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Two-dimensional (2D) materials including graphene, transition metal dichalcogenides, black phosphorus, MXenes, and semimetals have attracted extensive and widespread interest over the past years for their many intriguing properties and phenomena, underlying physics, and great potential for applications. The vast library of 2D materials and their heterostructures provides a diverse range of electrical, photonic, mechanical, and chemical properties with boundless opportunities for photonics and plasmonic devices. The infrared (IR) regime, with wavelengths across 0.78 μm to 1000 μm, has particular technological significance in industrial, military, commercial, and medical settings while facing challenges especially in the limit of materials. Here, we present a comprehensive review of the varied approaches taken to leverage the properties of the 2D materials for IR applications in photodetection and sensing, light emission and modulation, surface plasmon and phonon polaritons, non-linear optics, and Smith-Purcell radiation, among others. The strategies examined include the growth and processing of 2D materials, the use of various 2D materials like semiconductors, semimetals, Weyl-semimetals and 2D heterostructures or mixed-dimensional hybrid structures, and the engineering of light-matter interactions through nanophotonics, metasurfaces, and 2D polaritons. Finally, we give an outlook on the challenges in realizing high-performance and ambient-stable devices and the prospects for future research and large-scale commercial applications. Agency for Science, Technology and Research (A*STAR) National Research Foundation (NRF) This work is partially supported by the National Research Foundation, Singapore, under its CRP program (NRF-CRP26- 2021-0004) and A*STAR AME IRG (A20E5c0084). Z.L. acknowledges the support from PHC Merlion Program 2020. L.W. gratefully acknowledges the Start-Up Research Grant from the Singapore University of Technology and Design via Grant No. SRG SMT 2021 169, and National Research Foundation Singapore via Grant Nos. NRF2021-QEP2-02-P03 and NRF2021-QEP2-03-P09. Y.L. acknowledges the support from A*STAR Career Development Fund - Seed Projects (C222812008). M.Z. acknowledges the support from A*STAR Career Development Fund (C210812027).

Superlattices-a periodic stacking of two-dimensional layers of two or more materials-provide a versatile scheme for engineering materials with tailored properties1,2. Here we report an intrinsic heterodimensional superlattice consisting of alternating layers of two-dimensional vanadium disulfide (VS2) and a one-dimensional vanadium sulfide (VS) chain array, deposited directly by chemical vapour deposition. This unique superlattice features an unconventional 1T stacking with a monoclinic unit cell of VS2/VS layers identified by scanning transmission electron microscopy. An unexpected Hall effect, persisting up to 380 kelvin, is observed when the magnetic field is in-plane, a condition under which the Hall effect usually vanishes. The observation of this effect is supported by theoretical calculations, and can be attributed to an unconventional anomalous Hall effect owing to an out-of-plane Berry curvature induced by an in-plane magnetic field, which is related to the one-dimensional VS chain. Our work expands the conventional understanding of superlattices and will stimulate the synthesis of more extraordinary superstructures. Ministry of Education (MOE) National Research Foundation (NRF) Submitted/Accepted version The work was supported by: the National Key R&D Program of China (grant number 2020YFA0308800), the NSF of China (grant numbers 12074009, 11774009, 62174013, 12061131102 and 11734003), BIT (number 2021CX11013) and the National Key R&D Program of China (2017YFA0206301); the National Research Foundation, Singapore, under its Competitive Research Programme (NRF-CRP22-2019-0007 and NRF-CRP22-2019-0004), under its NRF-ISF joint research programme (NRF2020-NRF-ISF004-3520); and the Ministry of Education, Singapore, under its AcRF Tier 3 Programme ‘Geometrical Quantum Materials’ (MOE2018-T3-1-002). H.D., and W.G. acknowledge funding from the National Key Basic Research Program of China (2017YFB0701603) and NSFC (number 51971037). We thank X. Dai and H. M. Weng for discussions and their preliminary attempts on ab initio calculations. Y.-C.L. and K.S. acknowledge the JSPS-KAKENHI (JP16H06333 and JP22H05478), (18K14119), the JST-CREST programme (JPMJCR20B1, JMJCR20B5 and JPMJCR1993), the JSPS A3 Foresight Program, and the Kazato Research Encouragement Prize. Y.G. acknowledges funding from the Innovation Program of Shanghai Municipal Education Commission (number 2019-01-07-00- 09-E00020), Shanghai Municipal Science and Technology Commission (18JC1412800). Jianhui Zhou was supported by the High Magnetic Field Laboratory of Anhui Province. Yugui Yao acknowledges the Strategic Priority Research Program of Chinese Academy of Sciences (grant number XDB30000000).

Two-dimensional (2D) materials with multiphase, multielement crystals such as transition metal chalcogenides (TMCs) (based on V, Cr, Mn, Fe, Cd, Pt and Pd) and transition metal phosphorous chalcogenides (TMPCs) offer a unique platform to explore novel physical phenomena. However, the synthesis of a single-phase/single-composition crystal of these 2D materials via chemical vapour deposition is still challenging. Here we unravel a competitive-chemical-reaction-based growth mechanism to manipulate the nucleation and growth rate. Based on the growth mechanism, 67 types of TMCs and TMPCs with a defined phase, controllable structure and tunable component can be realized. The ferromagnetism and superconductivity in FeXy can be tuned by the y value, such as superconductivity observed in FeX and ferromagnetism in FeS2 monolayers, demonstrating the high quality of as-grown 2D materials. This work paves the way for the multidisciplinary exploration of 2D TMPCs and TMCs with unique properties. Ministry of Education (MOE) National Research Foundation (NRF) Submitted/Accepted version This work was supported by the National Key R&D Program of China (grant no. 2020YFA0308800) and the NSF of China (grant nos. 62174013, 11504046 12061131002 and 11734003). This work was also supported by the National Research Foundation— Competitive Research Program (NRF-CRP22-2019-0007, NRF-CRP21-2018-0007 and NRF2020-NRF-ISF004-3520). This work was also supported by the Singapore Ministry of Education Tier 3 Programme ‘Geometrical Quantum Materials’ (MOE2018-T3-1-002), AcRF Tier 2 (MOE2019-T2-2-105) and AcRF Tier 1 RG161/19 and RG7/21. W.B.G. acknowledges the support of NRF CRP by NRF-CRP22-2019-0004. G.L. and L. Lu acknowledge fundings from the National Natural Science Foundation of China under grant numbers 92065203 and 11874406, and the Strategic Priority Research Program of the Chinese Academy of Sciences (grant no. XDB33010300). Y.Y. was supported by the National Key R&D Program of China (grant no. 2016YFA0300600). C.Z. acknowledges the Fundamental Research Funds for the central Universities. F.D. and J.D. acknowledge funding from the Institute for Basic Science, Republic of Korea (IBS‐R019‐D1) and the use of the IBS‐CMCM high‐performance computing system Cimulator. This work was also supported by the Innovation Program of Shanghai Municipal Education Commission (no. 2019-01-07-00-09-E00020) and Shanghai Municipal Science and Technology Commission (18JC1412800). Y.-C.L. and K.S. acknowledge JSPS-KAKENHI (JP16H06333 and 18K14119), JSPS A3 Foresight Program and Kazato Research Encouragement Prize. H. Yang acknowledges funding from the Chinese Academy of Sciences (grant nos. XDB33030100). Y.Y. acknowledges the Strategic Priority Research Program of the Chinese Academy of Sciences (grant no. XDB30000000).

In recent years, two-dimensional (2D) magnetic transition metal chalcogenides (TMCs) have attracted tremendous research interests thanks to their intriguing properties that are essential in developing future electronic and spintronic devices in this modernizing era. This review aims to introduce recent developments in the preparation of 2D magnetic TMCs, especially chromium and iron-based chalcogenides, their structures, as well as the related intriguing magnetic phenomena. First, the common crystal structures of magnetic TMCs including both layered and nonlayered structures are introduced. Various chemical vapor deposition strategies for synthesizing 2D magnetic TMCs are then introduced with emphasis on the key synthesis parameters. Moreover, the intriguing physical properties associated with 2D TMCs such as magnetic anisotropy, thickness, and phase-dependent magnetic response as well as stability are summarized. Last but not least, challenges and future research directions are briefly discussed in light of recent advances in the field. Ministry of Education (MOE) National Research Foundation (NRF) Submitted/Accepted version Z.L. acknowledges support from National Research Foundation Singapore Programme Grants NRF-CRP22-2019-0007, NRF-CRP21-2018-0007, and NRF-CRP22-2019-0004. This research is also supported by the Ministry of Education, Singapore, under its AcRF Tier 3 Programme “Geometrical Quantum Materials” (Grant MOE2018-T3-1-002), and AcRF Tier 1 Grant RG161/19.

Single-metal-atom chains (SMACs), as the smallest one-dimensional structure, have intriguing physical and chemical properties. Although several SMACs have been realized so far, their controllable fabrication remains challenging due to the need to arrange single atoms in an atomically precise manner. Here we develop a chemical vapour co-deposition method to construct a wafer-scale network of platinum SMACs in atom-thin films. The obtained atomic chains possess an average length of up to ~17 nm and a high density of over 10 wt%. Interestingly, as a consequence of the electronic delocalization of platinum atoms along the chain, this atomically coherent one-dimensional channel delivers a metallic behaviour, as revealed by electronic measurements, first-principles calculations and complex network modelling. Our strategy is potentially extendable to other transition metals such as cobalt, enriching the toolbox for manufacturing SMACs and paving the way for the fundamental study of one-dimensional systems and the development of devices comprising monoatomic chains. Agency for Science, Technology and Research (A*STAR) Ministry of Education (MOE) National Research Foundation (NRF) Submitted/Accepted version This work was supported by the support from National Research Foundation Singapore programme NRF-CRP22-2019-0007 and NRF-CRP21-2018-0007. This work is also supported by the Ministry of Education, Singapore, under its AcRF Tier 2 (MOE2019-T2-2-105) and AcRF Tier 1 RG4/17 and RG7/18. This research is also supported by A*STAR under its AME IRG Grant (Project No. A2083c0052). The work at NUAA was supported by the National Key Research and Development Program of China (2019YFA0705400), National Natural Science Foundation of China (11772153, 22073048), the Natural Science Foundation of Jiangsu Province (BK20190018), and a Project by the Priority Academic Program Development of Jiangsu Higher Education Institutions. W.Z. acknowledges the support of the Beijing Outstanding Young Scientist Program (BJJWZYJH01201914430039). B.T. and X.W. acknowledge the support from the Ministry of Education, Singapore (MOE2019 T1-001-113). H.Y. and M. N. acknowledge the support from the Hong Kong Research Grant Council, Hong Kong (HKRGC GRF 12300218, 12300519, 17201020, 17300021, and UGC-RMGS 207300829). H.D. acknowledges the support from German Research Foundation (DFG) under the Grant SFB917 Nanoswitches.

