Dendritic Nanosheets Research Articles

A single step wet chemical approach to bifunctional ultrathin (ZnO)62(Fe2O3)38 dendritic nanosheets.

At the ultrathin scale, nanomaterials exhibit interesting chemical and physical properties, like flexibility, and polymer-like rheology. However, to limit the dimensions of composite nanomaterials at the ultrathin level is still a challenging task. Herein, by adopting a new low temperature single step and single pot wet chemical approach, we have successfully fabricated two dimensional (2D) mixed oxide ZnO-Fe2O3 dendritic nanosheets (FZDNSs). Various control experimental outcomes demonstrate that precursor salts of both the metals are crucial for the formation of stable 2D FZDNSs. The obtained FZDNSs not only exhibit the best photoreduction performance but also much enhanced electrocatalytic performance. This work will provide a promising avenue for the synthesis of cost effective transition metal mixed oxide based 2D nanosheets having wide ranging applications.

Architecting Hybrid Donor–Acceptor Dendritic Nanosheets Based on Polyoxometalate and Porphyrin for High‐Yield Solar Water Purification

AbstractHarvesting solar energy for saline and polluted water purification is a sustainable and affordable solution to alleviate the stress on water shortages. However, the water evaporation rate relies on high optical intensity and suffers from inadequate energy conversion. Herein, a novel hybrid donor–acceptor dendritic nanosheets (denoted as DNS) composed of phosphomolybdic acid (PMA) clusters and porphyrin ligands is reported. Experimental results and molecular dynamics simulations indicate that the PMA and porphyrin are oriented attachment and assembled into a stable nanostructure. Benefiting from the advantages of the unique structure and photosensitive components, the DNS exhibits high evaporation rate of 2.23 kg m‐2 h‐1 with 90.9% energy efficiency under 1 sun irradiation. It is noteworthy that the evaporation performance is upgraded by innovative technology, and even under 0.5 sun that is close to the natural sunlight intensity, the evaporation rate reaches up to 1.31 kg m‐2 h‐1, which exceeds that of the vast majority of the reported evaporators. Furthermore, this evaporator also displays excellent seawater desalination and wastewater decontamination based on photo‐thermal distillation, highlighting its potential application toward water purification.

Pt-on-Pd Dendritic Nanosheets with Enhanced Bifunctional Fuel Cell Catalytic Performance.

Pd-Pt bimetallic nanocrystals have become appealing in the electrocatalytic field by virtue of their synergy effects derived from the electronic coupling between two metals. Herein, a facile seed-mediated growth approach is reported for synthesis of Pt-on-Pd dendritic nanosheets (DNSs) through the growth of Pt branches on ultrathin Pd nanosheets (NSs). The as-obtained Pt-on-Pd DNSs exhibit superior catalytic activity toward both oxygen reduction reaction (ORR) and methanol oxidation reaction (MOR), with mass activities (MAs) 2.2 times higher for ORR and 3.4 times higher for MOR than commercial Pt/C catalysts. Moreover, these spatially separated Pt branches supported on 2D NSs also endow the Pt-on-Pd DNSs with impressive durability for ORR with only 18.9% loss in MA, whereas the Pt/C catalyst loses 50.0% after 10,000-cycle accelerated durability tests. This 2D DNS architecture can be extended to other 2D metallic NS substrates for constructing Pt-based electrocatalysts with excellent electrocatalytic performance.

Nanoengineering 2D Dendritic PdAgPt Nanoalloys with Edge-Enriched Active Sites for Enhanced Alcohol Electroxidation and Electrocatalytic Hydrogen Evolution.

