A new fluorescent probe for sensing Al3+ ions in the solution phase and CH3COO- in the solid state with aggregation induced emission (AIE) activity.

An AIE (aggregation induced emission) active probe DFP-AMQ was designed and synthesized as a hexa-coordinated N2O donor chelator for the selective sensing of Al3+ colorimetrically as well as fluorimetrically with a 27-fold fluorescence enhancement for CH3CN-H2O (9 : 1, v/v, pH 7.2, HEPES buffer). The fluorescence enhancement occurred through the blocking of ESIPT, chelation enhanced fluorescence effect (CHEF) arose, and as a result fluorescence enhancement was observed through 1 : 1 complexation with Al3+ ions. Detailed spectroscopic studies including UV-Vis, FTIR, 1H NMR, and HRMS studies were carried out to characterize the probable structure of DFP-AMQ including the complexation of DFP-AMQ with Al3+ ions. The spectrophotometric and spectrofluorimetric titrations revealed strong binding towards Al3+ and the K d values were obtained from UV-Vis (3.26 × 10-5 M-1) and fluorescence titration (2.02 × 10-5 M-1). The limit of detection of Al3+ by DFP-AMQ was 1.11 µM. The quantum yields of DFP-AMQ and [DFP-AMQ-Al]+ were calculated to be 0.008 and 0.211, respectively. Dynamic light scattering (DLS) studies showed that the sizes of the particles increased with increasing water percentage due to aggregation. SEM (scanning electron microscopy) studies revealed interesting morphological changes in microstructures in which DFP-AMQ demonstrated a rod-like shape, which was converted to a spherical-like shape in the presence of Al3+ and when DFP-AMQ aggregated in H2O it showed aggregated block-like shape. In the solid phase, DFP-AMQ with nitrate has no particular shape, but in the presence of acetate, it converts to stone-like shape. This probe (DFP-AMQ) could be employed for on-site Al3+ ion detection in the solid state.

Combined Experimental and Theoretical Studies on the Rubbing-Induced Fluorescence Behavior of a Luminophore in the Solid State.

It is intricate to break and make chemical bonds in solid states compared to their solution states, so it is imperative to ascertain green proficient approaches by regulating the solid-state structures and their related material properties. Here, the rubbing-induced photoluminescence behavior of a luminophore (RIL) of the benzimidazole family in the solid state has been accomplished. Interestingly, upon gentle rubbing or mere scratching, solid-state fluorescence from the nonemissive pristine RIL was observed due to the aggregation-induced emission (AIE) phenomenon in the solid state, for which the phenolic moiety is present in the molecule and is accountable. The structure-property relationship of RIL and the mechanism responsible for this solid-state fluorescence characteristics have been explained with the help of experimental (using the single-crystal structure, powder X-ray diffraction (PXRD), scanning electron microscopy (SEM) images, etc.) and theoretical (by DFT and TDDFT) studies. The crystal arrangements with different stacking interactions and the SEM images after being rubbed revealed that the mechanical force- or pressure-induced slight deformation in the crystal arrangement notably facilitated the strong emission in the solid state. This rubbing-induced solid-state fluorescence in a new luminophore (RIL) through stacking of layers restricting the molecular motion has been developed here for the first time, and it can be explicitly employed in steganography techniques for data security. This present study will open up a new insight into the use of this RIL as a solid-state smart material for data security in coding devices in the future, and this developed approach may be helpful to ameliorate the design of new-generation smart materials by modifying the structure to attain other characteristics.

A new metal-free benzorhodol-based photoluminophore selective for carbon monoxide detection applicable in both in vitro and in vivo bioimaging.

A new benzorhodol-based non-fluorescent organic frame (DEB-CO) detects carbon monoxide (CO) selectively through a spirolactam ring-opening mechanism. Herein, the selective off-on fluorogenic behavior of this probe towards CO has been achieved without any assistance of precious and hazardous metals (e.g. Pd2+) as additional substrates. Moreover, the red-emissive probe motivated us to apply in situ tracing in mice and living cells. The selective off-on fluorogenic behavior of this probe towards CO originating from CORM-3 in vitro and in vivo with a limit of detection as low as 64.29 nM (for CORM-3) has been observed. Additionally, this probe is capable of sensing toxic carbon monoxide gas. This probe has also been utilized to detect intracellular CO in MCF7 cells (in vitro) and to spot the distribution of CO in mice (in vivo) by acquiring bioimages with the help of confocal microscopy, which indicates that DEB-CO is a smart competent probe for this purpose.

