Designing spirobifullerene core based three-dimensional cross shape acceptor materials with promising photovoltaic properties for high-efficiency organic solar cells

The development of organic electron acceptor materials is one of the key factors for realizing high-performance organic solar cells (OSCs). Nonfullerene electron acceptors, compared to traditional fullerene acceptor materials, have gained much impetus owing to their better optoelectronic tunabilities and lower cost, as well as higher stability. Therefore, 5 three-dimensional (3D) cross-shaped acceptor materials having a spirobifullerene core flanked with 2,1,3-benzothiadiazole are designed from a recently synthesized highly efficient acceptor molecule SF(BR) ₄ and are investigated in detail with regard to their use as acceptor molecules in OSCs. The density functional theory (DFT) and time-dependent DFT (TDDFT) calculations have been performed for the estimation of frontier molecular orbital (FMO) analysis, density of states analysis, reorganization energies of electron and hole, dipole moment, open-circuit voltage, photo-physical characteristics, and transition density matrix analysis. In addition, the structure-property relationship is studied, and the influence of end-capped acceptor modifications on photovoltaic, photo-physical, and electronic properties of newly selected molecules ( H1-H5 ) is calculated and compared with reference ( R ) acceptor molecule SF(BR) ₄ . The structural tailoring at terminals was found to effectively tune the FMO band gap, energy levels, absorption spectra, open-circuit voltage, reorganization energy, and binding energy value in selected molecules H1 to H5 . The 3D cross-shaped molecules H1 to H5 suppress the intermolecular aggregation in PTB7-Th blend, which leads to high efficiency of acceptor material H1 to H5 in OSCs. Consequently, better optoelectronic properties are achieved from designed molecules H1 to H5 . It is proposed that the conceptualized molecules are superior than highly efficient spirobifullerene core-based SF(BR) ₄ acceptor molecules and, thus, are recommended to experiments for future developments of highly efficient solar cells.     

Parametric Quintic-Spline Approach to the Solution of a System of Fourth-Order Boundary-Value Problems

In this paper, we use parametric quintic splines to derive some consistency relations which are then used to develop a numerical method for computing the solution of a system of fourth-order boundary-value problems associated with obstacle, unilateral, and contact problems. It is known that a class of variational inequalities related to contact problems in elastostatics can be characterized by a sequence of variational inequations, which are solved using some numerical method. Numerical evidence is presented to show the applicability and superiority of the new method over other collocation, finite difference, and spline methods.     

Salt effects in the aqueous alkaline hydrolysis of N-hydroxyphthalimide. Kinetic evidence for the ion-pair formation

The effects of the concentrations of LiCl, NaCl, KCl, CsCl, Na₂CO₃, BaCl₂, and Me₄NCl on the rates of reactions of hydroxide ion with ionized N-hydroxyphthalimide (NHP) at 30°C and in a H₂O–MeCN solvent containing 98%, v/v, H₂O reveal a nonlinear increase in observed rate constants with increase in salt concentrations. The observed rate constants are highly sensitive to the valence state of cations and almost insensitive to the valence state of anions of the salts. These observations are explained in terms of ion-pair formation between cations and NHP^?.     

The influence of synthetic conditions on the stability of methotrexate-monoclonal antibody conjugates determined by reversed phase high performance liquid chromatography.

Methotrexate (MTX) has been convalently attached to an IgG-type monoclonal antibody (791T/36) directed to tumour-associated antigen gp72. Conjugates were synthesized by the active ester method using MTX N-succinimidyl ester at various pH values (7.5-10.5). Following purification by gel filtration, high performance liquid chromatography was used to assess the free drug or its derivatives in samples of MTX-791T/36 conjugates previously treated (or not) with hydroxylamine. Quantitative analysis, performed on a reversed phase column (pore size 300 A) with isocratic acetonitrile-sodium acetate buffer (pH 4.8) as mobile phase, indicated no detectable amount of free methotrexate in hydroxylamine-treated conjugates even six months after their preparation. Similar observations were made with conjugates, whose synthesis were performed at pH greater than or equal to 10. In contrast, the presence of increasing amounts of drug/metabolite could be demonstrated in samples produced at lower pH values. Based on these findings, the pH-dependent kinetics of MTX release has been determined and used to design conditions under which stable MTX-791T/36 conjugates could be prepared without hydroxylamine reaction.     

Studies on recoil proton tracks in NTA films with the T(d,n)He reaction

Recoil proton tracks in nuclear emulsion are counted by scanning them using strip, square or circular field of view of optical microscope. In this paper, the overestimate due to the edge effects in counting recoil proton tracks at different neutron energies produced from the T(d,n)⁴He reaction has been determined by measuring the true track density in NTA film. The overestimate has also been calculated using the measured value of the mean projected track length (L) in the film. The percentage of measured overestimates has been compared with those obtained by calculation and the results agree reasonably well. Fading effect in NTA film has been studied and found to be 22% more in the summer than in the winter season. A great reduction in fading rate could be achieved if the films are desiccated and sealed in highly pure dry nitrogen maintained at an over-pressure of 1000 Pa to reduce water vapour ingress. After the edge effect correction, the sensitivity of NTA film has been calculated from (1.72±0.08)×10⁻³ tracksn⁻¹ to (1.97±0.16)×10⁻³ tracksn⁻¹ in the neutron energy ranges from 15.91 to 18.88 MeV. The response was found to be from 0.24±0.02 trackscm⁻² permSv to 0.26±0.01 trackscm⁻² permSv in the same energy range.