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The synthesis and characterization of a novel trinuclear rhodamine‐Gd(III) complex, along with two analogous mononuclear rhodamine‐Gd(III) complexes, are reported. All complexes displayed good selectivity in a human glioma cell line (T98G) when compared to a glial cell line (SVG p12), with low cytotoxicities. Superior tumor cell uptake for these Gd(III) complexes was observed at lower incubation concentrations compared to previously‐reported delocalized lipophilic cations such as a rhodamine‐lanthanoid(III) probe and Gd(III)‐arylphosphonium complexes, with ca. 150 % and 250 % increases in Gd uptake, respectively. [ABSTRACT FROM AUTHOR]

Effects of xanthene dyes and aerosil nanoparticles on the structure and dynamic characteristics of the cross-linked polyurethane were investigated by the IR-spectroscopy, dynamic-mechanical analysis, and electronic paramagnetic resonance methods. Dye molecule presence causes self-association of urethane groups within polymer rigid segments, weaker interactions between urethane groups and flexible oligoether parts and increased oligoether mobility. Increased mobility of flexible segments by xanthene dyes provides the necessary beam strength due to compensating the nanofiller network effect. The most efficient polyurethane material in the radiation resistance is expected to be a polymer composite with the highest permeability and the lowest modulus of elasticity. [ABSTRACT FROM AUTHOR]

A kind of novel catalyst Co-Fe@GAC was prepared by the method of impregnation-calcination with cobalt and iron oxides attached onto granular activated carbon (GAC), and microscopic morphology and structure of the catalyst were analyzed by scanning electron microscopy and X-ray diffraction. Then the laboratory experiment was conducted focusing on examining the effects of degrading Rhodamine B (RhB), a representative organic pollutant, by peroxymonosulfate (PMS) that was activated by Co-Fe@GAC in different circumstances including co-existing ions and humic acids contained in the system. The experiment revealed that by increasing the dosage of Co-Fe@GAC catalysts and PMS concentration it could significantly improve the removal efficiency of RhB, and the system also showed a good degradation performance in a wide-range of pH, in addition, with interference resistance; and the oxidative species quenching test indicated that both hydroxyl radicals and sulphate radicals (SO4•-) existed in the Co-Fe@GAC/PMS system, and SO4•- was the dominant radical in RhB degradation. Besides, Co-Fe@GAC, being re-usable, was considerable stable in terms of catalytic performance. [ABSTRACT FROM AUTHOR]

Single‐molecule localization microscopy (SMLM) has found extensive applications in various fields of biology and chemistry. As a vital component of SMLM, fluorophores play an essential role in obtaining super‐resolution fluorescence images. Recent research on spontaneously blinking fluorophores has greatly simplified the experimental setups and extended the imaging duration of SMLM. To support this crucial development, this review provides a comprehensive overview of the development of spontaneously blinking rhodamines from 2014 to 2023, as well as the key mechanistic aspects of intramolecular spirocyclization reactions. We hope that by offering insightful design guidelines, this review will contribute to accelerating the advancement of super‐resolution imaging technologies. [ABSTRACT FROM AUTHOR]

Although the syntheses and applications of rhodamine dyes have been extensively researched, their photophysical properties and photostability have rarely been studied. In this study, we systematically investigated the photophysical properties and photostability of six rhodamine dyes by the spectrum measurements, photodegradation experiments and theoretical calculations. It was found that the following structural modifications can lead to the redshift of absorption and fluorescence emission spectra: increasing the alkyls of amino on xanthene; forming rigid ring between the N-linked alkyl and xanthene; and esterification of –COOH on benzene ring. The degradation experiments under 525-nm light irradiation indicated that increasing the alkyls of amino on xanthene improves the photostability, fixing the N-linked alkyls on the xanthene ring to form rigid rings significantly reduces the photostability of rhodamine dyes, and the esterification of –COOH on benzene ring can increase their photostability to some extent. The results of DFT calculations showed that the esterification of –COOH decreases the dihedral angle D1 and increases D2, the variation trends of calculated absorption and emission wavelengths are consistent with the measured results, and the rhodamine dyes with higher electrophilic index usually have higher photostability. [ABSTRACT FROM AUTHOR]

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• 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]

• 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]

