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In this paper, based on the fluorescence of carbon quantum dots (CQDs) quenched by mercury ions (Hg2+ ) and the nonresponse of Hg2+ to rhodamine B fluorescence, a dual emission ratio fluorescence sensor was constructed to realize the quantitative detection of Hg2+ . Under excitation at 365 nm, the fluorescence spectrum showed double emission peaks at 437 nm and 590 nm, corresponding to the fluorescence emissions of CQDs and rhodamine B, respectively. This method quantitatively detected Hg2+ based on the linear relationship between the ratio of the intensities of the two emission peaks F437 /F590 and the concentration of Hg2+ . The detection range was 10-70 nM, and the limit of detection (S/N = 3) was 3.3 nM. In addition, this method could also realize the qualitative and semiquantitative detection of Hg2+ according to the fluorescence colour change of the probe under ultraviolet light. After various evaluations, the method could be successfully applied to the quantitative and visual detection of Hg2+ in tap water, and demonstrated excellent selectivity, anti-interference performance, and repeatability of the method.

An ultrahigh supramolecular cascaded phosphorescence-capturing aggregate was constructed by multivalent co-assembly of cucurbit[7]uril (CB[7]) and amphipathic sulfonatocalix[4]arene (SC4AD). The initial dibromophthalimide derivative (G) generated a weak phosphorescent emission at 505 nm by host-guest interaction with CB[7], which further assembled with SC4AD to form homogeneously spherical nanoparticles with a dramatic enhancement of both phosphorescence lifetime to 1.13 ms and emission intensity by 40-fold. Notably, this G⊂CB[7]@SC4AD aggregate exhibited efficient phosphorescence energy transfer to Rhodamine B (RhB) and benzothiadiazole (DBT) with high efficiency (ϕET ) of 84.4 % and 76.3 % and an antenna effect (AE) of 289.4 and 119.5, respectively, and then each of these can function as a bridge to further transfer their energy to second near-IR acceptors Cy5 or Nile blue (NiB) to achieve cascaded phosphorescence energy transfer. The final aggregate with long-range effect from 425 nm to 800 nm and long-lived photoluminescence was further employed as an imaging agent for multicolour cell labeling.

Wastewater treatment is of great significance to environmental remediation. The exploration of efficient and stable methods for wastewater treatment is still a challenging issue. Herein, a heterojunction material with photocatalysis and adsorption properties has been designed to remove the complex pollutants from wastewater. The heterojunction material (ZnO/TiO2 -PW12 , PW12 =[PW12 O40 ]3- ) was synthesized by calcining the ZnTi-layered double hydroxide (ZnTi-LDH) intercalated with the Keggin-type polyoxometalate H3 PW12 O40 . In the construction of ZnO/TiO2 -PW12 it was found that the polyanionic PW12 remained unchanged in the process of forming the proposed heterojunction. The photochemical properties verify that heterojunction synergistic with PW12 facilitated the separation of photoproduced electron-hole pairs and thus suppressed the recombination. Therefore, ZnO/TiO2 -PW12 exhibits excellent photocatalytic property, and the efficiency of Cr(VI) photoreduction reached more than 90 % in the first 3 min. Furthermore, the electrostatic force between the PW12 and cationic dyes makes ZnO/TiO2 -PW12 having an outstanding adsorption performance for cationic dyes, such as rhodamine B, crystal violet and methyl blue. Such heterojunction material combined with polyoxometalate puts forward new insights for the design of functional materials for water treatment with low cost and high efficiency.

