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A new rhodamine B derivative (RDB) was synthesized and utilized for the colorimetric detection of copper ions (Cu2+). This chemosensor utilized a paper strip as a support and a smartphone as a detector for on-site quantitative detection of Cu2+ in water samples. Silica nanoparticles (SiNPs) were investigated as the modifier nanoparticles to achieve uniform color on the paper strip and showed a color response 1.9-fold higher than the one without SiNPs. The RDB chemosensor-based paper strip provided high selectivity toward Cu2+ with a detection limit of 0.7 mg/L, and the working concentrations for Cu2+ ranged from 1 to 17 mg/L. Parallel analyses of eight drinking water samples were conducted by inductively coupled plasma optical emission spectroscopy. The results were in good agreement, indicating the practical reliability of the established method with a short assay time and high selectivity. These indicate its great potential for on-site detection of Cu2+. [ABSTRACT FROM AUTHOR]

The distribution of tiny sensors over a specific area was first proposed in the late 1990s as a concept known as smart dust. Several efforts focused primarily on computing and networking capabilities, but quickly ran into problems related to power supply, cost, data transmission, and environmental pollution. To overcome these limitations, we propose using paper-based (confetti-like) chemosensors that exploit the inherent selectivity of chemical reagents, such as colorimetric indicators. In this work, cheap and biodegradable passive sensors made from cellulose could successfully indicate the presence of hazardous chemicals, e.g., strong acids, by a significant color change. A conventional color digital camera attached to a drone could easily detect this from a safe distance. The collected data were processed to define the hazardous area. Our work presents a combination of the smart dust concept, chemosensing, paper-based sensor technology, and low-cost drones for flexible, sensitive, economical, and rapid detection of hazardous chemicals in high-risk scenarios. [ABSTRACT FROM AUTHOR]

An afterglow is beneficial as an emission signal in the field of displays and imaging probes. Here, boronic acid‐appended and spirolactam ring‐containing rhodamine dye 1 was synthesized and grafted onto the surface of room‐temperature phosphorescence‐active boronate nanoparticles (BPs), composed of polymeric 3‐benzo‐2,4,8,10‐tetraoxa‐3,9‐diboraspiro[5.5]undecane. The resultant ensemble, 1@BP, exhibited a greenish afterglow. However, the addition of Al3+ into the dispersion solution with 1@BP led to a change in the afterglow to grass green as a result of Förster‐type energy transfer from the phosphorescent BP to the Al3+‐interacting rhodamine dye 1 on the surface. Based on the ratio of the two emission intensities, a linear response in the concentration range of 3.8–15.2 μM was observed, with a detection limit of 4.2 μM for Al3+. A metal ion‐dependent discernable color in afterglow was observed on a 1@BP‐coated filter paper, which would be useful for not only film‐based afterglow chemosensors but also encryption application. [ABSTRACT FROM AUTHOR]

[Display omitted] • New Schiff base sensor R4P developed using Rhodamine B fluorophore. • Highly sensitive and selective towards Al3+/Cu2+ in two solvent systems. • Low LOD, high K A , good anti-interference and reversibility properties. • Fabrication of strip for on-site detection using chromatography paper. • Low cytotoxicity of R4P makes it suitable for bio-imaging studies. In order to create a new Schiff base sensor R4P , rhodamine B hydrazide was directly combined with 4-propoxybenzaldehyde. The structure of this new sensor was completely revealed by spectroscopic methods, and a single crystal that could be used for X-ray diffraction techniques was produced. Under a UV lamp, the colourless and non-fluorescent R4P solution exhibits an orange fluorescence enhancement when Al3+ is present and showed a pink colour change when Cu2+ is present. Spectroscopic tools like UV, fluorescence, MS and NMR spectroscopy were used to study the recognition performance and complexation process of the sensor. The findings demonstrated that sensor R4P , with a limit of detection as low as 10-8 M and an association constant of ×104 M−1, is highly sensitive and selective towards both Al3+ and Cu2+ in two different solvent systems. Additionally, the designed system had a reasonable recovery range of above 89% for Al3+ and Cu2+ in two chosen water samples of natural mineral water and tap water. Moreover, a paper-based test strip that can detect target metal ions both colorimetrically and fluorometrically was created utilising chromatography paper. Aside from that, R4P 's minimal cytotoxicity marks it appropriate for bio-imaging studies on metal ion sensing using the fluorescence response in the HCT 116 cell line. [ABSTRACT FROM AUTHOR]

Remarkable efforts have been dedicated to paper-based chemosensors and biosensors over the last few years, mainly driven by the promise of reaching the best trade-off between performance, affordability and simplicity. Because of the low-cost and rapid prototyping of these sensors, recent research has been focused on providing affordable diagnostic devices to the developing world. The recent progress in sensitivity, multi-functionality and integration of microfluidic paper-based analytical devices (µPADs), increasingly suggests that this technology is not only attractive in resource-limited environments but it also represents a serious challenger to silicon, glass and polymer-based biosensors. This review discusses the design, chemistry and engineering aspects of these developments, with a focus on the past few years. [ABSTRACT FROM AUTHOR]

A novel naphthalimide-based colorimetric and fluorescent turn-on chemosensor for Al3+ was synthesized and characterized with spectroscopic techniques. In MeOH solution, BPAM showed high selectivity and sensitivity to Al3+ by a 60-fold fluorescence enhancement and blue-shift absorption with visible color changes attributed to the contribution of chelation enhanced fluorescence (CHEF) and inhibition of intramolecular charge transfer (ICT). A 1:1 BPAM-Al3+ complex confirmed by job’s plot and HRMS with a binding constant of 6.37 × 104 M− 1, and the detection limit for Al3+ was as low as 1.59 × 10− 7 M. BPAM was successfully applied in real sample detection and assessing the existence of Al3+ by a colorimetric method on filter paper. Furthermore, the fluorescent signals of BPAM were designed to construct an INHIBIT molecular logic gate. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new rhodamine based chemosensor 1 was synthesized and characterized. • Selectively detect Co2+/Cu2+ in different solvent systems (MeCN and DMF). • Sensor 1 as copper (II) ion detector can be reused with proper treatment. • Filter paper test strip for detection of Co2+ and Cu2+ in pure aqueous solution. • Sensor 1 showed no significant cytotoxicity towards CCD-18Co and HT-29 cell lines. A new chemosensor 1 was synthesized by reacting rhodamine B hydrazide and 2,3,4-trihydroxybenzaldehyde, which was then characterized by spectroscopic techniques and single crystal X-ray crystallography. Sensor 1 has the ability to sense Co2+/Cu2+ ions by "naked-eye" with an apparent colour change from colourless to pink in different solvent system, MeCN and DMF respectively. Furthermore, it can selectively detect Co2+/Cu2+ among wide range of different metal ions, and it exhibits low detection limit of 4.425 × 10−8 M and 1.398 × 10−7 M respectively. Binding mode of the two complexes were determined to be 1:1 stoichiometry for Co2+ complex and 1:2 stoichiometry for Cu2+ complex through Job's plot, IR spectroscopy, mass spectrometry and 1H NMR spectroscopy. Moreover, reversibility of the sensor 1 as copper (II) ion detector was determined by using EDTA and the results showed that sensor 1 can be reused for at least 6 cycles. Other than that, a low cost chemosensor test strips were fabricated for the convenient "naked-eye" detection of Co2+ and Cu2+ in pure aqueous media. The MTT assay was conducted in order to determine the cytotoxicity of sensor 1 towards human cell lines. [ABSTRACT FROM AUTHOR]

• Synthesis of novel oxazolidine derivatives with ionochromic properties. • Application of the oxazolidine molecules for photodetection of metal ions by colorimetric and fluorometric methods. • Selective sensing of Fe3+ and Ag+ in aqueous solution by development of metal ion chemosensors. • Preparation of ionochromic papers with the printing ability of security marks by using metal ion solutions as the ink. Photodetection of metal ions in different environments is a noteworthy research. Some sensitive oxazolidine derivatives were synthesized and their responsivities toward different metal ions were investigated. The OX 1 and OX 2 derivatives were synthesized from 2,3,3-trimethylindolenin and 1,1,2-trimethylbenz[e]indole, respectively. In addition, two hydroxyl and naphthalene functionalities were applied to both of the OX 1 and OX 2 derivatives to obtain OX 1 -OH and OX 2 -OH and also OX 1 -Naph and OX 2 -Naph derivatives, respectively. Investigation of ionochromic properties of oxazolidine derivatives showed their potential applications as highly-selective and sensitive optical chemosensors for detection of metal ions. The results showed colorimetric and fluorometric photodetection of Fe3+ ions in aqueous solution, where OX 2 -NaPh displayed selective photodetection of Ag+ in addition to Fe3+. For the development of paper-based colorimetric/fluorometric metal ion chemosensors and also high-security anticounterfeiting technology, ionochromic cellulosic papers based on oxazolidine derivatives were prepared via layer-by-layer coating strategy, which showed fluorescence emission in different colors with impregnation in aqueous solution of Fe3+ or Ag+. In addition, the Fe3+ and Ag+ aqueous solutions were used as anticounterfeiting ink for handwriting and printing on the ionochromic papers with pink, cyan blue, and dark blue fluorescence emissions of the written or printed marks. Therefore, the prepared ionochromic cellulosic papers have potential applications as colorimetric/fluorometric metal ion chemosensors and also in anticounterfeiting technology based on ionochromic security papers. Photodetection of metal ions by development of fluorometric/colorimetric chemosensors, and also anticounterfeiting technology based on oxazolidine derivatives. [Display omitted] [ABSTRACT FROM AUTHOR]