Defect states dominate the performance of low-dimensional nanoelectronics, which deteriorate the serviceability of devices in most cases. But in recent years, some intriguing functionalities are discovered by defect engineering. In this work, we demonstrate a bifunctional memory device of a MoS2/BiFeO3/SrTiO3 van der Waals heterostructure, which can be programmed and erased by solely one kind of external stimuli (light or electrical-gate pulse) via engineering of oxygen-vacancy-based solid-ionic gating. The device shows multibit electrical memory capability (>22 bits) with a large linearly tunable dynamic range of 7.1 × 106 (137 dB). Furthermore, the device can be programmed by green- and red-light illuminations and then erased by UV light pulses. Besides, the photoresponse under red-light illumination reaches a high photoresponsivity (6.7 × 104 A/W) and photodetectivity (2.12 × 1013 Jones). These results highlighted solid-ionic memory for building up multifunctional electronic and optoelectronic devices. Agency for Science, Technology and Research (A*STAR) Ministry of Education (MOE) National Research Foundation (NRF) Submitted/Accepted version This research was supported by National Research Foundation Singapore Grants NRF-CRP22-2019-0007 and NRF-CRP21- 2018-0007, Singapore Ministry of Education via AcRF Tier 3 Programme “Geometrical Quantum Materials” (Grant MOE2018-T3-1-002), AcRF Tier 2 (Grant MOE2016-T2-1- 131), and AcRF Tier 1 Grants RG4/17 and RG7/18. This research is also supported by A*STAR under its AME IRG Grant (Project A2083c0052). This work was also financially supported by the National Key R&D Program of China (Grant 2020YFA0309200), the National Natural Science Foundation of China (Grant 62074025), Applied Basic Research Program of Sichuan Province (Grant 2020ZYD014), and Sichuan Province Key Laboratory of Display Science and Technology.

Double perovskites are materials exhibiting excellent properties for a variety of optical and electrical applications. In this paper, we characterize the structural, electronic, optical, electrical and scintillation properties of two variants of lead-bismuth halide double perovskite, with the general chemical composition of Cs4PbBi2X12 (X = Br, I). Density functional theory calculations reveal that the Br- and I-variants have direct and indirect bandgaps, respectively. The Cs4PbBi2X12 perovskites also show a broad emission down to near infrared, suggesting the presence of self trapped excitons. Photoluminescence time-resolved measurements show a very fast decay time with average decay times of 4.1 ns and 0.39 ns, for the Br- and I-variant, respectively. Photodetectors fabricated with the Cs4PbBi2X12 perovskites show clear rectification under bias, and a moderate response to illumination. Due to the presence of very heavy atoms and density of the material, the Cs4PbBi2X12 perovskites are strong X-ray absorbers with attenuation lengths comparable to Gd2O2S, a standard X-ray phosphor. The Cs4PbBi2X12 perovskites also show strong scintillation at cryogenic temperatures below 30 K, but thermal quenching severely reduces the light yield at room temperature. Although the performances of both crystals for photodetectors and scintillators are still low in comparison with some other perovskites, they are still a very promising materials due to their short absorption length and high theoretical maximum light yield, and their optoelectronic properties could be significantly improved by ion doping. Ministry of Education (MOE) The authors acknowledge financial supports from the Ministry of Education (Singapore), under its AcRF Tier 2 grant (MOE-T2EP50121-0012), the MERLION Program, and Thales-CINTRA Funding.

The emission of light from charged particles underlies a wealth of scientific phenomena and technological applications. Classical theory determines the emitted photon energy by assuming an undeflected charged particle trajectory. In 1940, Ginzburg pointed out that this assumption breaks down in quantum electrodynamics, resulting in shifts—known as quantum recoil— in outgoing photon energies from their classically predicted values. Since then, quantum recoil in free-electron light-emission processes, including Cherenkov radiation and Smith–Purcell radiation, has been well-studied in theory, but an experimental demonstration has remained elusive. Here we present an experimental demonstration of quantum recoil, showing that this quantum electrodynamical effect is not only observable at room temperature but also robust in the presence of other electron-scattering mechanisms. By scattering free electrons off the periodic two-dimensional atomic sheets of van der Waals materials in a tabletop platform, we show that the X-ray photon energy is accurately predicted only by quantum recoil theory. We show that quantum recoil can be enormous, to the point that a classically predicted X-ray photon is emitted as an extremely low-energy photon. We envisage quantum recoil as a means of precision control over outgoing photon and electron spectra, and show that quantum recoil can be tailored through a host of parameters: the electron energy, the atomic composition and the tilt angle of the van der Waals material. Our results pave the way to tabletop, room-temperature platforms for harnessing and investigating qua- ntum electrodynamical effects in electron–photon interactions. Agency for Science, Technology and Research (A*STAR) National Research Foundation (NRF) Submitted/Accepted version This project was partially supported by the National Research Foundation (Project ID NRF2020-NRF-ISF004-3525) and the Agency for Science, Technology and Research (A*STAR) Science & Engineering Research Council (Grant No. A1984c0043). We acknowledge the Facility for Analysis, Characterisation, Testing and Simulation, Nanyang Technological University, Singapore, for use of their electron microscopy/X-ray facilities. Z.L. acknowledges the support from National Research Foundation, Singapore, under its Competitive Research Programme (CRP) (NRF-CRP22-2019-0007 and NRF-CRP26-2021-0004). This research is also supported by A*STAR under its AME IRG Grant (Project No. A2083c0052). L.J.W. acknowledges the Nanyang Assistant Professorship Start-up Grant.

Nonlinear optical activities (e.g., harmonic generations) in two-dimensional (2D) layered materials have attracted much attention due to the great promise in diverse optoelectronic applications such as nonlinear optical modulators, nonreciprocal optical device, and nonlinear optical imaging. Exploration of nonlinear optical response (e.g., frequency conversion) in the infrared, especially the mid-infrared (MIR) region, is highly desirable for ultrafast MIR laser applications ranging from tunable MIR coherent sources, MIR supercontinuum generation, and MIR frequency-comb-based spectroscopy to high harmonic generation. However, nonlinear optical effects in 2D layered materials under MIR pump are rarely reported, mainly due to the lack of suitable 2D layered materials. Van der Waals layered platinum disulfide (PtS2) with a sizable bandgap from the visible to the infrared region is a promising candidate for realizing MIR nonlinear optical devices. In this work, we investigate the nonlinear optical properties including third-and fifth-harmonic generation (THG and FHG) in thin layered PtS2 under infrared pump (1550-2510 nm). Strikingly, the ultrastrong third-order nonlinear susceptibility χ(3)(-3ω;ω,ω,ω) of thin layered PtS2 in the MIR region was estimated to be over 10-18 m2/V2, which is about one order of that in traditional transition metal chalcogenides. Such excellent performance makes air-stable PtS2 a potential candidate for developing next-generation MIR nonlinear photonic devices. Ministry of Education (MOE) National Research Foundation (NRF) Submitted/Accepted version This research was also supported partially by National Research Foundation Singapore program (NRFCRP19- 2017-01 and NRF-CRP22-2019-0007) and Ministry of Education Tier 2 program (MOE-T2EP50120-0009), and Singapore A*STAR funding (A18A7b0058 and A2090b0144).

Many applications of photonics require efficient nonlinear optical interactions with low power and small footprints. However, the current needs for long interaction lengths and strong laser sources of nonlinear optical devices make them unsuitable for nanophotonic integrated optics. New materials and devices with stronger nonlinear properties have been developed using various approaches in the past few years. One of the largest nonlinear optical responses reported to date has been realized with engineered intersubband transitions in n-doped multiple quantum wells (MQWs) semiconductors. Here, this work proposes to improve further the nonlinear properties of a MQW heterostructure by tailoring its permittivity to reach near-zero values. Materials with vanishing permittivity, called epsilon-near-zero (ENZ) materials, have exotic nonlinear features which can be explored to achieve this goal. To prove this point, this work makes use of In0.53Ga0.47As/Al0.48In0.52As, designs an ultrathin multilayer structure, and couples the designed structure with metasurfaces. Unprecedented nonlinear efficiency within subwavelength propagation lengths is obtained. Such structure with strong second harmonic generation (SHG) enables efficient frequency conversion, while the tunability offered by the metasurface provides new degrees of freedom to control the amplitude, phase, and polarization of the nonlinear light. Agency for Science, Technology and Research (A*STAR) Ministry of Education (MOE) National Research Foundation (NRF) Published version This work was supported by the Singapore Ministry of Education (MOE2018-T2-2-189(S)), A*Star AME IRG Grant (A20E5c0095) and Programmatic Funds (A18A7b0058), and the National Research Foundation Singapore Competitive Research Program (NRF-CRP22-2019-0006 and NRF-CRP23-2019-0007).

