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The concept of a lab-on-a-molecule, which was proposed just short of two decades ago, has captured the imagination of scientists. From originally being proposed as an AND logic gate driven by three chemical inputs as a direct way of detecting congregations of chemical species, the definition of what constitutes a lab-on-a-molecule has broadened over the years. In this review, molecules that can detect multiple analytes by fluorescence, among other techniques, are reviewed and discussed, in the context of molecular logic and multi-analyte sensing. The review highlights challenges and suggestions for moving the frontiers of research in this field to the next dimension. [ABSTRACT FROM AUTHOR]

In this case, various factors of course ideological and political elements are integrated into a comprehensive chemistry experiment in the construction of a visual molecular logic system with the preparation, characterization and application of intelligent hydrogel film electrodes. Through interdisciplinary research, it bridges the gap between basic teaching and cutting-edge technologies, guiding students to pay attention to issues such as national emerging material development, sustainable development, and digital information encryption. The design of this case helps cultivate students’ sense of responsibility in serving national strategies and socio-economic development, as well as the determination to innovate and climb the peaks of science. [ABSTRACT FROM AUTHOR]

The concept of a lab-on-a-molecule, which was proposed just short of two decades ago, has captured the imagination of scientists. From originally being proposed as an AND logic gate driven by three chemical inputs as a direct way of detecting congregations of chemical species, the definition of what constitutes a lab-on-a-molecule has broadened over the years. In this review, molecules that can detect multiple analytes by fluorescence, among other techniques, are reviewed and discussed, in the context of molecular logic and multi-analyte sensing. The review highlights challenges and suggestions for moving the frontiers of research in this field to the next dimension.

Describing a gated photochromic derivative (DTEC) based on diarylethene, which is inert to light in solution. In other words, compound DTEC does not undergo an effective photochromic transformation in response to any wavelength of light, and the solution is always colorless. However, after addition of Ag+ ions, the photochromic reaction of DTEC is activated and the solution changes from colorless to yellow upon irradiation with UV light, suggesting that DTEC changes to ring-closed isome r. Therefore, the photochromic reactivity of DTEC can be restored by adding Ag+ ions, indicating that the photochromic properties of DTEC can be gated by Ag+ ions. Furthermore, a molecular logic circuit can be successfully fabricated with three inputs (Ag+ ions, UV and DTEC) and one output (absorbance at 410 nm), which shows great potential for the development of multi-stimulus-responsive photoswitches. [ABSTRACT FROM AUTHOR]

[Display omitted] • SEM-EDX analysis confirmed the presence of GSR components in the sample, lacking concentration details. • FRET analysis involving Acf and RhB dyes provided insight into individual component concentrations, particularly effective at higher Sb+3 concentrations (around 500 µg/L to 550 µg/L). • The designed Molecular Logic Gate enabled FRET efficiency to discern Pb+2 and Ba+2 concentrations even at lower Sb+3 levels. • FRET's ratio metric sensor advantage ensures robustness against external factors like excitation source fluctuations, solvent conditions, etc. making it ideal for quantitatively detecting GSR components. The present work represents a Fluorescence Resonance Energy Transfer (FRET) based sensing method for detecting Gunshot Residue (GSR) components. Two laser dyes Acf and RhB have been used as donor and acceptor respectively in the FRET pair. The real sample was collected after test firing in a forensic science laboratory. On the other hand, a standard GSR solution has been prepared in the laboratory. For the preparation of standard GSR solutions, we used the water solutions of the salts BaCl 2 , SbCl 3, and Pb(NO 3) 2. The FRET efficiency was measured between Acf and RhB to sense the presence of GSR components (Pb+2, Ba+2, and Sb+3) in both real sample and standard solution by mixing the salts in aqueous solution. It has been observed that the FRET efficiency systematically decreases in the presence of GSR components. To amplify the FRET efficiency of the dye pair, inorganic clay dispersion (laponite) was used. The enhancement in FRET efficiency represents a better sensitivity of the proposed sensor. The current sensor is useful for the quantification of concentrations of the GSR components in a real sample. [ABSTRACT FROM AUTHOR]

• The ferrocene-pyridylpyrazole combo enables efficient multi-channel sensing. • Receptor R 's DFT parameters closely match its XRD structure; interactions elucidated via NMR and DFT. • R displays color changes upon Hg²⁺ (yellow to orange) and Cu²⁺ (yellow to green) addition. • Hg²⁺ binding alters R's E 1/₂ and shows significant shifts in cyclic and pulse voltammetry. • R 's fluorescence responds to Cu²⁺ (turn-on) and Hg²⁺ (turn-off) selectively, enabling combinatorial logic. A cation sensor, R , with multi-channel signaling was developed by creating a covalent connection between a ferrocene unit and pyridyl-pyrazole rings. Spectroscopic techniques and single-crystal X-ray diffraction were employed to characterize sensor R. The examination revealed a dihedral angle of 140.09° for the pyridyl-pyrazole rings. The receptor R functions as a highly selective multi-channel chemosensor, exhibiting chromogenic, fluorogenic, and electrochemical capabilities. In a CH 3 CN/water (9:1) solvent mixture, receptor R operates as a multi-channel signaling chemosensor, selectively detecting Hg2+ and Cu2+ ions in water. The original pale-yellow solution turned orange upon Hg2+ addition and green upon Cu2+ addition. A new low energy (LE) band at 460 nm was detected after adding one equivalent of Hg2+. In cyclic voltammetry (CV), the half-wave potential (E 1/2) of 462 mV shifted to 622 mV, whereas in differential pulse voltammogram (DPV), the oxidation peak underwent an anodic shift (ΔE 1/2 = 155 mV). The maximum emission at 423 nm was lowered by more than 90 % when the concentration of Hg2+ ions reached one equivalent. One equivalent addition of Cu2+ results in a new LE band at 740 nm. Cu2+ ions suppress the oxidation peak current in both the CV and DPV of R. It also demonstrates chelation-enhanced fluorescence effect (CHEF) with Cu2+. The interaction between cations and R was elucidated through 13C NMR titration. DFT calculations revealed the binding mode. Its distinctive fluorescence demonstrates a 'turn-on' response to Cu2+ and a 'turn-off' response to Hg2+ with selectivity. This concept has been applied to create a molecular combinatorial logic circuit. [Display omitted] [ABSTRACT FROM AUTHOR]

A novel coumarin-based fluorescent sensor CHE , incorporating 2-hydrazinylbenzothiazole and coumarin aldehyde, has been developed that demonstrated a preferential detection of Hg2+ and Ag+ in presence of interferences. Compared to previously prevalent intensity-based fluorescent probes, CHE exhibited a ratiometric fluorescence response to Hg2+ and Ag+, and further accurately differentiated Hg2+ and Ag + using the differential extractive ability of EDTA when interacting with ion- CHE complexes. Sensing mechanism was investigated and elucidated. The chemosensor CHE was successfully applied to detect Hg2+ and Ag+ in six distinct samples with satisfactory results. Additionally, combinatorial logic circuits were constructed utilizing three distinct logic gates (NOT, OR, and INH) based on the sensor's differential output signals in response to Hg2+/Ag+ and other cations. Interestingly, utilizing the reversible and reproducible switching behavior of the EDTA interaction with Hg2+, a conceptual 'Write–Read–Erase–Read' memory function with multi-write capability was proposed, offering a novel perspective for molecular-based memory systems. [Display omitted] • A novel probe CHE was designed by incorporating 2-hydrazinylbenzothiazole and coumarin aldehyde. • CHE exhibited a ratiometric fluorescence response to Hg2+ and Ag+, and further differentiated Hg2+ and Ag+. • The chemosensor CHE was successfully applied to detect Hg2+ and Ag+ in six distinct samples with satisfactory results. • A conceptual 'Write–Read–Erase–Read' memory function with multi-write capability was proposed based on monomolecular CHE. [ABSTRACT FROM AUTHOR]