In this paper, isatin-hydrazone was synthesized using SBA-Pr-N-Is-But-SO3H as nanocatalyst via the two-component reaction of isatin with hydrazine hydrate in an expeditious reaction with high yield of production. The sensing properties were evaluated in EtOH: H2O (1:9) for the different cation (K+, Ca2+, Na+, Cu2+, Zn2+, Cr3+, Mn2+, Co2+, Al3+, Pb2+, Ag+, Cd2+, Ni2+, Hg2+, and Mg2+). The obtained results revealed that these compounds could be applied as chemosensor for the sensitive detection of Hg2+ and Ag+ ions using UV–Vis spectroscopy and fluorescence spectroscopy, respectively. The detection limit was calculated to be 1.17 × 10–6 M for Hg2+ ions and 1.4 × 10–6 M for Ag+ ions. Also, isatin-hydrazone was treated with 4-flurobenzaldehyde to obtain 4-fluorobenzaldehyde-N-(2-oxo-1,2-dihydro-3H-indole-3-indole-3-ylidene)hydrazone which could sensitively select Hg2+ ions among different ions using fluorescence spectroscopy. The detection limit of the colorimetric sensor to detect the Hg2+ ions is 3.6 × 10–6 M. At the end of the reaction, the nanocatalyst was recovered and reused. [ABSTRACT FROM AUTHOR]

[Display omitted] • Probe RD6G-1 can be utilized as a colorimetric paper test strip smartphone chemosensor for detection of Pb2+ in meat samples. • The AuNPs enhanced of the paper test strip chemosensor showed 9 orders of magnitude for Pb2+ detection. • Quantitative detection readout with a smartphone could be achieved within only 1 min. • Excellent accuracy and selectivity were confirmed by the detection of Pb2+ in food samples. A rapid and selective colorimetric chemosensor based on a paper test-strip platform and smartphone detection were investigated to determine lead ions (Pb2+) in meat samples. The colorimetric chemosensor for Pb2+ analysis, the rhodamine 6G −1 (RD6G −1 probe), was synthesized through the Schiff base formation of rhodamine 6G hydrazide and 3,4,5-trimethoxybenzaldehyde. The Pb2+ sensing process was accomplished by the color on the detection zone change from colorless to pink within 1 min. The proposed chemosensor strip was functionalized with (3-aminopropyl)triethoxysilane and gold nanoparticles (AuNPs) to enhance the colorimetric response. Under the optimal conditions, the color intensity of the chemosensor strip increased linearly with the Pb2+ concentrations in the range of 0.1–1.0 mg/L. This developed strip allowed low detection limit (0.12 mg/L). The paper test strip modified with AuNPs provided a color response 9-fold higher than the one without AuNPs. Moreover, the paper test strip was successfully applied for Pb2+ analysis in meat samples, consistent with the inductively coupled plasma-mass spectrometry method.This work showed the proposed smartphone-based paper test-strip chemosensor offers a highly selective and accurate quantitative detection of Pb2+ ions without the additional equipment. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

We have constructed a novel fluorescein-based fluorescent chemosensor, FL-In, functionalised with an indole moiety and capable of sensing by both the optical "turn-on" and electrochemical detection of carbonate ions (CO32−) in aqueous media. The probe exhibits excellent selectivity and a low detection limit (0.27 µM) regarding carbonate ions by a possible coordination and hydrolysis reaction mechanism. The developed probe successfully detected CO32− ions in different samples of water. Also, in a simple filter paper experiment, we documented its ability to allow the monitoring of CO32− with the naked eye. [ABSTRACT FROM AUTHOR]

Hypochlorous acid (HClO) as well as its ionic form (ClO−), representative of reactive oxygen species (ROS), are essential players in all sorts of biological processes. The abnormal level of each can lead to the onset of various diseases. Besides, Sodium hypochlorite, a commonly-used bleaching agent in our daily lives, could also result in breathing and skin problems when overexposed. Therefore, developing a molecular chemosensor for sensing HClO is of biological and environmental importance. Though many such chemosensors have been reported, new HClO chemosensors with different sensing performances may still come in handy in certain situations. In this work, we have developed a new coumarin-based chemosensor, CM-hbt , for realizing both ratiometric and colorimetric imaging detection of HClO in live cells. Notably, we further explored its application in sensing HClO in plant mung beans as well as fabricated an easy-to-use paper strip apparatus for facilitating its quick detection, which is seldomly seen in other HClO chemosensors. All the analysis results confirmed the high sensitivity and selectivity of this novel chemosensor. DFT calculations were used to decipher the underlying sensing mechanism of CM-hbt. Overall, this work presents a novel chemosensor, CM-hbt , as a colorimetric and ratiometric chemosensor for realizing imaging detection of HClO in a variety of different model systems, which highlights its broad spectrum of application potentials. [Display omitted] • A new chemosensor CM-hbt was developed and well-characterized by UV–vis and fluorescence spectra, NMR, and MS analysis. • CM-hbt can track HClO changes with LOD-545 nM, within 100 s via a highly selective colorimetric and ratiometric response. • CM-hbt has realized imaging tracking of exogenous/endogenous HClO variations in live cells. • CM-hbt has realized imaging tracking of HClO in mung bean sprouts and paper strips. • The sensing mechanism of CM-hbt was confirmed by DFT calculations. [ABSTRACT FROM AUTHOR]

A derivative of fluorescein was designed, synthesized, and characterized by FT-IR, 1H, 13C NMR, mass spectrometry, and quantum chemical calculations. When applied to the set of solutions containing different cations, it has shown a selective colorimetric and fluorescence response for Cu2+. A visible color change from colorless to purple and from non-fluorescent to red fluorescence was observed. A linear relationship between Cu2+ concentration and absorbance or fluorescence intensity was demonstrated with low detection limits (0.64 and 0.24 μM, respectively) in the acetonitrile/water mixture. Test strips are made by impregnating filter paper with acetonitrile chemosensor 1 solution and used to detect Cu2+ in water. The strips noticeably change their color from colorless to purple. • Chemosensor 1 has been designed and synthesized for selective recognition of Cu2+. • Structure of 1 has been confirmed by 1H, 13C NMR, FT-IR, and mass spectrometry. • Cu2+ ions cause visible color change of the hydrazone solution. • Cu2+ ions turn-on the red fluorescence of the chemosensor. • The limit of detection value is 0.24 μM. [ABSTRACT FROM AUTHOR]

• A paper-based chemosensor with smartphone reflectometry detection relying on the F C assay was developed for direct total polyphenols analysis. • 3D printing and PDMS replica molding technologies were used to develop all-in-one analytical device for on-site polyphenols quantification. • The chemosensor has been applied to measure polyphenols in extra virgin olive oil and aqueous food matrices. High polyphenols levels are one of the main quality characters of Extra Virgin Olive Oil (EVOO), leading to high antioxidant activity and contributing to the EVOO health beneficial effects. Analytical methods for the rapid assessment of EVOO polyphenols content, possibly directly at the place of production or distribution, are therefore important for the commercial enhancement of this product. Unfortunately, most analytical methods for quantification of polyphenols in EVOO require laboratory instrumentation and preliminary sample extraction procedures. In this paper we describe a paper-based chemosensor based on the well-known Folin-Ciocalteu colorimetric assay for the rapid (assay time 15 min) quantitative detection of polyphenols in EVOO without any preliminary sample extraction. Use of n-propanol for diluting the EVOO sample allows its direct analysis on paper supports loaded with the Folin-Ciocalteu reagent. The color change of the paper supports is measured using a smartphone camera. A disposable analytical cartridge containing all necessary reagents, including calibration standards, and accessories for performing the assay using a Samsung S8 smartphone have been developed to perform on-site analysis. Measurement of total polyphenol content of EVOO samples gave results in good agreement with the conventional Folin-Ciocalteu assay, and the limit of detection was 30 μg gallic acid equivalents g−1 EVOO. The same approach can be employed to measure polyphenols in other oils of vegetal origin. [ABSTRACT FROM AUTHOR]

