Zhaoxiang Deng

Toward a Universal "Adhesive Nanosheet" for the Assembly of Multiple Nanoparticles Based on a Protein-Induced Reduction/Decoration of Graphene Oxide

Graphene oxide (GO) can be reduced and decorated by bovine serum albumin (BSA) at suitable pH and temperature. The resulting bioconjugates between BSA and GO or reduced GO are ideal templates for highly efficient assembly of a variety of nanoparticles with dramatically different compositions, sizes, shapes, and properties. This methodology offers a great chance for investigations on the structure-performance relationship of hybrid nanomaterials toward combinatorial material design aiming at special functions and applications.

Single Cobalt Atoms with Precise N‐Coordination as Superior Oxygen Reduction Reaction Catalysts

A new strategy for achieving stable Co single atoms (SAs) on nitrogen-doped porous carbon with high metal loading over 4 wt % is reported. The strategy is based on a pyrolysis process of predesigned bimetallic Zn/Co metal-organic frameworks, during which Co can be reduced by carbonization of the organic linker and Zn is selectively evaporated away at high temperatures above 800 °C. The spherical aberration correction electron microscopy and extended X-ray absorption fine structure measurements both confirm the atomic dispersion of Co atoms stabilized by as-generated N-doped porous carbon. Surprisingly, the obtained Co-Nx single sites exhibit superior ORR performance with a half-wave potential (0.881 V) that is more positive than commercial Pt/C (0.811 V) and most reported non-precious metal catalysts. Durability tests revealed that the Co single atoms exhibit outstanding chemical stability during electrocatalysis and thermal stability that resists sintering at 900 °C. Our findings open up a new routine for general and practical synthesis of a variety of materials bearing single atoms, which could facilitate new discoveries at the atomic scale in condensed materials.

Surfactant-assisted hydrothermal synthesis of hydroxyapatite nanorods

Abstract A synthetic method, using the surfactant (SDS and CTAB) as regulator of the nucleation and crystal growth, with hydrothermal treatment as a successive process, is reported. The hydroxyapatites (HAps) obtained at room temperature were fibrous polycrystals and after hydrothermal treatment, nanorods (150 nm×10 nm) with uniform morphology. The process of crystal growth is discussed.

Bottom-up Assembly of RNA Arrays and Superstructures as Potential Parts in Nanotechnology

DNA and protein have been extensively scrutinized for feasibility as parts in nanotechnology, but another natural building block, RNA, has been largely ignored. RNA can be manipulated to form versatile shapes, thus providing an element of adaptability to DNA nanotechnology, which is predominantly based upon a double-helical structure. The DNA-packaging motor of bacterial virus phi29 contains six DNA-packaging RNAs (pRNA), which together form a hexameric ring via loop/loop interaction. Here we report that this pRNA can be redesigned to form a variety of structures and shapes, including twins, tetramers, rods, triangles, and 3D arrays several microns in size via interaction of programmed helical regions and loops. Three dimensional RNA array formation required a defined nucleotide number for twisting of the interactive helix and a palindromic sequence. Such arrays are unusually stable and resistant to a wide range of temperatures, salt concentrations, and pH.

Noncovalent DNA decorations of graphene oxide and reduced graphene oxide toward water-soluble metal–carbon hybrid nanostructures via self-assembly

Non-covalent DNA decorations on the basal planes of graphene oxide and reduced graphene oxide nanosheets are realized. The resulting DNA–carbon bioconjugates (DNA–GO or DNA–RGO) bearing multiple thiol groups tagged on DNA strands are then employed to scaffold the two-dimensional self-assembly of gold nanoparticles (AuNPs) into metal–carbon hybrid nanostructures (namely AuNP–DNA–GO or AuNP–DNA–RGO) that may find important applications in various aspects. The resulting heteronanostructures incorporating metal nanoparticles obtained by self-assembly are highly stable and water-soluble, and can be easily isolated by gel electrophoresis to guarantee high purity. Thanks to the noncovalent features of this method, either GO or RGO do not suffer from any permanent alterations of their structures and properties. In addition, the nanoparticles still maintain their optical absorbance after being assembled, and the assembly process is highly specific. This self-assembly based method for constructing heterostructured materials is excellent at overcoming any incompatibilities between nanoparticle syntheses and the formation of hybrid structures. As a result, this strategy is easily adaptable to various other materials other than gold nanoparticles and also favors the combinatorial assembly of multiple nanophases on a single nanosheet.