This study evaluated tubule penetration of GuttaFlow Bioseal with cold single cone or carrier-based technique, under confocal laser scanning microscopy (CLSM). Twenty straight single-rooted teeth were instrumented with Hyflex CM and divided in two groups (n = 10) according to the obturation method: single cold gutta-percha cones; experimental carrier-based obturators. GuttaFlow Bioseal, labelled with Rhodamine B dye, was used as sealer in both groups. Teeth transversally sectioned were observed under CLSM. Percentage of sealer penetration and integrity of sealer layer perimeter were measured. Surface and microstructural characteristics of obturators and gutta-percha cones were compared by FEG-SEM and EDX analysis. No significant differences were found between groups for each examined parameter. Significant differences (P < 0.05) were reported mainly within groups. Integrity was similar among and within groups. FEG-SEM/EDX analysis of obturators revealed the presence of Ba and Zn. Carrier-based obturation technique associated with GuttaFlow Bioseal does not seem to affect sealer penetration into dentinal tubules.

The use of acid-modified mango pod (AMMP) sorbent for removing Rhodamine B (Rh-B) dye from aqueous media was investigated. Raw mango pod (RMP) and AMMP sorbents were characterized using scanning electron microscopy (SEM), energy dispersive X-ray (EDX), powdered X-ray diffractogram (PXRD), Fourier transform infrared (FTIR), point of zero charge pH (pHpzc ), and Boehm titration (BT) techniques. Batch adsorption was employed to examine the influence of operational factors. Sorption kinetic parameters were calculated using pseudo-first-order, pseudo-second-order, Elovich, and intraparticle diffusion models. The pseudo-second-order model best fitted the adsorption kinetic data most with maximum correlation coefficient (R2 > 0.99). The process of the adsorption was controlled by both boundary layer and intraparticle diffusion mechanisms. Four isotherm models (Langmuir, Freundlich, Dubinin-Radushkevich, and Temkin) were utilized to analyze the equilibrium data at various temperatures. Freundlich model gave the best fit with the maximum regression (0.99), while the Langmuir isotherm model established a maximum monolayer adsorption capacity of 500 mg g-1 . Thermodynamic parameters studied revealed that the interaction is spontaneous and endothermic in nature. The cost analysis of the current study provides convincing proof that AMMP is efficient for removing Rh-B dye from solution by providing a saving of 225.2 USD/kg, which is eight times cheaper than commercial activated carbon. Consequently, the study revealed that AMMP is a viable, effective, and sustainable sorbent for Rhodamine B dye removal. PRACTITIONER POINTS: The powdered X-ray diffractogram (PXRD) showed the formation of new and intense peaks with the presence of highly organized crystalline structures on acid-modified mango pod (AMMP). Surface morphology of AMMP showed well-developed open surface pores required for effective adsorption of Rh B dye molecules. Economic feasibility of the present study showed that AMMP is more affordable than commercial activated carbon that costs USD 259.5/kg, thus translated to a saving cost of USD 225.2/kg and more than 7.5 times cheaper than the commercial activated carbon (CAC).

Interfacial modular assembly has emerged as an adaptable strategy for engineering the surface properties of substrates in biomedicine, photonics, and catalysis. Herein, we report a versatile and robust coating (pBDT-TA), self-assembled from tannic acid (TA) and a self-polymerizing aromatic dithiol (i.e., benzene-1,4-dithiol, BDT), that can be engineered on diverse substrates with a precisely tuned thickness (5-40 nm) by varying the concentration of BDT used. The pBDT-TA coating is stabilized by covalent (disulfide) bonds and supramolecular (π-π) interactions, endowing the coating with high stability in various harsh aqueous environments across ionic strength, pH, temperature (e.g., 100 mM NaCl, HCl (pH 1) or NaOH (pH 13), and water at 100 °C), as well as surfactant solution (e.g., 100 mM Triton X-100) and biological buffer (e.g., Dulbecco's phosphate-buffered saline), as validated by experiments and simulations. Moreover, the reported pBDT-TA coating enables secondary reactions on the coating for engineering hybrid adlayers (e.g., ZIF-8 shells) via phenolic-mediated adhesion, and the facile integration of aromatic fluorescent dyes (e.g., rhodamine B) via π interactions without requiring elaborate synthetic processes.

