A Mechanistic Switch in C-H Bond Activation by Elusive Fe\begin{document}$^\text{V}$\end{document}(O)(TAML) Reaction Intermediate: A Theoretical Study

The divergent behavior of C-H bond oxidations of aliphatic substrates compared to those of aromatic substrates shown in Gupta's experiment was mechanistically studied herein by means of density functional theory calculations. Our calculations reveal that such difference is caused by different reaction mechanisms between two kinds of substrates (the aliphatic cyclohexane, 2, 3-dimethylbutane and the aromatic toluene, ethylbenzene and cumene). For the aliphatic substrates, C-H oxidation by the oxidant Fe\begin{document}$^{\rm{V}}$\end{document}(O)(TAML) is a hydrogen atom transfer process; whereas for the aromatic substrates, C-H oxidation is a proton-coupled electron transfer (PCET) process with a proton transfer character on the transition state, that is, a proton-coupled electron transfer process holding a proton transfer-like transition state (PCET(PT)). This difference is caused by the strong \begin{document}$\pi$\end{document}-\begin{document}$\pi$\end{document} interactions between the tetra-anionic TAML ring and the phenyl ring of the aromatic substrates, which has a "pull" effect to make the electron transfer from substrates to the Fe=O moiety inefficient.     

Three-Dimensional Cu-Ni Composite Superamphiphobic Surface via Electrodeposition and Fluorosilane Modification

A superamphiphobic (SAP) surface was fabricated by electrodepositing Cu-Ni micro-nano particles on aluminum substrate and modifying via 1H, 1H, 2H, 2H-perfluorodecyltrimethoxysilane. Scanning electron microscopy, X-ray diffraction, energy-dispersive X-ray spectroscopy, and Fourier-transform infrared spectroscopy were employed to investigate the morphology and chemical composition. The results showed that the SAP surface had three-dimensional micro-nano structures and exhibited a maximum water contact angle of 160.0\begin{document}$ ^{\circ} $\end{document}, oil contact angle of 151.6\begin{document}$ ^{\circ} $\end{document}, a minimum water slide angle of 0\begin{document}$ ^{\circ} $\end{document} and oil slide angle of 9\begin{document}$ ^{\circ} $\end{document}. The mechanical strength and chemical stability of the SAP surface were tested further. The experimental results showed that the SAP surface presented excellent resistance to wear, prominent acid-resistance and alkali-resistance, self-cleaning and anti-fouling properties.     

Ultrafast Electron Transfer in All-Small-Molecule Photovoltaic Blends Promoted by Intermolecular Interactions in Cyanided Donors

Cyano substitution has been established as a viable approach to optimize the performance of all-small-molecule organic solar cells. However, the effect of cyano substitution on the dynamics of photo-charge generation remains largely unexplored. Here, we report an ultrafast spectroscopic study showing that electron transfer is markedly promoted by enhanced intermolecular charge-transfer interaction in all-small-molecule blends with cyanided donors. The delocalized excitations, arising from intermolecular interaction in the moiety of cyano-substituted donor, undergo ultrafast electron transfer with a lifetime of \begin{document}$ \sim $\end{document}3 ps in the blend. In contrast, some locally excited states, surviving in the film of donor without cyano substitution, are not actively involved in the charge separation. These findings well explain the performance improvement of devices with cyanided donors, suggesting that manipulating intermolecular interaction is an efficient strategy for device optimization.     

Delocalized \begin{document}$\pi_3^6$\end{document} Bond in OX\begin{document}$_2$\end{document} (X=Halogen) Molecules

OX\begin{document}$_2$\end{document} (X=halogen) molecules was studied theoretically. Calculation results show that delocalized \begin{document}$\pi_3^6$\end{document} bonds exist in their electronic structures and O atoms adopt the sp\begin{document}$^2$\end{document} type of hybridization, which violates the prediction of the valence shell electron pair repulsion theory of sp\begin{document}$^3$\end{document} type. Delocalization stabilization energy is proposed to measure the contribution of delocalized \begin{document}$\pi_3^6$\end{document} bond to energy decrease and proves to bring extra-stability to the molecule. These phenomena can be summarized as a kind of coordinating effect.     