All-inorganic metal halide perovskites, such as CsPbX3 (X = Br, Cl, or I), have attracted significant interest for a new generation of integrated, high-performance optoelectronic devices. To realize the full potential of layer-by-layer devices, perovskite crystal thin films are preferred over crystal ingots, considering carrier loss during carrier transport. The space-confined method is a facile way of fabricating perovskite crystal films in a geometrically confined space to break the isotropic growth. Many researchers have reported effective preparation of large-area perovskite films using this method. However, most space-confined methods require growth in a liquid phase (solution), which can cause uncontrollable nucleation, surface traps, and unsatisfactory device performance. In this work, a pure solid-state space-confined strategy to grow CsPbBr3 films for the first time without relying on solution conditions is developed. The regular shapes of CsPbBr3 films prepared by this solid-state space-confined strategy can function as effective multimode and single-mode Fabry–Perot (F–P) microlasers under optical pumping. This work overcomes the challenge that the conventional space-confined method can only be adapted to the liquid phase. It also opens a new approach for making high-quality microlasers, which are significant for photonic integrated circuits and optoelectronic devices. Agency for Science, Technology and Research (A*STAR) National Research Foundation (NRF) Submitted/Accepted version The authors acknowl-edge support from A*Star-AME-IRG 192E5012-S, NRF-CRP23-2019-0007,NRF-CRP19-2017-01, and LUX Seed Grant 2021LUX02P01.

2D ferromagnets have garnered considerable attention for their potential applications in spintronics, magnonics, and spin-orbitronics. Chromium tellurides (CrxTey), in particular, have drawn interest due to their exceptional magnetic properties and diverse range of chemical stoichiometries, attributed to the phenomenon of chromium self-intercalation. To provide an in-depth understanding of this complex material class, this review first explains the origin of 2D magnetism using two well-known 2D ferromagnets, CrI3 and Fe3GeTe2, and compares the structures of CrTe2, Cr5Te8, Cr2Te3, and CrTe to clarify the self-intercalation phenomenon. In addition, it summarizes the growth conditions of CrxTey using the chemical vapor deposition approach as well as commonly practiced characterization techniques for 2D ferromagnetism. This review also compares ferromagnetic properties while analyzing how Cr intercalants affect the magnetic. Finally, it suggests that more attention should be focused on this material system to unlock its full practical and academic potential, and proposes directions for future research. Agency for Science, Technology and Research (A*STAR) National Research Foundation (NRF) Published version Z.L. acknowledges the support from National Research Foundation, Singapore, under its Competitive Research Program (CRP) (NRF-CRP22-2019-0007 and NRF-CRP22-2019-0004), under its NRF-ISF joint research program (NRF2020-NRF-ISF004-3520). This research is also supported by A*STAR under its AME IRG Grant (Project No. A2083c0052).

Scintillators are materials that emit visible photons when bombarded by high-energy particles (X-ray, γ-ray, electrons, neutrinos, etc.) and are crucial for applications, including X-ray imaging and high-energy particle detection. Here, we show that one-dimensional (1D) photonic crystal (PhC) cavities, added externally to scintillator materials, can be used to tailor the intrinsic emission spectrum of scintillators via the Purcell effect. The emission spectral peaks can be shifted, narrowed, or split, improving the overlap between the scintillator emission spectrum and the quantum efficiency (QE) spectrum of the photodetector. As a result, the overall photodetector signal can be enhanced by over 200%. The use of external PhC cavities especially benefits thick and large-area scintillators, which are needed to stop particles with ultrahigh energy, as in large-area neutrino detectors. Our findings should pave the way to greater versatility and efficiency in the design of scintillators for applications, including X-ray imaging and positron emission tomography. Nanyang Technological University Submitted/Accepted version L.J.W. acknowledges the Nanyang Assistant Professorship Start-up Grant.

Transition metal tellurides (TMTs) have attracted intense interest due to their intriguing physical properties arising from their diverse phase topologies. To date, a wide range of physical properties have been discovered for TMTs, including that they can act as topological insulators, semiconductors, Weyl semimetals, and superconductors. Among the TMT families, MoTe2 is a representative material because of its Janus nature and rich phases. In this Perspective, we first introduce phase structures in monolayer and bulk MoTe2 and then summarize MoTe2 synthesis strategies. We highlight recent advances of Janus MoTe2 in terms of material structures and emerging quantum states. We also provide insight into the opportunities and challenges faced by MoTe2-associated device design and applications. Ministry of Education (MOE) Nanyang Technological University National Research Foundation (NRF) Submitted/Accepted version Z.L. acknowledges support from National Research Foundation Singapore programme NRF-CRP22-2019-0007 and NRFCRP21-2018-0007.This work is also supported by the Ministry of Education, Singapore, under its AcRF Tier 3 Programme “Geometrical Quantum Materials” (MOE2018-T3-1-002). X.Z. acknowledges support from Singapore NTU Presidential Postdoctoral Fellowship (03INS000973C150). G.L. acknowledges support from National Basic Research Program of China from the MOST (2016YFA0300601, 2014CB920904, and 2015CB921402), National Natural Science Foundation of China (92065203, 11527806, and 11874406), Beijing Municipal Science & Technology Commission of China (Z191100007219008), Beijing Academy of Quantum Information Sciences (Y18G08), Strategic Priority Research Program of the Chinese Academy of Sciences (XDB33010300), and by the Synergic Extreme Condition User Facility.

Colloidal quantum wells (CQWs) provide an appealing platform to achieve emissive many-body correlations for novel optoelectronic devices, given that they act as hosts for strong carrier Coulomb interactions and present suppressed Auger recombination. However, the demonstrated high-order excitonic emission in CQWs requires ultrafast pumping with high excitation levels and can only be spectrally resolved at the single-particle level under cryogenic conditions. Here, through systematic investigation using static power-dependent emission spectroscopy and transient carrier dynamics, we show that Cu-doped CdSe CQWs exhibit continuous-wave-pumped high-order excitonic emission at room temperature with a large binding energy of ∼64 meV. We attribute this unique behavior to dopant excitons in which the ultralong lifetime and the highly localized wavefunction facilitate the formation of many-body correlations. The spectrally resolved high-order excitonic emission generated at power levels compatible with solar irradiation and electrical injection might pave the way for novel solution-processed solid-state devices. Agency for Science, Technology and Research (A*STAR) Ministry of Education (MOE) Published version C.D. is grateful for the financial support from the Ministry of Education, Singapore, under its AcRF Tier 2 grant (MOE-T2EP50121-0012). H.V.D. acknowledges the financial support in part from the Singapore Agency for Science, Technology and Research (A*STAR) MTC program under grant no. M21J9b0085, the Ministry of Education, Singapore, under its Academic Research Fund Tier 1 (MOE-RG62/20), and in part from TUBITAK 119N343, 20AG001, 121N395, and 121C266. H.V.D. also acknowledges support from TUBA and TUBITAK 2247-A National Leader Researchers Program (121C266). M.S. also acknowledges the funding through the Australian Research Council Center of Excellence in Exciton Science (grant no. CE170100026).

The emerging two-dimensional (2D) materials, particularly 2D transition metal dichalcogenides (TMDs), show great potential for catalysis due to their extraordinary large surface areas and tuneable activities. However, the as-synthesized TMDs are usually chemically inert because of their perfect atomic structure and inaccessible interlayer space for electrolytes. Herein, we activate 2D palladium diselenide (PdSe2) for catalysing the oxygen reduction reaction using a controllable electrochemical intercalation process. The electrochemically activated PdSe2 exhibits greatly enhanced electrocatalytic activities such as a doubled current density, 250 mV positive shift of potential, 5 times smaller Tafel slope, and greatly improved stability. DFT calculations were employed to study the mechanisms of electrochemical activation. Complementary experimental and theoretical studies suggest that the significantly increased activities come from (1) the activated surface with enriched Se vacancies and chemically bonded oxygen, and (2) easy access of the interlayer space for reaction intermediates. Furthermore, the robustness of the Pd-Se bonding ensures high structural stability and excellent resistance to degradation. Ministry of Education (MOE) Nanyang Technological University Accepted version This work was supported by the Nanyang Technological University under NAP award (M408050000) and Singapore Ministry of Education Tier 1 program (2018-T1-001-051). J. H. is grateful for financial support from the National Natural Science Foundation of China (No. 51771165 and 51925105), and the Natural Science Foundation of Hebei Province (No. E2020203123). B. H. acknowledges the support from the Global Frontier Program through the Global Frontier Hybrid Interface Materials (GFHIM) of the NRF funded by the Ministry of Science and ICT (Project No. 2013M3A6B1078882).

Ternary logic has been proven to carry an information ratio 1.58 times that of binary logic and is capable to reduce circuit interconnections and complexity of operations. However, the excessive transistor count of ternary logic gates has impeded their industry applications for decades. With the modulation of the ferroelectric negative capacitance (NC) properties on the channel potential, MOSFETs show many novel features including steep subthreshold swing and non-saturation output characteristics, based on which an ultra-compact ternary inverter can be achieved. Compared with traditional bulk materials, layered 2D materials and 2D ferroelectrics provide a clean interface and better electrostatic control and reliability. Even though ultra-low SS (∼10 mV/dec) has been experimentally demonstrated in ferroelectric-negative capacitance-incorporated 2D semiconductor (NC2D) FETs, the available models are still rare for large-scale circuit simulations. In this study, the superb electrical properties of pure 2D material stack-based NC2D FETs (layered CuInP2S6 adopted as the 2D ferroelectric layer) are investigated through device modeling based on the Landau–Khalatnikov (LK) equations in HSPICE. We managed to realize an ultra-compact ternary inverter with one NC2D-PMOS (WSe2) and one NC2D-NMOS (MoS2) in HSPICE simulations, whose transistor count is significantly reduced compared with other counterparts. We also proposed a novel input waveform scheme to solve the hysteresis problem caused by ferroelectric modulation to avoid logic confusion. Additionally, the power consumption and propagation delay of the NC2D-based ternary inverter are also investigated. This work may provide some insights into the design and applications of ferroelectric-incorporated 2D semiconductor devices. Ministry of Education (MOE) Published version This research work was supported by the Ministry of Education, Singapore, under its MOE Tier 2 project (MOE2019-T2-2-075), Shenzhen Science and Technology Innovation Committee JCYJ20200109115210307, and Guangdong Basic and Applied Basic Research Foundation 2019A1515111142, China.

