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Two natural adsorbent materials, potassium humate (KHA) and montmorillonite (MMT), were successfully prepared by embedding them in sodium alginate (SA) gel spheres through physical cross-linking with CaCl 2 . And CaCO 3 was used as a porogenic agent to prepare the porous composites, KHA/SA/MMT. The materials were characterized by using XRD, TGA, SEM, and N 2 adsorption/desorption equipment. The results showed that MMT and KHA were successfully embedded in the SA gel; the introduction of MMT increased the thermal stability of the composites and the embedding of MMT, and the porogenic effect of CaCO 3 increased the specific surface area of the composites substantially, which provided favorable conditions for adsorption and treatment of pollutants. In addition, a one-way exploratory experiment yielded a higher removal rate of Rhodamine B (RhB) at D = 0.6 g/L, pH = 5, C 0  = 100 mg/L, and t = 360 min. The adsorption kinetics and adsorption isotherm conformed to the secondary kinetic model and Langmuir model, respectively, and the maximum adsorption of RhB by KHA/SA/MMT could reach up to 884.96 mg/g at 303 K. The adsorption mechanism for RhB was shown by FT-IR and XPS analyses to be possibly bound by non-covalent bonding forces. After seven consecutive adsorption-desorption cycles, the adsorption of RhB by KHA/SA/MMT still reached 80.75%. Therefore, the prepared gel spheres have the advantages of easy regeneration and efficient reuse and great potential for application in purifying RhB from wastewater., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.) more...

Removal of toxic dyes such as Rhodamine B is essential as it pollutes aqueous and soil streams as well. This comprehensive study explores the potential of Calophyllum inophyllum seed char as an efficient bio-adsorbent based on their characteristic properties and a comparative study between various carbon-based adsorbents on the adsorption capacity of Rhodamine B dye. In this study, the char was prepared from Calophyllum inophyllum seed using a slow pyrolysis process (298 K/min) at an optimum temperature of 823 K and used as an adsorbent for the removal of Rhodamine B from water. The resulting char was mesoporous and had 155.389 m 2 /g surface areas (BET) and 0.628 cc/g pore volume. The formation of pores was observed from the SEM analysis. The adsorption studies were tested and optimized through various parameters such as solution pH, adsorbent dosage, initial dye concentration, stirring speed, contact time, and solution temperature. Maximum 95.5 % removal of Rhodamine B was possible at the pH: 2, stirring speed: 100 rpm, time: 25 min, temperature 308 K, and dose: 1.2 g/L. The highest adsorption capacity at equilibrium was determined to be 169.5 (mg/g) through Langmuir adsorption isotherm studies and followed pseudo 2nd order kinetics. The thermodynamics study confirmed the adsorption processes were spontaneous (ΔG°=-0.735 kJ/mol) and endothermic (ΔH° = 4.1 kJ/mol) processes. The reusability study confirmed that the mesoporous char can be reused as an efficient adsorbent for up to 3 cycles for environmental remediation., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.) more...

In this study, a new chitosan Schiff base with surface modification using citric acid was synthesized for efficient removal of pernicious dyes, namely Bismarck Brown R (BBR) and Rhodamine B (RhB), from wastewater. The physicochemical properties of the modified chitosan Schiff base were comprehensively investigated. Adsorption studies demonstrated that BBR adsorption occurred through monolayer formation, while RhB adsorption proceeded via multilayer formation on the heterogeneous surface. The synthesized adsorbent exhibited exceptional dye removal efficiency, with a Langmuir saturation capacity of 348 ± 11.0 mg.g -1 for BBR and 145 ± 18.44 mg.g -1 for RhB. Isotherm data fitting revealed consistency with the Langmuir isotherm model for BBR and the Freundlich isotherm model for RhB. Notably, the modified chitosan Schiff base showcased enhanced antibacterial properties, effectively inhibiting both gram-positive and gram-negative bacteria. The study's findings underscore the potential of this novel chitosan-based Schiff base as an efficient adsorbent for the removal of various dyes from wastewater, emphasizing its versatility and practical applicability in water treatment processes., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.) more...

Fluorescent dyes synergize with advanced microscopy for researchers to investigate the location and dynamic processes of biomacromolecules with high spatial and temporal resolution. However, the instability of fluorescent dyes, including photobleaching and photoconversion, represent fundamental limits for super-resolution and time-lapse imaging. In this review, we discuss the latest advances in improving the photostability of fluorescent dyes. We summarize the primary photobleaching processes of cyanine and rhodamine dyes and highlight a range of strategies developed in recent years to strengthen these fluorophores. Additionally, we discuss the influence of protein microenvironments and labeling methods on the photostability of fluorophores. We aim to inspire next-generation robust and bright fluorophores that ultimately enable the routine practice of time-lapse super-resolution imaging of live cells., Competing Interests: Declaration of competing interest Z.C. is an inventor of a patent on mitochondria dyes described in this review (CN 202010492298.8). Z.C. and Y.Z. are the inventors of a patent on the fluorophores with S-arylation-type conjugation chemistry in this review (CN202210228995.1, patent pending)., (Copyright © 2024 Elsevier Ltd. All rights reserved.) more...

We report the application of pump-probe fluorescence microscopy in time-resolved polarization imaging. We derived the equations governing the pump-probe stimulated emission process and characterized the pump and probe laser power levels for signal saturation. Our emphasis is to use this novel methodology to image polarization properties of fluorophores across entire cells. As a feasibility study, we imaged a 15-microm orange latex sphere and found that there is depolarization that is possibly due to energy transfer among fluorescent molecules inside the sphere. We also imaged a mouse fibroblast labeled with CellTracker Orange CMTMR (5-(and-6)-(((4-chloromethyl)benzoyl)amino)tetramethyl-rhodamine). We observed that Orange CMTMR complexed with gluthathione rotates fast, indicating the relatively low fluid-phase viscosity of the cytoplasmic microenvironment as seen by Orange CMTMR. The measured rotational correlation time ranged from approximately 30 to approximately 150 ps. This work demonstrates the effectiveness of stimulated emission measurements in acquiring high-resolution, time-resolved polarization information across the entire cell. more...