Lots of research studies reveal that the surface atoms on the top/bottom facets of the nanosheets are the key features in enhancing electrocatalytic activity while the edge and corner sites of electrocatalysts often possess superior activity. Herein, we report 2D dendritic PdAgPt ternary nanoalloys with abundant crystal defects such as steps, twin boundary, and atomic holes, which can effectively work as catalytic active-sites. The morphology of PdAgPt nanoalloys can be regulated readily from dendritic nanosheets to nanowheels. Compared with binary Pd68Ag32 nanodendrites, Pd62Pt38 nanospheres, and Pt/C catalyst, the composition- and morphology-optimized Pd43Ag21Pt36 nanowheels exhibit the best mass/specific activity and stability for methanol/ethanol oxidation reaction (MOR/EOR). The mass peak current density for EOR/MOR of Pd43Ag21Pt36 is 7.08/3.50 times of the Pt/C catalyst. Simultaneously, the hydrogen evolution reaction performance of the Pd43Ag21Pt36 nanowheels in terms of the lowest overpotential of 9 mv at a current density of 10 mA/cm2 and high electrochemical stability is much better than that of binary Pd68Ag32 nanodendrites, Pd62Pt38 nanospheres, and Pt/C.

Preparation of hierarchical WO3 dendrites and their applications in NO2 sensing

Hierarchical WO3 dendrites were synthesized via low-cost and environmental-friendly solvothermal strategy. Characterization results indicated that WO3 dendrites were composed of several multi-directional dendritic nanosheets. To further understand the formation of WO3 dendrites, time-dependent experiments were carried out and formation mechanism was investigated. Since such dendritic structures rarely occurred in the field of gas sensing, the synthesized WO3 dendrites were subjected to detailed NO2 sensing tests. Results demonstrated that WO3 dendrites based sensors had low detection limit (200 ppb) and fast response and recovery (7s, 12s to 5 ppm NO2). Moreover, the sensor was also highly sensitive, selective and stable at low optimal operating temperature of 140°C.

Graphene supported foam-like platinum electrocatalyst for oxygen reduction reaction

Graphene supported platinum seeds localized in between liposomal bi-layer provide a unique supporting-seeding-templating tri-functional reaction environment that permits the synthesis of graphene supported foam-like platinum (Pt foam/G). Pt foam consists of 2–3 nm thick dendritic nanosheets. In order to prevent graphene from stacking together, carbon black particles were inserted among graphene sheets. Interestingly, Pt foam/G showed a much higher oxygen reduction reaction (ORR) activity compared with commercial Pt/C composed of semi-spherical nanoparticles supported on carbon. Moreover, accelerated durability test demonstrated that the Pt foam/G exhibited a better stability than commercial Pt/C.

Fabrication of the flower-like Zn5(OH)6(CO3)2 and ZnO microstructures consisting of the dendritic nanosheets

The flower-like Zn5(OH)6(CO3)2 microstructures consisting of dendritic nanosheets were successfully prepared by the PEG 1000 and terpineol-assisted hydrothermal process. The flower-like Zn5(OH)6(CO3)2 microstructures could be converted to the flower-like ZnO microstructures consisting of dendritic nanosheets when the flower-like Zn5(OH)6(CO3)2 microstructures were decomposed in Muffle. The optical properties of flower-like ZnO nanostructures were investigated. The formation mechanism of the flower-like Zn5(OH)6(CO3)2 microstructures was also discussed. The experiments shown that the Zn5(OH)6(CO3)2 nuclei preferentially grew along the [100] direction under the assistance of PEG 1000 and terpineol. The flower-like Zn5(OH)6(CO3)2 microstructures consisting of dendritic sheets were formed through an Ostwald ripening process.

Evolution of dendritic nanosheets into durable holey sheets: a lattice gas simulation study

Monte Carlo lattice gas simulations are performed to study sintering in a realistic dendritic platinum nanosheet. The morphological and topological transformations observed in the simulations are in good agreement with sintering experiments. Employing an intuitive method of quantifying surface area, the stability of the surface area of the dendritic nanosheets is analyzed. The surface area is found to have a double exponential decay, one decay corresponding to rapid coarsening of dendritic features into pores and the other decay corresponding to a slow disappearance of unstable pores. Long duration simulations indicate that the thickness of the dendritic nanosheet remains fairly stable. Stability simulations of a single model pore in a sheet establish that there exists a narrow range of sheet thickness and pore size combinations that produces stable holey sheets. Outside this parameter range pores either rapidly close or expand without bound. The thickness of the engineered dendritic platinum nanosheet and the size of the crevices between dendritic arms put the Pt sheet into this stable range, further corroborating the detailed simulations and explaining the persistence of pores observed in actual dendritic platinum nanosheets.

