Pyrene Fluorescence Research Articles

Mechanism of dust suppressant by sodium carboxymethyl cellulose grafted acrylic copolymer

In order to inhibit dust, a substance C-PAA was synthesized by free radical polymerization using sodium carboxymethyl cellulose and acrylic acid as raw materials and ammonium persulfate as an initiator. The optimal synthesis process was determined by using a single factor experimental method. Quantum chemistry and experiments were used to investigate the chemical synthesis of C-PAA. The results indicate that the active centers of the reaction were at the OH bond of sodium carboxymethyl cellulose, where H was seized by ·SO4-, produced by ammonium persulfate, to form an alkoxyl radical. Concurrently, ·SO4- attacked acrylic acid, resulting in the breakage of the CC bond, creating a CC bond, and combining with the alkoxyl group to create a new ether group that produced the compound C-PAA. The enthalpy change and activation energy of the reaction were −178.40 KJ/mol and −22.59 KJ/mol, respectively, and the infrared absorption peaks of the newly generated fatty ether and the increase in the relative content of the ether group in the final product proved that the preparation of C-PAA was successful. In order to further improve the wetting performance of the dust suppressant, pyrene fluorescence spectrometry was used to determine the critical micelle concentration of the surfactant sodium dodecyl sulfate as 1.5 g/L, and 1.5 g/L sodium dodecyl sulfate was mixed with C-PAA to obtain the dust suppressant SC-PAA. In comparison to the H2O-lignite system, the total number of hydrogen bonds in the SC-PAA-lignite system increased from 2023 to 2405, according to the molecular dynamics results. The rationale is that C-PAA in SC-PAA has a plethora of oxygen-containing functional groups, which enable it to create more hydrogen bonds with H2O as well as amino and hydroxyl groups on the surface of lignite. Due to hydrogen bonding, the dust suppressant is able to gather more water molecules adsorbed on the surface of the lignite. It then utilizes the capillary force of the coal pores to penetrate deeply into the fissures within the coal particles, thereby enhancing the wetting impact on the lignite.

Aggregation Characteristics of Biobased Anionic Surfactant, Hydroxy Alkane Sulfonate in Aqueous CaCl2 Solutions: Vesicle and Supported Bilayer Formation.

Vesicles are known to spontaneously adsorb onto solid-liquid interfaces and to form supported bilayers in aqueous solution. Cationic surfactants have typically been used to generate supported bilayers because solid surfaces in water are often negatively charged. The present study investigated the aggregation behavior of an anionic surfactant, hydroxy alkane sulfonate having a C18 alkyl chain (C18HAS) in aqueous CaCl2 solutions. These assessments were performed by acquiring data related to equilibrium surface tension, the solubilization of an oil-soluble dye, UV-visible transmittance, pyrene fluorescence and dynamic light scattering together with freeze-fracture transmission electron microscopy observations. The results suggest that C18HAS can form vesicles in aqueous CaCl2 solutions under certain surfactant concentrations. Specifically, this aggregation behavior is greatly affected by C18HAS/CaCl2 molar ratio. At the C18HAS/CaCl2 molar ratio is less than an equivalence point (that is, less than 2:1), phase separation occurs with the formation of a vesicle above solubility limit of the C18HAS Ca salt. On the other hand, in the case that the C18HAS/CaCl2 molar ratio is above an equivalence point (that is, above 2:1), the Na salt of C18HAS forms micelles above the critical micelle concentration (cmc), causing solubilization of vesicles. Analyses by high-speed atomic force microscopy demonstrated that the C18HAS vesicles can spontaneously form a supported bilayer on a negatively charged mica surfaces, similar to the behavior of cationic surfactant vesicles, even though C18HAS is an anionic surfactant. These results suggest that C18HAS could serve as a detergent component but also as a surface modifier when the C18HAS/CaCl2 molar ratio is optimized.