Creating micro/nanostructures on fibers is beneficial for extending the application range of fiber-based devices. To achieve this using thermal fiber drawing is particularly important for the mass production of longitudinally uniform fibers up to tens of kilometers. However, the current thermal fiber drawing technique can only fabricate one-directional micro/nano-grooves longitudinally due to structure elongation and polymer reflow. Here, we develop a direct imprinting thermal drawing (DITD) technique to achieve arbitrarily designed surface patterns on entire fiber surfaces with high resolution in all directions. Such a thermal imprinting process is simulated and confirmed experimentally. Key process parameters are further examined, showing a process feature size as small as tens of nanometers. Furthermore, nanopatterns are fabricated on fibers as plasmonic metasurfaces, and double-sided patterned fibers are produced to construct self-powered wearable touch sensing fabric, revealing the bright future of the DITD technology in multifunctional fiber-based devices, wearable electronics, and smart textiles., Creating micro/nanostructures on fibers is beneficial to many fiber-based devices, which remains a challenge in large-scale fabrication due to elongation and reflow. Here, the authors demonstrate a method for generating high-resolution, arbitrarily designed surface patterns on fiber during the thermal drawing process.

Antimonene (Sb) is a novel kind of two-dimensional (2D) material that is predicted to be promising for various applications, such as water splitting and semiconductor devices. Several methods have been reported to prepare Sb nanoflakes/nanofilms; however, it is still relatively difficult to prepare Sb nanofilms. In this work, a method of low-power magnetron sputtering deposition was used for the preparation of Sb nanofilms with lateral dimensions on the centimeter scale and controllable film thickness. It was found that the control of the deposition temperature is important for the final crystalline structure of the nanofilms. Furthermore, the application of the nanofilms as a catalyst for water splitting (hydrogen evolution reaction (HER) and oxygen evolution reaction (OER)) was demonstrated. Ministry of Education (MOE) Published version This research was funded by the Ministry of Education, Singapore (Project ID: MOE2019- T1-001-113).

Rational design of noble metal catalysts with the potential to leverage efficiency is vital for industrial applications. Such an ultimate atom-utilization efficiency can be achieved when all noble metal atoms exclusively contribute to catalysis. Here, we demonstrate the fabrication of a wafer-size amorphous PtSe film on a SiO substate via a low-temperature amorphization strategy, which offers single-atom-layer Pt catalysts with high atom-utilization efficiency (~26 wt%). This amorphous PtSe (1.2 < x < 1.3) behaves as a fully activated surface, accessible to catalytic reactions, and features a nearly 100% current density relative to a pure Pt surface and reliable production of sustained high-flux hydrogen over a 2 inch wafer as a proof-of-concept. Furthermore, an electrolyser is demonstrated to generate a high current density of 1,000 mA cm. Such an amorphization strategy is potentially extendable to other noble metals, including the Pd, Ir, Os, Rh and Ru elements, demonstrating the universality of single-atom-layer catalysts. [Figure not available: see fulltext.], This work was supported by the Singapore National Research Foundation Singapore programme (NRF-CRP21-2018-0007, NRF-CRP22-2019-0060, NRF-CRP18-2017-02 and NRF–CRP19–2017–01) and the Singapore Ministry of Education via AcRF Tier 3 (MOE2018-T3-1-002), AcRF Tier 2 (MOE2017-T2-2-136, MOE2019-T2-2-105 and MOE2018-T2-1-176) and AcRF Tier 1 (RG7/18 and 2019-T1-002-034). It was also supported by the National Key Research and Development Program of China (2019YFA0705400, 2021YFE0194200), the National Natural Science Foundation of China (11772153, 22073048, 21763024, 22175203, 22006023), the Natural Science Foundation of Jiangsu Province (BK20190018), the National Key R&D Program of China (2021YFA1500900), the Fundamental Research Funds for Central Universities (531119200209, NE2018002, NJ2020003) and the High-Performance Computing Center of Nanjing Tech University. Catalan Institute of Nanoscience and Nanotechnology (ICN2) acknowledges funding from Generalitat de Catalunya 2017SGR327 and the project NANOGEN (PID2020-116093RB-C43), funded by MCIN/AEI/10.13039/501100011033/. ICN2 is supported by the Severo Ochoa programme from Spanish MINECO (grant no. SEV-2017-0706) and is funded by the CERCA Programme/Generalitat de Catalunya. This work has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement no. 823717-ESTEEM3.

Practical implementation of porous carbon-based composite phase-change materials (CPCMs) for heat dissipation in high-power-density electronics is usually limited by liquid leakage issues and unsatisfactory thermal conductivity resulting from their relatively low filler fraction and/or existence of interfacial thermal resistance between fillers. Therefore, development of shape-stable CPCMs with high thermal conductivity and large latent heat to avoid overheating of electronics remains challenging. Herein, graphene foams (GFs) with very high densities of up to 204 mg/cm3have been synthesized to act as interconnected porous networks of CPCMs. Notably, the obtained CPCM with a filler loading of 11.1 wt % preserves a high heat capacity (171.8 J/g) with a retention of 84.8% while showing a 22.6-fold enhancement in the thermal conductivity as compared to pure PCM (10.13 vs 0.43 W/m·K). A higher thermal conductivity of 14.29 W/m·K can be achieved by further increasing the filler loading to 17.7 wt %, which outperforms many of the previously reported CPCMs based on the interconnected porous carbon-based frameworks. Owing to the superior interconnected network structure of the dense GFs and the strong interconnection between them and PCM molecules, these CPCMs also exhibit leakage-proof shape stability and excellent thermal reliability (at least 100 cycles). Moreover, a state-of-the-art aluminum (Al) package based on the CPCM (filler loading: 11.1 wt %) possessing weight 60% less than its pure Al panel counterpart has been demonstrated to verify better heat transfer efficiency and more efficient phonon pathways of the CPCM composite than those of the pure PCM, which holds great promise for advanced thermal management of emerging applications in electronics. The authors would like to acknowledge the financial support from Thales.

International audience; It is well understood that nonlinear optical (NLO) phenomena are deeply related to the material’s symmetry. Mathematically, the material symmetry can be described in terms of the nonzero parameters in the nonlinear susceptibility tensors. Generally, more complex structures involve more nonzero parameters in the tensor. The number of parameters increases rapidly if higher NLO orders are considered, complicating the physical analysis. Conventionally, these parameters are obtained via abstract symmetry analysis, e.g., group theory (GT). This work presents a novel theoretical analysis to approach the nonlinear tensor using the simplified bond hyperpolarizability model (SBHM) and compare it with GT. Our analysis is based on a light–matter interaction classical phenomenological physical framework. Rather than just looking at the symmetry of the crystal, the model applies physical considerations requiring fewer independent parameters in the tensor than GT. Such a simplification significantly improves the determination of the surface–bulk SHG contribution factors, which cannot be extracted from the experiment alone. We also show for the case of perovskite that the SHG contribution can be addressed solely from their surface dipoles with only one independent component in the tensor. Therefore, this work may open the path for a similar analysis in other complicated semiconductor surfaces and structures in the future, with potential applications to nanoscale surface characterization and real-time surface deposition monitoring.

Two-dimensional materials that are intrinsically ferromagnetic are crucial for the development of compact spintronic devices. However, most non-layered 2D magnets with a strong ferromagnetic order are difficult to synthesize. Here we show that the flakes of trigonal and monoclinic Cr5Te8 can be grown via a chemical vapour deposition method. Using magneto-optical and magnetotransport measurements, we show that both phases exhibit robust ferromagnetism with strong perpendicular anisotropy at thicknesses of a few nanometres. A high Curie temperature of up to 200 K can be obtained by manipulating the phase structure and thickness. We also observe a colossal anomalous Hall effect in the more structurally distorted monoclinic Cr5Te8, with an anomalous Hall conductivity of 650 Ω−1 cm−1 and anomalous Hall angle of 5%. Ministry of Education (MOE) National Research Foundation (NRF) Submitted/Accepted version Z.L. acknowledges support from the National Research Foundation Singapore (NRF-CRP22-2019-0007 and NRF-CRP21-2018-0007). This research is also supported by the Ministry of Education, Singapore, under its AcRF Tier 3 Programme ‘Geometrical Quantum Materials’ (MOE2018-T3-1-002), and AcRF Tier 1 RG161/19. W.G. acknowledges support from the National Research Foundation Singapore (NRF-CRP22-2019-0004). J.L. acknowledges support from the National Natural Science Foundation of China (grant no. 11974156); Guangdong International Science Collaboration Project (grant no. 2019A050510001); Guangdong Innovative and Entrepreneurial Research Team Program (grant no. 2019ZT08C044); Shenzhen Science and Technology Program (no. KQTD20190929173815000 and 20200925161102001); the Science, Technology and Innovation Commission of Shenzhen Municipality (no. ZDSYS20190902092905285); and assistance of SUSTech Core Research Facilities, especially technical support from the Pico-Centre that receives support from the Presidential fund and Development and Reform Commission of Shenzhen Municipality. J.Z. acknowledges support from the Beijing Institute of Technology (grant no. 2021CX11013) and National Natural Science Foundation of China (grant no. 62174013).