Giant unilamellar vesicles (GUVs) composed of different phospholipid binary mixtures were studied at different temperatures, by a method combining the sectioning capability of the two-photon excitation fluorescence microscope and the partition and spectral properties of 6-dodecanoyl-2-dimethylamino-naphthalene (Laurdan) and Lissamine rhodamine B 1,2-dihexadecanoyl-sn-glycero-3-phosphoethanolamine (N-Rh-DPPE). We analyzed and compared fluorescence images of GUVs composed of 1,2-dilauroyl-sn-glycero-3-phosphocholine/1, 2-dipalmitoyl-sn-glycero-3-phosphocholine (DLPC/DPPC), 1, 2-dilauroyl-sn-glycero-3-phosphocholine/1, 2-distearoyl-sn-glycero-3-phosphocholine (DLPC/DSPC), 1, 2-dilauroyl-sn-glycero-3-phosphocholine/1, 2-diarachidoyl-sn-glycero-3-phosphocholine (DLPC/DAPC), 1, 2-dimyristoyl-sn-glycero-3-phosphocholine/1, 2-distearoyl-sn-glycero-3-phosphocholine (DMPC/DSPC) (1:1 mol/mol in all cases), and 1,2-dimyristoyl-sn-glycero-3-phosphoethanolamine/1, 2-dimyristoyl-sn-glycero-3-phosphocholine (DMPE/DMPC) (7:3 mol/mol) at temperatures corresponding to the fluid phase and the fluid-solid phase coexistence. In addition, we studied the solid-solid temperature regime for the DMPC/DSPC and DMPE/DMPC mixtures. From the Laurdan intensity images the generalized polarization function (GP) was calculated at different temperatures to characterize the phase state of the lipid domains. We found a homogeneous fluorescence distribution in the GUV images at temperatures corresponding to the fluid region for all of the lipid mixtures. At temperatures corresponding to phase coexistence we observed concurrent fluid and solid domains in the GUVs independent of the lipid mixture. In all cases the lipid solid domains expanded and migrated around the vesicle surface as we decreased the temperature. The migration of the solid domains decreased dramatically at temperatures close to the solid-fluid-->solid phase transition. For the DLPC-containing mixtures, the solid domains showed line, quasicircular, and dendritic shapes as the difference in the hydrophobic chain length between the components of the binary mixture increases. In addition, for the saturated PC-containing mixtures, we found a linear relationship between the GP values for the fluid and solid domains and the difference between the hydrophobic chain length of the binary mixture components. Specifically, at the phase coexistence temperature region the difference in the GP values, associated with the fluid and solid domains, increases as the difference in the chain length of the binary mixture component increases. This last finding suggests that in the solid-phase domains, the local concentration of the low melting temperature phospholipid component increases as the hydrophobic mismatch decreases. At the phase coexistence temperature regime and based on the Laurdan GP data, we observe that when the hydrophobic mismatch is 8 (DLPC/DAPC), the concentration of the low melting temperature phospholipid component in the solid domains is negligible. This last observation extends to the saturated PE/PC mixtures at the phase coexistence temperature range. For the DMPC/DSPC we found that the nonfluorescent solid regions gradually disappear in the solid temperature regime of the phase diagram, suggesting lipid miscibility. This last result is in contrast with that found for DMPE/DMPC mixtures, where the solid domains remain on the GUV surface at temperatures corresponding to that of the solid region. In all cases the solid domains span the inner and outer leaflets of the membrane, suggesting a strong coupling between the inner and outer monolayers of the lipid membrane. This last finding extends previous observations of GUVs composed of DPPE/DPPC and DLPC/DPPC mixtures (, Biophys. J. 78:290-305). more...

Fluorescence correlation spectroscopy (FCS) is generally used to obtain information about the number of fluorescent particles in a small volume and the diffusion coefficient from the autocorrelation function of the fluorescence signal. Here we demonstrate that photon counting histogram (PCH) analysis constitutes a novel tool for extracting quantities from fluorescence fluctuation data, i.e., the measured photon counts per molecule and the average number of molecules within the observation volume. The photon counting histogram of fluorescence fluctuation experiments, in which few molecules are present in the excitation volume, exhibits a super-Poissonian behavior. The additional broadening of the PCH compared to a Poisson distribution is due to fluorescence intensity fluctuations. For diffusing particles these intensity fluctuations are caused by an inhomogeneous excitation profile and the fluctuations in the number of particles in the observation volume. The quantitative relationship between the detected photon counts and the fluorescence intensity reaching the detector is given by Mandel's formula. Based on this equation and considering the fluorescence intensity distribution in the two-photon excitation volume, a theoretical expression for the PCH as a function of the number of molecules in the excitation volume is derived. For a single molecular species two parameters are sufficient to characterize the histogram completely, namely the average number of molecules within the observation volume and the detected photon counts per molecule per sampling time epsilon. The PCH for multiple molecular species, on the other hand, is generated by successively convoluting the photon counting distribution of each species with the others. The influence of the excitation profile upon the photon counting statistics for two relevant point spread functions (PSFs), the three-dimensional Gaussian PSF conventionally employed in confocal detection and the square of the Gaussian-Lorentzian PSF for two photon excitation, is explicitly treated. Measured photon counting distributions obtained with a two-photon excitation source agree, within experimental error with the theoretical PCHs calculated for the square of a Gaussian-Lorentzian beam profile. We demonstrate and discuss the influence of the average number of particles within the observation volume and the detected photon counts per molecule per sampling interval upon the super-Poissonian character of the photon counting distribution. more...

A dual‐mode "turn‐on" fluorescent‐colorimetric sensor, 1‐methyl piperazine rhodamine amide (MPRA), has been identified and developed for acidic pH detection in practice. After its structure and photophysical property were characterized and investigated in detail, it was noted to find that nonfluorescent and colorless MPRA would present rose Bengal color and emit strong saffron yellow fluorescence simultaneously with pH decreasing from 7.2 to 1.8 in PBS/acetonitrile (1 : 1, v/v). Under the optimized conditions, MPRA expressed an excellent partitioned and dual‐mode response to pH, i. e., ranging from 1.8 to 3.6 and 3.6 to 7.2 for fluorescent analysis, and 1.8 to 4.0 and 4.0 to 7.2 for colorimetric one with the acidity constant (Ka) of 1.75 obtained from Henderson‐Hasselbach equation. Importantly, the sensing was real‐time and reversible, which was successfully applied for pH detection in real fruit aqueous samples with R.S.D. less than 5.0%. The selective recognition mechanism for MPRA to H+ was confirmed to be the ring‐opened amide form mechanism by 1H NMR and theoretical calculation. MPRA will be a potential dual‐mode sensor for on‐site monitoring pH in acidic environments. [ABSTRACT FROM AUTHOR] more...

Graphene-enhanced Raman scattering (GERS) on isotopically labelled bilayer and a single layer of pristine and partially hydrogenated graphene has been studied. The hydrogenated graphene sample showed a change in relative intensities of Raman bands of Rhodamine 6 G (R6G) with different vibrational energies deposited on a single layer and bilayer graphene. The change corresponds qualitatively to different doping of graphene in both areas. Pristine graphene sample exhibited no difference in doping nor relative intensities of R6G Raman peaks in the single layer and bilayer areas. Therefore, it was concluded that strain and strain inhomogeneities do not affect the GERS. Because of analyzing relative intensities of selected peaks of the R6G probe molecules, it is possible to obtain these results without determining the enhancement factor and without assuming homogeneous coverage of the molecules. Furthermore, we tested the approach on copper phtalocyanine molecules. [ABSTRACT FROM AUTHOR] more...

The variation of the fluorescence spectral signature of tracer solutions with temperature enables temperature imaging measurements in liquids and sprays by simultaneously recording and rationing the fluorescence intensity detected in two separate wavelength channels. In this work, we recorded fluorescence spectra of ethanol-based solutions of nine laser dyes used as tracers (PTP, stilbene 1, coumarin 152, coumarin 153, rhodamine B, rhodamine 101, pyrromethene 597, DCM, and pyridine 1) after excitation at either 266, 355, or 532 nm (depending on the dye) for temperatures between 298 and 348 K (close to the boiling point of the solvent), and for concentrations (depending on dye) around 10 mg/l (i.e., ~ 10–5 mol/l). The influence of signal self-absorption was investigated for the tracers best suited for thermometry, rhodamine B and coumarin 152, where the latter is almost unaffected due to its large Stokes shift. In thin-film (100 µm) cells, possible concentration effects on the fluorescence spectrum were investigated in the absence of signal self-absorption in the 0.1–10 and 0.5–50 mg/l range for rhodamine B and coumarin 152, respectively. Sensitivities of the two-color intensity ratios were determined for two selected color detection channels for each tracer characterized by their center wavelength and spectral half width and conditioned on averaged intensities of larger than 10% of the spectral peak of their respective fluorescence spectrum. The use of coumarin 152 that showed the overall best spectroscopic properties was demonstrated for temperature imaging in a burning ethanol spray. [ABSTRACT FROM AUTHOR] more...

