Biomolecule-assisted Route Research Articles

Biomolecule-assisted route to obtain nanostructured bismuth oxybromide with enhanced photocatalytic activity

Using a microwave-assisted hydrothermal method, we synthesized BiOBr powders, with and without, glycine or phenylalanine as templates. The samples were characterized by X-ray Diffraction, UV–Vis Diffuse Reflectance Spectroscopy, and Field Emission Gun Scanning Electron Microscopy. The XRD patterns were indexed to the tetragonal structure and presented very different intensities from each other, which is consistent with changes in the structural organization. The FEG-SEM images showed morphology alterations, from nanoplates for unmodified BiOBr to nanolamellae for BiOBr with phenylalanine (BOB-phe). The catalytic activity of BOB-phe degraded 98% of Rhodamine B dye in approximately 20min, while the other BiOBr compounds presented slower degradation kinetics, which could be explained by a higher amount of active sites on BOB-phe surface.

Biomolecule-assisted route for shape-controlled synthesis of 3D flower-like CdWO4 microstructures

Plausible mechanism for the formation of 3d hierarchical flower-like structures.

A novel synthesis of star-like FeWO4 nanocrystals via a biomolecule-assisted route

Uniform hierarchical star-like ferrous tungstate (FeWO4) is synthesized in a facile manner via a biomolecule-assisted green route without the need for using pre-fabricated templates and reductive agents. l-cysteine in this protocol was not only skillfully useful as a complexing and reducing agent, but also utilized as a structure-directing agent for the formation of star nanostructure. The as-prepared FeWO4 nanostars were characterized by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, etc. The results indicate that thickness of the star-like FeWO4 orderly assembled by the nanosheets is ~50 nm. The concentrations of l-cysteine and reaction time play important roles in the assembly of the star-like nanostructure. The morphology of FeWO4 dramatically varies from nanowires (diameter of ~20 nm) to nanoblades with an average thickness of 40 nm, then to the hierarchical star-like FeWO4 according to the changes of experiment conditions. The resulting FeWO4 nanostars with higher order symmetries were phase-pure and possess single crystalline structure. In addition, the star-like FeWO4 shows a small ferromagnetic ordering at low temperature. Moreover, a coordination adsorption and oriented attachment and Ostwald ripening mechanism are proposed for explaining the formation process of star-like FeWO4.

Biomolecule-assisted route for shape-controlled synthesis of single-crystalline MnWO4nanoparticles and spontaneous assembly of polypeptide-stabilized mesocrystal microspheres

Single-crystalline mixed metal oxide nanoparticles and 3D hierarchical mesocrystal microspheres of MnWO4 have been synthesized on a large scale by a facile single-step hydrothermal method using Mn(NO3)2 and Na2WO4 precursors, and capping bifunctional amino acid biomolecules with different alkyl chain lengths, and water or water/ethylene glycol medium. The resulting single-crystalline MnWO4 nanoparticles with different uniform shapes including bar, rod, square, quasi-sphere, sphere, hexagonal crystals were obtained by tuning the synthetic conditions such as the concentration and the alkyl chain length of amino acids, pH, and reaction temperature. By decreasing the Mn2+ and WO42− precursor monomer concentration from 0.0150 to 0.0076 M in aqueous media, polypeptide-stabilized MnWO4 mesocrystal hierarchical microspheres were achieved, due to the spontaneous-assembly of primary nanoparticles through the back-bone–back-bone intermolecular hydrogen bonding interactions of polypeptide chains. Nanoplatelet-based microapples with two holes on their poles were also obtained under the same synthetic conditions for the microspheres, except that the use of water/ethylene glycol (10:30 mL) instead of water medium. The photoluminescence (PL) results revealed that the PL emission intensity of the MnWO4 nanobars is higher than that of the self-assembled MnWO4 microspheres. This green chemistry method is simple and highly reproducible, using inexpensive reagents, and water as reaction solvent. The uniform MnWO4 nanorods with the control of aspect ratio (length/width) can be produced in a large quantity as much as 16 g in a single preparation. The current approach is quite general and able to be extended to a variety of other well-defined metal oxide and mixed oxide nanomaterials with controlled shapes.

Aspartic-Acid-Assisted Hydrothermal Growth and Properties of Magnetite Octahedrons

A biomolecule-assisted hydrothermal route to the fabrication of magnetite (Fe3O4) with uniform microsized and regular octahedral morphology has been successfully developed by use of toxic-free aspartic acid as reducing reagent and FeCl3·6H2O as iron source. The as-prepared magnetite was characterized by X-ray diffraction (XRD), Raman spectroscopy, field emission scanning electron microscopy (FESEM), and high-resolution transmission electron microscopy (HRTEM). Altering different experimental parameters showed that pH of the aspartic acid solution, concentration of aspartic acid, and hydrothermal temperature can significantly influence product phase composition. Furthermore, a series of time-course experiments revealed that growth of regular octahedral magnetite is controlled by the Ostwald ripening process. This biomolecule-assisted route may be expected to be applicable for the fabrication of other transition metal oxides with uniform size and morphology. Besides, magnetic properties of the product were characterized on a vibrating sample magnetometer (VSM). The values of saturation magnetization (Ms), remanent magnetization (Mr), and coercivity (Hc) of the magnetite octahedrons are 71.6 emu/g, 9.8 emu/g, and 120 Oe, respectively. The electrochemical performances of the magnetite octahedra exhibit a discharge capacity of ca. 600 mAh/g in the first cycle and a discharge voltage of 0.92 and 0.74 V, respectively.

Biomolecule-assisted synthesis of single-crystalline selenium nanowires and nanoribbons viaa novel flake-cracking mechanism

Recently, the biomolecule-assisted synthesis method has been a new and promising focus inthe preparation of various nanomaterials. But current works mainly focus on the synthesisof metal nanoparticles and nanowires using macro-biomolecules (e.g. virus, protein andDNA) as templates in the presence of a reducing agent. Beta-carotene, one of the mostcommon bio-antioxidants, can be oxidized to form species with both hydrophilic andhydrophobic ends, which can provide an in situ soft template for the synthesis ofnanomaterials. Herein, a simple beta-carotene-assisted method was developed for the firsttime to synthesize t-Se nanowires and nanoribbons with high crystallinity. We demonstratethat beta-carotene serves as not only the reducing agent, but also an in situ template in thepreparation of Se one-dimensional nanostructures. It is found that the growthmechanism of Se nanomaterials is different from the familiar sphere–wire process. Anovel flake-cracking mechanism is proposed. By this biomolecule-assisted route,Te one-dimensional nanostructures and Pd nanowires were also fabricated. Theassisted-biomolecule in our method may be spread to carotenoids and other antioxidants,and thus broaden the application fields of biomolecules. Our preliminary investigationshave shown that the facile, solution-phase biomolecule-assisted method can bepotentially extended to the preparation of other low-dimensional nanostructures. Thesynthesized t-Se nanowires and nanoribbons may serve as templates to generateother tubular functional nanomaterials and find applications in the studies ofstructure–property relationships as well as in the fabrication of nanoscale optoelectronicdevices.