Bio-inspired fabrication of chitosan/PEO/TiCT 2D MXene nanosheets supported palladium composite nanofiber catalysts via electrospinning.

In this study, novel chitosan/polyethylene oxide/TiCT 2D MXene nanosheets (CS/PEO/TiCT) nanofibers were successfully prepared by a continuous electrospinning process. During the electrospinning process, induced by the syringe tip capillary effects and electric field force, the TiCT nanosheets were aligned along the direction of the nanofiber formation to occur a highly oriented structure. This well-ordered arrangement of the inorganic TiCT nanosheets within the organic polymer matrix nanofiber was similar with nacre-like 'brick-and-motar' structure to some extent, resulting in a marked increase in thermal stability and mechanical properties of the resultant CS/PEO/TiCT nanofiber.

Novel Divinyl-Flanked Diketopyrrolopyrrole Polymer, Based on a Dimerization Strategy for High-Performance Organic Field-Effect Transistors.

In this communication, we report a novel acceptor structural unit, TVDPP, that can be distinguished from classical materials based on TDPP structures. By designing a synthetic route via retrosynthetic analysis, we successfully prepared this monomer and further prepared polymer P2TVDPP with high yield using a Stille-coupling polymerization reaction. The polymer showed several expected properties, such as high molecular weight, thermal stability, full planarity, small π-π stacking distance, smooth interface, and so on.

Preparation of Dye Semiconductors via Coupling Polymerization Catalyzed by Two Catalysts and Application to Transistor.

Organic dye semiconductors have received increasing attention as the next generation of semiconductors, and one of their potential applications is as a core component of organic transistors. In this study, two novel diketopyrrolopyrrole (DPP) dye core-based materials were designed and separately prepared using Stille coupling reactions under different palladium catalyst conditions. The molecular weights and elemental compositions were tested to demonstrate that both catalysts could be used to successfully prepare materials of this structure, with the main differences being the weight-average molecular weight and the dispersion index.

Preparation of Novel Organic Polymer Semiconductor and Its Properties in Transistors through Collaborative Theoretical and Experimental Approaches.

Conjugated polymer semiconductors based on donor-acceptor structures are commonly employed as core materials for optoelectronic devices in the field of organic electronics. In this study, we designed and synthesized a novel acceptor unit thiophene-vinyl-diketopyrrolopyrrole, named TVDPP, based on a four-step organic synthesis procedure. Stille coupling reactions were applied with high yields of polymerization of TVDPP with fluorinated thiophene (FT) monomer.

Modification of Pillared Intercalated Montmorillonite Clay as Heterogeneous Pd Catalyst Supports.

Montmorillonite clay was modified by pillaring with AlMn oxides in different Al/Mn ratios and intercalation of two kinds of N-containing polymers (i.e., chitosan (CS) and polyvinyl pyrrolidinone (PVP)) chains.

TiO-Modified Montmorillonite-Supported Porous Carbon-Immobilized Pd Species Nanocomposite as an Efficient Catalyst for Sonogashira Reactions.

In this study, a combination of the porous carbon (PCN), montmorillonite (MMT), and TiO was synthesized into a composite immobilized Pd metal catalyst (TiO-MMT/PCN@Pd) with effective synergism improvements in catalytic performance. The successful TiO-pillaring modification for MMT, derivation of carbon from the biopolymer of chitosan, and immobilization of Pd species for the prepared TiO-MMT/PCN@Pd nanocomposites were confirmed using a combined characterization with X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), N adsorption-desorption isotherms, high-resolution transition electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. It was shown that the combination of PCN, MMT, and TiO as a composite support for the stabilization of the Pd catalysts could synergistically improve the adsorption and catalytic properties.

Novel bio-inspired three-dimensional nanocomposites based on montmorillonite and chitosan.

In this study, inspired by nacre-like structural natural shells, novel three-dimensional (3D) nanocomposites based on natural nanoplatelets of montmorillonite (MMT) and polysaccharide of chitosan (CS) were prepared with solution intercalation and self-assembly process. The CS-intercalated-MMT nanoplatelets units acted as "bricks" and CS molecules acted as "mortar", arranging in fairly well-ordered layered structure. With addition of glutaraldehyde (GA) and Pd cations, synergistic toughening and strengthening effects of covalent and ionic bonds could be achieved.

Chitosan modified Ti-PILC supported PdO catalysts for coupling reactions of aryl halides with terminal alkynes.