In this paper, Zn doped CdTe quantum dots (CdTe:Zn QDs) was synthesized and imbedded in silica particles via a reverse microemulsion method to form a QDs/silica core. It acted as a fluorescence energy donor to conjugate with fluorescence energy acceptor rhodamine B derivative and construct a fluorescence sensor based on the principle of fluorescence resonance energy transfer (FRET). Hg2+ ions induced the ring-opening reaction of the spirolactam rhodamine moieties, leading to the occurrence of FRET. The fluorescence probe was accomplished by detecting the fluorescence intensity at 521 nm and 577 nm, and it exhibited high selectivity, sensitivity and accuracy and the detection limit reached as low as 0.5 µM. [ABSTRACT FROM AUTHOR] more...

In order to quantitatively detect hydrogen polysulfides (H2Sn, n > 1) in biosystems, we propose a new two-photon turnon fluorescent probe, named Np–Sn, based on the D–π–A skeleton two-photon fluorophore of 4 -hydroxy-1,8-naphthalimide derivative and deprotection of 2-fluoro-5-nitrobenzoic ester by H2Sn–Np–Sn displayed a more than 80-fold enhancement towards H2Sn in 550 nm and high sensitivity with a detection limit as low as 33 nM. Additionally, the probe Np–Sn was further used for fluorescence imaging of H2Sn in living cells under two-photon excitation (820 nm), which showed a high-resolution imaging, thus demonstrating its practical application in biological systems for the study of physiological and pathological functions of H2Sn. [ABSTRACT FROM AUTHOR] more...

A novel six-membered rhodamine-based fluorescent probe (6G-ClO) was developed from 2-formyl rhodamine (6G-CHO) and used for hypochlorite detection in water and HUVEC cells. Different from planar penta cycle of rhodamine spirolactam, there was a twist six-membered spirocyclic hydrazone in 6G-ClO optimized by Gaussian software at DFT/B3LYP/6-31G(d) level. The high selectivity, high sensitivity and fast response of 6G-ClO towards ClO− would be attributed to the twist six-membered spirocycle. Test-strip prepared with 6G-ClO was successfully used to semi-quantitatively indicate the concentration of ClO− in water. 6G-ClO can also quantitatively detect the concentration of ClO− in tap water and swimming pool water. The detection limit of 6G-ClO was as low as 12 nM. The co-localization staining of HUVEC cells further verified that 6G-ClO could specifically accumulate in lysosomes and capture exogenous/endogenous ClO− in living lysosomes. 6G-ClO would be a practical probe for real-time monitoring of ClO− in the biological and real water samples. Image 1 • A twist six-membered rhodamine fluorescent probe 6G-ClO has been developed with the precursor 2-formyl-rhodamine 6G. • 6G-ClO bearing unique six-membered spirocycle is characterized by NMR and HRMS spectra. • 6G-ClO exhibits high sensitivity and fast response to ClO− in real water samples. • The detection limit of 6G-ClO was as low as 12 nM for ClO−. • 6G-ClO localizes specifically in lysosomes and monitors exogenous and endogenous ClO− in live HUVEC cells. [ABSTRACT FROM AUTHOR] more...

A novel imidazo[1,2-a]pyridine-rhodamine ratiometric fluorescent probe IP-Hg for Hg2+ based on a fluorescence resonance energy transfer mechanism has been developed. The probe has been proved to show high sensitivity and high selectivity toward Hg2+. Furthermore, it could be used for imaging Hg2+ in cells and in polluted water. Image 1 • A ratiometric fluorescent probe for sensing Hg2+ based on new imidazo[1,2-a]pyridine fluorophore has been synthesized. • The probe exhibits highly sensitivity and selectivity toward Hg2+ (LOD: 9.1 nM). • The ratiometric fluorescent probe displays a remarkable emission shift (220 nm). • The probe show low cytotoxicity and can image in cells. [ABSTRACT FROM AUTHOR] more...

The formal replacement of one dialkylamino group in rhodamines with a hydroxyl group transforms them into rhodols. This apparently minor difference is not as small as one may think; rhodamines belong to the cyanine family whereas rhodols belong to merocyanines. Discovered in the late 19th century, rhodols have only very recently begun to gain momentum in the field of advanced fluorescence imaging. This is in part due to the increased understanding of their photophysical properties, and new methods of synthesis. Rationalization of how the nature and arrangement of polar substituents around the core affect the photophysical properties of rhodols is now possible. The emergence of so-called π-expanded and heteroatom-modified rhodols has also allowed their fluorescence to be bathochromically shifted into regions applicable for biological imaging. This review serves to outline applicable synthetic strategies for the synthesis of rhodols, and to highlight important structure–property relationships. In the first part of this Review, various synthetic methods leading to rhodols are presented, followed by structural considerations and an overview of photophysical properties. The second part of this review is entirely devoted to the applications of rhodols as fluorescent reporters in biological imaging. [ABSTRACT FROM AUTHOR] more...

A rhodamine B-based chromo-fluorogenic probe BOS is prepared with a good yield by condensating an o-diaminobenzene functionalized rhodamine derivative (RBO) and a large steric hindrance salicylaldehyde, and characterized by elemental analysis, infrared spectroscopy (IR), 1H and 13C NMR technology, and high resolution mass spectrum (HRMS). Spectroscopy experiments reveal that the probe can selectively and sensitively detect Al3+ from a variety of metal ions with a low detection limit of 1.855 μmol/L. Compared to traditional detection methods, BOS provides an inexpensive, rapid and straightforward way for Al3+ detection that can be distinguished by "naked eye". The MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2- H - tetrazoliubromide) assays and cell imaging experiments demonstrate that the sensor is low toxic and amicable for Al3+ sensing in living cells. Image 1 • A novel rhodamine-based probe BOS is designed and synthesized. • BOS is able to high selectively and sensitively detect Al3+. • The detection process can be identified through naked eye. • BOS is capable of detecting Al3+ in complex biological environment. [ABSTRACT FROM AUTHOR] more...

Perimedine labelled rhodamine dye 1 has been designed and synthesised. Metal ion binding studies of 1 have been performed in CH3CN/H2O (3:1, v/v, 10 mM Tris-HCl buffer, pH = 6.90). Compound 1 senses multiple metal ions such as Al3+, Fe3+ and Fe2+ by exhibiting turn on fluorescence and colour change (colourless to pink) under different experimental conditions. Concentration variation distinguishes Al3+ from Fe3+ ion. At low concentration (c = 1 x 10−4 M), only Al3+ ion can exhibit turn on fluorescence with sharp colour change. Sensing of Fe2+ ion through turn on fluorescence and colour change has been possible via in situ oxidation by following Fenton's reaction. [ABSTRACT FROM AUTHOR] more...

