高中化学必修课程“变化观念与平衡思想”学科核心素养的系统构成研究

“变化观念与平衡思想”学科核心素养的系统构成对开展“素养导向”的教学与评价具有重要意义。通过课标分析,基于学科能力模型明确了高中必修学段“变化观念与平衡思想”核心素养的核心知识与活动经验、认识方式、研究对象及问题情境、学科能力活动及其表现等4个维度的具体内涵,系统建构了高中化学必修课程“变化观念与平衡思想”学科核心素养模型。     

Simultaneous detection of resolved glutamate, glutamine, and gamma-aminobutyric acid at 4 T

A new approach is introduced to simultaneously detect resolved glutamate (Glu), glutamine (Gln), and gamma-aminobutyric acid (GABA) using a standard STEAM localization pulse sequence with the optimized sequence timing parameters. This approach exploits the dependence of the STEAM spectra of the strongly coupled spin systems of Glu, Gln, and GABA on the echo time TE and the mixing time TM at 4 T to find an optimized sequence parameter set, i.e., {TE, TM}, where the outer-wings of the Glu C4 multiplet resonances around 2.35 ppm, the Gln C4 multiplet resonances around 2.45 ppm, and the GABA C2 multiplet resonance around 2.28 ppm are significantly suppressed and the three resonances become virtual singlets simultaneously and thus resolved. Spectral simulation and optimization were conducted to find the optimized sequence parameters, and phantom and in vivo experiments (on normal human brains, one patient with traumatic brain injury, and one patient with brain tumor) were carried out for verification. The results have demonstrated that the Gln, Glu, and GABA signals at 2.2-2.5 ppm can be well resolved using a standard STEAM sequence with the optimized sequence timing parameters around {82 ms,48 ms} at 4 T, while the other main metabolites, such as N-acetyl aspartate (NAA), choline (tCho), and creatine (tCr), are still preserved in the same spectrum. The technique can be easily implemented and should prove to be a useful tool for the basic and clinical studies associated with metabolism of Glu, Gln, and/or GABA.     

Probing the electronic structure of ZnO nanowires by valence electron energy loss spectroscopy

Valence electron energy loss spectroscopy in a transmission electron microscope is employed to investigate the electronic structure of ZnO nanowires with diameter ranging from 20 to 100 nm. Its excellent spatial resolution enables this technique to explore the electronic states of a single nanowire. We found that all of the basic electronic structure characteristics of the ZnO nanowires, including the 3.3 eV band gap, the single electron interband transitions at approximately = 9.5, approximately = 13.5,and approximately = 21.8 eV, and the bulk plasmon oscillation at approximately 18.8 eV, resemble those of the bulk ZnO. Momentum transfer resolved energy loss spectra suggest that the 13.5 eV excitation is actually consisted of two weak excitations at approximately = 12.8 and approximately = 14.8 eV, which originate from transitions of two groups of the Zn 3d electrons to the empty density of states in the conduction band, with a dipole-forbidden nature. The energy loss spectra taken from single nanowires of different diameters show several size-dependent features, including an increase in the oscillator strength of the surface plasmon resonance at approximately = 11.5 eV, a broadening of the bulk plasmon peak, and splitting of the O 2s transition at approximately = 21.8 eV into two peaks, which coincides with a redshift of the bulk plasmon peak, when the nanowire diameter decreases. All these observations can be well explained by the increased surface/volume ratio in nanowires of small diameter.     

An interlocked coordination cage based on aromatic amide ligands

An interlocked M_4 L_8 coordination cage was synthesized by coordination-driven self-assembly of palladium(Ⅱ) ions with aromatic amide bidentate ligands.The reaction of the ligand and the metal at 2:1 ratio led to the monomeric M_2 L_4 cage as the kinetic product,while the thermodynamic product M_4 L_8 cage was obtained by prolongating the reaction.This conve rsion and the interlocked structure was clearly revealed by using ~1 H NMR,mass spectrometry and X-ray crystallography.The driving force of interlocking was mainly attributed to the interactions(hydrogen bonding,aromatic stacking and electrostatic interaction) arising from the aptitude of flexibility of the amide ligand.     

Quantum communication for satellite-to-ground networks with partially entangled states

To realize practical wide-area quantum communication,a satellite-to-ground network with partially entangled states is developed in this paper.For efficiency and security reasons,the existing method of quantum communication in distributed wireless quantum networks with partially entangled states cannot be applied directly to the proposed quantum network.Based on this point,an efficient and secure quantum communication scheme with partially entangled states is presented.In our scheme,the source node performs teleportation only after an end-to-end entangled state has been established by entanglement swapping with partially entangled states.Thus,the security of quantum communication is guaranteed.The destination node recovers the transmitted quantum bit with the help of an auxiliary quantum bit and specially defined unitary matrices.Detailed calculations and simulation analyses show that the probability of successfully transferring a quantum bit in the presented scheme is high.In addition,the auxiliary quantum bit provides a heralded mechanism for successful communication.Based on the critical components that are presented in this article an efficient,secure,and practical wide-area quantum communication can be achieved.     