Meso-N-TiO2 nanocatalysts (Nx-MT) were successfully synthesized through evaporation-induced self-assembly (EISA) method by using urea as the nitrogen source and Pluronic F127 as the templating agent. Through a series of characterizations and degradation of rhodamine B under simulated sunlight, the roles of mesoporous and N-doping in the Nx-MT nanocatalyst were evaluated. The Nx-MT exhibited enhanced photocatalytic activity due to the comprehensive effect of mesopores and N-doping. The effects of calcination temperature and N concentration on the performance of the catalyst were studied. Besides, the relationship between the pore volume of Nx-MT and the catalytic reaction rate was clarified. Moreover, the turn-over number (TON) was used to evaluate the effect of the amount of nitrogen doping on the catalytic activity per active site.

Simultaneous visualization and concentration quantification of molecules in biological tissue is an important though challenging goal. The advantages of fluorescence lifetime imaging microscopy (FLIM) for visualization, and electron paramagnetic resonance (EPR) spectroscopy for quantification are complementary. Their combination in a multiplexed approach promises a successful but ambitious strategy because of spin label‐mediated fluorescence quenching. Here, we solved this problem and present the molecular design of a dual label (DL) compound comprising a highly fluorescent dye together with an EPR spin probe, which also renders the fluorescence lifetime to be concentration sensitive. The DL can easily be coupled to the biomolecule of choice, enabling in vivo and in vitro applications. This novel approach paves the way for elegant studies ranging from fundamental biological investigations to preclinical drug research, as shown in proof‐of‐principle penetration experiments in human skin ex vivo., A novel multi‐label synthetic platform for a functional dual fluorescence–spin label probe enables the non‐destructive simultaneous quantification and visualization of molecules in biological tissue. Multiplexed FLIM and EPR spectroscopy avoids analytical inconsistencies between both techniques. Beside tissue applications, molecular spectroscopic studies of biomolecular conformation, structure, dynamics, and microenvironment are feasible.

NIR and UV exposure of systems comprising upconversion nanoparticles (UCNP) based on NaYF4:Tm/Yb@NaYF4, a sensitizer absorbing either in the blue or UV region, and an onium salt with weak coordinating anion resulted in formation of conjugate acid (con‐H+). That was namely Ivocerin (di(4‐methoxybenzoyl)diethylgermane), ITX (2‐iso‐propyl thioxanthone), anthracene, pyrene, rubrene, camphore quinone, and a strong fluorescent coumarin (1,1,6,6,8‐pentamethyl‐2,3,5,6‐tetrahyhdro‐1H,4H‐11‐oxa‐3a‐aza‐benzo[de]anthracene‐10‐one). Quantification occurred by treatment with Rhodamine B lactone whose color switched to intensive red after photolytic formation of con‐H+. Exposure with a NIR laser at 980 nm resulted in less con‐H+ compared to 395 nm where all sensitizers absorb radiation. UCNP did not mainly interfered formation of con‐H+. The different rates obtained in both experiments responsibly explain the failure and success to initiate polymerization of epoxides applying ether 980 nm or 395 nm excitation, respectively., Make it acidic with long wavelength invisible light: Upconversion nanoparticles generate blue and UV light needed to excite a sensitizer absorbing in the UV or blue whose reaction with an onium salt results in conjugate acid. Rhodamine B lactone helps to quantify it and gives a drawback for initiation of cationic polymerization. Different efficiencies were found appearing in distinct deep red color.

Two photoswitchable arylazopyrozoles form hydrogels at a concentration of 1.2 % (w/v). With a molecular weight of 258.28 g mol-1 , these are the lowest known molecular weight hydrogelators that respond reversibly to light. Photoswitching of the E- to the Z-form by exposure to 365 nm light results in a macroscopic gel→sol transition; nearly an order of magnitude reduction in the measured elastic and loss moduli. In the case of the meta-arylazopyrozole, cryogenic transmission electron microscopy suggests that the 29±7 nm wide sheets in the E-gel state narrow to 13±2 nm upon photoswitching to the predominantly Z-solution state. Photoswitching for meta-arylazopyrozole is reversible through cycles of 365 nm and 520 nm excitation with little fatigue. The release of a rhodamine B dye encapsulated in gels formed by the arylazopyrozoles is accelerated more than 20-fold upon photoswitching with 365 nm light, demonstrating these materials are suitable for light-controlled cargo release.