It is still challenging to clarify the intrinsic relationship between the photostability and molecular structures of rhodamine dyes. Herein, we investigated the photostability of three rhodamine dyes RhB, Rh101, and Rh101-ME in water and 20%EtOH–H 2 O solutions under 525 nm LED light irradiation. The photostability of RhB is much higher than that of Rh 101 and Rh101-ME, indicating that forming rigid ring between the N-linked alkyl and xanthene can significantly decrease the photostability of rhodamine dyes, while the esterification of carboxyl on benzene ring can improve their photostability. The EPR analyses and radical trapping experiments proved that 1O 2 is the most important reactive oxygen species responsible for dye degradation, and the Rh101 and Rh101-ME have higher 1O 2 and •OH production rates than RhB. The cyclic voltammetry tests showed that forming rigid ring between the N-linked alkyls and xanthene can decrease the oxidation potential of RhB and consequently lower down its photostability. The theoretical calculations disclosed that the higher HOMO energy levels in ground states and lower singlet–triplet energy gaps of Rh101 and Rh101-ME are the main factor that results in their lower photostability when compared with RhB. Forming rigid ring between the N-linked alkyl and xanthene of rhodamine dyes significantly decreases the photostability of rhodamine dyes, which is related to the structure distortion on the twisted intramolecular charge transfer (TICT). In addition, the esterification of –COOH on benzene ring improves the photostability to some extent. [Display omitted] • The influence of rhodamine molecular structures on their photostability was investigated. • Forming rigid ring between N-linked alkyl and xanthene reduces the photostability of rhodamine dye. • Esterification of carboxyl acid on benzene ring can improve the photostability of rhodamine dyes. • 1O 2 is the most important reactive oxygen species responsible for rhodamine dye degradation. • The calculation reveals that the photostability of dyes is related to their S 0 energy levels and T 1 energy gaps. [ABSTRACT FROM AUTHOR]

Rhodamine derivatives have been widely investigated for their mitochondrial targeting and chemotherapeutic properties that result from their lipophilic cationic structures. In previous research, we have found that conversion of Rhodamine 6G into nanoGUMBOS, i.e., nanomaterials derived from a group of uniform materials based on organic salts (GUMBOS), led to selective chemotherapeutic toxicity for cancer cells over normal cells. Herein, we investigate the chemotherapeutic activity of GUMBOS derived from four different rhodamine derivatives, two bearing an ester group, i.e., Rhodamine 123 (R123) and SNAFR-5, and two bearing a carboxylic acid group, i.e., rhodamine 110 (R110) and rhodamine B (RB). In this study, we evaluate (1) relative hydrophobicity via octanol–water partition coefficients, (2) cytotoxicity, and (3) cellular uptake in order to evaluate possible structure–activity relationships between these different compounds. Intriguingly, we found that while GUMBOS derived from R123 and SNAFR-5 formed nanoGUMBOS in aqueous medium, no distinct nanoparticles are observed for RB and R110 GUMBOS. Further investigation revealed that the relatively high water solubility of R110 and RB GUMBOS hinders nanoparticle formation. Subsequently, while R123 and SNAFR-5 displayed selective chemotherapeutic toxicity similar to that of previously investigated R6G nanoGUMBOS, the R110 and RB GUMBOS were lacking in this property. Additionally, the chemotherapeutic toxicities of R123 and SNAFR-5 nanoGUMBOS were also significantly greater than R110 and RB GUMBOS. Observed results were consistent with decreased cellular uptake of R110 and RB as compared to R123 and SNAFR-5 compounds. Moreover, these results are also consistent with previous observations that suggest that nanoparticle formation is critical to the observed selective chemotherapeutic properties as well as the chemotherapeutic efficacy of rhodamine nanoGUMBOS.

Abstract Based on the laser induced fluorescence technology, the Fluorescence characteristics of two dyes Rhodamine 6G (R6G) and Rhodamine B (RB) in two anionic surfactants (AS) sodium dodecylsulpfate (SLS) and sodium 1-dodecanesulfonate (SDS) are experimentally investigated and compared in detail for different concentrations of dyes and ASs. The results show that the two ASs can weaken or enhance the fluorescence of the two dyes depending on different concentrations of dyes and ASs. In our experiment, the maximal fluorescence enhancement factors can be up to 30.1325, 15.6099, 20.0699, and 2.4403, for RB in SLS, RB in SDS, R6G in SLS, and R6G in SDS, respectively. In comparison with SDS, SLS is more efficient in fluorescence enhancement of the two dyes. Moreover, RB fluorescence can be enhanced more intensely. While SDS mostly decreases the fluorescence of R6G under our parameter conditions. The peak wavelengths of fluorescence spectra generally red-shift with increase of dye concentrations whereas red-shift first and blue-shift and then tend to fundamental stability with increase of AS concentrations. [ABSTRACT FROM AUTHOR]

Abstract Microwave-assisted organic synthesis (MAOS) has been risen as new strategy in the syntheses of dyes with luminescence properties. Scientists have turned from conventional heating to microwave assisted chemistry as an astounding and powerful strategy for their researches in modern organic synthesis. The technique offers a lot of advantages as it is simple, rapid, economic, and efficient. Dyes are effective molecules have pivotal effects in various fields. They were endowed with a diverse of electrochemical and photophysical properties and biomedical applications. Novel microwave synthetic strategies for many types of dyes including naphthalimides, phenothiazines, fluorescein, pyridinones, cyanines, quinolines, coumarins, triazoloquinoxalines, monoazo disperse dyes and schiff base dyes were demonstrated. This review highlights microwave applications for the synthesis of dyes with fluorescence, luminescence and photophysical properties from 1990 to 2017. Graphical abstract Microwave-assisted organic synthesis (MAOS) has fundamental roles in the synthesis of dyes with luminescent properties. These compounds have many industrial and biomedical applications which have drawn the interest of scientists. Various microwave synthetic approaches and strategies for various classes of fluorescent and luminescent dyes have been exhibited throughout this review. Image 1 Highlights • Green chemistry. • Applications of the luminescent dyes. • Up-to-date synthetic approaches for dyes with luminescence properties. [ABSTRACT FROM AUTHOR]

