Renjie Zhang

Inflating Strategy To Form Ultrathin Hollow MnO2 Nanoballoons

Ultrathin MnO2 hollow nanoballoons (UMHNBs) have a large ratio of interfacial to total atoms, corresponding to expected improved performance. However, their synthesis is a challenge due to difficulty in controlling the concentration of the unit cells. Herein, we describe a strategy to synthesize dry intact UMHNBs through a one-step synthesis by inflating MnO2 (reduced from KMnO4) with CO2 (oxidized from single-layer graphene oxide nanosheets) followed by instant freeze-drying. UMHNBs are 30-500 nm in diameter with a shell thickness of 3.7 nm, packing with laminar [MnO6] unit cells in the form of δ-MnO2. UMHNBs show efficient catalytic activity for decomposing the organic dye methylene blue (MB), 15 times the biggest reported value, and have long-term catalytic efficacy and durability. The described strategy in this paper makes use of graphene nanosheets to assemble durable ultrathin hollow nanoballoons.

Monolayer aggregation of a series of atypical amphiphilic β-diketone rare earth complexes at air/liquid interface

Abstract Monolayer aggregation of a series of atypical amphiphilic rare earth complexes REL 3 Phen [RE=Eu(III), Sm(III), Tb(III); L=acac (acetylacetone), TFA (trifluoroacetylacetone), HFA (hexafluoroacetylacetone), TTA (thenoyltrifluoroacetone); Phen=1, 10-phenanthroline] were investigated at the air/liquid interface by π - A isotherms, Brewster angle microscopy (BAM) and transmission electron microscopy (TEM). When the complexes were mixed with arachidic acid (AA), respectively, stable monolayers could be formed. The rare earth complexes could be divided into two classes according to the π - A isotherm shape that whether there was a plateau period or not. Complexes with β-diketones acac, TFA and HFA were in one class, while complexes with the β-diketone TTA were in another. All the rare earth complexes formed microcrystals at the air/liquid interface. However, the former complex microcrystals oriented with the same crystal plane facing to all directions upon compression; while the latter complex microcrystals oriented with the same crystal plane facing to the same direction. Differences between monolayer behaviors of the two classes of complexes were discussed by comparing the structure of β-diketone ligands. A possible structural model of the rare earth complexes in the mixed monolayers with AA at air/liquid interface was proposed.

Coassembly and high ORR performance of monodisperse Pt nanocrystals with a mesopore-rich nitrogen-doped graphene aerogel

Solving the problems of the decrease of exposed active surfaces of Pt nanoparticles due to aggregation and their non-uniform dispersion is key to yielding high catalytic activity. In this work, monodisperse Pt nanocrystals (PtNCs) with a small size (2.8 nm in average diameter) and large exposed active surfaces are obtained by designing, inducing and dispersing the PtNCs on a 3D mesopore-rich nitrogen-doped graphene aerogel (NGA) through a facile one-step coassembly. Such a coassembly of PtNCs with NGA (PtNCs@NGA) has a large specific surface area (1750 m2 g−1), rich mesopores (the ratio of mesopores of 2–5 nm to all mesopores is 78%), and a high N content (3.93 at%). The unique structure of PtNCs@NGA not only ensures the exposure of the active PtNCs to O2 and decreases the diffusion time of O2 inside the pore channels, but also increases the adsorption and diffusion of O2 in PtNCs@NGA, consequently increasing the oxygen reduction reaction (ORR) speed and yielding better electrocatalytic activity than those of so far reported metal catalysts on carbon materials. The simple and low-cost preparation of the PtNCs@NGA catalyst renders it the most promising among electrocatalysts for application in fuel cells.

Rough glass surface-mediated formation of vesicles from lauryl sulfobetaine micellar solutions.

We report novel vesicles composed of the zwitterionic surfactant lauryl sulfobetaine (LSB), which is a simple single-tailed surfactant (STS). The novel vesicles spontaneously formed from LSB micellar solutions with the mediation of a rough glass surface (RGS) in the absence of any cosurfactants or additives. Importantly, the obtained STS vesicles displayed good stability upon long-term storage, exposure to high temperature, and freeze-thawing after the RGS was removed. The pH of the LSB solution (4.0-9.0) and the presence of NaCl (1.0 × 10(-5) and 1.0 × 10(-4) mol/L) in the LSB solution had no obvious influence on the formation and stability of the vesicles. The adsorption configuration of LSB on the RGS was investigated via water contact angle measurements and atomic force microscope observations. The results showed that LSB adsorption bilayers could form on the RGS, and the bilayer adsorption of LSB on the RGS and the roughness of the solid surface played a key role in the vesicle formation. A possible mechanism for the RGS-mediated formation of LSB vesicles is proposed: LSB micelles and molecules adsorb on the RGS to form curved bilayers, and the curved bilayers are then detached from the RGS and close to form vesicles. To the best of our knowledge, this is the first report of LSB alone forming vesicles. This finding extends our understanding of the nature of vesicle systems.

Fabrication of pore-rich nitrogen-doped graphene aerogel

Tuning the porosity of NGAs by tailoring the size of GONSs results in the pore-richest NGA with the best mechanical stability and electrocatalytic biosensing activity by using the smallest sonicated GONSs with DA as precursors, where DA favours high N content and 3D crosslinking capability.

Thickness-determined photocatalytic performance of bismuth tungstate nanosheets

Bismuth tungstate (Bi2WO6) nanosheets with dominant exposed (010) facets and various thicknesses (H) and lateral sizes were hydrothermally synthesized via pH adjustment of precursor suspensions. As the pH increases from <1 to 8, the resultant nanosheets exhibit improved crystallinity and photoabsorption, decreased specific surface area, increased H, and decreased photoactivity in the degradation of rhodamine B (RhB), methylene blue (MB), and Eosin Y (EY) under visible light irradiation. The photoactivity of the Bi2WO6 sample obtained at pH < 1 is about 6, 100, and 25 times of that at pH 8 for RhB, MB, and EY degradation, respectively. The photoactivity enhancement is ascribed to reduction of the H. The photocatalytic efficiencies are inversely proportional to the reduction of H2 when the nanosheets can be penetrated by incident light. This work reveals the structure–performance relationship of Bi2WO6 nanosheets and provides significant guidance for preparation of high efficient two-dimensional photocatalysts.

Preparation of preferentially exposed poison-resistant Pt(111) nanoplates with a nitrogen-doped graphene aerogel

A poison-resistant and highly catalytically active Pt(111) lattice on ultrathin Pt nanoplates (Pt(111)NPTs) with a large ratio (28%) of surface active to sum Pt atoms is obtained with a dense small pore N-atom doped aerogel (NGA) featuring a large specific surface area and high N content in the graphene skeleton.

Morphology control of BaCO3 by template and polymer–inorganic precursor

Barium carbonate (BaCO3) within the controllable morphology of nanorods (NRs) was prepared by employing pore channels of a polycarbonate (PC) membrane as the template, combining with poly(sodium 4-styrene-sulfonate) (PSS). To further lower the crystallization process, (PSS/PAH)1.5 polyelectrolyte layers were assembled on the pore channels of the PC membrane. (PSS/PAH)1.5 layers coated on the BaCO3 NRs increase the mechanical strength.