Materials In Aqueous Solution Research Articles

A Novel Fluorescent Probe for Determination of pH and Viscosity Based on a Highly Water-Soluble 1,8-Naphthalimide Rotor.

A novel highly water-soluble 1,8-naphthalimide with pH and viscosity-sensing fluorescence was synthesized and investigated. The synthesized compound was designed as a molecular device in which a molecular rotor and molecular "off-on" switcher were integrated. In order to obtain a TICT driven molecular motion at C-4 position of the 1,8-naphthalimide fluorophore, a 4-methylpiperazinyl fragment was introduced. The molecular motion was confirmed after photophysical investigation in solvents with different viscosity; furthermore, the fluorescence-sensing properties of the examined compound were investigated in 100% aqueous medium and it was found that it could be used as an efficient fluorescent probe for pH. Due to the non-emissive deexcitation nature of the TICT fluorophore, the novel system showed low yellow-green emission, which represented "power-on"/"rotor-on" state. The protonation of the methylpiperazine amine destabilized the TICT process, which was accompanied by fluorescence enhancement indicating a "power-on"/"rotor-off" state of the system. The results obtained clearly illustrated the great potential of the synthesized compound to serve as pH- and viscosity-sensing material in aqueous solution.

Solar light-responsive α-Fe2O3/CdS/g-C3N4 ternary photocatalyst for photocatalytic hydrogen production and photodegradation of methylene blue

Photocatalytic degradation of waste materials in aqueous solutions, as well as photocatalytic hydrogen generation, were investigated for remediation of environment and renewable energy production. α-Fe 2 O 3 and CdS are attractive visible-light-driven semiconductor photocatalysts because of their inexpensive cost, simple production methods, and stability. Whereas, its implementations were limited by the photocorrosion, narrow optical band gap for solar-light operations and poor separation of photogenerated electron-hole pair. To increase the performance of α-Fe 2 O 3 , CdS, α-Fe 2 O 3 /CdS, and g-C 3 N 4 ; a ternary nanocomposite (α-Fe 2 O 3 /CdS/g-C 3 N 4 ) was designed. To obtain binary structure, CdS nanoparticles were overgrown on α-Fe 2 O 3 nanorods-cubes using a simple wet-chemical process, and as-prepared g-C 3 N 4 was decorated with binary composite. XRD, SEM, XPS, BET, UV–Visible spectrometry, FT-IR, PL and EIS were employed to investigate the crystal structures, surface morphology, optical properties, functional groups and electrochemical characteristics. Considering the optical absorption properties, the photocatalytic studies were performed for hydrogen production and MB dye degradation under solar light irradiation. Among the synthesized semiconductors, the ternary material had the highest photocatalytic hydrogen evolution, 165 µmol g −1 2 h −1 from water. Within 120 min, the photocatalytic performance resulted in 99.4% degradation of the MB. The higher activities were attributed to Z-scheme mechanism, optical band levels and strict heterojunctions of the photocatalysts that induces an influential electron-hole separation, subsequently rapid diffusion of photogenerated charge between components and also the optical bandgap value of the ternary structure that more convenient for solar lights applications. This work paves a way for improvement of photocatalysts working in practical conditions of pollution and energy issues. • The α-Fe 2 O 3 /CdS/g-C 3 N 4 ternary heterostructured material was synthesized. • Photocatalytic hydrogen production was studied. • Photocatalytic degradation was studied. • The α-Fe 2 O 3 /CdS/g-C 3 N 4 ternary nanocomposite showed best photocatalytic properties under solar light irradiation.

Physicochemical and Adsorption Properties of Some Carbon Materials in Aqueous Solutions

Physicochemical and Adsorption Properties of Some Carbon Materials in Aqueous Solutions

Chemical Composition and Rheological Properties of Seed Mucilages of Various Yellow- and Brown-Seeded Flax (Linum usitatissimum L.) Cultivars.