A deoxygenation-switch-based red-emitting fluorogenic light-up probe for the detection of highly toxic free bilirubin in human blood serum.

Reaction-based chemical switches are attracting great interest due to their high selectivity, and their use has become a powerful technique for developing fluorogenic probes. Herein, a benzorhodol-derivative-attached N-oxide probe (DEBNox) has been designed as a new fluorogenic probe for the detection of the biologically toxic species bilirubin based on a deoxygenation switching mechanism. Upon reaction with added Fe3+, bilirubin produces Fe2+ ions in situ, which in turn promote a deoxygenation reaction with DEBNox to generate the corresponding high-red-fluorescence (λem: ∼623 nm) benzorhodol derivative (DEB). This type of Fe3+-mediated response helps the probe to act as a qualified turn on selective fluorescence sensor for bilirubin with a detection range as low as 33 nM. Moreover, the probe was successfully employed to detect free bilirubin in human blood serum specimens with acceptable accuracy and reliability. This DEBNox-based light-up strategy also facilitates the construction of reliable and highly sensitive assays based on a paper-based strategy, similar to pH-indicator paper, as is demonstrated here via bilirubin detection in real serum samples. These findings could be useful for developing powerful diagnostic tools for the detection of free bilirubin in the near further.

Encapsulation and Stabilization of a Donor-Acceptor Stenhouse Adduct Isomer in Water Inside the Blue Box: A Combined Experimental and Theoretical Approach.

We synthesized two types of donor-acceptor Stenhouse adducts (DASAs), a new type of photochromic molecules showing dual color in two different isomeric forms in solution phase, using Meldrum acid (DASA-Mel) and barbituric acid (DASA-Bar), along with a naphthalimide derivative to obtain interesting fluorescence properties. DASA-Mel was found to have fast photochromic conversion in comparison to DASA-Bar, evident from ultraviolet-visible (UV-vis) and fluorescence spectroscopic studies. The colored form of DASA-Mel was encapsulated inside the water-soluble Stoddart's blue box and became soluble in water much faster than DASA-Bar. Interestingly, the competitive encapsulation experiment showed that DASA-Mel was selectively encapsulated inside the blue box in water whereas DASA-Bar was mostly separated out from the solution after centrifugation, and this phenomenon was confirmed by 1H and DOSY NMR and mass spectroscopies. Moreover, we found through density functional theory (DFT) optimization that the open form of DASA-Mel was more stable during the encapsulation reaction in a water medium in comparison to DASA-Bar. The calculated binding energies of encapsulated DASA-Mel and DASA-Bar are -10.2 and -9.9 kcal/mol, respectively, clearly showing that the former is more stable by 0.3 kcal. Consequently, the organic macrocycle selectively separating one kind of DASA from a mixture by encapsulation in water is reported for the first time with experimental and theoretical support in the literature.

A new half-condensed Schiff base platform: structures and sensing of Zn2+ and H2PO4- ions in an aqueous medium.

A newly designed and synthesized half-condensed organic moiety 2-hydroxy-5-methyl-3-[(2-phenylamino-phenylimino)-methyl]-benzaldehyde (HL') and a Zn2L4 complex sequentially detect Zn2+ and H2PO4- ions as low as 1.13 nM and1.23 µM, respectively. HL' and a dinuclear Zn(ii) complex of in situ generated L- in a solution formulated as Zn2L4 under investigation were characterized by physicochemical and spectroscopic studies along with detailed structural analyses by single-crystal X-ray crystallography. The selectivity and sensitivity of HL' towards Zn2+ ions and of the Zn2L4 complex towards H2PO4- ions are based on CHEF and via displacement pathways, respectively. Dual sensing of Zn2+ ions and H2PO4-ions in an aqueous medium via "Green-Blue-Green" emission with the reversible transformation of in situ formed HL' to HL was established by detailed electronic absorption and emission spectroscopic studies. This non-cytotoxic probe (HL', i.e. produced HL in solution) and Zn2L4 complexes are able to monitor the subcellular distribution changes of Zn2+ and H2PO4- ions, respectively, by fluorescence microscopy using the human semen sample.

A Nuclear-Localized Naphthalimide-Based Fluorescent Light-Up Probe for Selective Detection of Carbon Monoxide in Living Cells.

