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It has recently been shown that interference effects in disordered systems give rise to two non-trivial structures: the coherent backscattering (CBS) peak, a well-known signature of interference effects in the presence of disorder, and the coherent forward scattering (CFS) peak, which emerges when Anderson localization sets in. We study here the CFS effect in the presence of quantum multifractality, a fundamental property of several systems, such as the Anderson model at the metal-insulator transition. We focus on Floquet systems, and find that the CFS peak shape and its peak height dynamics are generically controlled by the multifractal dimensions $D_1$ and $D_2$, and by the spectral form factor. We check our results using a 1D Floquet system whose states have multifractal properties controlled by a single parameter. Our predictions are fully confirmed by numerical simulations and analytic perturbation expansions on this model. Our results, which we believe to be generic, provide an original and direct way to detect and characterize multifractality in experimental systems., 7 pages, 3 figures

Acoustic vibrations of Au and Ag elongated nano-objects with original morphologies, from Ag–Ag homodimers to Au@Ag–Ag heterodimers and Au@Ag eccentric core–shell spheroids, have been experimentally investigated by ultrafast time-resolved optical spectroscopy. Their frequencies, obtained by the analysis of time-dependent transient absorption changes, are compared with results from Finite Element Modeling (FEM) numerical computations, which allow assignment of the detected oscillating signals to fundamental radial and extensional modes. FEM was further used to analyze the effects of morphology and composition on the vibrational dynamics. FEM computations indicate that (1) the central distance between particles forming the nanodimers have profound effects on the extensional mode frequencies and a negligible influence on the radial mode ones, in analogy with the case of monometallic nanorods, (2) coating Au with Ag also has a strong mass-loading-like effect on the dimer and core-shell stretching mode frequency, while (3) its influence on the radial breathing mode is smaller and analogous to the non-monotonical frequency dependence on Au fraction previously observed in isotropic bimetallic spheres. These findings are significant for developing a predictive understanding of nanostructure mechanical properties and for designing new mechanical nanoresonators. Agency for Science, Technology and Research (A*STAR) Ministry of Education (MOE) Nanyang Technological University Accepted version This work is financially supported by the National Natural Science Foundation of China (grant no. 11774071, 11874125, and 11704079), the Science and Technology Program of Guangzhou (grant no. 201804010451 and 201904010104), the State Key Laboratory of Luminescence and Applications (grant no. SKLA-2019-08), the Pearl River Talent Programme in Guangdong Province (2017GC010251) and by a NTU start-up grant, the A*STAR Advanced Optics in Engineering Program (122 360 0008), and the Ministry of Education Singapore (MOE2018-T2-1-081).

An anisotropic quantum vacuum (AQV) has been predicted to induce quantum interferences during the spontaneous emission process in an atomic $V$-transition [G. S. Agarwal, Phys. Rev. Lett. 84, 5500 (2000)]. Nevertheless, the finite lifetime of the excited states is expected to strongly limit the observability of this phenomenon. In this paper, we predict that an AQV can induce a long-lifetime coherence in an atomic $\Lambda$-transition from the process of spontaneous emission, which has an additional advantage of removing the need for coherent laser excitation. We also carry out two metasurface designs and compare their respective efficiencies for creating an AQV over remote distances. The detection of this coherence induced by a metasurface, in addition to being yet another vindication of quantum electrodynamics, could pave the way towards the remote distance control of coherent coupling between quantum emitters, which is a key requirement to produce entanglement in quantum technology applications., Comment: 15 pages, 9 figures

