Ling He

Aqueous-phase selective hydrogenation of phenol to cyclohexanone over soluble Pd nanoparticles

The water-soluble metal nanoparticles (NPs) stabilized by poly(N-vinyl-2-pyrrolidone) (PVP) were prepared and examined as catalysts for the one-step selective hydrogenation of phenol to cyclohexanone in water. More than 99% conversion of phenol and selectivity to cyclohexanone was obtained at 90 °C and 1 atm H2 for 16 h over “soluble” Pd NPs that were reduced by NaBH4 and stabilized by PVP. These Pd NPs were stable, and no leaching or aggregation was detected after five successive runs, showing their advantage for catalyzing the efficient synthesis of cyclohexanone via the one-step selective hydrogenation of phenol under mild conditions.

High yield of ethyl valerate from the esterification of renewable valeric acid catalyzed by amino acid ionic liquids

Ethyl valerate (EV) as a promising fuel additive was produced by esterification of valeric acid with ethanol over Bronsted acidic amino acid ionic liquids. Hammett method and density functional theory (DFT) calculations were preformed to evaluate the acidities of the catalysts. The composition of catalyst, reaction temperature, reaction time, molar ratio of reactants, amount of catalyst, and recycling ability of the catalyst were investigated. Proline bisulfate (ProHSO4) ionic liquid has the highest catalytic activity and the best recyclability under the optimized esterification conditions. A high conversion of valeric acid (>99.9%) was obtained for 7 h at 80 °C, with 100% selectivity of EV. The density, viscosity, melting point, boiling point, elemental analysis and heat of combustion of the EV product were measured. The density of EV is 0.896 g cm−3. The viscosity of EV was 1.7 cP at room temperature. The heating values of EV are 4158.1 kJ mol−1 and 31.9 kJ g−1. EV obtained from esterification has higher energy density than methanol, ethanol, γ-valerolactone, and valeric acid, which illustrates that EV is a promising biofuel candidate.

Experimental and Theoretical Enthalpies of Formation of Glycine-Based Sulfate/Bisulfate Amino Acid Ionic Liquids

The experimental and theoretical enthalpies of formation of several structural-similar glycine-based sulfate/bisulfate amino acid ionic liquids including glycine sulfate (Gly(2)SO(4), 1), glycine bisulfate (GlyHSO(4), 2), N,N-dimethylglycine sulfate ([DMGly](2)SO(4), 3), N,N-dimethylglycine bisulfate ([DMGly]HSO(4), 4), N,N-dimethylglycine methyl ester sulfate ([DMGlyC(1)](2)SO(4), 5), N,N-dimethylglycine methyl ester bisulfate ([DMGlyC(1)]HSO(4), 6), N,N,N-trimethylglycine methyl ester sulfate ([TMGlyC(1)](2)SO(4), 7), and N,N,N-trimethylglycine methyl ester bisulfate ([TMGlyC(1)]HSO(4), 8) were studied. Their experimental enthalpies of formation were obtained from the corresponding energies of combustion determined by the bomb calorimetry method. The enthalpies of formation of these amino acid ionic liquids are in the range from -1406 kJ mol(-1) to -1128 kJ mol(-1). Systematic theoretical study on these amino acid ionic liquids were performed by quantum chemistry calculation using the Gaussian03 suite of programs. The geometric optimization and the frequency analyses are carried out using the B3LYP method with the 6-31+G** basis set. Their calculated enthalpies of formation were derived from the single point energies carried out with the HF/6-31+G**, B3LYP/6-31+G**, B3LYP/6-311++G**, and MP2/6-311++G** level of theory, respectively. The relevance of experimental and calculated enthalpies of formation was studied. The calculated enthalpies of formation are in good agreement with their experimental data in less than 3% error.

Brønsted acidity of bio-protic ionic liquids: the acidic scale of [AA]X amino acid ionic liquids