A coumarin-based chemosensor was developed with excellent dual-mode detection capability for ClO− and N 2 H 4 based on different reaction mechanisms, which provides a strategy for the design of dual-channel responsive chemosensor for visualizing ClO− and N 2 H 4 in environment and biological samples. • A dual responsive chemosensor for hypochlorite and hydrazine was developed. • Different response signals based on different reaction mechanisms for hypochlorite and hydrazine. • A user-friendly test paper strip soaked with the chemosensor for hypochlorite. • Good recovery was achieved in real water samples for detecting hydrazine. A chemosensor was synthesized conveniently by the condensation between 7-diethylaminocoumarin and barbituric acid, which was used successfully for the detection of hypochlorite and hydrazine with excellent performances. This chemosensor underwent remarkable color change and turn off fluorescence in solution, while revealed turn on fluorescence on the filter paper in the presence of hypochlorite. In addition, it exhibited obvious fluorescence enhancement in solution, while no fluorescence change on the test paper after addition of N 2 H 4. As a result, this chemosensor could be a potential candidate for hypochlorite and hydrazine in different media through two distinct response modes. It could realize the detection of hypochlorite in water with a low detection concentration of 2 μM by test strip, and trace hydrazine in aqueous solution and living HepG2 cells by the mean of fluorescence signal. Moreover, the sensing mechanisms of this chemosensor towards hypochlorite and hydrazine were suggested by HRMS and 1H NMR spectra, in which the coumarin structure was destroyed by hypochlorite and the barbituric acid was removed by hydrazine, respectively. [ABSTRACT FROM AUTHOR]

• A colorimetric and ratiometric fluorescence dual-mode responsive chemosensor was prepared to detect toxic oxalyl chloride. • The chemosensor could determine oxalyl chloride with high sensitivity (LOD: ∼95 nM), high selectivity and fast response. • The flexible and portable AC-HPD-based test strip could semi-quantitatively determine oxalyl chloride vapor. • The AC-HPD-based kit could respond toward oxalyl chloride vapor with obvious color and fluorescence alteration. The screening of highly toxic chemical vapor is critical for environmental monitoring and human health maintenance. Herein, we reported a chemosensor (AC-HPD) for rapid and specific detection of highly toxic oxalyl chloride vapor, which adopted anthracene carboxyimide as a fluorophore and 3-aminopropanol as the reaction site. Upon coupling of oxalyl chloride with NH and OH groups, AC-HPD exhibited remarkable colorimetric and ratiometric fluorescence dual-mode responses towards oxalyl chloride via the intramolecular charge transfer effect. AC-HPD could determine oxalyl chloride with features of rapid response, excellent specificity, low detection limit (95 nM), as well as obvious color and fluorescence change. Furthermore, AC-HPD-embedded test strip was successfully fabricated and used as a flexible sensing device for rapid, sensitive and visible monitoring oxalyl chloride vapor. [ABSTRACT FROM AUTHOR]

• Dicarbohydrazide-based chemosensors were synthesized and characterized by analytical techniques. • All the sensors were applied in selective sensing of Fe(III) ions with a LOD in the range of 2.71–39 µM. • Sensor L2 was applied for the development of molecular logic gate and molecular lock keypad. • L2 was successfully applied in test strip experiments and was able to detect Fe(III) in aqueous solution. Two new and two reference sensors L1 - L2 and R1 - R2 , respectively, based on the hydrazide core were synthesized in good yields (70–86 %). A variety of analytical methods, including NMR, HRMS, and single-crystal XRD, were used to characterize these sensors. Cyclic voltammetry, UV–visible absorption, and emission spectroscopies were then used to confirm the electrochemical and photophysical characteristics of these sensors. Moreover, theoretical calculations at the level of DFT and TD-DFT were carried out to compare the experimental findings with the theoretical ones. The sensors were found to exhibit luminescence attributed to singlet ligand-centered (1LC) transitions. Based on their luminescent properties and the previous literature reports where structurally analogous sensors have been used for the detection of metal ions, these sensors were investigated as selective chemosensors for Fe(III) detection, with a "turn-off" fluorescence behaviour in a binding stoichiometry of 1:1 = sensor:M(III) [M = Fe(III)] with a limit of detection of 2.71–39 µM, or 0.15–2.81 ppm. The mechanistic details regarding the sensing of Fe(III) ion by the sensors was provided by NMR, IR, XPS and UV-visible absorption spectroscopic studies. To increase the usefulness of the sensors, L2 was also applied for the successful fabrication of the molecular logic gate and molecular lock keypad. Paper strip test and sensing of Fe(III) contaminated water by the sensors accounted for the practical applicability of the sensors in real life. [Display omitted] [ABSTRACT FROM AUTHOR]

Toxic cations, including heavy metals, pose significant environmental and health risks, necessitating the development of reliable detection methods. This review investigates the techniques and approaches used to strengthen the sensitivity and selectivity of Schiff base fluorescent chemosensors designed specifically to detect toxic and heavy metal cations. The paper explores a range of strategies, including functional group variations, structural modifications, and the integration of nanomaterials or auxiliary receptors, to amplify the efficiency of these chemosensors. By improving selectivity towards targeted cations and achieving heightened sensitivity and detection limits, consequently, these strategies contribute to the advancement of accurate and efficient detection methods while increasing the range of end-use applications. The findings discussed in this review offer valuable insights into the potential of leveraging Schiff base fluorescent chemosensors for the accurate and reliable detection and monitoring of heavy metal cations in various fields, including environmental monitoring, biomedical research, and industrial safety. [ABSTRACT FROM AUTHOR]

Fresh air and clean water are essential constituents for the human population as well as for fauna and flora. Owing to the extreme toxicity of NACs and VOCs in physiological systems and their widespread presence in the environment, serious mitigation is required. The innovation of chemosensors for these two types of harmful organic contaminants (NACs i. e., nitroaromatics, and VOCs i. e., volatile organic compounds) have unfolded as a key research topic in recent decades, garnering a lot of attention due to their environmental, industrial and biological importance. In recent years, there has been a significant amount of research on both NACs and VOCs chemosensors. This Review article has recapitulated the latest development of fluorescent chemosensors especially small molecular frameworks from 2015 to 2022, for NACs and VOCs which has been discussed individually. In addition, the detection of NACs and VOCs on multiple platforms with a special focus on their mechanistic exploration, as well as their probable applications in natural water body specimens, vapor phase detection, and paper strip analysis have also been discussed. [ABSTRACT FROM AUTHOR]

[Display omitted] • A colorimetric chemosensor for the detection of Cr(III) and Co(II) chloride in the presence of LMI was synthesized. • The acceptable LODs as 0.58 and 0.90 μM were validated in isopropanol for Cr(III) and Co(II), respectively. • A TLC test strip was successfully employed for the visible multication detection by L. • Dispersion of L in water was shown as a selective FL chemosensor of Cr(III). The present study describes the chemosensing capability of an N 2 O 4 -donor tetrabenzodiaza-crown ether macrocyclic ligand derivatized by two pyridine side arms to afford the flexible macrocyclic ligand, 5,20-bis(pyridin-4-ylmethyl)-5,6,12,13,19,20,26,27octahydrotetrabenzo [e,i,o,s][1,4,11,14]tetraoxa[7,18]diazacycloicosine (PMHBOA). A selective colorimetric behavior of PMHBOA for the prompt detection of Cr(ΙΙΙ) and Co(ΙΙ) can be observed with naked eyes. The 1H, 13C{H} NMR, and infrared spectroscopy disclosed the ligand binding capability for selective metal ions, ascribed to a 1:1 complex formation with Cr(III) and Co(II) cations in isopropanol. The limit of detection (LOD) values were calculated as 580 and 850 nM for Cr(ΙΙΙ) and Co(ΙΙ), respectively, accompanied with suitable LOQs as 1.95 µM for Cr(III) and 2.85 µM for Co(II), respectively. The reusability was confirmed in the presence of ethylenediaminetetraacetic acid (EDTA). Moreover, a TLC-based fabricated paper strip successfully applied PMHBOA as a chemosensor for synchronous visible detection of Cr(III) and Co(II) in their alcoholic solution. Meanwhile, the observed color change along with the turn-off fluorescent of PMHBOA guaranteed a felicitous choice of candidate for Cr(III) in the presence of other library metal ions in isopropanol:H 2 O (9/1 v/v) solution. A fast separation test on the filter paper, impregnated with PMHBOA, was also employed to separate Cr(III) and Co(II) cations from aqueous solutions by recording UV–vis spectra. The 1H NMR spectroscopy supported the macrocycle ring and side arms as the parallel coordination site of PMHBOA with Cr(III) and Co(II). [ABSTRACT FROM AUTHOR]