Biopolymer of chitosan (CS) and titanium pillared clays (Ti-PILCs) have been combined in a hybrid as advanced supports for immobilization of PdO species to prepare novel PdO@Ti-PILC/CS nano-composite catalysts. The Ti-PILC materials showed high specific surface areas and abundant meso-porous structure with many irregular pore channels caused by collapses of layered structure of clay during Ti pillaring process. Both CS chains and sub-nano sized PdO particles were successfully incorporated into the pore channels of Ti-PILC, resulting in a decrease in both the specific surface areas and uniform distribution of pore size.

Preparation of porous chitosan/reduced graphene oxide microspheres supported Pd nanoparticles catalysts for Heck coupling reactions.

Novel porous chitosan/reduced graphene oxide microspheres supported Pd nanoparticles catalysts (Pd@CS/RGO) were prepared by a combination of silica nanoparticles etching and freeze-drying treatments of CS/RGO/silica/PdCl composite microspheres. The microstructure of the Pd@CS/RGO microspheres catalysts have been investigated by X-ray photo electron spectroscopy (XPS), Raman spectroscopy, high resolution transmission electron microscopy (HR-TEM), thermo-gravimetric analysis (TGA), and X-ray diffraction (XRD), etc. The results revealed that: the novel catalysts showed open porous structure; CS had good miscibility with RGO nanosheets; Pd nanoparticles were well incorporated within CS/RGO matrix; the thermal stabilities of the catalysts were improved significantly over CS.

Modification of Montmorillonite with Polyethylene Oxide and Its Use as Support for Pd Nanoparticle Catalysts.

In this study, montmorillonite (MMT) was modified by intercalating polyethylene oxide (PEO) macromolecules between the interlayer spaces in an MMT-water suspension system. X-ray diffraction results revealed that the galleries of MMT were expanded significantly after intercalation of different loading of PEO. MMT/PEO 80/20 composite was chosen as the support platform for immobilization of Pd species in preparing novel heterogeneous catalysts.

Heterogeneous Catalytic Composites from Palladium Nanoparticles in Montmorillonite Intercalated with Poly (Vinyl Pyrrolidone) Chains.

In this study, poly (vinyl pyrrolidone) (PVP) chains intercalated montmorillonite (MMT) matrices has been demonstrated as an excellent scaffolding material for the immobilization of palladium (Pd) nanoparticles to prepare efficient heterogeneous catalysts for Heck reactions. Multiple layers (up to four) of PVP chains can intercalate the interlayer space of the MMT, resulting in an increase therein from 1.25 to 3.

One-pot carbonization of chitosan/P123/PdCl blend hydrogel membranes to N-doped carbon supported Pd catalytic composites for Ullmann reactions.

Novel porous nitrogen-doped carbon supported Pd (Pd@N-C) catalytic composites were prepared by one-pot thermal carbonization of chitosan/poly(ethylene glycol)‑block‑poly(propylene glycol)‑block‑poly(ethylene glycol)/PdCl (CS/P123/PdCl) blend hydrogel membranes at different temperature in N atmosphere. The porous structure of the Pd@N-C catalytic composite was governed by both the addition of P123 and the carbonization temperature. At highest carbonization temperature of 900 °C, the prepared Pd@N-C catalytic composite from CS/P123/PdCl blend membrane showed the highest specific area (S) of 293.

Microstructure and catalytic performances of chitosan intercalated montmorillonite supported palladium (0) and copper (II) catalysts for Sonogashira reactions.

In this study, an efficient heterogeneous catalytic material including Pd nanoparticles and Cu cations supported on montmorillonite/chitosan (MMT/CS) composite was prepared by solution intercalation and complexion methods. The valence states of Pd (both Pd(0) and Pd(II) coexisting) and Cu (mainly Cu(II)) of the Pd/Cu@MMT/CS catalyst were confirmed by the X-ray photoelectron spectroscopy (XPS) characterization. The d spacing was enlarged from 1.

Insightful understanding of the correlations of the microstructure and catalytic performances of Pd@chitosan membrane catalysts studied by positron annihilation spectroscopy.

In this study, the catalytic performances of palladium supported on chitosan (Pd@CS) membrane heterogeneous catalysts have been studied from the aspects of free volume by positron annihilation lifetime spectroscopy (PALS). The results showed that the variation in free volume hole size of the Pd@CS membrane catalyst was closely associated with microstructure evolutions, such as increase of Pd content, valence transition of Pd by reduction treatment, solvent swelling, physical aging during catalyst recycling, and so on. The PALS results showed that both the mean free volume hole size of the Pd@CS membrane in the dry or swollen state (analyzed by the LT program) and its distribution (analyzed by the MELT program) are smaller than the molecule size of the reactants and products in the catalysis reaction.