When seeds sown in the soil become wet, their hulls secrete viscous matter that can retain water and thus support germination. Flaxseed mucilage (FSM) is an example of such a material and is attractive for food, cosmetic, and pharmaceutical applications due to its suitable rheological properties. FSM consists mainly of two polysaccharides, namely, arabinoxylan and rhamnogalacturonan I, and it also contains some proteins, minerals, and phenolic compounds. The genotype and the year of the flax harvest can significantly affect the composition and functional properties of FSM. In this work, FSM samples were isolated from flax seeds of different cultivars and harvest years, and their structural and rheological properties were compared using statistical methods. The samples showed significant variability in composition and rheological properties depending on the cultivar and storage time. It was found that the ratio of two polysaccharide fractions and the contribution of less-prevalent proteins are important factors determining the rheological parameters of FSM, characterizing the shear-thinning, thixotropic, and dynamic viscoelastic behavior of this material in aqueous solutions. The yield strength and the hysteresis loop were found to be associated with the contribution of the pectin fraction, which included homogalacturonan and rhamnogalacturonan I. In contrast, the shear-thinning and especially the dynamic viscoelastic properties depended on the arabinoxylan content. Proteins also affected the viscoelastic properties and maintained the elastic component of FSM in the solution. The above structural and rheological characteristics should be taken into account when considering effective applications for this material.

Experimental investigation of the adsorption process of the surfactant-nanoparticle combination onto the carbonate reservoir rock surface in the enhanced oil recovery (EOR) process

Nowadays, the application of materials, such as surfactants and nanoparticles in enhanced oil recovery (EOR) projects has been widely studied. So, the adsorption process of these substances is one of the important methods to increase the oil recovery factor from carbonate oil reservoirs. However, understanding how the surfactant-nanoparticle combination interacts through the adsorption process onto the carbonate reservoir rocks surface is not well discussed. In this paper, the adsorption process of saponin extracted from the Glycyrrhiza glabra plant as a natural non-ionic surfactant (GG surfactant) with the presence of hydrophilic titanium dioxide nanoparticles (HITNPs) onto the carbonate reservoir rock (adsorbent) surface has been investigated for mobilizing the crude oil remaining to increase the oil recovery factor. Hence, this study highlights the equilibrium adsorption rate and the adsorption kinetics of these materials in aqueous solutions for chemical EOR schemes. Also, analyses of X-ray diffraction (XRD) spectrometry, scanning electron microscopy (SEM), and Fourier transform infrared (FTIR) spectroscopy have been applied to confirm and determine the physicochemical changes and properties of materials. To evaluate the adsorption rate and the relationship between surfactant concentration with the presence of nanoparticles and adsorption density on the adsorbent surface in the aqueous phase, batch adsorption tests under atmospheric conditions at different concentrations and times have been used to comprehend the impact of adsorbate dose on the sorption efficiency. Therefore, the electrical conductivity (EC) technique was used for measuring the adsorption rate of surfactant with the presence of HITNPs in the aqueous phase on the adsorbent surface. The adsorption kinetics process was experimentally investigated at laboratory temperature (25 °C) by monitoring the uptake of solutions on the adsorbent surface as a function of time. The experimental adsorption data were also examined by different equilibrium and kinetic models of adsorption. Hence, the adsorption parameters were determined for each model. Langmuir isotherm was the best model according to the higher values of the correlation coefficient (R2) for GG surfactant and surfactant nanofluid solutions on the adsorbent surface. Furthermore, the pseudo-second-order kinetic model could satisfactorily estimate the adsorption kinetics of GG surfactant and surfactant nanofluid solutions on the adsorbent surface. Results indicated that the adsorption process of GG surfactant and surfactant nanofluid solutions on the adsorbent surface is characterized by a short period of rapid adsorption, followed by a long period of slower adsorption. Moreover, the results of the IFT experiment of these materials showed that GG surfactant and surfactant nanofluid solutions could significantly reduce the IFT value between oil and water system. Finally, the results obtained from this study can help in selecting appropriate surfactants and metal oxide nanoparticles for the design of EOR projects, especially reservoir simulation schemes and chemical flooding processes for carbonate oil reservoirs.