Analogous to the B- and Z-DNA structures in double-helix DNA, there exist both right- and left-handed quadruple-helix (G-quadruplex) DNA. Numerous conformations of right-handed and a few left-handed G-quadruplexes were previously observed, yet they were always identified separately. Here, we present the NMR solution and X-ray crystal structures of a right- and left-handed hybrid G-quadruplex. The structure reveals a stacking interaction between two G-quadruplex blocks with different helical orientations and displays features of both right- and left-handed G-quadruplexes. An analysis of loop mutations suggests that single-nucleotide loops are preferred or even required for the left-handed G-quadruplex formation. The discovery of a right- and left-handed hybrid G-quadruplex further expands the polymorphism of G-quadruplexes and is potentially useful in designing a left-to-right junction in G-quadruplex engineering. NRF (Natl Research Foundation, S’pore) MOE (Min. of Education, S’pore) Published version

DNA sequence composition determines the topology and stability of G-quadruplexes (G4s). Bulged G-quadruplex structures (G4-Bs) are a subset of G4s characterized by 3D conformations with bulges. Current search algorithms fail to capture stable G4-B, making their genome-wide study infeasible. Here, we introduced a large family of computationally defined and experimentally verified potential G4-B forming sequences (pG4-BS). We found 478 263 pG4-BS regions that do not overlap 'canonical' G4-forming sequences in the human genome and are preferentially localized in transcription regulatory regions including R-loops and open chromatin. Over 90% of protein-coding genes contain pG4-BS in their promoter or gene body. We observed generally higher pG4-BS content in R-loops and their flanks, longer genes that are associated with brain tissue, immune and developmental processes. Also, the presence of pG4-BS on both template and non-template strands in promoters is associated with oncogenesis, cardiovascular disease and stemness. Our G4-BS models predicted G4-forming ability in vitro with 91.5% accuracy. Analysis of G4-seq and CUT&Tag data strongly supports the existence of G4-BS conformations genome-wide. We reconstructed a novel G4-B 3D structure located in the E2F8 promoter. This study defines a large family of G4-like sequences, offering new insights into the essential biological functions and potential future therapeutic uses of G4-B. Agency for Science, Technology and Research (A*STAR) Nanyang Technological University Published version Bioinformatics Institute, Biomedical Institutes/A-STAR, Singapore (in part); V.A.K. was supported by a SUNY EMPIRE innovation program scholar grant; Upstate Medical University Cancer Center grant; Upstate Foundation Turn4ACure Fund; research in A.T.P. lab was supported by Nanyang Technological University Singapore; P.J. was supported by the Office of the Permanent Secretary, Ministry of Higher Education, Science, Research and Innovation (OPS MHESI); Thailand Science Research and Innovation (TSRI) [RGNS 64-161]. Funding for open access charge: SUNY EMPIRE innovation program scholar grant, the Upstate Medical University Cancer Center grant; Upstate Foundation Turn4ACure Fund.

A new protocol for the deoxygenation of alcohols and the hydrogenation of alkenes under Brønsted acid catalysis has been developed. The method is based on the use of either a benzyl or isopropyl ether as a traceless hydrogen‐atom donor, and involves an intramolecular hydride transfer as a key step, which is achieved in a regio‐ and stereoselective manner. MOE (Min. of Education, S’pore) Accepted version

The increased availability of ultrahigh-dimensional biomarker data and the high demand of identifying biomarkers importantly related to survival outcomes made feature screening methods commonplace in the analysis of cancer genome data. When survival outcomes include endpoints of overall survival (OS) and time-to-progression (TTP), a high concordance is typically found in both endpoints in cancer studies, namely, patients' OS would most likely be extended when tumour progression is delayed. Existing screening procedures are often performed on a single survival endpoint only and may result in biased selection of features for OS in ignorance of disease progression. We propose a novel feature screening method by incorporating information of TTP into the selection of important biomarker predictors for more accurate inference of OS subsequent to disease progression. The proposal is based on the rank of correlation between individual features and the conditional distribution of OS given observations of TTP. It is advantageous for its flexible model nature, which requires no marginal model assumption for each endpoint, and its minimal computational cost for implementation. Theoretical results show its ranking consistency, sure screening and false rate control properties. Simulation results demonstrate that the proposed screener leads to more accurate feature selection than the method without considering the prior observations of disease progression. An application to breast cancer genome data illustrates its practical utility and facilitates disease classification using selected biomarker predictors. Ministry of Education (MOE) Xiang’s research was partially supported by the Singapore Ministry of Education Academic Research Fund Tier 1 Grant (RG98/20) and Tier 2 Grant (MOE-T2EP20121-0004), and Peng’s research was partially supported by the National Key R&D Program of China (Nos. 2021YFA1000100 and 2021YFA1000101) and the National Natural Science Foundation of China (NSFC grant no. 92046005).

