Exciplex emission in the blend of two blue luminescent materials

Organic light-emitting diodes (OLEDs) based on the blend of two blue luminescent materials N,N′-bis(1-naphthyl)-N,N′-diphenyl-1,1′-diphenyl-4,4′-diamine (NPB) and 2-(4-biphenylyl)-5(4-tert-butyl-phenyl)-1,3,4-oxadiazole (PBD) were fabricated. The electroluminescence (EL) spectra of this device showed a new emission that is different from their intrinsic exciton emission. Compared with the photoluminescence (PL) spectra of single layer NPB and PBD, respectively, there was an apparent red shift in that of their blend. Thus the exciplex formation in the blend can be concluded due to the similar emission in both PL and EL spectra. The exciplex formation process and the effect of applied voltage were analyzed by Gaussian fitting.     

Direct calculation of time varying Aharonov-Bohm effect

The Aharonov-Bohm effect (ABE) for steady magnetic fields is a well known phenomenon. However, if the current in the infinite solenoid that creates the magnetic field is time-dependent, that is in the presence of both magnetic and electric fields, there is no agreement whether the effect would be present. In this note, we try to investigate time varying ABE by a direct calculation in a set-up with a weak time dependent magnetic field. We find that the electric field arising out of the time-varying magnetic field in the path of the electrons does not enter the action integral but only changes the path of the electron from the source to the slits and then on to the detector. We find a frequency dependent AB phase shift. At low frequencies the result smoothly approaches the one for a constant field as the frequency tends towards zero. On the other hand, for high frequencies such that the AB-phase induced in the path of the wave packet oscillates rapidly, the net effect will be very small which is borne out by our results.     

Expedition on surface adsorption of N-nitrosodiethylamine from rubber fumes on blue phosphorene sheets – a first-principles insight

In recent days, humans are easily exposed to many work-related health issues. N-nitrosodiethylamine (NDE), which is considered to be a harmful carcinogenic agent released from rubber-based industries imparts a long-lasting effect on human health and immunity system. The current research investigates the ability of the two-dimensional nanomaterial, blue phosphorene nanosheet (BPNS) to detect the presence of NDE in the environment. Besides, the electronic and structural characteristics of BPNS are initially explored and NDE target vapour is permitted to interact with the chief component, BPNS. We have also designed blue phosphorene device to study the adsorption properties of NDE vapours based on current–voltage characteristics. The adsorption attributes are accounted for the target vapour adsorbed chief component, the results suggest that BPNS can be employed in detecting NDE vapours.     

13C chemical shift tensors in MOF α-Mg3(HCOO)6: Which component is more sensitive to host-guest interaction?

Metal–organic frameworks (MOFs) are a class of important porous materials with many current and potential applications. Their applications almost always involve the interaction between host framework and guest species. Therefore, understanding of host–guest interaction in MOF systems is fundamentally important. Solid-state NMR spectroscopy is an excellent technique for investigating host–guest interaction as it provides information complementary to that obtained from X-ray diffraction. In this work, using MOF α-Mg₃(HCOO)₆ as an example, we demonstrated that ¹³C chemical shift tensor of organic linker can be utilized to probe the host–guest interaction in MOFs. Obtaining ¹³C chemical shift tensor components (δ₁₁, δ₂₂, and δ₃₃, where δ₁₁ ≥ δ₂₂ ≥ δ₃₃) in this MOF is particularly challenging as there are six coordinatively equivalent but crystallographically non-equivalent carbons in the unit cell with very similar local coordination environment. Two-dimensional magic-angle-turning experiments were employed to measure the ¹³C chemical shift tensors of each individual crystallographically non-equivalent carbon in three microporous α-Mg₃(HCOO)₆ samples with different guest species. The results indicate that the δ₂₂ component (with its direction approximately being co-planar with the formate anion and perpendicular to the C−H bond) is more sensitive to the adsorbate molecules inside the MOF channel due to the weak C−H···O hydrogen bonding or the ring current effect of benzene. The ¹³C isotropic chemical shift, on the other hand, seems much less sensitive to the subtle changes in the local environment around formate linker induced by adsorption. The approach described in this study may be used in future studies on host–guest interaction within MOFs.     

Calculating nuclear magnetic resonance chemical shifts in solvated systems

The nuclear magnetic resonance (NMR) chemical shift is extremely sensitive to molecular geometry, hydrogen bonding, solvent, temperature, pH, and concentration. Calculated magnetic shielding constants, converted to chemical shifts, can be valuable aids in NMR peak assignment and can also give detailed information about molecular geometry and intermolecular effects. Calculating chemical shifts in solution is complicated by the need to include solvent effects and conformational averaging. Here, we review the current state of NMR chemical shift calculations in solution, beginning with an introduction to the theory of calculating magnetic shielding in general, then covering methods for inclusion of solvent effects and conformational averaging, and finally discussing examples of applications using calculated chemical shifts to gain detailed structural information.     

高频单线圈双调谐NMR单晶探头的研制

本文报道了一种测角单晶NMR探头。该探头采用单线圃双调谐电路,工作频率在90MHz-110 MHz连续可调,可进行交叉极化大功率去耦实验。文中提出了一种简单而有效的测角装置,可使单晶绕三个互相垂直轴转动实现单晶的NMR测量。作为典型的应用例子,本文利用该探头实现了单晶DGO(2NH₂CH₂COOH·H₂C₂O₄)屏蔽张量的测量。     

二茂铁有机锡衍生物的13C,119Sn NMR研究

本文测定了几种二茂铁有机锡衍生物的¹¹⁹Sn,¹³C NMR谱。对其中几种衍生物的¹³C NMR谱进行了归属,从而进一步验证了这类化合物的结构。着重讨论了结构如化合物中取代基X的改变对¹¹⁹Sn化学位移的影响。并对结构如 类化合物N→Sn异侧配位的问题进行了讨论。     

J-matrix method of scattering in one dimension: The nonrelativistic theory

We formulate a theory of nonrelativistic scattering in one dimension based on the J-matrix method. The scattering potential is assumed to have a finite range such that it is well represented by its matrix elements in a finite subset of a basis that supports a tridiagonal matrix representation for the reference wave operator. Contrary to our expectation, the 1D formulation reveals a rich and highly nontrivial structure compared to the 3D formulation. Examples are given to demonstrate the utility and accuracy of the method. It is hoped that this formulation constitutes a viable alternative to the classical treatment of 1D scattering problem and that it will help unveil new and interesting applications.     

具有位数3和4的双随机循环矩阵中的素元

本文研究了双随机循环矩阵中素元的分类问题．由于任一n阶双随机循环矩阵都可以唯一地表示为移位的n-1次一元多项式,从而可把双随机循环矩阵中素元的分类问题简化为解双随机循环矩阵上的一个方程．应用此原理,本文完全解决了判别具有位数3的n阶双随机循环矩阵是否为素元的问题,并给出了n阶双随机循环矩阵中一类具有位数4的素元．