Fluorophores and probes are invaluable for the visualization of the location and dynamics of gene expression, protein expression, and molecular interactions in complex living systems. Rhodamine dyes are often used as scaffolds in biological labeling and turn‐on fluorescence imaging. To date, their absorption and emission spectra have been expanded to cover the entire near‐infrared region (650–950 nm), which provides a more suitable optical window for monitoring biomolecular production, trafficking, and localization in real time. This review summarizes the development of rhodamine fluorophores since their discovery and provides strategies for modulating their absorption and emission spectra to generate specific bathochromic‐shifts. We also explain how larger Stokes shifts and dual‐emissions can be obtained from hybrid rhodamine dyes. These hybrid fluorophores can be classified into various categories based on structural features including the alkylation of amidogens, the substitution of the O atom of xanthene, and hybridization with other fluorophores. [ABSTRACT FROM AUTHOR] more...

The novel ratiometric fluorescent probe HPQRB with an ESIPT effect based on Michael addition for highly sensitive and fast detection of sulfite in living HepG2 cells is reported. HPQRB can be easily synthesized by a two‐step condensation reaction. HPQRB has a large emission shift (Δλ=116 nm), which is beneficial for fluorescence imaging research, and its sulfite‐responsive site is based on a rhodamine‐like structure with the emission peak at 566 nm, which decreases with increasing sulfite concentration. and its HPQ structure always has an ESIPT effect throughout the reaction process, keeping the emission peak at 450 nm as a self‐reference. In particular, HPQRB has high selectivity for sulfite and responds quickly (within 30 s) with a low detection limit (44 nM). Furthermore, HPQRB has been successfully used for fluorescence imaging of sulfite in HepG2 cells, demonstrating the superior ability to detect sulfite under physiological conditions. [ABSTRACT FROM AUTHOR] more...

• Novel turn-on fluorescent probe RhB@MOF-5 for β-glucuronidase is firstly fabricated. • The reason of β-glucuronidase responses is depend on the synergistic effect of IFE and SQE. • The probe exhibits high selectivity and real human serum testing. • The theoretical limit of detection of this platform is low to 0.03 U L−1. β-Glucuronidase (β-GCU) is closely related to the occurrence of multiple diseases, and it has been applied as a biomarker and therapeutic target in clinical diagnosis. However, reliable methods with high selectivity and sensitivity for monitoring β-GCU are still lacked. Herein, we designed a novel fluorescent nanoprobe, rhodamine B encapsulated MOF-5 (RhB@MOF-5) for the first time, to detect β-GCU through the synergistic effect of inner filter effect (IFE) and static quenching effect (SQE) by employing 4-nitrophenyl-β-D-glucuronide (PNPG) as the substrate. After encapsulating into MOF-5, the fluorescence emission of RhB at 550 nm excited by 320 nm was greatly enhanced. The major overlap between the fluorescence excitation spectrum of RhB@MOF-5 (about 320 nm) and the ultraviolet absorption spectrum of PNPG (about 310 nm) lead to PNPG being a good IFE absorber in this sensing system. Under the optimized conditions, the excitation spectrum of the RhB@MOF-5 could be absorbed by PNPG, resulting in the dramatically decrease of fluorescence emission. After adding β-GCU into the system, the substrate of PNPG would be enzymatic hydrolyzed to p -nitrophenol (PNP) and glucose, then the IFE disappearance and the fluorescence recovered. The current sensing platform was interference-free and exhibited a broad linearity relationship for β-GCU range of 0.1–10 U L−1 (R2 = 0.9957) with a limit of detection as low as 0.03 U L−1, which was reduced by more than one orders compared with the reported methods. Moreover, the encapsulation of dyes using porous nanoparticles to achieve some tailor-made characteristics will enrich experimental design inspiration. [ABSTRACT FROM AUTHOR] more...

• Use of bulky 2-aminophenylboronic acid pinacol ester enables to form closed spirolactam rings with high pKa values. • The probes can specifically target lysosomes in live cells. • The probes provide powerful tools to visualize intracellular pH changes in live cells. Sterically hindered fluorescent probes (A - C) have been developed by introducing 2-aminophenylboronic acid pinacol ester to a traditional, A , a near-infrared rhodamine dye, B , and a near-infrared hemicyanine dye, C , forming closed spirolactam ring structures. Probe A was non-fluorescent under basic pH conditions whereas probes B and C were moderately fluorescent with fluorescence quantum yields of 9% and 5% in pH 7.4 PBS buffer containing 1% ethanol, respectively. With all probes increasing acidity leads to significant increases in fluorescence at 580 nm, 644 and 744 nm for probes A , B and C with fluorescence quantum yields of 26%, 21% and 10% in pH 4.5 PBS buffer containing 1% ethanol, respectively. Probes A , B and C were calculated to have pK a values of 5.81, 5.45 and 6.97. The difference in fluorescence under basic conditions is ascribed to easier opening of the closed spirolactam ring configurations due to significant steric hindrance between the 2-aminophenylboronic acid pinacol ester residue and an adjacent H atom in the xanthene derivative moiety in probe B or C. The probes show fast, reversible, selective and sensitive fluorescence responses to pH changes, and are capable of sensing lysosomal pH variations in living cells. [ABSTRACT FROM AUTHOR] more...

• Ratiometric near-infrared fluorescent probes for pH detection were built based on BODIPY donors and near-infrared rhodamine and merocyanine acceptor. • High efficient energy transfer from BODIPY donors to the Rhodamine and merocyanine acceptor was achieved through TBET or combination of TBET and FRET. • The probes show ratiometric fluorescence responses to pH downgrades through BODIPY fluorescence decreases and fluorescence increases of rhodamine or merocyanine acceptor. • The probes displays excellent selectivity to pH over biological species such as amino acids, common cations and anions. • Probe B has been applied in ratiometric detection of intracellular pH changes and fluctuations under treatment of NH 4 Cl and chloroquine. Three fluorescent probes have been developed by conjugating three different BODIPY donors to rhodamine and merocyanine acceptors for ratiometric determination of lysosomal pH variations. Probe A consists of a 1,3,5,7-tetramethyl-BODIPY donor and a near-infrared rhodamine acceptor bearing a lysosome-targeting morpholine residue. Probe B is composed of a 3,5-dimethyl-BODIPY donor and a near-infrared rhodamine acceptor modified with an o -phenylenediamine residue. Probe C contains a 3-styrene-functionalized BODIPY donor with longer wavelength emission and a near-infrared merocyanine acceptor containing a morpholine residue. Under neutral or basic pH conditions, the probes only show fluorescence from the BODIPY donors under BODIPY excitation because the rhodamine and merocyanine acceptors maintain closed spirolactam configurations. However, excitation at BODIPY absorption wavelengths concomitant with gradual pH decrease results in fluorescence decreases with the BODIPY donors and fluorescence increases from the rhodamine and merocyanine acceptors due to through-bond energy transfer from the donors to the acceptors. This is because the spirolactam ring opens under more acidic conditions and fluorescence of the acceptors results from significantly improved π-conjugation. These experimental results are substantiated with theoretical calculations on models of the different probes. The probes have all been used to determine lysosome pH variations in HeLa cells. Probe B was further utilized to successfully detect pH fluctuations in HeLa cells under oxidative stress induced with NH 4 Cl and chloroquine. [ABSTRACT FROM AUTHOR] more...

