Effect of Temperature on Asphaltene Precipitation in Crude Oils from Xinjiang Oilfield

During the production of crude oil, asphaltenes are prone to precipitate due to the changes of external conditions (temperature, pressure, etc.). Therefore, a series of research studies were designed to investigate the effect of temperature on asphaltene precipitation for two Xinjiang crude oils (S1, S2) so as to reveal the mechanism of asphaltene dissolution. First, the changes of asphaltene precipitation were intuitively observed by using a microscope. The results demonstrated that the asphaltene solubility increased with the increase of temperature and the dispersion rate of asphaltene particles increased with the decrease of particle size. Second, the variation of asphaltene precipitation with temperature was quantified by a gravimetric method. The results suggested that the different asphaltenes showed different sensitivity to temperature within the temperature range 25–120 °C. Third, a hypothesis was proposed to explain these results and proved that the asphaltene aggregate structure was an important factor for asphaltene stability. The crystallite parameters of asphaltenes were obtained by X-ray diffraction (XRD) to describe the structural characteristics. The results revealed that the layer distance between aromatic sheets (dm) of asphaltenes derived from S1 oil and S2 oil were 0.378 and 0.408 nm, respectively, which implied that the asphaltene aggregates derived from S2 oil were looser than those of S1 oil. Therefore, high temperature could facilitate the penetration of resins into asphaltene aggregates and ultimately improve the dispersion of asphaltenes. Finally, molecular dynamics (MD) simulation was used to verify the conclusions. Based on the molecular dynamics method, asphaltene aggregate models were developed. The compactness and internal energy of each model were calculated. The results showed that the asphaltene dispersion capability was proportional to the porosity and internal energy

A new isophorone-based ligand and its Ag(I) complex: crystal structures and luminescence

<div><p>An isophorone-based ligand with a delocalized π-electron system, 2-{5,5-dimethyl-3-[2-(pyridine-4-yl)ethenyl]cyclohex-2-enylidene}propanedinitrile (<b>L</b>), was synthesized. By assembling the ligand with AgNO₃, a mononuclear complex [Ag(L)₂]NO₃·H₂O was obtained. Compared with the free ligand, the complex shows superior luminescent properties with large red-shift and longer fluorescence lifetime.</p></div

KO^<i>t</i>Bu-Mediated Coupling of Indoles and [60]Fullerene: Transition‑Metal-Free and General Synthesis of 1,2-(3-Indole)(hydro)[60]fullerenes

Direct coupling of indoles with C₆₀ has been achieved for the first time. Transition-metal-free KO^<i>t</i>Bu-mediated reaction of indoles to [60]­fullerene has been developed as a practical and efficient method for the synthesis of various 1,2-(3-indole)­(hydro)[60]­fullerenes that are otherwise difficult to direct synthesize in an efficient and selective manner. This methodology tolerates sensitive functionalities such as chloro, ester, and nitro on indole and builds molecular complexity rapidly, with most reactions reaching completion in <1 h. A plausible reaction mechanism is proposed to explain the high regioselectivity at the 3-position of the indoles and the formation of 1,2-(3-indole)­(hydro)[60]­fullerenes

Uniting Ruthenium(II) and Platinum(II) Polypyridine Centers in Heteropolymetallic Complexes Giving Strong Two-Photon Absorption

New trinuclear RuPt₂ and heptanuclear RuPt₆ complex salts are prepared by attaching Pt^II 2,2′:6′,2″-terpyridine (tpy) moieties to Ru^II 4,4′:2′,2″:4″,4‴-quaterpyridine (qpy) complexes. Characterization includes single crystal X-ray structures for both polymetallic species. The visible absorption bands are primarily due to Ru^II → qpy metal-to-ligand charge-transfer (MLCT) transitions, according to time-dependent density functional theory (TD-DFT) calculations. These spectra change only slightly on Pt coordination, while the orange-red emission from the complexes shows corresponding small red-shifts, accompanied by decreases in intensity. Cubic molecular nonlinear optical behavior has been assessed by using Z-scan measurements. These reveal relatively high two-photon absorption (2PA) cross sections σ₂, with maximal values of 301 GM at 834 nm (RuPt₂) and 523 GM at 850 nm (RuPt₆) when dissolved in methanol or acetone, respectively. Attaching Pt^II(tpy) moieties triples or quadruples the 2PA activities when compared with the Ru^II-based cores

