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Copper is essential for life, and beyond its well-established ability to serve as a tightly bound, redox-active active site cofactor for enzyme function, emerging data suggest that cellular copper also exists in labile pools, defined as loosely bound to low-molecular-weight ligands, which can regulate diverse transition metal signaling processes spanning neural communication and olfaction, lipolysis, rest-activity cycles, and kinase pathways critical for oncogenic signaling. To help decipher this growing biology, we report a first-generation ratiometric fluorescence resonance energy transfer (FRET) copper probe, FCP-1, for activity-based sensing of labile Cu(I) pools in live cells. FCP-1 links fluorescein and rhodamine dyes through a Tris[(2-pyridyl)methyl]amine bridge. Bioinspired Cu(I)-induced oxidative cleavage decreases FRET between fluorescein donor and rhodamine acceptor. FCP-1 responds to Cu(I) with high metal selectivity and oxidation-state specificity and facilitates ratiometric measurements that minimize potential interferences arising from variations in sample thickness, dye concentration, and light intensity. FCP-1 enables imaging of dynamic changes in labile Cu(I) pools in live cells in response to copper supplementation/depletion, differential expression of the copper importer CTR1, and redox stress induced by manipulating intracellular glutathione levels and reduced/oxidized glutathione (GSH/GSSG) ratios. FCP-1 imaging reveals a labile Cu(I) deficiency induced by oncogene-driven cellular transformation that promotes fluctuations in glutathione metabolism, where lower GSH/GSSG ratios decrease labile Cu(I) availability without affecting total copper levels. By connecting copper dysregulation and glutathione stress in cancer, this work provides a valuable starting point to study broader cross-talk between metal and redox pathways in health and disease with activity-based probes.

Super-resolution microscopy requires that subcellular structures are labeled with bright and photostable fluorophores, especially for live-cell imaging. Organic fluorophores may help here as they can yield more photons-by orders of magnitude-than fluorescent proteins. To achieve molecular specificity with organic fluorophores in live cells, self-labeling proteins are often used, with HaloTags and SNAP-tags being the most common. However, how these two different tagging systems compare with each other is unclear, especially for stimulated emission depletion (STED) microscopy, which is limited to a small repertoire of fluorophores in living cells. Herein, we compare the two labeling approaches in confocal and STED imaging using various proteins and two model systems. Strikingly, we find that the fluorescent signal can be up to 9-fold higher with HaloTags than with SNAP-tags when using far-red rhodamine derivatives. This result demonstrates that the labeling strategy matters and can greatly influence the duration of super-resolution imaging.

Piperazine appended Schiff base chemosensor (HL) (Z)-2,4-dibromo-6-(4-(piperazin-1-yl)but-1-en-1-yl)phenol, developed by a simple condensation of 3,5-dibromosalicylaldehyde and 2-aminoethyl piperazine, is successfully utilized to recognize Zn(II) and Cl− ions among several competitive cations and anions in 9 : 1 ethanol–water medium via turn on fluorescence. Interestingly, this chemosensor bears novel aggregation induced emission (AIE) properties in H2O–ethanol mixtures up to a ratio of 9 : 1, and the results obtained from dynamic light scattering (DLS), scanning electron microscopy (SEM), UV, and fluorescence spectroscopic studies help to confirm the presence of this property. With the help of this AIE activity, this probe has been used for selective detection of Cd (II) and Hg(II) via turn-on and off fluorescence, respectively, in a near aqueous medium. At the same time, in AIE active medium, the chemosensor can recognize picric acid also via turn-off fluorescence. All the sensing phenomena have been spectroscopically handled. In the presence of adenosine triphosphate (ATP)/AgNO3/Cl−, individual detection of the analyte is possible when four aforementioned analytes [Zn(II), Cd(II). Hg(II), Cl−] are present together in a solution. The moderately high host–guest binding constant values assure us about the chemosensor-analyte adduct formation, and the chemosensor-analyst binding mechanism is confirmed by IR and mass spectroscopy. The density functional theory (DFT) study gives the optimized structure of probe–analyte complexes. The on-site clear visual detection of the analytes in paper strips, along with AIE property, is shown by the investigated chemosensor. As a practical application, this chemosensor can notably track Zn(II) and Hg(II) in plant cells and HeLa cells, respectively. The detection of Hg(II) and Cd(II) is also possible in real water samples. [ABSTRACT FROM AUTHOR]

A novel fluorescent probe based on poly(N-isopropyl acrylamide) (p(NIPAAm-co-AAm)) immobilized carbon dots@SiO2 nanoparticles complex was synthesized for ferric iron detection through the chemical crosslinking methods, in which carbon dots@SiO2 nanoparticles complex was characterized by field emission scanning electron microscope, Fourier transform infrared spectroscopy, Ultraviolet–visible spectrophotometer and fluorescence spectrophotometer, respectively. The fluorescence quenching between p(NIPAAm-co-AAm)-CQDs and ferric iron were able to be controlled at different temperatures based on the swelling and shrinking of p(NIPAAm-co-AAm) through changing the temperature, which the principle of the probe was analyzed. The fluorescent probe could detect the ferric iron with a good linear relationship in the range of concentration from 0 to 50 μM and the limit of detection was 0.48 μM at 25 °C. [ABSTRACT FROM AUTHOR]

Five new lanthanide metal–organic frameworks (Ln-MOFs), namely {[Ln(L)]·Cl}n, [Ln = Pr(1), Nd(2), Eu(3), Ho(4), Ce(5)], based on a benzimidazole carboxylic acid ligand [H2L = 2-(2-carboxyphenyl)-1H-benzo[d]imidazole-6-carboxylic acid] were synthesized by a solvothermal method. Ln-MOFs 1–5 have the same two-dimensional layered structures. Interestingly, 1–5 exhibit excellent adsorption performance to anionic dye Congo red (CR), with adsorption capacities of 2724 mg g−1, 2719 mg g−1, 2718 mg g−1, 327 mg g−1, and 2273 mg g−1, respectively. Adsorption kinetics experiments showed that this kind of adsorption belonged to chemisorption; the hydrogen bonding and π–π interactions between the 1–5 host and CR guest molecules resulted in a high adsorption capacity. Luminescence and sensing experiments showed that 5 can be considered a promising multifunctional fluorescent sensor with good reusability and a high sensitivity toward Ag+ and Hg2+ ions, with detection limits of 1.7 × 10−7 and 2.5 × 10−6 M, respectively. [ABSTRACT FROM AUTHOR]

Mechanochromic materials alter their color in response to mechanical force and are useful for both fundamental studies and practical applications. Several approaches are used to render polymers mechanochromic, but they generally suffer from limitations in sensing range, capacity to provide quantitative information, and their capability to enable broad and simple implementation. Here, is it reported that these problems can be overcome by combining photonic structures, which alter their reflection upon deformation, with covalent mechanophores, whose spectral properties change upon mechanically induced bond scission, in hierarchically structured mechanochromic pigments. This is achieved by synthesizing microspheres consisting of an elastic polymer with spiropyran‐based cross‐links and non‐close‐packed silica nanoparticles. A strain of less than 1% can be detected in a shift of the reflection band from the photonic structure, while the onset strain for the conversion of the spiropyran into fluorescent merocyanine ranges from 30% to 70%, creating a broad strain detection range. The two responses are tailorable and synergistic, permitting the activation strain for the mechanophore response to be tuned. The mechano‐sensing photonic pigments are demonstrated to be readily incorporated into different polymeric materials of interest and quantitatively probe spatially heterogeneous deformations over a large strain range. [ABSTRACT FROM AUTHOR]