A potential rhodamine derived chemosensor was synthesized for the quantitative colorimetric detection of F− ions in real-time and to design multiple-input logic gates at the molecular level. Bottom-up fabrication techniques to design logic gates using chemical inputs have been initiated for a decade now and have shown immense promise to make the size of microprocessors even smaller, as the chemical signals are at the molecular level. The chemosensor exhibited a change in color from pale yellow to dark yellow for F− ions. However, upon adding Cu2+ ions the same solution, pink coloration was exhibited. These changes in color and absorbance were used to develop chemical input logic gates. Further, the color change trend could be reversed for sixteen cycles with the alternating addition of F− and Cu2+ ions. Moreover, the chemosensor was used to design combinational three input logic gates by adding Cu2+, F− and Ni2+ ions. In addition, UV-vis titrations and 1H NMR titrations were carried out to understand the color change and binding mechanism. Furthermore, the chemosensor was investigated for its ability to detect F− ions in real samples. [ABSTRACT FROM AUTHOR] more...

Nanosized surface-enhanced Raman scattering (SERS) substrates fabricated by the controlled growth of metal nanostructures on water-dispersed two-dimensional nanomaterials can open a new avenue for SERS analysis of liquid samples in biological fields. In this work, regular and uniform Ag nanostructures were grown on the surface of graphene oxide (GO) through a microwave-assisted hydrothermal method. Polyamidoamine (PAMAM) dendrimers were assembled on the surface of GO to form GO/PAMAM templates for growing Ag nanostructures, which are primarily comprised of Ag dimers and trimers. The prepared Ag/GO nanocomposites are highly dispersed and stable in aqueous solution and may be used as substrates for enhanced Raman detection of rhodamine 6 G (R6G) in aqueous solution. This special substrate provides high-performance SERS and suppresses R6G fluorescence in aqueous solution and is promising as a nanosized material for the enhanced Raman detection of liquid samples in biological diagnostics. [ABSTRACT FROM AUTHOR] more...

A simple selective colorimetric and fluorimetric chemosensor RD based on Rhodamine B hydrazone derivatives was designed and synthesized, which showed both colorimetric and fluorescence responses for cyanide and Cu2+ in aqueous solution with specific selectivity and high sensitivity. In the presence of cyanide, the sensor exhibited a visible color change from colorless to pale yellow by naked–eyes and rapidly produced a strong yellow fluorescence in aqueous solution. The detection limit on fluorescence response of RD sensor to CN− is down to 3.54 × 10−7 M. In addition, compared to other metal ions such as Fe3+, Hg2+, Ag+, Ca2+, Cu2+, Co2+, Ni2+, Cd2+, Pb2+, Cr3+, Zn2+ and Mg2+ in aqueous solutions, RD could show both colorimetric and fluorescence responses rapidly for Cu2+. Notably, this sensor can be used as a molecular switch controlled by CN− and H+ cyclically. Test strips based on RD were fabricated that could be used as a convenient and efficient CN− and Cu2+ test kits. RD could detect cyanide in germinated potato, bitter almond and tap water. This chemosensor enabled detection of two ions, which do not need to rely on two different sensors. A novel cyanide and Cu2+ specifically selective and highly sensitive chemosensor RD based on Rhodamine B hydrazone derivatives had been designed and synthesized. Unlabelled Image • Sensor RD is based on Rhodamine B hydrazone derivatives. • Sensor RD demonstrates specifically selective "naked-eye" recognition and fluorescence "turn-on" response for CN− and Cu2+in aqueous solution. • Sensor RD has been detected successfully CN− in germinated potato, bitter almond and tap water. • Test strips of RD were prepared and convenient and rapidly detected CN− and Cu2+. • Sensor RD can dual channel recognition for CN− and Cu2+in aqueous, which has the feasibility of practical application. [ABSTRACT FROM AUTHOR] more...

Hypochlorous acid (HClO) is one of the most important ROS (reactive oxygen species) and common pollutant in tap-water. However, the determination of HClO with fast response and high sensitivity/selectivity is still an urgent demanding. Here we fabricated a ratiometric fluorescent probe RC based on TBET (through-bond energy transfer) on the platform of coumarin and rhodamine with the thiosemicarbazide group as the linker. This probe could display the characteristic fluorescence emission of coumarin. Upon addition of HClO, the linker was reacted into an oxadiazole, resulting in the opening of spiro-ring of rhodamine. The resultant then gives ratiometric fluorogenic changes. The probe exhibits fast response and high selectivity and sensitivity towards HClO with a low limit of detection (~140 nM). Eventually, RC is successfully applicated for determining spiked HClO in water samples and imaging endogenous HClO in living cells. Unlabelled Image • A TBET-based ratiometric fluorescent probe for hypochlorous acid • High selectivity and rapid response (within 90 s) for hypochlorous acid over other ROS in a broad pH range • Detection of exogenous and endogenous hypochlorous acid in living cells [ABSTRACT FROM AUTHOR] more...

• A new near infrared fluorescent probe was reported to detect ATP and target lysosomes in cells. • Probe 1 was used in selective lysosome staining and for real-time ATP level monitoring. • Probe 1 exhibits excellent photostability, low cytotoxicity, and good cell membrane permeability. A new near infrared fluorescent probe was designed and prepared to detect ATP and target lysosomes in cells. The non-fluorescent probe was turned on during the interaction with ATP, affording a 115-fold increase in fluorescence intensity. The colorless probe turned purple upon interaction with ATP. The probe displayed high sensitivity and selectivity toward ATP compared with other biomolecules, such as AMP, ADP, GMP, and CMP. Such significant spectroscopic changes derive from a structural change of the probe's spirocyclic moiety to its ring-opened form. This occurs through electrostatic and π,π-stacking interactions between the probe and ATP. This probe was also used in selective lysosome staining and for real-time ATP level monitoring. It exhibits great advantages in cell imaging studies, such as excellent photostability, low cytotoxicity, and good cell membrane permeability. [ABSTRACT FROM AUTHOR] more...

A new fluorescent probe L fusing the rhodamine B scaffold with 2H‐benzo[b][1,4]oxazin‐3(4H)‐one moiety has been developed and applied as an acidic pH sensor. The ultraviolet (UV) and fluorescence spectra of the probe at different pH values were investigated in B–R buffer/MeOH (v: v = 3: 7). This probe showed increase of both the UV–Vis absorption and fluorescence emission from alkaline/neutral to acidic condition, reaching a strongest intensity at pH 2.13, but the intensities decreased when the pH decreased to 1.83. The color variation along the pH changes proved that the probe L can be used as a low‐cost optical sensor for the naked eye detection of proton in the present buffer. [ABSTRACT FROM AUTHOR] more...

• Chitosan derivatives were synthesized and characterized. • Amphipathic character is tuned by degree of acetylation and tertiary amino groups. • Charge density and hydrophobic forces improves the coacervation process of siRNA into nanoparticles. • Chitosan-siRNA nanoparticles with improved colloidal stability at physiological conditions are obtained. Chitosan has received a lot of attention as a carrier for small interfering RNA (siRNA), due to its capacity for complexation and intracellular release of these molecules. However, one of its limitations is its insolubility at neutral pH and the tendency towards aggregation of its nanoparticles in isotonic ionic strength. In this study, a series of amphipathic chitosans were synthesized by varying the degree of acetylation (DA) from ˜2 to ˜30 mol% and the degree of substitution (DS) from 5 to 25%. by tertiary amino groups (DEAE) The results showed that the adjustment of these parameters decreases the interparticle interactions mediated by hydrogen bonding to obtain nanoparticles with improved colloidal stability. siRNA-containing nanoparticles of 100 to 150 nm with low polydispersities (0.15–0.2) and slightly positive zeta potentials (˜+ 5 mV) were resistant to aggregation at pH 7.4 and ionic strength of 150 mM. This resistance to aggregation is provided by changes on the nanoparticle surface and highlights the importance of more organized self-assembly in providing colloidal stability at physiological conditions. Additionally, the PEGylation of the most promising vectors conferred favorable physicochemical properties to nanoparticles. The chitosans and their nanoparticles exhibited low toxicity and an efficient cell uptake, as probed by confocal microscopy of rhodamine labeled vectors. The results provide a new approach to overcome the limited stability of chitosan nanoparticles at physiological conditions and show the potential of these amphipathic chitosans as siRNA carriers. [ABSTRACT FROM AUTHOR] more...