Red-Emissive Organic Room-Temperature Phosphorescence Material for Time-Resolved Luminescence Bioimaging

Organic room-temperature phosphorescence (RTP) materials have been used in high-resolution imaging. However, the development of long-wavelength-emission RTP materials in aqueous solution remains a ...

Stability of a Rolled-Up Conformation State for Two-Dimensional Materials in Aqueous Solutions.

Two-dimensional (2D) materials can roll up, forming stable scrolls under suitable conditions. However, the great diversity of materials and fabrication techniques has resulted in a huge parameter space significantly complicating the theoretical description of scrolls. In this Letter, we describe a universal binding energy of scrolls determined solely by their material parameters, the bending stiffness, and the Hamaker coefficient. Aiming to predict the stability of functionalized scrolls in water solutions, we consider the electrostatic double-layer repulsion force that may overcome the binding energy and flatten the scrolls. Our predictions are represented as comprehensive maps indicating the stable and unstable regions of a rolled-up conformation state in the space of material and external parameters. While focusing mostly on functionalized graphene in this work, our approach is applicable to the whole range of 2D materials able to form scrolls.

Natural Pigment from Madder Plant as an Eco-Friendly Cathode Material for Aqueous Li and Na-Ion Batteries

Modifying commercial Li-ion batteries to become more environmentally friendly is of a growing concern. This paper provides an examination of a potential replacement for commercial cathode material using a naturally occurring purpurin in aqueous solutions of lithium and sodium salts. The purpurin is extracted from the Madder plant (Rubia tinctorum) and characterized through XRPD, FTIR, and SEM methods. The intercalation and de-intercalation capacities obtained for the purpurin as a cathode material in the aqueous solution of LiNO3 are approximately 40 mAh g−1. Compared to the capacity of ∼35 mAh g−1 obtained for commercially used transition metal oxides in an aqueous solution of Li salt, results presented make the purpurin a promising material for the “green” development of Li-ion batteries. Although the initial purpurin capacity in NaNO3 solution is almost doubled (∼73 mA h g−1) compared to that of Li-salt, it is unstable and fades during cycling. The possible explanation of the electrochemical behavior of purpurin as the cathode material in aqueous solutions of Li and Na salts is discussed in detail.

Efficient removal of Th(IV) from aqueous solution by reusable porous Al2O3-SiO2 composites

In this study, porous Al2O3-SiO2 composite materials were successfully constructed and applied to remove Th(IV) in aqueous solution. There was a large amount of OH− on the surface of Al2O3-SiO2 composite materials in aqueous solution, which would effectively capture positively charged Th(IV) to form a complex. The maximum adsorption capacity reached 361.60 mg g−1 and the adsorption percentage was as high as 99.9% in low initial concentration of Th(IV) solution. In addition, it was worth noting that the adsorption efficiency could maintain more than 90% even after 5 cycles. In view of these results, porous Al2O3-SiO2 composite materials should be considered to be an efficient and reusable adsorbent for Th(IV).

Design and structural of Sm-doped SbFeO3 nanopowders and immobilized on poly(ethylene oxide) for efficient photocatalysis and hydrogen generation under visible light irradiation

In this study, the samarium doped SbFeO3 nanoparticles/poly (ethylene oxide) was prepared via the hydrothermal and chemical technique. The prepared materials were characterized by X-ray diffraction, nitrogen adsorption/desorption isotherm, field-emission scanning electron microscopy, dynamic light scattering and UV–visible spectroscopy analysis. Photocatalysis degradation studies are conducted for methyl orange dye and benzene degradation by using the prepared materials in aqueous solution under sunlight irradiation. The degradation efficiency of methyl orange and benzene were 99.23%, and 93.87%, respectively. The solar degradation of the organic compounds indicated the substantial performance of Sm-SbFeO3/poly (ethylene oxide) photocatalyst rather than using the pure SFO nanoparticles. The performance of Sm-SbFeO3/poly (ethylene oxide) was examined for photocatalytic hydrogen evolution. The H2 production rate of were 76.74 µmol g−1 h−1.

