Formation and microscopic investigation of iron oxide aligned nanowires into polymeric nanocomposite films

We present a microscopic investigation of nanocomposite films of iron oxide (g-Fe2O3) magnetic nanowires (NWs) aligned into polymers, formed upon evaporation of solutions of acrylate polymer/magnetic nanoparticles under magnetic field (MF). The field causes the assembly of the g-Fe2O3 nanoparticles along the direction of the MF lines, resulting in magnetic NWs embedded throughout the entire volume of the polymer film. The scanning electron microscopy and the trans- mission electron microscopy studies show that the cylindrical-shaped NWs have � 15-lm average length and are isotropically distributed throughout the film. The study with the MF microscopy tech- nique not only proves that the composed NWs are magnetic but also makes possible the magnetic study of each individual NW in a nondestructive way. In this way it becomes possible for the localized study of the magnetic properties alteration after the binding of various molecules onto individual NWs, opening up the way of using these films in sensor devices applied in various fields ranging from biology to environmental purposes. Microsc. Res. Tech. 73:952-958, 2010. V C 2010 Wiley-Liss, Inc

Biowaste-Derived Carbonized Bone for Solar Steam Generation and Seawater Desalination

AbstractInterfacial solar steam generation is an emerging strategy to improve the global freshwater supply. Herein, for the first time, a plausible alternative based on bone waste is presented for low‐cost solar steam generation and seawater desalination. This is accomplished via the exploration of the appropriate carbonization conditions for the successful bone transformation into a porous carbon‐based photothermal material. The carbonized bone (CB) not only is composed of inherent interlinked mesoporous microchannels for efficient water transportation but also displays broadband light absorption, photothermal conversion, and reduced vaporization enthalpy due to its special interactions with water. The as‐prepared CB shows an apparent evaporation rate of 1.82 kg m−2 h−1 under one‐sun illumination, attributed not only to its interaction with the sunlight but also to its performance in the dark field, and a solar‐to‐vapor conversion efficiency of 80%. Furthermore, CB desalinates water with an efficiency of 99.99%. Such performance combined with its wide availability, facile fabrication, and stability makes this biowaste‐based porous material a promising system for the production of freshwater. In this way, a valuable alternative for the valorization of bone‐based food‐waste is offered, paving the way to new routes for the management of such, continuously growing, food‐waste products

Nanochains Formation of Superparamagnetic Nanoparticles

We present simulations on the aggregation of nanometer sized polydispersed superparamagnetic particles under the application of an external magnetic field. We make use of a Monte Carlo method, using a cluster-moving approach, as previously used in literature for ferrofluids. van der Waals attraction and magnetic anisotropy are taken into account in the simulations. Chains elongated in the field direction are formed. The results are in good agreement with recent experimental results on nanochains made of iron oxide nanoparticles into polymer matrix, obtained with the application of a magnetic field during film deposition. The magnetization anisotropy of the nanocomposite film under dc magnetic field can be predicted within this simple model

Mechanical reinforcement and water repellency induced to cellulose sheets by a polymer treatment

The present study reports a simple method to control the mechanical and surface properties of cellulose fiber networks and to protect them from humidity, without altering their initial morphology. This is achieved by dip coating the fiber networks in solutions containing different amounts of ethyl cyanoacrylate monomer (ECA). Under ambient humidity and due to the presence of the -OH groups of the cellulose, the ECA polymerizes around each individual cellulosic fiber forming a thin poly(ethyl cyanoacrylate) (PECA) shell. PECA was found to interact with the cellulose surface via hydrogen bonding as evidenced by Fourier transform infrared spectroscopy and thermogravimetric analysis measurements. The detailed surface characterization reveals that only 3.5 wt% of ECA in solution is sufficient to form compact PECA cladding around every cellulose fiber. After the proposed treatment the cellulose sheets become hydrophobic, well protected from the environmental humidity and with increased Young's modulus

Enhanced electrical conductivity of poly(methyl methacrylate) filled with graphene and in situ synthesized gold nanoparticles

The improvement of the electrical conductivity of polymers by incorporating graphene has been intensively studied in recent years. To further boost the electrical conductivity, blending third-party additives into the polymer/graphene systems has been demonstrated as a viable strategy. Herein, we propose a simple route to increase the electrical conductivity of poly(methyl methacrylate) (PMMA)/graphene nanoplatelet (GnP) composites, by the in situ synthesis of gold nanoparticles directly into the solid film. In particular, PMMA, GnPs and a gold precursor are solution blended to form the composite films. The subsequent heat-induced formation of gold nanoparticles directly in the solid state film, cause the significant decrease of the percolation threshold of GnPs loading, from 3% to 1% by weight in the composite. This is attributed to the preferential formation of the gold nanoparticles onto the GnPs, with synergistic effects beneficial for the improvement of the electrical conductivity. The formation procedure of the gold nanoparticles, and their arrangement into the composite matrix are studied. We demonstrate that following this straightforward process it is possible to form nanocomposites able to conduct efficiently electric current even at low graphene loadings preserving at the same time the mechanical properties of the polymer matrix

Microscale patterning of hydrophobic/hydrophilic surfaces by spatially controlled galvanic displacement reactions.

In this letter, we report the design and fabrication of different metal patterns for the realization of spatially controlled hydrophobic/hydrophilic regions with micrometer resolution. The fabrication procedure, based on a combination of lithographic techniques and wet-chemistry reactions (namely, spontaneous Galvanic displacement reactions) is reliable, undemanding, and highly versatile, allowing the achievement of precise spatial control along with the use of a wide variety of different materials

Complex architectures formed by alginate drops floating on liquid surfaces

We demonstrate the generation of natural polymeric structures of complex shapes and controlled composition, starting from the collision of aqueous drops of alginate with the surface of a calcium ion-based liquid. We prove that by tuning the impact velocity of the alginate drops on the target surface one can control the floating state of the drops inducing the formation of mushroom-like structures, upon alginate gelation. Besides the geometric peculiarity, the presented approach allows us to provide dual functionality to the polymeric objects, attaching different kinds of functional molecules onto their surface areas, which are immersed or not in the liquid, making such architectures attractive for the development of a novel class of bionanocomposites