A Chiral Gold Nanocluster Au20 Protected by Tetradentate Phosphine Ligands

The chirality of a gold nanocluster can be generated from either an intrinsically chiral inorganic core or an achiral inorganic core in a chiral environment. The first structural determination of a gold nanocluster containing an intrinsic chiral inorganic core is reported. The chiral gold nanocluster [Au₂₀(PP₃)₄]Cl₄ (PP₃=tris(2‐(diphenylphosphino)ethyl)phosphine) has been prepared by the reduction of a gold(I)–tetraphosphine precursor in dichloromethane solution. Single‐crystal structural determination reveals that the cluster molecular structure has C₃ symmetry. It consists of a Au₂₀ core consolidated by four peripheral tetraphosphines. The Au₂₀ core can be viewed as the combination of an icosahedral Au₁₃ and a helical Y‐shaped Au₇ motif. The identity of this Au₂₀ cluster is confirmed by ESI‐MS. The chelation of multidentate phosphines enhances the stability of this Au₂₀ cluster.     

Restraint of stress in fabricating the large areas of crack-free porous silica films in the presence of composite polydimethylsiloxane

To present a new method of fabricating the large areas of crack-free porous silica films by introduction of composite polydimethylsiloxanes (PDMS). We employed two kinds of side-chain polyether modified by PDMS terminated with Si–CH₃ and Si–OC₂H₅ groups in preparation of large areas of porous silica films. The porous film presents a mesopore structure with a porosity of 58.0 %, which is fit for thermal-isolating layer applied in pyroelectric devices. The stress evolution on gel-to-ceramic film conversion has been investigated. The results reveal that a slow decrease in tensile stress before 250 °C and a slow increase after 250 °C can be observed, which is closely related to the alteration of chemical composition in the heat-treatment process. It is clear that the stress has been restrained with the addition of composite PDMS.     

Clickable Periodic Mesoporous Organosilicas: Synthesis,Click Reactions,and Adsorption of Antibiotics

Pharmaceutical antibiotics are not easily removed from water by conventional water‐treatment technologies and have been recognized as new emerging pollutants. Herein, we report the synthesis of clickable azido periodic mesoporous organosilicas (PMOs) and their use as adsorbents for the adsorption of antibiotics. Ethane‐bridged PMOs, functionalized with azido groups at different densities, were synthesized by the co‐condensation of 1,2‐bis(trimethoxysilyl)ethane (BTME) and 3‐azidopropyltrimethoxysilane (AzPTMS), in the presence of nonionic‐surfactant triblock‐copolymer P123, in an acidic medium. Four different alkynes were conjugated to azide‐terminated PMOs by means of an efficient click reaction. The clicked PMOs showed improved adsorption capacity (241 μg g^?1) for antibiotics (ciprofloxacin hydrochloride) compared with azido‐functionalized PMOs because of the enhanced π–π stacking interactions. These results indicate that click reactions can introduce multifunctional groups onto PMOs, thus demonstrating the great potential of PMOs for environmental applications.     

Rationally Designed Axially Chiral Diarylethene Switches with High Helical Twisting Power

Three rationally designed axially chiral diarylethene switches were synthesized and their application as chiral dopants for phototunable cholesteric liquid crystal devices was investigated. Design of these molecules was based on the combination of photochromic dithienylcyclopentene core with bridged binaphthyl units as chiral precursors. Aromatic groups were introduced to the molecules at 6,6′‐positions of binaphthyls through a Suzuki–Miyaura coupling reaction. Their helical twisting powers (HTPs) are significantly higher than those of the known chiral diarylethenes reported as chiral dopants so far. Photocyclization of these molecules upon light irradiation brought out dramatic variation in HTPs between different states. The primary colors, red, green, and blue, were obtained in reflection on light irradiation and with thermal stability. Moreover, a multi‐switchable photodisplay was demonstrated using one of these chiral molecular switches.     

Exceedingly Fast Copper(II)‐Promoted ortho CH Trifluoromethylation of Arenes using TMSCF3

The direct ortho‐trifluoromethylation of arenes, including heteroarenes, with TMSCF₃ has been accomplished by a copper(II)‐promoted C? H activation reaction which completes within 30 minutes. Mechanistic investigations are consistent with the involvement of C? H activation, rather than a simple electrophilic aromatic substitution (S_EAr), as the key step.