Amino acid ionic liquids (AAILs) [AA]X based on amino acid cations are a kind of typical “bio-base” protic ionic liquids (PILs), which are supposed to be acidic ionic liquids. The Bronsted acidity of [AA]X PILs at room temperature was systematically studied for the first time. Acid dissociation constants (pKa) of [AA]X were determined by the potentiometric titration method. The first acid dissociation constants (pKa1) are from 1.98 to 2.42. The actual pH values of [AA]X (0.010 mol L−1) obtained from a pH meter are from 2.26 to 2.44 which are slightly higher than the calculated pH values according to the above experimental pKa1. The Hammett method performed on UV/Vis spectra with p-nitroaniline as the indicator was used to determine the acidic strength of [AA]X. Their H0 values (0.010 mol L−1) are in the range from 2.10 to 2.44. Various frameworks of amino acid cations and five anions (including nitrate (NO3−), chloride (Cl−), perchlorate (ClO4−), trifluoromethanesulfonate (OTf−) and trifluoroacetate (TfA−) anions) were used to investigate the cationic and anionic effect on the acidity of AAILs. The Bronsted acidity of AAILs depends on the cationic structure, the type of anion and the concentration of [AA]X. In addition, the theoretical pKa1 values were studied by using the cluster-continuum model using the density functional theory (DFT) method. The experimental and theoretical results showed that [AA]X PILs have a stronger Bronsted acidity than the common PILs prepared by one-pot syntheses.

Electrochemical and thermodynamic properties of Ln(III) (Ln = Eu, Sm, Dy, Nd) in 1-butyl-3-methylimidazolium bromide ionic liquid.

The electrochemical behavior and thermodynamic properties of Ln(III) (Ln = Eu, Sm, Dy, Nd) were studied in 1-butyl-3-methylimidazolium bromide ionic liquid (BmimBr) at a glassy carbon (GC) electrode in the range of 293–338 K. The electrode reaction of Eu(III) was found to be quasi-reversible by the cyclic voltammetry, the reactions of the other three lanthanide ions were regarded as irreversible systems. An increase of the current intensity was obtained with the temperature increase. At 293 K, the cathodic peak potentials of −0.893 V (Eu(III)), −0.596 V (Sm(III)), −0.637 V (Dy(III)) and −0.641 V (Nd(III)) were found, respectively, to be assigned to the reduction of Ln(III) to Ln(II). The diffusion coefficients (D o), the transfer coefficients (α) of Ln(III) (Ln = Eu, Sm, Dy, Nd) and the charge transfer rate constants (k s) of Eu(III) were estimated. The apparent standard potential (E 0*) and the thermodynamic properties of the reduction of Eu(III) to Eu(II) were also investigated.

Discriminative Analysis of Migraine without Aura: Using Functional and Structural MRI with a Multi-Feature Classification Approach.

Magnetic resonance imaging (MRI) is by nature a multi-modality technique that provides complementary information about different aspects of diseases. So far no attempts have been reported to assess the potential of multi-modal MRI in discriminating individuals with and without migraine, so in this study, we proposed a classification approach to examine whether or not the integration of multiple MRI features could improve the classification performance between migraine patients without aura (MWoA) and healthy controls. Twenty-one MWoA patients and 28 healthy controls participated in this study. Resting-state functional MRI data was acquired to derive three functional measures: the amplitude of low-frequency fluctuations, regional homogeneity and regional functional correlation strength; and structural MRI data was obtained to measure the regional gray matter volume. For each measure, the values of 116 pre-defined regions of interest were extracted as classification features. Features were first selected and combined by a multi-kernel strategy; then a support vector machine classifier was trained to distinguish the subjects at individual level. The performance of the classifier was evaluated using a leave-one-out cross-validation method, and the final classification accuracy obtained was 83.67% (with a sensitivity of 92.86% and a specificity of 71.43%). The anterior cingulate cortex, prefrontal cortex, orbitofrontal cortex and the insula contributed the most discriminative features. In general, our proposed framework shows a promising classification capability for MWoA by integrating information from multiple MRI features.

Insensitive energetic 5-nitroaminotetrazolate ionic liquids

Five energetic ionic liquids of 5-nitroaminotetrazolate anion (NAT) combined with 1,3-dimethylimidazolium (1), 1-ethyl-3-methylimidazolium (2), 1-butyl-3-methylimidazolium (3), 1-hexyl-3-methylimidazolium (4), and 1-methyl-3-octylimidazolium (5) cations were synthesized in high yields and fully characterized by IR, NMR and elemental analysis. Colorless block crystals of 1 were isolated in methanol/ethanol and crystallized in the orthorhombic system Fdd2(43) (a = 49.337(3) A, b = 20.9073(12) A, c = 3.6993(2) A, V = 3815.84(38) A3, Z = 16). The ionic liquids 1–5 are thermally stable at temperatures higher than 200 °C. Among them, 2–5 are found to be room temperature ionic liquids. The heats of formation of 1–5 obtained by both experimental and theoretical methods are all positive. 1 possesses the highest value of 194.6 kJ mol−1 and 0.86 kJ g−1. These novel NAT energetic ionic liquids contain only C, H, N and O elements. The CHNO type ionic liquids 1–5 are insensitive towards impact (>40 J) and friction (>360 N). They showed good combustion characteristics after being ignited by a flame. They are of interest as liquid energetic materials with modestly high energy, high thermal stability, and good insensitivity to impact and friction, as well as environmentally friendly decomposition gases.