A novel multimode colorimetric and fluorescent chemosensor was developed using an 8-hydroxy quinoline carbaldehyde Schiff base with a quinoline hydrazide probe (E)-2-((2-(quinolin-2-yl)hydrazineylidene)methyl)quinolin-8-ol (L). NMR (1H &13C), FTIR, and HR-mass spectral characterization techniques confirmed the probe L structural conformation. As Probe L contacts Pb2+ ions, a color change and turn-off emission can be visually detected in EtOH:H 2 O (1:1, v/v, pH = 7.21) medium. The probe displays a good emission at 440 nm due to the combined ESIPT and ICT process. The Pb2+ ion interacts with the probe and selectively quenches fluorescence by inhibiting ESIPT and >C N- isomerization. As per Job's plot, L-Pb 2+ complex formation occurred in a 1:1 stoichiometric ratio, with association constant (K a) and quenching constant (K sv) estimated at 1.52 × 105 M−1 and 4.12 × 105 M, respectively. The detection limits of Pb2+ by spectrophotometric and spectrofluorometric were 1.99 μM (41 ppb) and 23.4 nM (485 ppt), respectively. Additionally, the test paper kit and RGB tool were used to monitor the color changes of L with Pb2+ and the LOD was found to be 5.99 μM (125 ppb). Its recognition mechanism has been verified by 1H NMR, ESI-mass, and theoretical studies. [Display omitted] • Quinoline-Quinoline based probe (L) was Synthesized and Characterized by NMR, IR, and Mass. • Probe L shows visually detectable color change with Pb2+ via turn-off emission. • The LOD of Pb2+ by spectrophotometric and spectrofluorometric were 41 ppb and 485 ppt, respectively. • Used smartphone RGB tool and test paper kit for real-time Pb2+ ion detection. [ABSTRACT FROM AUTHOR]

[Display omitted] • D-A-D type chemosensor molecule (MPhTT) synthesis and its optical response to various analytes. • Fluorescent hydrogel film preparation by using MPhTT as cross-linker. • Anion, cation, acid, base detection by fluorescent hydrogel films. • Increasing chemosensing ability of the fluorophore by cross-linking in the preparation of polymer films. • Extended mechanical properties and swelling behaviors of the films. 2,5-Bis(4-hydroxy-3-methoxyphenyl)thiazolo[5,4- d ]thiazole (MPhTT) fluorophore as a donor–acceptor-donor (D-A-D) type sensor molecule is synthesized for further investigation of sensing ability of the molecule towards various anions and cations. The MPhTT molecule with strong photoluminescence (PL) has been determined to be sensitive against anions with an effective deprotonation mechanism. MPhTT molecule has been demonstrated to have a limited ability to recognize anions by PL response in the solution while selectively sensitive against CN− anion after being embedded into filter paper. Moreover, metal cations detection in the solution is impossible with the MPhTT fluorophore. The use of MPhTT dye as a cross-linker to prepare highly emissive PVA hydrogel films resulted in a reusable chemosensor for acid, base, CN− anion, and metal cations. The mechanical properties of the films and their swelling behavior have also been investigated to show their water-responsive mechanical properties and water intake ability for possible biomedical applications. These findings indicate that increasing the chemosensing ability of the dye by cross-linking of polymers can be used for many fluorophores as an innovative approach. The films with extended mechanical properties can be used for wound dressing, biosensors, moisture sensors, and many other applications. [ABSTRACT FROM AUTHOR]

In this paper, we studied the effect of increasing the conjugation in compound 3 on the proton transfer and aggregation‐induced emission properties. Compound 3 exhibited the dual absorption peak at 420 nm and 320 nm, which was redshifted by 50 nm compared to compound 2 (previous report). Compound 3 emits exhibited a peak at 530 nm with a Stokes' shift of 110 nm after photoexcitation at 420 nm. In a high polarity medium, the absorption and emission spectra of compound 3 showed redshifts of 50 nm and 20 nm, respectively. Further, compound 3 displayed the aggregation‐induced emission enhancement in THF/H2O (60 % v/v). Additionally, the proton transfer process in compounds 2 and 3 was evaluated through theoretical calculations via determining the relative free energies of possible tautomeric forms. It was determined that the small energy barriers for compound 2 in the S1 state suggested the presence of the proton transfer process; however, high energy barriers and high stabilization and Boltzmann population of 3.KK tautomeric form at S0 and S1 state for compound 3 discommoded the proton transfer process. Further, the aggregated form of compound 3 (20 μM; CH3OH/HEPES buffer (4 : 1; v/v) pH=7.04) was utilized to recognize Cu2+ ions with the lowest detection limit of 1.5 nM and Stern‐Volmer binding constant of 2.8×105 M−1. A noted decrease in the hydrodynamic size of compound 3 from 400 nm to 40 nm in the presence of Cu2+ ions confirmed the disaggregation with a decrease in emission intensity. Compound 3 was also employed as a Cu2+ ions recognizer in different collected samples with good percentage recovery. [ABSTRACT FROM AUTHOR]

2,4,6-Triarylpyridines (TAPs) represent a versatile class of N -heterocycles with broad applications in many fields. This study presents an investigation on photochemical properties and acidochromism behavior of novel 2,6-bis(4-(dodecyloxy)phenyl)-4-(4-substituted-phenyl)pyridine-based derivatives (1a - 1g). Photochemical study in dichloromethane (DCM) and acetone (ACT) solutions showed a small solvent effect for the TAP derivatives, except for the carbazole derivative 1a , which was characterized as the most emissive material in all conditions, but especially in DCM solution for blue emission (λ EM = 406 nm, ϕ f = 0.36). The presence of electron-donating groups at the 4-phenyl moiety contributes to more intense and redshifted emissions in both DCM and ACT solutions, as well as in the solid state. In aqueous ACT, while TAPs bearing EDGs such as 1a presented more intense emissions depending on the water fraction, an opposite effect was verified for fluorinated derivative 1f. The acidochromism of selected TAPs 1a and 1f (fluorinated derivative) in aqueous acetone was characterized by the decreasing of the emission intensity at 436 nm and 388 nm, respectively, in the presence of aqueous HCl for both TAPs, however, the protonated 1f showed strong emission in higher wavelength (λ EM = 476 nm) in acidic medium. A 1H NMR study allowed a better understanding of the structural features associated to the acidochromism. The photochemical and acidochromism results obtained for the TAP derivatives are strongly supported by computational results, and particularly noteworthy is the favoring of the resonance effect as consequence of the decreasing in the torsion angle between the 4-alkoxyaryl substituents and the pyridine core after protonation of 1f. The emissive properties and acidochromism capacity of 1a and 1f allowed the potential application of TAP-adsorbed paper strips as disposable sensors for qualitative detection of gaseous HCl. [Display omitted] • Nonconventional TAPs were synthesized in moderate yields. • Photochemical results showed emission up to 0.36 in DCM solution for compound 1a. • AIEE was observed for TAP with EDG, notably N -carbazole derivative 1a. • Selected compound 1f showed interesting acidchromism. • Computational results support the experimental data. [ABSTRACT FROM AUTHOR]

This paper represents the synthesis of 1,2,3-triazole appended Schiff base functionalized silanes as colorimetric sensors for the detection of Al (III) and molecular docking analysis with butyrylcholinesterase in Alzheimer's diseases. A Boolean molecular logic circuit based on the reversible nature for ligand 7a was built. The real sample analysis performed with the aluminium foil. [Display omitted] • 1,2,3-Triazole appended Schiff base functionalized silanes has been achieved via a copper-catalyzed azide-alkyne cycloaddition (CuAAC) click chemistry reaction. • Sensing behaviour of the synthesized compounds were evaluated towards various cations. • The binding mode of compound 7a with Al (III) was proven by NMR techniques. • The synthesized compounds (7a-c) were evaluated for cytotoxicity. • Molecular docking analysis was performed for compound 7a with the active site of soman-aged human butyryl cholinesterase in complex with the substrate analog butyrylthiocholine (PDB ID: 1P0P). The current article reports the synthesis of 1,2,3-triazole appended Schiff base functionalized silanes. The organosilane 7a used for the colorimetric detection of Al (III). The absorption studies have been performed, resulting in a limit of detection values of 1.28 × 10-7 M for the ligand7a.In order to validate the practical applicability of the synthesized probe, the real sample analysis has been performed with aluminium foil in distilled water. Further,the ligand 7a reversibility from [ligand 7a + Al (III)] complex upon EDTA addition can be utilised to build a molecular logic gate, with Al (III) and EDTA considered as inputs and the absorbance intensity at 433 nm considered as the output.The potential binding site of 7a for the Al (III) has been analysed by characterizing the metal–ligand complex using 1H NMR spectroscopy. The cytotoxicity assay of compounds 7(a-c) was performed using SAF-1 (ECACC n°00122301), rendering thenon-toxicity of synthesized compounds. The binding energy of −10.16 Kcal mol−1 demonstrated that the ligand 7a is a potent inhibitor for the butyrylcholinesterase enzyme and might be employed as an anti-Alzheimer agent in the future. [ABSTRACT FROM AUTHOR]

