Table1_Influence of the Weakening Effect of Drilling Fluid on Wellbore Stability in Anisotropic Shale Formation.XLSX

For horizontal wells in Longmaxi Formation, oil-based drilling fluid that soaks for a long time is more likely to cause a wellbore collapse. Therefore, in this paper, the downhole core method of shale formation, in Longmaxi Formation, was adopted. First, rock samples were selected from different sampling angles and soaked with field drilling fluid. Second, a triaxial mechanics experiment was carried out. Based on the anisotropic wellbore stress distribution model, the stability of shale wellbore was calculated and analyzed. The results show that the compressive strength and cohesion of the shale are reduced after soaking in the drilling fluid. Hence, the reduction range of various sampling angles obviously differs as well. Shear failure occurs in vertical stratification; shear slip failure occurs along the weak plane, showing strong anisotropy. Combined with the experimental results, the collapse pressure is calculated, and it is found that the weakening effect of drilling fluid makes the overall collapse pressure rise by about 0.2 g/cm3. Finally, the shale bedding dip and dip direction have a great influence on the collapse pressure. The lower critical mud weight always takes the minimum value when the borehole axis is perpendicular to the bedding.</p

Table2_Influence of the Weakening Effect of Drilling Fluid on Wellbore Stability in Anisotropic Shale Formation.XLSX

For horizontal wells in Longmaxi Formation, oil-based drilling fluid that soaks for a long time is more likely to cause a wellbore collapse. Therefore, in this paper, the downhole core method of shale formation, in Longmaxi Formation, was adopted. First, rock samples were selected from different sampling angles and soaked with field drilling fluid. Second, a triaxial mechanics experiment was carried out. Based on the anisotropic wellbore stress distribution model, the stability of shale wellbore was calculated and analyzed. The results show that the compressive strength and cohesion of the shale are reduced after soaking in the drilling fluid. Hence, the reduction range of various sampling angles obviously differs as well. Shear failure occurs in vertical stratification; shear slip failure occurs along the weak plane, showing strong anisotropy. Combined with the experimental results, the collapse pressure is calculated, and it is found that the weakening effect of drilling fluid makes the overall collapse pressure rise by about 0.2 g/cm3. Finally, the shale bedding dip and dip direction have a great influence on the collapse pressure. The lower critical mud weight always takes the minimum value when the borehole axis is perpendicular to the bedding.</p

A Highly Efficient Coordination Polymer for Selective Trapping and Sensing of Perrhenate/Pertechnetate

A porous cationic Ag­(I) coordination polymer, [Ag­(1,2,4,5-p4b)]­(SbF6) (TJNU-302) with the ligand 1,2,4,5-p4b (1,2,4,5-tetra­(pyridin-4-yl)­benzene), is reported that shows high sorption capacity (211 mg g–1) and distribution coefficient Kd (5.8 × 105 mL g–1) as well as outstanding selectivity in 500 times excess of CO32– or PO43– anion for perrhenate removal. TJNU-302 can act as a crystalline turn-off sensor for perrhenate upon UV radiation. In this way, a test paper strip for sensing ReO4– could be produced. In water solution, TJNU-302 shows an efficient fluorescence quenching response to ReO4– ion, with the highest quenching percentage (86%) among all reported ReO4– sensors. These results could be elucidated by the bonding properties of single-crystal structures of TJNU-302 before and after perrhenate sorption, as well as density functional theory (DFT) calculations

A Highly Efficient Coordination Polymer for Selective Trapping and Sensing of Perrhenate/Pertechnetate

A porous cationic Ag­(I) coordination polymer, [Ag­(1,2,4,5-p4b)]­(SbF6) (TJNU-302) with the ligand 1,2,4,5-p4b (1,2,4,5-tetra­(pyridin-4-yl)­benzene), is reported that shows high sorption capacity (211 mg g–1) and distribution coefficient Kd (5.8 × 105 mL g–1) as well as outstanding selectivity in 500 times excess of CO32– or PO43– anion for perrhenate removal. TJNU-302 can act as a crystalline turn-off sensor for perrhenate upon UV radiation. In this way, a test paper strip for sensing ReO4– could be produced. In water solution, TJNU-302 shows an efficient fluorescence quenching response to ReO4– ion, with the highest quenching percentage (86%) among all reported ReO4– sensors. These results could be elucidated by the bonding properties of single-crystal structures of TJNU-302 before and after perrhenate sorption, as well as density functional theory (DFT) calculations

