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

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

Rapid Self-Recoverable Hydrogels with High Toughness and Excellent Conductivity

Hydrogels as soft and wet materials have attracted much attention in sensing and flexible electronics. However, traditional hydrogels are fragile or have unsatisfactory recovery capability, which largely limit their applications. Here, a novel hydrogen bond based sulfuric acid–poly­(acrylic acid) (PAA)/poly­(vinyl alcohol) physical hydrogel is developed for addressing the above drawbacks. Sulfuric acid serves two functions: one is to inhibit the ionization of carboxyl groups from PAA chains to form more hydrogen bonds and the other is to provide conductive ions to promote conductivity of hydrogel. Consequently, the hydrogel obtains comprehensive mechanical properties, including extremely rapid self-recovery (strain = 1, instantly self-recover; strain = 20, self-recover within 10 min), high fracture strength (3.1 MPa), and high toughness (18.7 MJ m^–3). In addition, we demonstrate this hydrogel as a stretchable ionic cable and pressure sensor to exhibit stable operation after repeated loadings. This work provides a new concept to synthesize physical hydrogels, which will hopefully expand applications of hydrogel in stretchable electronics

Rapid Self-Recoverable Hydrogels with High Toughness and Excellent Conductivity

Hydrogels as soft and wet materials have attracted much attention in sensing and flexible electronics. However, traditional hydrogels are fragile or have unsatisfactory recovery capability, which largely limit their applications. Here, a novel hydrogen bond based sulfuric acid–poly­(acrylic acid) (PAA)/poly­(vinyl alcohol) physical hydrogel is developed for addressing the above drawbacks. Sulfuric acid serves two functions: one is to inhibit the ionization of carboxyl groups from PAA chains to form more hydrogen bonds and the other is to provide conductive ions to promote conductivity of hydrogel. Consequently, the hydrogel obtains comprehensive mechanical properties, including extremely rapid self-recovery (strain = 1, instantly self-recover; strain = 20, self-recover within 10 min), high fracture strength (3.1 MPa), and high toughness (18.7 MJ m^–3). In addition, we demonstrate this hydrogel as a stretchable ionic cable and pressure sensor to exhibit stable operation after repeated loadings. This work provides a new concept to synthesize physical hydrogels, which will hopefully expand applications of hydrogel in stretchable electronics