Molecular Systems Design & Engineering最新文献

Although the wide-energy-gap hole-transport layer (HTL) is a key material to realizing high-efficiency and long-lifetime phosphorescent and thermally activated delayed fluorescent (TADF) organic light-emitting devices (OLEDs), a limited number of HTLs have been explored in previous studies. Accordingly, dibenzofuran-end-capped HTLs show promising performance in realizing a maximum external quantum efficiency (EQE) of 20% and a long lifetime of over 20?000 h at 1000 cd cm^?2 in phosphorescent and TADF OLEDs. This study investigates the effects of the substitution positions of TnDBFBP (n = 1–4) derivatives with four DBF-end-capping groups to extensively study the molecular design of robust multifunctional HTLs. TnDBFBP derivatives exhibited a high glass transition temperature (T_g) of ～149 °C, a triplet energy (E_T) value of ～2.9 eV, and anionic bond dissociation energy of ～1.75 eV depending on the substitution positions. Consequently, T1DBFBP realized green TADF OLEDs with an EQE of over 20% and an operational lifetime of 50% of the initial luminance (LT₅₀) of 30?000 h at 1000 cd m^?2. These performances are among the best reported by previous studies.

Nonconjugated radical polymers and small molecules are employed as functional materials in organic electronic devices. Furthermore, the unpaired electrons on these materials have permanent magnetic moments, making these materials promising candidates for organic magnets. Through molecular design, strong antiferromagnetic and ferromagnetic ordering have been achieved in conjugated materials. However, the magnetic properties of nonconjugated radical polymers have only shown weak magnetic interactions among the open-shell sites due to the large mean separation between radicals in typical materials. Here, we have designed, synthesized, and crystalized two open-shell molecules that used molecular engineering to control the assembly of the open-shell sites into a strong antiferromagnetically ordered network. The strong antiferromagnetic interaction is evidenced by a high paramagnetic-to-antiferromagnetic transition temperature of ～40 K. This high transition temperature was a result of a high spin exchange coupling constant J of about ?20 cm^?1, which was suggested by both experimental and computed coupling parameters given by the energy difference between high-spin and low-spin broken-symmetry structures. In addition, a single-crystal electrical conductivity of ～10^?3 S m^?1 was achieved, which indicated the potential of this material in electronic applications. Therefore, this work provides an insight into a design strategy for radical-based electronic and magnetic materials through proper molecular structure modifications.

This study examined the role of diphenylalanine (the central hydrophobic cluster of Alzheimer's β-amyloid peptide) in the intermolecular hydrogen-bonded supramolecular sheet and fibril formation. N-phenylglycine appended peptide NPG-Phe-Phe-OMe (1), having a sequence similarity with a diphenylalanine motif, self-aggregates to form entangled fibers. The fibers show green-gold birefringence in a Congo red assay. Moreover, the fibers bind with thioflavin T (ThT) and show an enhanced emission. However, the tyrosine-modified analogues failed to form fibers and rather exhibited a microsphere-like morphology. From X-ray diffraction analysis, the tyrosine-modified analogues, namely, NPG-Phe-Tyr-OMe (2) and NPG-Tyr-Phe-OMe (3), adopt extended conformations and self-aggregate to form sheet-like structures via intermolecular hydrogen bonds and π–π stacking interactions.

We have investigated the possibility of using aluminum functionalized silicene trilayers (ABC-Si₄Al₂) as an anode material for alkali metal ion batteries (AMIBs). First, we studied the thermodynamic stability of ABC-Si₄Al₂ using ab initio molecular dynamics simulations, showing that this material remains stable up to around 600 K. Then, we explored the properties of alkali metal atoms (Li, Na, K) adsorption in ABC-Si₄Al₂, finding several available sites with high average adsorption energies. Moreover, we computed the diffusion properties of those adsorbed atoms along high-symmetry paths using the nudged elastic band method. The results indicated diffusion barriers as low as the ones in graphite, especially for Na (0.32 eV) and K (0.22 eV), which allows those ions to migrate easily on the material's surface. Our studies also revealed that the full loaded Li₄Si₄Al₂, Na₂Si₄Al₂, and K₂Si₄Al₂ systems provide low average open-circuit voltage, ranging from 0.14 to 0.49 V, and large theoretical capacity of 645 mAh g^?1 for Li- and 322 mAh g^?1 for Na- and K-ion batteries, values that are close to the ones in other anode materials, such as graphite, TiO₂, and silicene-based systems. Those results indicate that aluminum functionalized few-layer silicene is a promising material for AMIBs anodes, particularly for Na- and K-ion batteries.

In this study, spatially isolated terbium ions are post-synthetically installed on a two-dimensional (2D) water-stable zirconium-based metal–organic framework (MOF), ZrBTB (BTB = 1,3,5-tri(4-carboxyphenyl)benzene), and the loading of installed terbium ions is adjusted by tuning the synthetic temperature of the post-synthetic process. The crystallinity, porosity, morphology, chemical state, and terbium loading of the obtained materials are characterized. Tb-modified MOFs synthesized at various temperatures were subjected to photoluminescence tests in aqueous environments, and the energy transfer from the BTB linkers to the installed terbium sites is highly tunable by adjusting the temperature for installing terbium. Since the photoluminescence of the installed terbium sites can be quenched by the nitrite ions present in the solution, as a demonstration, the terbium-incorporating MOFs are applied for nitrite quantification by utilizing the Stern–Volmer equation; a high Stern–Volmer constant of 472?000 M^?1 and a low limit of detection of 0.08 μM can be achieved.