Aromatic isocyanides have gained a lot of attention lately as promising antifungal and anticancer drugs, as well as high-performance fluorescent analytical probes for the detection of toxic metals, such as mercury, even in vivo. Since this topic is relatively new and aromatic isocyanides possess unique photophysical properties, the understanding of structure–behavior relationships and the preparation of novel potentially biologically active derivatives are of paramount importance. Here, we report the photophysical characterization of 1,5-diisocyanonaphthalene (DIN) backed by quantum chemical calculations. It was discovered that DIN undergoes hydrolysis in certain solvents in the presence of oxonium ions. By the careful control of the reaction conditions for the first time, the nonsymmetric product 1-formamido-5-isocyanonaphthalene (ICNF) could be prepared. Contrary to expectations, the monoformamido derivative showed a significant solvatochromic behavior with a ~50 nm range from hexane to water. This behavior was explained by the enhanced H-bond-forming ability of the formamide group. The significance of the hydrolysis reaction is that the isocyano group is converted to formamide in living organisms. Therefore, ICNF could be a potential drug (for example, antifungal) and the reaction can be used as a model for the preparation of other nonsymmetric formamido–isocyanoarenes. In contrast to its relative 1-amino-5-iscyanonaphthalene (ICAN), ICNF is highly fluorescent in water, enabling the development of a fluorescent turnoff probe. [ABSTRACT FROM AUTHOR]

Breast cancer is the most prevalent diagnosed cancer among women and the main cause of morbidity and mortality. As for breast cancer, MCF-7 cells are an important candidate since they are widely utilized in research for estrogen receptor (ER)-positive breast cancer cell assays, and various sub-clones have been identified to reflect different classes of ER-positive tumors with varied levels of nuclear receptor expression. Rhodamines and its derivatives have shown a great interest over the past two decades due to their excellent structural and spectroscopic properties. Rhodamine derivatives have been widely investigated for their mitochondrial targeting and chemotherapeutic properties. Rhodamine derivatives, in particular, have been widely investigated for their therapeutic properties. In this regard, several studies have shown that rhodamine dye derivatives have promising in vitro and in vivo therapeutic efficacy. The present study deals with potential anticancer activity of few synthesized rhodamine derivatives against MCF-7 cell lines. [ABSTRACT FROM AUTHOR]

Photo-induced mode change of CO2 capture/release was achieved by a rationally designed system composed of spiropyran introduced into a polar-gradient field in the interlayer of montmorillonite. DFT calculations and CO2 adsorption tests demonstrated that spiropyran can interact with CO2 through not only weak physical interaction such as Coulombic or van der Waals interactions but also electronic interaction, while photo-isomerized merocyanine was in the CO2 release mode. Photo-induced CO2 concentration systems highly contribute to the realization of carbon neutrality, hence, this study could be a breakthrough for the world's environmental issues. [ABSTRACT FROM AUTHOR]

It is very challenging to fabricate a non-viral gene carrier system containing multifunctional components to overcome multiple extra- and intracellular barriers. Herein, we developed a novel PEGylated, targeted and fluorescence traceable multifunctional supramolecular host-guest gene vector system. This system was based on poly(β-cyclodextrin) (PCD), disulfide-containing azobenzene-terminated branched polymer (Az-ss-BPDM-RhB) with rhodamine-fluorescent functional groups and adamantyl terminated folate-modified PEG (Ad-PEG-FA). Transfection and cellular uptake data of the PEGylated supramolecular PCD/Az-ss-BPDM-RhB/DNA polyplexes demonstrated that prolonged incubation time to 24 h or longer could improve cell uptake and transfection efficiency of the PEGylated polyplexes. Good targeting and fluorescence traceable feature of this host-guest interaction gene delivery system was displayed. Moreover, the PEGylated and targeted supramolecular PCD/Az-ss-BPDM-RhB/Ad-PEG-FA showed lower cytotoxicity and in vivo zebrafish embryo toxicity and better gene transfection efficiency compared with the control 25 kDa PEI. Therefore, this PEGylated and targeted multifunctional supramolecular platform is a promising and effective gene delivery system for fluorescence traceable applications. [ABSTRACT FROM AUTHOR]

Titanium carbide quantum dots (Ti3C2 QDs) were synthesized by ammonia-assisted hydrothermal method. We also synthesized potassium permanganate (KMnO4)–functionalized Ti3C2 QDs (Mn-QDs) by modifying Ti3C2 nanosheets with KMnO4 and then cutting the functional nanosheets into Mn-QDs. The Ti3C2 QDs and Mn-QDs were characterized by fluorescence spectroscopy (FL), Fourier transform infrared spectroscopy (FTIR), UV–vis spectrophotometry (UV–vis), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). Furthermore, the modified Mn-QDs have strong luminescence ability and good dispersion stability, which can be used for Cr3+ and Hg2+ double ion detection with enhanced fluorescence specificity. Cr3+/Hg2+ and negatively charged Mn-QDs are bound together by electrostatic interactions. Meanwhile, the surface of Mn-QDs is rich in functional groups, which interacts with Cr3+/Hg2+ to modify the surface traps, leading to defect passivation and exhibiting photoluminescence enhancement. For the dynamic quenching produced by the interaction of Mn-QDs with Hg2+ within 50 μM, it may be caused by the complex formation of Hg2+ trapped by the amino group on the surface of Mn-QDs. The detection limits for Cr3+ and Hg2+ were 0.80 μM and 0.16 μM, respectively. The recoveries of Cr3+ and Hg2+ ions in real water samples were 93.79–105.10% and 93.91–102.05%, respectively, by standard addition recovery test. In this work, the application of Mn-QDs in Cr3+ and Hg2+ ion detection was researched, which opens a new way for its application in the field of detecting heavy metal ions. [ABSTRACT FROM AUTHOR]

A new bis-spirocyclic rhodamine B derivative was developed as a near-infrared colorimetric and "turn-on" fluorometric chemodosimeter (1) with a large Stokes shift (70 nm) for Cu2+. In response to Cu2+, the solution of 1 displayed major absorption at 700 nm, from colorless to blue within ten seconds. At the same time, emissions at 580 nm (excitation at 520 nm) and at 770 nm (excitation at 650 nm) were turned on. Good linear relationships between absorbance at 700 nm, fluorescence at 580 and 770 nm and concentration of Cu2+ in wide ranges were obtained in both colorimetric and fluorometric analyses, with the detection limits of 0.57 μM, 9 nM and 28 nM, respectively. Irreversible ring-opening processes of 1 coordinated with Cu2+, followed by hydrolysis as well as acylated reaction were proposed. Furthermore, 1 was applied to image Cu2+ in HepG2 living cells and within the mitochondria of the cells in the roots of paulownia sprouts. [ABSTRACT FROM AUTHOR]

