Functional Materials

Functional materials convert one form of energy into another or change their properties in response to external stimuli. Two-dimensional monochalcogenides (for example SnS, SnSe, GeS, GeSe) exploit quantum confinement and anisotropic crystal lattices to deliver tunable direct bandgaps, large exciton binding energies and polarisation-selective absorption for photonic and valleytronic devices. Thermoelectric monochalcogenide monolayers exhibit high figures of merit (ZT>2) by combining low lattice thermal conductivity with enhanced electrical conductivity and Seebeck coefficients. Stretchable polymer semiconductors integrate randomly distributed co-monomers or in-situ rubber matrices to achieve high charge-carrier mobilities (≈0.2 cm² V⁻¹ s⁻¹) under 100% biaxial strain by balancing entropic and enthalpic energy dissipation. Dynamic infrared materials, including aluminium-doped zinc oxide nanocrystals and phase-change metamaterials, modulate emissivity between 0.05 and 0.5 across mid- and long-wave bands within sub-second response times, enabling smart thermal management and camouflage. Graphene and metal-oxide metasurfaces extend functional materials to the terahertz regime, where ultrahigh-Q Fabry–Pérot spoof-plasmon resonances and electromagnetically induced transparency afford spectral sensitivities above 2 THz RIU⁻¹ and sub-micrometre film-thickness resolution.

Research from Nature Portfolio

A comprehensive study of ambient degradation in mechanically exfoliated group-VI and group-III monochalcogenides reveals that Se-containing layers oxidise and amorphise within days, whereas GaS retains crystallinity for over three weeks. Operando Raman and photoluminescence identify edge-initiated amorphous ring formation, guiding surface-passivation strategies for 2D semiconductor devices. Parallel work demonstrates visible-transparent aluminium-doped zinc oxide nanocrystal films with independent electrical control of carrier concentration in surface depletion layers. These regulators achieve 84.7% visible transmittance and emissivity tuning from 0.05 to 0.56 in the mid-infrared (3–5 µm) with response times under 600 ms and lifetimes exceeding 10,000 cycles for adaptive thermal camouflage.

Research from all publishers

Flame-assisted ultrafast synthesis of sulfur- and nitrogen-doped hard carbon nanosheets produces high-surface-area anodes for sodium-ion batteries, delivering reversible capacities above 540 mAh g⁻¹ at 0.1 A g⁻¹ and 236 mAh g⁻¹ after 1,200 cycles at 2 A g⁻¹; density functional theory attributes performance gains to enhanced Na⁺ adsorption and migration. A van der Waals graphene transfer technique achieves large-area, additive-free films on polymers with sheet resistances near 93 Ω sq⁻¹. These films yield over 90% modulation of mid-infrared reflectivity under low‐voltage bias, offering scalable, durable platforms for flexible electro-optical thermal camouflage. Moreover, single-pixel reconfigurable graphene metasurfaces enable ultra-wideband (1.5 THz) terahertz fingerprint sensing with detection limits below 1 µg mm⁻² and signal enhancements up to 17 dB via electromagnetically induced transparency, supported by inversion models to restore molecular spectra with ≥0.99 fidelity.

Functional Materials publication trend

The graph below shows the total number of articles in functional materials across all publications each year (not limited to Nature Index journals).

Technical terms

Monochalcogenide: A two-dimensional semiconductor formed by pairing group-IV and group-VI elements in an orthorhombic lattice, offering direct bandgaps and anisotropic optoelectronic responses.

Depletion layer: A near-surface region in a doped semiconductor depleted of free carriers, whose thickness and carrier density control optical emissivity under bias.

Emissivity: The ratio of thermal radiation emitted by a surface to that of a perfect blackbody at the same temperature, ranging from 0 (reflective) to 1 (ideal emitter).

Hard carbon: A micro/mesoporous, predominantly amorphous carbon characterized by disordered graphitic domains, high surface area and reversible alkali-ion storage.

Van der Waals film: An assembly of atomically thin layers held together by weak interlayer forces, enabling additive-free transfer of two-dimensional materials onto arbitrary substrates.

Electromagnetically induced transparency (EIT): A narrow resonance window created in metamaterials by destructive interference between adjacent resonant modes, providing sharp spectral features for sensing.

References

1. Thermoelectric and phonon transport properties of two-dimensional IV–VI compounds. Scientific Reports (2017).
2. Stability of mechanically exfoliated layered monochalcogenides under ambient conditions. Scientific Reports (2023).
3. Transparent dynamic infrared emissivity regulators. Nature Communications (2023).
4. Flame‐assisted ultrafast synthesis of functionalized carbon nanosheets for high‐performance sodium storage. Carbon Energy (2024).
5. Scalable van der Waals graphene films for electro‐optical regulation and thermal camouflage. InfoMat (2023).
6. Ultra-wideband terahertz fingerprint enhancement sensing and inversion model supported by single-pixel reconfigurable graphene metasurface. PhotoniX (2024).
7. Highly stretchable polymer semiconductor thin films with multi-modal energy dissipation and high relative stretchability. Nature Communications (2023).