The present article highlights a pyrene-based probe for the detection of water in various organic solvents. It also gives an insight into DFT and TD-DFT calculations and can be applied for inkless writing and reusable paper strips. [Display omitted] • A pyrene-based probe has been synthesized for the detection of water in organic solvents. • Detection limit and fluorescence quantum yield have been calculated. • Theoretical calculations (both DFT and TD-DFT) were performed. • Practically, the probe can be used for inkless writing and rewritable paper strips. The present manuscript highlights a newly synthesized pyrene-based probe (PyQ), which has a high affinity for the detection of water in water-miscible organic solvents. The efficient probe followed the principle based on aggregation-induced emission and showed its potential behavior as a sensor by detecting water in common water-miscible organic solvents by the fluorometric method. The chemosensor PyQ has identified water separately from many other solvents as its emission maxima in presence of water is found near 510 nm while for others it is around 410 – 440 nm. Moreover, in different water-miscible solvents by increasing the percentage of water, fluorescence studies have been carried out and were found that increasing water content in organic solvents increased the fluorescence intensity of the PyQ as well as provided a redshift to the emission intensities. Furthermore, the response of PyQ towards pH and the LOD and LOQ of PyQ towards a low level of water content in different organic solvents were determined. TD-DFT studies were carried out in the aqueous phase to clarify the optical and electronic properties of the probe. The moisture detection capacity of PyQ in presence of silica gel desiccant was also showcased. Finally, the utilization of PyQ in inkless writing and in reusable or rewritable paper strips disclosed its potential for real-life applications, which strengthened its use as a water sensor. [ABSTRACT FROM AUTHOR]

B OHC b showed definite fluorescence reduction only to Cu SP 2+ sp and applied to paper-strip for the first time among chromone-based fluorescence chemosensors that detect Cu SP 2+ sp . On addition of Cu SP 2+ sp into B OHC b , the absorbance of 280 and 380 nm gradually increased and that of 340 nm decreased until the amount of Cu SP 2+ sp increased up to 1.25 equiv. In the SP 1 sp H NMR titrations (Figure S5), as Cu SP 2+ sp was added, all proton signals blurred due to the paramagnetic character of Cu SP 2+ sp , indicating that B OHC b interacted with Cu SP 2+ sp . In the FT-IR investigation (Figure S6), the carbonyl (C=O) and imine (C=N) peaks of B OHC b at 1643 and 1539 cm SP -1 sp were shifted to 1664 and 1563 cm SP -1 sp and the intensity of the hydroxyl peak at 3268 cm SP -1 sp was markedly reduced, after copper ion reacted with B OHC b . [Extracted from the article]

The work presented here describes the synthesis and comparative physiochemical studies of hybrid compounds C-1 to 5 of azobenzene A-1 and chalcone B-1, which exhibited the characteristic of both. Further, electron-withdrawing and donating substituents analogues have also been synthesized. The hybrid compound is unique in nature because it contains the phenolic -OH, - N = N -, as well as α,β-unsaturated enone functional groups. The photophysical properties of hybrid C-1 behaved more or less like the azobenzene moieties and showed the same pattern of UV–vis absorption as with the change in the polarity of the solvent and the change in the pH of the medium. Thus, in the non-polar solvent or in the water medium, the phenol form dominates with its yellow colour and in polar solvents shows an intense red colour of keto form. They show a dramatic quenching of fluorescence emission in the polar solvent. Furthermore, after screening, C-1 was found to show selective sensing of the aqueous CO 3 2− ion as well as minimally with PO 4 3- and show a characteristic colour change in an organic solvent such as CH3CN. A few ions also changed colour in DMF, but that was due to the only shifting of the tautomerization equilibrium from keto to enol form. The UV–vis as well as fluorescent spectral studies, determination of the detection limits, and binding constants illustrated significant sensing of CO 3 2− ions. A systematic study was performed to understand the binding interactions of the chemosensor by using Job's plot and time-dependent 1H NMR studies that supported the involvement of phenoloc -OH and β carbon of α,β-unsaturated system. The characteristic pattern of UV–vis and interaction mode was confirmed by DFT studies. The applicability of chemosensor C-1 was demonstrated by the development of a paper strip model to check the presence of CO 3 2− ions in different kinds of water in society. [ABSTRACT FROM AUTHOR]

• A Colorimetric chemosensor (MM) has been introduced to selectively cascade recognition of F − and alkaline earth metal ions. • The limit of detection (LOD) of F − ions could be possible down to the μM range. • A paper strips-based test kit has been fabricated to detect F − ions selectively by the naked eye. • A smartphone-based assay analysis is also successfully performed to identify F − ions. • We have designed molecular logic circuits and set-reset memorized molecular devices. A salen-based colorimetric chemosensor (MM) has been designed and synthesized to selectively recognize F − and alkaline earth metal ions in solution and solid phase, respectively. A ratiometric UV–visible absorption spectral change with a colorimetric visualization from yellow to pink is observed in the presence of F − ions. The detection of F − ions is fully reversible in alkaline earth metal ions. The limit of detection (LOD) of F − ions by our as-prepared MM could be possible down to the μM range. A paper strips-based test kit has been fabricated to detect F − ions selectively by the naked eye. A smartphone-based assay analysis is also successfully performed to identify F − ions in the non-aqueous media. Such a dual ions sensing system with excellent reversibility and repeatability prompted us to consider probe MM a viable choice for fabricating molecular logic circuits and set-reset memorized molecular devices. A salen-based colorimetric chemosensor (MM) has been introduced to selectively recognize F − and alkaline earth metal ions in solution and solid phase, respectively. [Display omitted] [ABSTRACT FROM AUTHOR]

The investigation of dihydrazone Schiff base ligands as potential and appropriate chemosensors for fast, simple and portable detection of Cd(II) ion is reported. [Display omitted] • Dihydrazone Schiff bases – chemosensors for Cd(II) ion. • Photoluminescence on/off effect upon coordination of Schiff bases with Cd(II). • Fluorescence of ligands is enhanced when Cd(II) is added to test paper strips. Finding suitable probes for the rapid and sensitive detection of highly toxic pollutants is an urgent challenge for our environment. In this paper, three Schiff base ligands (H 2 L1 = 2 , 6-diacetylpyridine bis(isonicotinoylhydrazone), H 2 L2 = 2 , 6-diacetylpyridine bis(nicotinoylhydrazone) and H 2 L3 = 2 , 6-diacetylpyridine bis(picolinoylhydrazone)) have been used as potential chemosensors for Cd2+ detection. The corresponding Cd(II) complexes were prepared and it was found that the chemosensors coordinate similarly to the Cd2+ ion, eventually exhibiting different photoluminescent responses. Coordination of H 2 L1 and H 2 L2 to the Cd(II) ion results in a "turn-off" photoluminescence, while coordination of H 2 L3 show an excellent example of a "turn-on" mode of photoluminescence. Moreover, all three studied ligands are appropriate candidates for a fast, simple and portable method of Cd(II) ion detection. [ABSTRACT FROM AUTHOR]

Abstract: Here, we describe the construction of pH sensitive surfaces via the synthesis and controlled photografting of pH sensitive, fluorescent tethers from the surface of a reactive polymeric substrate. The living radical photografting technique presented makes use of dithiocarbamate-functionalized polymer to graft synthetic poly(ethylene glycol) acrylate succinyl fluorescein. Fluorescence intensity of grafted chains is analyzed as a function of photografting reaction time, graft length, buffer solution pH, and cycling sensors from acidic to basic conditions for optical switching. The graft fluorescence response occurs rapidly in a basic environment and grafted functionalities do not cleave or dramatically deplete (up to 72h later) upon initial exposure to high or low pH buffers. This behavior is a result of the increased stability when introducing the PEG spacer into the structure of the fluorescein. Ultimately, the pH sensitive grafts developed here demonstrate rapid response times, are easy to produce, and are readily integrated onto a fully polymeric microfluidic device using photolithographic techniques and spatially controlled living radical photografting chemistry. Once integrated, sensors such as these could be useful in monitoring pH changes when mixing, reacting, or introducing new chemicals onto a microdevice like the one presented. [Copyright &y& Elsevier]

