Blue TiO2 nanotube arrays as semimetallic materials with enhanced photoelectrochemical activity towards water splitting

In the past years there has been a great interest in self-doped TiO₂ nanotubes (blue TiO₂ nanotubes) compared to undoped ones owing to their high carrier density and conductivity. In this study, blue TiO₂ nanotubes are investigated as photoanode materials for photoelectrochemical water splitting. Blue TiO₂ nanotubes were fabricated with enhanced photoresponse behavior through electrochemical cathodic polarization on undoped and annealed TiO₂ nanotubes. The annealing temperature of undoped TiO₂ nanotubes was tuned before cathodic polarization, revealing that annealing at 500 °C improved the photoresponse of the nanotubes significantly. Further optimization of the blue TiO₂ nanotubes was achieved by adjusting the cathodic polarization parameters. Blue TiO₂ nanotubes obtained at the potential of –1.4 V (vs. SCE) with a duration of 10 min exhibited twice more photocurrent response (0.39 mA cm^-2) compared to the undoped TiO₂ nanotube arrays (0.19 mA cm^-2). Oxygen vacancies formed through the cathodic polarization decreased charge recombination and enhanced charge transfer rate; therefore, a high photoelectrochemical activity under visible light irradiation could be achieved.     

Probing the Local Magnetic Structure of the [FeIII(Tp)(CN)3]− Building Block Via Solid-State NMR Spectroscopy,Polarized Neutron Diffraction,and First-Principle Calculations

The local magnetic structure in the [Fe^III(Tp)(CN)₃]⁻ building block was investigated by combining paramagnetic Nuclear Magnetic Resonance (pNMR) spectroscopy and polarized neutron diffraction (PND) with first-principle calculations. The use of the pNMR and PND experimental techniques revealed the extension of spin-density from the metal to the ligands, as well as the different spin mechanisms that take place in the cyanido ligands: Spin-polarization on the carbon atoms and spin-delocalization on the nitrogen atoms. The results of our combined density functional theory (DFT) and multireference calculations were found in good agreement with the PND results and the experimental NMR chemical shifts. Moreover, the ab-initio calculations allowed us to connect the experimental spin-density map characterized by PND and the suggested distribution of the spin-density on the ligands observed by NMR spectroscopy. Interestingly, significant differences were observed between the pseudo-contact contributions of the chemical shifts obtained by theoretical calculations and the values derived from NMR spectroscopy using a simple point-dipole model. These discrepancies underline the limitation of the point-dipole model and the need for more elaborate approaches to break down the experimental pNMR chemical shifts into contact and pseudo-contact contributions.     

Atomic Hydrogen Induced Chemical Vapor Deposition of Silicon Oxycarbide Thin Films Derived from Diethoxymethylsilane Precursor

Amorphous silicon oxycarbide (a-SiOC:H) films produced by remote plasma RPCVD from diethoxymethylsilane (DEMS) were characterized in terms of their basic properties related to the coatings deposited using conventional plasma enhanced PECVD method. The effect of substrate temperature (T_S) on the growth rate, chemical composition, structure, and properties of resulting a-SiOC:H films is reported. Film growth is an adsorption-controlled process, wherein two mechanisms can be distinguished with a transition at about T_S=70°C. Depending on the temperature, films of different nature can be obtained, from polymer-like to highly crosslinked material with C-Si-O network. The chemical structure of a-SiOC:H films was characterized by FTIR, ¹³C and ²⁹Si solid-state NMR, and X-ray photoelectron spectroscopes. The a-SiOC:H films were also characterized in terms of their density, refractive index, surface morphology, conformality of coverage, hardness, adhesion to a substrate, and friction coefficient. The films were found to be morphologically homogeneous materials exhibiting good conformality of coverage and small surface roughness. Their refractive index exhibits anomalous effect revealing a minimum value at T_S=125°C. Due to their exceptional physical properties a-SiOC:H films produced by RPCVD from DEMS precursor seems to be useful as potential dielectric materials or coatings for various encapsulation applications.     

Chirality and Magnetic Properties of One-dimensional Ln (Ln = Gd,Dy) Polymers

The usage of the achiral ligand, in lanthanide chemistry, successfully obtained two series of chiral lanthanide complexes, formulated d - and l -{Gd[IN][HIN][CH₂OCH₂O]}_n (abbreviated as Gd ) and d - and l -{Dy[IN][HIN][CH₂OCH₂O]}_n (abbreviated as Dy , HIN = isonicotinic acid). Crystallographic researches determined that four compounds are all one-dimensional (1D) chain structures and crystallized in a chiral space group. In addition, CH₂OHCH₂OH acts as not only solvent but also the bridge ligand. Besides, single crystal circular dichroism (CD) spectra conformed compounds Gd-_L and Gd-_D , Dy-_L and Dy-_D are enantiomers respectively. Magnetically, compound Gd showed predominant magnetocaloric effect (MCE) of 26.20 J · kg^–1 · K^–1 at 2.5 K for ΔH = 7 T, while there is ferromagnetic interactions in compound Dy .     

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.     

Thermal,mechanical and morphological properties of multicomponent blends based on acrylic and styrenic polymers

Multicomponent polymer blends afford polymeric materials with specific properties for many applications. The effect of different chemical structures on the miscibility and compatibility of polymer blends composed of multicomponent acrylic and styrenic polymers was studied in this research. The influence of each component on the thermal, mechanical, and morphological properties, as well as optical transparency, was analyzed in poly (methyl methacrylate), homopolymer (PMMAh), or copolymer (PMMAe) blends where the minority constituents formed by polystyrene (PS), styrene-acrylonitrile copolymer (SAN) or acrylonitrile-butadiene-styrene terpolymer (ABS). The results showed significant changes in the properties of these mixtures due to the effect of the type of chemical structure and different elastomeric domains of the majority and minority components of polymer blends.     

Local process-dependent structural and mechanical properties of extrusion blow molded high-density polyethylene hollow parts

Although applied for several decades, production of hollow plastic parts by extrusion blow molding (EBM) is still over-dimensioned. To overcome this issue, a thorough investigation of the process-structure-property relationship is required. In this study, the local process-structure-property relationship for high-density polyethylene EBM containers is analyzed with differential scanning calorimetry and dynamic mechanic analysis microindentation. Local process-dependent crystallinity and complex modulus data at various processing conditions are supplemented with wide-angle X-ray diffraction and transmission electron microscopy (TEM). The crystallinities and the complex moduli clearly show lower values close to the mold side than at the inner side and the middle of the cross-section, which reflects the temperature gradient during processing. Additionally, the orientation of the polymer chain (c-axis) reveals a low level of biaxiality with a slight tendency towards transverse direction. The biaxiality increases for low mold temperature and high draw ratio. Finally, biaxiality is confirmed with TEM, which reveals no preferred lamellar orientation.     

Determination of tensile strength of UHMWPE fiber-reinforced polymer composites

Quasi-static tensile test of UHMWPE fiber-reinforced composite laminate is challenging to perform due to low interlaminar shear strength and low coefficient of friction. Tensile tests proposed in the literature were conducted and limitations associated with each method led to the evolution of a new method. Tensile test of single-ply was realized as the best representative of tensile strength of a composite than tensile test of UHMWPE laminate. A fixture was developed for single-ply tests which increased friction and provided the mechanical constraint to slipping. The fixture is easy to fabricate and has provided repeatable results for eight grades of UHMWPE fiber-based (0/90) fabrics. Reported tensile strengths are in quite high range of 900–1500 MPa.