Rhodamine 6G Hydrazide Research Articles

Synthesis and Characterization of 2-(((2,7-Dihydroxynaphthalen-1-yl)methylene)amino)-3',6'-bis(ethylamino)-2',7'-dimethylspiro[isoindoline-1,9'-xanthen]-3-one and Colorimetric Detection of Uranium in Water.

2-(((2,7-Dihydroxynaphthalen-1-yl)methylene)amino)-3',6'-bis(ethylamino)-2',7'-dimethyl-spiro[isoindoline-1,9'-xanthen]-3-one was synthesized using Rhodamine 6G hydrazide (prepared using literature methods) and commercially available 2,7-dihydroxynaphthalene-1-carbaldehyde via imine condensation. Structural characterization was performed using FT-IR, 1H-NMR, 13C-NMR, X-ray, and HRMS. This Schiff base shows promise as a ligand for the colorimetric analysis of uranium in water.

Chiral MOF Derived Wearable Logic Sensor for Intuitive Discrimination of Physiologically Active Enantiomer.

Chiral sensors have attracted growing interest due to their application in health monitoring. However, rational design of wearable logic chiral sensors remains a great challenge. In this work, a dual responsive chiral sensor RT@CDMOF is prepared through in situ self-assembly of chiral γ-cyclodextrin metal-organic framework (CDMOF), rhodamine 6G hydrazide (RGH), and tetracyanovinylindane (TCN). The embedded RGH and TCN inherit the chirality of host CDMOF, producing dual changes both in fluorescence and reflectance. RT@CDMOF is explored as a dual channel sensor for chiral discrimination of lactate enantiomers. Comprehensive mechanistic studies reveal the chiral binding process, and carboxylate dissociation is confirmed by impedance and solid-state 1 H nuclear magnetic resonance (NMR). A flexible membrane sensor is successfully fabricated based on RT@CDMOF for wearable health monitoring. Practical evaluation confirms the potential of fabricated membrane sensor in point-of-care health monitoring by indexing the exercise intensity. Based on above, a chiral IMPLICATION logic unit can be successfully achieved, demonstrating the promising potential of RT@CDMOF in design and assembly of novel smart devices. This work may open a new avenue to the rational design of logic chiral sensors for wearable health monitoring applications.

A dual channel rhodamine appended smart probe for selective recognition of Cu2+ and Hg2+ via “turn on” optical readout

A new rhodamine-6G hydrazone RHMA has been synthesized using rhodamine-6G hydrazide and 5-Allyl-3-methoxysalicylaldehyde. RHMA has been fully characterized with different spectroscopic methods and single crystal XRD. RHMA can selectively recognize Cu2+ and Hg2+ in aqueous media amongst other common competitive metal ions. A significant change in absorbance was observed with Cu2+ and Hg2+ ions with emergence of a new peak at λmax 524 nm and 531 nm respectively. Hg2+ ions lead to “turn-on” fluorescence enhancement at λmax 555 nm. This event of absorbance and fluorescence marks the opening of spirolactum ring causing visual color change from colorless to magenta and light pink.RHMA-Cu2+ and RHMA- Hg2+complexes are found to be reversible in presence of EDTA2−ions. RHMA has real application in form of test strip. Additionally, the probe exhibits turn-on readout-based sequential logic gate-based monitoring of Cu2+ and Hg2+ at ppm levels, which may be able to address real-world challenges through simple synthesis, quick recovery, response in water, “by-eye” detection, reversible response, great selectivity, and a variety of output for accurate investigation.

Fluorescent and Colorimetric Dual-Mode Strategy Based on Rhodamine 6G Hydrazide for Qualitative and Quantitative Detection of Hg2+ in Seafoods.

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

A smartphone based-paper test strip chemosensor coupled with gold nanoparticles for the Pb2+ detection in highly contaminated meat samples