Co-immobilization of Pd and Zn nanoparticles in chitosan/silica membranes for efficient, recyclable catalysts used in ullmann reaction.

In this study, an efficient heterogeneous catalyst including palladium (Pd) and zinc (Zn) nanoparticles supported on chitosan/silica (CS/SiO) composite membrane is synthesized using partially etching of SiO technique. N sorption isotherm results shows that the prepared Pd-Zn@CS/SiO (1/1) porous membrane had a BET surface area of 26.50m/g.

Probing sub-nano level molecular packing and correlated positron annihilation characteristics of ionic cross-linked chitosan membranes using positron annihilation spectroscopy.

Chitosan, CS, cross-linked with bivalent palladium has shown enhanced mechanical and thermal properties depending on the transformation of the structure at a microscopic scale. In the present study, CS directly cross-linked by palladium cation membranes (CS-cr-PM) was prepared through a solution-casting method. Mobility of chitosan chains were greatly reduced after crosslinking, making a great reduction in the swelling ratio studied by a water-swelling degree measurement, which led to an improvement in molecular chain rigidity.

Encaging Palladium Nanoparticles in Chitosan Modified Montmorillonite for Efficient, Recyclable Catalysts.

Metal nanoparticles, once supported by a suitable scaffolding material, can be used as highly efficient heterogeneous catalysts for numerous organic reactions. The challenge, though, is to mitigate the continuous loss of metals from the supporting materials as reactions proceed, so that the catalysts can be recycled multiple times. Herein, we combine the excellent chelating property of chitosan (CS) and remarkable stability of montmorillonite (MMT) into a composite material to support metal catalysts such as palladium (Pd).

N-doped mesoporous carbons supported palladium catalysts prepared from chitosan/silica/palladium gel beads.

In this study, a heterogeneous catalyst including palladium nanoparticles supported on nitrogen-doped mesoporous carbon (Pd@N-C) is synthesized from palladium salts as palladium precursor, colloidal silica as template, and chitosan as carbon source. N2 sorption isotherm results show that the prepared Pd@N-C had a high BET surface area (640m(2)g(-1)) with large porosity. The prepared Pd@N-C is high nitrogen-rich as characterized with element analysis.

Novel macroporous palladium cation crosslinked chitosan membranes for heterogeneous catalysis application.

A novel palladium supported on chitosan porous membrane heterogeneous catalyst has been prepared by freeze-drying of Pd(2+)-crosslinked chitosan gel solution. The prepared membrane catalyst has three-dimensional porous structure (porosity: >70%). The crosslinking effects of Pd(2+) to chitosan were good for the improvement of the mechanical properties and thermal stabilities.

Chitosan microspheres supported palladium heterogeneous catalysts modified with pearl shell powders.

Significant enhancement of the catalytic stability and activity was obtained for the heterogeneous palladium catalyst supported on the shell powders-reinforced chitosan microspheres. For example, over 90% cross-coupling yields were achieved using as low as 0.05 mol% palladium catalyst loading for the Heck-type reaction of iodobenzene with n-butyl acrylate.

Microstructure-stability relations studies of porous chitosan microspheres supported palladium catalysts.

In this study, polyethylene glycol (PEG) with different molecular weight, polyvinyl pyrrolidone (PVP), and polyvinyl alcohol (PVA), are chosen as porogens for preparing chitosan base porous microsphere supported palladium catalyst for coupling reactions. The pore structure of the microspheres was controlled by the compatibility of chitosan and counterpart polymers. The prepared porous chitosan microspheres supported palladium heterogeneous catalysts have been evaluated using the well-established Ullmann reductive homocoupling and the Heck cross-coupling reactions.

Palladium-catalyzed reductive homocoupling of aromatic halides and oxidation of alcohols.

Palladium-catalyzed reductive homocoupling of aromatic halides can be performed in alcohol solutions without any auxiliary reducing reagents. Pd(dppf)Cl(2) [dppf = 1,1'-bis(diphenylphosphino)ferrocene] has been shown as the most effective catalyst among the palladium catalysts screened for the model reductive homocoupling of iodobenzene in alcoholic solutions. The reduction of iodobenzene is stoichiometrically coupled with the oxidation of solvent alcohol (3-pentanol).