Synthesis and Electro-magnetic Properties of Polyaniline-barium Ferrite Nanocomposite

"The polyaniline (PANI)-barium ferrite composite with magnetic behavior was synthesized by in situ poly-merization of aniline in the presence of BaFe12O19 nanoparticles of 60-80 nm in diameters. The structure, morphology and magnetic properties of samples were characterized by powder X-ray diffraction, Fourier transform infrared, scanning electron microscopy, transmission electron microscopy and vibrating sample magnetometer technique. The results of spectroanalysis indicated that there was interaction between PANIchains and ferrite particles. The composite exhibited the hysteresis loops of the ferromagnetic nature. The saturated magnetization of composite was 22.2 emu/g and the conductance was 0.069 S/cm."     

Microwave Spectrum and Structure of 2-(Trifluoromethyl)pyridine

The high resolution rotational spectrum of 2-(trifluoromethyl)pyridine in 2\begin{document}$ - $\end{document}20 GHz was recorded and analyzed. Spectroscopic parameters including rotational constants, nuclear quadrupole coupling constants of \begin{document}$ ^{14} $\end{document}N as well as the centrifugal distortion constants were determined. The rotational spectra of five mono-substituted \begin{document}$ ^{13} $\end{document}C and one \begin{document}$ ^{15} $\end{document}N isotopologues were also measured and assigned in natural abundance. Experimental results complemented by ab initio calculations lead to an accurate determination of the skeleton structure. The values of the planar moment inertia \begin{document}$ P_{cc} $\end{document} were determined to be 44.46 u?\begin{document}$ ^2 $\end{document} for all the measured isotopologues, indicating a C\begin{document}$ _ \rm{s} $\end{document} symmetry of this molecule. The molecular electrostatic surface potential was calculated to illustrate the trifluoromethyl substitution effects on the electron distribution.     

Direct Observation of Transient Species Generated from Protonation and Deprotonation of the Lowest Triplet of p-Nitrophenylphenol

Photo-induced proton coupled electron transfer (PCET) is essential in the biological, photosynthesis, catalysis and solar energy conversion processes. Recently, \begin{document}$ p $\end{document}-nitrophenylphenol (HO-Bp-NO₂) has been used as a model compound to study the photo-induced PCET mechanism by using ultrafast spectroscopy. In transient absorption spectra both singlet and triplet states were observed to exhibit PCET behavior upon laser excitation of HO-Bp-NO₂. When we focused on the PCET in the triplet state, a new sharp band attracted us. This band was recorded upon excitation of HO-Bp-NO₂ in aprotic polar solvents, and has not been observed for \begin{document}$ p $\end{document}-nitrobiphenyl which is without hydroxyl substitution. In order to find out what the new band represents, acidic solutions were used as an additional proton donor considering the acidity of HO-Bp-NO₂. With the help of results in strong (\begin{document}$ \sim $\end{document}10\begin{document}$ ^{-1} $\end{document} mol/L) and weak (\begin{document}$ \sim $\end{document}10\begin{document}$ ^{-4} $\end{document} mol/L) acidic solutions, the new band is identified as open shell singlet O-Bp-NO₂H, which is generated through protonation of nitro O in \begin{document}$ ^3 $\end{document}HO-Bp-NO₂ followed by deprotonation of hydroxyl. Kinetics analysis indicates that the formation of radical \begin{document}$ \cdot $\end{document}O-Bp-NO₂ competes with O-Bp-NO₂H in the way of concerted electron-proton transfer and/or proton followed electron transfers and is responsible for the low yield of O-Bp-NO₂H. The results in the present work will make it clear how the \begin{document}$ ^3 $\end{document}HO-Bp-NO₂ deactivates in aprotic polar solvents and provide a solid benchmark for the deeply studying the PCET mechanism in triplets of analogous aromatic nitro compounds.     