Formation of rod-like Mg(OH)2 nanocrystallites under hydrothermal conditions and the conversion to MgO nanorods by thermal dehydration

Abstract Mg(OH)2 nanorods have been successfully prepared via the hydrolysis of MgSO4 in aqueous ammonium hydroxide solution under hydrothermal conditions. Subsequent thermal decomposition of the as-prepared Mg(OH)2 nanorods produced MgO nanorods due to shape memory. The morphologies of the resultant Mg(OH)2 nanocrystallites were monitored at different periods of the hydrothermal process, which clearly revealed the formation process of the Mg(OH)2 nanorods. The morphology of the MgO product, as a dehydrated product of the rod-like Mg(OH)2 nanorods, remained similar to its precursor, Mg(OH)2. The reported method is low cost, simple and environmentally benign, thus it should be relatively easy to be scaled up for industrial production.

Synthesis of nanocrystalline TiO2 in alcohols

Abstract A solvothermal synthetic method to nanocrystalline titania has been carefully investigated in alcohol solutions. The selection of crystal structures, grain sizes and morphologies could be achieved through simply varying the alcohols and other reaction conditions. It is believed that HCl plays a significant role in determining the possible formation mechanism and the crystal structures. Although GC–MS and FT-IR results can give some information about the synthetic process, the formation of titania in these systems still remains unclear and both the hydrolytic and non-hydrolytic mechanisms might be involved. The products were also characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Raman as well as UV–VIS spectroscopy.

Characterization and synthesis of pure ZrO2 nanopowders via sonochemical method

Pure ZrO{sub 2} nanopowders have been synthesized via sonochemical method, which is a simple and energy efficient way to synthesize inorganic materials. The as-synthesized samples (hydrous zirconia, ZrO{sub 2}{center_dot}nH{sub 2}O) are characterized by several techniques: X-ray diffraction (XRD), thermogravimetric analysis (TGA), photoluminescence spectrometer (PLS) and Raman spectrometer (RS). It is shown that t-ZrO{sub 2} samples have two photoluminescence (PL) bands corresponding to the wavelengths of excitations of 254 and 412 nm. The structure of as-synthesized samples (ZrO{sub 2}{center_dot}nH{sub 2}O) and the formation mechanism of ZrO{sub 2} nanopowders are also discussed.

Room temperature synthesis of rutile nanorods and their applications on cloth

In order to achieve better photocatalytic performance, rutile nanorods dispersed in anatase and brookite phases were synthesized from titanium isopropoxide (TIP) in a concentrated HNO3 solution at room temperature (23 °C). X-ray diffraction results indicated that the percentage of rutile increased with increasing peptization time. Scanning electron microscopy and and high-resolution transmission electron microscopy measurements revealed that the nanosized titania particles mainly consisted of granular anatase and brookite, and rod-like rutile. It was interesting that the stability of the colloid increased with increasing nanoparticle concentration, and the tricrystalline titania showed a photocatalytic activity higher than that of pure anatase. These nanocrystals were applied onto cotton fabrics, and achieved a promising bactericidal photocatalytic activity and excellent protection against UV radiation.

Synthesis and characterization of Sb2Se3 nanorods

Abstract A hydrothermal reduction route was employed for the synthesis of Sb 2 Se 3 semiconductor nanorods. The reaction temperature for the formation of Sb 2 Se 3 nanorods should be above 130°C, otherwise impurities, such as Sb 2 O 3 and unreacted Se, would exist. The role of hydrazine as both the reducing agent and the coordinator was also found to be crucial for the formation of the rod-like morphologies. The products were characterized by XRD, SEM, TEM, XPS, absorption spectroscopy and Raman spectroscopy.