Abstract The following paper designed two rhodamine-based chemosensors for cysteine optical recognition. In order to decrease their photobleaching, up-conversion NaYF 4 nanocrystals were used as excitation host. There was an efficient energy transfer from these NaYF 4 nanocrystals to these rhodamine chemosensors, which was confirmed by spectral analysis, energy transfer radius calculation and emission decay lifetime comparison. Job's titration experiment suggested that these chemosensors followed a simple sensing mechanism towards Cys with binding stoichiometry of 1:1. Chemosensor emission was increased by Cys, showing emission turn on effect. Good selectivity and linear response were observed. It was found that sulfur modification on chemosensor improved sensitivity and selectivity. Graphical abstract Two rhodamine-based chemosensors for cysteine optical recognition were reported using up-conversion nanocrystals as excitation host, so that their photostability can be improved. Chemosensor emission was increased by Cys, showing emission turn on effect. Good selectivity and linear response were observed. fx1 [ABSTRACT FROM AUTHOR]

In this study, a smart and green analytical method based on the second-order calibration algorithm coupled with excitation-emission matrix (EEM) fluorescence was developed for the determination of rhodamine dyes illegally added into chilli samples. The proposed method not only has the advantage of high sensitivity over the traditional fluorescence method but also fully displays the “second-order advantage”. Pure signals of analytes were successfully extracted from severely interferential EEMs profiles via using alternating trilinear decomposition (ATLD) algorithm even in the presence of common fluorescence problems such as scattering, peak overlaps and unknown interferences. It is worth noting that the unknown interferents can denote different kinds of backgrounds, not only refer to a constant background. In addition, the method using interpolation method could avoid the information loss of analytes of interest. The use of “mathematical separation” instead of complicated “chemical or physical separation” strategy can be more effective and environmentally friendly. A series of statistical parameters including figures of merit and RSDs of intra- (≤1.9%) and inter-day (≤6.6%) were calculated to validate the accuracy of the proposed method. Furthermore, the authoritative method of HPLC-FLD was adopted to verify the qualitative and quantitative results of the proposed method. Compared with the two methods, it also showed that the ATLD-EEMs method has the advantages of accuracy, rapidness, simplicity and green, which is expected to be developed as an attractive alternative method for simultaneous and interference-free determination of rhodamine dyes illegally added into complex matrices. [ABSTRACT FROM AUTHOR]

The ultrafast dynamics of zwitterionic and cationic Rhodamine B in ethanol have been investigated using TDDFT calculations and ultrafast transient absorption spectroscopy. The calculations show that the zwitterionic form exhibits an electronically excited dark state which could potentially quench the initially photoexcited state, while in the case of cationic form the lowest excited lying dark state is outside the energy region of interest and cannot explain its quenching. Due to similarities in the relaxation dynamics of the two molecules, it is suggested that the electronically excited dark state may not play such an important role in the quenching process of this dye as previously proposed. Experimental evidence presented suggests that a quenching mechanism is active on the picosecond timescale for both forms of Rhodamine B. [ABSTRACT FROM AUTHOR]

Electrophoresis on plastic microchips is an economic way for rapid separation and determination of multiple analytes, but its application is frequently limited by the unstable electroosmotic flow (EOF) and non-specific adsorption of certain analytes and sample matrices. In this work, cationic polymer poly (diallyldimethylammonium chloride) (PDDA) was used as the background electrolyte (BGE) to eliminate the non-specific adsorption, control the EOF, regulate the viscosity and improve the separation efficiency on cyclic olefin copolymer microchips with 75 μm id microchannels. Three rhodamine dyes that are easily adsorbed on plastics were separated in the presence of organic solvents. Influences of the experimental conditions were systematically investigated and the performance was compared with anionic polymer polyacrylic acid or neutral polymer hydroxypropyl cellulose. The effectiveness of ionic polymers for the modulation of EOF was demonstrated. With PDDA as BGE, three rhodamine dyes were well separated and baseline separation could be achieved in 20 s with a voltage as low as 400 V using a microchannel of 1 cm long and 75 μm id. The determination of rhodamine dyes in foods and lipsticks was performed to verify the robustness and applicability of the proposed methods. Separation of peptides and proteins labeled by rhodamine B isothiocyanate was also performed with the proposed running medium. [ABSTRACT FROM AUTHOR]

