the graph results of the decrease in the fluorescence intensity of TPE-TAP in the presence of Fe3+ at different concentrations. In addition, the study investigating the selectivity of TPE-TAP in the presence of 18 cations other than Fe3+ showed that none of the studied cations interfered with Fe3+. Practical application of TPE-TAP was also carried out using a commercial iron drug. All results showed that TPE-TAP is a fluorometric sensor highly selective, sensitive, and suitable for practical application for Fe3+ ions in aqueous medium.

Fluorescence and colorimetric‐based sensing of Hg2+ and Cu2+ using rhodamine derivative

Effective and simultaneous detection of multimetal ions has been achieved by a colorimetric and fluorometric sensor (RA), which was fabricated between rhodamine hydrazide and 9‐anthraldehyde through a simple Schiff base reaction. Sensor RA provided an effective platform for reliable detection of Hg2+ with a detection limit as low as 9.978 × 10−9 and displayed fabulous sensitivity for Cu2+ with a low limit of detection (LOD) of 4.81 × 10−8 M of detection limit toward Cu2+. Among them, the detection limit for heavy metal mercury ions has reached the ultrasensitive level. The sensing mechanism between RA and metal ions was further confirmed by 1H NMR and IR titration experiments and high‐resolution mass spectrometry and discussed from a theoretic level based on crystal structures and density functional theory (DFT) calculations. The switch in turn‐on signaling was attributed to the spiro‐lactam and ring‐opened form of RA and was accompanied by significant changes in ultraviolet spectroscopy and fluorescent spectrum.