We reported two simple rhodamine-based colourimetric sensors for the first time which can selectively and sensitively detect salicylic acid (SA) under naked-eye detection. We proposed two distinctly different modes to elucidate the possible mechanism for monitoring SA. The rationally designed probes can be well exploited in signalling SA in living cell lines. [ABSTRACT FROM AUTHOR] more...

• Al3+ and Hg2+ selective novel triphenylamine appended rhodamine derivative (TR) was synthesized • TR indicated high selectivity and sensitivity for Al3+ and Hg2+ in the presence of most metal ions • The limits of detection of TR for sensing Al3+ and Hg2+ are down to 71.8 nM and 0.48 μM, respectively • Simple test papers coated TR were successively developed for the rapid monitoring of Al3+ and Hg2+ Triphenylamine appended rhodamine (named probe TR) was built as a selective fluorescent probe for Al3+ and Hg2+ ions through different sensing mechanisms. TR demonstrated a distinct fluorescence enhancing at 501 and 580 nm towards Al3+ and Hg2+ ions due to the "PET-off" (Photoinduced electron transfer-off) and "FRET-on" (Fluorescence resonance energy transfer-on) processes, respectively. The binding modes between TR with Al3+ and Hg2+ were found to be 1:1 by job plot analysis. The limits of detection of TR for sensing Al3+ and Hg2+ are down to 71.8 nM and 0.48 μM, respectively. At the same time, the complexation details between the probe TR with Al3+ and Hg2+ ions were investigated by FTIR, 1HNMR experiments and DFT calculations. Moreover, simple test papers coated probe TR were successively developed for the rapid monitoring of Al3+ and Hg2+ ions. [ABSTRACT FROM AUTHOR] more...

While titanium‐based metal–organic frameworks (MOFs) have been widely studied for their (photo)catalytic potential, only a few TiIV MOFs have been reported owing to the high reactivity of the employed titanium precursors. The synthesis of COK‐47 is now presented, the first Ti carboxylate MOF based on sheets of TiIVO6 octahedra, which can be synthesized with a range of different linkers. COK‐47 can be synthesized as an inherently defective nanoparticulate material, rendering it a highly efficient catalyst for the oxidation of thiophenes. Its structure was determined by continuous rotation electron diffraction and studied in depth by X‐ray total scattering, EXAFS, and solid‐state NMR. Furthermore, its photoactivity was investigated by electron paramagnetic resonance and demonstrated by catalytic photodegradation of rhodamine 6G. [ABSTRACT FROM AUTHOR] more...

Cyanoacrylate fuming, rhodamine 6G staining and 532 nm laser light visualization were used to reveal a thirty-year-old fingermark on a plastic bag discovered at a double homicide scene. [ABSTRACT FROM AUTHOR] more...

A π-extended red absorbing Se-rhodamine (Se-NR) was synthesised and characterized. By masking the amine of Se-NR as an azide, we successfully constructed a bio-orthogonally activatable photosensitizer (Se-NR-Az). Se-NR-Az was not photocytotoxic, but when activated by the Staudinger reaction, photocytotoxicity was restored. [ABSTRACT FROM AUTHOR] more...

A novel mercury specifically selective and highly sensitive chemosensor SD based on Rhodamine B hydrazone derivatives had been designed and synthesized. • Sensor SD demonstrates selective "naked-eye" recognition and fluorescence "turn-on" response for Hg2+ in aqueous solution. • Sensor SD has been detected successfully Hg2+ in tap water. • Test strips of SD were prepared and convenient and rapidly detected Hg2+. A novel chemical sensor SD based on Rhodamine B hydrazide derivative was designed and synthesized, which displayed both colorimetric and "turn-on" fluorescence responses for Hg2+ in DMSO/H 2 O (1 : 9, v/v) solution. In the presence of mercury ions, the sensor SD showed an obvious change in color from colorless to distinct rose red by naked eyes and rapidly provided bright orange fluorescence under UV lamp in the aqueous solution. The detection limit on fluorescence response of SD to Hg2+ was as low as 2.71 × 10−7M. Compared to other metal ions such as Fe3+, Co2+, Ni2+, Cd2+, Pb2+, Zn2+, Cr3+, Cu2+, Ag+, Ca2+and Mg2+, SD could only selectively recognizes Hg2+.The results of the Job's plot and infrared spectra analysis suggested that the combined stoichiometry between SD and Hg2+ was 1:1. Notably, SD could be used as molecular switch controlled by EDTA and Hg2+ cyclically. In addition, SD -based test strips were produced which could be used as a convenient and efficient Hg2+ test kits. SD also could qualitatively detect Hg2+ in tap water. [ABSTRACT FROM AUTHOR] more...

Abstract Polysiloxanes have excellent stability and biological relevance and are suitable for biological research. However, there were few polysiloxane-based fluorescent probes for bioimaging. This report successfully designed a new polysiloxane-based polymer fluorescent probe (RB-1) for the first time as a "turn-on" fluorescent probe response to Al3+ ion with highly sensitive and selectivity. Importantly, this probe could also apply both in cell and zebrafish imaging, indicating the huge application development prospects of polysiloxane-based fluorescent probes in future. Graphical abstract Unlabelled Image Highlights • A novel polymer fluorescence probe RB-1 for detecting Al3+ ions was designed based on the polysiloxanes. • The fluorescent probe RB-1 could specifically detect Al3+. • The fluorescent probe RB-1 could be used in human cervical carcinoma cells (HeLa) and zebrafish. [ABSTRACT FROM AUTHOR] more...

Rhodamine and its derivatives have been widely used in designing fluorescent ‘turn on’ cation sensors, while very few rhodamine based fluorescent probes have been reported to date for the detection of anions in water. In this article, a new rhodamine based facile and convenient ‘turn on’ fluorescent chemosensor 2-(2-(1-hydroxynaphthyllideneamino)ethyl)-3′,6′-bis(diethylamino)spiro [isoindoline-1,9′-xanthen]-3-one (RAHN) has been developed by Schiff base condensation and characterized by standard techniques for selective detection of bisulfite anions in water. A faintly yellow colour solution of RAHN turns pink upon addition of bisulfite. Again RAHN is weakly emissive in solution but becomes strongly emissive on addition of bisulfite and the emission intensity increases gradually in the presence of increasing concentration of bisulfite. No other analytes can cause emission enhancement of RAHN, suggesting the selectivity of the probe towards bisulfite. The detection limit for bisulfite was found to be ∼0.4 μM. [ABSTRACT FROM AUTHOR] more...