Pentagonal 2D materials as a new member in the 2D material family have attracted increasing attention due to the exotic physical properties originating from the unique Cairo pentagonal tiling topology. Herein, the penta-PdPS atomic layers as a new air-stable 2D semiconductor with the unique puckered pentagonal low-symmetry structure are successfully exfoliated from bulk crystals grown via chemical vapor transport (CVT). Notably, 2D pentaPdPS exhibits outstanding electronic and optoelectronic performance under 650 nm laser: high electron mobility of ≈208 cm2 V−1 s−1, an ultrahigh on/off ratio of ≈108, a high photoresponsivity of 5.2 × 104 A W−1, a high photogain of 1.0 × 105, an ultrahigh detectivity of 1.0 × 1013 Jones, respectively. Significantly, the exceptional puckered pentagonal atomic structure of 2D PdPS makes it strong in-plane anisotropy in optical, electronic, and optoelectronic properties, demonstrating a sizeable anisotropic ratio of carrier mobility and photocurrent with the value of up to 3.9 and 2.3, respectively. These excellent properties make 2D Cairo Pentagonal PdPS a potential candidate in nanoelectronics, optoelectronics, polarized-nanoelectronics, which will significantly promote the development of 2D materials. Agency for Science, Technology and Research (A*STAR) National Research Foundation (NRF) Z.L. acknowledges supports from Singapore National Research Foundation – Competitive Research Program NRF-CRP22-2019-0007 and NRF-CRP21-2018-0007. This research was also supported by A*STAR under its AME IRG Grant (Project No. A2083c0052).

Plasmon antennas allow subwavelength confinement and enhancement of electromagnetic fields at the “hotspot” where the radiation efficiency of emitters can be substantially enhanced. Such enhancement, however, is often polarization dependent. Consequently, the radiation behaviors (e.g., radiation pattern and polarization states) of the emitter placed at the hotspot are also modified significantly. Enhancing the radiation efficiency without altering the original radiation pattern and polarization state of the emitter is highly desired for many sought-after applications involving chiral emitters but remains a challenging task, especially at low frequencies. To this end, spoof-plasmon antennas with fourfold and sixfold rotational symmetries are designed and realized experimentally. These plasmon antennas support polarizationindependent localized plasmon resonances, which can significantly enhance the local density of photonic states at the structural center without changing the polarization state of the emitter. As a typical example, the structure with sixfold rotational symmetry is coupled with a half-wave dipole antenna. The measurement results show that the far-field radiation pattern of the dipole antenna is maintained with the radiation efficiency enhanced by more than 2 orders of magnitude, irrespective of the dipole orientation. Agency for Science, Technology and Research (A*STAR) Ministry of Education (MOE) National Research Foundation (NRF) Submitted/Accepted version This work is supported, in part, by the National Science Foundation of China under Grants No. 61871127 and No. U21A20459, the 111 Project under Grant No. 111-2-05, and the Fund for International Cooperation and Exchange of the National Natural Science Foundation of China Grant No. 61761136007. Y.L. received funding from the Singapore Ministry of Education [Grant No. MOE2018-T2-2-189(S)], an A*Star AME IRG grant (Grant No. A20E5c0095) and Programmatic Funds (Grant No. A18A7b0058), and the National Research Foundation Singapore Competitive Research Program (Grants No. NRF220 CRP22-2019-0006 and No. NRF-CRP23-2019-0007).

Flexible electronic devices have been extensively studied for their advantages of distinguished portability, conformal contact characteristics, and human-friendly interfaces compared with conventional bulk Si technology. Flexible electronics can be attached to various surfaces like skin and internal organs for human–machine interaction, which has made significant advances in electronics, medicine, neuromorphic computing, etc. Owing to the innovation and maturation of the thin film preparation process, which have promoted the successful preparation of high-quality flexible ferroelectric films. Herein, the preparation of flexible ferroelectric devices and the progress of their applications in recent years are reviewed. Prevailing methods for preparing flexible ferroelectric films including the van der Waals heteroepitaxy on flexible substrate, delamination of the ferroelectric films on rigid substrate by chemical etching techniques, and direct use of novel 2D ferroelectric materials etc. are summarized. The research progress of flexible ferroelectric devices applied to memories, sensors, photovoltaic devices, and energy harvesters are also be discussed in detail. Moreover, the potential applications of flexible ferroelectric devices in the field of neuromorphic computing are studied, a new trend which contributes to the further development of brain-like chip systems. Finally, the challenges and prospects of flexible ferroelectric devices in the future advanced electronics are briefly proposed. Ministry of Education (MOE) This work was financially supported by the National Natural Science Foundation of China (grant nos. 62004056, 61674050, and 61874158), the Project of Distinguished Young of Hebei Province (grant no. A2018201231), the Support Program for the Top Young Talents of Hebei Province (Grant No. 70280011807), the Hundred Persons Plan of Hebei Province (grant nos. E2018050004 and E2018050003), the Supporting Plan for 100 Excellent Innovative Talents in Colleges and Universities of Hebei Province (grant no. SLRC2019018), Special project of strategic leading science and technology of Chinese Academy of Sciences (grant no. XDB44000000-7), utstanding young scientific research and innovation team of Hebei University (605020521001), Special support funds for national high level talents (041500120001), High-level Talent Research Startup Project of Hebei University (521000981426), Hebei Basic Research Special Key Project (F2021201045), Funded by Science and Technology Project of Hebei Education Department (grant no. QN2020178, QN2021026), the Singapore Ministry of Education, (grant no. AcRF TIER 2-MOE2019-T2-2-075).

This paper reports the fabrication, testing and obtained performance of a plasmonic sensor employing a gold (Au) nanohole array chip coated with tungsten disulphide (WS2), which is then functionalized for the detection of protein-protein interactions. A key novelty is that the WS2 was deposited as a monoatomic layer using a wafer-scale synthesis method that successfully provided a film of both high quality and uniform thickness. The deposited WS2 film was transferred onto a Au nanohole array chip using a novel method and was subsequently functionalized with biotin. The final sensor was tested and it demonstrated efficient real-time and label-free plasmonic detection of biotin-streptavidin coupling. Specifically, compared to a standard (i.e. uncoated) Au nanohole-based sensor, our WS2-coated Au nanohole array boosted the spectral shift of the resonance wavelength by ∼190%, resulting in a 7.64-fold improvement of the limit of detection (LOD). National Research Foundation (NRF) Submitted/Accepted version This work was supported by the Singapore National Research Foundation (NRF) and French National Research Agency (ANR), grant number (NRF2017–ANR002 2DPS).

We proposed and demonstrated mode cleaning in a high-power fiber laser by integrating an anti-resonant hollow-core fiber (AR-HCF) into a multimode laser cavity of an ytterbium (Yb)-doped fiber (YDF). An in-house mode-matched AR-HCF was fusion-spliced to a commercial multimode LMA-YDF, ensuring efficient fundamental mode coupling. The AR-HCF inflicts a high propagation loss selectively on higher-order modes, facilitating fundamental mode operation. Thus, the AR-HCF works as an efficient spatial mode filter embedded in the multimode fiber laser cavity and reinforces preferential amplification of the fundamental mode. Beam quality factor enhancement was achieved from M2 = 2.09 to 1.39 at an output power of 57.7 W (pump-power limited). The beam quality can be further improved by refining the AR-HCF fabrication. The proposed technique has a great potential to be exploited in other multimode fiber laser cavities involving erbium- or thulium-doped fibers and obviates the need for complicated specialty active fiber designs. Compared with the commonly used fiber bending technique, our method can achieve an efficient higher-order mode suppression without inducing mode-field deterioration. National Research Foundation (NRF) Published version National Research Foundation Singapore (QEP-P4).

High Q-factor resonance holds great promise for bio-chemical sensing and enhanced light-matter interaction. However, terahertz (THz) magnetic resonances usually demonstrate low Q-factors, resulting in huge energy radiation loss particularly in high frequency bands. Here, we show that high Q-factor magnetic dipole resonance at THz frequencies can be achieved by exploiting the coherent Fano interactions with strong field enhancements in an array composed of single metallic split-ring resonators, working at Wood-Rayleigh anomalies. It can give rise to ultrahigh Q-factor beyond 104 in the THz regime. Experimentally, the measured Q-factor of dominant magnetic dipole resonance can achieve no less than a level of ∼261 by Lorentzian fitting to the experimental data. In addition, a high Q-factor of the fundamental-order magnetic dipole resonance is demonstrated beyond 30. High-Q magnetic dipole resonance is closely associated with ultralow-damping and negative permeability in the THz band. The measurements of magnetic dipole resonances are in good agreement with the theoretical analyses. Our scheme suggests a feasible route to suppress radiative loss for enhanced THz field-matter interaction. Agency for Science, Technology and Research (A*STAR) Ministry of Education (MOE) National Research Foundation (NRF) Submitted/Accepted version The authors acknowledge the funding supported by the Fundamental Research Funds for the Central Universities (Talent startup fund No. AUGA5710012622), the National Natural Science Foundation of China (No. 61377110), the Natural Science Foundation of Heilongjiang Province (No. LH2019F012), and the China Scholarship Council (No. 202006120141). Y.L. and Q.J.W. acknowledge funding support from the Singapore Ministry of Education [No. MOE2018-T2-2-189(S)], the A Star AME IRG Grant (No. A20E5c0095), Programmatic Funds (No. A18A7b0058), and the National Research Foundation Singapore Competitive Research Program (Nos. NRF-CRP22-2019-0006 and NRF-CRP23-2019-0007).