Neuromorphic computing (NC) is considered a potential vehicle for implementing energy-efficient artificial intelligence. To realize NC, several technologies are being investigated. Among them, the spin−orbit torque (SOT)- driven domain wall (DW) devices are one of the potential candidates. Researchers have proposed different device designs to achieve neurons and synapses, the building blocks of NC. However, the experimental realization of DW device-based NC is only at the primeval stage. Here, we have studied pine-tree DW devices, based on the Laplace pressure on the elastic DWs, for achieving synaptic functionalities and diode-like characteristics. We demonstrate an asymmetric pinning strength for DW motion in two opposite directions to show the potential of these devices as DW diodes. We have used micromagnetic simulations to understand the experimental findings and to estimate the Laplace pressure for various design parameters. The study provides a strategy to fabricate a multifunctional DW device, exhibiting synaptic properties and diode characteristics. Agency for Science, Technology and Research (A*STAR) National Research Foundation (NRF) Submitted/Accepted version The authors gratefully acknowledge the National Research Foundation (NRF), Singapore, for the CRP21 grant (NRFCRP21-2018-0003). They also acknowledge the support provided by Agency for Science, Technology and Research, A*STAR RIE2020 AME Grant No. A18A6b0057 for this work. H.R. thanks the NTU research scholarship for carrying out research at NTU.

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).

Three-dimensional/low-dimensional perovskite solar cells afford improved efficiency and stability. The design of low-dimensional capping materials is constrained to tuning the A-site organic cation, as Pb2+ and Sn2+ are the only options for the metal cation. Here we unlock access to a library of low-dimensional capping materials with metal cations beyond Pb2+/Sn2+ by processing a full precursor solution containing both metal and ammonium halides. This enables easier synthetic control of the low-dimensional capping layer and greater versatility for low-dimensional interface engineering. We demonstrate that a zero-dimensional zinc-based halogenometallate (PEA2ZnX4; PEA = phenethylammonium, X = Cl/I) induces more robust surface passivation and stronger n–N isotype three-dimensional/low-dimensional heterojunctions than its lead-based counterpart. We exhibit p–i–n solar cells with 24.1% efficiency (certified 23.25%). Our cells maintain 94.5% initial efficiency after >1,000 h of operation at the maximum power point. Our findings expand the material library for low-dimensional interface engineering and stabilization of highly efficient three-dimensional/low-dimensional perovskite solar cells. Ministry of Education (MOE) National Research Foundation (NRF) Submitted/Accepted version This work is supported by the Ministry of Singapore under its AcRF Tier 1 (Project RG6/21 (2021-T1-001-072) to Y.M.L.) and Tier 2 grants (MOE2019-T2-1-006 to T.C.S., MOE2019-T2-1-085 to Y.M.L. and MOE-T2EP50120-0004 to T.C.S.), and the National Research Foundation (NRF) Singapore under its NRF Investigatorship (NRF-NRFI2018-04 to T.C.S.).

