Single-crystal microplates of two-dimensional organic–inorganic lead halide layered perovskites for optoelectronics

Organic-inorganic hybrid perovskites attract considerable attention owing to their applications in high-efficiency solar cells and light emission.Compared with three-dimensional perovskites,two-dimensional (2D) layered hybrid perovskites have a higher exciton binding energy and potentially higher light-emission efficiency.The growth of high-quality crystalline 2D perovskites with a well-defined nanoscale morphology is desirable because they can be suitable building blocks for integrated optoelectronics and (nano)photonics.Herein,we report the facile solution growth of single-crystal microplates of 2D perovskites based on a 2-phenylethylammonium (C6H5CH2CH2NH3+,PEA) cation,(PEA)2PbX4 (X =Br,I),with a well-defined rectangular geometry and nanoscale thickness through a dissolution-recrystallization process.The crystal structures of (PEA)2PbX4 are first confirmed using single-crystal X-ray diffraction.A solution-phase transport-growth process is developed to grow microplates with a typical size of tens of micrometers and thickness of hundreds of nanometers on another clean substrate different from the substrate coated with lead-acetate precursor film.Surface-topography analysis suggests that the formation of the 2D microplates is likely driven by the wedding-cake growth mechanism.Through halide alloying,the photoluminescence emission of (PEA)2Pb(Br,I)4 perovskites with a narrow peak bandwidth is readily tuned from violet (～410 nm) to green (～530 nm).     

Acrylic blends based on polyaniline. Factorial design

Processable conducting materials for large-scale utilization were prepared by mechanical mixing of polyaniline (PANI) paste and commercially acrylic resin. Doped PANI with organic phosphorus acid was synthesized. These blends can be used for the production of semiconductive paints with good corrosion resistance. By mixing doped PANI with commercially acrylic acid (SMP 63 AZUR SA) hard semiconducting and low elastic films are obtain. The effect of four variables was simultaneously studied: PANI (concentration), stirring speed (ST), mixing time (MT), dispersing agent (DA). Due to the number of variables, a factorial-design was chosen in order to reduce the number of experiments required in order to obtain coatings with high hardness and elasticity and semiconductive behavior. The results indicated that the influences of control factors decrease in order: PANI (concentration), mixing time (MT), dispersing agent (DA) and stirring speed (ST). From the studied variables, the resistance is significantly influenced by the two control factors PANI and MT.     

Homomorphic Public-Key Cryptosystems and Encrypting Boolean Circuits

Given an arbitrary finite nontrivial group, we describe a probabilistic public-key cryptosystem in which the decryption function is chosen to be a suitable epimorphism from the free product of finite Abelian groups onto this finite group. It extends the quadratic residue cryptosystem (based on a homomorphism onto the group of two elements) due to Rabin – Goldwasser – Micali. The security of the cryptosystem relies on the intractability of factoring integers. As an immediate corollary of the main construction, we obtain a more direct proof (based on the Barrington technique) of Sander-Young-Yung result on an encrypted simulation of a boolean circuit of the logarithmic depth.     

Temperature derivative spectroscopy to monitor the autoxidation decay of cytochromes P450

Temperature derivative spectroscopy (TDS), a type of relaxation spectroscopy, is a powerful tool to study protein dynamics (Berendzen, J.; Braunstein, D. Proc. Natl. Acad. Sci. U. S. A. 1990, 87, 1). We developed the version of temperature derivative spectroscopy to monitor kinetics of autoxidation of cytochromes P450 and applied it to study the properties of the oxy-ferrous complex of a human membrane bound P450, CYP19A1 (aromatase), and that of a bacterial soluble P450, CYP101 when bound with their most common substrates, androstenedione (AD) and camphor, respectively. TDS extends the panel of methods that can be used to monitor heme protein kinetics, providing a rapid measurement technique and enabling measurement of the autoxidation rate over a wide range of temperatures, yielding the activation energy as well as absolute reaction rate in a single experiment.     

Impact of local versus global ligand density on cellular adhesion

α(v)β(3) integrin-mediated cell adhesion is crucially influenced by how far ligands are spaced apart. To evaluate the impact of local ligand density versus global ligand density of a given surface, we used synthetic micronanostructured cell environments with user-defined ligand spacing and patterns to investigate cellular adhesion. The development of stable focal adhesions, their number, and size as well as the cellular adhesion strength proved to be influenced by local more than global ligand density.     

Machine Learning‐Enabled Correlation and Modeling of Multimodal Response of Thin Film to Environment on Macro and Nanoscale Using “Lab‐on‐a‐Crystal”

To close the feedback loop between artificial intellegence‐controlled materials synthesis and characterization, material functionality must be rapidly tested. A platform for high‐throughput multifunctional materials characterization is developed using a quartz crystal microbalance with auxiliary in‐plane electrodes and a custom gas/vapor flow cell, enabling simultaneous scanning probe microscopy and electrical, optical, gravimetric, and viscoelastic characterization on the same film under controlled environment. The lab‐on‐a‐crystal in situ multifunctional output allows direct correlations between the gravimetric/viscoelastic, electrical, and optical responses of polymer film in response to environment. When multiple film properties are used to augment the training set for machine learning regression, prediction of material response to the environment improves by a factor of 13 when <5% of the total dataset is used for model training.     

Computational Study of Main Mechanisms for Gas-Phase Decomposition of 1,1- and 1,2-Dinitroethane

The gas-phase enthalpies of formation of 1,1- and 1,2-dinitroethane and corresponding radical products were calculated using G3B3, CBS-QB3 composite methods and DFT B3LYP level of theory with various basis sets. The enthalpies of the C–N, C–C bonds dissociation and activation enthalpies for HONO elimination were also calculated and compared with available experimental data. It was found that G3B3 calculations do provide a reasonable way to tackle the problem of the decomposition channels of 1,1- and 1,2-dinitroethane. Four main mechanisms for gas-phase decomposition of 1,1- and 1,2-dinitroethane were studied using G3B3 model chemistry. HONO elimination seems to be the most favorable mechanism for the decomposition of 1,2-dinitroethane. However, the difference in energies of the HONO elimination and C–N homolytic bond cleavage in 1,1-dinitroethane does not allow to favor any of these channels, especially at the working temperature. Gauche conformation of 1,2-dinitroethane is calculated to be the lowest-energy minimum.