Visible-light excitable thermally activated delayed fluorescence in aqueous solution from F, N-doped carbon dots confined in silica nanoparticles

Visible light has better biocompatibility and is more accessible for anti-counterfeiting compared to UV light. However, the synthesis of visible light excitable CDs-based long afterglow materials is still a challenge, especially in aqueous solution. Herein, we provide the first example of visible-light excitable thermally activated delayed fluorescence (TADF) in aqueous solution by confining the fluorine and nitrogen co-doped CDs in silica nanoparticles (F, NCDs@SiO2). The hydrogen network and covalent bonds effectively protect the triplet excitons from quenching by water oxygen, so the nanoparticles can produce long-lived TADF in aqueous solutions under the excitation of white light. Meanwhile, the large number of silanol groups on the surface of amorphous silicon endows F, NCDs@SiO2 with water solubility making them possible for time-resolved probes. We reveal that fluorine doping is essential for obtaining visible-light excitable TADF, which redshifts the excitation spectra and narrows the energy level between the singlet and triplet states through strong electron-withdrawing effect and heavy-atom effects. Our work provides a new strategy for the development of visible-light-excited TADF materials in aqueous solution and potential applications of CDs in information encryption, temperature sensor and time-resolved fluorescence bioimaging.

Tetraphenylethylene based amphiphilic derivatives: The self-assembly, photo-responsiveness and their application for erasable fluorescent ink

Since the discovery of aggregation induced emission (AIE) phenomenon, various stimuli-responsive materials have been rapidly developed. However, the development of self-assembled amphiphilic light-responsive materials in aqueous solution needs to be solved urgently. In this work, three new amphiphilic tetraphenylethylene (TPE) derivatives (TPE-1, TPE-2 and TPE-3) with AIE properties and photochromism were synthesized and investigated. Owing to the different electron-donating abilities of the three groups attached to TPE units, the TPE-1, TPE-2 and TPE-3 displayed blue-green, yellow-green, and orange fluorescence emission in the aggregation state respectively. Furthermore, ordered nanoparticles formed via self-assembly in aqueous solution showed interesting photocyclization behaviors, which lead to fluorescence quenching under ultraviolet light irradiation (λ = 365 nm). Therefore, the compounds can be used as anti-counterfeiting ink in the information encryption due to their amphiphilicity and photo-responsiveness. This work contributes new members to the amphiphilic light-responsive materials family and demonstrates the potential for applications in the fields of optical information storage, information security protection, and erase/rewrite systems.

Nano zero valent iron (nZVI) particles for the removal of heavy metals (Cd2+, Cu2+ and Pb2+) from aqueous solutions.

For the past 15 years, nanoscale metallic iron (nZVI) has been investigated as a new tool for the treatment of heavy metal contaminated water. The removal mechanisms depend on the type of heavy metals and their thermodynamic properties. A metal whose redox potential is more negative or close to the reduction potential of Fe(0) is removed by the reduction process, while the others will be mediated by precipitation, complexation or other sorption processes. This review summarises our contemporary knowledge of nZVI aqueous chemistry, synthesis methods, mechanisms and actions (practical experiences) of heavy metal (Cd, Cu and Pb) removal and challenges of nZVI practical applications. Its inner core (iron(0)) has reducing ability towards pollutants, while the iron oxide (FeO) outer shell provides reaction sites for chemisorption and electrostatic interactions with heavy metals. Emerging studies highlighted that nZVI surfaces will have negatively charged species at higher pH and have good affinity for the removal of positively charged species such as heavy metals. Different sizes, shapes and properties of nZVI have been produced using various methods. Ferric salt reduction methods are the most common methods to produce stable and fine graded nZVI. Higher uptake of copper(ii), lead(ii) and cadmium(ii) has also been reported by various scholars. Practical pilot tests have been conducted to remove heavy metals, which gave highly satisfactory results. Challenges such as agglomeration, sedimentation, magnetic susceptibility, sorption to other fine materials in aqueous solution and toxicity of microbiomes have been reported. Emerging studies have highlighted the prospects of industrial level application of nano zero valent particles for the remediation of heavy metals and other pollutants from various industries.