Electronic absorption and fluorescence spectra of two Rhodamine dyes (Rhodamine B and Rhodamine 6G) in binary solutions are studied in this paper. The excited state dipole moments have been computed using the correlation coefficients obtained by linear solvation energy relationship (LSER) applied to electronic spectra and the values of the dipole moments in the ground state of Rhodamines computed by HyperChem 8.0.6. The nature and the contributions of each type of interactions to the spectral shifts from visible range are established based on solvatochromic analysis. [ABSTRACT FROM AUTHOR]

Rhodamine dyes are ideal material to construct off-on-type probes for recognizing various analytes with high sensitivity. However, most of them were operated in either pure organic or organic-aqueous solutions, which limited their practical applications in physiological environment. Herein, a universal strategy is provided to improve the water solubility of rhodamine-based fluorescent probe by structural modification. In this strategy, a carboxyl group is introduced to the chemical structure of probe. It is expected that the design strategy could be widely applied to improve the water solubility of all the existing rhodamine-based fluorescent probes. A fluorescent probe named Rh-COOH is designed and synthesized through attaching a carboxyl to the structure of this probe. Rh-COOH is used to recognize glutathione (GSH), which is the most abundant cellular thiol and plays crucial roles in physiological processes. The characteristics of this probe are as following: (1) Rh-COOH operates well in aqueous solution without organic solvent. (2) The probe exhibits high sensitivity toward GSH with 69-fold fluorescence enhancement. (3) The probe is highly selective, which will not be interfered by the other 2 biological thiols (Cys, Hcy) and other 19 amino acids. (4) The probe displays selective detection of GSH in living cells. [ABSTRACT FROM AUTHOR]

Rhodamine dyes are widely used as molecular probes in different fields of science. The aim of this paper was to ascertain to what extent the structural peculiarities of the compounds influence their absorption, emission, and acid-base properties under unified conditions. The acid-base dissociation (HR + ⇄ R + H + ) of a series of rhodamine dyes was studied in sodium n -dodecylsulfate micellar solutions. In this media, the form R exists as a zwitterion R ± . The indices of apparent ionization constants of fifteen rhodamine cations HR + with different substituents in the xanthene moiety vary within the range of p K a app = 5.04 to 5.53. The distinct dependence of emission of rhodamines bound to micelles on pH of bulk water opens the possibility of using them as fluorescent interfacial acid–base indicators. [ABSTRACT FROM AUTHOR]

The development of light-sensitive media based on organic, mostly heterocyclic compounds that have no fluorescence in their initial form but provide fluorescent photoproducts formation is considered in this review. Materials with photoinduced irreversible fluorescence appear to be the most promising in the design of recording media for 3D archive optical memory. Photoactivatable fluorophores are also of interest for use in cell biology. [ABSTRACT FROM AUTHOR]

A transition-metal-free method for the synthesis of N-substituted unsymmetrical sulforhodamine fluorophores from an unusual monobrominated sulfoxanthene dye and primary or secondary amines by direct SNAr-type reactions is presented. The simplicity and effectiveness of this 'postamination' procedure were demonstrated through the rapid preparation of a library of multifunctional red-emitting rhodamine analogues. Some of these analogues are equipped with a reactive handle and retain the two water-solubilizing sulfonic acid moieties of the starting halogenated derivative; this makes them ideal candidates for biolabeling applications. The potential utility of this expeditious strategy to finely tune the photophysical (Stokes shift) and physicochemical properties (amphiphilic character and water solubility) of the sulforhodamine scaffold was also demonstrated through the appendage of a fluorescent amine to create a fluorescence resonance energy transfer (FRET) pair, a long-chain amine, and tetraazamacrocycles derived from cyclen. [ABSTRACT FROM AUTHOR]

Photodehydrogenation of aryl(hetaryl)pyrazolines in the presence of organohalogen compounds has been used for fluorescence activation of Rhodamine laser dyes both in organic solvents and in polymer films. The ability of aryl(hetaryl)pyrazolines as photoacids to generate a highly fluorescent Rhodamine dye can be used for optical information recording. [ABSTRACT FROM AUTHOR]

Xanthene dyes such as rhodamine B undergo an interesting mass-spectrometric fragmentation reaction that eliminates small neutral alkanes such as propane. This fragmentation reaction has been investigated in a Fourier transform ion cyclotron mass spectrometer by means of laser photodissociation with visible light as well as by collision-induced dissociation. Different isotopically labeled decarboxyrhodamine B compounds were used to investigate the fragmentation mechanism. The results support a concerted mechanism for the formation of the alkanes instead of a two-step radical mechanism. [ABSTRACT FROM AUTHOR]