A nuclear-localized fluorescent light-up probe, NucFP-NO2, was designed and synthesized that can detect CO selectively in an aqueous buffer (pH 7.4, 37 °C) through the CO-mediated transformation of the nitro group into an amino-functionalized moiety. This probe triggered a more than 55-fold "turn-on" fluorescence response to CO without using any metal ions, e.g., Pd, Rh, Fe, etc. The enhanced response is highly selective over a variety of relevant reactive oxygen, nitrogen, and sulfur species and also various biologically important cationic, anionic, and neutral species. The detection limit of this probe for CO is as low as 0.18 µM with a linear range of 0-70 µM. Also, this fluorogenic probe is an efficient candidate for monitoring intracellular CO in living cells (RAW 264.7, A549 cells), and the fluorescence signals predominantly localize in the nuclear region.

Bilirubin Quantification in Human Blood Serum by Deoxygenation Reaction Switch-Triggered Fluorescent Probe.

A coumarin-based fluorescent compound, bilirubin fluorescent probe N-oxide (BFPNox), was successfully designed and synthesized for highly selective and sensitive detection of free bilirubin with short response time. The fluorescence "turn-on" response of the probe is based on the in situ generated Fe2+-mediated deoxygenation reaction of N-oxide from the diethylarylamine group of the probe, where the group attached to the coumarin π-conjugated system is responsible for the fluorescence quenching state of the probe, BFPNox. Here, the reaction of the added Fe3+ ions with bilirubin produces Fe2+ ions in situ in aqueous buffer. Fluorescence enhancement of BFPNox was achieved by more than 12-fold when a double equivalent of bilirubin solution was added in reaction buffer at pH 7.2 (50 mM HEPES, 5% DMSO) at 25 °C under excitation at 400 nm. It detected free bilirubin as low as 76 nM in an aqueous system without any interference of metal ions, anions, and other important biomolecules with a linear concentration range of 0-10 µM (R2 = 0.991). The probe was also employed in the estimation of free bilirubin in human serum specimens to verify the efficacy of this probe. With these, it is revealed that this probe is a good candidate to be used as a powerful diagnostic tool for the assessment of free bilirubin with significant accuracy and reliability.

Recent Advances in Fluorescence Light-Up Endogenous and Exogenous Carbon Monoxide Detection in Biology.

Considerable attention has been paid by the scientific community to detect toxic carbon monoxide (CO) in sub-cellular organelles like mitochondria, lysosomes, nuclei, etc. due to their generation and accumulation through numerous biological processes and their role as signal transducer, therapeutics, etc. Various methods are also available for detection of CO, but fluorescence light-up detection is considered the best due to its easy and accurate sensing capability. As of now, no review is available in the literature dedicated to fluorescent detection of only CO both in vitro and in vivo, but considering the huge amount of work reporting every year, it is necessary to have an account of all the recent significant works devoted to it. This review will give special attention to the most noteworthy development of fluorescent light-up probes for the detection of cellular and sub-cellular targetable CO starting from 2012 and emphasizing also the mechanism of action and the applications.

A Lysosome-Targetable Fluorescence Sensor for Ultrasensitive Detection of Hg2+ in Living Cells and Real Samples.

A new lysosome-targetable fluorescence sensor, Lyso-HGP, was designed and synthesized based on 4-methyl-2,6-diformylphenol as a fluorophore. Lyso-HGP displays highly sensitive fluorescent detection of Hg2+ in HEPES buffer solution (10 mM, DMSO 1%) of pH 7.0 at 37 °C due to the formation of highly fluorescent formyl-functionalized derivative Lyso-HGP-CHO. The sensor triggered a "turn-on" fluorescence response to Hg2+ with a simultaneous increase of fluorescence intensity by 180-fold just after 10 min. The response is very selective over a variety of biologically relevant cations, anions, molecules, and competitive toxic heavy metal cations. The limit of detection (LOD) was calculated as low as 6.82 nM. So, it can be utilized to detect this toxic heavy metal in biology and environmental samples in an aqueous buffer medium. Also, the sensor is able to monitor the subcellular distribution of Hg2+ specifically localized in the lysosome's compartment in the MCF7 human breast cancer cell line by fluorescence microscopy.

Study on size dependent ion exchange property of nanosilica as green inorganic exchanger in radiochemical separation.

Silica nanoparticles (SiNPs) of different sizes were synthesized using different concentration of precursor material tetraethylorthosilicate (TEOS). The structural and morphological details of the material were obtained by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The SEM study was followed by energy dispersive spectroscopic analysis (EDS) for elemental analysis of the sample. The particle sizes were determined by dynamic light scattering (DLS) method. Ion exchange capacity was measured for different metal ions with sizes of the SiNPs and size-dependent ion exchange property of the material was investigated thoroughly. The nanomaterial of the smallest size of around 13.54 nm was used to separate carrier-free 90Y from 90Sr in column chromatographic technique using 1% aqueous EDTA as eluting agent at pH 6.