Mineral plastic foams.

We describe a route to synthesize a mechanically stable, non-flammable poly(acrylic acid)-calcium salt (the so-called mineral plastic) foam whose structure can be tailored. Main steps of the foam synthesis are: (1) foaming of the PAA-containing solution, (2) gelation of the continuous foam phase, and (3) drying of the hydrogel foam. The main challenge was to formulate an aqueous solution with a large amount of poly(acrylic acid), PAA, and calcium to yield a mechanically stable foam. The resulting PAA-based solid foams with pore sizes of around 220 μm can easily be dissolved, i.e. recycled, in an acidic solution.

Possibilities for Optimization of Industrial Alkaline Steeping of Wood-Based Cellulose Fibers.

Steeping of cellulosic materials in aqueous solution of NaOH is a common pre-treatment in several industrial processes for production of cellulose-based products, including viscose fibers. This study investigated whether the span of commonly applied process settings has the potential for process optimization regarding purity, yield, and degree of transformation to alkali cellulose. A hardwood kraft dissolving pulp was extracted with 17–20 wt% aq. NaOH at 40−50 °C. The regenerated residue of the pulp was characterized regarding its chemical composition, molecular structure, and cellulose conformation. Yield was shown to be favored primarily by low temperature and secondly by high alkali concentration. Purity of xylan developed inversely. Both purity of xylan and yield varied over the applied span of settings to an extent which makes case-adapted process optimization meaningful. Decreasing the steeping temperature by 2 °C increased xylan content in the residue with 0.13%-units over the whole span of applied alkali concentrations, while yield increased by 0.15%-units when extracting with 17 wt% aq. NaOH, and by 0.20%-units when extracting with 20 wt%. Moreover, the yield-favoring conditions resulted in a narrower molecular weight distribution. The degree of transformation via alkali cellulose to cellulose II, as determined with Raman spectroscopy, was found to be high at all extraction settings applied.

Multifunctionality of Polypyrrole Polyethyleneoxide Composites: Concurrent Sensing, Actuation and Energy Storage.

In films of conducting polymers, the electrochemical reaction(s) drive the simultaneous variation of different material properties (reaction multifunctionality). Here, we present a parallel study of actuation-sensing-energy storage triple functionality of polypyrrole (PPy) blends with dodecylbenzenesulfonate (DBS-), PPy/DBS, without and with inclusion of polyethyleneoxide, PPy-PEO/DBS. The characterization of the response of both materials in aqueous solutions of four different salts indicated that all of the actuating, sensing and charge storage responses were, independent of the electrolyte, present for both materials, but stronger for the PPy-PEO/DBS films: 1.4× higher strains, 1.3× higher specific charge densities, 2.5× higher specific capacitances and increased ion-sensitivity towards the studied counterions. For both materials, the reaction energy, the material potential and the strain variations adapt to and sense the electrical and chemical (exchanged cation) conditions. The driving and the response of actuation, sensing and charge can be controlled/read, simultaneously, via just two connecting wires. Only the cooperative actuation of chemical macromolecular motors from functional cells has such chemical multifunctionality.

Computational Study of Corrosion in Steel in Aqueous Solution: a Review

Corrosion affects most of the material strength and causes damages to the material and the structure. Corrosion has become a major problem of material stability and it is difficult to predict its phenomenon. It can happen in any environment and can deteriorate metallic material. Computational models have been implemented in order to study and predict the phenomenon and the evolution of the corrosion. This paper presents a critical review of the computational model from various softwares that have been developed to observe the growth and the behaviour of corrosion on the metallic material in aqueous solution. The metallic material undergoes redox reaction with the presence of oxygen and water to form corrosion. This paper reviews the corrosion model of steel at different pH, temperatures and types of ionic species. The pH of the aqueous solution is either acidic or alkaline which will determine the rate of corrosion by the ionic reaction in the electrolyte.