Abstract: Absorption and emission spectra of two rhodamine dyes with same molecular skeletons and different functional groups have been studied in various isotropic and anisotropic media. The solute photo-physical behavior depends strongly on the solvent–solute interactions and solvent microenvironment as well as resonance structures of the rhodamine dyes. In order to understand the effect of intermolecular interactions on spectral behaviors of these dyes and to conceive nature and extend of solvent–solute interactions the spectral variations were analyzed by the linear solvation energy relationships concept. In addition, by means of solvatochromic method the dyes dipole moments variations, from ground to excited states, were investigated in isotropic and anisotropic solvents media. [Copyright &y& Elsevier]

The concept of mitochondrial targeting for chemo- and photochemotherapy of neoplastic diseases has its origin in the observation that enhanced mitochondrial transmembrane potential is a common tumor cell phenotype. As a result of this enhanced transmembrane potential, a number of cationic dyes accumulate in larger amounts and are retained for longer periods in the mitochondria of tumor cells than in normal cells. Only a relatively small number of (photo)toxic dyes known to localize in energized cell mitochondria are capable of inducing the destruction of tumor cells with desirable degrees of selectivity, however. We investigated how lipophilic character may affect the degree of specificity with which cationic dyes localize in energized cell mitochondria and how mitochondrial specificity may affect tumor cell selectivity. To this end, we used fluorescence microscopy to characterize the subcellular localization of ethyl violet and seven analogs of the prototypical mitochondria-specific dye, rhodamine 123. All cationic rhodamines studied here (−0.62 < log Dow < 1.60, where Dow represents the n-octanol/water distribution coefficient) were found to show considerable mitochondrial specificity, while the more lipophilic ethyl violet ( log Dow == 2.37) did not. Ethyl violet was found to localize not only in mitochondria, but also in lysosomes. We also compared the degree of selective tumor cell killing induced by ethyl violet and two phototoxic rhodamines, i.e., the dibromo derivatives of rhodamine 123 and its n-octyl ester analog. While ethyl violet induces the destruction of human uterine sarcoma (MES-SA) cells and normal green monkey kidney cells (CV-1) with comparable efficiency, the mitochondria-specific dibromorhodamines were found to induce the destruction of MES-SA cells with considerable selectivity. Our findings are consistent with the premise that mitochondrial localization per se does not provide successful selective tumor cell killing using mitochondrial targeting. Our results reinforce the hypothesis that while most cationic dyes can be expected to localize at least to some extent in energized cell mitochondria, only those showing virtually absolute mitochondrial specificity can actually mediate the destruction of tumor cells with desirable selectivity. These findings also support the hypothesis that the probability of success of mitochondrial targeting in photochemotherapy of neoplastic diseases is bound to be higher when the Dow associated with the drug candidate falls within approximately two orders of magnitude of that of rhodamine 123. [ABSTRACT FROM AUTHOR]

Abstract: A fluorescent sensor for Fe3+ has been synthesized based on rhodamine-lactam, which shows excitation (531nm) and emission (557nm) wavelength, displays an excellent selectivity for Fe3+ and can be used for imaging Fe3+ in living cells. The pK a of the sensor is as low as of 3.2. It can be used in the range of pH 5–9. [Copyright &y& Elsevier]

Novel rhodamine dyes were prepared from xanthone precursors in a ‘one-pot’ procedure via reaction of the xanthone with trifluoromethanesulfonic anhydride followed by Pd-mediated Suzuki coupling between the xanthone triflate and an arylboroxin. Rhodamines with 9-(3- or 4-carboxyphenyl) and 9-(3-nitrophenyl) substituents were prepared by this procedure. The procedure also works well with thio- and selenoxanthones, but not with telluroxanthones. [ABSTRACT FROM AUTHOR]

Abstract: TiO2- and Ag/TiO2-nanotubes (NTs) were synthesized by hydrothermal methods and microwave-assisted preparation, respectively. Scanning electron microscopy, high resolution transmission electron microscopy, Brunauer–Emmett–Teller particle surface area measurement and X-ray diffraction were used to characterize the nanotubes. Rutile TiO2-NTs with Na2Ti5O11 crystallinity had a length range of 200–400nm and diameters of 10–20nm. TiO2- and Ag/TiO2-NTs with a 0.4% deposition of Ag had high surface areas of 270 and 169m2 g−1, respectively. The evaluation of photocatalytic activity showed that Ag/TiO2-NTs displayed higher photocatalytic activity than pure TiO2-NTs and a 60.91% degradation of Rhodamine-B with 0.8% deposition of Ag species. Also 60% of Rhodamine-6G was physisorbed and 40% chemisorbed on the surface of TiO2-NTs. In addition, the photocatalytic degradations of organochlorine pesticides taking α-hexachlorobenzene (BHC) and dicofol as typical examples, were compared using Ag/TiO2-NTs, and found that their degradations rates were all higher than those obtained from commercial TiO2. [Copyright &y& Elsevier]