A novel photocatalytic process using a modification of photo-Fenton reaction, with sodium percarbonate (SP), as an alternative source of H2O2, and alloy Al65Cu20Fe15 containing, among others, quasicrystals (of the percentage composition Al65Cu20Fe15), being a source of iron ions, effectively decolourizes the aqueous solution of rhodamine B (RB; solution of 5 mg/l). The source of UV radiation was a lamp with a power of 36 W. The experiments were carried out at pH = 7 and reaction time (from 5 to 60 min). The increase in SP concentration (in the range of 8.3 to 33.3 g/l) significantly increased the degree of degradation of RB and the reaction rate. However, the use of quasicrystals, in the range of 8.3 to 33.3 g/l, was also important in the modified photocatalytic photo-Fenton process. The best degradation effects of RB (95%) were obtained for the highest SP concentration of 33.3 g/l and the lowest quasicrystal concentration of 8.3 g/l. On the other hand, visual decolourization of RB was obtained with an efficiency of 70% for SP and quasicrystal concentrations of 16.7 g/l and 16.7 g/l, respectively, after 45 minutes, and for SP and quasicrystal concentrations of 33.3 g/l and 8.3 g/l, respectively, after the time of 20 minutes. The best RB degradation effects in the comparative method (UV/Na2CO3·1.5H2O2 without the addition of quasicrystals) were only 52.7%. The obtained results encourage further research to optimize the conditions of the proposed method and to investigate its applicability to other types of dyes and pollutants. [ABSTRACT FROM AUTHOR]

Photochromic molecules can transform from colorless closed to colored open forms by coordination with metal ions. Interaction of photochromic 1,3,3-trimethylindolino-β-naphthopyrylospiran (TMI-NPS) with manganese(II) hexafluoroacetylacetonate in o-dichlorobenzene results in the formation of deep red-violet solution indicating a coordination-induced transition from closed to colored open form. Precipitation of crystals yields {MnII(hfac)2·(μ2-TMI-NPS)}2 dimers (1) in which two Mn(II) atoms of hexafluoroacetylacetonate are bridged by oxygen atoms of two TMI-NPS ligands in the open form. Magnetic studies show a weak ferromagnetic exchange between MnII spins through oxygen atoms of TMI-NPS with estimated exchange interaction (J) of +1.07 cm−1. A positive Weiss temperature of +8 K also supports ferromagnetic coupling. As a result, MnII spins arrange parallel to each other at 2 K, and correspondingly, these dimers transfer to a high spin (S = 5) state. DFT calculations support noticeable mixing of the metal and ligand orbitals and essential positive charge on the TMI-NPS ligands, which can provide ferromagnetic exchange between MnII spins. [ABSTRACT FROM AUTHOR]

Mechanochromic polymers that exhibit multiple color changes under external mechanical stimulation show great potential for sensor applications. Herein, an epoxy thermoset that can reveal the intensity, type, and duration of mechanical stimulation via a combination of disulfide (DS) and rhodamine (Rh) mechanochromophores is reported. A unique multicolor transition occurs upon ball mill or manual grinding because of the different activation energies of DS and Rh. The epoxy changes color depending on the ball mill grinding duration. Simultaneous activation occurs with a mechanochromic time lag between DS and Rh, and the collision energy strongly affects the relative intensity. A more dramatic multicolor response is observed using a mortar and pestle, as sequential activation occurs upon gentle and strong grinding. Various types of mechanical stimulation can cause different aggregates of the activated Rh moiety and vary the relative mechanosensitivities of Rh and DS, which lead to a different color response. [ABSTRACT FROM AUTHOR]

The development of live-cell fluorescence nanoscopy is powered by the availability of suitable fluorescent probes. Rhodamines are among the best fluorophores for labeling intracellular structures. Isomeric tuning is a powerful method for optimizing the biocompatibility of rhodamine-containing probes without affecting their spectral properties. An efficient synthesis pathway for 4-carboxyrhodamines is still lacking. We present a facile protecting-group-free 4-carboxyrhodamines' synthesis based on the nucleophilic addition of lithium dicarboxybenzenide to the corresponding xanthone. This approach drastically reduces the number of synthesis steps, expands the achievable structural diversity, increases overall yields and permits gram-scale synthesis of the dyes. We synthesize a wide range of symmetrical and unsymmetrical 4-carboxyrhodamines covering the whole visible spectrum and target them to multiple structures in living cells – microtubules, DNA, actin, mitochondria, lysosomes, Halo-tagged and SNAP-tagged proteins. The enhanced permeability fluorescent probes operate at submicromolar concentrations, allowing high-contrast STED and confocal microscopy of living cells and tissues. Rhodamines are privileged fluorescent dyes for labelling intracellular structures in living cells. Here, the authors present a facile protecting-group-free synthesis permitting generation of a wide range of symmetrical and unsymmetrical 4-carboxyrhodamines covering the whole visible spectrum. [ABSTRACT FROM AUTHOR]

Tracers for bimodal optical imaging and positron emission tomography unite multiple advantages in a single molecule. Their tumor-specific uptake can be visualized after their PET activation by radiofluorination via PET/CT or PET/MRI allowing for staging or therapy planning, while their non-radioactive moiety additionally facilitates the visualization of malignant tissue during intraoperative fluorescence-guided surgery or in histological assessments. The silicon-bridged xanthene core offers the opportunity for radiofluorination with SiFA isotope exchange to obtain a small-molecule, PET-activatable NIR dye that can be linked to different target vectors. Herein, we demonstrate for the first time the PET-activation of a fluorinated silicon pyronine, belonging to a class of low-molecular-weight fluorescence dyes with a large Stokes shift (up to 129 nm) and solvent-dependent NIR dye properties, with a successful radiochemical conversion of 70%. The non-fluorinated pyronine precursor is easily accessible by a three-step sequence from commercially starting material with a 12% overall yield. Moreover, a library of seven unusually functionalized (by approximately 15 nm), red-shifted silicon rhodamines were synthesized in three- to four-step sequences and the optical properties of the novel dyes were characterized. It was also shown that the synthesized silicon rhodamine dyes can be easily conjugated by amide bond formation or 'click-reaction' approaches. [ABSTRACT FROM AUTHOR]

A rhodamine B derivative containing a terminal (4-hydroxybenzyl)triphenylphosphonium chloride substituent was synthesized. Its structure was determined using IR, 1H NMR, and 13C NMR spectroscopy. The spectral luminescent properties of the compound obtained and its complex formation in solutions with Co2+, Cu2+, Ni2+, and Zn2+ cations were studied. These ions are responsible for a contrasting ionochromic naked-eye effect with the crimson-red coloration of a colorless solution due to the isomerization of the rhodamine spirolactam form into an open form. The process is accompanied by the appearance of fluorescence in the region of 560–600 nm. The complex with zinc(II) cation exhibits particularly intensive emission, which gives the properties of a highly sensitive and effective chemosensor for Zn2+ ions to the obtained rhodamine. [ABSTRACT FROM AUTHOR]

Carbon dots (CDs) have excellent fluorescence properties and can be used in many research fields. In this paper, carbon dots were prepared by microwave-assisted pyrolysis of citric acid and urea, characterized by transmission electron microscope (TEM), X-ray diffractometer (XRD), 13C-NMR spectrum, zeta potential, Fourier transform infrared spectroscopy (FT-IR), ultraviolet–visible (UV–vis) absorption and fluorescence spectra, and detected the Hg2+ and ascorbic acid (AA) sequentially. It showed that carbon dots were hollow, spherical particles and less than 10 nm, photoluminescence quantum yield of carbon dots was about 15%. The CDs were selective and sensitive to Hg2+ and AA based on the "on–off-on" fluorescence behavior. The detection limits of CDs for Hg2+ and AA were 0.138 μM and 0.212 μM, respectively. Fluorescence response mechanism of CDs was also discussed. [ABSTRACT FROM AUTHOR]