Study on synthesis and mechanism of high temperature resistant suspension stabilizer for spacer fluid

With 2-acrylamido-2-methylpropanesulfonic acid (AMPS), YX-1 (a monomer containing an amide group) as the main chain, DX-2 (a monomer containing a hydrophobic group), N-vinylpyrrolidone (NVP) as the side chain, the high temperature resistant suspension stabilizer for spacer was prepared by free radical aqueous solution polymerization and characterized. The structure was characterized by fourier transform infrared (FTIR) spectroscopy and thermogravimetry-differential thermal analysis (TG-DTA), which proved that the synthesized product was the target product. The performance of the copolymer was evaluated. The experimental results showed that it could be used in the spacer fluid at 30 ∼ 210 °C, and its sedimentation performance could also meet the requirements in the spacer fluid system containing saturated brine. In order to explore the mechanism of the polymer, the polymer solution was tested by six-speed rotational viscometer, pyrene fluorescence probe test, environmental scanning electron microscopy (ESEM) test, and the isolation solution containing the copolymer was tested by Zeta potential test and X-ray diffraction (XRD). Based on the above test results, it is shown that the suspension stabilizer synthesized in this paper has the characteristics of thickening, physical plugging, chemical and physical adsorption, which can effectively ensure that the spacer fluid has excellent suspension performance at high temperature.

Dual Fluorescence and Phosphorescence Emissions from Dye-Modified (NCN)-Bismuth Pincer Thiolate Complexes.

We report the synthesis, characterization, and photophysical properties of four new dye-modified (NCN)Bi pincer complexes with two mercaptocoumarin or mercaptopyrene ligands. Their photophysical properties were probed by UV/vis spectroscopy, photoluminescence (PL) studies, and time-dependent density functional theory (TD-DFT) calculations. Absorption spectra of the complexes are dominated by mixed pyrene or coumarin π → π*/n(pS) → pyrene or coumarin π* transitions. While unstable toward reductive elimination of the corresponding disulfide under irradiation at room temperature, the complexes provide stable emissions at 77 K. Under these conditions, coumarin complexes 2 and 4 exhibit exclusively green phosphorescence at 508 nm. In contrast, the emissive properties of pyrene complexes 1 and 3 depend on the excitation wavelength and on sample concentration. Irradiation into the lowest-energy absorption band exclusively triggers red phosphorescence from the pyrenyl residues at 640 nm. At concentrations c < 1 μM, excitation into higher excited electronic states results in blue pyrene fluorescence. With increasing c (1-100 μM), the emission profile changes to dual fluorescence and phosphorescence emission, with a steady increase of the phosphorescence intensity, until at c ≥ 1 mM only red phosphorescence ensues. Progressive red-shifts and broadening of steady-state excitation spectra with increasing sample concentration suggest the presence of static excimers, as we observe it for concentrated solutions of pyrene. Crystalline and powdered samples of 1 indeed show intermolecular association through π-stacking. TD-DFT calculations on model dimers and a tetramer of 1 support the idea of aggregation-induced intersystem crossing (AI-ISC) as the underlying reason for this behavior.

Polyelectrolyte complexes of chitosan and hyaluronic acid or carboxymethylpullulan and their aminoguaiacol derivatives with biological activities as potential drug delivery systems

Polyelectrolyte complexes (PECs) were elaborated from chitosan as cationic polymer and carboxy-methylpullulan (CMP), hyaluronic acid (HA) and their derivatives grafted with aminoguaiacol (G) with different degrees of substitution (DSGA) with the aim of obtaining nanogels for drug delivery. For each couple of polysaccharides, the charge ratios giving the smaller size with the lower PDI were selected to produce PECs. CMP_CHIT and CMP-G_CHIT PECs had smaller sizes (220–280 nm) than HA_CHIT and HA-G_CHIT PECs (280–390 nm). PECs were stable at 4 °C during 28 days at pH 5. In phosphate buffer saline (PBS) at pH 7.4, at 4 °C, a better stability of PECs based on CMP-G derivatives was observed. The hydrophobic associations between aminoguaiacol groups (highlighted by measurements of pyrene fluorescence) led to a better PECs' stabilization in PBS. The PECs' antioxidant and antibacterial activities were demonstrated and related to the DSGA. Diclofenac and curcumin were used as drug models: their loading reached 260 and 53 μg/mg PEC, respectively. The release of diclofenac in PBS at 37 °C followed a quasi-Fickian diffusion mechanism with release constant between 0.88 and 1.04 h−1. The curcumin release followed a slow linear increase in PBS/EtOH (60/40 V/V) with an effect of DSGA.