Abstract A novel ratiometric fluorescent sensor for superoxide radical (O 2 •−) detection was developed based on Schiff base polymer (SBP)/rhodamine-B (SBP/RDB) nanocomposites. The SBP/RDB was investigated by atomic force microscopy, scanning electron microscopy, transmission electron microscopy, X-ray powder diffraction, Fourier transform infrared spectroscopy, N 2 adsorption/desorption isotherms and fluorescence spectroscopy, etc. The results showed the SBP was two-dimensional (2D) crystalline nanosheet with the thickness of 0.5 nm. RDB could be self-assembled on each of 2D SBP surface to form SBP/RDB due to the hydrogen bond between N atoms of SBP and –COOH of RDB as well as π-π interaction. The SBP/RDB exhibited the characteristic fluorescence emission of both SBP at 485 nm and RDB at 585 nm under an excitation of 270 nm. The 2D SBP was not only acted as template to assemble RDB, but also used as reference fluorescence for O 2 •− detection. The SBP/RDB fluorescence probe for O 2 •− detection demonstrated high sensitivity and selectivity with good linear range (11.1 ± 0.76 nM–8.0 ± 0.36 μM) and low detection limit (3.7 ± 0.42 nM). Because of the low cost and simple operation, the work sheds some new light to construct ratiometric fluorescent sensors based on SBP to detect O 2 •− in drinking water and human blood serum for commercial applications. Graphical abstract fx1 Highlights • A novel dual-emission Schiff base polymer/rhodamine-B (SBP/RDB) was prepared. • The Schiff base polymer was two-dimensional crystal with single atom thickness. • A SBP/RDB ratiometric fluorescent sensor detection was developed for O 2 •− detection. • The ratometric fluorescent sensor showed good performance. [ABSTRACT FROM AUTHOR] more...

Rhodamine derivatives have been persistently used as fluorescent/solvatochromic dyes in various areas. For example, they are used as a labeling agent in biotechnology and a chemosensor. Also, rhodamine derivatives are used for cell imaging experiment. Herein, we report on the synthesis of fluorescent derivatives based on rhodamine B (RHB1, RHB2, and RHB3). We confirmed the structures and purities of the synthesized probes i.e.,RHB1, RHB2, and RHB3 by using analytical technique's viz. 1H NMR, 13C NMR, Mass and FT‐IR followed by exploring spectroscopic properties by using fluorescence/UV absorption spectroscopy. The effect of solvents on the fluorescence and absorption properties of the synthesized compounds has been comprehensively studied using a series of solvent. In addition, synthesized RHB1, RHB2, and RHB3 were found to be non‐toxic against the cancer cell (MDA‐MB‐231). It is clear from the result of the conventional fluorescence microscopy that probe RHB2 exhibits significant optical properties as compared with those of RHB1 and RHB3. [ABSTRACT FROM AUTHOR] more...

Recently, great attention has been directed towards the fabrication of solar-driven nanophotocatalysts for wastewater treatment. Thus, in this work, CeO2-based nanoheterostructures were synthesized by mixing n-type CeO2 nanoparticles (NPs) with p-type Cu2S and n-type Ag2S NPs to form Cu2S/CeO2 (p–n) and Ag2S/CeO2 (n–n) nanoheterostructures, respectively. The synthesis of pristine CeO2 and CeO2-based nanoheterostructure architectures and their characterization is conducted using XRD, XPS, TEM, HRTEM, UV–Vis, N2 sorpometry, and electrochemical techniques. Pristine CeO2 NPs had a particle size of 3.9 nm and a surface area of 72.40 m2 g−1, which increased with the generation of nanoheterostructures to 12.3 and 11.1 nm and to 81.5 and 101.16 m2 g−1 for Cu2S/CeO2 and Ag2S/CeO2, respectively. Moreover, both nanoheterostructures showed strong levels of visible light absorbance relative to UV absorber pristine CeO2 NPs. Moreover, Mott-Schottky measurements were collected to determine electrochemical flat potential and band gap structures, and based on the derived results, a schematic diagram of the separation of electron–hole and insight into mechanistic routes involved are given. The photocatalytic degradation of rhodamine 6G (R6G) under natural sunlight was investigated. Based on changes in the temporal UV–Vis spectra of R6G observed over time, photocatalytic efficiencies were estimated at 23%, 44% and 30% for pristine CeO2, Cu2S/CeO2 and Ag2S/CeO2, respectively. The enhancement of the photocatalytic performance of the nanoheterostructures was attributed to the generation of p–n and n–n heterojunction arrangements, which facilitated photogenerated charge separation and transfer. [ABSTRACT FROM AUTHOR] more...

Although fluorescence detection is a sensitive method in the field of pollutant analysis, its application is restricted due to the fluorescence shown by organic material being quenched after aggregation and to low photo-thermal stability. To address these issues, a novel mineral/dye composite material was prepared by intercalating a fluorescence molecule, Rhodamine (R6G), into the interlayer space of montmorillonite (Mnt). This composite material greatly enhanced the light stability and efficiency of R6G. After enhancement, the fluorescence lifetime of R6G-Mnt was eight times longer than originally and the luminous intensity was 20 times greater. Chromium at the mmol/L (mM) level can be detected by the naked eye when its enhanced fluorescent property is fabricated into a solid test paper, even though a fluorescence spectrophotometer should be used for detection at the 0.01 μmol/L level in the sensing range 0.01 μmol/L to 100 mmol/L. These results can provide new avenues as well as a theoretical and experimental foundation for the development of novel supramolecular luminescent material. [ABSTRACT FROM AUTHOR] more...

A novel fluoro-chromogenic rhodamine spirolactam probe (RP) has been prepared through the condensation of rhodamine hydrazine and 2-acetylpyridine, which displayed the detection of Cu2+ with high selectivity over a large number of other common metal ions. It shows a "turn-on" response to paramagnetic Cu2+ with an about 12-fold enhancement, and a color change from colorless to red that is observable by the naked eye. These changes are ascribed to the ring-opening of the spirolactam in RP, and subsequent host–guest coordination. The 2:1 binding stoichiometry of RP to Cu2+ was confirmed by Job's and B-H plots. The resulting fluorescence enhancement can be used to detect Cu2+ at concentrations from 2.0 to 20.0 μM with a limit of detection of 0.21 μM, which was lower than the maximum allowable Cu2+ level set by the WHO. Finally, RP has been utilized to monitor Cu2+ in living cells and natural water. [ABSTRACT FROM AUTHOR] more...

Abstract Nitric oxide (NO) plays vital roles in many physiological process and is closely related to many diseases. So far, a number of fluorescent probes have been constructed for the detection of NO successfully. However, the probes still suffer from long-time reaction and limited selectivity. Herein, a fluorescent probe named dRB-OPD is synthesized and used to recognize NO. The probe contains a deoxy-rhodamine B as fluorophore and o-phenylenediamino as reaction site. dRB-OPD shows fast response to NO within 40 s with 170-fold fluorescence enhancement. Moreover, the probe shows high selectivity towards NO over dehydroascorbic acid (DHA), ascorbic acid (AA), and methylglyoxal (MGO). Particularly, the probe can avoid the serious interference from cysteine (Cys) found in the rhodamine lactam-based fluorescent NO probes (RB-OPD). In addition, the probe is applied for the detection of exogenous and endogenous NO in the HepG2 and RAW 264.7 cells with satisfactory results. Graphical abstract fx1 Highlights • A fluorescent probe named dRB-OPD is synthesized and used to recognize NO. • The probe has fast response to NO within seconds (< 40 s). • The probe shows high selectivity towards NO over DHA, AA, and MGO. • dRB-OPD can avoid the serious interference from cysteine (Cys) found in RB-OPD. • The probe is used for monitoring exogenous and endogenous NO in living cells. [ABSTRACT FROM AUTHOR] more...

