A new optical touchless positioning interface based on ultrasensitive humidity responsive 1D photonic crystals utilizing the giant moisture dependent swelling capacity of 2D phosphatoantimonate nanosheets is presented. The spatially confined, full spectral color change combined with reversible transparency switching induced by the humidity sheath of a human finger allows for real time, true color lateral finger motion tracking under touchless conditions.

An approach toward intercalant tunable nanosheet-based Fabry-Pérot sensors is presented. The intercalant tetrabutylammonium significantly increases the sensitivity of the photonic nose sensor to volatile organic compounds with increasing polarity, enabling polarity-driven color-coded vapor differentiation. Paired with the improved millisecond response times for polar vapors, vapor imaging with spatio-temporal resolution is within reach.

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Rapid progress in the synthesis of nanostructures with tailor-made morphologies necessitates adequate analytical tools to unravel their physical properties. In our study, we investigate, on the nanometer scale, the band gap of individual [TBA x H1–x ]+[Ca2Nb3O10]− nanosheets obtained through intercalation–exfoliation of the layered bulk phase KCa2Nb3O10 with tetra-n-butyl­ammonium hydroxide (TBAOH) using valence electron energy loss spectroscopy (VEELS) in the scanning transmission electron microscope (STEM). The nanosheets consist of an anionically charged perovskite layer with cationic organic ligands surrounding it. Because of the hybrid nature, a careful acquisition and analysis protocol is required since the nanosheets disintegrate easily under electron beam irradiation. The VEELS data reveal a fundamental band gap of an individual freely suspended perovskite nanosheet to be 2.9 ± 0.2 eV and optically allowed transitions above 3.8 ± 0.2 eV (optical band gap). The spatial resolution of the measurements is about 9 nm, taking into account 50% of the excitations when illuminating with an incident electron beam of 1 nm diameter. Our investigations reveal that the band gap of an individual nanosheet is not changed significantly compared to the bulk phase, which is confirmed by UV–vis data. This is rationalized by the quasi-2D electronic structure of the bulk material being preserved upon delamination.

Abstract.We report the high-pressure synthesis and the structure of aluminum hexathiohypodiphosphate, Al 4 (P 2 S 6 ) 3 , along with the redetermination of the structures of two modifications of AlPS 4 . Al 4 (P 2 S 6 ) 3 crystallizes in the monoclinic space group C2 with a = 17.584(3), b = 10.156(2), c = 6.698(1) Å, β = 106.93(1)°in a superstructure of the layered FePS 3 structure type with tripled a axis. Hereby, Al 3+ occupies 2/3 of the Fe 2+ sites in an ordered fashion. The

A 2D nanosheet-based photonic nose for vapor identification is presented. A HSbP2 O8 nanosheet thin-film sensor with resistive readout is developed for the tracking of trace amounts of water, and a photonic HSbP2 O8 /TiO2 multilayer structure is effective at optically distinguishing between chemically similar solvent vapors through analyte-specific host-guest interactions.

In the system Ge-Sn-Sb-Te, there is a complete solid solution series between GeSb2Te4 and SnSb2Te4. As Sn2Sb2Te5 does not exist, Sn can only partially replace Ge in Ge2Sb2Te5; samples with 75% or more Sn are not homogeneous. The joint refinement of high-resolution synchrotron data measured at the K-absorption edges of Sn, Sb and Te combined with data measured at off-edge wavelengths unambiguously yields the element distribution in 21R-Ge(0.6)Sn(0.4)Sb2Te4 and 9P-Ge(1.3)Sn(0.7)Sb2Te5. In both cases, Sb predominantly concentrates on the position near the van der Waals gaps between distorted rocksalt-type slabs whereas Ge prefers the position in the middle of the slabs. No significant antisite disorder is present. Comparable trends can be found in related compounds; they are due to the single-side coordination of the Te atoms at the van der Waals gap, which can be compensated more effectively by Sb(3+) due to its higher charge in comparison to Ge(2+). The structure model of 21R-Ge(0.6)Sn(0.4)Sb2Te4 was confirmed by high-resolution electron microscopy and electron diffraction. In contrast, electron diffraction patterns of 9P-Ge(1.3)Sn(0.7)Sb2Te5 reveal a significant extent of stacking disorder as evidenced by diffuse streaks along the stacking direction. The Seebeck coefficient is unaffected by the Sn substitution but the thermal conductivity drops by a factor of 2 which results in a thermoelectric figure of merit ZT = ~0.25 at 450 °C for both Ge(0.6)Sn(0.4)Sb2Te4 and Ge(1.3)Sn(0.7)Sb2Te5, which is higher than ~0.20 for unsubstituted stable layered Ge-Sb-Te compounds.

Harvesting the properties of nanosheets is not only crucial from af undamental perspective,b ut also for the development of novel functional devices based on 2D nanosheets.H erein, we demonstrate the processing of organically modified TBA x H 1Àx Ca 2 Nb 3 O 10 nanosheets into photonic thin films and study their colorimetric sensing properties in response to various aqueous and organic solvent vapors. Building on the enhanced solvent accessibility of TBAcontaining nanosheets and their photocatalytic activity under UV irradiation, we develop an ew concept for photocatalytic lithography using TBA x H 1Àx Ca 2 Nb 3 O 10 nanosheets as an egative photoresist to obtain high-fidelity micron-scale patterns of robust inorganic nanosheets.P hotocatalytic nanosheet lithography (PNL) therefore adds anew resist-free,resource efficient direct patterning technique to the toolbox of photolithography.Recently,calcium niobate nanosheets derived from the Dion-Jacobson-type perovskite HCa 2 Nb 3 O 10 have developed into an ubiquitous building block for nanoarchitectonics, [1] nanoelectronics, [2] and beyond [3] owing to their high structural definition and aspect ratio as well as their easy accessibility and handling. [2c, 4] Amongst others,c alcium niobate nanosheets have been deployed as 2D building blocks in artificial heterostructures, [4,5] as electron transport materials in solar cells [3d] and photocatalysts, [3a-c] or as ultrathin high-k capacitors or gate insulators. [2] Following pioneering work by Sasaki and Mallouk on the exfoliation and utilization of 2D oxide nanosheets, [1a-c,6] Osterloh and co-workers demonstrated the vast potential of calcium niobate nanosheet suspensions in photocatalytic water splitting. [3a,b] While the large-band gap Ca 2 Nb 3 O 10 À semiconductor nanosheets (E g = 3.5-3.6 eV) [3a, 7] produce hydrogen from pure water, the decomposition of n-tetrabutylammonium (TBA), which is commonly used as an exfoliation agent, is another fingerprint of the photoactivity of calcium niobate under UV-illumination in air.[3b] Similar observations for titania nanosheets modified with organic cations were reported by Sasaki and co-workers earlier.[8] This photodegradation of organic counterions was later used to pattern graphene oxide/PDDA/titania multilayer or titania thin films on the millimeter or hundreds of micron scale, respectively,u sing as hadow mask.[9] However,b eing able to precisely sculpture nanosheet architectures with feature sizes smaller than 100 microns is highly desired for applications in integrated microelectronic circuits due to the ever increasing need for miniaturization.[2b, 10] Recent attempts to pattern nanosheet thin films on the mm-scale were based on MoS 2 , [10] reduced graphene oxide (rGO), [11] or graphene oxide (GO).[12] In these approaches the patterns are either obtained by laser patterning or by electrochemical microstamping. [10][11][12] However,n one of these latter methods utilizes the intrinsic properties of the nanosheets for pattern creation, and all...