Highly Thermo-Conductive Three-Dimensional Graphene Aqueous Medium

Highly thermo-conductive aqueous medium is a crucial premise to demonstrate high-performance thermal-related applications.Graphene has the diamond comparable thermal conductivity,while the intrinsic two-dimensional reality will result in strong anisotropic thermal conductivity and wrinkles or even crumples that significantly sacrifices its inherent properties in practical applications.One strategy to overcome this is to use three-dimensional(3D)architecture of graphene.Herein,3D graphene structure with covalent-bonding nanofins(3D-GS-CBF)is proposed,which is then used as the filler to demonstrate effective aqueous medium.The thermal conductivity and thermal conductivity enhancement efficiency of 3D-GS-CBF(0.26 vol%)aqueous medium can be as high as 2.61 W m-1 K-1 and 1300%,respectively,around six times larger than highest value of the existed aqueous mediums.Meanwhile,3D-GS-CBF can be stable in the solution even after 6 months,addressing the instability issues of conventional graphene networks.A multiscale modeling including non-equilibrium molecular dynamics simulations and heat conduction model is applied to interpret experimental results.3D-GS-CBF aqueous medium can largely improve the solar vapor evaporation rate(by 1.5 times)that are even comparable to the interfacial heating system;meanwhile,its cooling performance is also superior to commercial coolant in thermal management applications.

Evaluation of Biodegradation in Aqueous Medium of Poly(Hydroxybutyrate-Co-Hydroxyvalerate)/Carbon Nanotubes Films in Respirometric System

Biodegradable polymers have been increasingly used for scientific and commercial applications because they are similar to some conventional thermoplastics and exhibit the ability of self-degradation.Poly(3-hydroxybutyrate-co-3-hydroxyvalerate)(PHBV)nanocomposites films with 1 and 2 wt% of carbon nanotubes(CNT)were prepared by solution mixing,followed by solvent evaporation.In this work,PHBV/CNT nanocomposites were submitted to biodegradation in an aqueous medium for 34 days through a respirometric system.Then,the PHBV films were analyzed by the CO2 production and mineralization as a response of a microbial attack,which was monitored by back titration during all the experiment.The films were also characterized by measuring the weight loss;crystallinity was evaluated by differential scanning calorimetry(DSC)and the surface morphology by scanning electron microscopy(SEM).By analyzing the weight loss of the films,it was observed that adding CNT increases the resistance to biodegradation process.The obtained values of CO2 production and mineralization of the samples,as well as the values of weight loss,showed that the biodegradation of PHBV/CNT nanocomposites was minor in comparison to neat PHBV.The addition of CNT in PHBV matrix influences the surface morphology,causing the presence of cavities and an increase of roughness.

Facile, Direct Reaction of Benzaldehydes to 3-Arylprop-2-Enoic Acids and 3-Arylprop-2-Ynoic Acids in Aqueous Medium

Wittig reactions of benzaldehydes, alkanals, and cycloalkanals as well as of acetophenones are carried out with alkoxycarbonyl methylidenetriphenylphosphoranes in 10 w% aqueous NaOH, where the cinnamates and alkenoates produced are hydrolysed in situ and the corresponding acids are obtained after mostly simple extractive work-up, often without employing organic solvents. Under the same conditions, benzaldehydes are reacted with alkoxycarbonyl bromomethy-lidenephosphorane to produce 3-arylprop-2-ynoic acids (arylpropiolic acids).

Un-catalyzed tandem Knoevenagel-Michael reaction for the synthesis of 4,4'-(arylmethylene)bis(1H-pyrazol-5-ols)in aqueous medium

An environmentally benign un-catalyzed one-pot synthesis of 4,4＇-（arylmethylene）bis（1H-pyrazol-5-ols） has been reported via tandem Knoevenagel-Michael reaction of aldehydes with two equivalents of 3-methyl-1-phenyl-1H-pyrazol-5（4H）-one in aqueous medium.

A Novel One-pot Synthesis of Biaryl Derivatives by Sequential Strategies via Suzuki Coupling/Knoevenagel Condensation in Aqueous Medium at Room Temperature

A novel one-pot synthesis of biaryl derivatives has been developed starting from bromobenzaldehyde and phenylboronic acid in the presence of activated methylene compounds via sequential Suzuki coupling/Knoevenagel condensation in aqueous isopropanol medium at room temperature. Significantly, this strategy afforded a straightforward and efficient approach to construct original biaryls in which a new carbon double bond bound to activated moieties such as nitrile, ester and amide is formed from three simple substrates in a one-pot procedure. Moreover, a wide scope of substrates could effectively participate in the process affording the target products in moderate to excellent yields.