Interfacial and aggregation behavior of ionic liquid-bile salt conjugates

Bile salt derived nontoxic surface-active ionic liquids (SAILs), 1-butyl-3-methylimidazolium cholate ([bmim]C) and deoxycholate ([bmim]DC) were synthesized by reacting [bmim] tetrafluoroborate separately with sodium cholate (NaC) and sodium deoxycholate (NaDC) which were subsequently characterized by FTIR, 1H-NMR, 13C-NMR, HRMS, PXRD, and TGA-DTA studies. Interfacial and aggregation behavior of the SAILs were assessed by surface tension, conductance, pyrene fluorescence, dynamic light scattering, and isothermal titration calorimetric studies. Critical micelle concentration values were substantially lower than their precursor sodium salts. SAILs were less surface active than their corresponding sodium salts due to enhanced aqueous solubility induced by the ionic liquid cation. Both the aggregation number and size of the SAIL micelles were higher/larger where the SAIL micelles were more compact than NaC/NaDC. Exothermic changes in the enthalpy of micellization were higher for SAILs, where the micellization processes were found to be entropy driven. Such comprehensive studies can shed further light on the microstructure, besides the fundamental understanding on SAIL aggregation. The combined advantages of surfactant and ionic liquid in the SAILs can result in superior amphiphilic characteristics. Such nontoxic aggregates are capable to enhance the limited solubility of organic compounds in water besides their possible uses in catalysis, drug delivery, and energy storage, etc.

Location of a Hydrophobic Load in Poly(oligo(ethylene glycol) methyl ether methacrylate)s (PEGMAs) Dissolved in Water and Probed by Fluorescence.

Two series of pyrene-labeled poly(oligo(ethylene glycol) methyl ether methacrylate)s referred to as PyEG5-PEGnMA and PyC4-PEGnMA were prepared to probe the region surrounding the polymethacrylate backbone by using the fluorescence of the dye pyrene. PyEG5-PEGnMA and PyC4-PEGnMA were prepared by copolymerizing the EGnMA methacrylate monomers with penta(ethylene glycol) 1-pyrenemethyl ether methacrylate or 1-pyrenebutyl methacrylate, respectively. In organic solvents, the much longer 18 non-hydrogen atom linker connecting the pyrene moieties to the polymethacrylate backbone in the PyEG5-PEGnMA samples enabled the deployment of the pyrenyl labels into the solution. In water, however, an excited pyrene for PyEG5-PEGnMA was found to probe a same volume as for the PyC4-PEGnMA samples where a much shorter 6 non-hydrogen atom spacer connected pyrene to the backbone. Another surprising observation, considering that the hydrophobicity of pyrene induces strong pyrene aggregation for many pyrene-labeled water-soluble polymers (Py-WSPs) in water, was the little pyrene aggregation found for the PyEG5-PEGnMA and PyC4-PEGnMA samples in water. These effects could be related to the organic-like domain (OLD) generated by the oligo(ethylene glycol) side chains densely arranged around the polymethacrylate backbone of the polymeric bottlebrush (PBB). Additional fluorescence experiments conducted with the penta(ethylene glycol) 1-pyrenemethyl ether derivative indicated that the cylindrical OLD surrounding the polymethacrylate backbone had a chemical composition similar to that of ethylene glycol. Binding of hydrophobic pyrene molecules to unlabeled PEGnMA bottlebrushes in water further supported the existence of the OLD. The demonstration, that PEGnMA samples form an OLD in water, which can host and protect hydrophobic cargoes like pyrene, should lead to the development of improved PEGnMA-based drug delivery systems.

Nucleobase-Functionalized 7-Deazaisoguanine and 7-Deazapurin-2,6-diamine Nucleosides: Halogenation, Cross-Coupling, and Cycloaddition.

The functionalization in position-7 of 7-deazaisoguanine and 7-deazapurin-2,6-diamine ribo- and 2'-deoxyribonucleosides by halogen atoms (chloro, bromo, iodo), and clickable alkynyl and vinyl side chains for copper-catalyzed and copper-free cycloadditions is described. Problems arising during the synthesis of the 7-iodinated isoguanine ribo- and 2'-deoxyribonucleosides were solved by the action of acetone. The impact of side chains and halogen atoms on the pKa values and hydrophobicity of nucleosides was investigated. Halogenated substituents increase the lipophilic character of nucleosides in the order Cl < Br < I and decrease the pK values of protonation. Photophysical properties (fluorescence, solvatochromism, and quantum yields) of azide-alkyne click adducts bearing pyrene as sensor groups were determined. Pyrene fluorescence was solvent-dependent and changed according to the linker lengths. Excimer emission was observed in dioxane for the long linker adduct. Bioorthogonal inverse-electron-demanding Diels-Alder cycloadditions (iEDDA) were conducted on the electron-rich vinyl groups of 7-deazaisoguanine and 7-deazapurin-2,6-diamine nucleosides as dienophiles and 3,6-dipyridyl-1,2,4,5-tetrazine as diene. The initially formed complex reaction mixture of isomers could be easily oxidized with iodine in tetrahydrofuran (THF)/pyridine leading to single aromatic tetrazine adducts within a short time and in excellent yields.