The development of fluorometric detection methods for toxic metal ions in real samples and inside cellular environments using fluorescent dyes has gained tremendous research interest. This work represents the design and synthesis of a 1,8-naphthalimide-based visible light absorbing fluorescence probe His-NMI-Bu showing an intramolecular charge transfer (ICT) feature. Photophysical properties of the fluoroprobe are investigated in-depth through a combination of steady-state, time-resolved spectroscopic techniques, and DFT calculation. The probe displays outstanding pH tolerance in the pH range of 5–10 as evident from UV–Vis. and fluorescence measurements. The fluoroprobe exhibits chelation with Hg2+-induced fluorescence attenuation via PET in the solution, thus acting as a suitable fluorescence sensor for mercury ions with LOD 0.52 µM. The high sensitivity and selectivity of the probe towards Hg2+ are validated from fluorescence titration with various metal ions. Banking on its intriguing solid-state emissive properties, dye-loaded filter paper-based sensing of Hg2+ is also developed demonstrating the sensitivity in the micromolar range. Finally, His-NMI-Bu fluorophore depicts its selective localization inside the lysosomal compartment of live cells which assists further to monitor the presence of mercury ions inside the lysosome showing similar Hg2+-induced fluorescence depletion. [ABSTRACT FROM AUTHOR]

In this study, a rapid fluorescent and colorimetric dual-mode detection strategy for Hg2+ in seafoods was developed based on the cyclic binding of the organic fluorescent dye rhodamine 6G hydrazide (R6GH) to Hg2+. The luminescence properties of the fluorescent R6GH probe in different systems were investigated in detail. Based on the UV and fluorescence spectra, it was determined that the R6GH has good fluorescence intensity in acetonitrile and good selective recognition of Hg2+. Under optimal conditions, the R6GH fluorescent probe showed a good linear response to Hg2+ (R2 = 0.9888) in the range of 0–5 μM with a low detection limit of 2.5 × 10−2 μM (S/N = 3). A paper-based sensing strategy based on fluorescence and colorimetric analysis was developed for the visualization and semiquantitative analysis of Hg2+ in seafoods. The LAB values of the paper-based sensor impregnated with the R6GH probe solution showed good linearity (R2 = 0.9875) with Hg2+ concentration in the range of 0–50 μM, which means that the sensing paper can be combined with smart devices to provide reliable and efficient Hg2+ detection. [ABSTRACT FROM AUTHOR]

• A new xanthene-based Schiff base probe was synthesized and utilized for highly selective and sensitive quantification of Hg2+. • A smartphone technique was quickly applied to analyze Hg2+ in real samples with good recovery rates. • 3-Dimensional geometries and the electronic properties of the probe and (3), 3-Hg and hydrolysis product were explained by DFT calculations. • The probe exhibited a high potential for Hg2+ sensing on adenocarcinoma alveolar basal epithelial (A549) cancer cells. In this study, a Schiff base-based probe, named as 2-((methyl benzoate-4-yl)methyleneamino)-3′,6′-bis(diethylamino)spiro[isoindoline-1,9′-xanthene]-3-one (2), was successfully synthesized and characterized by various spectral techniques besides single-crystal x-ray diffraction. The investigation was focused on the analyzing the selectivity of the probe towards some common metal ions. The study was conducted in an aqueous medium, and the results indicated that the probe showed high selectivity towards the Hg2+ ion. The utilization of mass analysis revealed that the optical emission originating from rhodamine ethyl ester can be generated through the spirolactam ring/Schiff base hydrolysis facilitated by the Hg2+ ion. The Limit of Detection (LOD) for the Hg2+ ions by colorimetry and fluorometry were determined to be 3.0 × 10-8 M and 9.4 × 10-9 M, respectively. A technique using a smartphone was quickly applied to analyze Hg2+ in real samples with good recovery rates (96.5%-101.5%). To explain their 3-dimensional geometries and the electronic properties, the DFT calculations were also performed on 2, its spiro bond opened Hg-complex (3-Hg), Hg2+ uncomplexed product (3) and the rhodamine ethyl ester hydrolysis product. Moreover, mercury detection potency of the probe at the cellular level was investigated on adenocarcinoma alveolar basal epithelial (A549) cancer cells, and the result showed that the probe exhibits high potential for living cell imaging. [Display omitted] [ABSTRACT FROM AUTHOR]

In this work, a porphyrin metalation-based ratiometric absorbance and fluorescence dual model immunoassay was proposed to detect ochratoxin A (OTA). 5,10,15,20-tetrakis(1-methyl-4-pyridinio) porphyrin (TMPyP) was pink and had a strong fluorescence, upon coordination with Hg(II), its fluorescence was quenched and the color became green. The alkaline phosphatase can catalyze the dephosphorylation of ascorbic acid 2-phosphate to produce ascorbic acid, which can reduce the coordinated Hg(II) to Hg(0) and then dissociated from TMPyP, its fluorescence was recovered. Meanwhile, the color changed from green to light pink, which can be identified by naked eye for semi-quantitative detection. The linear ranges of ratiometric absorbance and fluorescence model were 0–6.0 ng/mL and 0.1–6.0 ng/mL, respectively. The absorbance and fluorescence signals produced by porphyrin metalation can mutually verify to improve the accuracy of detection results. Besides, the ultra-sensitivity and high selectivity demonstrated this method was a powerful tool for trace OTA detection. • The porphyrin metalation was combined with immune recognition to detect OTA. • The ratiometric absorption and fluorescence dual-mode can improve the accuracy. • The green to pink color change can be used for naked eye semi-quantitative detection. • Ratiometric dual-mode produced wider linear range than that of Ic-ELISA. [ABSTRACT FROM AUTHOR]

In this project, a sensitive fluorescent aptasensor was fabricated to detect lead ions (Pb2+) by applying hollow gold nanoparticles (HGNPs) as a nano-carrier and rhodamine B (RDB) fluorescent dye as the signal agent. In the aptasensor that was created, the specific attachment of the aptamers to Pb2+ ions led to the release of aptamer from the chitosan (CTS) coated-HGNPs loaded with RDB, causing an increase in fluorescence intensity due to the leakage of RDB. The method demonstrated specific detection of the target analyte, achieving a detection limit (LOD) of 1 ppb and a broad linear dynamic range spanning from 2 to 1000 ppb. The aptasensor was able to accurately measure the concentration of Pb2+ in human serum, low-fat milk, and mineral water samples. The suggested biosensor, which offers the benefits of simplicity, user-friendliness, affordability, and high sensitivity, is well-suited for use with complex samples such as environmental and clinical samples. [Display omitted] • A fluorescent aptasensor was developed to detect Pb2+ ions by applying HGNPs and RDB. • HGNPs with a high capacity for RDB loading and RDB as the signal indicator. • The designed HGNPs-based fluorescent aptasensor exhibited a detection limit of 1 ppb. • The aptasensing method demonstrated specific detection of the target analyte. • The sensor was able to accurately measure the concentration of Pb2+ in milk samples. [ABSTRACT FROM AUTHOR]