Abstract: Two kinds of rhodamine modified β-cyclodextrins (R-1 and R-2), which are coupled up ethylene diamine (EDA) and tetraethylene pentamine (TEPA) between Rh B and β-cyclodextrin, respectively, have been synthesized. R-1 and 2 work as a new fluorogenic probe for monitoring pH of Hela cells, and MTT of assay R-1, R-2, and rhodamine B indicate that less a cytotoxicity of those R-1 and R-2 than that of rhodamine B, where R-1 has much less one than that of R-2. The fluorogenetic probe capability of R-2 was recognized in an area of acidic area in living cell, which is lysosome. [Copyright &y& Elsevier]

Abstract: The aggregative properties of rhodamine 6G (R6G) and rhodamine B (RB) in aqueous solutions of cationic and anionic surfactants were studied using the absorption and fluorescence spectroscopic methods. The dye–surfactant interactions in aqueous and surfactant solutions were also studied. The spectroscopic studies were extended in order to determine the effect of molecular structure of the surfactants on the aggregative behavior of the rhodamine dyes. The aggregate structures and the nature of the interacting pairs in these dyes were discussed using the exciton theory. [Copyright &y& Elsevier]

We have studied the effect of blood serum albumin on the absorption and fluorescence spectra of rhodamine C (RC), rhodamine 6G (R6G), and rhodamine 3B (R3B). Interaction of the dye with protein is assessed using the binding parameters: binding constants and concentrations of binding sites. We have studied the effect of temperature on the binding parameters. We have observed that heating a mixture of the dye solution with protein for 30 min leads to an increase in the binding constant for rhodamine 3B with protein by a factor of 2, while the concentration of binding sites increases by a factor of 2.3. This is explained by features of the globular protein structure and a change in its conformation when heated. We have shown that rhodamine 3B at a concentration of 10−5 M is the most effective among the studied rhodamine dyes for application as a fluorescent probe when studying conformational changes in blood serum protein. [ABSTRACT FROM AUTHOR]

Abstract: The absorption spectra of rhodamine B (RB) chloride, rhodamine 6G (R6G) tetrafluoroborate and rhodamine 6G chloride in poly-2-hydoxyethyl methacrylate hydrogel (PHEMA) matrix were studied using absorption spectroscopy in the visible region. The transport and aggregative properties of these ionic dyes in aqueous solution across the hydrophilic gel were also investigated. The similarities of absorption spectra of RB in aqueous solutions and in hydrogel host suggest that the hydrogel framework has a minor effect in their absorption spectra. In contrast, there is a relatively strong interaction or electrostatic forces between R6G dyes and the hydrogel matrix. The permeability of R6G chloride through hydrogel host is seen to be markedly higher than RB chloride and R6G tetrafluoroborate. [Copyright &y& Elsevier]

The aggregation of rhodamine 6G tetrafluoroborate and rhodamine 6G chloride in liquid crystalline solution (anisotropic host) was studied using polarized spectroscopy (the electronic absorption spectroscopy with polarized light). The self-association of these two ionic dyes in the normal solvents (isotropic hosts) was studied using absorption spectroscopy in the visible region for comparison. Therefore, the influence of the [BF4]-1 anion on the molecular interaction of the guest molecules was investigated. The dimerization constants, Kd=cd/cm, of solutions containing rhodamine 6G tetrafluoroborate and rhodamine 6G chloride in dioxane were calculated to be 183 l mol-1 and 2363 l mol-1, respectively, indicating important role of anion–cation interaction in their solvation. In contrast, the similarities of absorption spectra of these two dyes in aqueous solutions suggest that the type of anion has a minor effect on their absorption spectra. The nature of the interacting pairs in these dyes was discussed using the exciton theory. [Copyright &y& Elsevier]

The nanometer-sized ZnO was prepared through the sol–gel method. Its average particle diameter, determined by TEM, was 20–30 nm. The specific surface area was determined to be 22 m2 g-1 by BET. The photodegradation mechanism of Rhodamine dyes on nanometer-sized ZnO was studied by dynamic molecular spectra, and the results showed that the photodegradation of Rhodamine dyes obeyed the rules of a pseudo first-order kinetic reaction. The rate constant k of the degradation of Rhodamine B (RB) and butyl-Rhodamine (BR) were 0.0128 and 0.0154 min-1, respectively, and the half period t1/2 were 60 and 52 min, respectively. The photodegradation reaction conditions were optimized. After intermixing with silver, the photodegradation efficiency was greatly improved. A life-span test showed that nanometer-sized ZnO had a long life-span. [Copyright &y& Elsevier]

The spectral‐luminescence and generation properties of a nonsubstituted analog of rhodamine 101 have been investigated and compared to those of rhodamines 101 and 6G in a polyurethane matrix. It has been shown that the former possesses a higher photostability, a longer lifetime at the local point, and a higher efficiency of conversion of the dye‐laser energy than the latter. This has been attributed to the totally rigid structure of the analog of rhodamine 101 and the absence of photochemical‐reaction‐prone functional groups in it. [ABSTRACT FROM AUTHOR]