Abstract A new colorimetric styryl-benzimidazole based receptor to recognize more than one analyte trans -2-[4′−(dimethylamino)styryl]benzimidazole) (L1) has been synthesized and fully characterized by 13C and 1H NMR, elemental analysis, UV–vis spectroscopy, and HRMS. Investigation of sensing ability of receptor L1 was carried out in presence of multiple anions (Br−, CN−, Cl−, ClO 4 −, F−, HSO 4 −, PF 6 −, NO 3 −, S2−, OH−, AcO− and H 2 PO 4 −) and cations (Cu2+, Cr3+, Al3+, Mg2+, Cd2+, Ni2+, Fe3+, K+, Fe2+, Mn2+, Ag+, Hg2+, Ca2+, Co2+, Pb2+, Na+, and Zn2+) by using UV–vis spectroscopy. Receptor L1 showed colorimetric response towards only for HSO 4 − ion. Receptor L1 -HSO 4 − interaction confirmed with the help of 1H NMR titration. Among various cations, L1 selectively sense the Cu2+ and Al3+ with the drastic colour change from yellow to green and dark yellow respectively. The stoichiometric binding ratio of L1 with HSO 4 −, Cu2+, and Al3+ found to be 1:1 by jobs method and HRMS data proved the complex formation between L1 and Cu2+/Al3+ with very low detection limit. In addition to explore practical applicability of L1 , paper strips have been made and used to detect HSO 4 − and Cu2+ ions, respectively, up to 10 ppm level. Graphical Abstract Unlabelled Image Highlights • A new colorimetric styryl-benzimidazole based receptor L1 has been synthesized to recognize more than one analyte. • Receptor L1 showed colorimetric response towards only for HSO 4 − ion in presence of multiple anions. • Among various cations, L1 selectively sense the Cu2+ and Al3+ with the drastic colour change. • To explore practical applicability of L1 , paper strips have been made and used to detect HSO 4 − and Cu2+ ions, respectively, up to 10 ppm level. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • A novel azo-based sensor (M1) for detection of CNˉ and Cu2+ ions is developed. • Cyanide is detected with a concentration of nanomolar (nM) level by naked eyes. • For quantitative measurements, M1 loaded paper test stripes were prepared. • Sensor M1 is applied as a colorimetric sensor for detection of CNˉ in real samples. Abstract Two novel and simple azo-based compounds with electron-withdrawing and electron-donating groups (M1 and M2) were synthesized by the diazotization procedure. The synthesized compounds were then applied for detection of important ions in aqueous solutions of acetonitrile. Sensor M1 with electron-withdrawing group (EWG) showed distinct colorimetric responses towards CNˉ (light yellow to red) and Cu2+ (light yellow to dark yellow). Through titration experiment, the detection limit (LOD) of M1 for CNˉ and Cu2+ ions sensing were found to be nano molar (nM) level. Job's plot based on spectroscopic data showed the complexes formation between M1 and ions has the stoichiometric ratio of 1:1 (M1-CNˉ and M1-Cu2+). In addition, the binding constants for M1 towards CNˉ and Cu2+ were determined using the Benesi-Hildebrand equation. Furthermore, the M1-based test papers strips were successfully used to the rapid detection of CNˉ ions in semi‐aqueous medium. Importantly, sensor M1 was applied to detect CNˉ and Cu2+ in real water samples and apple seeds samples. However, for M2, containing electron-donating group (EDG), no clear color changes were observed in the presence of investigated ions. [ABSTRACT FROM AUTHOR]

Optical chemosensor L comprising of a new mono-N-substituted derivative of dibenzodiaza-crown ether macrocyclic ligand bearing a 2-benzimidazole (2Bim) side arm was synthesized, and characterized by FT-IR, elemental microanalyses, 1H NMR, and 13C NMR, UV-visible, fluorescence (FL) spectroscopy. The colorimetric chemosensing behavior of L toward the library metal ions was examined, wherein L represented a prompt and selective yellow-to-purple color change for Fe(III) cation in a 25µM solution with LOD as 0.23 µM in ethanol:water (9:1, v/v), even in the presence of the other library metal ions (LMI). Based on the 1H NMR, UV-visible, and FL observations the coordination sphere of Fe(III) was shared with two 2-benzoimidazole (2Bim) side arms which were also confirmed by the elemental microanalyses (in the solid state) and the Job plot method (in the solution) of the complex. Moreover, the above-mentioned color change was attributed to the presence of a strong charge transfer (LMCT) band for the Fe(III)/L interaction in the solution. Furthermore, the viscosity measurement in the presence of Fe(III) uncovered an increase at 0.5–1.0 ratios for Fe(III)/L, attributable to the formation of a self-assembly in the solution. A TLC paper strip was impregnated by L for selective detection of Fe(III), demonstrating a live color change for Fe(III) at 0–5 mM in the presence of LMI. [ABSTRACT FROM AUTHOR]

• A quinazolinone-isophorone derived colorimetric sensor IAH was developed for the rapid detection of Cu2+ion. • Probe IAH can specially recognize Cu2+ ion over other metal ions. • The limit of detection for Cu2+ ion was found to be 141 nM. • The formation of IAH+Cu2+ complex was proved by 1H NMR titration, job's plot and DFT calculation. • IAH system can also be applied in low-cost test paper strips application for detection of Cu2+ ion. This paper presents the design and synthesis of a new colorimetric chemosensor based on quinazolinone-isophorone (IAH) to colorimetrically detect Cu2+ ions with high selectivity in the aqueous acetonitrile solution.In the presence of Cu2+, the synthesized compound had a remarkable colorimetric response from yellow to colorless, which could be seen with naked eyes. The analytical performance features of the proposed Cu2+ sensor are studied. The chemosensor can be applied to the quantification of Cu2+with a significant detection limit of 141 nM. The experiment results show that the colorimetric response of IAH towards Cu2+is pH-independent under a wide range of pH from 3.0 to 10.0. Moreover, the colorimetric response of IAH +Cu2+ can be reversed with EDTA multiple times. The mechanism of interaction between the IAH and Cu2+ions has been studied by Job's plot, HRMS, and 1HNMR titration experiments, which confirmed 1:1 binding stoichiometry between IAH and Cu2+. The real-time application of Cu2+ detection was demonstrated in test paper-based detection, constructing the molecular logic gate and quantifying Cu2+in water samples. [ABSTRACT FROM AUTHOR]

This paper reports a colorimetric and ratiometric chemosensor for hydrogen sulfide based on the 1-(2-pyridylazo)-2-naphthol and zinc ions ensemble. The detection strategy was designed based on the hydrogen sulfide-induced dissolution of the ensemble to form more stable zinc sulfide species. Using this strategy, hydrogen sulfide can remove zinc ions from the ensemble and restore the optical signals of the indicator, 1-(2-pyridylazo)-2-naphthol. Upon addition of hydrogen sulfide to the ensemble of 1-(2-pyridylazo)-2-naphthol and zinc ions, the absorption spectra displayed decreasing absorption intensity at 511 and 541 nm and increasing absorption intensity at 398 nm; moreover, the solution exhibited an obvious color change from pink to yellow that could be observed by the naked eye. This ensemble system could detect hydrogen sulfide with a limit of detection of 1.9 µM, and other common anions did not induce distinct changes in either absorption spectra or solution colors. [ABSTRACT FROM AUTHOR]

The dimeric azulene boronate ester 1 was designed and synthesized as a potential chemosensor for fluoride ion. UV–Vis titration analysis shows that with the enhancement of fluoride equivalents, the absorption peaks have been decreasing at 408 and 434 nm, while the peak at 370 nm has been increasing remarkably. Job's plot proves that the formation of a 1:2 [ 1 ·2F] 2− species is responsible for the observed absorbance enhancement in THF solution. Furthermore, this probe displays a quick response for fluoride ion and the color is from light green to yellow in solution, exhibiting a high selectivity and excellent stability. It is noted that a test paper for effective detection of fluoride has been prepared by using dimeric azulene boronate ester as a colorimetric chemosensor without any spectroscopic instrumentation. In addition, TD–DFT calculation has also been carried out in aqueous media for comparison. [ABSTRACT FROM AUTHOR]