[Display omitted] • Probes based on polycyclic aromatic hydrocarbons and rhodamine 6G for heavy metals. • Rhodamine 6G-phenanthrene probe with a detection limit of 0.84 nmol/L for Hg(II). • Rhodamine 6G-acenaphthene probe with a detection limit of 0.31 nmol/L for Cu(II). • Solid-phase sensor with excellent reproducibility and fluorescence "on/off" response. • Fluorescence detection of Hg(II) in living cells by rhodamine 6G-phenanthrene probe. Four rhodamine 6G-PAH probes with pyrene (R6G-Pyr), anthracene (R6G-Ant), acenaphthene (R6G-Acp) or phenanthrene (R6G-PA) as fluorophore were designed and synthesized for Hg(II) detection. Probe R6G-PA , which had the lowest detection limit of 0.84 nmol/L, displayed the best fluorescence performance as compared to the other three probes. This type of probe had good anti-interference properties against most common metal ions except Cu(II). Metal Cu(II) had a certain quenching effect on the fluorescence generated by Hg(II), with a minimum detection limit of 0.31 nmol/L (for R6G-Acp), indicating its potential practicability for Cu(II) detection. The structure-fluorescence relationship was discussed based on density functional theory (DFT) calculations, and R6G-PA + Hg(II), which had the minimum dihedral angle between polycyclic aromatic rings and rhodamine spiro ring, produced the strongest π-π accumulation and provided the brightest fluorescence. Probe R6G-PA was successfully employed for fluorescence detection of Hg(II) in biological samples. Its solid-phase sensor PS@R6G-PA was developed by immobilizing R6G-PA on PS microspheres for the determination of Hg(II) in water and food samples, with excellent reproducibility and fluorescence "on/off" response. The relative error of the spiked recovery rate was less than 10 %. [ABSTRACT FROM AUTHOR]

Fluorescent pyrene-based polymer organic frameworks (POFs) PY-POFs were designed and synthesized by a facile solvothermal route for glucose detection, employing melamine, aromatic dialdehydes, 1-pyrenecarboxaldehyde, and phenylboronic acid as building blocks. The structure and photophysical properties of as-prepared POFs were systematically characterized via Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy, N 2 adsorption isotherms and fluorescence spectroscopy. The PY-POFs possessed intrinsic microporosity derived from extensively interlinked aminal structures, boasting specific surface areas reaching 192 m²/g, pore volumes extending to 0.8079 cm³/g, pore diameters of up to 17 nm, and an average particle dimension of ∼ 31 nm. In addition, the PY-POFs exhibited a dual-wavelength emission of pyrene excimer (λ em = 472 nm) and monomer (λ em = 382, 400, and 422 nm). When exposed to glucose, the former emission decreased while the latter increased, corresponding to the conformational transition of pyrene molecule from excimer to monomer. The non-enzymatic ratiometric fluorescent sensor displayed remarkable sensitivity towards glucose within 10−200 μM range, with a limit of detection (LOD) of 5.6 µM. Moreover, the glucose detection ability of PY-POFs was also in vivo demonstrated within zebrafish. Application of this sensor to real samples such as human saliva and DMEM biological matrix presented satisfactory results and good reproducibility. These results indicate that the fluorescent glucose sensor PY-POFs have broader prospects for utilization within biological studies. [Display omitted] • The successful preparation of pyrene-functionalized ratiomatric polymer organic frameworks. • Selective ratiometric fluorogenic response of PY-POFs for glucose sensing. • In vivo imaging using fluorogenic response of PY-POFs. • Non-enzymatic glucose detection by chemosensor PY-POFs. [ABSTRACT FROM AUTHOR]

• A TPE-functionalized rhodamine chemdosimeter TRP has been synthesized with an AIE effect. • TRP shows ratiometric fluorescence to Hg2+ with high selectivity and well-resolved emission bands. • The LOD of Hg2+ is low down to 10.0 nM. • TRP can be used for tracing intracellular Hg2+ by ratiometric fluorescence imaging. In this work, a tetraphenyl ethylene functionalized rhodamine chemodosimeter, namely, TRP, has been designed, built, and structurally determined. The chemodosimeter exhibited an AIE effect in an EtOH-H 2 O mixture with the maximal emission intensity at 463 nm at a water fraction of 70 %. Then TRP was applied for ratiometric monitoring of Hg2+ ions in EtOH/H 2 O solution (v/ v = 3/7), presenting about a 35-fold fluorescence intensity ratio enhancement (F 649 /F 463), visible color changes, and well-resolved emission bands (187 nm). In addition, TRP showed high selectivity and sensitivity in Hg2+ ions sensing and achieved a limit of detection (LOD) of 10.0 nM, which was mainly attributed to the production of an oxadiazole functionalized and spirolactam ring opened rhodamine derivative-induced by Hg2+ ions. Significantly, using TRP as a tracer, ratiometric fluorescent detection of Hg2+ ion has been successfully conducted via living cell imaging, demonstrating its potential for practical applications in biological systems. We developed a chemodosimeter with AIE effect for selectivity, sensitive and ratiometeric sensing Hg2+ ions in vitro and in vivo. [Display omitted] [ABSTRACT FROM AUTHOR]

A sensitive photoluminescence turn-off Hg(II) sensor based on ethylenediamine-functionalized carbon dots (CDs/en) fabricated using wastepaper and ethylenediamine via a facile two-step synthesis process. A quantum yield (QY) obtained is 16.2 % with maximum emission at 446 nm. The CDs/en acted as the blue fluorescent probe accompanied by strong quenching of the fluorescence emission with Hg(II) at pH 6. The amino or oxygen groups on the CDs/en allow electron transfer to Hg(II), leading to fluorescence quenching. Under the optimal condition, the proposed sensor was applied to detect Hg(II) in the linear range of 1–20 nM. A detection limit of 0.16 nM is achieved using fluorescence spectroscopy and 0.72 nM by monitoring the absorbance variation at 274 nm. The successful real sample analysis and "EXIT" signs made of fluorescent sand also paved the way for the best optical sensor. Based on the bi-mode signals, a "NAND" logic gate was constructed effectively. [Display omitted] • Ethylenediamine-functionalized carbon dots (CDs/en) were prepared in a two-step hydrothermal method. • CDs/en exhibited high selectivity and sensitivity for the fluorescence and absorbance detection of Hg(II). • Quenching of fluorescence of CDs/en with Hg(II) via PET mechanism. • The CDs/en detects Hg(II) concentration from 1 to 20 nM with a detection limit of 0.16 nM. • Practical performance of the sensor monitored through real sample analysis, "EXIT" signs of fluorescent sand, and "NAND" logic gate. [ABSTRACT FROM AUTHOR]

[Display omitted] • FS-Hg-1 determined mercury ions rapidly with sterling selectivity and sensitivity. • High specificity of FS-Hg-1 effectively eliminated interference from most ions. • In contrast, FS-Hg-1 demonstrates strong visualization effects. • Satisfactory results were conducted with the excellent confidence interval. Mercury, one of the various harmful metals, is particularly significant in affecting aquatic organisms, currently gaining more attentions and sparking discussions. In response to the limitations of traditional detections, fluorescent probes have emerged as a promising solution with some advantages, such as weaker background interference, shorter processing time, higher accuracy. Thus, a novel fluorescent probe, FS-Hg-1 , has been developed for assessing mercury ion (Hg2+) concentrations in aquatic products. This probe displays specific recognition of mercury ions in fluorescence spectra. Notably, FS-Hg-1 exhibits a distinct color change to pink when combined with Hg2+ (with a 948-fold increase in absorption at 568 nm) and a substantial fluorescence change towards Hg2+ (361-fold increase, excitation at 562 nm, emission at 594 nm) in N, N-dimethylformamide. The probe boasts a detection limit of 0.14 μM and rapid reaction with Hg2+ within 10 s, showing an excellent linear correlation with [Hg2+] in the range of 0 to 10 μM. Through thorough analysis using FS-Hg-1 , the results align with those from the standard method (P > 0.05), with spiked recovery rates ranging from 108.4% to 113.2%. With its precise recognition, low detection limit, and remarkable sensitivity, this fluorescent assay proves effective in mercury concentration determination in aquatic samples without interference. The potential of FS-Hg-1 is promising for speedy detection of residual Hg2+ and holds significance in ensuring food safety. [ABSTRACT FROM AUTHOR]