• Schiff base ligand L is used for the precise spectroscopic detection of Cu2+ ions. • The 1:1 complexation of L with Cu2+ was validated by ESI-MS, and Job's plot. • L could detect Cu2+ as low as 0.46 μM. • L was employed to develop a molecular logic gate. In this study, we employed a Schiff base ligand (L = 6,6′-((1E,1′E)-(cyclohexane-1,2-diylbis(azanylylidene))bis(methanylylidene))bis(2,4-di- tert -butylphenol)) to serve as a chemosensor exclusively for detecting Cu2+ ions over other metal ions and anions in a THF:H 2 O mixture (7:3, v/v). L exhibits an absorption band at 330 nm, which undergoes a bathochromic shift to 377 nm upon interaction with solely Cu2+ ions, suggesting a restricted internal charge transfer process of L. Analysis via ESI-MS and Job's plot confirmed a 1:1 stoichiometric ratio between L and Cu2+. L demonstrated the capability to detect Cu2+ ions at a concentration as low as 0.46 μM. Furthermore, we investigated the effectiveness of L in developing molecular logic gates and its applications in analyzing Cu2+ in water samples. [ABSTRACT FROM AUTHOR]

[Display omitted] • Schiff base receptor L for Cu2+, Fe3+, and Zn2+ detection via chromogenic and fluorogenic channels. • The 1:1 complexation of L with three target ions was validated by ESI-MS, Job's plot, and 1H NMR titration. • Molecular logic gates, keypad locks, and portable test kits were developed using L. • L was employed to measure the trace amounts of Cu2+, and Fe3+ ions in water samples. A simple and adaptable salen-based Schiff base receptor (L = 6,6′-((1E,1′E)-(cyclohexane-1,2-diylbis(azanylylidene))bis(methanylylidene))bis(2-methoxyphenol))was employed in the current study for colorimetric detection of Cu2+, Fe3+, and fluorescence detection of Zn2+ ions in a semi-aqueous solution. L could identify the three target ions among the many different cations and anions in the solution. The turn-on fluorescence signal of L to Zn2+ ions was boosted by the restriction of the intramolecular charge transfer process, and the resulting chelation enhances the fluorescence signal. The sensing mechanisms were validated using a Job's plot, Electrospray Ionization Mass Spectrometry (ESI-MS) analysis, Nuclear Magnetic Resonance (NMR) titration experiment, and theoretical calculation investigations. The detection limits for Zn2+ were determined to be 0.038 μM, whereas Cu2+ and Fe3+ detection limits were 0.58 μM and 0.62 μM, respectively. Next, L was used to develop solid silica gel and test strips for instantaneous colorimetric and fluorescent detection of the three target ions in real time. The trace level of Cu2+ and Fe3+ in the tap and drinking water samples could be quantitatively measured using L. Eventually, applications for keypad locks and molecular logic gates were developed utilizing the receptor L. [ABSTRACT FROM AUTHOR]

[Display omitted] • The surface of ZnO nanoparticles has been adorned with a tripodal novel chemical probe. • A new innovative nano-platform detects Al3+ ions, with naked-eye observation. • Utilizing PET mechanism for fluorescence activation, creating an AND molecular logic gate with Al3+ and H+ ions. The FDA (Food and Drug Administration, (USA)) lists ZnO as a material that is widely acknowledged to be safe. ZnO NPs with a range of tiny particle sizes were made using the precipitation process. ZnO nanoparticles' surface is embellished with a tripodal sensor containing naphthol units. The assembly with the same receptor decorated on ZnO NPs is contrasted with the cation detection capabilities of the purified tripodal receptor. The UV–visible spectrophotometric analysis was conducted to study the state transitions of the receptor and the decorated ZnO receptor. A positive selectivity to Al3+ cations is determined by the fluorescence study under ideal circumstances. The particle size and surface morphologies are determined by DLS and SEM analysis for the same receptor − TP1 and embellished with a tripodal receptor TP2. Using a fluorescence switch-on Photoinduced Electron Transfer (PET) mechanism, the receptor coated on ZnO detects the presence of Al3+ ions with specificity. The binding constant value was determined using the B-H plot equation. Binding stoichiometry for [TP1-Al3+, TP2-Al3+] showed a 1:1 ratio. The fluorescence switches ON-OFF process of the ZnO surface adorned − TP2 with Tripodal receptor- TP1 was used to create molecular logic gates, which can function as a module for sensors and molecular switches. The addition of Na 2 EDTA in the solution of the [TP1; TP2 − Al3+] complex resulted in a noticeable reduction in the emission of fluorescence. This finding offers compelling support for the reversibility of the chemosensor. To enable the practical application of this sensor, we have developed a cassette containing receptors TP1 and TP2. Successfully, it can detect Al3+ metal ions. We performed a comprehensive assessment of the dependability and appropriateness of our approach in measuring the concentration of Al3+ ions in wastewater produced by important industrial procedures. [ABSTRACT FROM AUTHOR]

Polyacrylamide hydrogels formed by free radical polymerisation were formed by entrapping anthracene and 4-amino-1,8-naphthalimide fluorescent logic gates based on photoinduced electron transfer (PET) and/or internal charge transfer (ICT). The non-covalent immobilisation of the molecules in the hydrogels resulted in semi-solid YES, NOT, and AND logic gates. Two molecular AND gates, examples of Pourbaix sensors, were tested in acidic aqueous methanol with ammonium persulfate, a strong oxidant, and displayed greater fluorescence quantum yields than previously reported. The logic hydrogels were exposed to aqueous solutions with chemical inputs, and the fluorescence output response was viewed under 365 nm UV light. All of the molecular logic gates diffuse out of the hydrogels to some extent when placed in solution, particularly those with secondary basic amines. The study exemplifies an effort of taking molecular logic gates from homogeneous solutions into the realm of solid-solution environments. We demonstrate the use of Pourbaix sensors as pE-pH indicators for monitoring oxidative and acidic conditions, notably for excess ammonium persulfate, a reagent used in the polymerisation of SDS-polyacrylamide gels. [ABSTRACT FROM AUTHOR]

Covalent organic framework (COF) film with electrofluorochromic (EFC) and electrochromic (EC) properties has been synthesized by using triphenylamine-based monomers. The film exhibited a high maximum fluorescence contrast of 151 when subjected to a drive voltage of 0.75 V vs the Ag/AgCl electrode, causing the fluorescence to be quenched, which resulted in the EFC process's "fluorescence off" state. The switching times for the fluorescence on and off states were 0.51 and 7.79 s, respectively. Over the same voltage range, the COF film also displayed EC properties, achieving a contrast of 50.23% and a coloration efficiency of 297.4 cm 2 C -1 at 532 nm, with switching times of 18.6 s for coloration and 0.7 s for bleaching. Notably, the quenched fluorescence of the COF film could be restored by adding dopamine as a reductant. This phenomenon enabled the implementation of a NAND logic gate using the applied potential as a physical input and dopamine addition as a chemical input. This study demonstrates the successful development of COF films with bifunctional EFC and EC properties, showcasing their potential for use in constructing advanced optoelectronic devices.

