Improving Surface Adsorption via Shape Control of Hematite α‑Fe₂O₃ Nanoparticles for Sensitive Dopamine Sensors

α-Fe₂O₃ nanoparticles (NPs) with morphologies varying from shuttle to drum were synthesized through an anion-assisted and surfactant-free hydrothermal method by simply varying the ratios of ethanol and water in solvent. Control experiments show that the structural evolution can be attributed to a small-molecular-induced anisotropic growth mechanism in which the growth rate of α-Fe₂O₃ NPs along the <i>a</i>-, <i>b</i>-, or <i>c</i>-axis was well-controlled. The detailed structural analysis through the high-resolution transmission electron microscope (HRTEM) indicated that shuttle-like Fe₂O₃ NP surface was covered by high-density atomic steps, which endowed them with the enhanced adsorption and sensor ability toward dopamine (DA). The XPS characterizations indicated that the percentages of the O_C component follow the order of shuttle-like Fe₂O₃ (S-Fe₂O₃ for short) > pseudoshuttle-like Fe₂O₃ (Ps-Fe₂O₃ for short) > polyhedron-like Fe₂O₃ (Ph-Fe₂O₃ for short) > drum-like Fe₂O₃ (D-Fe₂O₃ for short). Benefits from these structural advantages, the S-Fe₂O₃ NPs–Nafion composite electrode exhibited remarkable electrochemical detection ability with a wide liner range from 0.2 μM to 0.107 mM and a low detection limit of 31.25 nM toward DA in the presence of interferents

Unusual Designated-Tailoring on Zone-Axis Preferential Growth of Surfactant-Free ZnO Mesocrystals

An unusual designated-tailoring on zone-axis preferential growth of surfactant-free ZnO mesocrystals with different features (shapes and sizes) was successfully achieved via an additive-free complex-precursor solution method. The formation of ZnO mesocrystals here is essentially determined by the characteristic of [Zn­(OH)4]2– precursors, and an oriented nanoparicle aggregation with tailoring sizes and shapes can occur in different concentration of reactants at higher reaction temperature. Spindle-like ZnO mesocrystals with tunable sizes (along the c-axis direction) were synthesized by adjusting the concentration of hydroxyl ions, and peanut-like ZnO mesocrystals with controllable sizes (along the c-axis direction) and shapes (perpendicular c-axis direction) were prepared by tailoring the concentration of zinc ions. Structural and morphological evolutions were investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and field-emission scanning electron microscopy (FESEM). The study is of great significance in bottom-up assembly of controllable ordering architectures, and provides a good opportunity to understand the formation mechanism and fundamental significance of zone-axis preferential growth of ZnO mesocrystals. Significantly, it is believed that the precursor driven assembly of mesostructures reported here would provide a green way to design more and more surfactant-free metal oxide architectures with well-defined shapes

Table_1_Ion-Induced Synthesis of Alginate Fibroid Hydrogel for Heavy Metal Ions Removal.DOCX

Design and synthesis of environmentally friendly adsorbents with high adsorption capacities are urgently needed to control pollution of water resources. In this work, a calcium ion-induced approach was used to synthesize sodium alginate fibroid hydrogel (AFH). The as-prepared AFH has certain mechanical strength, and the mechanical strength is enhanced especially after the adsorption of heavy metal ions, which is very convenient for the recovery. AFH exhibited excellent adsorption performances for Cu2+, Cd2+, and Pb2+ ions and displayed very high saturated adsorption capacities (Qe) of 315.92 mg·g−1 (Cu2+), 232.35 mg·g−1 (Cd2+), and 465.22 mg·g−1 (Pb2+) with optimized pH values (3.0–4.0) and temperature (303 K). The study of isotherms and kinetics indicated that adsorption processes of heavy metal ions fitted well with the pseudo-second-order kinetics model and the Langmuir model. Pb2+ was found to have the strongest competitiveness among the three heavy metal ions. Thus, AFH has great application prospects in the field of heavy metal ions removing from wastewater.</p

Sodium Chloride Template Synthesis of Cubic Tin Dioxide Hollow Particles for Lithium Ion Battery Applications

This paper describes a new synthesis and lithium ion charge–discharge property of tin dioxide (SnO₂) hollow nanocubes. SnO₂ is one of the best-known anode materials for lithium-ion battery application because of its high lithiation-delithiation capacity. Hollow nanostructures with high surface area are preferred, because they accommodate large volume changes and maintain the structural stability of electrode materials during charge–discharge cycles. The SnO₂ hollow cubes made in this study had a discharge capacity of up to 1783 mA h g^–1 for the initial cycle and 546 mA h g^–1 after 30 cycles at a current density of 0.2 C between 0.02 and 2.0 V (vs Li/Li⁺)