Iterative Multireference Configuration Interaction

Iterative multireference configuration interaction (IMRCI) is proposed. It is exploited to compute the electronic energies of H\begin{document}$_2$\end{document}O and CH\begin{document}$_2$\end{document} (singlet and triplet states) at equilibrium and non-equilibrium geometries. The potential energy curves of H\begin{document}$_2$\end{document}O, CH\begin{document}$_2$\end{document} (singlet and triplet states) and N\begin{document}$_2$\end{document} have also been calculated with IMRCI as well as the M?ller Plesset perturbation theory (MP2, MP3, and MP4), the coupled cluster method with single and double substitutions (CCSD), and CCSD with perturbative triples correction (CCSD(T)). These calculations demonstrate that IMRCI results are independent of the initial guess of configuration functions in the reference space and converge quickly to the results of the full configuration interaction. The IMRCI errors relative to the full configuration interaction results are at the order of magnitude of 10\begin{document}$^{-5}$\end{document} hartree within just 2-4 iterations. Further, IMRCI provides an efficient way to find on the potential energy surface the leading electron configurations which, as correct reference states, will be very helpful for the single-reference and multireference theoretical models to obtain accurate results.     

Bias-Polarity Dependent Electroluminescence from a Single Platinum Phthalocyanine Molecule

By using scanning tunneling microscope induced luminescence (STML) technique, we investigate systematically the bias-polarity dependent electroluminescence behavior of a single platinum phthalocyanine (PtPc) molecule and the electron excitation mechanisms behind. The molecule is found to emit light at both bias polarities but with different emission energies. At negative excitation bias, only the fluorescence at 637 nm is observed, which originates from the LUMO→HOMO transition of the neutral PtPc molecule and exhibits stepwise-like increase in emission intensities over three different excitation-voltage regions. Strong fluorescence in region (Ⅰ) is excited by the carrier injection mechanism with holes injected into the HOMO state first; moderate fluorescence in region (Ⅱ) is excited by the inelastic electron scattering mechanism; and weak fluorescence in region (Ⅲ) is associated with an up-conversion process and excited by a combined carrier injection and inelastic electron scattering mechanism involving a spin-triplet relay state. At positive excitation bias, more-than-one emission peaks are observed and the excitation and emission mechanisms become complicated. The sharp molecule-specific emission peak at ~911 nm is attributed to the anionic emission of PtPc\begin{document}$^-$\end{document} originated from the LUMO+1→LUMO transition, whose excitation is dominated by a carrier injection mechanism with electrons first injected into the LUMO+1 or higher-lying empty orbitals.     

Synthesis and Tribological Properties of Tubular NbS2 and TaS2 Nanostructures

"NbS2 and TaS2 nanostubes were prepared via solid state reaction method, and their tribological properties were studied over a wide range of normal loads and sliding velocities. The size distributions and shapes of sulfides were characterized using transmission electron microscopy and scanning electron microscopy. The results indicated that the NbS2 and TaS2 compounds had tubular structures with the mean diameter of 100 nm and length of 10 mm. The effect of NbS2 and TaS2 nanotubes added in commercial lubricating oil T40, was initially studied using the instrument MS-T3000. The results showed that the antiwear ability of NbS2 and TaS2 as additives was obviously better than that of the normal lubricating oil in ambient conditions. The general frictional properties of the solid lubricant containing TaS2 is better than those of the solid lubricant containing NbS2. The frictional mechanism was discussed."     