An Efficient Synthesis of N-Substituted-3-aryl-3-（2-hydroxy-4,4- dimethyl-6-oxocyclohex-l-enyl）propanamides by Four-component Reaction in Aqueous Medium

A mild and efficient synthesis of N-substituted-3-aryl-3-（2-hydroxy-4,4-dimethyl-6-oxocyclohex-l- enyl）propanamides via four-component reaction of an aldehyde, amine, Meldrum＇s acid and 5,5-dimethylcyclo- hexane-1,3-dione in the presence of benzyltriethylammonium chloride （TEBAC） in aqueous medium is described. This method has the advantages of accessible starting materials, good yields, mild reaction conditions and eco- friendliness.

Batch equilibrium studies on the adsorptive capacity of powdered and pelleted maize tassel to remove PFOA and PFOS from aqueous medium

This study was aimed at evaluating the potential of raw maize tassel powder and pellets to remove PFOA and PFOS from water.Batch experiments were first conducted using ultrapure water to investigate the effects of pH,adsorbent dosage,initial PFASs concentration,contact time and temperature in adsorption efficiency of powdered and pelleted maize tassel.The optimum conditions for the removal of PFOA/PFOS observed for both maize tassel powder and pellets were as follows:pH 2.0,adsorbate initial concentrations of 20 mg g1,adsorbent dosage of 0.5 g(20 pellets),1 h contact time,all at 25℃.These optimum conditions were,thereafter,applied to surface water samples from Apies River in Pretoria,spiked with 20 mg L^(-1)PFOS/PFOA.Shimadzu LC-MS/MS was employed in analysis and the Langmuir and Freundlich isotherm models were used to determine the types of adsorption mechanism.High percentage removal 91.3%and 89.7%for PFOA and PFOS respectively using both MT powder and pellets were achieved.The maximum adsorption capacities identified for the monolayer of the Langmuir isotherm model was found to be between 41.6 mg g^(-1)and 58.82 mg g^(-1)for PFOA using powder and pellets respectively;and between 42.37 mg g^(-1)and 176.5 mg g^(-1)for PFOS for the same adsorbents respectively.These results showed very insignificant conformity to the Langmuir model;therefore it can be assumed that the Langmuir model was not obeyed.However,the experiments proved to be primarily consistent with the Freundlich model,with high correlation coefficient(R2)values ranging from 0.900 to 0.998 for both PFOA and PFOS.Maximum adsorption capacities of 142.8 mg g^(-1)and 78.57 mg g^(-1)for PFOA and 107.4 mg g^(-1)and 85.7 mg g^(-1)for PFOS at 25℃using both powder and pellets respectively were obtained suggesting that adsorption took place on heterogeneous layers for both targeted PFASs.

Dispersion polymerization of anionic polyacrylamide in an aqueous salt medium

Anionic polyacrylamide dispersions were prepared by dispersion polymerization in an aqueous salt medium, using acrylamide（AM） and acrylic acid（AA） as monomers and anionic polyelectrolytes as stabilizer. Effects of salt concentration, and molecular weight and concentration of stabilizers on the stability of the dispersions were investigated using a HAAKE rheometer and optical microscopy. The results showed that stable anionic polyacrylamide dispersions, consisting of smooth, spherical, polydisperse particles, could be obtained under the conditions of salt concentration ranging from 26 wt% to 30 wt%, concentration of stabilizers from 1.2 wt% to 1.8 wt%, and intrinsic viscosity of stabilizers from 2.98 dL·g^-1 to 3.74 dL·g^-1. The apparent viscosity of the stable dispersions changed very little with the shear rate, showing Newton fluid behavior.

Ultrasonic-enhanced Stereoselective Debromination of vic-Dibromides to Alkenes with Metallic Zinc Powder in Aqueous Media

Carbon-carbon double bond functional groups are often protected through a popular bromination/debromination method because of their reactivity. An ultrasonic-enhanced stereoselective debromination of vic-dibromides with metallic zinc powder in aqueous media has been developed, which generates E-alkenes with excellent yields. The reactivity of vic-dibromides decreases in the order of 1,2-dibromo-1,2-diphenylethane>1,2-dibromo-1-phenylethane>1,2-dibromo-1,2-dialkylethane.