Homogeneous Fluidization of Geldart D Particles in a Gas–Solid Fluidized Bed with a Frame Impeller

The influence of agitation of a frame impeller on the fluidization performance of Geldart D particles is experimentally and numerically studied in a gas–solid stirred fluidized bed, using a three-dimensional (3D) unsteady computational fluid dynamics (CFD) simulation. The bed pressure drops obtained from simulations are in reasonable agreement with those measured with pressure transducers, which validates the CFD models. The experimental results of the pressure fluctuation and the simulated ones of the solid volume fraction distribution show that Geldart D particles can perform homogeneous fluidization in the presence of the impeller. The homogeneous fluidization regime expands as the minimum bubbling velocity increases with the agitation speed while the minimum fluidizing velocity remains unaffected. In addition, the uniformity of particle velocities that are distributed in the entire fluidized bed is also improved by the agitation of the frame impeller

Effects of the Cage Unit Size and Number of Cage Units As Well As Bridge Unit on the Second Order Nonlinear Optical Response in Multicage Electride Molecules

Interesting effects of the cage unit size and number of cage units as well as bridge unit on the static first hyperpolarizabilities (β0) for novel multicage electrides are revealed. (1) The small cage unit C8 systems have larger β0 for cage unit size effect. (2) The β0 increases with increasing cage unit number. (3) The effect of the bridge between cage units on β0 is O > NH > CH2. Specially, a novel relationship between the excess electron cloud and β0 is revealed. Assembling the three effects, the constructed multicage electride structure with three small C8 cage units connected by the O-bridge (K···3C8(O)) is a electride salt K+[e@3C8(O)]– and has the considerable β0 value of 7.1 × 105 au, which is about 55 times larger than the 13 000 au of the single-cage electride molecule Na3O+(e@C20F20)−. The novel multicage strategy is effective to enhance nonlinear optical (NLO) response

Unusual Manipulative Effects of Spin Multiplicity and Excess Electron Number on the Structure and Nonlinear Optical Response in New Linear and Cyclic Electride Molecules with Multiexcess Electrons

Using the M06-2X density functional theory, unusual manipulative effects of spin multiplicity and excess electron number on the structure and static first hyperpolarizability (β₀) are revealed for new electride molecules with multiexcess electrons. (1) For the spin effect on molecular structure, the low spin multiplicity brings bent structures (^<b>1</b><b>L</b>_<b>2</b> and ^<b>2</b><b>L</b>_<b>3</b>) for linear isomers. (2) For the dramatic effect of spin multiplicity on β₀, the considerable β₀ of 22.7 × 10⁴ au for the low spin structure ^<b>2</b><b>L</b>_<b>3</b> is larger by 21 times than that of 1.1 × 10⁴ au for the high spin structure ^<b>4</b><b>L</b>_<b>3</b> due to one excess electron spin reversal. The low spin structure with doubly and singly occupied frontier orbitals is relevant to the low transition energy and complex distribution of electron density, which dramatically enhances β₀. (3) For the effect of excess electron number on β₀, the β₀ value increases rapidly with increasing excess electron number. A long chain-shaped electride molecule (for instance, ^<b>2</b><b>L</b>_<b>3</b>) with multiexcess electrons in low spin state may bring a considerable static first hyperpolarizability, which is a novel manipulation strategy of enhancing molecular NLO response

New Acceptor–Bridge–Donor Strategy for Enhancing NLO Response with Long-Range Excess Electron Transfer from the NH₂...M/M₃O Donor (M = Li, Na, K) to Inside the Electron Hole Cage C₂₀F₁₉ Acceptor through the Unusual σ Chain Bridge (CH₂)₄