[Display omitted] • The AXS probe can rapidly detect Zn2+ by near-infrared fluorescence. • Smartphone and fluorescent dual-model detection were achieved. • Qualitative and quantitative determination of Zn2+ in common foodstuffs. • Successful applications for bioimaging in Caenorhabditis elegans and mice. Zn2+ plays a vital role in regulating various life processes, such as gene expression, cell signaling, and brain function. In this study, a near-infrared fluorescent probe AXS was synthesized to detect Zn2+ with good fluorescence specificity, high selectivity, and high sensitivity; the detection limit of Zn2+ was 6.924 × 10−11 M. The mechanism of Zn2+ recognition by the AXS probe was investigated by 1H nuclear magnetic resonance titrations, UV–visible spectroscopy, fluorescence spectroscopy, Fourier-transform infrared spectroscopy, and high-resolution mass spectrometry. Test paper experiments showed that the AXS probe could detect Zn2+ in real samples. In addition, quantitative and qualitative detection of Zn2+ in common foodstuffs was achieved. For portable Zn2+ detection, a smartphone detection platform was also developed based on the AXS probe. Importantly, the AXS probe showed good bioimaging capabilities in Caenorhabditis elegans and mice. [ABSTRACT FROM AUTHOR]

Human serum albumin (HSA) levels in the body are crucial for the accurate diagnosis of various health issues, necessitating continuous monitoring and novel detection methods. This study focused on the development and synthesis of two novel D-π-A small molecule near-infrared fluorescent probes, PTPA-B and CPTPA-B. The probes demonstrated selective detection of HSA with a rapid response time of 1 min and high sensitivity, featuring limits of detection (LOD) of 0.102 μM and 1.702 μM. Under physiological conditions, the intrinsic fluorescence of these probes is minimal due to intramolecular charge transfer (TICT). Upon entering the hydrophobic cavity of HSA, the probes exhibit red fluorescence by inhibiting the TICT process. Additionally, the probes exhibited enhanced biocompatibility in living cells and enabled fluorescence imaging of L-02 live cells. Therefore, the PTPA-B fluorescent probe serves as an effective tool for serum detection, revealing its potential applications in live cell imaging and precise clinical diagnosis. • Designed and synthesized two novel D-π-A near-infrared fluorescent probes with high selectivity and sensitivity for HSA detection. • The probes provide rapid HSA detection with a 1-min response time and low detection limits (0.102 μM for PTPA-B and 1.702 μM for CPTPA-B). • The probes are effective in live cell imaging, offering enhanced biocompatibility and potential for clinical diagnostics. [ABSTRACT FROM AUTHOR]

Hypochlorous acid (HClO) serves as a critical biomarker in inflammatory diseases such as rheumatoid arthritis (RA), and its real-time imaging is essential for understanding its biological functions. In this study, we designed and synthesized a novel probe, RHMB , which ingeniously integrates rhodamine B and methylene blue fluorophores with HClO-specific responsive moieties into a single molecular framework. Upon exposure to HClO, RHMB exhibited significant dual-channel fluorescence enhancement characterized by high sensitivity (LODs of 2.55 nM and 14.08 nM), excellent selectivity, and rapid response time (within 5 s). Notably, RHMB enabled reliable imaging of both exogenous and endogenous HClO in living cells and in zebrafish, employing a unique duplex-imaging turn-on approach that highlighted its adaptability across various biological contexts. Furthermore, RHMB effectively monitored HClO fluctuations in an RA mouse model and assessed the therapeutic efficacy of diclofenac (Dic) in alleviating RA symptoms. These findings underscore the potential of RHMB as an invaluable tool for elucidating the biological roles of HClO in various diseases. [Display omitted] • A NIR dual-channel fluorescent probe called RHMB is developed for HClO imaging. • RHMB has high sensitivity and selectivity for the detection of HClO in vitro. • Realized in vivo imaging of HClO level fluctuations in cells and zebrafish. • Evaluated diclofenac's efficacy in RA mice via duplex-imaging mode. [ABSTRACT FROM AUTHOR]

[Display omitted] • The fluorescent skeletons were constructed by triphenylamine composed the electron-withdrawing nitrogen-containing. • The fluorescence sensors were designed to detect the human serum albumin (HSA). • The sensors were explored to be able to efficiently bind the IB structural domain of HSA. • The sensor had a good meaningful of avoiding the interference of commonly drugs in clinical medicine and artificial urine. Serum albumin is the most abundant protein in mammalian plasma. It occupies an extremely important position in organisms as an early indicator of the development of many diseases. The development of fluorescence sensing technology has revolutionized the drawbacks of traditional methods. In this strategy, we designed and synthesized three dual fluorophore organic sensors TPA-IPA-T1, TPA-QL-T2, and TPA-Py-T3 for the detection of serum albumin. The rotation of the C–C bond of sensors is restricted and the molecular structure forms a rigid plane that contributes to the fluorescent emission intensity of the sensor. The fluorescent skeletons were successfully constructed by triphenylamine composed the electron-withdrawing nitrogen-containing compounds benzopyrrole (indole), benzopyridine (quinoline), and pyridine, respectively, with piperazine as a rigid connecting bridge. The addition of human serum albumin (HSA) turned on the fluorescent emission of the sensor near 580–600 nm. The color of the sensor solution changed from colorless to pink and bright orange, respectively. The fluorescent intensity increased by 24, 67, and 31 fold, respectively. The sensors have the advantages of sensitivity and fast response, strong anti-interference ability, low detection limit and good water solubility. Drug experiments in artificial urine demonstrate the characteristics of sensors, which has a very high potential for biological feasibility and medical applications. The sensors facilitaty the binding of the HSA through electrostatic interactions. The sensors were explored to be able to efficiently bind the IB structural domain of HSA, which had a good meaningful of avoiding the interference of commonly drugs in clinical medicine and in artificial urine on the detection of HSA. [ABSTRACT FROM AUTHOR]

Although protein synthesis is a conserved and essential cellular function, it is often regulated in a cell-type-specific manner to influence cell fate, growth and homeostasis. Most methods used to measure protein synthesis depend on metabolically labeling large numbers of cells with radiolabeled amino acids or amino acid analogs. Because these methods typically depend on specialized growth conditions, they have been largely restricted to yeast, bacteria and cell lines. Application of these techniques to investigating protein synthesis within mammalian systems in vivo has been challenging. The synthesis of O-propargyl-puromycin (OP-Puro), an analog of puromycin that contains a terminal alkyne group, has facilitated the quantification of protein synthesis within individual cells in vivo. OP-Puro enters the acceptor site of ribosomes and incorporates into nascent polypeptide chains. Incorporated OP-Puro can be detected through a click-chemistry reaction that links it to a fluorescently tagged azide molecule. In this protocol, we describe how to administer OP-Puro to mice, obtain cells of interest (here, we use bone marrow cells) just 1 h later, and quantify the amount of protein synthesized per hour by flow cytometry on the basis of OP-Puro incorporation. We have used this approach to show that hematopoietic stem cells (HSCs) exhibit an unusually low rate of protein synthesis relative to other hematopoietic cells, and it can be easily adapted to quantify cell-type-specific rates of protein synthesis across diverse mammalian tissues in vivo. Measurement of protein synthesis within bone marrow cells in a cohort of six mice can be achieved in 8-10 h.