Effect of Solute on Interfacial Properties and Micelle Structure of Dodecylbenzenesulfonate (DBS): Experimental and Molecular Dynamics Studies.

A combined experimental and molecular dynamic simulation approach was used to examine the structure and interfacial properties of solute-saturated micelles. The properties of dodecylbenzenesulfonate (DBS) micelles were examined in dodecane and benzene hydrocarbon systems. Pyrene fluorescence was used to determine the aggregation number of surfactant monomers in the micelle systems. Molecular dynamic (MD) simulations using energy minimization applying the CHARMm force field with the TIP3P model for water. Comparison of the DBS/benzene and DBS/Dodecane micelles equilibrium structures via radial distribution function (RDF) and probability distribution function (PDF) analysis indicates that the area per head group for the DBS/Benzene micelle interface is significantly larger than that of the DBS/Dodecane at the interface. It was also determined that benzene molecules can move freely within the micelle while dodecane is strictly confined in the core of the micelle. The increased interfacial area per monomer caused by the insertion of benzene also reduces the effectiveness of the surfactant, which has implications for use in various environmental applications. However, the DBS/benzene micelle can solubilize many more hydrocarbon molecules in one micelle with less surfactant monomer (i.e., lower aggregation number) per micelle due to the increased available packing positions within the micelle. This, in turn, increases the efficiency of the surfactant in real-world applications which is consistent with previous laboratory results. Understanding the differing solubilization characteristics of surfactants against various classes of hydrocarbons in single solute systems is a necessary step to beginning to understand their solubilization properties in the mixed waste systems prevalent in most surfactant enhanced remediation (SEAR) strategies.

Development of temperature- and salt-resistant viscosifier with dual skeleton structure of microcrosslinking and hydrophobic association structures and its application in water-based drilling fluids

In the process of developing deep oil and gas resources, the problem of high temperature and high salinity in deep strata has become a serious challenge faced by water-based drilling fluids. Under high temperature and high salinity conditions, drilling fluids must maintain good rheological properties to ensure safe and efficient drilling work. In this study, a temperature- and salt-resistant viscosifier (DASL) was synthesized using N, N-dimethylacrylamide, 2-Acrylamido-2-methylpropane sulfonic acid, sodium p-styrene sulfonate, and lauryl methacrylate as monomers with a double backbone structure of micro crosslinking and hydrophobic association structures. The results of pyrene fluorescence probe test and transmission electron microscopy observation showed that DASL has an obvious hydrophobic associative structure. Moreover, due to the presence of microcrosslinked structure, DASL exhibits good shear thinning property and thixotropy in aqueous solution. Under the conditions of 200 ℃ and 35 wt% NaCl, the apparent viscosity of the drilling fluid with 2 wt% DASL added was 24.5 mPa⸱s, and the filtration was only 9.2 mL. In addition, mechanism studies have shown that the dual skeleton structure of DASL improves its temperature and salt resistance. DASL can adsorb and bridge with bentonite particles, increase the internal friction and structural viscosity of the drilling fluid, enhance the internal mesh structure of the drilling fluid, improve the colloidal stability of the drilling fluid, and maintain a reasonable particle size distribution of the bentonite particles, which enable DASL to significantly increase the viscosity of the drilling fluid while reducing the filtration loss of the drilling fluid. This work demonstrates that polymers with dual skeleton structures of micro crosslinking and hydrophobic association have good application effects as temperature- and salt-resistant viscosifier for water-based drilling fluids.

Switched "On" Transient Fluorescence Output from a Pulsed-Fuel Molecular Ratchet.