[Display omitted] • Hydrogen-bonding receptors at the meso -position of the BODIPYs. • Detection of F- ions in polar aprotic organic solvents with a ppm detection limit. • Abstraction of acidic protons followed by deprotonation results in PET. • Molecular-level insight of photophysical response by spectral and DFT/TDDFT studies. • Use of B1 in molecular logic gate; B2 based test paper strip for F- ions detection. We report the facile synthesis of three meso -substituted BODIPYs which can act as fluorimetric chemosensors for detecting fluoride ions in polar aprotic organic solvents with a micromolar detection limit. The substituents at the meso -positions of synthesized BODIPYs are acetamidophenyl (B1), trihydroxyphenyl (B2), and hydroxyquinoline (B3) which show strong absorption (490–510 nm) and emission (515–550 nm) in the visible region. The spectral and quantum mechanical studies indicate that the fluoride ions can interact with the acidic proton of the BODIPYs viz., N H in B1 and O H in B2 and B3 respectively, and results in 1:1 BODIPY-fluoride [BODIPY----H F] adduct. The acidic protons of these BODIPYs are abstracted by fluoride ions resulting in non-fluorescent deprotonated species (turn-OFF state). The time-dependent density functional theory (TDDFT) calculations indicate that the deprotonated adduct is responsible for the fluorescence turn-OFF via the photoinduced electron transfer (PET) mechanism. These non-fluorescent deprotonated adducts can return to the fluorescent BODIPY state by abstracting H+ ions from any protic solvents. Hence, these molecules can act as ON-OFF-ON reversible sensors. The deprotonated adducts show significantly different UV–visible responses for B1 , B2 and B3. The binding constant of fluoride ions with BODIPYs (K b) is calculated to be in the range of 105 –106 M−1 with a limit of detection (LOD) in the range of 0.73–9 ppm. The ON-OFF-ON sensing behaviour of B1 is utilized to construct NOR molecular logic gate based on the two inputs of F- and OH– ions, and the emission intensity at 520 nm as the output. Among these BODIPYs, B2 has the lowest LOD for fluoride ions and shows distinct color change upon deprotonation in the visible region. This property has been utilized to develop portable test-paper strips for the qualitative colorimetric detection of fluoride ions. [ABSTRACT FROM AUTHOR]

A new oligothiophene derivative (3TY) was synthesized, and used as a highly selective hydrazine (N 2 H 4) chemosensor in ∼100% aqueous solution with "naked-eye" colorimetric and "turn-on" fluorimetric response. This chemosensor 3TY enabled ultrafast and ultrasensitive detection of hydrazine with ultralow detection limit of 1.45 nM (0.04 ppb) in a wide sensing pH range from 6 to 10. The sensing mechanism of 3TY toward hydrazine was strongly and fully confirmed. More importantly, colorimetric paper test strip and solid support silica are easily prepared by 3TY for on-site and real-time detection of hydrazine. Furthermore, 3TY displays many potential applications for detecting N 2 H 4 in environmental water and human urine along with bio-imaging in living HeLa cells. Image 1 • A new hydrazine-selective sensor 3TY based on oligothiophene derivative is developed. • 3TY displays distinct spectral and color change to N 2 H 4 in 100% aqueous solution. • The N 2 H 4 detection shows ultrafast response, ultraselectivity and ultrasensitivity. • 3TY -based test strips can colorimetrically and portably detect hydrazine in water. • Sensor 3TY provides an effective tool for imaging hydrazine in living cells. [ABSTRACT FROM AUTHOR]

In this paper, a novel chemosensor (named L1) for Fe3+ based on the rhodamine 6G and o-vanillin has been synthesized, which can selectively recognize Fe3+. The L1 solution showed a distinguishable colour change by naked eye, and the fluorescence turns on response after the addition of Fe3+. In addition, the experimental results showed that the spirocyclic of L1 was opened by cooperation between L1 and Fe3+, and then the fluorescence emission after excitation of the mixture solution was detected with the change in solution colour. The complexation coefficient of L1 towards Fe3+ was 1:1. Furthermore, L1 for Fe3+ sensing had a remarkable low detection limit of 427 nM (UV) and 130 nM (fluorescence), which is far below the drinking water standards (0.3 mg/L) of China. Meanwhile, the in vivo imaging and cell viability assay experiments demonstrated that L1 could be used for sensing Fe3+ in vivo. [ABSTRACT FROM AUTHOR]

[Display omitted] • Previously used aluminum sensor L has been further explored in sensing of Eu3+ ions. • The binding insights among L and Eu3+ have been explored by UV–visible, fluorescence spectroscopic and colorimetrically. • Association affinity, limits of detection, quantification, and linear ranges were determined. • The reversibility or re-usability of L checked via colorimetric observations using sodium salt of EDTA. Herein, the metal sensing properties of a previously reported aluminium sensor (E)-N'-((2-hydroxynapthalene-1-yl)thiophene-2-Carbohydrazide) (L) have been further explored in selective sensing of lanthanide ions. Among many tested lanthanide ions sensor L showed the selective colorimetric response for only Eu3+ ions. The presence of Eu3+ ions caused electronic transitions in the visible region with a color change from colorless to yellow in aqueous acetonitrile media. A red-shift in the absorption band and enhancement in emission intensity is investigated only for the addition of Eu3+ ions to L , without any interference of other existing ions. This chemosensor binds the Eu3+ ions in 1:1 stoichiometric ratio and works upto a detection limits, 2.179 × 10-8 M (LOD for Eu3+ at 415 nm from UV–Visible), 3.443 × 10-8 M (LOD for Eu3+ at 477 nm from fluorescence) with a binding constant of 8.691 × 103 M−1 for the L-Eu3+ binding. However, the developed sensor is used as a paper, cotton-based test kit assay and solid state colorimetric sensing of Eu3+ ions. The reversibility of sensor L is checked by colorimetric observation with the addition of sodium salt ethylenediaminetetraacetic acid (EDTA) and found it reversible up to three cycles. [ABSTRACT FROM AUTHOR]

In this article, we reported a new poly(diacetylenes)-based sensor (PDA-IBA) for silver ion detection and reduction through the chelation of imidazole moiety. The poly(diacetylenes) polymer functionalized with imidazole groups. As the concentration of silver ions in the solution increased, the PDA surface underwent oxidation concurrently with the reduction of silver ions was demonstrated through imidazole receptor. This chemical reaction resulted in a noticeable change in the color of the solution, shifting from blue to dark red. The limit of detection (LOD) was determined to be 0.034 mM. Zeta potential data analysis and electrochemical measurements further confirmed the PDA-IBA was capable to reduce Ag+ into Ag0. Moreover, the silver species produced were validated through inductively coupled plasma optical emission spectrometry (ICP-OES). Additionally, the color change observed in PDA-IBA as a response to silver ions was effectively demonstrated by integrating it into a paper-based sensor. This study introduces an innovative and promising approach for enhancing the capabilities of chemosensors in detecting and reducing Ag+. [Display omitted] • A highly sensitive and selective Ag + sensor, poly(diacetylenes)-based chemosensor PDA-IBA was synthesized. • The PDA-IBA polymer displayed a color change in the presence of Ag + through a chemical reduction process. • The silver ion's reduction was demonstrated by zeta potential data analysis and ICP-OES. [ABSTRACT FROM AUTHOR]

A very new and alternate function of an antibiotic drug levofloxacin (Lv), as a highly selective, colorimetric turn-OFF/turn-ON chemosensor for metal-ions Hg 2+ and Fe 3+ , has been reported in this study. An extremely easy, very less time consuming, economical one-pot method of synthesis has been developed for the production of silver nanoparticles (AgNPs). The AgNPs that are stabilized and surface functionalized by Lv. Functionalization of AgNPs by antibiotic drug Lv has been thoroughly confirmed using FTIR spectrophotometry. Two carbonyl oxygen moieties, one belongs to the pyridine oxygen group and another one from the carboxylate oxygen group of Lv together form the binding site over the nanoparticle surface. The Lv-AgNPs system has shown naked eye detectable colour change, as well as significant change via both UV–Vis and fluorescence spectroscopy. The limits of detection (LODs) are predicted to be 6.86 × 10 −8 M for Hg 2+ and 2.52 × 10 −9 M for Fe 3+ using UV–Vis spectroscopy and 2.35 × 10 −9 M for Fe 3+ using fluorescence spectroscopy. UV–Vis spectroscopy, fluorescence spectroscopy, FTIR, TEM, DLS etc. have been used for the physico-chemical characterization of Lv-AgNPs system and the nanoparticle mediated sensing process. Detailed experimental and theoretical studies employing FTIR spectrophotometry and density functional theory (DFT) studies have been used for the elucidation of drug-nanoparticle based sensing mechanism. It is also demonstrated that the Lv-AgNPs system can show real time application using Test-Paper Kit to establish the drug-nanoparticle assembly as a potential colorimetric turn-OFF/turn-ON sensing system for Hg 2+ and Fe 3+ respectively. [ABSTRACT FROM AUTHOR]