An orange light emitting 'off–on-off' fluorogenic probe for consecutive detection of Al3+ ions and 2,4,6-trinitrophenol having detection and quantification limit in the nM range. [Display omitted] • A fluorogenic sensor (HNMN) has been introduced to detect Al3+ ions and picric acid (PA). • A paper strips-based test kit has been fabricated to detect Al3+ ions and PA. • The LOD and LOQ values are found to be 8.6 nM and 28.4 nM respectively in the DMF medium. • Demonstrate a facile approach to design highly red-shifting fluorosensors from the non-fluorophore moieties. • Could be avoided false signaling during the detection of target analytes. A simple, orange light emitting 'off–on-off' fluorogenic sensor, (E)-4-(((2-hydroxy-4-nitrophenyl) imino) methyl) naphthalene-3-ol (HNMN), has been introduced for the successive recognition of Al3+ ions and 2, 4, 6-trinitrophenol respectively, utilizing the photoluminescence 'off–on-off' mechanism. A significant enhancement in the photoluminescence of HNMN is found at 558 nm, attributed to the chelation of Al3+ ions, resulting in a visible orange-colored photoluminescence under a handy 365 nm UV light illumination. Among the different tested nitroaromatic compounds (NACs), 2, 4, 6-trinitrophenol, namely picric acid (PA), selectively quenches the orange photoluminescence caused by Al3+ on the HNMN complex. The stoichiometric ratio for the complex formation between HNMN and aluminum ion is determined to be 1:1, with an estimated limit of detection (LOD) and quantification (LOQ) found to be 8.6 nM and 28.4 nM respectively in DMF medium. Different spectroscopic analyses have elucidated the mechanistic features of identifying Al3+ ions. A test kit–based experiment is performed with the HNMN- coated filter paper to detect Al3+ ions and PA sequentially & selectively. Based on the chemical inputs and optical output, we have framed the INHIBIT molecular logic circuit. The present report evokes a facile approach for the design and molecular development of highly red-shifting fluorosensors from the non-fluorophore moieties to avoid false signaling during the detection of target analytes. [ABSTRACT FROM AUTHOR]

Abstract Background In this paper, a simple, enzyme-free, label-free fluorescence, high sensitivity logic gate hairpin aptasensor was developed for adenosine triphosphate (ATP) detection based on graphene oxide (GO) and PicoGreen dye. Methods Using single-strand deoxyribonucleic acid (DNA) and adenosine triphosphate (ATP) as input signal and fluorescence signal as output signal, if single-strand DNA (DNA-L), single-strand DNA (DNA-S), and ATP were present at the same time, one segment of DNA-L formed a hairpin ring with ATP, and the other segment of DNA-L formed a completely complementary hairpin stem with DNA-S. The hairpin DNA was detached from the GO surface, and PicoGreen dye was embedded into the hairpin stem, and the fluorescence signal was enhanced. The molecular logic gate was constructed through the establishment of logic histogram, logic circuit, truth table, and logic formula. The biosensor-related performances including sensitivity, selectivity, and linearity were investigated, respectively. Results We have successfully constructed a AND logic gate. The detection limit of ATP is 138.0 pmol/L (3σ/slope) with detection range of 50–500 nmol/L (R 2 = 0.98951), and its sensitivity is 4.748 × 106–6.875 × 108 a.u. (mol/L)−1. Conclusions The logic gate hairpin aptamer sensor has the advantages of high sensitivity, low detection limit, and low cost, and can be successfully applied to the detection of adenosine triphosphate (ATP) in actual human urine samples.

The available heavy metals in soil samples can cause the direct toxicity on ecosystems, plants, and human health. Traditional chemical extraction and recombinant bacterial methods for the available heavy metals assay often suffer from inaccuracy and poor specificity. In this work, we construct half adder and half subtractor molecular logic gates with molecular-level biocomputation capabilities for the intelligent sensing of the available lead (Pb) and cadmium (Cd). The available Pb and Cd can cleave DNAzyme sequences to release the trigger DNA, which can activate the hairpin probe assembly in the logic system. This multifunctional logic system can not only achieve the intelligent recognition of the available Pb and Cd according to the truth tables, but also can realize the simultaneous quantification with high sensitivity, with the detection limits of 2.8 pM and 25.6 pM, respectively. The logic biosensor is robust and has been applied to determination of the available Pb and Cd in soil samples with good accuracy and reliability. The relative error (Re) between the logic biosensor and the DTPA + ICP-MS method was from −8.1 % to 7.9 %. With the advantages of programmability, scalability, and multicomputing capacity, the molecular logic system can provide a simple, rapid, and smart method for intelligent monitoring of the available Pb and Cd in environmental samples. [Display omitted] • Intelligent sensing system was built for the available Pb and Cd monitoring. • Half adder and half subtractor logic gates were constructed employed DNAzymes as recognition probes. • The logic biosensor is ultrasensitive, with the detection limit to be 2.8 pM for Pb and 25.6 pM for Cd. • The sensing system is robust and can work in soil samples with good accuracy and reliability. • The operation is simple without complex extraction steps. [ABSTRACT FROM AUTHOR]

When photochromes function as a photonic molecular logic gate (MLG), the problem of uncertainty of the final state of the gate arises at the level of a single molecule, since photoisomerization of a photochrome is a probabilistic process. To solve this problem, we propose to use as MLGs self-organized multiphotochromic systems (MPSs) based on hybrid organic–inorganic nanoparticles (HNPs)—conjugates of colloidal quantum dots (QDs) and organic photochromes. A quantum dot in HNP is a platform for coordination of a photochromic ligand (PL) containing special anchor groups. The photochromic ligand has at least two spectrally distinguishable isomers. A multiphotochromic system containing n PL molecules is a "super-photochrome" with at least (n + 1) spectrally distinguishable isomers. We have shown for the first time that MPS based on CdS QD and anthrylquinolylethylene PL, switching by the mechanism of reversible trans–cis photoisomerization, is capable of functioning as fully photonic MLG, since the output signal is read from fluorescence of PL or QD. The homogeneity of input and output signals, which are quanta of light, opens up new opportunities for the design and creation of molecular photonic devices, including means for processing digital information at the molecular level. [ABSTRACT FROM AUTHOR]