The photoexcitation life cycle from incident photon (and creation of photoexcited electron–hole pair) to ultimate extraction of electrical current is a complex multiphysics process spanning across a range of spatiotemporal scales of quantum materials. Photocurrent is sensitive to a myriad of physical processes across these spatiotemporal scales, and over the past decade it has emerged as a versatile probe of electronic states, Bloch band quantum geometry, quantum kinetic processes and device characteristics of quantum materials. This Technical Review outlines the key multiphysics principles of photocurrent diagnostics, for resolving band structure and characterizing topological materials, for disentangling distinct types of carrier scattering that can range from femtosecond to nanosecond timescales and for enabling new types of remote-sensing protocols and photocurrent nanoscopy. These distinctive capabilities underscore photocurrent diagnostics as a novel multiphysics probe for a growing class of quantum materials with properties governed by physics spanning multiple spatiotemporal scales. Ministry of Education (MOE) Q.M. was supported through NSF Career DMR-2143426 and the CIFAR Azrieli Global Scholars programme. R.K.K. acknowledges the EU Horizon 2020 programme under the MarieSkłodowska-Curie grant numbers 754510 and 893030. S.-Y.X. was supported through NSF Career (Harvard fund 129522) DMR-2143177. F.H.L.K. acknowledges support from the ERC TOPONANOP (726001), the Government of Spain (PID2019-106875GB-I00; Severo Ochoa CEX2019-000910-S (MCIN/AEI/10.13039/501100011033)), Fundació Cellex, Fundació Mir-Puig and Generalitat de Catalunya (CERCA, AGAUR, SGR 1656). Furthermore, the research leading to these results has received funding from the European Union’s Horizon 2020 under grant agreement numbers 881603 (Graphene flagship Core3) and 820378 (Quantum flagship). J.C.W.S. acknowledges support from the Singapore MOE Academic Research Fund Tier 3 Grant number MOE2018-T3-1-002.

We measure the ultrafast spectral diffusion, vibronic dynamics, and energy relaxation of a CdSe colloidal quantum wells (CQWs) system at room temperature using two-dimensional electronic spectroscopy (2DES). The energy relaxation of light-hole (LH) excitons and hot carriers to heavy-hole (HH) excitons is resolved with a time scale of ∼210 fs. We observe the equilibration dynamics between the spectroscopically accessible HH excitonic state and a dark state with a time scale of ∼160 fs. We use the center line slope analysis to quantify the spectral diffusion dynamics in HH excitons, which contains an apparent sub-200 fs decay together with oscillatory features resolved at 4 and 25 meV. These observations can be explained by the coupling to various lattice phonon modes. We further perform quantum calculations that can replicate and explain the observed dynamics. The 4 meV mode is observed to be in the near-critically damped regime and may be mediating the transition between the bright and dark HH excitons. These findings show that 2DES can provide a comprehensive and detailed characterization of the ultrafast spectral properties in CQWs and similar nanomaterials. Agency for Science, Technology and Research (A*STAR) Ministry of Education (MOE) Submitted/Accepted version H.V.D. gratefully acknowledges the financial support in part from the Singapore Agency for Science, Technology and Research (A*STAR) SERC under Grant No. M21J9b0085, and the Singapore Ministry of Education Tier 1 grant (MOERG62/20). H.V.D. also gratefully acknowledges the support from TUBA. H.-S.T. gratefully acknowledges the financial support in part from the Singapore Ministry of Education Tier 1 grant (MOE-RG2/19 and MOE-RG14/20). O.V.P. acknowledges the financial support from the United States National Science Foundation under Grant No. CHE-2154367.