MoO2微米空心球的水热合成及合成机理研究

Micrometer-sized MoO2 hollow spheres were synthesized hydrothermally with ammonium heptamolybdate tetrahydrate as molybdenum source, Cetyltrimethylammonium bromide as structure-directing agent and C2H5OH as reducing agent, respectively. The products were investigated by X-ray diffraction, thermo- gravimetry and differential thermal analysis, scanning electron microscopy, transmission electron microscopy and X-ray photoelectron spectroscopy. A morphology transition of "blocks-solid spheres-hollow spheres" during the growth process was observed and the possible mechanism for the formation of MoO2 samples was proposed to be through a microscale Kirkendall effect.     

Location Effect in a Photocatalytic Hybrid System of Metal-Organic Framework Interfaced with Semiconductor Nanoparticles

We report an ultrafast spectroscopy investigation that addresses the subtle location effect in a prototypical semiconductor-MOF hybrid system with TiO\begin{document}$_2$\end{document} nanoparticles being incorporated inside or supported onto Cu\begin{document}$_3$\end{document}(BTC)\begin{document}$_2$\end{document}, denoted as TiO\begin{document}$_2$\end{document}@Cu\begin{document}$_3$\end{document}(BTC)\begin{document}$_2$\end{document} and TiO\begin{document}$_2$\end{document}/Cu\begin{document}$_3$\end{document}(BTC)\begin{document}$_2$\end{document}, respectively. By tracking in real time the interface electron dynamics in the hybrid system, we find that the interface states formed between TiO\begin{document}$_2$\end{document} and Cu\begin{document}$_3$\end{document}(BTC)\begin{document}$_2$\end{document} can act as an effective relay for electron transfer, whose efficiency rests on the relative location of the two components. It is such a subtle location effect that brings on difference in photocatalytic CO\begin{document}$_2$\end{document} reduction using the two semiconductor-MOF hybrids. The mechanistic understanding of the involved interface electron-transfer behavior and effect opens a helpful perspective for rational design of MOF-based hybrid systems for photoelectrochemical applications.     

Excess-Electron Attachment and Ionization of Aqueous Uridine Monophosphate Anion

We applied quantum mechanics/classical mechanics simulations to study excess-electron attachment and ionization of uridine monophosphate anion (dUMP\begin{document}$^-$\end{document}) in explicit aqueous solutions. We calculated vertical electron affinities (VEAs), adiabatic electron affinities (AEAs), vertical detachment energies (VDEs), vertical ionization energies (VIEs), and adiabatic ionization energies (AIEs) of the 40 structures obtained from molecular dynamic trajectory. The excess-electron and hole distributions were analyzed in electron attachment and ionization of aqueous dUMP\begin{document}$^-$\end{document}. The converged mean VEA (-0.31 eV) and AEA (2.13 eV) suggest that excess-electron can easily attach to dUMP\begin{document}$^-$\end{document}. The mean vertical (-0.50 e) and adiabatic (-0.62 e) excess-electron on uracil reveal that main excess-electrons are localized on nucleobases at the most snapshots. The distributions at several special snapshots demonstrate the excess-electron delocalization over nucleobases/ribose or ribose/phosphate group after the structural relaxations of dUMP\begin{document}$^{2-}$\end{document} dianion. The VDE value (2.78 eV) indicates that dUMP\begin{document}$^{2-}$\end{document} dianion could be very stable. Moreover, the mean VIE is 8.13 eV which is in agreement with the previous calculation using solvation model. The hole distributions on uracil suggest that the nucleobases are easily ionized after the irradiation of high-energy rays. In vertical ionizations, the holes would be delocalized over uracil and ribose at several snapshots. Observing the adiabatic hole distributions, it can be found that electrons on phosphate group and holes on nucleobases can be transferred to ribose at the special snapshots in the structural relaxation of neutral species.     