In the present study, we have engineered a molecular logic gate system employing both Fe 2+ ions and cholesterol as bioanalytes for innovative detection strategies. We utilized a green-synthesis method employing the mango leaves extract to create fluorescent graphene quantum dots termed "mGQDs". Through techniques like HR-TEM, i.e., high-resolution transmission electron microscopy, Raman spectroscopy, and XPS, i.e., X-ray photoelectron spectroscopy, the successful formation of mGQDs was confirmed. The photoluminescence (PL) characteristics of mGQDs were investigated for potential applications in metal ion detection, specifically Fe 2+ traces in water, by using fluorescence techniques. Under 425 nm excitation, mGQDs exhibited emission bands at 495 and 677 nm in their PL spectrum. Fe 2+ -induced notable quenching of mGQDs' PL intensity decreased by 97% with 2.5 μM Fe 2+ ions; however, adding 20 mM cholesterol resulted in a 92% recovery. Detection limits were established through a linear Stern-Volmer (S-V) plot at room temperature, yielding values of 4.07 μM for Fe 2+ ions and 1.8 mM for cholesterol. Moreover, mGQDs demonstrated biocompatibility, aqueous solubility, and nontoxicity, facilitating the creation of a rapid nonenzymatic cholesterol detection method. Selectivity and detection studies underscored mGQDs' reliability in cholesterol level monitoring. Additionally, a molecular logic gate system employing Fe 2+ metal ions and cholesterol as a bioanalyte was established for detection purposes. Overall, this research introduces an ecofriendly approach to craft mGQDs and highlights their effectiveness in detecting metal ions and cholesterol, suggesting their potential as versatile nanomaterials for diverse analytical and biomedical applications.

Polyacrylamide hydrogels formed by free radical polymerisation were formed by entrapping anthracene and 4-amino-1,8-naphthalimide fluorescent logic gates based on photoinduced electron transfer (PET) and/or internal charge transfer (ICT). The non-covalent immobilisation of the molecules in the hydrogels resulted in semi-solid YES, NOT, and AND logic gates. Two molecular AND gates, examples of Pourbaix sensors, were tested in acidic aqueous methanol with ammonium persulfate, a strong oxidant, and displayed greater fluorescence quantum yields than previously reported. The logic hydrogels were exposed to aqueous solutions with chemical inputs, and the fluorescence output response was viewed under 365 nm UV light. All of the molecular logic gates diffuse out of the hydrogels to some extent when placed in solution, particularly those with secondary basic amines. The study exemplifies an effort of taking molecular logic gates from homogeneous solutions into the realm of solid-solution environments. We demonstrate the use of Pourbaix sensors as pE-pH indicators for monitoring oxidative and acidic conditions, notably for excess ammonium persulfate, a reagent used in the polymerisation of SDS-polyacrylamide gels.

[Display omitted] • We have successfully designed and synthesized a new biocompatible chromo- and fluorogenic probe L2 derived from rhodamine-6G which showed a selective and sensitive colorimetric as well as " turn-ON " fluorescence response towards Fe3+ ion over mono-, di- and other trivalent metal ions. • Complete aqua friendliness of this probe has drawn special attention over other rhodamine 6G based chemosensors. • A large enhancement of fluorescence intensity of L2 (14 fold) in the presence of Fe3+ in aqueous medium (HEPES buffer at pH 7.2) with the development of reddish yellow color clearly indicates that this probe L2 can be used for the detection of Fe3+ through naked eye. • The K f value was evaluated to be (1.16 ± 0.04) x 104 M−1 from the fluorescence titration data at systematic increasing concentration of metal ions and fixed 20 μM concentration of ligand. • The higher values of quantum yields (0.523) for [ L2 -Fe3+] over the free ligand (0.013) indicate the higher stability of the complexes in the excited states. • Job's plot confirms 1:1 stoichiometric ratio for the binding of Fe3+ with L2. • An excellent reversible fluorescence ' OFF-ON " property of L2 has been observed through fluorescence study with the sequential addition of Fe3+ and CN– ions at room temperature which suggests the reusability of this chemosensor. • The detection limit of L2 for Fe3+ was evaluated to be 4.184 μM and this makes the probe usable to quantify the Fe3+ in real water samples. • As the sensing phenomenon is reversible it helps to frame INHIBIT gate and memory devices. A novel rhodamine-6G based biocompatible chromo- and fluorogenic "OFF-ON" sensor L2 , having amide based metal ion receptor, has been synthesized using Michael addition reaction and characterized by IR, NMR and HRMS spectroscopic studies. It exhibits an excellent selectivity and sensitivity towards Fe3+ in aqueous medium over mono- and di-valent and other trivalent metal ions. A 14-fold enhancement of fluorescence intensity was found upon addition of 11.5 equivalent Fe3+ ion into the probe L2 in H 2 O (pH 7.2, 10 mM HEPES buffer) with colour change from colourless to reddish yellow, providing an opportunity for naked eye detection of Fe3+. The corresponding binding constant K f was evaluated to be (1.16 ± 0.04) x 104 M−1 with 1:1 stoichiometry. Quantum yields of L2 and [L2 - Fe3+] complex in H 2 O (pH 7.2, 10 mM HEPES buffer) were found to be 0.013 and 0.523, respectively using Rhodamine-6G as standard. LOD of L2 for Fe3+ detection in aqueous medium determined by 3σ/slope method was found to be 4.184 μM. Cyanide ion scavanges Fe3+ from [L2 - Fe3+] resulting quenching of fluorescence due to re-attainment of the non-fluorescent spirolactam ring form of the probe. As the sensing phenomenon is reversible, it helps to frame INHIBIT logic gate and memory devices. [ABSTRACT FROM AUTHOR]

Background: In this paper, a simple, enzyme-free, label-free fluorescence, high sensitivity logic gate hairpin aptasensor was developed for adenosine triphosphate (ATP) detection based on graphene oxide (GO) and PicoGreen dye. Methods: Using single-strand deoxyribonucleic acid (DNA) and adenosine triphosphate (ATP) as input signal and fluorescence signal as output signal, if single-strand DNA (DNA-L), single-strand DNA (DNA-S), and ATP were present at the same time, one segment of DNA-L formed a hairpin ring with ATP, and the other segment of DNA-L formed a completely complementary hairpin stem with DNA-S. The hairpin DNA was detached from the GO surface, and PicoGreen dye was embedded into the hairpin stem, and the fluorescence signal was enhanced. The molecular logic gate was constructed through the establishment of logic histogram, logic circuit, truth table, and logic formula. The biosensor-related performances including sensitivity, selectivity, and linearity were investigated, respectively. Results: We have successfully constructed a AND logic gate. The detection limit of ATP is 138.0 pmol/L (3σ/slope) with detection range of 50–500 nmol/L (R2 = 0.98951), and its sensitivity is 4.748 × 106–6.875 × 108 a.u. (mol/L)−1. Conclusions: The logic gate hairpin aptamer sensor has the advantages of high sensitivity, low detection limit, and low cost, and can be successfully applied to the detection of adenosine triphosphate (ATP) in actual human urine samples. [ABSTRACT FROM AUTHOR]

We study via DFT and TDDFT calculations the photophysical processes of a styryl‐bodipy derivative, (1), of its monometallic complexes 1‐M2+ (M = Ca, Zn, and Hg), and its trimetallic complex (2) unprotonated, protonated and complexed with water molecules in water solvent and in acidic conditions. The main targets of this study are to gain information regarding published reports on fluorophore species mentioning that fluorescent switching results from trace water, to study how 1 behaves in water solvent which is a common used solvent for molecular logic gates (MLG), and how it behaves in acidic conditions. We conclude that in water solvent, as in acetonitrile solvent (which was found before both theoretically and experimentally) there will be a quenching of emission spectra in 1 and 1‐M2+ and a retaining of emission in 2. However, contrary to acetonitrile solvent, in water, a weak peak will be observed for 1 and 1‐M2+, due to a small ratio of reversible protonation, showing that in acetonitrile 1 acts as a better MLG candidate than in water solvent. On the other hand, in acidic conditions all five species will emit and as a result, 1 will not be an AND MLG, showing that the selection of the solvent conditions is crucial for a species to act as an MLG candidate. Finally, we conclude that the retaining of emission is accomplished by the simultaneous tetrahedral geometry of all three aniline N atoms. [ABSTRACT FROM AUTHOR]