A rapid and selective colorimetric chemosensor based on a paper test-strip platform and smartphone detection were investigated to determine lead ions (Pb2+) in meat samples. The colorimetric chemosensor for Pb2+ analysis, the rhodamine 6G −1 (RD6G −1 probe), was synthesized through the Schiff base formation of rhodamine 6G hydrazide and 3,4,5-trimethoxybenzaldehyde. The Pb2+ sensing process was accomplished by the color on the detection zone change from colorless to pink within 1 min. The proposed chemosensor strip was functionalized with (3-aminopropyl)triethoxysilane and gold nanoparticles (AuNPs) to enhance the colorimetric response. Under the optimal conditions, the color intensity of the chemosensor strip increased linearly with the Pb2+ concentrations in the range of 0.1–1.0 mg/L. This developed strip allowed low detection limit (0.12 mg/L). The paper test strip modified with AuNPs provided a color response 9-fold higher than the one without AuNPs. Moreover, the paper test strip was successfully applied for Pb2+ analysis in meat samples, consistent with the inductively coupled plasma-mass spectrometry method.This work showed the proposed smartphone-based paper test-strip chemosensor offers a highly selective and accurate quantitative detection of Pb2+ ions without the additional equipment.

Facile Synthesis of Water-Soluble Rhodamine-Based Polymeric Chemosensors via Schiff Base Reaction for Fe3+ Detection and Living Cell Imaging.

Quantitative and accurate determination of iron ions play a vital role in maintaining environment and human health, but very few polymeric chemosensors were available for the detection of Fe3+ in aqueous solutions. Herein, a water-soluble rhodamine-poly (ethylene glycol) conjugate (DRF-PEG), as a dual responsive colorimetric and fluorescent polymeric sensor for Fe3+ detection with high biocompatibility, was first synthesized through Schiff base reaction between rhodamine 6G hydrazide and benzaldehyde-functionalized polyethylene glycol. As expected, the introduction of PEG segment in DRF-PEG significantly improved the water solubility of rhodamine derivatives and resulted in a good biosensing performance. The detection limit of DRF-PEG for Fe3+ in pure water is 1.00 μM as a fluorescent sensor and 3.16 μM as a colorimetric sensor at pH 6.5. The specific sensing mechanism of DRF-PEG toward Fe3+ is proposed based on the intramolecular charge transfer (ICT) mechanism, in which the O and N atoms in rhodamine moiety, together with the benzene groups from benzaldehyde-modified PEG segment, participate in coordination with Fe3+. Furthermore, DRF-PEG was applied for the ratiometric imaging of Fe3+ in HeLa cells and showed the potential for quantitative determination of Fe3+ in fetal bovine serum samples. This work provides insights for the design of water-soluble chemosensors, which can be implemented in iron-related biological sensing and clinical diagnosis.

Green Synthesis, Characterization and Photophysical Properties of Rhodamine Derivatives

Rhodamine 6G-chromone-derived compounds RD1 - RD4 have been synthesized by condensation of rhodamine 6G hydrazide and substituted chromone aldehydes in ethanol using microwave-assisted reaction. The structures of these synthesized rhodamine 6G derivatives were confirmed by proton nuclear magnetic resonance (1H-NMR), carbon nuclear magnetic resonance (13C-NMR), and high-resolution mass spectra data (HRMS). Colorimetric and photophysical studies show the synthesized compounds selectively detect copper (II) ion in aqueous acetonitrile solution.

A rhodamine based dye for sensing of Group 13 metal ions

Search for a new reagent for the detection of a particular group members is of significant importance to the researchers of analytical and inorganic chemistry. We report here a rhodamine based compound, L1, for the colorimetric as well as fluorometric sensing of Group 13 cations in 10 mM HEPES buffer in (1:9, v/v) water:ethanol (pH = 7.4). L1 has been obtained from the condensation between rhodamine 6G hydrazide and 4-(4-fluorobenzyloxy)benzaldehyde and characterized by standard methods. Colorless L1 becomes pink in the presence of Al3+, Ga3+, In3+ and Tl3+ ions. Its absorbance increases at ∼530 nm considerably with these cations. L1 is nonfluorescent. However, it exhibits strong fluorescence enhancement at about 555 nm in the presence of Al3+, Ga3+, In3+ and Tl3+.Other metal ions fail to alter any significant change in abosrbance and fluorescence. Opening of spirocyclic ring of L1 occurs with the Group 13 cations followed by the strong complex formation to display its color change and fluorescence increment. Lifetime and quantum yield of L1 increase appreciably with the cations. Limit of detection values of the probe are in order of 10−8 M indicating high sensitivity towards these cations. It has been utilized to sense these cations using river water. Thus, it may be concluded that L1 is effective to sense Group 13 metal ions.