Construction of Cuprous Oxide Electrodes Composed of 2D Single‐Crystalline Dendritic Nanosheets

An unusual anisotropic growth of Cu(2)O is stabilized via the electrochemical synthesis of Cu(2)O in the presence of Ag(+) ions, which results in the formation of Cu(2)O electrodes composed of 2D sheetlike crystals containing complex dendritic patterns. It is quite unusual for Cu(2)O to form a 2D morphology since it has a 3D isotropic cubic crystal structure where the a, b, and c axes are equivalent. Each Cu(2)O sheet is single-crystalline in nature and is grown parallel to the {110} plane, which is rarely observed in Cu(2)O crystal shapes. A various set of experiments are performed to understand the role of Ag(+) ions on the 2D growth of Cu(2)O. The results show that Ag(+) ions are deposited as silver islands on already growing Cu(2)O crystals and serve as nucleation sites for the new growth of Cu(2)O crystals. As a result, the growth direction of the newly forming Cu(2)O crystals is governed by the diffusion layer structure created by the pre-existing Cu(2)O crystals, which results in the formation of 2D dendritic patterns. The thin 2D crystal morphology can significantly increase the surface-to-volume ratio of Cu(2)O crystals, which is beneficial for enhancing various electrochemical and photoelectrochemical properties of the electrodes. The photoelectrochemical properties of the Cu(2)O electrodes composed of 2D dendritic crystals are investigated and compared to those of 3D dendritic crystals. This study provides a unique and effective route to maximize the {110} area per unit volume of Cu(2)O, which will be beneficial for any catalytic/sensing abilities that can be anisotropically enhanced by the {110} planes of Cu(2)O.

Synthesis of Platinum Nanowheels Using a Bicellar Template

Disk-like surfactant bicelles provide a unique meso-structured reaction environment for templating the wet-chemical reduction of platinum(II) salt by ascorbic acid to produce platinum nanowheels. The Pt wheels are 496 +/-55 nm in diameter and possess thickened centers and radial dendritic nanosheets (about 2-nm in thickness) culminating in flared dendritic rims. The structural features of the platinum wheels arise from confined growth of platinum within the bilayer that is also limited at edges of the bicelles. The size of CTAB/FC7 bicelles is observed to evolve with the addition of Pt(II) complex and ascorbic acid. Synthetic control is demonstrated by varying the reaction parameters including metal salt concentration, temperature, and total surfactant concentration. This study opens up opportunities for the use of other inhomogeneous soft templates for synthesizing metals, metal alloys, and possibly semiconductors with complex nanostructures.

Foamlike Nanostructures Created from Dendritic Platinum Sheets on Liposomes

The synthesis of novel dendritic platinum sheets of 2-nm thickness by the reduction of an aqueous metal complex with ascorbic acid in the presence of liposomes is reported. Variation of the reaction conditions, including incorporation of a tin porphyrin photocatalyst within the liposomal bilayer to initiate seed-particle growth, allows access to a diverse range of platinum nanostructures, including dendritic nanosheets of uniform diameters and convoluted foamlike structures composed of interwoven dendritic nanosheets. The mechanism of formation of these nanomaterials is investigated with regard to the photocatalytic generation of platinum nanoparticle seeds, the autocatalytic dendritic growth, and the templating on liposomes. The discrete nanospheres of foamlike platinum are of particular interest, as they may have advantages over conventional platinum black in some applications. For example, they will likely exhibit improved electrical connectivity and mass-transport properties in electrocatalytic applications. Electrochemical CO-stripping measurements and N2 adsorption experiments show that the nanospheres of foamlike platinum possess high surface areas. In addition, these platinum foam nanospheres are as active as commercial platinum black in catalyzing the four-electron oxygen reduction reaction.