Rapid fabrication of complex nanostructures using room-temperature ultrasonic nanoimprinting

Sonochemical Synthesis of Low-Dimensional Nanostructures and Their Applications-A Review

Sonochemical synthesis is becoming a popular method of preparing various nanomaterials, including metals, carbons, oxides, and chalcogenides. This method is relatively cheap and responds to the challenges of green chemistry as it typically does not involve high temperatures, high pressures, inert atmospheres, or long reaction times in comparison to other conventional methods. The utilization of ultrasound in synthesis makes the elimination of toxic solvents possible, as well as the execution of the synthesis without the use of reducing and stabilizing agents, while receiving products with the same or even better properties. The application of ultrasound allows for the synthesis of various nanomaterials with different properties for use in fields such as catalysis, electrochemistry, medicine, and biosensors. The final product is influenced by multiple variables such as temperature, pH, reagents, capping agents, time of reaction, and the addition of dopants.

In Situ Nanomechanics: Opportunities Based on Superplastic Nanomolding

In situ nanomechanics, referring to the real-time monitoring of nanomechanical deformation during quantitative mechanical testing, is a key technology for understanding the physical and mechanical properties of nanoscale materials. This perspective reviews the progress of in situ nanomechanics from the aspects of preparation and testing of nanosamples, with a major focus on one-dimensional (1D) nanostructures and discussions of their challenges. We highlight the opportunities provided by in situ nanomechanics combined with the superplastic nanomolding technique, especially in the aspects of regulating physical and chemical properties which are highly exploitable for mechanoelectronics, mechanoluminescence, piezoelectronics, piezomagnetism, piezothermography, and mechanochemistry.

Enhancing electrocatalytic methanol oxidation of Pd-Ir nanoalloy through electron-rich catalytic interface induced by incorporating phosphorus

Incorporating less expensive nonmetal phosphorus (P) into noble metal-based catalysts has become a developing strategy to enhance the catalytic performance of electrocatalysts for methanol electrooxidation reaction (MOR), attributing to the electronic and synergistic structure alteration mechanism. In the work, three-dimensional nitrogen-doped graphene anchoring ternary Pd-Ir-P nanoalloy catalyst (Pd₇IrP_x/NG) was prepared by co-reduction strategy. As a multi-electron system, elemental P adjusts the outer electron structure of Pd and diminishes the particle size of nanocomposites, which heightens the electrocatalytic activity effectively and accelerate MOR kinetics in alkaline medium. The study reveals that the electron effect and ligand effect induced by P atoms on the hydrophilic and electron-rich surface of Pd₇Ir/NG and Pd₇IrP_x/NG samples can reduce the initial oxidation potential and peak potential of CO_ads, showing significantly enhanced the anti-poisoning ability compared with commercial Pd/C as the benchmark. Meanwhile, the stability of Pd₇IrP_x/NG is significantly higher than that of commercial Pd/C. The facile synthetic approach provides an economic option and a new vision for the development of electrocatalysts in MOR.

Development and Analysis of Electrochemical Reactor with Vibrating Functional Element for AAO Nanoporous Membranes Fabrication

Nanoporous anodic aluminum oxide (AAO) is needed for a variety of purposes due to its unique properties, including high hardness, thermal stability, large surface area, and light weight. Nevertheless, the use of AAO in different applications is limited because of its brittleness. A new design of an electrochemical reactor with a vibrating element for AAO nanoporous membranes fabrication is proposed. The vibrating element in the form of a piezoceramic ring was installed inside the developed reactor, which allows to create a high-frequency excitation. Furthermore, mixing and vibration simulations in the novel reactor were carried out using ANSYS 17 and COMSOL Multiphysics 5.4 software, respectively. By theoretical calculations, the possibility to excite the vibrations of five resonant modes at different frequencies in the AAO membrane was shown. The theoretical results were experimentally confirmed. Five vibration modes at close to the theoretical frequencies were obtained in the novel reactor. Moreover, nanoporous AAO membranes were synthesized. The novel aluminum anodization technology results in AAO membranes with 82.6 ± 10 nm pore diameters and 43% porosity at 3.1 kHz frequency excitation and AAO membranes with 86.1 ± 10 nm pore diameters and 46% porosity at 4.1 kHz frequency excitation. Furthermore, the chemical composition of the membrane remained unchanged, and the hardness decreased. Nanoporous AAO has become less brittle but hard enough to be used for template synthesis.