Carbon nano-dot for cancer studies as dual nano-sensor for imaging intracellular temperature or pH variation

Cellular temperature and pH govern many cellular physiologies, especially of cancer cells. Besides, attaining higher cellular temperature plays key role in therapeutic efficacy of hyperthermia treatment of cancer. This requires bio-compatible, non-toxic and sensitive probe with dual sensing ability to detect temperature and pH variations. In this regard, fluorescence based nano-sensors for cancer studies play an important role. Therefore, a facile green synthesis of orange carbon nano-dots (CND) with high quantum yield of 90% was achieved and its application as dual nano-sensor for imaging intracellular temperature and pH was explored. CND was synthesized from readily available, bio-compatible citric acid and rhodamine 6G hydrazide using solvent-free and simple heating technique requiring purification by dialysis. Although the particle size of 19 nm (which is quite large for CND) was observed yet CND exhibits no surface defects leading to decrease in photoluminescence (PL). On the contrary, very high fluorescence was observed along with good photo-stability. Temperature and pH dependent fluorescence studies show linearity in fluorescence intensity which was replicated in breast cancer cells. In addition, molecular nature of PL of CND was established using pH dependent fluorescence study. Together, the current investigation showed synthesis of highly fluorescent orange CND, which acts as a sensitive bio-imaging probe: an optical nano-thermal or nano-pH sensor for cancer-related studies.

An "Off-On" Rhodamine 6G Hydrazide-Based Output Platform for Fluorescence and Visual Dual-Mode Detection of Lead(II).

In this study, the rhodamine 6G hydrazide (R6GH) complex was synthesized to develop an "off-on" output platform for fluorescence and visual dual-mode analysis of lead(II) (Pb2+). The prepared R6GH complex using the heat to reflux reaction of rhodamine 6G (R6G) and hydrazine hydrate was characterized through FT-IR, MS, 1H NMR, and 13C NMR and demonstrated to have good fluorescence stability and reversibility. The microenvironment for Pb2+ detection has been optimized in detail. Under the optimal conditions, the "off-on" R6GH-based fluorescence output platform showed a good response to Pb2+ in the concentration range of 0.05-6.0 μM (R2 = 0.9851) with a limit of detection (LOD) of 0.02 μM. Furthermore, at three spiked Pb2+ levels in the selected agricultural (tap water, soil) and food (fish, shrimp) samples, the developed R6GH-based fluorescence assays obtained a significant recovery range of 84.0-102.0% (RSD < 5.0%, n = 3), which had a good correlation with the results from ICP-MS (R2 = 0.9915). The developed R6GH immobilized paper-based array sensor can reach the lower LOD (2.5 μM) for Pb2+ through the naked eye. By combining with LAB analysis, a good linear response was obtained in the Pb2+ concentration range of 1.0-50.0 μM. These results indicated that the developed R6GH probe had great application potential in accurate detection of fluorescence and rapid visual and semiquantitative screening for Pb2+.

Theoretical solvent selection for nanostructured surface fabrication of reusable and colourimetric visual-eye sensor strips with rhodamine derivative-encapsulated polymeric membranes for highly sensitive and selective detection of Hg2+

Homogenous electrospinnable solutions were prepared through theoretical solvent selection using the high solubility parameters of rhodamine derivatives (rhodamine B hydrazide, RBH and rhodamine 6G hydrazide, R6GH) and poly(methylmethacrylate) (PMMA). Results of the systematic method showed that the best solvent for the Hg2+-sensing membranes was ethanol/tetrahydrofuran at 0.6/0.4 (v/v). PMMA/RBH and PMMA/R6GH membranes were fabricated using electrospinning. The optimal PMMA concentration was 11 wt%. The PMMA/RBH and PMMA/R6GH membranes possessed a nanostructured smooth surface with a high surface area of ultra-fine narrow nanofibres (about 2.5 μm in diameter). Given their high surface area with narrow-diameter fibres, the PMMA/RBH and PMMA/R6GH electrospun membranes showed high selectivity and sensitivity fluorescent sensing of Hg2+ ion with low detection limit (ranges of 0.8–1.099 and 3.6–4.3 ppb, respectively) than the sensor-encapsulated polymeric membranes prepared by spinning technique. The sensing membranes provided a vibrant colourimetric response unique to Hg2+ ions (white-pink) over other potential interfering metal cations that were observed within 30 s by the visual eye. Furthermore, the membranes were effective for reuse up to four times with a high fluorescence intensity. Therefore, PMMA/RBH and PMMA/R6GH can be used as portable colourimetric visual-eye and fluorescent sensors for the easy real-time monitoring of Hg2+ ions in dietary and environment sources.