We report the synthesis and operation of a molecular energy ratchet that transports a crown ether from solution onto a thread, along the axle, over a fluorophore, and off the other end of the thread back into bulk solution, all in response to a single pulse of a chemical fuel (CCl3CO2H). The fluorophore is a pyrene residue whose fluorescence is normally prevented by photoinduced electron transfer (PET) to a nearby N-methyltriazolium group. However, crown ether binding to the N-methyltriazolium site inhibits the PET, switching on pyrene fluorescence under UV irradiation. Each pulse of fuel results in a single ratchet cycle of transient fluorescence (encompassing threading, transport to the N-methyltriazolium site, and then dethreading), with the onset of the fluorescent time period determined by the amount of fuel in each pulse and the end-point determined by the concentration of the reagents for the disulfide exchange reaction. The system provides a potential alternative signaling approach for artificial molecular machines that read symbols from sequence-encoded molecular tapes.

Ultrafast photoactivated nitric oxide release with a pyrene fluorescence probe

Nitric oxide (NO) plays important roles in both physiology and therapeutics. Nonetheless, the in-situ monitoring of NO release from most existing donors is challenging, inhibiting advanced research in both chemistry and biology. In this study, we introduce an innovative photochemotherapeutic agent that incorporates a nitroaniline NO moiety with an integrated pyrene fluorophore. This design enables controlled NO release upon light irradiation, allowing for precise quantification through a dramatic fluorescence enhancement (with a 3000-fold increase in intensity). Ultrafast spectroscopy data revealed that the NO release process is exceptionally rapid, completing within 13.3 ps. Additionally, the donor's fluorescence was successfully utilized for in situ cell imaging upon direct photoexcitation. Consequently, using this fluorescent probe enables the accurate visualization of NO release kinetics, dosage, and localization in real-time. The unique advantages of this NO donor are anticipated to significantly advance research in NO chemistry and biology.

A Spectroscopic and Molecular Dynamics Study on the Aggregation Properties of a Lipopeptide Analogue of Liraglutide, a Therapeutic Peptide against Diabetes Type 2.

The pharmacokinetics of peptide drugs are strongly affected by their aggregation properties and the morphology of the nanostructures they form in their native state as well as in their therapeutic formulation. In this contribution, we analyze the aggregation properties of a Liraglutide analogue (LG18), a leading drug against diabetes type 2. LG18 is a lipopeptide characterized by the functionalization of a lysine residue (K26) with an 18C lipid chain. To this end, spectroscopic experiments, dynamic light scattering measurements, and molecular dynamics simulations were carried out, following the evolution of the aggregation process from the small LG18 clusters formed at sub-micromolar concentrations to the mesoscopic aggregates formed by aged micromolar solutions. The critical aggregation concentration of LG18 in water (pH = 8) was found to amount to 4.3 μM, as assessed by the pyrene fluorescence assay. MD simulations showed that the LG18 nanostructures are formed by tetramer building blocks that, at longer times, self-assemble to form micrometric supramolecular architectures.

Influence of acetyl-11-keto-beta boswellic acid on hepatic membrane dynamics and lipidiome during conditions of benzo(a)pyrene induced toxicity

Background and AimPollution and lifestyle changes expose mankind to a number of toxicants such as polycyclic aromatic hydrocarbons that may cause life-threatening diseases. The present study was undertaken to explicate the protective role of Acetyl-11-Keto-Beta Boswellic Acid (AKBA), if any, in containing benzo(a)pyrene (BaP) induced alterations on hepatic membrane dynamics and lipidiome in female rats. Experimental procedureThe animals were divided into five groups viz. Normal control, Vehicle treated, BaP treated, AKBA treated and BaP + AKBA treated. To induce hepatotoxicity, BaP was administered orally at a dose level of 50 mg/kg b.wt. dissolved in olive oil twice a week for 4 weeks. AKBA was supplemented to animals four weeks prior to BaP treatment and continued for 8 weeks at a dose level of 50 mg/kg b.wt. thrice a week. Certain key indices that included oxidative stress biomarkers, lipid profile of membranes, membrane fluidity parameters and activities of ATPases were studied. Results and ConclusionThe results showed that benzo(a)pyrene treatment resulted in a significant increase in the levels of lipid peroxidation (LPO) and ROS but caused a significant decrease in the levels of total lipids, phospholipids, cholesterol, glycolipids and activities of ATPases. Hepatic membrane fluidity as assessed by 1,6-Diphenyl-1,3,5-hexatriene (DPH) and Pyrene fluorescence probes was significantly increased in rats intoxicated with BaP. Interestingly, AKBA supplementation to BaP treated rats appreciably contained altered membrane dynamics and lipidiome as well as modulated hepatotoxicity by skirmishing activities of oxidative stress markers and also improved hepatic histoarchitecture. Our study thus concludes that AKBA can be used as a prophylactic intervention in providing protection to hepatocytes as it maintains membrane integrity in conditions of BaP induced toxicity.

