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Cellulose-based reduced graphene oxide materials (r-nGO) were fabricated and anchored onto polyvinyl alcohol stabilized gold nanoparticles. Their potential in applications in the electrocatalytic r ...

Cellulose-based materials are very attractive for emerging bioeconomy as they are renewable, inexpensive, and environmentally friendly. Cellulose beads are spherical and porous and can be highly engineered to be used as catalyst support material. This type of inorganic catalysts is cost-effective and suitable for multiple re-usage and has been rarely explored in cellulose reaction research. In this work, NiFe-layered double hydroxide (LDH) was tailor-made in situ on anionic cellulose beads to form a hybrid, supported photocatalyst for the first time. The hybrid beads were prepared in a size larger than the pulp fibers in order to make the catalysis reaction heterogeneous in nature. Hydrophilic pulp fibers were converted into hydrophobic pulp by photocatalytic topochemical grafting of ethyl acrylate using the LDH-cellulose bead catalyst. The approach identified for the modification of the pulp fibers is the "hydrogen abstraction-UV photografting" because the low-energy, UV radiation-induced grafting offers advantages, such as a reduced degradation of the backbone polymer and a control over the grafting reaction. After grafting, the pulp fibers showed increased water repellency and unaltered thermal stability, indicating the hydrophobic, plasticizing nature of the pulp, which in turn accounts for its thermoformable behavior. These acrylated pulp fibers can be further designed/customized for waterproof or oil absorption applications. ispartof: ACS Omega vol:4 issue:1 pages:320-330 ispartof: location:United States status: published

Bio-based resources are of high scientific importance these days due to their abundance, renewability, environment compatibility, recyclability, and many more aspects of sustainable material production and its consumption. Cellulose, the naturally occurring plant polymer has been a widely worked out substrate material for value addition as their supply from the forest products industry and agricultural wastes is huge and inexpensive. Cellulose is a fascinating polymer, with the repeating units of monosaccharide molecules containing secondary and tertiary –OH functional groups. These –OH groups are the primary target locations to modify cellulose chemically or physically. Topochemical engineering is a method of directed assembly or directed disassembly of functional materials. Directed assembly and disassembly are controlled via the design of intermolecular interactions in a topological space. This chapter covers recent advances in topochemical engineering of cellulose-based functional materials with the emphasis on valorization methods, chemistry, composition, and applications for the readers of sustainable biomaterials chemistry.

Topochemical engineering is a method of designing the fractionation (disassembly) and fabrication (assembly) of highly engineered functional materials using a combination of molecular and supramolecular techniques. Cellulose is one of the naturally occurring biopolymers, currently considered to be an important raw material for the design and development of sustainable products and processes. This feature article deals with new insights into how cellulose can be processed and functionalized using topochemical engineering in order to create functional fibers, enhance biopolymer dissolution in water-based solvents, and control the shaping of porous materials. Subsequently, topochemical engineering of cellulose offers a variety of morphological structures such as highly engineered fibers, functional cellulose beads, and reactive powders that find relevant applications in pulp bleaching, enzyme and antimicrobial drug carriers, ion exchange resins, photoluminescent materials, waterproof materials, fluorescent materials, flame retardants, and template materials for inorganic synthesis. The topochemical engineering of biopolymers and biohybrids is an exciting and emerging area of research that can boost the design of new bioproducts with novel functionalities and technological advancements for biobased industries. ispartof: LANGMUIR vol:34 issue:34 pages:9857-9878 ispartof: location:United States status: published

Technical composite materials derived from renewable sources are always of high importance due to cost-effectiveness and environmental concern. Cellulose, a renewable biopolymer stays constantly at the high realm in terms of valorization for functional materials, chemicals and other raw-materials. Cellulose based moisture-repellent materials have challenged the chemists in recent decade as the inherent hydrophilic nature of cellulose should be overcome by chemical modification or hydrophobic insulation. In the present study, cellulose is hydrophobized by eco-friendly stearic acid (SA) through inorganic linker/interface/sandwich material namely layered double hydroxides (LDH) for the first time as the layers have affinity to both cellulose and stearic acid at molecular level. The novel idea of utilizing the charge centres on LDH has been effectively materialized to make conjugation with hydrophobic SA and hydrophilic cellulose simultaneously. This produces an entirely new kind of hybrid material which offers not only hydrophobicity but super-hydrophobicity to cellulose network. This novel SA-LDH-CEL interfaced composite material surpasses all other materials that have been reported in the literature in terms of its water-repellency which is a mandatory requirement for water-proof packaging, thin films, paper, sorbent and sanitary materials.