A novel rhodamine-based turn-on probe for fluorescent detection of Au3+ and colorimetric detection of Cu2+

In this work, we design and synthesize the novel probe RC through introduction the 1-aza-4,13-dithia-15-crown-5 ring into the structure of rhodamine 6G hydrazide, where the N atom of crown ring is responsible for quenching of rhodamine fluorescence. The compound obtained behaves as multifunctional cation sensor providing selective fluorescent response to Au3+ and selective colorimetric response to Cu2+ ions in aqueous acetonitrile (1/1, v/v) at pH 7.0. The use of 10−5 M RC solution allowed reliable determination of target cations in the presence of a wide range of environmentally relevant ions with detection limits of 2 × 10−6 M and 5 × 10−7 M for gold and copper, respectively.

A rhodamine hydrazide–4-nitroindole-3-carboxaldehyde based turn on Hg2+ chemosensor: cytoplasmic live cell imaging, logic gate and memory device applications and computational studies

A new, highly sensitive probe L2 for the selective detection of Hg2+ in organo-aqueous (H2O:CH3CN, 1:1, v/v, HEPES buffer, pH 7.2) medium has been synthesized from rhodamine 6G-hydrazide and 4-nitroindole-3-carboxaldehyde. It was thoroughly characterized by physicochemical techniques including single crystal X-ray diffraction studies. The reaction of L2 with Hg2+ gives a 1:1 stoichiometry resulting in a 146 fold fluorescence enhancement and a binding constant (Kf) of 3 × 104 M−1. The spirolactam form of the probe is non-fluorescent; however, it shows dual channel (absorbance and fluorescence) recognition of Hg2+ via CHEF effect through the opening of the spirolactam ring. The quantum yields of L2 (0.00045) and L2-Hg2+ (0.29) show the higher stability of complex in the excited state over the free ligand. The 44.5 nM LOD value demonstrates the detection of Hg2+ at a very low concentration range. Cell imaging studies show the cytoplasmic recognition of Hg2+ by L2. Experimental results are comparable with theoretical values obtained by DFT studies. The fluorescence emission of the complex was completely quenched by I- and from the reversibility studies an advance level INHIBIT logic gate and memory device can be framed.

A highly selective chemiluminescent probe for the detection of chromium(VI)

In present work, rhodamine B hydrazide and rhodamine 6G hydrazide were synthesized and the chemiluminescence performance has been investigated. Based on the chemiluminescence of rhodamine 6G hydrazide‑chromium(VI), a selective and sensitive method for the direct detection of chromium(VI) was developed. The chemiluminescence intensity was linearly related to the concentration of chromium(VI) in the range of 2.60×10−8–8.00×10−6mol/L with a correlation coefficient of r=0.998 and a detection limit of 1.4×10−8mol/L (S/N=3). The results indicated rhodamine 6G hydrazide was an excellent chemiluminescent probe for chromium(VI) without reduction of chromium(VI) to chromium(III). A possible mechanism of CL emission was also suggested.

Light-Up of Rhodamine Hydrazide to Generate Emissive Initiator for Polymerization and to Afford Photochromic Polypeptide Metal Complex.

Ring-opening polymerization (ROP) of cyclic peptide monomer of γ-propargyl-l-glutamate N-carboxyanhydride (PLG–NCA) was originally initiated by non-emissive, ring-close rhodamine 6G hydrazide (R-C). However, instantaneously after adding PLG–NCA to R-C, the spirolactam ring of R-C was opened by PLG–NCA, rendering emissive, ring-open R-O to initiate ROP of PLG–NCA. The emissive R-O moiety therefore produced fluorescent R–PLG with aggregation-induced emission (AIE) properties. Moreover, R–PLG was found to exhibit photochromic properties with good fatigue resistance and long lifetime when forming metal complexes with Sn(II) and Fe(III). In the dark, irradiated metal complexes slowly (~50 min) restored to the initial state. This research provides foundation for the development of new photochromic materials with long lifetime.

An Efficient Fluorescence "Turn-On" Chemosensor Comprising of Coumarin and Rhodamine Moieties for Al3+ and Hg2.