Using the strong electron hole cage C20F19 acceptor, the NH2...M/M3O (M = Li, Na, and K) complicated donors with excess electron, and the unusual σ chain (CH2)4 bridge, we construct a new kind of electride molecular salt e–@C20F19–(CH2)4–NH2...M+/M3O+ (M = Li, Na, and K) with excess electron anion inside the hole cage (to be encapsulated excess electron–hole pair) serving as a new A–B–D strategy for enhancing nonlinear optical (NLO) response. An interesting push–pull mechanism of excess electron generation and its long-range transfer is exhibited. The excess electron is pushed out from the (super)­alkali atom M/M3O by the lone pair of NH2 in the donor and further pulled inside the hole cage C20F19 acceptor through the efficient long σ chain (CH2)4 bridge. Owing to the long-range electron transfer, the new designed electride molecular salts with the excess electron–hole pair exhibit large NLO response. For the e–@C20F19–(CH2)4–NH2...Na+, its large first hyperpolarizability (β0) reaches up to 9.5 × 106 au, which is about 2.4 × 104 times the 400 au for the relative e–@C20F20...Na+ without the extended chain (CH2)4–NH2. It is shown that the new strategy is considerably efficient in enhancing the NLO response for the salts. In addition, the effects of different bridges and alkali atomic number on β0 are also exhibited. Further, three modulating factors are found for enhancing NLO response. They are the σ chain bridge, bridge-end group with lone pair, and (super)­alkali atom. The new knowledge may be significant for designing new NLO materials and electronic devices with electrons inside the cages. They may also be the basis of establishing potential organic chemistry with electron–hole pair

Amphiphilic Polyurethane with Cluster-Induced Emission for Multichannel Bioimaging in Living Cell Systems

The development of single-component materials with low cytotoxicity and multichannel fluorescence imaging capability is a research hotspot. In the present work, highly electron-deficient pyrazine monomers were covalently connected into a polyurethane backbone using addition polymerization with terminal poly(ethylene glycol) monomethyl ether units containing a high density of electron pairs. Thereby, an amphiphilic polyurethane-pyrazine (PUP) derivative has been synthesized. The polymer displays cluster-induced emission through compact inter- and/or intramolecular noncovalent interactions and extensive through-space electron coupling and delocalization. Molecular rigidity facilitates red-shifted emission. Based on hydrophilic/hydrophobic interactions and excitation dependence emission at low concentrations, PUP has been self-assembled into fluorescent nanoparticles (PUP NPs) without additional surfactant. PUP NPs have been used for cellular multicolor imaging to provide a variety of switchable colors on demand. This work provides a simple molecular design for environmentally sustainable, luminescent materials with excellent photophysical properties, biocompatibility, low cytotoxicity, and color modulation

An External Electric Field Manipulated Second-Order Nonlinear Optical Switch of an Electride Molecule: A Long-Range Electron Transfer Forms a Lone Excess Electron Pair and Quenches Singlet Diradical

An electride molecule e^–···K­(1)⁺···calix­[4]­pyrrole···K­(2)⁺···e^– as an external electric field (<i>F</i>) manipulated nonlinear optical (NLO) switch is designed theoretically for the first time. As this molecule is an unusual singlet diradical electride molecule with two easily driven excess electrons (by electric field) at two opposite ends of the molecule, a novel switching mechanism of electronic structure isomerization emerges as a distinctive nonbonding evolution in the electride molecule. A small electric field driving leads to a long-range excess electron transfer from one side K(1) through the middle calix[4]­pyrrole to the other side K(2), forms a lone excess electron pair of <i>s</i>-type rather than a single bond, and quenches the singlet diradical. Meanwhile, the molecular electronic structure becomes K(1)⁺···calix­[4]­pyrrole···K­(2)⁺···2e^–. Therefore, the small electric field driving brings a very high static first hyperpolarizability (β₀) contrast from 0 (<i>F</i> = 0, Off form) to 4.060 × 10⁵ au (<i>F</i> = a small nonzero value of 5 × 10^–4 au, On form). Notably, under the electric field of 30 × 10^–4 au, β₀ reaches the largest value of 3.147 × 10⁶ au and the molecule displays the most optimal NLO switching behavior. Furthermore, we consider also that 4H atoms of calix[4]­pyrrole are substituted with 4F and 2Be atoms, respectively; then the 2Be and 4F substitution effects on the NLO switch in electride molecules are exhibited. This work opens a new research field of an electric field manipulated NLO switch of electride molecules