Microfluidic CE (MCE) is an effective solution for rapid and sensitive determination of multiple analytes. Herein, a dynamic coated cyclic olefin copolymer microchip was developed having an on-chip micropump for fluid velocity adjusting in electrophoretic separations. This micropump was fabricated by constructing a polyacrylamide gel membrane at one channel terminal. Once applying electric field across the membrane, a pressure-driven flow generated automatically to balance the electroosmotic flow (EOF) mismatch at the channel-membrane interface. The influence of gel precursor concentration and operating voltages on the fluid velocity was carefully evaluated. Moreover, the highly integration of injection, separation, and pumping units of the MCE system minimized the dead volume and provides satisfied column efficiency. Experiments showed that by adjusting of pumping voltage reduced the fluid velocity by a factor of 6, resulting six- and threefold resolving power enhancements of rhodamine dye mixture and amino acid mixture, respectively. Furthermore, the developed MCE method was applied for rhodamines and amino acids quantitation in food and cosmetics, with standard addition recoveries of 87.3-106.9% and 89.9-117.4%, respectively. These results were also confirmed by standard HPLC method, revealing the application potential in fast and onsite analysis of complex samples., (© 2022 Wiley-VCH GmbH.)

Rhodamine derivatives have been widely investigated for their mitochondrial targeting and chemotherapeutic properties that result from their lipophilic cationic structures. In previous research, we have found that conversion of Rhodamine 6G into nanoGUMBOS, i.e., nanomaterials derived from a group of uniform materials based on organic salts (GUMBOS), led to selective chemotherapeutic toxicity for cancer cells over normal cells. Herein, we investigate the chemotherapeutic activity of GUMBOS derived from four different rhodamine derivatives, two bearing an ester group, i.e., Rhodamine 123 (R123) and SNAFR-5, and two bearing a carboxylic acid group, i.e., rhodamine 110 (R110) and rhodamine B (RB). In this study, we evaluate (1) relative hydrophobicity via octanol–water partition coefficients, (2) cytotoxicity, and (3) cellular uptake in order to evaluate possible structure–activity relationships between these different compounds. Intriguingly, we found that while GUMBOS derived from R123 and SNAFR-5 formed nanoGUMBOS in aqueous medium, no distinct nanoparticles are observed for RB and R110 GUMBOS. Further investigation revealed that the relatively high water solubility of R110 and RB GUMBOS hinders nanoparticle formation. Subsequently, while R123 and SNAFR-5 displayed selective chemotherapeutic toxicity similar to that of previously investigated R6G nanoGUMBOS, the R110 and RB GUMBOS were lacking in this property. Additionally, the chemotherapeutic toxicities of R123 and SNAFR-5 nanoGUMBOS were also significantly greater than R110 and RB GUMBOS. Observed results were consistent with decreased cellular uptake of R110 and RB as compared to R123 and SNAFR-5 compounds. Moreover, these results are also consistent with previous observations that suggest that nanoparticle formation is critical to the observed selective chemotherapeutic properties as well as the chemotherapeutic efficacy of rhodamine nanoGUMBOS. [ABSTRACT FROM AUTHOR]

Rhodamines are widely used as laser dyes and fluorescent probes due to their excellent photophysical and photochemical properties. Previous theoretical studies have shown that the lowest excitation energies of rhodamines are overestimated systematically by time‐dependent density functional theory (TDDFT). In this study, we first perform a TDDFT benchmark study with 21 exchange‐correlation functionals (XCFs) on a series of rhodamines and assess the performance of different types of functional in predicting the lowest excitation energies of rhodamines. Statistical results reveal that the fraction of Hartree–Fock exchange (HFX) included in the XCF is a key parameter. Pure functionals without HFX offer the best performance, with the mean absolute error (MAE) of approximately 0.1 eV. However, they provide a wrong order of the lowest nπ* and ππ* states and suffer from charge‐transfer contamination problem for rhodamine dyes (RDs) in zwitterionic form. Among the other tested functionals, popular global hybrid functional B3LYP delivers the smallest MAE of 0.36 eV. We then perform calculations with second‐order algebraic diagrammatic construction and extended multiconfiguration quasi‐degenerate perturbation theory at second‐order of PT expansion methods. Remarkably accurate results are obtained. We confirm that the reason for the overestimation of the lowest excitation energies of RDs by TDDFT method should be similar to that of cyanine dyes, and that double excitations contribute to this systematic deviation. The lowest excitation energies of rhodamine dyes are systematically overestimated by time‐dependent density functional theory (TDDFT). Benchmark study reveals that this systematic deviation results from two factors: (1) the first excited‐state of rhodamine dyes contains substantial contributions from double excitations; (2) TDDFT has issues capturing the differential electron‐correlation effects between the ground and excited states of rhodamine dyes. [ABSTRACT FROM AUTHOR]