Precise detection of single-nucleotide mutations (SNMs) is extremely important in various biomedical applications, but the simultaneous detection of multiple SNMs remains a great challenge. Herein, we developed a new method based on CRISPR/Cas9 system for multiple SNMs detection. The CRISPR/Cas9 system transduces the nucleic acid into an intermediate trigger to initiate the isothermal amplification reaction and further form fluorescence signals. According to this strategy, we established nucleic acid bio-computing operations-molecule logic gate in simultaneous distinction of the genetic locus. We demonstrate that the fluorescence signals generated from different input combinations can be used to discriminate the multiple genetic locus, and the molecular logic gate has great potential in single-base mismatch detection. In addition, the successful assay of real samples indicates that the novel strategy could further adapt for the pathogenic monitoring and biomedical research. A strategy based on the CRISPR/Cas9 system was introduced to detect the multiple single-nucleotide mutations and a AND logic gate was constructed to discriminate the genetic locus. Image 1 • A novel method was developed to detect SNMs by CRISPR/Cas9 triggered signal amplification. • The multiple target sites were simultaneously recognized by Cas9n system. • Molecular logic gate was designed to diagnose multiple genetic locus. • Such methods were successfully applied in P. infestans genomic DNA detection. [ABSTRACT FROM AUTHOR]

Three quinoline‐based Low Molecular Weight Gelators (LMWG's), containing benzimidazole and long alkyl chain moieties, with excellent gelation abilities have been designed and synthesized. The gel properties were studied by IR and NMR spectroscopies, scanning electron microscopy (SEM) and rheological measurements. The gelators showed excellent ability as efficient colorimetric and fluorescent sensors for detection of Hg2+ and Cu2+ ions in aqueous media. The supramolecular gel was selectively transformed into solution in the presence of Hg2+ ion alongside complete quenching of its fluorescence intensity. In the presence of Cu2+ ion, the gelator exhibited a significant color change from white to dark pink and its fluorescence intensity was substantially reduced in gel‐gel state. Other competing ions such as Mn2+, Zn2+, Pb2+, Cd2+, Mg2+, Ni2+and Al3+, induced no change under the same conditions. The gel function as molecular logic gate was also investigated and found that, the gelators implement the functions of INH and NOT gates with water and Hg2+ ion as inputs and gel formation and fluorescence intensity as outputs. [ABSTRACT FROM AUTHOR]

[Display omitted] • Tb3+ ion modified an anionic MOFs fluorescent probe was obtained by encapsulation. • Tb3+@HDU-1 has abundant multi-emission fluorescence centers. • With low detection limits for sensing Fe3+ and Cu2+ ions in aqueous solutions. • Tb3+@HDU-1 has different fluorescence responses for Fe3+ and Cu2+ ions. • A logic gate to distinguish quenching Fe3+ and Cu2+ ions in aqueous solution. We successfully synthesized a stable anionic microporous metal-organic framework (MOF) HDU-1 ([Me 2 NH 2 ] 2 In 2 [(TATAB) 4 (DMF) 4 ](DMF) 4 (H 2 O) 4) and constructed a fluorescent probe Tb@HDU-1 by an exchange strategy. Because of its suspension distinct fluorescent response of Tb(III) characteristic transition and ligand emission, the Tb@HDU-1 can be used as fluorescent probe for sensing towards Fe3+ and Cu2+ ions. It is surprising that Tb@HDU-1 is used as a ratiometric fluorescent probe for Cu2+ ions while only single peak detection for Fe3+ ions, which describes a particular rare example of a sensor based on Ln-MOFs to distinguish quenching Fe3+ and Cu2+ ions. Hence we designed a molecular logic gate device for making the distinction of Fe3+ and Cu2+ ions more clearly and appropriately. In addition, the different quenching effect between Fe3+ and Cu2+ ions may be ascribed to the differences of competitive absorption and interaction between frameworks and metal ions. [ABSTRACT FROM AUTHOR]

The metal ion and anion recognition abilities of the newly synthesized acridone derivative having amide and ester groups were studied by UV–vis and fluorescence spectroscopies. The sensor molecule revealed selective recognition toward Ca(II), Hg(II), and fluoride in acetonitrile. Based on X‐ray crystallographic and 1H NMR analyses, intramolecular bifurcated H‐bond is formed between the acridone NH and the amide oxygens in the free receptor. Addition of Ca(II) and Hg(II) induced large fluorescence enhancements and changes in the 1H NMR shifts due to complexation, while fluoride deprotonated the sensor molecule giving rise to a new emission band. Selective sensing of Hg(II) based on absorption changes was also observed, presumably due to the tautomerization of the acridone unit upon complexation. The optical spectroscopic behavior in the presence or absence of Ca(II) and fluoride as chemical inputs provided an opportunity to construct IMP, INH, XOR, and XNOR molecular logic gates as well as a complementary IMP/INH circuit, and integrated logic functions such as a half‐subtractor (XOR/INH combination) and a magnitude comparator (XNOR/INH combination). [ABSTRACT FROM AUTHOR]

For the first time, we have reported the metal ion sensing behaviour of a fluorescent probe APAP (derivative of 4-amino/4-formyl antipyrine) along with its precursors (AAP-4-Aminoantipyrine, FAP-4-Formylantipyrine) and explained the tuning of precursors resulted in difference in the sensing behaviour. The two antipyrine precursors (4-amino/4-formyl antipyrine) were condensed together to form a new host molecule APAP, which acts an effective fluorescent chemosensor for detection of Fe3+ ions. The precursors AAP and FAP would able to detect Al3+ and Cr3+ ions respectively. The antipyrine precursors as well as the antipyrine derivative showed fluorescence response towards trivalent cations when treated with various metal ions in CH3OH:H2O (1:9, v/v) medium. Binding stoichiometry between APAP and Fe3+ ion was 1:1 from Jobs' plot and the binding constant value was calculated as 5.3 × 105 M−1 by Benesi–Hildebrand plot. Addition of Na2EDTA to the [APAP-Fe3+] complex solution quenched the fluorescence emission, indicating the reversible nature of the probe. The binding of APAP with Fe3+ was based on restricted PET with CHEF process. Quantum mechanical studies using time dependent density functional theory (TDDFT) have also been carried out to understand the mechanism of Fe3+ binding mode with APAP probe. With respect to various pH, the probe APAP exhibited an AND molecular logic gate behaviour when H+ and Fe3+ ions were given as inputs. For the first time, the metal recognition property of a fluorescent probe along with its precursors was studied. [ABSTRACT FROM AUTHOR]

