Giant In-Plane Flexoelectricity and Radial Polarization in Janus IV-VI Monolayers and Nanotubes

Nanotubes have established a new paradigm in nanoscience because of their atomically thin geometries and intriguing properties. However, because of their typical metastability compared to their 2D and 3D counterparts, it is still fundamentally challenging to synthesize nanotubes with controlled size. New strategies have been suggested for synthesizing nanotubes with a controlled geometry. One of these is considering Janus 2D layers, which can self-roll to form a nanotube. Herein, we study 412 nanotubes (along the armchair and zigzag directions) based on 36 Janus IV-VI compounds using density functional theory (DFT) calculations. By investigating the energy-radius relationship using structural models and Bayesian predictions, the most stable nanotubes show negative strain energies and radii below 20 Å, where curvature effects can play a significant role. The band structures show that the selected nanotubes exhibit sizable band gaps and size-dependent electronic properties. More strikingly, the flexoelectricity along the in-plane directions and radial directions in these nanotubes is significantly larger than that in other nanotubes and their 2D counterparts. This work opens up an avenue of structure-property relationships of Janus IV-VI nanotubes and demonstrates giant flexoelectricity in these nanotubes for future electronic and energy applications.

Non-Classical Self-Assembly of Anisotropic Magneto-Organosilica Janus Particles Possessing Surfactant Properties and the Field-Triggered Breakdown of Surface Activity and Amphiphilic Properties

Using colloidal particles as models to understand processes on a smaller scale is a precious approach. Compared to molecules, particles are less defined, but their architecture can be more complex and so is their long-range interaction. One can observe phenomena that are unknown or much more difficult to realize on the molecular level. The current paper focuses on particle-based surfactants and reports on numerous unexpected properties. The main goal is creating an amphiphilic system with responsiveness in surface activity and associated self-organization phenomena depending on applying an external trigger, preferably a physical field. A key step is the creation of a Janus-type particle characterized by two types of dipoles (electric and magnetic) which geometrically stand orthogonal to each other. In a field, one can control which contribution and direction dominate the interparticle interactions. As a result, one can drastically change the system's properties. The features of ferrite-core organosilica-shell particles with grain-like morphology modified by click chemistry are studied in response to spatially isotropic and anisotropic triggers. A highly unusual aggregation-dissolution-reaggregation sequence w as discovered. Using a magnetic field, one can even switch off the amphiphilic properties and use this for the field-triggered breaking of multiphase systems such as emulsions.

Confined Growth of Silver-Copper Janus Nanostructures with {100} Facets for Highly Selective Tandem Electrocatalytic Carbon Dioxide Reduction

Electrocatalytic carbon dioxide reduction reaction (CO₂ RR) holds significant potential to promote carbon neutrality. However, the selectivity toward multicarbon products in CO₂ RR is still too low to meet practical applications. Here the authors report the delicate synthesis of three kinds of Ag-Cu Janus nanostructures with {100} facets (JNS-100) for highly selective tandem electrocatalytic reduction of CO₂ to multicarbon products. By controlling the surfactant and reduction kinetics of Cu precursor, the confined growth of Cu with {100} facets on one of the six equal faces of Ag nanocubes is realized. Compared with Cu nanocubes, Ag₆₅ -Cu₃₅ JNS-100 demonstrates much superior selectivity for both ethylene and multicarbon products in CO₂ RR at less negative potentials. Density functional theory calculations reveal that the compensating electronic structure and carbon monoxide spillover in Ag₆₅ -Cu₃₅ JNS-100 contribute to the enhanced CO₂ RR performance. This study provides an effective strategy to design advanced tandem catalysts toward the extensive application of CO₂ RR.

Janus Nanostructures from ABC/B Triblock Terpolymer Blends

Lamella-forming ABC triblock terpolymers are convenient building blocks for the synthesis of soft Janus nanoparticles (JNPs) by crosslinking the B domain that is "sandwiched" between A and C lamellae. Despite thorough synthetic variation of the B fraction to control the geometry of the sandwiched microphase, so far only Janus spheres, cylinders, and sheets have been obtained. In this combined theoretical and experimental work, we show that the blending of polybutadiene homopolymer (hPB) into lamella morphologies of polystyrene-block-polybutadiene-block-polymethylmethacrylate (SBM) triblock terpolymers allows the continuous tuning of the polybutadiene (PB) microphase. We systematically vary the volume fraction of hPB in the system, and we find in both experiments and simulations morphological transitions from PB-cylinders to perforated PB-lamellae and further to continuous PB-lamellae. Our simulations show that the hPB is distributed homogeneously in the PB microdomains. Through crosslinking of the PB domain and redispersion in a common solvent for all blocks, we separate the bulk morphologies into Janus cylinders, perforated Janus sheets, and Janus sheets. These studies suggest that more complex Janus nanostructures could be generated from ABC triblock terpolymers than previously expected.

Pt/TiSi x-NCNT Novel Janus Nanostructure: A New Type of High-Performance Electrocatalyst

Novel Janus nanostructured electrocatalyst (Pt/TiSi _x-NCNT) was prepared by first sputtering TiSi _x on one side of N-doped carbon nanotubes (NCNTs), followed by wet chemical deposition of Pt nanoparticles (NPs) on the other side. Transmission electron microscopy (TEM) studies showed that the Pt NPs are mainly deposited on the NCNT surface where no TiSi _x (i.e., between the gaps of TiSi _x film). This feature could benefit the increase in the stability of the Pt NP catalyst. Indeed, compared to the state-of-the-art commercial Pt/C catalyst, this novel Pt/TiSi _x-NCNT Janus structure showed ∼3 times increase in stability as well as significantly improved CO tolerance. The obvious performance enhancement could be attributed to the better corrosion resistance of TiSi _x and NCNTs than the carbon black that is used in the commercial Pt/C catalyst. Pt/TiSi _x-NCNT Janus nanostructures open the door for designing new type of high-performance electrocatalyst for fuel cells and other oxygen reduction reaction-related energy devices.