Size & shape controlled synthesis of metal nanoparticles are of high importance in catalysis. Colloidal techniques offer fine tunings in synthesis process as it involve multiple steps and reaction parameters. An efficient way of producing morphology controlled palladium nanostructures viz. palladium nanocubes (Pd-nc), palladium nanoicosahedrons (Pd-nico) supported on reduced graphene oxide (rGO) and its application in electro-catalysis is reported here. These Pd nano-shapes were achieved via sequential chemical reduction of Pd metal precursor and graphene oxide in the presence of reductant, ethylene glycol (EG) and stabilizer (capping agent), polyvinylpyrrolidone (PVP). Potassium bromide (KBr) and ascorbic acid (AA) were used as structure directing and secondary reducing agents respectively, to tune the geometry of Pd nanoparticles (Pd NPs). The preparation steps were optimized to yield cube shaped Pd nanoparticles (Pd-nc) with mean diameter of 4 nm in the presence of KBr/AA; while in their absence, icosahedron shaped Pd nanoparticles (Pd-nico) with mean diameter of 3.1 nm were formed and then homogeneously distributed over rGO sheets as evidenced by SEM-EDX and TEM. Further, Pd-nc/rGO and Pd-nico/rGO hybrid composite materials were used to investigate the electrochemical oxidation of oxalic acid (OA) in acidic medium. The results reveal that, these optimal size ranged nanostructures exhibit enhanced electro-catalytic activity when compared to bare glassy carbon electrode (GCE), towards OA oxidation. Among the two, Pd-nico/rGO showed enhanced activity than Pd-nc/rGO. The activity difference was justified based on the particle size distribution and no of surface exposed sites. The synthesis approach provides a versatile route for morphology (shape and size) controlled synthesis of metal nanostructures immobilized on support materials aiming towards fabrication of low cost composites in electro-catalysis and potential sensor applications.

The use of precious metals in heterogeneous catalysis relies on the preparation of small nanoparticles that are stable under reaction conditions. To date, most conventional routes used to prepare noble metal nanoparticles have drawbacks related to surface contamination, particle agglomeration, and reproducibility restraints. We have prepared titania-supported palladium (Pd) and platinum (Pt) catalysts using a simplified vapor deposition technique termed chemical vapor impregnation (CVI) that can be performed in any standard chemical laboratory. These materials, composed of nanoparticles typically below 3 nm in size, show remarkable activity under mild conditions for oxidation and hydrogenation reactions of industrial importance. We demonstrate the preparation of bimetallic Pd-Pt homogeneous alloy nanoparticles by this new CVI method, which show synergistic effects in toluene oxidation. The versatility of our CVI methodology to be able to tailor the composition and morphology of supported nanoparticles in an easily accessible and scalable manner is further demonstrated by the synthesis of Pdshell-Aucore nanoparticles using CVI deposition of Pd onto preformed Au nanoparticles supported on titania (prepared by sol immobilization) in addition to the presence of monometallic Au and Pd nanoparticles. © 2013 American Chemical Society.

The utilisation of gold-palladium nanoparticles either in the form of colloids or supported nanoparticles has received enormous attention in recent years. These materials are very effective for the transformation of organic compounds to highly useful chemical products. The catalytic materials are usually prepared using deposition-precipitation and impregnation techniques, but recently significant attention has been focused on the use of colloidal methods. Here we compare and contrast the preparation and catalytic reactivity of Au-Pd supported nanoparticles synthesised by deposition-precipitation and colloidal methods. The catalyst materials have been evaluated for three different reactions, namely, the oxidation of benzyl alcohol, the direct synthesis of hydrogen peroxide and the oxidation of carbon monoxide. In addition, we have focused our attention on the pre-treatment temperature and the improvement of the deposition-precipitation method by using urea and sodium borohydride for the preparation of highly active Au-Pd supported nanoparticles. © 2010 Elsevier B.V. All rights reserved.

We report the preparation of Au-Pd nanocrystalline catalysts supported on activated carbon prepared via a sol-immobilization technique and explore their use for the direct synthesis of hydrogen peroxide and the oxidation of benzyl alcohol. In particular, we examine the synthesis of a systematic set of Au-Pd colloidal nanoparticles having a range of Au/Pd ratios. The catalysts have been structurally characterized using a combination of UV-visible spectroscopy, transmission electron microscopy, STEM HAADF/XEDS, and X-ray photoelectron spectroscopy. The Au-Pd nanoparticles are found in the majority of cases to be homogeneous alloys, although some variation is observed in the AuPd composition at high Pd/Au ratios. The optimum performance for the synthesis of hydrogen peroxide is observed for a catalyst having a Au/Pd 1:2 molar ratio. However, the competing hydrogenation reaction of hydrogen peroxide increases with increasing Pd content, although Pd alone is less effective than when Au is also present. Investigation of the oxidation of benzyl alcohol using these materials also shows that the optimum selective oxidation to the aldehyde occurs for the Au/Pd 1:2 molar ratio catalyst. These measured activity trends are discussed in terms of the structure and composition of the supported Au-Pd nanoparticles. © 2010 American Chemical Society.

The selectivity of photocatalytic phenol production from the direct oxidation of benzene can be enhanced by fine adjustment of the morphology and composition of Au-Pd metal nanoparticles supported on titanium dioxide thereby suppressing the decomposition of benzene and evolution of phenolic compounds.

Metal nanoparticles that comprise a few hundred to several thousand atoms have many applications in areas such as photonics, sensing, medicine and catalysis. Colloidal methods have proven particularly suitable for producing small nanoparticles with controlled morphologies and excellent catalytic properties. Ligands are necessary to stabilize nanoparticles during synthesis, but once the particles have been deposited on a substrate the presence of the ligands is detrimental for catalytic activity. Previous methods for ligand removal have typically involved thermal and oxidative treatments, which can affect the size or morphology of the particles, in turn altering their catalytic activity. Here, we report a procedure to effectively remove the ligands without affecting particle morphology, which enhances the surface exposure of the nanoparticles and their catalytic activity over a range of reactions. This may lead to developments of nanoparticles prepared by colloidal methods for applications in fields such as environmental protection and energy production. © 2011 Macmillan Publishers Limited. All rights reserved.