Proteins possess a complex and dynamic structure, which is influenced by external signals and may change as they perform their biological functions. We present an optical approach, distance-encoding photoinduced electron transfer (DEPET), capable of the simultaneous study of protein structure and function. An alternative to FRET-based methods, DEPET is based on the quenching of small conjugated fluorophores by photoinduced electron transfer: a reaction that requires contact of the excited fluorophore with a suitable electron donor. This property allows DEPET to exhibit exceptional spatial and temporal resolution capabilities in the range pertinent to protein conformational change. We report the first implementation of DEPET on human large-conductance K+ (BK) channels under voltage clamp. We describe conformational rearrangements underpinning BK channel sensitivity to electrical excitation, in conducting channels expressed in living cells. Finally, we validate DEPET in synthetic peptide length standards, to evaluate its accuracy in measuring sub- and near-nanometer intramolecular distances.

New high-throughput assay formats and innovative screening technologies are needed for miniaturized screens using small quantities of near-native, patient-derived cells. Here, we developed a hollow micropillar array method to screen compounds using epithelial cells cultured on a porous support, with the goal of screening thousands of compounds using a single 24 mm diameter transwell filter containing cultured cells. Test compounds (∼1 nL) in an alginate hydrogel were printed by microinjection in hollow cylindrical micropillars (height = 150 μm, inner diameter = 100 μm) spaced 300 μm apart in a square array configuration. Compounds were delivered by positioning the array near the surface of a cell layer, with 5-10 μm of distance between the micropillars and cell surface. Micropillar array geometry, and the viscosity of the hydrogel and overlying solutions, were optimized computationally and experimentally to produce sustained exposure of cells to test compounds with minimal cross-talk from compounds in neighboring micropillar wells. The method was implemented using a 10 × 10 micropillar array (size = 3 × 3 mm) on CFTR-expressing epithelial cells, in which CFTR chloride channel function was measured from fluorescence in response to iodide addition using a genetically encoded cytoplasmic yellow fluorescent protein halide indicator. The hollow micropillar array platform developed here should be generally applicable for high-capacity drug screening using small numbers of cells cultured on solid or porous supports.

An effect of Rhodamine 6G dye introduced into vinylidenefluoride and tetrafluoroethylene copolymer on a number of its structural and electrical characteristics has been detected. It was shown that at film crystallization, the inserted dopant shifts the equilibrium distribution of isomers to the side of increasing concentrations of chains with the conformation of a planar zigzag. The dye introduced strongly increases ac conductivity, especially at high electric fields. The investigation of high voltage polarization under bipolar external field conditions shows slow switching of gigantic current which is observed at fields lower than coercive ones. The estimation of the charge density indicates the non-ferroelectric nature of the phenomenon observed. The analysis of the data shows that in the system, Maxwell–Wagner relaxation processes take place, which lead to the space charge formation in the polymer matrix. It is established that current switching observed must be attributed to the relaxation of the space charge field. [ABSTRACT FROM AUTHOR]

For the first time a pyrrolidinofullerene salt containing a spiropyran group and an ammonium group, capable of reversibly reacting to UV radiation, has been synthesized. Photoinduced reactions of the synthesized compounds were studied using absorption and luminescence spectroscopies, spectral and kinetic characteristics were measured. The hybrid molecule was found to exhibit intrinsic fluorescence even in the spirocyclic form. The C60 derivative showed a higher stability and better spectral and luminescent properties than the precursor. [ABSTRACT FROM AUTHOR]

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

It is highly desirable to develop high-performance ratiometric fluorescent probes for SO2 derivative detection and realize their application in biological imaging. In this study, we report the rational design of a novel negative photochromic spiropyran derivative, spiro[azahomoadamantane-pyran] (MAHD-SP), with notable orange fluorescence in its stable ring-opened state without UV regulation. The unsaturated double bond of MAHD-SP underwent the Michael addition reaction of the SO2 derivative, making the fluorescence quenching of MAHD-SP obvious. Then, MAHD-SP, a fluorescent conjugated polymer PFO and a polymeric surfactant PEO113-b-PS49 were used to construct a ratiometric fluorescent polymeric nanoprobe (RFPN) via a coprecipitation method. The probe exhibited high sensitivity and selectivity for the ratiometric detection of SO2 derivatives in pure aqueous solutions. Moreover, the good biocompatibility of RFPN can be used to visualize exogenous and endogenous SO2 derivative generation in living cells. [ABSTRACT FROM AUTHOR]

We designed a rhodamine B‐based colorimetric chemosensor BHSO ((Z)‐3′,6′‐bis(diethylamino)‐2‐(2‐(((8‐hydroxy‐2,3,6,7‐tetrahydro‐1H,5H‐pyrido[3,2,1‐ij]quinolin‐9‐yl)methylene)amino)ethyl)spiro[isoindoline‐1,9′‐xanthen]‐3‐one) for detecting Cu2+. In the presence of Cu2+, BHSO caused a colour variation from colourless to bright orange. The limit of detection for Cu2+ towards BHSO was 0.73 μM. The binding of BHSO to Cu2+ was analysed as a 1:1 ratio through a Job plot and electrospray ionisation mass spectrometry. BHSO can detect readily Cu2+ with a test strip by colorimetric variation. The detecting process of Cu2+ by BHSO was represented by ultraviolet‐visible titration, electrospray ionisation mass spectrometry, proton nuclear magnetic resonance titration, Job plot and density functional theory calculations. [ABSTRACT FROM AUTHOR]

Biorthogonal labelling with fluorescent small molecules is an indispensable tool for diagnostic and biomedical applications. In dye‐based 5‐ethynyl‐2′‐deoxyuridine (EdU) cell proliferation assays, augmentation of the fluorescent signal entails an overall enhancement in the sensitivity and quality of the method. To this end, a rapid, divergent synthetic procedure that provides ready‐to‐click pH‐insensitive rhodamine dyes exhibiting outstanding brightness was established. Compared to the shortest available synthesis of related high quantum‐yielding rhodamines, two fewer synthetic steps are required. In a head‐to‐head imaging comparison involving copper(I)‐catalyzed azide alkyne cycloaddition reactions with in vitro administered EdU, our new 3,3‐difluoroazetidine rhodamine azide outperformed the popular 5‐TAMRA‐azide, making it among the best available choices when it comes to fluorescent imaging of DNA. In a further exploration of the fluorescence properties of these dyes, a set of bis‐MPA dendrons carrying multiple fluorescein or rhodamine units was prepared by branching click chemistry. Fluorescence self‐quenching of fluorescein‐ and rhodamine‐functionalized dendrons limited the suitability of the dyes as labels in EdU‐based experiments but provided new insights into these effects. [ABSTRACT FROM AUTHOR]

Rhodamine Schiff bases as fluorescent chemo-sensors, fluorogenic cation sensors, is scientifically exigent work. Rhodamine Schiff base derivatives have gained attention due to their structural variability. The combination of donor and acceptor groups with delocalized π-orbital results in excellent fluorescent properties due to intramolecular charge transfer (ICT) and opening of spirolactam ring of Rhodamine moiety. In this review, we summarize information about Rhodamine Schiff bases sensors reported over the past two decades (2002–2022). We focused on the design, synthesis, and sensing mechanism (ON/OFF, OFF/ON, and ON-OFF-OFF) of these sensors for Fe3+ and Cu2+ metal ions, as well as their practical applications. We also examined how the photophysical properties of these sensors change when they coordinate with the metal ions, resulting in changes in the typical sensing behaviour, such as a hypochromic/hyperchromic or hypsochromic/bathochromic shift. We anticipate that this review will provide a fundamental framework for researchers to further investigate Rhodamine Schiff-based sensors. [ABSTRACT FROM AUTHOR]