Synthesis and Characterization of ZnO Ellipsoid-like Nanostructures

"ZnO ellipsoid-like structures assembled by ZnO nanrods were fabricated from common ZnO whiskers by autoclave tests and pyrolysis integrated method. X-ray diffraction, scanning electron microscopy, transmission electron microscopy, selected area electron diffraction, and high resolution transmission electron microscopy studies reveal ZnO ellipsoidal structures are single-crystals and formed from direct oriented attachment of nanorods. Raman and room temperature photoluminescence spectra are also discussed."     

Relative Molecular Orientations in Organic Optoelectronic Films Probed via Polarization-Selected UV/IR Mixed Frequency Ultrafast Spectroscopy

Molecular packing patterns are crucial factors determining electron/energy transfer processes that are critical for the optoelectronic properties of organic thin film devices. Herein, the polarization-selective ultraviolet/infrared (UV/IR) mixed frequency ultrafast spectroscopy is applied to investigate the relative molecular orientations in two organic thin films of 7-(diethylamino)coumarin-3-carboxylic acid (DEAC) and perylene. The signal anisotropy changes caused by intermolecular energy/electron transfers are utilized to calculate the cross angles between the electronic transition dipole moment of the donor and the vibrational transition dipole moments of the acceptor, yielding the relative orientation between two adjacent molecules. Using this method, the relative orientation angle in DEAC film is determined to be 53.4\begin{document}$ ^\circ $\end{document}, close to 60\begin{document}$ ^\circ $\end{document} of its single crystalline structure, and that of the perylene film is determined to be 6.2\begin{document}$ ^\circ $\end{document}, also close to \begin{document}$ - $\end{document}0.2\begin{document}$ ^\circ $\end{document} of its single crystalline structure. Besides experimental uncertainties, the small difference between the angles determined by this method and those of single crystals also results from the fact that the thin film samples are polycrystalline where some of the molecules are amorphous.     

Two-Dimensional Electronic Spectroscopy with Active Phase Management?

Two-dimensional electronic spectroscopy (2DES) is a powerful method to probe the coherent electron dynamics in complicated systems. Stabilizing the phase difference of the incident ultrashort pulses is the most challenging part for experimental demonstration of 2DES. Here, we present a tutorial review on the 2DES protocols based on active phase managements which are originally developed for quantum optics experiments. We introduce the 2DES techniques in box and pump-probe geometries with phase stabilization realized by interferometry, and outline the fully collinear 2DES approach with the frequency tagging by acoustic optical modulators and frequency combs. The combination of active phase managements, ultrashort pulses and other spectroscopic methods may open new opportunities to tackle essential challenges related to excited states.      

Influence of Electron Donating Ability on Reverse Intersystem Crossing Rate for One Kind of Thermally Activated Delayed Fluorescence Molecules

First-principles calculations are applied for investigating influence of electron donating ability of donor groups in eight thermally activated delayed fluorescence (TADF) molecules on their geometrical structures and transition properties as well as reverse intersystem crossing (RISC) processes. Results show that the diphenylamine substitution in the donor part can slightly change the bond angle but decrease bond length between donor and acceptor unit except for the lowest triplet state (T\begin{document}$_1$\end{document}) of carbazole-xanthone molecule. As the electron donating ability of donor groups is increased, the overlap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) is decreased. As the diphenylamine groups are added in donor part, the delocalization of HOMO is enlarged, which brings a decreased energy gap (\begin{document}$\Delta E$\end{document}\begin{document}$_{\text{S}_1\text{-T}_1}$\end{document}) between the lowest singlet excited state (S\begin{document}$_1$\end{document}) and T\begin{document}$_1$\end{document} state. Furthermore, with the calculated spin-orbit coupling coefficient (\begin{document}$H_{\text{so}}$\end{document}), one finds that the larger value of \begin{document}$\displaystyle{\frac{\langle S_1|\hat{H}_{\text{so}}|{T}_1\rangle^2}{\Delta E_{\text{S}_1\text{-T}_1}^2}}$\end{document} is, the faster the RISC is. The results show that all investigated molecules are promising candidates as TADF molecules. Overall, a wise molecular design strategy for TADF molecules, in which a small \begin{document}$\Delta E_{\text{S}_1\text{-T}_1}$\end{document} can be achieved by enlarging the delocalization of frontier molecular orbitals with large separation between HOMO and LUMO, is proposed.     

