Effect of thickness on the structural,optical and electrical properties of thermally evaporated PbI2 thin films

This work describes the physical properties of lead iodide (PbI₂) thin films with different thicknesses that were deposited on ultrasonically cleaned glass substrates using a thermal evaporation technique at 5×10^-6 torr. The initial material was purified by the zone refining technique under an atmosphere of argon gas. XRD analysis of the material demonstrates that the thin films were preferably oriented along the (001) direction. The size of the crystallites was calculated from the Scherer relation and found to be in the range of ～5–10 nm, with higher values being observed for increasing film thicknesses. The optical energy band gaps were evaluated and determined to belong to direct transitions. Because the band gap increased with decreasing film thickness, a systematic blue shift was observed. The surface morphologies of PbI₂ films exhibited a clear increase in grain size with increasing film thickness. The photoluminescence and dc conductivity of the thin films are also discussed.     

A facile route to flavone and neoflavone backbones via a regioselective palladium catalyzed oxidative Heck reaction

A straightforward and atom-economical base-free palladium-catalyzed regioselective direct arylation of coumarins and chromenones is devised. This protocol is compatible with a wide variety of electron-donating and -withdrawing substituents and allows construction of various biologically important flavone and neoflavone backbones.     

Consecutive iridium catalyzed C-C and C-H bond forming hydrogenations for the diastereo- and enantioselective synthesis of syn-3-fluoro-1-alcohols: C-H (2-fluoro)allylation of primary alcohols

Commercially available (2-fluoro)allyl chloride serves as an efficient allyl donor in highly enantioselective iridium catalyzed carbonyl (2-fluoro)allylations from the alcohol or aldehyde oxidation level via transfer hydrogenation. Diastereoselective Crabtree hydrogenation of the resulting homoallylic alcohols provides syn-3-fluoro-1-alcohols.     

(-)-Kunstleramide, a new antioxidant and cytotoxic dienamide from the bark of Beilschmiedia kunstleri gamble

A new dienamide, (2E,4E)-7-(3',4'-dimethoxyphenyl)-N-ethyl-6-(R)-hydroxyhepta- 2,4-dienamide, named (-)-kunstleramide (1), were isolated from the bark of Beilschmiedia kunstleri Gamble together with one neolignan: (+)-kunstlerone (2) and seven known alkaloids: (+)-nornuciferine (3), (-)-isocaryachine (4), (+)-cassythicine (5), (+)-laurotetanine (6), (+)-boldine (7), noratherosperminine (8), (+)-N-demethylphyllocaryptine (9). Their structures were established from spectroscopic techniques, most notably 1D- and 2D-NMR, UV, IR, OR, circular dichroism (CD) spectra and LCMS-IT-TOF. (-)-Kunstleramide (1) exhibited very poor dose-dependent inhibition of DPPH activity, with an IC?? value of 179.5 ± 4.4 μg/mL, but showed a moderate cytotoxic effect on MTT assays of A375, A549, HT-29, PC-3 and WRL-68 with EC?? values of 64.65, 44.74, 55.94, 73.87 and 70.95 μg/mL, respectively.     

Three-component reactions of isocyanides, dialkyl acetylenedicarboxylates, and trans-cinnamoyl chlorides for the synthesis of highly functionalized 2-vinyl furans

Abstract  

In this study, we present a convenient and efficient method for the synthesis of novel, highly substituted 2-vinyl furans using a three-component reaction. The zwitterions generated from the reaction of isocyanides and dialkyl acetylenedicarboxylates are reacted with trans-cinnamoyl chlorides to produce the desired products in good yields.     

A novel route to tetracyclic fused tetrazines and thiadiazines

The reaction between 3‐amino‐2,3‐dihydro‐7,9‐dimethyl‐2‐thioxo‐pyrido[3′,2′:4,5]thieno[3,2‐d]‐pyrimidin‐4(1H)‐one 4 or its 2‐methylthio derivative 5 with hydrazonoyl halides 6 in dioxane in the presence of triethylamine under reflux has followed heterocyclization reaction to yield pyrido[3″,2″:4′,5′]‐thieno[3′,2′:4,5]pyrimido[2,1‐c][1,2,4,5]tetrazin‐6(4H)‐ones 9 . On the other hand, reaction of compound 4 with hydrazonoyl halides 6 in sodium ethoxide at room temperature led to formation of hydrazonothioate compounds 10 . The latter on treatment with glacial acetic acid produced tetracyclic compounds, namely 2‐arylhydrazonopyrido[3″,2″:4′,5′]thieno [3′,2′:4,5]pyrimido[2,1‐b][1,3,4]thiadiazinones 11 . An alternative method was carried out to prove the structure of product 11 . The mechanism of the reaction under study was proposed and the products were screened for their biological activity.     

Superlattice formation in a binary mixture of block copolymer micelles

A binary solution mixture of distinct block copolymer micelles is found to adopt a superlattice. The larger micelles, formed from polystyrene-polyisoprene diblocks, have a nominal radius of 29 nm; the smaller micelles, formed from polystyrene-polydimethylsiloxane diblocks, have a nominal radius of 16 nm. The superlattice unit cell dimension is 156 nm and is assigned to space group Fm3c; it corresponds to the AB13 structure. As these diblocks are uncharged, the driving force for superlattice formation is primarily free volume entropy, as in sterically stabilized colloidal hard spheres.     

Pseudo almost automorphic solutions of fractional order neutral differential equation

In this paper we discuss the pseudo almost automorphic solution of a fractional order neutral differential equation in a Banach space X. The results are established using the Krasnoselskii’s fixed point theorem.     

Another homogeneous q-difference operator

In this paper we show the equivalence between Goldman-Rota q-binomial identity and its inverse. We may specialize the value of the parameters in the generating functions of Rogers-Szegö polynomials to obtain some classical results such as Euler identities and the relation between classical and homogeneous Rogers-Szegö polynomials. We give a new formula for the homogeneous Rogers-Szegö polynomials h_n(x,y|q). We introduce a q-difference operator θ_xy on functions in two variables which turn out to be suitable for dealing with the homogeneous form of the q-binomial identity. By using this operator, we got the identity obtained by Chen et al. [W.Y.C. Chen, A.M. Fu, B. Zhang, The homogeneous q-difference operator, Advances in Applied Mathematics 31 (2003) 659-668, Eq. (2.10)] which they used it to derive many important identities. We also obtain the q-Leibniz formula for this operator. Finally, we introduce a new polynomials s_n(x,y;b|q) and derive their generating function by using the new homogeneous q-shift operator L(bθ_xy).     

Some periodic point results in generalized metric spaces

We prove some fixed point and periodic point theorems for a map in generalized metric spaces. An example is provided to support our result. The results presented in this paper generalize several well known comparable results in the literature.