Three one‐pot three‐step four‐component reaction sequences for spiropyran synthesis have been developed, based around three different methods for in situ generation of 1,2,3‐trisubstituted indoles (indole N‐alkylation, Fischer indolisation and indole C‐alkylation). The reaction sequences give access to a broad swathe of spiropyran structures. Each sequence is operationally straightforward, rapid and high yielding. We have synthesized 58 structurally diverse spiropyrans bearing a wide range of useful functional groups, and their utility were demonstrated in the targeted synthesis of potential ratiometric fluorescence probes for metal ions and spiropyran‐cholesterol conjugates. Finally, we showed that our one‐pot N‐alkylation‐C‐alkylation‐condensation sequence can underpin combinatorial spiropyran synthesis through generation of a 16‐member spiropyran library. [ABSTRACT FROM AUTHOR]

Diethyl chlorophosphate (DCP) has similar reactivity to sarin, which is widely known as a nerve agent that is often used in terrorist attacks. As DCP lacks high toxicity, it can be used as a model compound for sarin detection. Besides their use as chemical warfare agents (CWAs), organophosphorus compounds (OPs) also have greater implications for human health. To maintain the balance in global security the first and most in demand work is to establish efficient detection methods for monitoring CWAs. The work presented here reports a benzothiazole-based fluorescent chemodosimeter (BZ-DAM) for the fluorogenic detection of DCP via the ESIPT assisted ICT mechanism. The benzothiazole unit serves as a fluorophore, whereas the phenolic and imine groups act as a recognition unit for DCP. In this mechanistic path, the phenol group in BZ-DAM is phosphoesterified by DCP, which leads to a significant fluorescence change and assists the hydrolysis of the aldemine of BZ-DAM. The detection limit was found to be 0.43 μM by the fluorescence method. BZ-DAM is also stable in biological mediums and a physiological pH range and can be successfully used to detect intracellular DCP in living cells. Scanning electron microscopy (SEM) studies of a polycaprolactone (PCL)-BZ-DAM composite also revealed partial deformation of the surface of the nanomaterials upon the adsorption of DCP, indicating a DCP-mediated chemical transformation. [ABSTRACT FROM AUTHOR]

An amphiphilic block copolymer, poly(N-isopropyl acrylamide)-b-poly(N-vinyl carbazole) containing 1,8-naphthalimide and spirolactam rhodamine 6G moieties, has been designed as fluorescent sensors for detecting pH, Fe3+ ion, and temperature. The emission from the poly(N-vinyl carbazole) block almost disappears, and the enhanced emissions from the 1,8-naphthalimide (505 nm) and rhodamine 6G (555 nm) moieties are observed due to the effective resonance energy transfer among the fluorophores. The plots of I555/I505 functional of pH value of the Britton-Robinson buffer, Fe3+ concentration, and temperature show that there are good linear relationships in particular ranges. The results indicate that the block copolymer can be used as multiplexing ratiometric fluorescent sensors and realized at different excitation wavelengths. The functional relationship of the I555/I505 value and the concentration of the detection medium has been established according to Förster theory, which is consistent with the experimental results. [ABSTRACT FROM AUTHOR]

Seminaphthorhodafluor (SNARF) Schiff base (SNARF-SB) bridged periodic mesoporous organosilicas (SSPMOs) with "turn-on" fluorescence enhancement for sensing Cu2+ were synthesized via a template-directed co-condensation method. Small-angle x-ray scattering (SAXS) patterns, high resolution transmission electron microscope (HRTEM) images, and N2 adsorption–desorption isotherms indicated the presence of mesoporous structure in the SSPMOs. FT-IR spectra and 29Si MAS NMR data confirmed the successful incorporation of bridged organic groups in the framework of SSPMOs. The luminous properties that SSPMOs had a selective response to Cu2+ were investigated by UV–Vis absorption spectroscopy and fluorescence spectroscopy. The limit of detection (LOD) was 5.1 × 10–7 M and binding stoichiometry was determined 1:1 between SNARF-SB and Cu2+. The fluorescence enhancement of SSPMOs towards Cu2+ was induced by ring-opening of the spirolactam in SNARF-SB in framework of SSPMOs, which was confirmed by FT-IR spectra of SNARF-SB with Cu2+. Moreover, SSPMOs have improved fluorescence lifetimes compared with that of SNARF-SB. Therefore, SSPMOs can be a progressive chemical sensor for Cu2+ due to its high selectivity, recyclability, and stability. [ABSTRACT FROM AUTHOR]

Many ways to produce plasmonically-active substrates used for SERS applications, which is a nondestructive and reliable spectroscopy method, have been tried in recent years. Here we have presented an economical and easy procedure for synthesizing Ag NSs on Cu-grid in one step. Structural and elemental characterizations of Ag NSs on the Cu-grid were performed by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). Ag NSs on Cu-grids cause a high electromagnetic increase due to having complex morphology. Thus, the determination of R6G is easily realized even at very low concentrations such as 100 pM. It is predicted that different metallic nanostructures can be obtained by applying a similar recipe for different applications. [ABSTRACT FROM AUTHOR]

Seminaphthorhodafluor (SNARF) Schiff base (SNARF-SB) bridged periodic mesoporous organosilicas (SSPMOs) with "turn-on" fluorescence enhancement for sensing Cu2+ were synthesized via a template-directed co-condensation method. Small-angle x-ray scattering (SAXS) patterns, high resolution transmission electron microscope (HRTEM) images, and N2 adsorption–desorption isotherms indicated the presence of mesoporous structure in the SSPMOs. FT-IR spectra and 29Si MAS NMR data confirmed the successful incorporation of bridged organic groups in the framework of SSPMOs. The luminous properties that SSPMOs had a selective response to Cu2+ were investigated by UV–Vis absorption spectroscopy and fluorescence spectroscopy. The limit of detection (LOD) was 5.1 × 10–7 M and binding stoichiometry was determined 1:1 between SNARF-SB and Cu2+. The fluorescence enhancement of SSPMOs towards Cu2+ was induced by ring-opening of the spirolactam in SNARF-SB in framework of SSPMOs, which was confirmed by FT-IR spectra of SNARF-SB with Cu2+. Moreover, SSPMOs have improved fluorescence lifetimes compared with that of SNARF-SB. Therefore, SSPMOs can be a progressive chemical sensor for Cu2+ due to its high selectivity, recyclability, and stability. [ABSTRACT FROM AUTHOR]

Fluorescent indicators that respond to changes in biological membrane potentials provide a powerful complement to existing methods for monitoring neuronal activity. Indicators that absorb and emit in the near infrared window are especially attractive, since lower energy wavelengths excite fewer biological molecules and can penetrate more deeply into biological tissues. In this work, we incorporate sulfone rhodamine chromophores into a voltage‐sensitive scaffold in order to generate voltage sensitive fluorophores which absorb and emit above 700 nm. These Sulfone Rhodamine Voltage Reporters (SuRhoVRs) partition into cell membranes and display good sensitivity to membrane potential changes. The most sensitive SuRhoVR derivative also displays excellent photostability and can track membrane potential changes in dissociated rat hippocampal neurons. [ABSTRACT FROM AUTHOR]