The sub-band gap absorption in the ferroelectric lead-free hybrid perovskite.

Aptamers, which can be screened via systematic evolution of ligands by exponential enrichment (SELEX), are superior ligands for molecular recognition due to their high selectivity and affinity. The interest in the use of aptamers as ligands for targeted drug delivery has been increasing due to their unique advantages. Based on their different compositions and preparation methods, aptamer-functionalized targeted drug delivery systems can be divided into two main categories: aptamer-small molecule conjugated systems and aptamer-nanomaterial conjugated systems. In this review, we not only summarize recent progress in aptamer selection and the application of aptamers in these targeted drug delivery systems but also discuss the advantages, challenges and new perspectives associated with these delivery systems.

Ab initio simulations combined with the Berry phase method are employed to investigate ferroelectric polarization of tetragonal CsPbBr3 crystals by applying hydrostatic pressure varying from 0 to 19 GPa; we find that the object research belongs to the P4mm space group. The calculated results show that the materials undergo a paraelectric-ferroelectric phase transition when the pressure increases to a critical value 15 GPa. The polarization is strongly enhanced and attains a high value of about 23 μC cm-2, owing to the increase in the ionic and electric contributions to the polarization under compressive strain. We present a detailed theoretical investigation to analyze the origin of polarization. The ionic polarization is mainly ascribed to the central displacements of Pb2+ cations and Br- anions induced by a highly distorted octahedral PbBr6- framework. Electronic structure calculations suggest that asymmetric hopping p orbital electrons of Br(3) ions are responsible for the enhancement in electric polarization. These discoveries suggest that tetragonal CsPbBr3 has significant potential in future ferroelectric applications, and this can broaden the application field from optoelectronics to ferroelectrics.

Despite great efforts devoted to the unusual optoelectronic properties for the bulk inorganic halide perovskites, overcoming the surface effects and bringing about selective growth in the specified surface termination are still a challenge. In this paper, we investigate the electronic structures, effective masses, carrier mobility, and optical properties of γ-CsSnI 3 with different terminations by employing density functional theory calculations. The calculated results show that the range of values of hole mobility is from 370.50 to 584.39 cm 2 /V s. Our results are close to the experimental data 400 cm 2 /V s. Moreover, we further predicted that the perfect CsI termination may exhibit better photovoltaic characteristics than the SnI 2 termination. On the basis of the stability of different surfaces and surface vacancies, an appropriate condition was obtained to suppress the I vacancies and promote the growth of perfect CsI-termination surface. This work also indicates that the electronic and optical properties of inorganic halide perovskites are tuned by selecting the proper surface, which is an important technique in the design of other optoelectronic devices.

In recent years, two-dimensional (2D) organic–inorganic perovskites have been attracting considerable attention because of their unique performance and enhanced stability for photovoltaic solar cells or photoluminescent devices.

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The electronic properties of an MoS2 and graphene heterostructure are investigated by density functional calculations.

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