Machine learning-based prediction and inverse design of 2D metamaterial structures with tunable deformation-dependent Poisson's ratio

With the aid of recent efficient and prior knowledge-free machine learning (ML) algorithms, extraordinary mechanical properties such as negative Poisson's ratio have extensively promoted the diverse designs of metamaterials with distinctive cellular structures. However, most existing ML approaches applied to the design of metamaterials are primarily based on a single property value with the assumption that the Poisson's ratio of a material is stationary, neglecting the dynamic variability of Poisson's ratio, termed deformation-dependent Poisson's ratio, during the loading process that a metamaterial other than conventional materials may experience. This paper first proposes a crystallographic symmetry-based methodology to build 2D metamaterials with complex but patterned topological structures, and then converts them into computational models suitable for molecular dynamics simulations. Then, we employ an integrated approach, consisting of molecular dynamics simulations capable of generating and collecting a large dataset for training/validation, in addition to ML algorithms (CNN and Cycle-GAN) able to predict the dynamic characteristics of Poisson's ratio and offer the inverse design of a metamaterial structure based on a target quasi-continuous Poisson's ratio-strain curve, to eventually unravel the underlying mechanism and design principles of 2D metamaterial structures with tunable Poisson's ratio. The close match between the predefined Poisson's ratio response and that from the generated structure validates the feasibility of the proposed ML model. Owing to the high efficiency and complete independence from prior knowledge, our proposed approach offers a novel and robust technique for the prediction and inverse design of metamaterial structures with tailored deformation-dependent Poisson's ratio, an unprecedented property attractive in flexible electronics, soft robotics, and nanodevices.

Organic ultrathin nanostructure arrays: materials, methods and applications

Organic ultrathin semiconductor nanostructures have attracted continuous attention in recent years owing to their excellent charge transport capability, favorable flexibility, solution-processability and adjustable photoelectric properties, providing opportunities for next-generation optoelectronic applications. For integrated electronics, organic ultrathin nanostructures need to be prepared as large-area patterns with precise alignment and high crystallinity to achieve organic electronic devices with high performance and high throughput. However, the fabrication of organic ultrathin nanostructure arrays still remains challenging due to uncontrollable growth along the height direction in solution processes. In this review, we first introduce the properties, assembly methods and applications of four typical organic ultrathin nanostructures, including small molecules, polymers, and other organic-inorganic hybrid materials. Five categories of representative solution-processing techniques for patterning organic micro- and nanostructures are summarized and discussed. Finally, challenges and perspectives in the controllable preparation of organic ultrathin arrays and potential applications are featured on the basis of their current development.

Polymers based on thieno[3,4-c]pyrrole-4,6-dione and pyromellitic diimide by CH–CH arylation reaction for high-performance thin-film transistors

Three homopolymers were successfully synthesized by direct CH–CH arylation polymerization of thieno[3,4-c]pyrrole-4,6-dione or pyromellitic diimide derivatives affording highly purified polymers with high molecular weights (43.0–174.7 K). Thieno[3,4-c]pyrrole-4,6-dione and pyromellitic diimide derivatives are considered as electron-withdrawing units. The synthesized homopolymers P1, P2, and P3 showed band gaps in the range of 2.13–2.08 eV, respectively. The electron mobilities of the three homopolymers have been investigated. The thin film transistor for P1 prepared by the eutectic-melt-assisted nanoimprinting method achieved an electron mobility of 2.11 × 10⁻³ cm² s⁻¹ V⁻¹. Based on the obtained results, the synthesized polymers can be used as potential electron acceptors in solar cell applications.

The homopolymers P1, P2 and P3 were successfully synthesized by direct CH–CH arylation polymerization in an eco-friendly one-step coupling reaction. They present n-type properties for potential applications as acceptor polymers.