A multiresponsive luminescent probe of antibiotics, pesticides, Fe3+ and ascorbic acid with a Cadmium(II) metal-organic framework

A novel two-dimensional (2D) cadmium-based metal-organic framework [Cd2(HDDB)(bimpy)(NMP)(H2O)]·3H2O (1) (H5DDB = 3,5-di(2′,4′-dicarboxylphenyl)benozoic acid and bimpy = 3,5-bis(1-imidazolyl)pyridine) has been constructed by solvothermal method, which exhibits good water stability, pH stability and excellent photoluminescence properties. Complex 1 reveals a fluorescence turn-off behaviour towards nitrofuran/nitroimidazole antibiotics and DCN pesticide due to PET (photoinduced electron transfer) and FRET (fluorescence resonance energy transfer). Interestingly, complex 1 can be designed as an “on-off-on” fluorescence probe to detect Fe3+ ion and ascorbic acid (AA). The fluorescence of complex 1 can be quenched by Fe3+ ion to form a Fe3+@1 hybrid system, which can be ascribed to the FRET process and the week interaction between Fe3+ and 1. Then, after gradually adding AA into Fe3+@1 system, the fluorescence intensity of Fe3+@1 fluorescence-silent system was recovered (turn on). The possible fluorescence turn-on mechanism is the elimination of FRET process between Fe3+ and complex 1. This work represents the first example of recognition of nitrofuran/nitroimidazole antibiotics, DCN pesticide, Fe3+ ion and AA based on a MOF material in aqueous solution.

Underlying Processes Driving the Evolution of Nanoporous Silica in Water and Electrolyte Solutions

In this study, we related the alteration of mesoporous materials in aqueous solutions to the properties of confined water in the presence of ions, that is, its structure and its dynamics. To reach this goal, we have determined and quantified the evolution of the morphology of hexagonal mesoporous silica-based materials, that is, MCM-41 (mean pore size of 2.9 nm and dense pore wall) and SBA-15 (mean pore size of 6.8 nm and microporous pore wall), during their alteration in water and electrolyte solutions with ions presenting various kosmotropic properties ([XCl2] = 1 M and X = Ba, Ca, Mg) at 50 °C by in situ small and wide angle X-ray scattering. The experimental results and the calculated small-angle X-ray scattering spectra have demonstrated that the alteration behavior is strongly dependent on the type of silica and the water properties (water dynamics at a picosecond time scale and water structure) related to the confinement size, the nature of the cations, and their surface ion excesses. For MCM-41 silica, having reduced water dynamics, the alteration behavior is mainly driven by silica hydrolysis—recondensation/precipitation processes leading to a pore deformation and a possible precipitation of XCl2 metastable phases partially clogging the pores. In case of SBA-15, its alteration behavior in aqueous solutions starts with an initial increase of the pore size and the formation of an alteration layer within its microporosity which grows following a diffusive process of the solution. Inside the microporosity, similar alteration processes to MCM-41 silica occur. These recondensation/precipitation processes may continue until a thermodynamically stable silica phase is formed. The results obtained within the scope of this work revealed the importance of the influence of the dynamics and the structure of water in chemical reactions taking place in confined media filled with water and ions.

Construction of lanthanide-containing ratiometric probe for facile anthrax biomarker detection.

Since the outbreak of anthrax attack in the United States in 2001, much effort has been done to detect anthrax spores. In this paper, a simple and facile lanthanide-containing ratiometric luminescence "turn on" probe is constructed to achieve sensitive and selective detection of anthrax spores biomarker - pyridine-2,6-carboxylic acid (DPA) by simply mixing Tb3+, sodium polyacrylate as well as red internal reference which could exclude some disturbance from the luminescence of biological tissue. Our probe shows remarkable luminescence enhancement upon addition of DPA. The detection limit for DPA is measured as 35.8nM with a wide work range of 0-66.7μM. Besides, our probe enables distinguish DPA selectively from numerous interfering materials in aqueous solution. Further test strip experiments demonstrate the potential practical application of our probe in DPA detection.