Highly Sensitive Ratiometric Chemosensor and Biomarker for Cyanide Ions in the Aqueous Medium.

A newly designed cyanide-selective chemosensor based on chromone containing benzothiazole groups [3-(2,3-dihydro-benzothiazol-2-yl)-chromen-4-one (DBTC)] was synthesized and structurally characterized by physico-chemical, spectroscopic, and single-crystal X-ray diffraction analyses. The compound DBTC can detect cyanide anions based on nucleophilic addition as low as 5.76 nM in dimethyl sulfoxide-N-(2-hydroxyethyl)piperazine-N'-ethanesulfonic acid buffer (20 mM, pH 7.4) (v/v = 1:3). The binding mode between receptor DBTC and cyanide nucleophile has also been demonstrated by experimental studies using various spectroscopic tools and theoretical studies, and the experimental work has also been verified by characterizing one supporting compound of similar probable structure of the final product formed between DBTC and cyanide ion (DBTC-CN compound) by single-crystal X-ray analysis for detailed structural analyses. In theoretical study, density functional theory procedures have been used to calculate the molecular structure and the calculation of the Fukui function for evaluation of the electrophilic properties of each individual acceptor atom. Furthermore, the efficacy of the probe (DBTC) to detect the distribution of CN- ions in living cells has been checked by acquiring the fluorescence image using a confocal microscope. Notably, the paper strips with DBTC were prepared, and these could serve as efficient and suitable CN- test kits successfully.

A New Lysosome-Targetable Turn-On Fluorogenic Probe for Carbon Monoxide Imaging in Living Cells.

A lysosome-targetable fluorogenic probe, LysoFP-NO2, was designed and synthesized based on a naphthalimide fluorophore that can detect selectively carbon monoxide (CO) in HEPES buffer (pH 7.4, 37 °C) through the transformation of the nitro group into an amino-functionalized system in the presence of CO. LysoFP-NO2 triggered a "turn-on" fluorescence response to CO with a simultaneous increase of fluorescence intensity by more than 75 times. The response is selective over a variety of relevant reactive nitrogen, oxygen, and sulfur species. Also, the probe is an efficient candidate for monitoring changes in intracellular CO in living cells (MCF7), and the fluorescence signals specifically localize in the lysosome compartment.

Dosimetric Chromogenic Probe for Selective Detection of Sulfide via Sol-Gel Methodology.

Dinitrobenzenesulfonyl-protected naphthyl azo pyridine conjugate 1 has been designed and synthesized. Compound 1 acts as a nongelator in dimethyl sulfoxide (DMSO)-H2O (1:1, v/v) while its hydroxy counterpart 2 can form a nice gel in the same solvent. In the presence of sulfide, compound 1 undergoes rapid sulfonate ester hydrolysis and results in the formation of azo-naphthol 2 that responds in instant gelation. Such deprotection was extremely selective to sulfide; other analytes did not show measurable response. The sensing mechanism has been established by various spectroscopic techniques. Compound 1 in solution (DMSO-H2O) also shows a selective response toward sulfide over a series of other anions with a color change. Preparation of test kit with compound 1 allows detection of sulfide in solution and vapor states. Such kind of dosimetric sensing of chemical analytes by improvising the protection/deprotection of functional groups in gelator structure is rare in the literature, and to the best of our knowledge, this is the first example of a stimuli-responsive low-molecular-weight gelator which dosimetrically senses sulfide over other nucleophilic substrates.

Synthesis, characterization, redox behavior, DNA and protein binding and antibacterial activity studies of ruthenium(II) complexes of bidentate schiff bases.

Two new ruthenium(II) complexes of Schiff base ligands (L) derived from cinnamaldehyde and ethylenediamine formulated as [Ru(L)(bpy)2](ClO4)2, where L1 = N,N'-bis(4-nitrocinnamald-ehyde)ethylenediamine and L2 = N,N'-bis(2-nitrocinnamaldehyde)-ethylenediamine for complex 1 and 2, respectively, were isolated in pure form. The complexes were characterized by physicochemical and spectroscopic methods. The electrochemical behavior of the complexes showed the Ru(III)/Ru(II) couple at different potentials with quasi-reversible voltammograms. The interaction of the complexes with calf thymus DNA (CT-DNA) using absorption, emission spectral studies and electrochemical techniques have been used to determine the binding constant, Kb and the linear Stern-Volmer quenching constant, KSV. The results indicate that the ruthenium(II) complexes interact with CT-DNA strongly in a groove binding mode. The interactions of bovine serum albumin (BSA) with the complexes were also investigated with the help of absorption and fluorescence spectroscopy tools. Absorption spectroscopy proved the formation of a ground state BSA-[Ru(L)(bpy)2](ClO4)2 complex. The antibacterial study showed that the Ru(II) complexes (1 and 2) have better activity than the standard antibiotics but weak activity than the ligands.