Polyethylene Glycol as Support and Phase Transfer Catalyst in Aqueous Palladium-catalyzed Liquid-phase Synthesis

Excellent yields and purity were obtained in the aqueous medium Suzuki, Sonogashira, Stille and Heck reactions using palladium (II) as catalyst in liquid phase synthesis. Polyethylene glycol (PEG) acted as soluble polymeric support and phase transfer catalyst as well.

OXIDATIVE POLYMERIZATION BEHAVIOR OF 2,6-DIMETHYLPHENOL IN AQUEOUS MEDIA WITH POTASSIUM FERRICYANIDE

The effects of potassium ferricyanide,sodium n-dodecyl sulfate,sodium hydroxide and temperature on the molecular weight and the yield of poly(2,6-dimethyl-1,4-phenylene oxide)(PPO) synthesized in an aqueous medium were studied.It was found that oxygen in air had little influence on the oxidative polymerization of 2,6-dimethylphenol(DMP) in the aqueous medium,and potassium ferricyanide was only an oxidant during the oxidative polymerization of DMP.Sodium n-dodecyl sulfate could stabilize polymer particles an...

One-pot synthesis of 1,3,4-oxadiazole-5-thioethers in water

An efficient and environmental-friendly one-pot procedure has been developed for the synthesis of 1,3,4-oxadiazole-5- thioethers by the reaction of acylhydrazine with carbon disulfide and organic halides or α, β-unsaturated carbonyl compounds. The reactions were carried out in water in the presence of potassium phosphate within 2-4 h to afford the expected products in excellent yields.

Covalent triazine framework with efficient photocatalytic activity in aqueous and solid media

Covalent triazine frameworks(CTFs)have been recently employed for visible light-driven photocatalysis due to their unique optical and electronic properties.However,the usually highly hydrophobic nature of CTFs,which originates from their overall aromatic backbone,leads to limitations of CTFs for applications in aqueous media.In this study,we aim to extend the range of the application media of CTFs and design hybrid material of a CTF and mesoporous silica(SBA-15)for efficient photocatalysis in aqueous medium.A thiophene-containing CTF was directly synthesized in mesopores of SBA-15.Due to the high surface area and the added hydrophilic properties by silica,the hybrid material demonstrated excellent adsorption of organic molecules in water.This leads not only to high photocatalytic performance of the hybrid material for the degradation of organic dyes in water,but also for efficient photocatalysis in solvent-free and solid state.Furthermore,the reusability,stability and easy recovery of the hybrid material offers promising metal-free heterogeneous photocatalyst for broader applications in different reaction media.

A Barbier type reaction promoted by in situ formed active metal bismuth from NaBH_4 and BiCl_3 in aqueous media

In the presence of active metal bismuth (Bi) which was prepared from the combination of bismuth trichloride and sodium borohydride,aldehydes have been found to react with allyl bromide in aqueous media,and the corresponding homoallylic alcohols were obtained in excellent yields with high chemo-and stereoselectivity.

Functional groups assisted-photoinduced electron transfer-mediated highly fluorescent metal-organic framework quantum dot composite for selective detection of mercury(Ⅱ) in water

The presence of toxic mercury (Ⅱ) in water is an ever-growing problem on earth that has various harmful effect on human health and aquatic living organisms.Therefore,detection of mercury (Ⅱ) in water is very much crucial and several researches are going on in this topic.Metal-organic frameworks (MOFs) are considered as an effective device for sensing of toxic heavy metal ions in water.The tunable functionalities with large surface area of highly semiconducting MOFs enhance its activity towards fluorescence sensing.In this study,we are reporting one highly selective and sensitive luminescent sensor for the detection of mercury (Ⅱ) in water.A series of binary MOF composites were synthesized using in-situ solvothermal synthetic technique for fluorescence sensing of Hg^(2+)in water.The welldistributed graphitic carbon nitride quantum dots on porous zirconium-based MOF improve Hg^(2+)sensing activity in water owing to their great electronic and optical properties.The binary MOF composite (2) i.e.,the sensor exhibited excellent limit of detection (LOD) value of 2.4 nmol/L for Hg^(2+).The sensor also exhibited excellent performance for mercury (Ⅱ)detection in real water samples.The characterizations of the synthesized materials were done using various spectroscopic techniques and the fluorescence sensing mechanism was studied.