Considering the discharge of radioactive and non-radioactive effluents during the mining process, we report on a study that proposes to use optical sensing for the detection and monitoring of pollutants. This is realized by doping of Tb³⁺ ions in a metal–organic framework, namely UiO-66-(COOH)₂, and taking advantage of the host–guest interactions which allow analyte molecules to be pre-concentrated within the pores of the material, thus influencing the light absorption and emission profile of Tb³⁺ ions. Concentration-dependent spectroscopy analysis shows that Tb@UiO-66-(COOH)₂ has a luminescence turn-off behaviour which is more sensitive in the presence of Ni²⁺ and UO₂²⁺ ions as compared with monovalent (Ag⁺), bivalent (Co²⁺), trivalent (Fe³⁺), and tetravalent (Sn⁴⁺) cations. The relative luminescent intensity (I₀/I) as a function of the concentrations of both Ni²⁺ and UO₂²⁺ shows a linear response in a broad concentration range (10^?7–10^?3 M). The limit of detection (LOD) for Ni²⁺ is 5.7 μg L^?1, which is lower than the allowable concentration limit (0.02 mg L^?1) defined by the national environmental quality standard of surface water GB 3838. The LOD for UO₂²⁺ is 0.02 μg L^?1, far below the World Health Organization maximum standards for potable water (30 μg L^?1). Therefore, Tb@UiO-66-(COOH)₂ enables the detection of these ions with high sensitivity. Notably, the optical response measured at low concentrations of Ni²⁺ and UO₂²⁺ is not affected even in the presence of interfering metallic ions. These results demonstrate for the first time that Tb@UiO-66-(COOH)₂ is a versatile multi-hazard sensor for the detection of non-radioactive and radioactive elements. It also opens opportunities for the selective adsorption and extraction of UO₂²⁺ due to the high-stability functionality of Tb@UiO-66-(COOH)₂.

We propose a generalized lattice model that enables prediction of the phase behavior and thermal stability of surface-confined metal–organic layers consisting of molecules with nitrogen-bearing functional groups (–CN, –Py, (NH)₂) of various sizes and transition metal atoms (copper and iron). The coordination energy per molecule is revealed to be a nearly linear function of the coordination number. In the case of three-fold coordination and higher, steric repulsions between the coordinated functional groups play an important role. The lattice model has been parametrized using DFT methods. The ground state phase diagrams have been calculated and verified by GCMC simulation at non-zero temperatures. An increase in the size of the functional group and/or decrease of the coordination capacity of the metal center leads to a greater phase diversity. There are linear metal–organic structures and metal–organic networks consisting of different coordination motifs. Otherwise, close-packed structures with high coordination motifs predominate. The relative thermal stability of the linear and 2D porous metal–organic structures is proportional to the average coordination number of the structure. Thermal destruction of the porous metal–organic structures occurs through breaking the coordination bonds and compacting the layer at the first stage forming the motifs with higher coordination numbers.

Four novel tri-substituted supramolecular materials (CTGC₁–CTGC₄) have been synthesized by converting cyclotriveratrylene to cyclotriguaiacyclene followed by esterification using 4-n-alkoxy derivatives of trans cinnamic acid (B₁–B₄). The synthesized materials were characterized by IR, ¹H-NMR, ¹³C-NMR, and MALDI-TOF analysis. The liquid crystalline properties of these cinnamate-based trimers were confirmed by polarized optical microscopy, differential scanning calorimetry, thermogravimetry and small and wide-angle X-ray scattering analysis. These compounds displayed an enantiotropic type columnar hexagonal (Col_h) phase with broad thermal stability. The higher alkoxy tail substituted mesogens (CTGC₃ and CTGC₄) with decyloxy and tetradecyloxy groups stabilized the mesophase at 32.0 °C and 26.0 °C, respectively. The synthesized CTG-linked trans-cinnamic acid trimers with alkoxy side groups exhibited self-assembly, which makes them good candidates for device applications. The current–voltage relationship indicates the ohmic-type behavior for the pristine and 100 °C annealed films while 200 °C films showed deviation. The optical properties indicate the high transmittance of 200 °C annealed films in visible and near IR regions. As wide optical energy band gaps of 2.93 eV, 2.87 eV and 3.45 eV were observed for CTGC₃ thin films, they could be utilized as optical window in second and transport layers in third generation solar cells.

The mineralization of TiO₂ has been previously investigated by controlling the morphology and crystal phase of TiO₂ using several organic templates, but the relationship between the molecular structure of the template and the functionality of the mineralized TiO₂ has not been reported. In this study, we investigated the influence and photodegradation activity of the TiO₂ mineralized by different functional groups on the peptide template surface (i.e., Ac-(Val-Lys-Val-Lys-Val-Glu)₃-CONH₂: KE, Ac-(Val-Lys-Val-Lys-Val-Ser)₃-CONH₂: KS, and Ac-(Val-Lys-Val-Lys-Val-Tyr)₃-CONH₂: KY). The KE–TiO₂ and KS–TiO₂ hybrids exhibited absorption only in the UV region (<380 nm), whereas the KY–TiO₂ hybrid absorbed in a wider wavelength region that stretched into the visible spectrum (<500 nm). In addition, the KS–TiO₂ hybrid showed a higher self-photosensitized degradation activity than the other systems owing to an efficient separation between electrons and holes, whereas the KY–TiO₂ hybrid showed not only a reduction in self-photosensitized degradation activity due to the recombination between the methylene blue⁺˙ radical cation (MB⁺˙) and the injected electron, but also an increase in photocatalytic activity under UV or visible light irradiation. Our findings show that biomineralizing TiO₂ presents an excellent and highly attractive approach to further functionalizing and optimizing TiO₂via an inexpensive and facile process, which will find use in all research fields that utilize TiO₂ for such purposes.