Janus Material Research Articles

Unconventional Janus Properties of Enokitake-like Gold Nanowire Films.

We report on unconventional Janus material properties of vertically aligned gold nanowire films that conduct electricity and interact with light and water in drastically different ways on its two opposing sides. These Janus-like properties originate from enokitake-like nanowire structures, causing the nanoparticle side ("head") to behave like bulk gold, yet the opposing nanowire side ("tail") behaves as discontinuous nanophases. Due to this Janus film structure, its head side is hydrophilic but its tail side is hydrophobic; its head side reflects light like bulk gold, yet its tail side is a broadband superabsorber; its tail side is less conductive but with tunable resistance. More importantly, the elastomer-bonded Janus film exhibits unusual mechatronic properties when being stretched, bent, and pressed. The tail-bonded elastomeric sheet can be stretched up to ∼800% strain while remaining conductive, which is about 10-fold that of head-bonded film. In addition, it is also more sensitive to bending forces and point loads than the corresponding tail-bonded film. We further demonstrate the versatility of nanowire-based Janus films for pressure sensors using bilayer structures in three different assembly layouts.

Intercalated Chevrel Phase Mo6S8 as a Janus Material for Energy Generation and Storage

An approach to designing solar absorber materials based on an intercalation-induced metal-to-semiconductor transition has been proposed. Using a hybrid density functional calculation, Al-intercalated Chevrel phase Mo6S8 with end product Al4/3Mo6S8 is predicted to be a semiconductor with a 1.18 eV indirect band gap. Compared with GaAs and Si, Al4/3Mo6S8 shows significantly higher optical absorption over the solar spectrum as a result of the parallel bands across the band gap with direct transitions around 1.35 eV, nearly ideal for an absorber material in a solar cell. Chevrel phase Mo6S8 has recently been explored as a cathode material in rechargeable Al-ion batteries. Thus, Al4/3Mo6S8 is a potential dual-function (or Janus) material for both energy generation and storage. A possible device structure utilizing this unique property has been proposed.

Pseudo-Janus Zn/Al-based nanocomposites for Cr(VI) sorption/remediation and evolved photocatalytic functionality

An ingenious strategy for the recycling of Cr(VI)-enriched sorbents is presented herein. These adsorbents, which are Zn/Al-based nanocomposites with a Zn to Al ratio of 4:1, have shown great promise as a type of “Janus material” in which they not only behave as a sorbent, but a photocatalytic function can be evolved by calcination. The Zn/Al composite sorbents were prepared via a co-precipitation method followed by calcination at 500°C to show good removal capacity for Cr(VI) even after repeated absorption cycles. The Cr(VI)-saturated adsorbent could then be transduced to a highly crystallized Cr(VI)-containing ZnO/ZnAl2O4 nanocomposite by calcination at 900°C. It was found that the resultant Cr(VI)-containing ZnO/ZnAl2O4 nanocomposites possess a photocatalytic performance that is very similar to titania P25 and not compromised by the co-localization of Cr(VI). In fact, the adsorbed Cr(VI) is sufficiently well bound to not easily release into aqueous medium, while also, it can be serendipitously photo-reduced to a less toxic valency, i.e., Cr(III), after the application of the nanocomposites as a photocatalyst. Therefore, the nanocomposites exhibit a very promising Janus-like chemical behavior as exhibited by absorption of highly toxic Cr(VI) and subsequent evolved photocatalysis and remediation of Cr(VI) to Cr(II).

Highly efficient phase transfer catalyst supported on Janus composite particles: Synthesis, characterization, and applications

Abstract

Utilisation of janus material for controllable formation of graphene p–n junctions and superlattices

Graphene-based device applications such as ultrafast transistors and photodetectors benefit from precise control over its carrier type and concentration as well as a combination of both high-quality p- and n-doped components with spatial control and seamless connection (p–n junctions/superlattices). However, this remains experimentally a challenge for an atom-scale control over the doping in graphene and the attendant formation of p–n junctions/superlattices. Here, we demonstrate that sandwiching a janus material (a functionalized graphene layer with one side by H atoms and another side by F atoms, defined as H–G–F) between MoSe2 (BN) substrate and graphene allows us to effectively control the carrier type in graphene, where the janus material acts as an electron pump, facilitating the electron tunneling between MoSe2 (BN) and graphene. Appropriate functionalization of the janus material would open the possibility of creating well ordered and atomically sharp graphene p–n junctions/superlattices in a single layer of graphene. Furthermore, upon applying an external electric field, the charge concentration in both n-type and p-type regions can be continuously tuned except for a platform area. A comprehensive and detailed picture built by density functional theory calculations sheds light on the physical mechanism of the observed doping course as well as its response to an external field. Our results not only introduce single-layer H–G–F as a new 2D Janus material with the ability of electron extraction, but also open up a new direction for local control over the properties of graphene without destroying its intrinsic structure.

A three-headed Janus material

Switchable molecular materials generally alternate between two different states that are both stable in identical conditions. A magnetic molecular system is now available that allows switching between three different phases of the same compound.

Nanostructured carbons in catalysis a Janus material—industrial applicability and fundamental insights

Nanostructured carbons especially carbon nanotubes and carbon nanofibers are Janus materials. As will be shown in this review one side of the Janus face is looking towards industrial applications. The availability of the materials is ever increasing and they can be produced at conditions which should make them profitable. Moreover their physical properties can be modified in such a way that application is viable. The other side of the face is looking towards fundamental understanding of heterogeneous catalysis. Insights in particle size and confinement effects emerged in the last few year using nanostructured carbon as a catalyst support. The carbons itself are effective oxidation and, after nitrogen incorporation, base catalysts. Examples will be discussed in this review.