Light‐triggered substituted azobenzene‐based molecular switches are well known for their potential applications as molecular machines. The Z‐isomer stability affected by heteroaromatic groups, extended aromaticity, different substituents, and varying the solvents based on their polarity. In this regards, five different anthraquinone/imidazole‐based azobenzene derivatives have been synthesized with different electronic push/pull substituents. The detailed study of photoswitching processes with kinetic data was appraised by using UV/Vis and 1H‐NMR spectroscopic techniques. The investigation of light‐induced hydroxyl group conversion to quinone‐hydrazone tautomerization has been observed during the isomerization. Most importantly, intermolecular hydrogen bonding interaction between tautomeric form and a higher polar solvent (DMSO) block the isomerization, but in a less polar solvent (DCM), light‐induced trans ↔ cis isomerization takes place by tautomerization pathway with well‐separated π→π* and n→π* transitions. Further, the detailed mechanistic study of solvent‐assisted light‐induced tautomerization with the role of hydrogen bonding and the following WRITE‐READ‐ERASE‐READ system have been derived by using molecular logic gates. [ABSTRACT FROM AUTHOR]

A simple julolidine based chemosensor (JT) was designed and synthesized by single condensation step. JT displayed excellent selectivity and sensitivity with on-off responses towards Zn2+ and Cu2+ over other biologically relevant metal ions in aqueous media. Upon addition of Zn2+ ions, JT exhibited a significant blue shift in emission followed by turn- on enhancement while with Cu2+, the fluorescence intensity of JT was completely vanished. The 1:1 binding affinity between JT and Zn2+/Cu2+ was proposed by Job's plot analysis. The detection limit for Zn2+ and Cu2+ ions reached at 3.5 × 10−8 M and 1.46 × 10−6 M, respectively. The sensing mechanism of JT with Zn2+/Cu2+ was supported by DFT calculations. Based on photophysical studies and its reversibility environment with EDTA, molecular logic gates were fabricated. Furthermore, JT was successfully established to detect intracellular Zn2+ ions in live cells by turn-on response. A bifunctional chemosensor JT was synthesized to distinguish Zn2+ and Cu2+ ions based on emission on-off response. Unlabelled Image • New julolidine based Schiff base derivative (JT) was designed and synthesized and JT served as a selective emission on-off response towards Zn2+ and Cu2+ ions. • The sensor shows excellent sensitivity for Zn2+ and Cu2+ ions with an LOD at 3.5 × 10 -8 M and 1.46 × 10 -6 M, respectively. • The 1:1 binding model of the sensor JT with Zn2+/Cu2+ was established and reversibility of the chemosensor JT was proved by experiments with EDTA. • JT was successfully established to track intracellular Zn2+ ions in HeLa cells. [ABSTRACT FROM AUTHOR]

Abstract Since dyes are available in huge quantities and have the well-established chemistry involved in their synthesis, their use in chemosensing could be continued. In the current study, a new and reversible colorimetric and fluorometric chemosensor based on available triaryl methane dye (brilliant green (BG)) - phosphotungstic acid (PTA) complex has been designed for determination of ascorbate (AscH−1) ion in water/DMSO (90:10 v/v, 1.0 mmol L−1 HEPES, pH 7.0). The "ON-OFF" fluorescence and colorimetric responses of this ion association complex to AscH−1 were based on a displacement mechanism. For the detection of AscH−1, the linear ranges achieved for UV–Vis absorbance and fluorescence experiments were 3.9–62.6 μmol L−1 and 1.9–85.4 μmol L−1, respectively. The limits of detection for both of them were also calculated to be 0.4 and 0.2 μmol L−1. The proposed method was also successfully utilized for rapid recognition of ascorbate in juice samples, human serum, and the formulation of supplement products. Moreover, the proposed chemosensor capability of functioning as INHIBITION–type sensor with PTA and AscH−1 as chemical inputs was indicated by the investigation of the molecular logic behavior of this chemosensor. Eventually, a sequential memory unit displaying "Write-Read-Erase-Read" function could be integrated based on the reversible and reproducible system. Graphical abstract Unlabelled Image Highlights Notably it is worth mentioning that the present chemosensor has advantages in the fact that: • A novel probe showed fluorescent/colorimetric response to AscH− was developed. • This probe was successfully utilized for rapid recognition and monitoring of ascorbate. • This receptor demonstrates the function of "INHIBITION" logic gate. • The reversible sensing phenomenon can mimic "write-read-erase-read" logic circuit. • The proposed method, applied successfully for analysis of juice and biological samples. [ABSTRACT FROM AUTHOR]

Abstract A series of novel phenothiazine based pyridylhydrazones displaying large Stokes shifts, acidochromism and pH sensing in aqueous media was synthesized in good yields. Substituents with different electronic and steric effects were appended on the phenothiazine ring in order to fine tune its donor ability. The photophysical studies revealed the existence of enhanced ICT character in the compound bearing electron withdrawing 4 -cyanophenyl group. Effects of steric hindrance and increased conjugation were also examined by spectrophotometric studies. Acid sensing behavior in solution with pKa values in the range of 4.7–5.8 was observed in the hydrazones bearing one pyridyl group. These pKa values are similar to the pH of acidic intracellular organelles. Hydrazone bearing two pyridyl groups displayed an increased pH sensing range with two pKa values at 4.5 and 6.8. Reversible changes in color and spectrophotometric properties were observed in solution state. Also, reversible solid state acidochromism was displayed by all the hydrazones upon consecutive exposure of highly volatile TFA and TEA vapors. The reversibility of hydrazones was further utilized for the construction of molecular logic gates with inhibit (INH) function using TFA/TEA or HCl/NaOH as the chemical inputs. Graphical abstract Image 1 Highlights • Synthesis of blue-green and greenish-yellow light emitting phenothiazine based pyridylhydrazones with large Stokes shift. • Fast and reversible acid sensing behavior in solution state. • Detection of volatile acids in Solid state. • pKa values (4.5–6.7) similar to that of acidic cellular organelles. • Construction of multi-stimuli responsive two-way INHIBIT molecular logic circuit with acid and base as inputs. [ABSTRACT FROM AUTHOR]

Abstract A novel Schiff base L composed of fluorescein hydrazine and a phenol functionalized moiety has been designed and prepared via cost-effective condensation reaction. The L is utilized for selective sensing of Zn2+ over other environmental and biological relevant metal ions in aqueous alcoholic solution under physiological pH range. The binding of Zn2+ to the receptor L is found to causes ~23 fold fluorescence enhancement of L. The 1:1 binding mode of the metal complex is established by combined UV–Vis, fluorescence, and HRMS (high-resolution mass spectroscopy) spectroscopic methods. The binding constant (K a) for complexation and the limit of detection (LOD) of Zn2+ is calculated to be 2.86 × 104 M−1 and 1.59 μM, respectively. Further photophysical investigations including steady-state, time-resolved fluorescence analysis and spectral investigations including NMR (nuclear magnetic resonance), IR (infrared spectroscopy) suggest introduction of CHEF (chelation enhance fluorescence) with the suppression of C N isomerization and PET (photo-induced electron transfer) mechanism for the strong fluorescent response towards Zn2+. Finally, the sensor L is successfully employed to monitor a real-time detection of Zn2+ by means of TLC (thin layer chromatography) based paper strip. The L is used in the cell imaging study using African green monkey kidney cells (Vero cells) for the determination of exogenous Zn2+ by Immunofluorescence Assay (IFA) process. Graphical Abstract Unlabelled Image Highlights • A novel fluorescein-based probe with a simple structure for recognition of Zn2+ is synthesized via simple Schiff base condensation. • The probe shows promising fluorescence response, excellent selectivity, and high sensitivity (1.59 μM) toward Zn2+. • The binding modes of probe L with Zn2+ ion has been well demonstrated by UV–Vis, fluorescence, HRMS, 13C NMR, and FTIR spectroscopy. • The probe could be used for Zn2+ detection in various solvent medium and also in thin layer chromatography (TLC) paper with quick response. • The probe L serve as an excellent sensor in identifying Zn2+ in intracellular region of African green monkey kidney cells (Vero cells). [ABSTRACT FROM AUTHOR]