A series of carbon‐coated, nitrogen‐doped titanium dioxide photocatalysts was produced and characterized. N‐doped TiO 2 powder samples were prepared using a sol‐gel method and subsequently used for making stable doped‐TiO 2 thin films on glass substrates. Carbon layers were coated on the films by a thermal decomposition method using catechol. Diffuse reflection spectra and Mott‐Schottky analyses of the samples proved that nitrogen doping and carbon coating can slightly lower the band gap of TiO 2 , broaden its absorption to visible light and enhance its n‐type character. According to photocatalytic tests against model contaminants, carbon‐coated nitrogen‐doped TiO 2 films have better performance than simple TiO 2 on the degradation of Rhodamine B dye molecules, but are poorly effective for degrading 4‐chlorophenol molecules. Several possible explanations are proposed for this result, supported by scavenging experiments. This reveals the importance of a broad substrate scope when assessing new photocatalytic materials for water treatment, something which is often overlooked in many literature studies.

The aim of this work was to optimize the photocatalytic degradation of rhodamine B (RhB) using a four-factor Box-Behnken experimental design, and the study was carried out under artificial irradiation (24-W UV lamp) using ZnO in suspension. The Box-Behnken model has been validated with an error less than 5%. A total (100%) RhB removal and COD abatement rates were reached under optimal conditions of treatment time, ZnO dose, and stirring speed at different concentrations of dye. The study of the effect of irradiation type (solar and UV lamp) on the degradation of RhB showed that solar irradiation gave a better rate of degradation with complete discoloration after 2 hr. The study of RhB degradation mechanism indicates that O 2 ∙ - were the main active species for the degradation of this pollutant. The comparison between the degradation of RhB alone and RhB prepared with varnish (as it is usually used in industry) revealed that degradation of RhB alone is faster comparing than that of RhB/varnish mixture. The results showed that the biodegradability was improved after a contact time of 60 min with a BOD5 /COD ratio increasing from 0.23 to 0.90. PRACTITIONER POINTS: Optimization of the photocatalytic degradation of rhodamine B using a four-factor Box-Behnken experimental design. Investigation of dye mineralization. The degradation mechanism of rhodamine. Biodegradability assessment based on the BOD5 /COD ratio.

In this study, a rhodamine-acetylferrocene conjugate of RBFc was synthesized and then characterized using spectroscopy and single-crystal analysis. The chemosensor RBFc exhibited a marked colour change from colourless to pink after binding to Cu2+ ions. Importantly, under the presence of the other competing cations in aqueous solution, only Cu2+ ions caused spirolactam ring opening in rhodamine B in RBFc, resulting in an enhanced absorbance of ultraviolet light spectra and fluorescence spectra, as well as obvious shifts in cyclic voltammetry curves and differential pulsed voltammetry curves. The novel probe described in this manuscript provides an attractive approach for detecting Cu2+ in the presence of other multisignals.

The unique two-dimensional structure and surface chemistry of reduced graphene oxide (rGO) along with its high electrical conductivity can be exploited to modify the electrochemical properties of ZnO nanoparticles (NPs). ZnO-rGO nanohybrids can be engineered in a simple new two-step synthesis, which is both fast and energy-efficient. The resulting hybrid materials show excellent electrocatalytic and photocatalytic activity. The structure and composition of the as-prepared bare ZnO nanorods (NRs) and the ZnO-rGO hybrids have been extensively characterised and the optical properties subsequently studied by UV/Vis spectroscopy and photoluminescence (PL) spectroscopy (including decay lifetime measurements). The photocatalytic degradation of Rhodamine B (RhB) dye is enhanced using the ZnO-rGO hybrids as compared to bare ZnO NRs. Furthermore, potentiometry comparing ZnO and ZnO-rGO electrodes reveals a featureless capacitive background for an Ar-saturated solution whereas for an O2 -saturated solution a well-defined redox peak was observed using both electrodes. The change in reduction potential and significant increase in current density demonstrates that the hybrid core-shell NRs possess remarkable electrocatalytic activity for the oxygen reduction reaction (ORR) as compared to NRs of ZnO alone.