Complexes of alkylated 1,4-diazabicyclo[2.2.2]octane with Ag(I) and Gd(III). Synthesis, self-association and biological activity

New amphiphilic surfactant-transition metal complexes [Ag(L)(NO3)2], [Ag(2L)(NO3)3] and [Gd(L)Br(NO3)3H2O] (where L is 1-cetyl-4-aza-1-azoniabicyclo[2.2.2]octane) were synthesized and characterized. The composition and 3D structure of the complexes were determined using IR and 1H NMR spectroscopy, elemental analysis, and X-ray diffractometry. Self-assembly and adsorption properties of the amphiphiles in an aqueous medium were studied by tensiometry, conductometry, potentiometry, dynamic and electrophoretic light scattering, transmission electron microscopy and fluorescence of pyrene. The Kraft temperature, the critical micelle concentration, the degree of bromide ion binding with aggregates, the aggregation numbers, the aggregate size, the zeta-potential of the systems, and the adsorption characteristics at the water–air interface were determined. The results obtained were compared with data for single ligand solutions and ligand-inorganic salt mixtures. A high aggregation capacity and morphological rearrangements in metallosurfactant solutions (vesicle-micelle transition) were established. The antimicrobial activity of metallosurfactants (including antibiotic-resistant strains), as well as low hemolytic and cytotoxic effects were shown, which allows them to be classified as potential drugs with a wide spectrum of activity.

Self-assembly of NrTP6 cell-penetrating lipo-peptide with variable number of lipid chains: Impact of phosphate ions on lipid association

HypothesisLipopeptides synthesized from the Nucleolar Targeting Peptide (NrTP6) with one, two or four dodecanoic fatty acid (FA) chains, display large head to tail volumes, which together with the number of lipid chains per molecule, impacts their self-assembly behavior. In phosphate buffer (PB), peptide to peptide interactions are triggered by the presence of phosphate ions that act as ionic crosslinkers, affecting the organization of the lipid assemblies. ExperimentalThe NrTP6 lipopeptides were synthesized by the solid phase peptide synthesis technique. The critical micellar concentration (CMC) of the lipopeptides was determined in water and PB by pyrene fluorescence. The size and morphology of lipopeptide assemblies were characterized by dynamic light scattering (DLS) and transmission electron microscopy (TEM). Circular dichroism (CD) was used to study the secondary structures of the lipopeptide assemblies. ResultsFor NrTP6 lipopeptides with two and four lipid chains, CMCs in water are larger than in PB. TEM images of the lipopeptide assemblies show different morphologies including fibers, rods, and spheres depending on the number of lipid chains, concentration and whether they are assembled in water or PB. CD spectroscopy shows that the peptide conformation, either random or beta, correlates with the morphology of the assemblies.

A Smart Single-Fluorophore Polymer: Self-Assembly Shapechromic Multicolor Fluorescence and Erasable Ink.

A novel smart fluorescent polymer polyethyleneimine-grafted pyrene (PGP) is developed by incorporating four stimuli-triggers at molecular level. The triggers are amphiphilicity, supramolecular host-guest sites, pyrene fluorescence indicator, and reversible chelation sites. PGP exhibits smart deformation and shape-dependent fluorescence in response to external stimuli. It can deform into three typical shapes with a characteristic fluorescence color, namely, spherical core-shell micelles of cyan-green fluorescence, standard rectangular nanosheets of yellow fluorescence, and irregular branches of deep-blue fluorescence. A quasi-reversible deformation between the first two shapes can be dynamically manipulated. Moreover, driven by reversible coordination and the resulting intramolecular photoinduced electron transfer, PGP can be used as an aqueous fluorescence ink with erasable and recoverable properties. The fluorescent patterns printed by PGP ink on paper can be rapidly erased and recovered by simple spraying a sequence of Cu2+ and ethylene diamine tetraacetic acid aqueous solutions. This erase/recover transformation can be repeated multiple times on the same paper. The multiple stimulus responsiveness of PGP makes it have potential applications in nanorobots, sensing, information encryption, and anticounterfeiting.