Abstract New hydrophilic fluorescent selective ion sensor based on phenazine and phthalazine moieties, 1,1′-(phenazine-2,3-diyl)-bis(3-(1,4-dihydroxyphthalazin-6-yl)urea) (1), has been designed, synthesized and characterized. Interestingly, sensor 1 exhibits prominent " turn-on " and " turn-off " fluorogenic signaling at 580 nm towards Fe2+ & AcO− and Sr2+ & Cu2+, respectively. The fluorescence titration experiments shed light on the nature of the interaction between 1 and guest molecules (Fe2+, Sr2+, Cu2+ and AcO−), which divulge that 1 is flexible enough to orient itself according to the size of the guest molecule. Water mediated excited-state intramolecular proton transfer (ESIPT) and photo-induced electron transfer (PET) mechanisms are responsible for the dual behavior of 1 , which binds with guest molecules in 1:1 stoichiometry. Based on the significant duplex fluorescence response of 1 , a molecular logic gate keypad lock with sixteen " on " passwords for a storage system has been developed. Graphical Abstract Unlabelled Image Highlights • Two fluorogenic signaling subunits bearing two different binding sites to detect ' selective ion ' in water • Cost effective, strong affinity (K a > 104), low LOD, selective, reversible, and stable probe for the detection of naturally abundant ions • " Turn–on " and " Turn–off " dual fluorescence behavior follows water mediated ESIPT and PET mechanisms • Three way molecular logic keypad lock with sixteen " on " passwords was developed [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Designed and synthesis of 2-(2-mercaptophenyl)-1H-benzo[de]isoquinoline-1,3(2H)-dione (L3). • Colorimetric and Ratiometric fluorometric Mercury (II) sensor. • Highly selective and sensitive. • Reversibility and logic gate applications. • High in theoretical estimation and experimental outcome. Abstract A novel colorimetric and ratiometric fluorescent chemosensor, 2-(2-mercaptophenyl)-1H-benzo[de]isoquinoline-1,3-(2H)-dione (L3) is reported for Hg2+ ions. The selective binding of Hg2+ to L3 afforded new absorbance and fluorescence peaks at 438 nm and 480 nm, in addition to the existing bands of L3 at 332 nm and 376 nm. It also showed apparent colour change from colourless to yellowish green and weak fluorescent to bright yellowish green strong fluorescent due to selective binding of Hg2+ ion. The sensor forms a 1:1 stoichiometry with high binding constants (3.89 × 104 mol−1L) and limit of detection 1.74 × 10-8 M with high selectivity and sensitivity towards Hg2+ in the presence of other interfering metal ions. More importantly, it has good practicability in environmental water sample. The outcome of photo-physical experiment has also been in good accordance with the time-resolved fluorescence life decays and the density functional theory (DFT) estimations. Moreover, the L3 -Hg2+ solution displayed high colorimetric and fluorimetric reversibility via the addition of KI. This reversibility in fluorescence showed potential applicability of chemosensor L3 as " on–off–on " naked eye sensor. [ABSTRACT FROM AUTHOR]

Molecular logic gate has been proposed using single‐strand DNA (ssDNA) consisting of basic four nucleobases. In this study, density functional theory and non‐equilibrium Green's function based first principle approach is applied to investigate the electronic transmission characteristics of ssDNA chain. The heavily hydrogen‐doped‐ssDNA (H‐ssDNA) chain is connected with gold electrode to achieve enhanced quantum‐ballistic transmission along 〈1 1 1〉 direction. Logic gates OR, Ex‐OR, NXOR have been implemented using this analytical model of H‐ssDNA device. Enhanced logic properties have been observed for ssDNA after H adsorption due to improved electronic transmission. Dense electron cloud is considered as logic 'high' (1) output in presence of hydrogen molecule and on the contrary sparse cloud indicate logic 'low' (0) in the absence of hydrogen molecule. Device current is significantly increased from 0.2 nA to 2.4 µA (approx.) when ssDNA chain is heavily doped with hydrogen molecule. The current–voltage characteristics confirm the formation of various Boolean logic gate operations. [ABSTRACT FROM AUTHOR]

Abstract We present here the synthesis of a simple and low-cost Schiff base chemosensor (HL) for selective detection of both Zn(II) and Cu(II) ions in HEPES buffer pH = 7.4. The chemosensor HL exhibits quick response through fluorescence and colorimetric changes for both Zn(II) and Cu (II) ions as examined by fluorescence and absorption titrations. Both the metal ions form 1:1L– Zn(II) (complex 1) and 1:1L– Cu(II) (complex 2) complexes, confirmed by Job's Plot. We are successful to elucidate the structure of complex 1 through X-ray diffraction analysis. Reversibility of the chemosensor in its binding with Zn(II) and Cu (II) ions separately is also examined in presence of Na 2 EDTA solution. The enhancement of fluorescence intensity of the chemosensor is based on the chelation-enhanced fluorescence (CHEF) effect of L–Zn(II) with the inhibition of both photoinduced electron transfer (PET) effect and C˭N isomerization in excited state and the quenching effect is due to the paramagnetic nature of Cu(II) to the L–Zn(II) system. Furthermore, the geometry and spectral property of HL and both the metal complexes have been studied by DFT, TD-DFT calculations. The limit of detection (LOD) values of both the ions are 2.29 × 10-9 M and 3.67 × 10-9 M, respectively. These values clearly suggests that HL is a promising chemosensor in monitoring Zn(II) and Cu(II) ions in the biological and environmental study with excellent accuracy and precision. The propensity of the chemosensor to detect intracellular Cu(II) and Zn(II) ions in Candida albicans cell lines by fluorescence imaging is also demonstrated in this study. Furthermore, molecular logic gates have been developed based on the idea where chemically encoded information as the input is converted into fluorescent signals as the output. In this work, the designed fluorescent chemosensor exhibits dual logic gates (XOR, AND) involving Zn(II), Cu(II) and Na 2 EDTA. Graphical abstract fx1 [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • We have to design and synthesised a new quinoline conjugated rhodamine based chemosensor (RhQA). • The RhQA was selectively sensed two paramagnetic metal ions via different analytical tool in an aqueous medium. • This chemosensor were used for construction of the molecular logic gate. • Moreover, Chemosensor is used in vivo bio-sensing and bio-imaging for the detection of the Fe3+ ions in zebrafish embryos. Abstract A Rhodamine based quinoline conjugated fluorescence chemosensor (RhQA) was delineated for the detection of two paramagnetic metal ions (Fe3+/Cu2+) through various analytical techniques. The addition of Fe3+ and Cu2+ ions induced a great enhancement in the absorption of RhQA; moreover, Fe3+ also induced a strong fluorescence enhancement. Hence, this is an admirable example for the selective detection of the biologically/environmentally significant transition metal ions as dual chemosensor. The obtained results reveal that the chemosensor (RhQA) has remarkable selectivity towards Fe3+/Cu2+ ions even in the presence of higher concentration of various interference metal ions such as Pb2+, Cd2+, Hg2+, Zn2+, Ni2+, Co2+, Mn2+, Fe2+, Cr3+, Ca2+, Ba2+, Mg2+, Na+, K+, and Ag+. Its excellency in sensitivity was confirmed by the obtained linear relationship with Fe2+/Cu3+ ions, and the calculated detection limit values are, 1.8 × 10−8 and 3.3 × 10−8 M for Cu2+ and Fe3+ ions respectively. More interestingly, this chemosensor, RhQA was successfully employed to trace out the intra cellular Fe3+ ions in Zebrafish embryos. [ABSTRACT FROM AUTHOR]