The mechanism and kinetics of oil shale pyrolysis in the presence of water

The hydrous thermo-simulation experiments on oil shale sample from Liushuhe basin have been performed using autoclave.The mechanism and kinetics of oil shale pyrolysis were investigated.The formation mechanism of pyrolysates including retorting gas,oil and bitumen,were evaluated in the presence of saturated and unsaturated water,respectively.The results show that the physicochemical properties of water have greatly changed in high temperature and pressure.At the same time,water has three kinds of effect on the oil shale pyrolysis,including the protection of free radical,catalytic action and swelling.The pyrolysis temperature was carried out about 70
C earlier,and the generated processing of hydrocarbon would be easier under the aqueous.The consecutive first order reaction model involving bitumen as an intermediate product was used in the data analysis in order to determine the pyrolysis kinetic parameters.It was found that the apparent activation energy of kerogen pyrolysis was lower than bitumen pyrolysis.

H_6P_2W_(18)O_(62)á18H_2O: A green and reusable catalyst for one-pot synthesis of pyrano[4,3-b]pyrans in water

A convenient,effcient and environmentally benign procedure has been developed for the synthesis of pyrano[4,3-b]pyran derivatives via a one-pot,three-component reaction of 4-hydroxy-6-methylpyran-2-one,aldehydes and malononitrile in water using H6P2W18O62á18H2O as catalyst.Reusability of the catalyst and reaction media,short reaction times and easy isolation of products are some added advantages of the present methodology.

β-Cyclodextrin as a supramolecular catalyst for the synthesis of 2Hindazolo[2,1-b]phthalazine-trione derivatives in water and their antimicrobial activities

An efficient and green method has been developed for the synthesis of 2H-indazolo[2,1-b]phthalazinetriones derivatives by employing 15 mol%β-cyclodextrinvia a one-pot multicomponent reaction of aldehyde,dimedone,hydrazine hydrate with succinic anhydride/phthalic anhydride in water at 80 ℃ for first time.The catalyst could be recovered and reused for four consecutive cycles without appreciable loss in catalytic activity and evaluated for in vitro antimicrobial activity against different Gram-positive and Gram-negative bacterial strains.The outcome of the screening study showed that compound 6d,6f and7 n exhibited excellent activity against E.coil.Whereas,compound 6f and 6h exhibited excellent activity against P.aeurginosa,and compound 6c,and 6e displayed again excellent activity against Staphylococcus aureus whereas compound 7o shows excellent activity against S.aureus and B.subtilis when compared with Ampicillin（standard control）.The results indicated that maximum compounds are moderately effective against bacterial growth and their effectiveness is highest against standard drugs.

First Magnesium-mediated Carbonyl Benzylation in Water

Catalyzed by AgNO3, Mg was found for the first time to be able to mediate the coupling reaction between aromatic aldehydes and benzyl bromide or chloride in water. The yields were slightly higher than the recent results for Mg-mediated allylation despite the fact that aqueous benzylation is intrinsically much harder than allylation. It was also found that the coupling reaction was chemoselective for aromatic aldehydes over aliphatic aldehydes, and chemoselective for aromatic aldehydes over aromatic ketones.

Growth-controlled synthesis of polymer-coated colloidal-gold nanoparticles using electrospray-based chemical reduction

In this study,the controlled nucleation and growth of gold nanoparticles(GNPs)were investigated using a self-repelled mist in a liquid chemical reaction environment.An electrospray-based chemical reduction method was conducted in the aqueous region and at room temperature to synthesize the polymeric-stabilized gold nanoparticles.The electrospray technique was used to atomize a hydrogen tetrachloraurate(III)(HAuCl4)precursor solution into electrostatically charged droplets.The atomized droplets were dispersed in an aqueous reaction bath containing L-ascorbic acid as a reducing agent and polyvinylpyrrolidone(PVP)as a stabilizer.The effect of the electrospray parameters,specifically the flow rate and electrospray droplet size,as well as the reaction conditions such as the concentration of reactants,pH,and stabilizer(PVP),were investigated.The mean diameter of the GNPs increased from around 4 to 9 nm with an increase in the electrospray flow rate,droplet size,and current passing through the electrospray jet.Spherical and monodispersed GNPs were synthesized at a relatively high flow rate of 2 mL/h and a moderate concentration of 2 mM of precursor solution.The smallest-sized GNP with a high monodispersity was obtained in the reaction bath at a high pH of 10.5 and in the presence of PVP.It is expected that continuous and mass production of the engineered GNPs and other noble metal nanoparticles could be established for scaling up nanoparticle production via the proposed electrospray-based chemical reduction method.