Substituent Group Variations Directing the Molecular Packing, Electronic Structure, and Aggregation-Induced Emission Property of Isophorone Derivatives

A series of new isophorone derivatives (<b>1</b>–<b>5</b>), incorporating the heterocyclic ring or aza-crown-ether group, with large Stokes shifts (>140 nm), have been synthesized and characterized. <b>1</b>–<b>4</b> display aggregation-induced emission behaviors, while dye <b>5</b> is highly emissive in solution but quenched in the solid state. It was found that the tuning of emission color of the isophorone-based compounds in the solid state could be conveniently accomplished by changing the terminal substituent group. The photophysical properties in solution, aqueous suspension, and crystalline state, along with their relationships, are comparatively investigated. Crystallographic data of <b>1</b>–<b>4</b> indicate that the existence of multiple intermolecular hydrogen bonding interactions between the adjacent molecules restricts the intramolecular vibration and rotation and enables compounds <b>1</b>–<b>4</b> to emit intensely in the solid state. The size and growth processes of particles with different water fractions were studied using a scanning electron microscope, indicating that smaller globular nanoparticles in aqueous suspension are in favor of fluorescence emissions. The above results suggest that substituent groups have a great influence on their molecular packing, electronic structure, and aggregation-induced emission properties. In addition, fluorescence cell imaging experiment proved the potential application of <b>5</b>

Substituent Group Variations Directing the Molecular Packing, Electronic Structure, and Aggregation-Induced Emission Property of Isophorone Derivatives

A series of new isophorone derivatives (<b>1</b>–<b>5</b>), incorporating the heterocyclic ring or aza-crown-ether group, with large Stokes shifts (>140 nm), have been synthesized and characterized. <b>1</b>–<b>4</b> display aggregation-induced emission behaviors, while dye <b>5</b> is highly emissive in solution but quenched in the solid state. It was found that the tuning of emission color of the isophorone-based compounds in the solid state could be conveniently accomplished by changing the terminal substituent group. The photophysical properties in solution, aqueous suspension, and crystalline state, along with their relationships, are comparatively investigated. Crystallographic data of <b>1</b>–<b>4</b> indicate that the existence of multiple intermolecular hydrogen bonding interactions between the adjacent molecules restricts the intramolecular vibration and rotation and enables compounds <b>1</b>–<b>4</b> to emit intensely in the solid state. The size and growth processes of particles with different water fractions were studied using a scanning electron microscope, indicating that smaller globular nanoparticles in aqueous suspension are in favor of fluorescence emissions. The above results suggest that substituent groups have a great influence on their molecular packing, electronic structure, and aggregation-induced emission properties. In addition, fluorescence cell imaging experiment proved the potential application of <b>5</b>

Systematic Study and Imaging Application of Aggregation-Induced Emission of Ester-Isophorone Derivatives

The dicyanoisophorone derivatives show obvious AIE behaviors in our previous work. To study the bioimaging application of these chromophores with AIE/AIEE properties, the ester groups substituted for one cyan to form a new family based on isophorone (<b>2a</b>–<b>2e</b>). <b>2a</b>–<b>2d</b> exhibit obvious AIE/AIEE phenomena, while <b>2e</b> shows fluorescence quenching in the aggregate state. The morphology and size of aggregates with different water contents were investigated using SEM and DLS, indicating that a large number of smaller globular or quadrate nanoparticles with average diameters in the range 78.79–392.7 nm in mixed solutions are related to these AIE/AIEE or ACQ behaviors. We also made comparative analyses of their optical properties in different states. The crystal data of <b>2a</b>–<b>2d</b> reveal that the multiple intra- and intermolecular interactions leads to the molecular conformation being more stable, increases the planarity of compounds, restricts the intramolecular motions, and promotes the formation of <i>J</i>-type aggregate, enabling chromophores <b>2a</b>–<b>2d</b> to emit intensely in the solid state. In addition, the frontier molecular orbital energy and band gap calculated by density functional theory are quite consistent with the experimental results. Finally, these AIE/AIEE-active compounds could be used in bioimaging applications, which immensely provide a new strategy to the application of some AIE/AIEE systems