A potent fluorescence 'turn-on' receptor (HL) based on rhodamine and coumarin moieties for the detection of Hg2+ and Al3+ is synthesized by condensation of rhodamine 6G hydrazide and 4-hydroxy-3-acetylcoumarin. In presence of Al3+ and/or Hg2+ the receptor (HL) exhibits deep pink colouration and a sharp band at 528nm is appeared in UV-vis titration. Upon gradual addition of Al3+ and/or Hg2+ to the solution of HL significant enhancement of fluorescence intensity is observed at 564nm in MeCN:H2O (1:5, v/v) medium. The receptor is strongly bound to Al3+ and/or Hg2+ and the association constants (Ka) are found to be 1.74 × 104 and 1.04 × 104 M- 1 for Al3+ and Hg2+ respectively. Graphical Abstract A potent fluorescence 'turn-on' receptor (HL) based on rhodamine and coumarin moieties for the detection of Hg2+ and Al3+ is synthesized and characterized. In presence of Al3+ and/or Hg2+ the receptor (HL) exhibits deep pink colouration and significant enhancement of fluorescence intensity is observed at 564nm in MeCN:H2O (1:5, v/v) medium. The receptor is strongly bound to Al3+ and/or Hg2+ and the association constants (Ka) are found to be 1.74 × 104 and 1.04 × 104 M- 1 for Al3+ and Hg2+ respectively.

A Rhodamine-Based Fluorescent Chemosensor for the Detection of Pb2+, Hg2+ and Cd2.

A new rhodamine-based fluorescent chemosensor (1) has been designed and synthesized by linking rhodamine 6G hydrazide with N-methylisatin via an imine linkage. The receptor can selectively recognize and sense Pb2+, Hg2+ and Cd2+ by showing different fluorescence characteristics. In ethanol/HEPES buffer medium, the addition of Cd2+ caused a yellowish-green fluorescence, while the presence of Pb2+ or Hg2+ gave rise to an orange fluorescence. Additionally, the sensor shows an irreversible fluorescence response to Pb2+ and reversible fluorescence responses to Hg2+ and Cd2+.

Optical sensing of hydrogen sulphate using rhodamine 6G hydrazide from aqueous medium

This communication reports the application of rhodamine 6G hydrazide (L) for the selective colorimetric and turn-on fluorescent sensing of hydrogen sulphate ions from aqueous medium. The ring opening of the colourless spirocyclic form of L was selectively triggered in the presence of HSO4− among the other tested anions (F−, Cl−, Br−, I−, AcO−, H2PO4−, NO3−, ClO4−, CN−, HO−, AsO33− and SO42−), which gives rise to a pink colour and strong fluorescence in the visible region. Sensor L showed a detection limit down to micromolar range without any interference from the other tested competitive anions. Sensor L was applied for the construction of two inputs (HO– and HSO4−) INHIBIT type molecular logic gate and naked-eye detection of HSO4− using test paper strips.

A highly sensitive and selective colorimetric and off–on fluorescent chemosensor for Cu2+ based on rhodamine 6G hydrazide bearing thiosemicarbazide moiety

Abstract A rhodamine derivative (R1) has been synthesized by an additive reaction of rhodamine 6G hydrazide with methyl 2-isothiocyanatobenzoate, which exhibits high selectivity and sensitivity as a fluorescent sensor toward Cu2+ under physiological conditions. The detection limit of Cu2+ ion is 47.2 nM. Moreover, R1 could sense Cu2+ by “naked eye” with a color change from colorless to pink. This selective signaling behavior is not affected by other canions that might be present in the environmental samples. The application of the fluorescent sensor in monitoring intracellular Cu2+ in HeLa cells was also demonstrated.

Rhodamine 6G hydrazone bearing thiophene unit: A highly sensitive and selective off–on fluorescent chemosensor for Al3+

A rhodamine derivative (R1) has been synthesized by a hydrazone formation of rhodamine 6G hydrazide with 3-methylthiophene-2-carbaldehyde, which exhibits high selectivity and sensitivity as an “off–on” fluorescent sensor toward Al3+ in water containing media. The binding process was confirmed by UV–vis absorption, fluorescence measurements, mass spectroscopy and DFT calculation. The probe functions by Al3+ induced hydrolytic cleavage of the imine-bond to produce an intense rhodamine-based emission. To test the practical use of the probe, the determination of Al3+ in real water samples was also evaluated.