Microwave-solvothermal synthesized MIL-101(Fe) was successfully loaded by silver halides (AgCl and AgBr) by simple precipitation method. The XRD, FESEM mapping, XPS and DRS measurements reveal the successful fabrication of composite photocatalyst. The results suggested that silver halides altered surface charge, surface area and pore size distribution of MIL-101(Fe). The 20%AgBr@MIL-101(Fe) composite has strong tendency to remove the cationic/anionic dyes (96% of rhodamine B, 100% of malachite green and 92% of methyl orange) from wastewater after 30 min of adsorption and 90 min under visible light irradiation. The composite photocatalyst revealed the photodegradation stability up to four cycles. The formation of mesopores improves the adsorption ability of the composites for large organic molecules, while loaded silver halides might inhibit the recombination of electron-hole pairs; those were responsible for enhancing the photocatalytic degradation of organic pollutants. ESR suggested O 2 · - , · OH were responsible for dye degradation in visible light by composite photocatalysts. The photocatalytic mechanism of the composite was also explained in this work.

BACKGROUND: The importance of potable water is immeasurable and its contamination by pollutants is a serious environmental problem. Rhodamine B (RhB), one such pollutant, is highly toxic to various organisms and may cause long‐term undesirable effects when improperly disposed of. Thus, development of an efficient treatment technique is necessary. Among the new oxidation methods, heterogeneous photocatalysis is an emerging pollutant destructive technology. RESULTS: The photocatalytic activities of copper (Cu) and zinc (Zn) aluminate spinels (CuAl₂O₄ and ZnAl₂O₄) was evaluated. Chemical and physical properties were considered, and ZnAl₂O₄ showed higher RhB degradation efficiency (73.90% in only 10 min) than CuAl₂O₄ (51.95% in 10 min), reaching up to 100% in 30 min. According to results, a further RhB catalytic degradation pathway by ZnAl₂O₄ was monitored by UV‐visible spectrometry and ultra‐high performance liquid chromatography coupled to diode array detection (UHPLC‐DAD) analysis. When applied to wastewater from gemstone beneficiation, containing elevated RhB concentration, the ZnAl₂O₄ caused 88% color removal in 120 min and its pollutant removal rate was 18 times greater than the commonly used ZnO. CONCLUSION: The superior performance of ZnAl₂O₄ can be attributed to better pore properties, responsible for providing more active sites. These identified reactive oxygen species (ROS)‐induced interactions and the species demonstrated that degradation occurs due to generation of O₂•‐ and h⁺. Thus, ZnAl₂O₄ proved to be an efficient photocatalyst for quick RhB pollutant degradation with promising potential for real wastewater treatment applications. © 2019 Society of Chemical Industry

Supramolecular organisation and self-assembly are the pillars of functionality of many nanosystems. The covalent conjugate (6-spirolactam rhodamine B-6-monodeoxy)-β-cyclodextrin ( Rho- β CD ) is assembled as a self-included, rigid nanostructure, identical in the crystal and in aqueous solution, as revealed by detailed X-ray and NMR analyses. Rho- β CD self-assembly is the result of an interesting reaction pathway which partially de-aggregates Rho and disturbs the zwitterion↔spirolactone equilibrium. Rho- β CD is stable at pH 4.6 but displays controllable photoswitching between the coloured, fluorescent, zwitterionic and the colourless, non-fluorescent closed structures, during several iterative cycles. After an initial drop in absorbance, the on-off process continues without further changes under our irradiation conditions, a consequence of the specific self-locked arrangement of Rho in the cavity. Rho-βCD exemplifies a water soluble photoresponsive nanosystem with improved photostability suggesting promising applications in super resolution bioimaging.