Integrating two-dimensional (2D) transition-metal dichalcogenides (TMDCs) into dielectric plasmonic nanostructures enables the miniaturization of on-chip nanophotonic devices. Here we report on a high-quality light emitter based on the newly designed 2D h-BN/WS2 heterostructure integrated with an array of TiO2 nanostripes. Different from a traditional strongly coupled system such as the TMDCs/metallic plasmonic nanostructure, we first employ dielectric nanocavities and achieve a Purcell enhancement on the nanoscale at room temperature. Furthermore, we demonstrate that the light emission strength can be effectively controlled by tuning the polarization configuration. Such a polarization dependence meanwhile could be proof of the resonant energy transfer theory of dipole-dipole coupling between TMDCs and a dielectric nanostructure. This work gains experimental and simulated insights into modified spontaneous emission with dielectric nanoplasmonic platforms, presenting a promising route toward practical applications of 2D semiconducting photonic emitters on a silica-based chip. National Research Foundation (NRF) Submitted/Accepted version This work was supported by Start-up funds of Wuhan University and Singapore National Research Foundation (NRF) under the Competitive Research Programs (NRFCRP-21-2018-0007).

Two-dimensional (2D) ferromagnets with out-of-plane (OOP) magnetic anisotropy are potential candidates for realizing the next-generation memory devices with ultra-low power consumption and high storage density. However, a scalable approach to synthesize 2D magnets with OOP anisotropy directly on the complimentary metal-oxide semiconductor (CMOS) compatible substrates has not yet been mainly explored, which hinders the practical application of 2D magnets. This work demonstrates a cascaded space confined chemical vapor deposition (CS-CVD) technique to synthesize 2D FexGeTe2 ferromagnets. The weight fraction of iron (Fe) in the precursor controls the phase purity of the as-grown FexGeTe2. As a result, high-quality Fe3GeTe2 and Fe5GeTe2 flakes have been grown selectively using the CS-CVD technique. Curie temperature (TC) of the as-grown FexGeTe2 can be up to ∼ 280 K, nearly room temperature. The thickness and temperature-dependent magnetic studies on the Fe5GeTe2 reveal a 2D Ising to 3D XY behavior. Also, Terahertz spectroscopy experiments on Fe5GeTe2 display the highest conductivity among other FexGeTe2 2D magnets. The results of this work indicate a scalable pathway for the direct growth and integration of 2D ternary magnets on CMOS-based substrates to develop spintronic memory devices. [Figure not available: see fulltext.]. Ministry of Education (MOE) National Research Foundation (NRF) Submitted/Accepted version This work was supported from National Research Foundation Singapore programme NRF-CRP22-2019-0007, NRF-CRP22- 2019-0004 and NRF-CRP21-2018-0007. This work was also supported by the Ministry of Education, Singapore, under its AcRF Tier 3 Programme ‘Geometrical Quantum Materials’ (MOE2018-T3-1-002), AcRF Tier 2 (MOE2019-T2-2-105) and AcRF Tier 1 RG4/17 and RG7/18. We also thank the funding support from National Research foundation (NRF-CRP22- 2019-0004).

Summary Chemical vapor deposition (CVD) is a promising approach for the controllable synthesis of two-dimensional (2D) materials. Many studies have demonstrated that the morphology and structure of 2D materials are highly dependent on growth substrates. Hence, the choice of growth substrates is essential to achieve the precise control of CVD growth. Noble metal substrates have attracted enormous interest owing to the high catalytic activity and rich surface morphology for 2D material growth. In this review, we introduce recent progress in noble metals as substrates for the controllable growth of 2D materials. The underlying growth mechanism and substrate designs of noble metals based on their unique features are thoroughly discussed. In the end, we outline the advantages and challenges of using noble metal substrates and prospect the possible approaches to extend the uses of noble metal substrates for 2D material growth and enhance the structural controllability of the grown materials., Graphical abstract, Materials science; Materials synthesis; Nanomaterials

We show the increase of the photoluminescence intensity ratio (PLR) and the emission rate enhancement of perovskite cesium lead bromide (CsPbBr3 ) and formamidinium lead bromide (FAPbBr3 ) nanocrystals (NCs) in the presence of single and double gold layer cavities, which we refer to as Metal-Emitter (ME) and Metal-Emitter-Metal (MEM) nanostructures. Up to 1.9-fold PLRs and up to 5.4-fold emission rate enhancements were obtained for FAPbBr3 NCs confined by double gold layers, which are attributed to plasmonic confinement from the gold layers. The experimentally obtained values are validated by analytical calculations and electromagnetic simulations. Such an effective method of manipulation of the spontaneous emission by simple plasmonic nanostructures can be utilized in sensing and detection applications. Ministry of Education (MOE) Published version This research was funded by Ministry of Education, Singapore, grant nos. MOE2016-T2-1-052 and MOE2019-T1-002-063.

The solid electrolyte interface (SEI) significantly affects alkaline metal ion battery performance in terms of reversible capacity, Coulombic efficiency, and cycling stability. However, intrinsic properties of SEI layer in potassium ion batteries (KIBs), including structures, components, formation mechanism, and corresponding K+ storage behavior, are poorly understood. Here, we focus on the effect of electrolyte on SEI formation and K+ storage behavior in self-supported nitrogen-doped graphite foams (NGFs). Two types of organic electrolytes, KPF6 and KN(SO2F)2 (KFSI) salt in EC/DEC solution, were carefully selected and compared in detail to reveal the effect of SEI on the K+ ion storage mechanism. The experimental results, including in situ electrochemical evaluations and depth-profiling XPS analysis, demonstrate that the salts of KFSI result in a more uniform, stable, and thinner SEI layer compared with the SEI induced by KPF6. Particularly, the KFSI-induced SEI is rich in stable and uniformly distributed inorganic species and polycarbonates, whereas the KPF6-induced SEI is mainly composed of instable alkyl carbonates. This could be attributed to the larger FSI– size over PF6– and lower LUMO levels than solvents according to theoretical calculations, which effectively prevent SEI from co-intercalation damage, thus leading to high stability of the as-obtained SEI layer. In general, the above-mentioned features could ensure high reversibility and good cycling stability of the self-supported NGFs electrode in KFSI-based electrolyte. Ministry of Education (MOE) Accepted version The authors acknowledge the financial support from the Ministry of Education (MOE) AcRF Tier 3 [MOE2011-T3-1- 005], the Young Scientists Fund of the National Natural Science Foundation of China [Grants 51802091, 11504123, and 51627805], and the National Youth Thousand Talents Program [Grant 531109200024]. We also acknowledge the Facility for Analysis, Characterization, Testing and Simulation, Nanyang Technological University, Singapore, for use of their field emission Auger microprobe (JEOL JAMP-7830F).

Two-dimensional (2D) hybrid lead bromide perovskites are candidates for high light yield, fast scintillators. In this paper, we discuss the effect of commensurate Lithium (Li)-doping (1 : 1 Li : Pb precursor ratio) on the scintillation properties of two previously reported high light yield 2D-perovskite crystals, PEA2PbBr4 and BA2PbBr4. The effect of Li, e.g. light yield enhancement, is more prominent in PEA2PbBr4 compared to BA2PbBr4. Both perovskite crystals show a broadening of the radioluminescence spectrum and a slightly longer afterglow, with residual scintillation below 2% after 5 s for both materials. The effects of Li on the negative thermal quenching exhibited by the perovskites are also discussed. Li doping increases the light yield of PEA2PbBr4 by 78% and both perovskite materials show an improvement in their energy resolutions, with a record of 7.7% at 662 keV for the Li-doped PEA2PbBr4. Both perovskite crystals also show very fast gamma-ray excited scintillation decays, with average times of 12.9 ns and 8.0 ns for PEA2PbBr4 and BA2PbBr4, respectively. This work shows that Li doping brings a significant improvement of the perovskite performance, making the perovskites more competitive for fast, high light yield applications in the medical, security or industrial sectors. Ministry of Education (MOE) The authors acknowledge financial supports from the Singapore Ministry of Education (MOE2019-T1-002-087) and Thales-CINTRA Funding.

CsPbBr3 quantum dots (QDs) have recently gained much interest due to their excellent optical and scintillation properties and their potential for X-ray imaging applications. In this study, we blended CsPbBr3 QDs with resin at different QD concentrations to achieve thick films and to protect the CsPbBr3 QDs from environmental moisture. Then, their scintillation properties are investigated and compared to the traditional commercial scintillators, CsI:Tl microcolumns, and Gadox layers. The CsPbBr3 QD-resin sheets show a high light yield of up to 21 500 photons/MeV at room temperature and a relatively small variation in light yield across a wide temperature range. In addition, the CsPbBr3 QD-resin sheets feature a small scintillation afterglow. The CsPbBr3 QD-resin sheets show a negligible trap density for the concentration below 50% weight, indicating that traps might arise from the aggregation of the QDs. The CsPbBr3 QD-resin sheets are also very stable at low irradiation intensities and relatively stable at higher intensities, with higher CsPbBr3 QD concentrations being more stable. Gamma-ray-excited-time-resolved emission measurements at 662 keV showed that the CsPbBr3 QD-resin sheets have an average scintillation decay time between 108 and 176 ns, which are still 10 000 and 6000 times faster than CsI:Tl and Gadox, respectively. Imaging tests show that the CsPbBr3 QD-resin sheets have a mean transfer function of 50% at 2 lp/mm and 20% at 4 lp/mm, comparable to that of commercial Gadox layers. This feature makes CsPbBr3 QD-resin sheets a good candidate for the low-cost, flexible X-ray imaging screens and γ-ray applications. Ministry of Education (MOE) The authors acknowledge financial supports from the Singapore Ministry of Education (MOE2019-T1-002-087) and Thales-CINTRA Funding.