Field Emission Properties of Multi-walled Carbon Nanotubes Grown on Silicon Nanoporous Pillar Array

"Multi-walled carbon nanotubes (CNTs) were grown on a silicon nanoporous pillar array (Si-NPA) by thermal chemical vapor deposition. Surface morphologies and microstructure of the resultant were studied by a field emission scanning electron microscope, Raman spectrum, transmission electron microscope, and highresolution transmission electron microscopy. The composition of samples was determined by energy dispersive X-ray spectroscopy (EDS). The results showed that a great deal of CNTs, with diameter in the range of 20-70 nm, incorporated with Si-NPA and a large scale nest array of CNTs/Si-NPA (NACNT/Si-NPA) was formed. EDS analysis showed that the composition of carbon nanotubes was carbon. Field emission measurements showed that a current density of 5 mA/cm2 was obtained at an electric field of 4.26 V/1m, with a turn-on field of 1.3 V/1m. The enhancement factor calculated according to the Fowler-Nordheim theory was ?11,000. This excellent field emission performance is attributed to the unique structure and morphology of NACNT/Si-NPA, especially the formation of a nest-shaped carbon nanotube array. A schematic drawing that illustrates the experimental configuration is given. These results indicate that NACNT/Si-NPA might be an ideal candidate cathode for potential applications in flat panel displays."     

Controlled Synthesis of Se/Te Alloy and Te Nanowires

"Se/Te alloy and Te nanowires (NWs) with different morphologies were synthesized through a novel, control-lable solution-phase method. Sodium dodecylbenzene sulfonate was employed as a surfactant to control the reaction rate in the synthesis. Through reaction process dynamics control, both "bending" and "V-shaped" Se/Te alloy NWs were controllably produced. The phase structures and morphologies of the Se/Te and Te products were investigated with XRD, TEM, and HRTEM. The formation mechanisms of the NWs were investigated on the basis of the experimental results. The significance of these results lies in the important implications concerning the potential use of these NWs materials for nanoscale electronic devices."     

Superparticles Formed by Amphiphilic Tadpole-like Single Chain Polymeric Nanoparticles and Their Application as an Ultrasonic Responsive Drug Carrier

Herein, we report self-assembly of tadpole-like single chain polymeric nanoparticles (TPPs) and the ultrasonic response of the resultant superparticles. The TPPs are with an intramolecularly crosslinked poly(2-(methacryloyloxy)ethyl pent-4-ynoate)-r-poly(hydroxyethyl methacrylate) (PMAEP-r-PHEMA) chain as the "head" and a poly(2-(dimethylamino)ethyl methacrylate (PDMAEMA) linear chain as the "tail", and are pre-pared simply and efficiently by Glaser-coupling of the pendant alkynes in the PMAEP-r-PHEMA block in the common solvent methanol. The formation of the TPPs was confirmed by gel permeation chromatograph, nuclear magnetic resonance spectroscopy, dynamic light scattering, static dynamic scattering, and transmission electron microscopy. In aqueous solution, the amphiphilic TPPs could self-assemble into regular superparticles, driven by ag-gregation of the hydrophobic "heads". Since in the structure there is no chain entanglement and the embedding of PDMAEMA chains disturb close-packing of the "heads", the superpar-ticles are responsive to a low-energy ultrasonic vibration, as evidenced by greatly enhanced release of the functional molecules from the superparticles by treatment of a low-energy ultrasound. Therefore, the superparticles should be very promising in the use as the drug carriers that can be manipulated from a long distance, considering that ultrasonic energy can be focused at a small area in a relatively long distance from the ultrasound-radiating source.