Multimodal MRI-Based Classification of Trauma Survivors with and without Post-Traumatic Stress Disorder.

Post-traumatic stress disorder (PTSD) is a debilitating psychiatric disorder. It can be difficult to discern the symptoms of PTSD and obtain an accurate diagnosis. Different magnetic resonance imaging (MRI) modalities focus on different aspects, which may provide complementary information for PTSD discrimination. However, none of the published studies assessed the diagnostic potential of multimodal MRI in identifying individuals with and without PTSD. In the current study, we investigated whether the complementary information conveyed by multimodal MRI scans could be combined to improve PTSD classification performance. Structural and resting-state functional MRI (rs-fMRI) scans were conducted on 17 PTSD patients, 20 trauma-exposed controls without PTSD (TEC) and 20 non-traumatized healthy controls (HC). Gray matter volume (GMV), amplitude of low-frequency fluctuations (ALFF), and regional homogeneity were extracted as classification features, and in order to integrate the information of structural and functional MRI data, the extracted features were combined by a multi-kernel combination strategy. Then a support vector machine (SVM) classifier was trained to distinguish the subjects at individual level. The performance of the classifier was evaluated using the leave-one-out cross-validation (LOOCV) method. In the pairwise comparison of PTSD, TEC, and HC groups, classification accuracies obtained by the proposed approach were 2.70, 2.50, and 2.71% higher than the best single feature way, with the accuracies of 89.19, 90.00, and 67.57% for PTSD vs. HC, TEC vs. HC, and PTSD vs. TEC respectively. The proposed approach could improve PTSD identification at individual level. Additionally, it provides preliminary support to develop the multimodal MRI method as a clinical diagnostic aid.

Tunable luminescence of lanthanide (Ln = Sm, Eu, Tb) hydrophilic ionic polymers based on poly(N-methyl-4-vinylpyridinium-co-styrene) cations

Hydrophilic luminescent lanthanide polymers poly-[MVPS]2[Ln(NO3)5] (Ln = Sm (P1), Eu (P2), Tb (P3)) were designed and characterized. Benefiting from the methylation process of poly(4-vinylpyridinium-co-styrene) (PVPS), we switch the hydrophobicity of PVPS and further functionalize it by incorporating lanthanide luminophores into the chelate anion part to construct stable ionic polymer networks (P1–P3) by means of the anion–cation cooperative Coulombic interactions. These lanthanide polymers exhibit characteristic yellow, red and green emissions respectively which originate from the lanthanides Sm3+, Eu3+ and Tb3+. Furthermore, the chromatic colours of poly-[MVPS]2[Tb(NO3)5]/poly-[MVPS]2[Eu(NO3)5] (P3/P2) are readily modulated over a wide spectral emission from red over yellow to green. The energy transfer mechanism from the donor Tb3+ to the acceptor Eu3+ in the mixtures is further demonstrated. Interestingly, the straightforward reversible colorimetric water-responsive properties presented here offer a rapid approach to the broad-spectral colour tuning of water sensor materials. Therefore, these lanthanide-containing ionic polymers can be predicted to be utilized as promising candidates of reversible colorimetric components in the fabrication of UV-pumped sensors for water.

Insensitive ionic bio-energetic materials derived from amino acids

Energetic salts/ionic liquids have received increasing attention as fascinating energetic materials, and the use of renewable compounds is a promising approach to developing energetic materials. Until recently, biomolecules have been used as raw materials to develop neutral energetic compounds, whereas research focused on ionic energetic materials obtained from natural bio-renewable frameworks is scarce. This work systematically investigates ionic bio-energetic materials (IBEMs) derived from sustainable natural amino acids. In addition to combustibility, high density, good thermal stability, and one-step preparation, these IBEMs demonstrated apparent hypotoxicity and insensitivity. Moreover, a theoretical examination was performed to explore their appropriate properties. The intriguing results of this study indicates that IBEMs are potential bio-based energetic materials.