Substituent Group Variations Directing the Molecular Packing, Electronic Structure, and Aggregation-Induced Emission Property of Isophorone Derivatives

A series of new isophorone derivatives (<b>1</b>–<b>5</b>), incorporating the heterocyclic ring or aza-crown-ether group, with large Stokes shifts (>140 nm), have been synthesized and characterized. <b>1</b>–<b>4</b> display aggregation-induced emission behaviors, while dye <b>5</b> is highly emissive in solution but quenched in the solid state. It was found that the tuning of emission color of the isophorone-based compounds in the solid state could be conveniently accomplished by changing the terminal substituent group. The photophysical properties in solution, aqueous suspension, and crystalline state, along with their relationships, are comparatively investigated. Crystallographic data of <b>1</b>–<b>4</b> indicate that the existence of multiple intermolecular hydrogen bonding interactions between the adjacent molecules restricts the intramolecular vibration and rotation and enables compounds <b>1</b>–<b>4</b> to emit intensely in the solid state. The size and growth processes of particles with different water fractions were studied using a scanning electron microscope, indicating that smaller globular nanoparticles in aqueous suspension are in favor of fluorescence emissions. The above results suggest that substituent groups have a great influence on their molecular packing, electronic structure, and aggregation-induced emission properties. In addition, fluorescence cell imaging experiment proved the potential application of <b>5</b>

Substituent Group Variations Directing the Molecular Packing, Electronic Structure, and Aggregation-Induced Emission Property of Isophorone Derivatives

A series of new isophorone derivatives (<b>1</b>–<b>5</b>), incorporating the heterocyclic ring or aza-crown-ether group, with large Stokes shifts (>140 nm), have been synthesized and characterized. <b>1</b>–<b>4</b> display aggregation-induced emission behaviors, while dye <b>5</b> is highly emissive in solution but quenched in the solid state. It was found that the tuning of emission color of the isophorone-based compounds in the solid state could be conveniently accomplished by changing the terminal substituent group. The photophysical properties in solution, aqueous suspension, and crystalline state, along with their relationships, are comparatively investigated. Crystallographic data of <b>1</b>–<b>4</b> indicate that the existence of multiple intermolecular hydrogen bonding interactions between the adjacent molecules restricts the intramolecular vibration and rotation and enables compounds <b>1</b>–<b>4</b> to emit intensely in the solid state. The size and growth processes of particles with different water fractions were studied using a scanning electron microscope, indicating that smaller globular nanoparticles in aqueous suspension are in favor of fluorescence emissions. The above results suggest that substituent groups have a great influence on their molecular packing, electronic structure, and aggregation-induced emission properties. In addition, fluorescence cell imaging experiment proved the potential application of <b>5</b>

Boosting Hot-Electron Generation: Exciton Dissociation at the Order–Disorder Interfaces in Polymeric Photocatalysts

Excitonic effects, arising from the Coulomb interactions between photogenerated electrons and holes, dominate the optical excitation properties of semiconductors, whereas their influences on photocatalytic processes have seldom been discussed. In view of the competitive generation of excitons and hot carriers, exciton dissociation is proposed as an alternative strategy for hot-carrier harvesting in photocatalysts. Herein, by taking heptazine-based melon as an example, we verified that enhanced hot-carrier generation could be obtained in semicrystalline polymeric photocatalysts, which is ascribed to the accelerated exciton dissociation at the abundant order−disorder interfaces. Moreover, driven by the accompanying electron injection toward ordered chains and hole blocking in disordered chains, semicrystalline heptazine-based melon showed an ∼7-fold promotion in electron concentration with respect to its pristine counterpart. Benefiting from these, the semicrystalline sample exhibited dramatic enhancements in electron-involved photocatalytic processes, such as superoxide radical production and selective alcohol oxidation. This work brightens excitonic aspects for the design of advanced photocatalysts