Revaluation of Copper(II)-Schiff base complex for sensing of d -penicillamine and development of a molecular logic gate through the combined approach. The synthesized Cu(II)-salicylaldehyde rhodamine B hydrazone complex is characterized through FTIR, NMR, Mass spectrometry, UV–Vis, and fluorescence titrations. The recognition of D-PA is executed both colorimetrically and fluorometrically through the "Turn-off" mechanism. [Display omitted] d -penicillamine (D-PA) being a tri-functional organic compound (thiol, amine, and carboxylic acid) is used as a chelating drug for many serious diseases like Wilson's disease. Due to its serious adverse effects, regular monitoring of blood and urine for D-PA is required during the clinical application of the drug. The dye-containing Cu(II)-Schiff base complex is revisited for easy monitoring of D-PA and the development of a new molecular logic gate through extensive studies. Revaluation is carried out in light of extensive experimental evidence and theoretical rationalization which help to achieve the target. The synthesized Cu(II)-salicylaldehyde rhodamine B hydrazone complex is characterized through FTIR, NMR, Mass spectrometry, UV–Vis, and fluorescence titrations. The crystal structure of the complex is optimized through DFT studies and found distorted square planar. Calculations of Frontier Molecular Orbitals (FMOs) assist to understand the electronic and optical properties of the complex. The recognition of D-PA (LOD = 2.60 × 10-8 M) is executed both colorimetrically and fluorometrically through the "Turn-off" mechanism. The NAND-type molecular logic gate has been developed. [ABSTRACT FROM AUTHOR]

A novel fluorescent molecular logic gate 1 is demonstrated as a two-input AND logic gate for the detection of acidity and oxidizability. Designed according to an electron-donor–spacer–fluorophore–spacer–receptor ’ format, the modules are represented by ferrocene as the electron donor, 1,8-naphthalimide as the fluorophore and piperazine as the proton receptor. In the presence of elevated concentrations of H + and Fe 3+ , the molecule switches ‘on’ emitting at λ max  = 530 nm with Φ f  = 0.060 at 10 −4  M H + and 50 μM Fe 3+ . The H + binding and apparent Fe 3+ binding constants determined by fluorimetric titrations in 1:1 ( v/v ) methanol/water are log β H+  = 8.1 and log β Fe3+  = 4.7. Modulation of the fluorescence output results from controlling competing photoinduced electron transfer (PET) at the ferrocene end and internal charge transfer (ICT) at the piperazine end. Time-resolved fluorescence spectroscopy reveals a single fluorescent lifetime of 5.8 ns, while from absorption transient spectroscopy a remarkable fast decay signal <2 ps is observed. Comparison is made with methylpiperazine 2 and piperazine fluorescent pH indicator 3 as model compounds. [ABSTRACT FROM AUTHOR]

A new rhodamine-6G-based chemosensor X was designed and synthesized for the colorimetric and fluorometric detection of Hg 2+ . The chemosensor X responsed to Hg 2+ had good sensitivity, high selectivity and excellent reversibility in HEPES buffer (10 mM, pH 7.4)/CH 3 CN (40:60, V/V). The recognition mechanism of X toward Hg 2+ was evaluated by Job's plot, IR and MS. Meanwhile, X -Hg 2+ fluorescence lifetime was also measured. It was interesting that X displayed favorable reversibility to form an “off-on-off” type signaling behavior with the Hg 2+ -induced emission spectra being quenched by I − . Furthermore, it could be applied as a molecular logic gate and test strips based on X exhibited a good reversibility selectivity to Hg 2+ . [ABSTRACT FROM AUTHOR]

A highly colorimetric and fluorimetric chemosensor, 3-oxo-[1,4]-benzothiazin-2-ylidene acetohydrazide ( L2 ) is reported for the mercury detection. In HEPES-buffered solution (CH 3 CN: H 2 O, 1:2, v/v, pH 7.2), L2 showed a characteristic absorption peak at 340 nm, after addition of Hg 2+ induces color change from light yellow to purple with significantly enhancement in absorbance at 340 nm and a new band centered at 550 nm with red-shift of 110 nm. Furthermore, the L2 exhibited high sensitivity and selectivity overall emission change of more than 100-fold fluorescence intensity enhancement towards Hg 2+ ion with a 1:1 binding stoichiometry (1.938 × 10 3  M −1 binding constant within detection limit as low as 5.4 × 10 −8  M) in water samples. Apart from this, theoretical elucidation of the experimental outcome has also been supported by applying density functional theory (DFT) to the ligand and the complex. In situ, the solution of L2 + Hg 2+ complex displayed high reversibility by I − through Hg 2+ displacement approach. This reversibility in fluorescence suggested that the promising applicability of chemosensor as “off–on–off” naked eye sensor and practical applicability of L2 as an INHIBIT logic gate based on the emission changes with the inputs of Hg 2+ and I − was investigated. [ABSTRACT FROM AUTHOR]

In this work, a Zn(II)-containing coordination polymer, [Zn2(2,4′-tmbpt)2( o-bdc)2]·5H2O ( 1) [2,4′-tmbpt = 1-((1 H-1,2,4-triazol-1-yl)methyl)-3-(4-pyridyl)-5-(2-pyridyl)-1,2,4-triazole and o-H2bdc = 1,2-benzenedicarboxylic acid] has been synthesized hydrothermally. The structure of the compound has been characterized by single crystal X-ray crystallography, elemental analysis, infrared spectra, thermogravimetric analysis and powder X-ray diffraction analysis. Compound 1 features a 2D layer structure formed by the cross-link of the wave-like chains and helical chains. Because the uncoordinated nitrogen atoms in compound 1 can bind H+, the luminescent spectra of compound 1 in aqueous solutions of different pH from 1 to 7 have been investigated. The result indicates that this compound can be used as a sensitive and efficient pH fluorescent sensor, which can be further used for the design of molecular logic gate in the narrow pH range of 2-3. The pH response mechanism of compound 1 may be the disturbance of the conjugated system resulting from the protonation of the 2,4′-tmbpt ligand in the compound, which has been proved by the UV-vis absorption spectra and density functional theory (DFT) calculation. [ABSTRACT FROM AUTHOR]