[Display omitted] • A probe is designed with naphthol and benzothiadiazole at both ends linked by a hydrazone. • Theoretical study suggests a key role of Fe3+ in affecting the electron localization. • Sensing mechanism is proved to be a combination of two processes. • The probe exhibits an excellent sensitivity and a short response time. • Discriminative turn-off emission is observed in paper strips and bioimages. Naphthol hydrazone derivatives are recognized as efficient chelating agents for both qualitative and quantitative detection of metal ions. Here we design a naphthol hydrazine-based chemosensor with covalently linking a strong electron-withdrawing benzothiadiazole group to modulate the molecular electronic structure, nominated as NtHzBtd. The fluorescent probe performs excellent selectivity and sensitivity towards Fe3+ with 1:1 binding stoichiometry, while exhibiting a quick response at 55 s with a relatively low limit of detection of 0.036 µM. A series of spectroscopic measurements in tandem with theoretical calculations suggest that the probe undergoes both intramolecular charge transfer (ICT) and chelation enhanced quenching (CHEQ) processes. Successful color rendering of paper strips and bioimaging in PC3 cells demonstrate the promising applicability of NtHzBtd for portable Fe3+ detection in real samples and biosystems. [ABSTRACT FROM AUTHOR]

A new photochromic diarylethene with a benzoisothiazole unit has been designed and synthesized. The diarylethene could act as a colorimetric and fluorescence dual-channel chemosensor for CO 3 2− with short response time, high selectivity, and excellent sensitivity. Moreover, the response mechanism of the chemosensor to CO 3 2− was studied systematically in methanol. The chemosensor could be used to the detection of CO 3 2− in practical water samples, and also be made into test papers for CO 3 2− recognition with high efficiency. A dual-channel chemosensor has been designed and synthesized for detecting CO 3 2− with excellent selectivity and sensitivity. The chemosensor could be used to detect CO 3 2− in practical water samples, and be made into test strips for CO 3 2− recognition with high efficiency. [Display omitted] • A new diarylethene derivative with a benzoisothiazole unit has been designed and synthesized. • The derivative could act as a dual-channel chemosensor for CO 3 2− detection with excellent selectivity and sensitivity. • The chemosensor could be made into test strips for CO 3 2− recognition with high efficiency. [ABSTRACT FROM AUTHOR]

• A novel, di-Schiff base receptor, AQ , for the detection of Hg2+ ions through naked eye in buffered semi-aqueous medium (CH 3 OH: H 2 O 7: 3) at pH = 7. • AQ detects Hg2+ ions in natural water samples, filter paper strips and solid silica gel (60–120 mesh) pre-coated with it. • The limit of detection of AQ towards Hg2+ions is found to be 220 nM with an association constant of 1.49 × 104 M −1. • The job's plot experiment indicated the formation of 1: 1 stoichiometric complex between AQ and Hg2+ ions. A novel di-Schiff base colorimetric sensor, 2-((E)-(((E)-anthracen-9-ylmethylene)hydrazineylidene)methyl)quinolin-8-ol (coded as AQ) , connecting anthracene and 8-hydroxyquinaldehyde functionalities is developed for the naked eye detection of Hg2+ ions in HEPES buffered CH 3 OH: H 2 O (7: 3) solvent system within neutral pH range. The sensor witnessed high selectivity towards Hg2+ ions in the presence of various other metal ions with naked eye colour change from yellow to pink. The quantitative detection limit of 220 nM was achieved through UV–Vis spectroscopy. The change in the intramolecular charge transfer behaviour of AQ has been proposed to be responsible for the observed absorption as well as colour change as evident from 1H NMR titration, FT-IR studies and DFT calculations. Moreover, the probe AQ has been efficiently applied for the solid state naked eye detection of Hg2+ ions in the form of filter paper strips and solid silica gel (60–120 mesh), pre-impregnated with AQ , and for the detection of Hg2+ ions in real water samples. [ABSTRACT FROM AUTHOR]

Abstract A new antipyrine Schiff's base, 2-((2,5-dimethyl-3-oxo-1-phenyl-2,3-dihydro-1H-pyrazol-4-yl)imino)-1H-indene-1,3(2H)-dione (L) has been synthesized by simple condensation of ninhydrin with 4-aminoantipyrine. The sensing ability of L was studied with selected metal ions from s-block and d-block elements by visual and UV–Vis spectrometry in water: methanol (8:2, v/v) media. The naked-eye detectable colour change of L was occurred from pink to colourless upon interacting with Cr3+ while other metal ions did not change the colour of L. The two main absorption bands appeared at 425 nm and 540 nm of L were quenched upon interaction with Cr3+ while other tested metal ions failed to perturb the absorption bands of L. The Jobs plot and UV–visible spectral studies indicate the formation of a 2:1 complex between the L and Cr3+ with an association constant of 3.0 × 104 M−1. The limit of detection (LOD) of L for the analysis of Cr3+ found to be 5.4 × 10−7 M. The Cr L 2 complex formation in solution is reversed after treatment with ethylenediaminetetracetic acid (EDTA). The colorimetric sensing ability of Schiff's base L was successfully utilized in the preparation of test paper strips and solid supported silica for the real samples analysis to detect Cr3+ ions from 100% aqueous environment. Graphical abstract Unlabelled Image Highlights • The sensor showed fast absorbance response, excellent selectivity, and high sensitivity towards Cr3+. • L can be used for the analysis of Cr3+ in water sample. • The receptor L can be recyclable after treatment with a EDTA. [ABSTRACT FROM AUTHOR]

[Display omitted] • Highly selective and noncyclic Schiff base L has been used for the recognition of Bi3+. • The LOD as low as 6.39 nM. • The test paper strips has been used to monitor the Bi3+ ions and it applied for the intracellular imaging of Bi3+ ions in the HOS cell line. A new dual fluorescent-colorimetric probe (E)-4-methyl-N'-((2,3,6,7-tetrahydro-1H,5H-pyrido[3,2,1- ij ]quinolin-9-yl)methylene)benzenesulfonohydrazide (L) was synthesized by condensation reaction of julolidine carboxaldehyde and p-toluene sulfonyl hydrazide to get the probe (L) for recognition of bismuth ions (Bi3+). The structural conformation of L was confirmed through 1H NMR, IR, and mass spectral analysis. The probe L showed visual color change and turn-on emission upon interaction with Bi3+ in H 2 O:CH 3 CN (7:3, v/v) media over other divalent and trivalent metal ions. The probe displays selective 'turn-on' emission for Bi3+ via chelation enhanced fluorescence (CHEF) and > C N isomerization mechanism. The experimental analysis of Job's plot showed a 2:1 stoichiometric ratio of L-Bi3+ complex formation and this was further verified with theoretical studies. The detection limit by spectrophotometric and spectrofluorometric were found to be 170 nM and 6.39 nM, respectively. The binding mechanism was verified by 1H NMR, ESI-mass, and theoretical studies. Furthermore, the selective colour change of L with Bi3+ was integrated with a smartphone to monitor the change in the RGB tool and test paper kit. The turn-on response of the probe with Bi3+ was used to capture by the fluorescence imaging technique in live Human Bone Osteosarcoma cell line (HOS) cells. Overall, probe L demonstrates a promising potential for the detection of Bi3+ ions in the protic environment and this is the first report of a fluorescent probe used in HOS cell live imaging. [ABSTRACT FROM AUTHOR]

[Display omitted] • A naphthyl hydrazine-pyridine Schiff base chemosensor for Al3+ is prepared. • Density functional theory calculations are performed for both probe and complex. • Turn-off response arises from an intramolecular charge transfer process. • The probe exhibits a low detection limit, quick response and high selectivity to Al3+. • Tests in HeLa cells confirm low cytotoxicity and bioapplications of the probe. A pyridine modified naphthol hydrazone Schiff base chemosensor, NaPy , was prepared in a two-step process to detect aluminum ion (Al3+) in different samples. The probe shows a turn-off emission response towards Al3+ at a 1:1 binding stoichiometry via intramolecular charge transfer (ICT) mechanism, as validated by density functional theory (DFT) calculations and a series of spectroscopic measurements. The response time is slightly over one minute with a limit of detection (LOD) value of 0.164 µM, demonstrating the great sensitivity of the probe. It is also found that NaPy exhibits high selectivity towards Al3+ and resists interference from seventeen other cations. Application investigations in paper strips, water samples and HeLa cells suggest that NaPy can be used as an efficient probe for sensing Al3+ in real environmental samples and biosystems. [ABSTRACT FROM AUTHOR]