Although aqueous dye lasers are much sought after, they have been of no practical use, as laser dyes show a strong tendency for aggregation in water, thus diminishing their optical output. Contributing towards this shortcoming, we studied the noncovalent interactions of two prominent laser dyes, namely, rhodamine 6G and rhodamine B, with a water soluble macrocyclic host, sulfobutylether-β-cyclodextrin (SBE 7 βCD). Spectral changes in the absorption and fluorescence behavior of dyes in presence of the SBE 7 βCD host indicated adequate complex formation between dye and host (K∼10 4  M -1 ). A combination of various photophysical parameters evaluated from measurements such as Job plot, changes in the fluorescence lifetime/anisotropy values, and favorable thermodynamic parameters from isothermal titration calorimetric measurements adjudicated a 1 : 1 stoichiometric complex formation between dye and SBE 7 βCD host. Consequently, SBE 7 βCD prevents dye aggregation/adsorption and present rhodamine dyes in their monomeric forms with enhanced fluorescence yield and brightness. These vital parameters were utilized to optimize and demonstrate cost-effective supramolecular broad-band and narrow-band aqueous dye laser systems with improved lasing efficiencies (∼25 % higher for the SBE 7 βCD : RhB system and ∼10 % higher for SBE 7 βCD : Rh6G system), better beam profile, and enhanced durability compared to the respective dyes in optically matched ethanol solutions., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Luminescent metal-organic frameworks (MOFs) (typically dye-encapsulated MOFs) are considered as one kind of interesting downconversion materials for white-light-emitting diodes (LEDs), but their quantum efficiency (QE) is not sufficient and thus needs to be significantly enhanced for practical applications. In this study, we successfully synthesized a series of Rh@bio-MOF-1 (Rh = rhodamine) with an internal QE as high as ∼79% via a solvothermal reaction followed by cation exchanges. The high efficiency of the Rh@bio-MOF-1 composites was attributable to the high intrinsic luminescent efficiency of the selected Rh dyes, the confinement effect in the bio-MOF-1 host, and the uniform particle morphology. The emission maximum could be continuously tuned from 550 to 610 nm by controlling the species and concentration of encapsulated dye molecules, showing great color tunability of the dye-encapsulated MOFs. The emission lifetime of ∼7 ns was 1 or 2 magnitude orders shorter than that of Ce 3+ - or Eu 2+ -doped inorganic phosphors, allowing for visible light communication (VLC). White LEDs, fabricated by using the synthesized Rh@bio-MOF-1 composite and inorganic phosphors of green (Ba,Sr) 2 SiO 4 :Eu 2+ and red CaAlSiN 3 :Eu 2+ , exhibited a high color rendering index of 80-94, a luminous efficacy of 94-156 lm/W, and an excellent stability in color point against drive current. The Rh@bio-MOF-1 composites with tunable colors, short emission lifetime, and high QE are expected to be used for smart white LEDs with multifunctions of both lighting and VLC.

Rhodamine dyes have been banned as food additives due to their potential tumorigenicity. Rhodamine 110 is illegal as a food additive, although its pharmacokinetics have not been characterized, and no accurate bioanalytical methods are available to quantify rhodamine 110. The aim of this study was to develop and validate a fast, stable, and sensitive method to quantify rhodamine 110 using high-performance liquid chromatography coupled to tandem mass spectrometry (HPLC-MS/MS) to assess its pharmacokinetics and organ distribution in awake rats. Rhodamine 110 exhibited linear pharmacokinetics and slow elimination after oral administration. Furthermore, its oral bioavailability was approximately 34-35%. The distribution in the liver and kidney suggests that these organs are primarily responsible for rhodamine 110 metabolism and elimination. Our investigation describes the pharmacokinetics and a quantification method for rhodamine 110, improving our understanding of the food safety of rhodamine dyes.

A series of fluorescent nanothermometers (FTs) was prepared with Rhodamine dye-incorporated Pluronic F-127-melamine-formaldehyde composite polymer nanoparticles (R-F127-MF NPs). The highly soluble Rhodamine dye molecules were bound with Pluronic F127 micelles and subsequently incorporated in the cross-linked MF resin NPs during high-temperature cross-link treatment. The morphology and chemical structure of R-F127-MF NPs were characterized with dynamic light scattering, electron microscopy, and Fourier-transform infrared (FTIR) spectra. Fluorescence properties and thermoresponsivities were analyzed using fluorescence spectra. R-F127-MF NPs are found to be monodispersed, presenting a size range of 88-105 nm, and have bright fluorescence and high stability in severe treatments such as autoclave sterilization and lyophilization. By simultaneously incorporating Rhodamine B and Rhodamine 110 (as reference) dyes at a doping ratio of 1:400 in the NPs, ratiometric FTs with a high sensibility of 7.6%·°C(-1) and a wide temperature sensing range from -20 to 110 °C were obtained. The FTs exhibit good stability in solutions with varied pH, ionic strengths, and viscosities and have similar working curves in both intracellular and extracellular environments. Cellular temperature variations in Hela cells during microwave exposure were successfully monitored using the FTs, indicating their considerable potential applications in the biomedical field.