A fluorescent probe for the selective detection of creatinine in aqueous buffer applicable to human blood serum.

A naphthalimide-based fluorescence light-up probe, FCP-Pd, has been designed and synthesized for selective detection and quantitation of creatinine in PBS buffer of pH 7.2 at 37 °C with a 'turn-on' response over a variety of interfering metal ions and/or anions and several biologically significant species. This probe is highly effective in estimating creatinine in human blood serum, which confirms the reliability and accuracy of this new system to be applied in clinical and toxicological analysis.

Preparation, structural characterization, and evaluation of ion-exchange behavior of a new polyoxometalate, [Me2NH2]3[Mo12O40S] in separation of carrier-free 90Y from 90Sr.

A new ion-exchanger having chemical formula [Me2NH2]3[Mo12O40S] and belonging to the class of Keggin type polyoxometalate was synthesized and characterized by single-crystal X-ray structure determination. The crystal of the exchanger is rhombohedral, space group R-3 with cell dimensions, a =16.504(18) Å, b =16.504(18)Å (1) Å, c =25.23(3)Å and α=90.00°, ß=90.00°, γ=120.00° and Z =6, 3.284gcm-3. The compound behaves as an ion-exchanger and it is significantly stable towards thermal, chemical environments and total radiation dose of 35.0kGy. Radiochemical separation of the short-lived daughter carrier-free 9°Y (T1/2 =64.08h) from its long-lived parent 90Sr (T1/2 =29 a) using this material at pH 6.0 with 1.0% EDTA solution as an eluent.

Development of a cell permeable red-shifted CHEF-based chemosensor for Al(3+) ion by controlling PET.

A structurally modified quinazoline derivative (L) acts as highly selective chemosensor for Al(3+) ions in DMSO-H2O (1:9, v/v) over the other competitive metal ions. L shows a red shifted fluorescence after the addition of Al(3+) ions and later the further fluorescence enhancement is due to chelation enhanced fluorescence (CHEF) through inhibition of photoinduced electron transfer (PET). This probe (L) detects Al(3+) ions as low as 9nM in DMSO-H2O (1:9, v/v) at biological pH. The non-cytotoxic probe (L) can efficiently detect the intercellular distribution of Al(3+) ions in living cells under a fluorescence microscope to exhibit its sensible applications in the biological systems.

A rhodamine-based 'turn-on' Al³âº ion-selective reporter and the resultant complex as a secondary sensor for F⁻ ion are applicable to living cell staining.

A newly designed fluorescent aluminum(III) complex (L'-Al; 2) of a structurally characterized non-fluorescent rhodamine Schiff base (L) has been isolated in pure form and characterized using spectroscopic and physico-chemical methods with theoretical density functional theory (DFT) support. On addition of Al(III) ions to a solution of L in HEPES buffer (1 mM, pH 7.4; EtOH-water, 1 : 3 v/v) at 25 °C, the systematic increase in chelation-enhanced fluorescence (CHEF) enables the detection of Al(III) ions as low as 60 nM with high selectivity, unaffected by the presence of competitive ions. Interestingly, the Al(III) complex (L'-Al; 2) is specifically able to detect fluoride ions by quenching the fluorescence in the presence of large amounts of other anions in the HEPES buffer (1 mM, pH 7.4) at 25 °C. On the basis of our experimental and theoretical findings, the addition of Al(3+) ions to a solution of L helps to generate a new fluorescence peak at 590 nm, due to the selective binding of Al(3+) ions with L in a 1 : 1 ratio with a binding constant (K) of 8.13 × 10(4) M(-1). The Schiff base L shows no cytotoxic effect, and it can therefore be employed for determining the intracellular concentration of Al(3+) and F(-) ions by 2 in living cells using fluorescence microscopy.

A new fluorogenic probe for the selective detection of carbon monoxide in aqueous medium based on Pd(0) mediated reaction.

A coumarin-based fluorogenic probe, PCO-1, senses carbon monoxide (CO) selectively in HEPES buffer at pH 8.0 through the intramolecular cyclization-elimination pathway based on Pd(0) mediated reaction. The probe exhibits a 'turn-on' response of CO over a variety of relevant reactive oxygen, nitrogen and sulfur species.