Insight into the aggregation and phase behavior for aqueous solution of ethylene glycol monobutyl ether with self-assembly induced optical and electrical properties

Ethylene glycol monobutyl ether (EGMBE) is a polar small molecule with amphiphilic characteristics, which can form various aggregates in aqueous solution. The solubility of EGMBE decreases as the temperature increasing with a lower critical solution temperature (LCST). The influence of temperature and salinity on aggregation behavior and solubility of EGMBE were thoroughly investigated in this paper. The phase transition temperatures of EGMBE aqueous solutions with different concentrations were determined and compared with literature. The completed phase diagram of the ternary system (water + NaCl + EGMBE) was constructed. The measured liquid-liquid equilibrium (LLE) data can be well fitted to the commonly used empirical equations Othmer–Tobias, Bancroft and Setschenow. The dynamic light scattering (DLS) measurement shows that the particle size of EGMBE aggregates increases with increasing concentration, reaching its maximum at EGMBE mass fraction of about 30 %. Increasing temperature and inorganic salt concentration can both promote the increase of particle size, especially when approaching the phase separation point, the particle size increases sharply, and the corresponding viscosity of EGMBE solution abnormally increases with increasing temperature. The Tyndall effect of EGMBE solution was also observed to be most significant at mass fraction around 30 %. It is interesting to note that the conductivity of EGMBE solution increases with increasing concentration, reaching its maximum value when the EGMBE mass fraction is about 30 %, though EGMBE is not conductive. The investigation of pyrene fluorescence probes and surface/interfacial tension also demonstrated the aggregation and surface adsorption of EGMBE.

A Sensitive Concentration- and Polarity-Dependent Pyrene-Derived Vibrationally Resolved Fluorescence Probe for The Polymer Interdiffusion Study.

The vibrationally resolved pyrene fluorescence probe method was once popular but now languished, because the vibrationally resolved patterns of pyrene with limited sensitivity and concentration independence have not been updated for over 50 years. During our investigation on the polymer interdiffusion of a latex film, we found a pyrene acylhydrazone whose vibrationally resolved fluorescence pattern contradictory to those reported in pyrene and most pyrene derivatives. The pyrene acylhydrazone has sensitive concentration- and polarity-dependent fluorescence spectra (the sensitivity on polarity is at most 26 times higher than the old vibrationally resolved patterns), and the sensitivity well remains when it is copolymerized in a polymer. The vibrationally resolved spectrum of this pyrene acylhydrazone is a powerful fluorescence probe, which would be as useful as the pyrene excimer probe nowadays popular. This article is protected by copyright. All rights reserved.

Synergistic effect and co-adsorption mechanism of a mixed collector on the flotation separation of spodumene from feldspar

In this study, the flotation separation of spodumene from feldspar was achieved using mixed collector of sodium oleate (NaOL)/cetyl trimethylammonium bromide (CTAB). Micro-flotation experiments show that the selective flotation separation of the two minerals could not be achieved in the presence of single collector under the pH range of 2–12, but the they could be effectively separated using mixed collector at the NaOL-to-CTAB molar ratio (MR) of 7:1 at pH 6.0 Artificial mixed minerals tests prove the effective flotation separation effect of the mixed NaOL/CTAB at pH 6.0. Analyses of bubble collision-attachment show that when using mixed NaOL/CTAB as the collector, the bubble could quickly form a three-phase contact (TPC) line on spodumene surface (tTPC=396 ms), but the bubble did not form TPC line on feldspar surface (tTPC＞2000 ms), suggesting a much stronger hydrophobic surface of spodumene. Adsorption amount tests show the much higher adsorption density of mixed NaOL/CTAB on spodumene surface than feldspar, moreover, CTAB promoted the NaOL adsorption on spodumene surface, but it hindered the NaOL adsorption on feldspar surface. The surface and thermodynamic parameters (CMC, γcmc, ∆Gm0, Γmax, Amin) obtained from surface analyses demonstrate higher surface activity and denser molecular arrangement in mixed NaOL/CTAB system than that in the individual system, indicating a positive synergistic effect of mixed collector. Pyrene fluorescence spectrum analyses present the lower critical micelle concentration (CMC) value and polarity of the mixed NaOL/CTAB than their individual components, suggesting that the mixture had much stronger hydrophobicity and was more likely to form micelles than single collector. All the tests were conducted at temperature of 25 ℃.