Managing Excess Lead Iodide with Functionalized Oxo-Graphene Nanosheets for Stable Perovskite Solar Cells

Stability issues could prevent lead halide perovskite solar cells (PSCs) from commercialization despite it having a comparable power conversion efficiency (PCE) to silicon solar cells. Overcoming drawbacks affecting their long-term stability is gaining incremental importance. Excess lead iodide (PbI₂) causes perovskite degradation, although it aids in crystal growth and defect passivation. Herein, we synthesized functionalized oxo-graphene nanosheets (Dec-oxoG NSs) to effectively manage the excess PbI₂. Dec-oxoG NSs provide anchoring sites to bind the excess PbI₂ and passivate perovskite grain boundaries, thereby reducing charge recombination loss and significantly boosting the extraction of free electrons. The inclusion of Dec-oxoG NSs leads to a PCE of 23.7 % in inverted (p-i-n) PSCs. The devices retain 93.8 % of their initial efficiency after 1,000 hours of tracking at maximum power points under continuous one-sun illumination and exhibit high stability under thermal and ambient conditions.     

A versatile method for the hydrolysis of gem-dibromomethylarenes bearing carboxylate or boronate group into aldehydes

Hydrolysis of gem-dibromomethylarenes bearing carboxylate or boronate group to corresponding aldehydes without affecting the ester group was successfully accomplished in high yields by subjecting them to refluxing pyridine. Both aromatic and heteroaromatic substrates gave the corresponding aldehydes in good yields. This method was efficiently adapted for the large scale synthesis of 2d and 2f.     

Polydipyrrole- and polydicarbazole-nanorods as new nanosized supports for DNA hybridization

Novel functional polydipyrrole- and polydicarbazole nanorods have been AAO template-synthesized from COOH-dipyrrole/-dicarbazole monomers using Vapor Deposition and Liquid Phase Polymerizations (VDP and LPP). They were tested as insoluble supports for covalent DNA attachment and hybridization.     

Algebraic invariants of weighted oriented graphs

Journal of Algebraic Combinatorics - Let $$\mathcal {D}$$ be a weighted oriented graph and let $$I(\mathcal {D})$$ be its edge ideal in a polynomial ring R. We give the formula of...     

Activation of alkyl halides at the Cu0 surface in SARA ATRP: An assessment of reaction order and surface mechanisms

The external order in reagents for the activation of alkyl halides by Cu⁰ was investigated in supplemental activator and reducing agents (SARA) ATRP. Using methyl 2-bromopropionate (MBrP) or ethyl α-bromophenylacetate (EBPA) and tris(2-(dimethylamino)ethyl)amine (Me₆TREN) in DMSO and MeCN, it was determined that the rate of activation scaled with (S/V)^0.9 in both solvents. For MBrP, the rate was first order with respect to [MBrP]₀ until a saturation in the rate was observed around 33 and 110 mM in DMSO and MeCN, respectively. For EBPA, the reaction was also first order until a maximum rate was observed at 33 mM in DMSO, whereas an inverse order was observed for concentrations above 66 mM in MeCN. At saturated concentrations of MBrP, it was found that the rate increased linearly with respect to [Me₆TREN]₀ for all systems but became asymptotic with a maximum rate of 2 × 10⁻⁶ and 4 × 10⁻⁵ M s⁻¹ in DMSO and MeCN, respectively. Model polymerizations in the absence of ligand showed slow reaction rates, indicating the necessity for ligand. The results allow more accurate modeling and understanding of SARA ATRP under a large range of initiator concentrations. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 3048–3057     

3,5‐Bis{3‐[4‐(dimethylamino)phenyl]prop‐2‐enylidene}‐1‐methyl‐4‐piperidone and 3,5‐bis[3‐(4‐methoxyphenyl)prop‐2‐enylidene]‐1‐methyl‐4‐piperidone: potential biophotonic materials

The structures of the title compounds, C₂₈H₃₃N₃O, (I), and C₂₆H₂₇NO₃, (II), together with their two‐photon absorption properties and fluorescence activities are reported. Molecules of (II) reside on crystallographic mirror planes containing the piperidone C=O group and N‐methyl H atoms. Because of the conjugation between the donor and acceptor parts, the central heterocycle in both (I) and (II) exhibits a flattened boat conformation, with deviations of the N atom and the opposite C atom from the planar fragment. The dihedral angles between the coplanar heterocyclic atoms and terminal C₆ rings are less than 20° in both (I) and (II). In (I), the N‐methyl group of the ring occupies an equatorial position, but in (II) it is positioned in an axial site. In the crystal structure of (I), weak intermolecular C—H...π(arene) and C—H...O steric contacts link the molecules along the a axis. In the crystal structure of (II), molecules form stacks along the b axis.     

Regioselective synthesis of 2,8-disubstituted 4-aminopyrido[3,2-d]pyrimidine-6-carboxylic acid methyl ester compounds

We report herein the synthesis of 4-amino-2,8-dichloropyrido[3,2-d]pyrimidine derivatives 2 and their regioselective diversification through S(N)Ar and metal-catalyzed cross-coupling reactions. While amination of 2 took place selectively at C-2, the regioselectivity of thiol or thiolate addition depended on the reaction conditions. Selective C-8 addition was obtained in DMF with Hünig's base and C-2 addition in (i)PrOH. These C-2 or C-8 regioselective thiolations provided an opportunistic way to selectively activate either of the two positions toward the metal-catalyzed cross-coupling reaction. The chloride could be efficiently substituted by Suzuki-Miyaura reaction and the sulfanyl group by Liebeskind-Srogl cross-coupling reaction, demonstrating the orthogonality of both reactive centers. The development of regioselective conditions for these different transformations yielded the synthesis of 4-amino-2,6,8-trisubstituted pyrido[3,2-d]pyrimidine derivatives, with various substituents.     

A facile hydrothermal route to synthesize novel PbI2 nanorods

We report the synthesis of PbI₂ nanorods by reacting lead acetate with elemental iodine at room temperature by virtue of a wet chemical method at mild reactions. The diameters of the obtained PbI₂ nanorods are about 54 nm. The present technique may open a new doorway to one-dimensional nanosized rods from the same kind of materials with irregular shape or large size. X-ray powder diffraction (XRD), Fourier transform infrared analysis (FTIR), ultraviolet–visible–near infrared analysis (UV–vis–NIR), photoluminescence measurements (PL) and scanning electron microscopy (SEM) were used to characterize PbI₂ nanorods. The as obtained products were analyzed by X-ray powder diffraction, which confirms the formation of solid PbI₂ nanorods. From the UV–vis–NIR studies the band gap of PbI₂ nanorod was estimated. The various functional groups present in the PbI₂ nanorods were identified by FTIR analysis. Intense photoluminescence was also observed with some spectral tuning possibly giving a range of emission photon energies approximately spanning from 2.1 to 3.5 eV.