Facile Water-Assisted Synthesis of Cupric Oxide Nanourchins and Their Application as Nonenzymatic Glucose Biosensor

We have demonstrated an interesting approach for the one-pot synthesis of cupric oxide (CuO) nanourchins with sub-100 nm through a sequential dissolution–precipitation process in a water/ethanol system. The first stage produces a precursory crystal [Cu₇Cl₄(OH)₁₀H₂O] that is transformed into monoclinic CuO nanourchins during the following stage. Water is a required reactant for the morphology-controlled growth of different CuO nanostructures. When evaluated for their nonenzymatic glucose-sensing properties, these CuO nanourchins manifest higher sensitivity. Significantly, this water-dependent precursor transformation method may be widely used to effectively control the growth of other metal oxide nanostructures

Ultrathin Pt-Based Alloy Nanowire Networks: Synthesized by CTAB Assistant Two-Phase Water−Chloroform Micelles

Ultrathin Pt-based PtM (M = Pd, Ru, Au, Fe) alloy nanowire networks could be facilely synthesized using a soft template formed by cetyltrimethylammonium bromide in a two-phase water−chloroform system. The as-synthesized Pt-based alloyed nanowires show the fcc crystal phase. They have an average diameter of ∼2.3 nm and form porous nanonetworks, which can be potentially used for a number of catalytic applications. It was found that PtRu alloy nanonetworks showed more efficient catalytic activity for the hydrogenation of azo bonds in methyl orange than that of PtPd, PtAu, and pure Pt

Size Effect on Nanoparticle-Mediated Silver Crystal Growth

Understanding of the nanoparticle (NP)-mediated crystal growth mechanism is essential for the syntheses of nanostructures with desired physical and chemical properties. A facile protocol is developed to study the size effect of primary NPs on the silver NP-mediated crystal growth process. Experimental observation shows that the primary NPs size performs a key role for the crystal final shape and structure. Theory study discloses that water solution will promote an amorphous structure of small primary NPs which thus perform a different assembly process for NP-mediated crystal formation compared with larger crystalline primary NPs

Growth of Gold Nanoplates: The Case of a Self-Repair Mechanism

In this communication, we present a novel and interesting self-repair mechanism, in which the growth of gold nanoplates is due to the self-repair of the nanopores in porous nanoframes induced by UV irradiation. TEM images indicated that the initially formed branched fragments developed into nanoplates through a medium porous frame. In such porous frames, the attachment and fusion of small nanoparticles onto the pores’ edges led to the formation of growth front (bulges). The opposite growth of the bulges divided the bigger pores into the smaller. The HRTEM image showed that the grain-rotation-induced grain coalescence (GRIGC) mechanism was responsible for the ultimate closure of nanopores to form intact nanoplates

Electron Tunneling Induced Periodic Nucleation and Growth of Nanoparticles: Physical Basis of Chemical Reduction

We have developed a periodic nucleation and growth mechanism for nanoparticle-aggregated structure based on electron tunneling process that occurs in chemical replacement reactions. This electron tunneling process, which is a fundamental physical phenomenon, successfully explains the repeated formation of nanoparticles that has been observed in the experiment. Using the nanoparticle-mediated progress, we have interpreted the origin of layer-by-layer nanoparticle stacking polycrystalline nanostructures and mesocrystal in chemical reductions

Rapid Oxidation Synthesis of Hollow Cupric Oxide-Decorated rGO with High Performance and Kinetically Enhanced Lithium Storage

From the perspective of promotion of metal oxide anodes’ performance, structural design and reinforcement of carbon materials are always concerned as useful methods. In addition, high hope is being placed on the use of graphene as an ideal potential carbon reinforcement material for an abundant energy market, but currently, commercial graphene has poor intrinsic properties, which hamper its development in the energy storage area. Therefore, combining the metal oxide materials with commercial graphene by a rational structure design could be a more hopeful method to realize the productive use of commercial graphene in the energy storage area. In this work, hollow cupric oxide (CuO) decorated on reduced graphene oxide (rGO) is prepared by an effective glycol–water combined rapid oxidation strategy. The well-designed composite yields a high initial capacity of 1491 mAh/g and maintains 960 mAh/g after 500 cycles at 1.0 A/g. The remarkable reversible capacity may be attributed not only to the hollow structure of CuO, but also to the bidirectional synergy between graphene and the small-sized CuO. The galvanostatic intermittent titration technique (GITT) and density functional theory (DFT) calculation are conducted to analyze the relationship between the electrochemical properties and surface states. The GITT test shows that the ion diffusion coefficient is higher when the smaller hollow CuO is decorated on rGO. Additionally, the DFT results indicate that more active electrons appear on the surface of the composite. As a result, the as-prepared hollow and smaller CuO-decorated rGO presents excellent performance in terms of specific capacity and rate capability