The prosperity in portable and wearable electronics has stimulated researchers to develop safe, environmentally friendly, and efficient energy-storage technologies. Increased efforts have recently been made to fabricate high-performance rechargeable aqueous alkaline batteries (RAABs) as the frontrunner to complement and even replace the dominant lithium-ion batteries for large-scale energy storage due to the limited lithium resources and the use of flammable and toxic organic electrolyte. Compared with the conventional planar RAABs, fiber-shaped RAABs (FRAABs) manifest several intriguing features, such as miniaturization, adaptability, and weavability, making them an attractive candidate to power wearable and portable electronics. Herein, an overview of the recent progress in FRAABs by categories of fiber-shaped aqueous rechargeable Zn-based batteries, Fe−Ni batteries, and Bi−Ni batteries, with respect to the active electrode materials, device configurations, and battery properties, is comprehensively presented. Finally, the remaining challenges and possible solutions are emphasized as a useful guide for the further development of FRAABs. Agency for Science, Technology and Research (A*STAR) Ministry of Education (MOE) Nanyang Technological University National Research Foundation (NRF) Published version This work was sup-ported by the Singapore Ministry of Education Academic ResearchFund Tier 2 (MOE2019-T2-2-127 and MOE-T2EP50120-0002), A*STARunder AME IRG (A2083c0062), A*STAR under IAF-ICP (I2001E0067(IAF-ICP)-P2.1) and I2001E0067 (Schaeffler) P2.1, the SingaporeMinistry of Education Academic Research Fund Tier 1 (RG90/19 andRG73/19), and the Singapore National Research FoundationCompetitive Research Program (NRF-CRP18-2017-02). This work was alsosupported by Nanyang Technological University.

The well-developed preform-to-fiber thermal drawing technique owns the benefit to maintain the cross-section architecture and obtain an individual micro-scale strand of fiber with the extended length up to thousand meters. In this work, we propose and demonstrate a two-step soluble-core fabrication method by combining such an inherently scalable manufacturing method with simple post-draw processing to explore the low viscosity polymer fibers and the potential of soft fiber electronics. As a result, an ultra-stretchable conductive fiber is achieved, which maintains excellent conductivity even under 1900% strain or 1.5 kg load/impact freefalling from 0.8-m height. Moreover, by combining with triboelectric nanogenerator technique, this fiber acts as a self-powered self-adapting multi-dimensional sensor attached on sports gears to monitor sports performance while bearing sudden impacts. Next, owing to its remarkable waterproof and easy packaging properties, this fiber detector can sense different ion movements in various solutions, revealing the promising applications for large-area undersea detection., Though thermal drawing methods are attractive for fabricating fiber-based sensor devices, existing methods allow limited access to low viscosity and low modulus materials. Here, the authors demonstrate a two-step soluble-core fiber fabrication method with wide applicability to soft polymer materials.

Despite its advantages of scalable process and cost-effectiveness, nanoimprinting faces challenges with imprinting hard materials (e.g., crystalline metals) at low/room temperatures, and with fabricating complex nanostructures rapidly (e.g., heterojunctions of metal and oxide). Herein, we report a room temperature ultrasonic nanoimprinting technique (named nanojackhammer) to address these challenges. Nanojackhammer capitalizes on the concentration of ultrasonic energy flow at nanoscale to shape bulk materials into nanostructures. Working at room temperature, nanojackhammer allows rapid fabrication of complex multi-compositional nanostructures made of virtually all solid materials regardless of their ductility, hardness, reactivity and melting points. Atomistic simulations reveal a unique alternating dislocation generation and recovery mechanism that significantly reduces the imprinting force under ultrasonic cyclic loading. As a proof-of-concept, a metal-oxide-metal plasmonic nanostructure with built-in nanogap is rapidly fabricated and employed for biosensing. As a fast, scalable, and cost-effective nanotechnology, nanojackhammer will enable various unique applications of complex nanostructures in optoelectronics, biosensing, catalysis and beyond., Nanoimprinting faces challenges with imprinting hard materials at low or room temperature, and with fabricating complex nanostructures rapidly. Here, the authors overcome these challenges by a room-temperature ultrasonic nanoimprinting technique that capitalizes on the concentration of ultrasonic energy flow at nanoscale.

We present the synthesis and characterization of gallium nitride (GaN) pine tree-like nanostructures (PTLNs) grown by low-pressure chemical vapor deposition. A high yield of PTLNs is densely arranged with each PTLN having a typical length of 15.46 ± 3.38 μm. From Raman spectroscopy, we observe anE2Hpeak at 570 ± 6 cm-1which is the primary characteristic of wurtzite. X-ray and ultraviolet photoemission spectroscopy reveal that the electronic structures of GaN PTLNs indicate an n-type character, while the work function and valence band maximum are determined to be 3.30 ± 0.05 and 3.85 ± 0.08 eV, respectively. We confirm the electronic nature of our structure from the current-voltage characteristics exhibiting rectifying behavior. Density functional theory calculations of GaN PTLNs modeled by germanium-doped GaN nanowires are consistent with our experimental findings. To summarize, the energy-band diagram is presented for the future of GaN PTLNs in the optoelectronic and sensing applications. Ministry of Education (MOE) This research is supported by the Ministry of Education, Singapore, under its Academic Research Fund Tier 2, grant no. MOE2016-T2-1-052 and Tier 1, grant no. MOE2019-T1-002063. F.A. and H.H. would like to acknowledge Toray Science and Technology Research Grant 2021.

By applying a sudden perturbation to one of the components of a mixture of two quantum fluids, we explore the effect on the motion of the second component on a short time scale. By implementing perturbation theory, we prove that for short times the response of the second component is fixed by the energy weighted moment of the crossed dynamic structure factor (crossed f-sum rule). We also show that by properly monitoring the time duration of the perturbation it is possible to identify peculiar fast spin drag regimes, which are sensitive to the interaction effects in the Hamiltonian. Special focus is given to the case of coherently coupled Bose-Einstein condensates, interacting Bose mixtures exhibiting the Andreev-Bashkin effect, normal Fermi liquids and the polaron problem. The relevant excitations of the system contributing to the spin drag effect are identified and the contribution of the low frequency gapless excitations to the f-sum rule in the density and spin channels is explicitly calculated employing the proper macroscopic dynamic theories. Both spatially periodic and Galilean boost perturbations are considered., Comment: 11 pages, 2 figure

We report the optical and scintillation properties of (C6H5CH2NH3)2SnBr4 with excellent absorption length at 20 keV of 0.016 cm, measured bandgap of 2.51 eV, and photoluminescence lifetime of 1.05 μs. The light yield obtained with the 241Am source is 3600 ± 600 photons per MeV, which is much smaller than the maximum attainable light yield obtained from the bandgap. Temperature dependent radioluminescence measurements confirm the presence of thermal quenching at room temperature with the activation energy and the ratio between the attempt and the radiative transition rates of 61 meV and 129, respectively. Although thermal quenching affects light yield at room temperature, this green light-emitting perovskite opens an avenue for new lead-free scintillating materials. Ministry of Education (MOE) Published version This work is part of the project that has received funding from Universitas Prasetiya Mulya, Indonesia Toray Science Foundation, "Penelitian, Pengabdian Masyarakat, dan Inovasi (PPMI) Institut Teknologi Bandung (ITB) 2021, and Ministry of Education, Singapore (award no. MOE2018-T2-1-088). RL and TL measurements were performed at the National Laboratory for Quantum Technologies (NLTK), Nicolaus Copernicus University and supported by the European Regional Development Fund.

Reducing the lateral scale of two-dimensional (2D) materials to one-dimensional (1D) has attracted substantial research interest not only to achieve competitive electronic applications but also for the exploration of fundamental physical properties. Controllable synthesis of high-quality 1D nanoribbons (NRs) is thus highly desirable and essential for further study. Here, we report the implementation of supervised machine learning (ML) for the chemical vapor deposition (CVD) synthesis of high-quality quasi-1D few-layered WTe2 NRs. Feature importance analysis indicates that H2 gas flow rate has a profound influence on the formation of WTe2, and the source ratio governs the sample morphology. Notably, the growth mechanism of 1T' few-layered WTe2 NRs is further proposed, which provides new insights for the growth of intriguing 2D and 1D tellurides and may inspire the growth strategies for other 1D nanostructures. Our findings suggest the effectiveness and capability of ML in guiding the synthesis of 1D nanostructures, opening up new opportunities for intelligent materials development. Ministry of Education (MOE) The authors gratefully acknowledge financial support by National Key Research and Development Program of China (2020YFB2008501 and 2019YFC1520900), the National Natural Science Foundation of China (61974120, 11904289, 61701402, and 61804125), Key Research and Development Program of Shaanxi Province (2020ZDLGY04-08, 2020GXLH-Z-027, 2021JZ-43), the Key Program for International Science and Technology Cooperation Projects of Shaanxi Province (2018KWZ-08), the Natural Science Foundation of Shaanxi Province (2019JQ-613), the Natural Science Foundation of Ningbo (202003N4003), the Fundamental Research Funds for the Central Universities (3102019PY004, 31020190QD010, and 3102019JC004), and the start-up funds from Northwestern Polytechnical University. The authors also acknowledge the support from Ministry of Education, Singapore, under its AcRF Tier 3 Programme "Geometrical Quantum Materials" (MOE2018-T3-1-002) and AcRF Tier 1 RG161/19.

The development of earth-abundant oxygen reduction reaction (ORR) catalysts with high catalytic activity and good stability for practical metal-air batteries remains an enormous challenge. Herein, a highly efficient and durable ORR catalyst is reported, which consists of atomically dispersed Co single atoms (Co-SAs) in the form of Co-N4 moieties and small Co nanoparticles (Co-SNPs) co-anchored on nitrogen-doped porous carbon nanocage (Co-SAs/SNPs@NC). Benefiting from the synergistic effect of Co-SAs and Co-SNPs as well as the enhanced anticorrosion capability of the carbon matrix brought by its improved graphitization degree, the resultant Co-SAs/SNPs@NC catalyst exhibits outstanding ORR activity and remarkable stability in alkaline media, outperforming Co-SAs-based catalyst (Co-SAs@NC), and benchmark Pt/C catalyst. Density functional theory calculations reveal that the strong interaction between Co-SNPs and Co-N4 sites can increase the valence state of the active Co atoms in Co-SAs/SNPs@NC and moderate the adsorption free energy of ORR intermediates, thus facilitating the reduction of O2. Moreover, the practical zinc-air battery assembled with Co-SAs/SNPs@NC catalyst demonstrates a maximum power density of 223.5 mW cm–2, a high specific capacity of 742 W h kg–1 at 50 mA cm–2 and a superior cycling stability. Ministry of Education (MOE) Nanyang Technological University National Research Foundation (NRF) The authors thank Nanyang Technological University, Singapore, for providing financial support. This work was also supported by National Research Foundation–Competitive Research Programs (NRF-CRP22-2019-0007, and NRF-CRP21-2018-0007), and the Singapore Ministry of Education AcRF Tier 2 (MOE2019-T2-2-105) and AcRF Tier 1 (RG7/18 and RG161/19). X.Z. acknowledges the financial supports from the National Natural Science Foundation of China (NSFC): Grant No. 21922507 and 21771079, the Jilin Province Science and Technology Development Plan (No. YDZJ202101ZYTS126), and the Fundamental Research Funds for the Central Universities. Y.L. acknowledges the financial supports from the NSFC (Grant No. 22005116), the International Postdoctoral Exchange Fellowship Program (20190054).