Abstract A device was designed integrating solid phase extraction (SPE) and in situ optical detection techniques. A chip assembled in the device to carry out SPE was enclosed in a fully reflective aluminum box to avoid loss of radiation flux in the optical measurement. The spectrum was measured on the SPE material directly after SPE. The device offers simple analytical operation without any elution step comparing with the traditional analytical methods with complicated procedures. The device and the developed analytical technique was used for the determination of rhodamine B and benzo[ a ]pyrene with UV–visible diffuse reflectance and solid phase fluorescence spectroscopies, respectively. Under optimal conditions, standard curves of rhodamine B and benzo[ a ]pyrene showed a linear relationship in concentration ranges of 10–800 μg L-1 (R2 = 0.99) and 0.07–3.33 μg L-1 (R2 = 0.99), respectively. The limit of detections (LOD) were 7 μg L-1 and 0.02 μg L-1. The proposed device was successfully employed to quantify rhodamine B and benzo[ a ]pyrene in tap water samples. The results showed that the recoveries were 90–105% and the relative standard deviations (RSDs) were 2.53–5.55%, indicating that the device and analytical method is capable of trace analytes for rapid quantitative analysis in various samples. Graphical abstract fx1 Highlights • A device was designed integrating SPE and in situ optical detection techniques. • The spectrum was measured on the SPE material directly after SPE. • The device offers simple analytical operation without any elution step. • The developed device and technique can be used at μg L-1 and ng L-1 levels. [ABSTRACT FROM AUTHOR] more...

The molybdenum oxide and graphene oxide (MoO2/GO) nanocomposite has been fabricated via simple hydrothermal assisted synthesis using Mo and MoO3 as precursors. The MoO2 nanospheres with porous hollow structure are assembled onto GO nanosheets. Profiting from the plasmonic effects of MoO2 and synergistic effect of MoO2 and GO, this hybrid nanomaterial exhibits significantly enhanced surface enhanced Raman scattering (SERS) activity for organic pollutants. The detection limit for rhodamine 6G (R6G) is 1.0 × 10−9 M, and the maximum enhancement factor (EF) reaches up to 1.05 × 107, which is the best among the semiconductor-based SERS materials. For practical application, the MoO2/GO SERS substrates are also applied to detect Methylene blue (MB) in river water, and the detection limit (1.0 × 10−8 M) can be acquired. Pyrene is also chosen as probe molecule, and quantitative determination is achieved with detection limit of 1.0 × 10−7 M. These demonstrate the well feasibility for multi-molecule detection. Furthermore, the nanocomposite displays high stability, reproducible stability, and acid and alkali resistance. [ABSTRACT FROM AUTHOR] more...

A simple rhodamine-based fluorescent probe L1, which exhibits good response to Fe3+ in CH3CN/Tris-HCl buffer (v:v = 9:1, pH 7.00) solution. With the experimental conditions optimized, the probe L1 could be used as a fluorescent and colorimetric probe for Fe3+ with the detection limit as low as 0.29 μM. The binding constant (Ka) of Fe3+ binding to the probe L1 were calculated to be 1.4 × 1010 M−2, respectively from a Benesi-Hildebrand plot. With the addition of Fe3+, the CH3CN/Tris-HCl buffer (v:v = 9:1, pH 7.00) solution of the probe L1 exhibited a obviously color change from transparent to pink with distinctive changes. More importantly, the recognition process of the probe L1 for Fe3+ was chemically reversible on the addition AcO−. [ABSTRACT FROM AUTHOR] more...

Graphical abstract Highlights • Development of a sensitive chemiluminescence (CL) detection method for tramadol. • Encapsulation of Cu nanoclusters in 2D Cu metal-organic frameworks (CuNCs@CuMOF). • Tremendous enhancing effect of CuNCs@CuMOF on CL emission of rhodamine 6G (R6G). • Increasing effect of tramadol on the CL emission of R6G-KMnO 4 -CuNCs@CuMOF system. • Extraction of tramadol using magnetic MIP-Fe 3 O 4 @SiO 2 NPs, before the CL analysis. Abstract Herein, a high performance chemiluminescence (CL) system is developed for the sensitive detection of tramadol. The CL reaction is based on the direct oxidation of rhodamine 6 G (R6 G) by potassium permanganate (KMnO 4), producing an ultra-weak emission. It was found that copper nanoclusters encapsulated in copper-based two-dimensional metal-organic frameworks (CuNCs@CuMOF) create a tremendous enhancing effect on the observed emission. A probable mechanism was also suggested for CL emission based on the catalytic effects of nanomaterial and chemiluminescence resonance energy transfer (CRET) events. Besides, it was observed that tramadol caused a relatively selective increasing effect on the CL emission of R6 G-KMnO 4 -CuNCs@CuMOF system. In order to guarantee a selective response for tramadol, an extraction process using molecularly imprinted polymer modified Fe 3 O 4 @SiO 2 nanoparticles (MIP-Fe 3 O 4 @SiO 2 NPs) was applied before the CL analysis. The dispersed MIP-Fe 3 O 4 @SiO 2 NPs showed high specificity for the extraction of tramadol from its samples. The combination between the high improved CL detection system and the efficient extraction process caused an ultrasensitive and selective determination method for tramadol. The best linear calibration graph was obtained in the concentration range of 0.0030–2.5 μM tramadol, with a detection limit (3S b /m) of 0.80 nM. The illustrated CL method was tested for the quantification of tramadol in biological fluids, which led to the acceptable and reliable results. [ABSTRACT FROM AUTHOR] more...

Graphical abstract Highlights • "Always-on" and "water-soluble" rhodamine amide based on o -pyridinium was designed and synthesized. • A strategy inspired by rhodamine spirolactam probes for metal ions was used. • o -RPM maintained ring-opening state in broad pH values (3.5–13.0) and aprotic/protic solvents. • IR and NMR spectrum confirmed the ring-opening state of o -RPM induced by positive charge. • o -RPM exhibited excellent water-solubility and mitochondrion-specificity for living cells. Abstract Inspired by the ring-opening reaction of rhodamine probe induced by metal ions, we proposed a positive charge regulating strategy and designed an "always-on" and "water-soluble" fluorescent probe (o -RPM) based on rhodamine amide bearing o -pyridinium. To our knowledge, o -RPM was the first always-on opening form of spirolactam which can endure broad pH range (pH 3.5–13.0) and aprotic environment. IR and NMR spectrum were used to assess the distribution of conjugation system induced by positive charge in pyridinium moiety. The geometries of o -RPM were calculated using Gaussian software at DFT/B3LYP/6-31 G(d) level. The always-on opening form of o -RPM should be attributed to inductive and conjugation effects resulting from proximal positive charge. Meanwhile, positive charge contributed to the dissolution of o -RPM in aprotic and/or protic solvents. In addition, always-on and water-soluble o -RPM exhibited excellent membrane penetration, and was successfully used as a specific tracker to map the mitochondrial distributions in living MCF-7 cells, due to the nature characteristic of positive charge. It is anticipated that the strategy of ring-opening form of rhodamine spirolactam induced by positive charge might be hopeful to regulate the "on-off-on" state of spirolactams in the biomedical and biological fields. [ABSTRACT FROM AUTHOR] more...