NASICON-structured NaTi2(PO4)3 (NTP) is an attractive anode material for aqueous rechargeable sodium-ion batteries (ARSIBs) thanks to its three-dimensional open framework and appropriate negative voltage window. Nevertheless, the lack of flexible and high-performance binder-free NTP-based anodes remains stumbling blocks to the development of wearable ARSIBs. Herein, hollow-structure NTP evenly encapsulated in cross-linked porous N-doped carbon nanofiber (HNTP@PNC) is prepared through electrospinning technology and subsequent carbonization treatment, directly acting as binder-free anode for flexible ARSIBs. Benefiting from its unique hollow structure, continuous conductive network and favorable synergistic effect, the HNTP@PNC electrode displays as high as of 108.3 mAh g−1 rate capacity at 5.50 A g−1 and an impressive cycling stability of 97.2% capacity retention after 3000 cycles. Further, theoretical calculations reveal that NTP with NC coating significantly enhances electronic conductivity and accelerates Na+ diffusion kinetics. Pairing with potassium zinc hexacyanoferrate free-standing cathode, a prototype quasi-solid-state ARSIB with a high-voltage discharge plateau of 1.6 V is successfully constructed, achieving a high volumetric capacity of 24.5 mAh cm−3 and an admirable energy density of 39.2 mWh cm−3, outperforming most reported flexible aqueous rechargeable energy-storage devices. These exciting results provide valuable intuition into the design of novel binder-free NTP-based anodes for next-generation wearable ARSIBs. Agri-Food and Veterinary Authority of Singapore (AVA) Submitted/Accepted version

Thermally drawn multimaterial fibers have experienced rapid development in the past two decades owing to the high scalability, uniformity, and material and structure compatibility of the thermal drawing technique. This article reviews various multimaterial fibers based on different functional structures and their applications in disparate fields. We start from the functional structures achieved in optical fibers developed in the early stage of thermally drawn fibers. Subsequently, we introduce both typical functional structures and unique structures created in multimaterial fibers for varying applications. Next, we present the early attempts in breaking the axial symmetric structures of thermally drawn fibers for extended functionalities. Additionally, we summarize the current progress on creating surface structures on thermally drawn fibers. Finally, we provide an outlook for this trending topic towards wearable devices and smart textiles. Agency for Science, Technology and Research (A*STAR) Ministry of Education (MOE) Nanyang Technological University National Research Foundation (NRF) Published version This work was supported by the Singapore Ministry of Education Academic Research Fund Tier 2 (MOE2019-T2-2-127 and T2EP50120-0005), A∗STAR under AME IRG (A2083c0062), the Singapore Ministry of Education Academic Research Fund Tier 1 (RG90/19 and RG73/19), and the Singapore’s National Research Foundation Competitive Research Program (NRF-CRP18-2017-02). This work was also supported by Nanyang Technological University.

The last decade has witnessed the significant progress of physical fundamental research and great success of practical application in two-dimensional (2D) van der Waals (vdW) materials since the discovery of graphene in 2004. To date, vdW materials is still a vibrant and fast-expanding field, where tremendous reports have been published covering topics from cutting-edge quantum technology to urgent green energy, and so on. Here, we briefly review the emerging hot physical topics and intriguing materials, such as 2D topological materials, piezoelectric materials, ferroelectric materials, magnetic materials and twistronic heterostructures. Then, various vdW material synthetic strategies are discussed in detail, concerning the growth mechanisms, preparation conditions and typical examples. Finally, prospects and further opportunities in the booming field of 2D materials are addressed. Ministry of Education (MOE) National Research Foundation (NRF) Published version This work was supported by the National Research Foundation– Competitive Research Program (NRF-CRP21-2019-0007 and NRF-CRP21-2018-0007); the Singapore Ministry of Education Tier 3 Programme ‘Geometrical Quantum Materials’ (MOE2018-T3-1-002), AcRF Tier 2 (2016-T2-2-153) and AcRF Tier 1 (RG7/18 and RG161/19); the National Key R&D Program of China (2020YFA0309200), the National Natural Science Foundation of China (62074025); the Applied Basic Research Program of Sichuan Province (2020ZYD014 and 2021JDGD0026); the Sichuan Province Key Laboratory of Display Science and Technology and the Postdoctoral Innovative Talent Supporting Program (BX20190060).

Molybdenum disulfide (MoS₂) is one of the compounds discussed nowadays due to its outstanding properties that allowed its usage in different applications. Its band gap and its distinctive structure make it a promising material to substitute graphene and other semiconductor devices. It has different applications in electronics especially sensors like optical sensors, biosensors, electrochemical biosensors that play an important role in the detection of various diseases’ like cancer and Alzheimer. It has a wide range of energy applications in batteries, solar cells, microwave, and Terahertz applications. It is a promising material on a nanoscale level, with favorable characteristics in spintronics and magnetoresistance. In this review, we will discuss MoS₂ properties, structure and synthesis techniques with a focus on its applications and future challenges. Published version This research was funded by United Arab Emirates University UPAR project, grant number 31N393.

The change of the phase of light under the evolution of a nanomaterial with time is a promising new research direction. A phenomenon directly related to the sudden phase change of light is the Goos-Hänchen (G-H) shift, which describes the lateral beam displacement of the reflected light from the interface of two media when the angles of incidence are close to the total internal reflection angle or Brewster angle. Here, an innovative design of lithography-free nanophotonic cavities to realize electrically tunable G-H shifts at the singular phase of light in the visible wavelengths is reported. Reversible electrical tuning of phase and G-H shifts is experimentally demonstrated using a microheater integrated optical cavity consisting of a dielectric film on an absorbing substrate through a Joule heating mechanism. In particular, an enhanced G-H shift of 110 times of the operating wavelength at the Brewster angle of the thin-film cavity is reported. More importantly, electrically tunable G-H shifts are demonstrated by exploiting the significant tunable phase change that occurs at the Brewster angles, due to the small temperature-induced refractive index changes of the dielectric film. Realizing efficient electrically tunable G-H shifts with miniaturized heaters will extend the research scope of the G-H shift phenomenon and its applications. Agency for Science, Technology and Research (A*STAR) Ministry of Education (MOE) National Research Foundation (NRF) Accepted version K.V.S. and R.S. acknowledge the funding support from Singapore Ministry of Education (MOE) grant numbers AcRF MOE2016-T3-1-006 and MOE AcRF Tier 1 RG96/19 and Advanced Manufacturing and Engineering (AME) Programmatic grant (A18A5b0056) by Agency for Science, Technology and Research (A*STAR). R.M. and R.S.R. would like to acknowledge the Ministry of Education (MOE) through Tier 2 grants (2019-T2-1-058). In addition, C.M.D. and K.T.Y. acknowledge the funding support from Singapore National Research Foundation (NRF) and French National Research Agency (ANR), grant number (NRF2017-ANR002 2DPS).

Combination of anti-resonant hollow-core fiber (HCF) and semiconductor nanomaterial is an effective strategy to obtain high-performance gas sensors with exceptional sensitivity and low power consumption. However, controlling the semiconductor morphology onto HCF is a major challenge to achieve the desired gas sensor with the enhanced sensitivity. Here, a ZnO-Bi2O3 nanosheets (NSs) heterostructure is grown in situ on the surface of HCF by sol–gel and hydrothermal methods. ZnO-Bi2O3 NSs serving as electron acceptors trap electrons after acetone adsorption and then change the refractive index of the surface of HCF. Benefiting from the unique sheet structure and the synergetic effects for multi-component, the resulting ZnO-Bi2O3 NSs enabled HCF gas sensor exhibits high sensitivity, selectivity, and repeatability for detecting acetone at room temperature, particularly in the low concentration range, with the theoretical limit of detection down to 140 parts-per-billion. Meanwhile, the successful application of the ZnO-Bi2O3 NSs enabled HCF gas sensor to distinguish the exhaled breath from the healthy individuals and simulated diabetic cases is demonstrated, which paves the way to achieve non-invasive, ultra-sensitivity gas sensing at room temperature for the early diagnosis of diabetes. Agency for Science, Technology and Research (A*STAR) Ministry of Education (MOE) National Research Foundation (NRF) Submitted/Accepted version This work was supported by the Singapore Ministry of Education Academic Research Fund Tier 2 (MOE2019-T2-2-127 and T2EP50120-0005), A*STAR under AME IRG (A2083c0062), the Singapore Ministry of Education Academic Research Fund Tier 1 (RG90/19 and RG73/19) and the Singapore National Research Foundation Competitive Research Program (NRF-CRP18-2017-02), Guangdong Basic and Applied Basic Research Foundation (2019A1515011762), Shenzhen Science and Technology Innovation Foundation (JCYJ20180305125302333, JCYJ20170818093035338, JCYJ20180305125430954), Shenzhen University Fund (860-000002110229) and Foshan City Education Department Foundation.