Background: Recognizing the relatively few studies that have explored university students’ understanding and alternative conceptions in linear and circular motion as well as the relatively few studies that have used 2-dimensional multiple-choice questions (MCQs) in the science education literature, this study set out to contribute to these areas. Purpose: To investigate undergraduates’ understanding of velocities and accelerations in linear and circular motions using 2-dimensional MCQs. Sample: 450 engineering undergraduates who were doing a Physics course. Design and methods: A 2-dimensional MCQ instrument comprising 8 questions was developed and administered to the samples. Both cognitive scores and metacognitive measures were extracted as part of data analyses. Incorrect responses which were at least at the 10% threshold level were classified as alternative conceptions (ACs). Results: Both cognitive scores and metacognitive measures have afforded a more nuanced appreciation of students’ understanding as well as their ACs on the topics. In this context, we report on confidence when correct, confidence when wrong, confidence with which the ACs are expressed and confidence accuracy quotient for each question. Student responses led to the identification of 14 ACs. It was noted that students’ understanding of key concepts in the topics tested is rather modest. A commentary is presented on these ACs from the lens of instructor teaching experience. Conclusion: Two dimensional MCQs were found to be effective in exploring undergraduates’ understanding of linear and circular motions as well as in documenting their alternative conceptions.

The development of integrated circuits (ICs) based on a complementary metal−oxide−semiconductor through transistor scaling has reached the technology bottleneck; thus, alternative approaches from new physical mechanisms are highly demanded. Valleytronics in two-dimensional (2D) material systems has recently emerged as a strong candidate, which utilizes the valley degree of freedom to process information for electronic applications. However, for all-electrical valleytronic transistors, very low room- temperature “valley on−off” ratios (around 10) have been reported so far, which seriously limits their practical applications. In this work, we successfully illustrated both n- and p-type valleytronic transistor performances in monolayer MoS2 and WSe2 devices, with measured “valley on−off” ratios improved up to 3 orders of magnitude greater compared to previous reports. Our work shows a promising way for the electrically controllable manipulation of valley degree of freedom toward practical device applications. Ministry of Education (MOE) National Research Foundation (NRF) Submitted/Accepted version This work was supported by the Singapore National Research Foundation through its Competitive Research Program (CRP Award No. NRF-CRP22-2019-0004 and Quantum engineering programme), the Singapore Ministry of Education (MOE2016-T3-1-006 (S)), and the Start-up Research Grant of University of Macau (SRG2022-00030-IAPME).

Mixed-dimensional perovskites containing mixtures of organic cations hold great promise to deliver highly stable and efficient solar cells. However, although a plethora of relatively bulky organic cations have been reported for such purposes, a fundamental understanding of the materials’ structure, composition, and phase, along with their correlated effects on the corresponding optoelectronic properties and degradation mechanism remains elusive. Herein, we systematically engineer the structures of bulky organic cations to template low-dimensional perovskites with contrasting inorganic framework dimensionality, connectivity, and coordination deformation. By combining X-ray single-crystal structural analysis with depth-profiling XPS, solid-state NMR, and femtosecond transient absorption, it is revealed that not all low dimensional species work equally well as dopants. Instead, it was found that inorganic architectures with lesser structural distortion tend to yield less disordered energetic and defect landscapes in the resulting mixed-dimensional perovskites, augmented in materials with a longer photoluminescence (PL) lifetime, higher PL quantum yield (up to 11%), improved solar cell performance and enhanced thermal stability (T80 up to 1000 h, unencapsulated). Our study highlights the importance of designing templating organic cations that yield low-dimensional materials with much less structural distortion profiles to be used as additives in stable and efficient perovskite solar cells. Ministry of Education (MOE) National Research Foundation (NRF) Published version The authors would like to acknowledge funding from the Singapore National Research Foundation through the IntraCREATE Collaborative Grant (NRF2018-ITC001-001), Energy Innovation Research Program (NRF2015EWT-EIRP003-004 and Solar CRP: S18-1176-SCRP), and MOE Tier 2 project MOE2019-T2-2-097.

Lead based halide perovskites have made great progress in various fields especially optoelectronic devices, but the health risk caused by heavy metal lead strongly blocks their widespread applications. Therefore, Pb free perovskites such as Sn based halide perovskites have been proposed and are expected to address the toxicity issue. However, until now, the toxicity and environmental impact of tin-based halide perovskites are still debated. This even raised a critical question about whether it is still worth deploying tin-containing halide perovskites which needs to be answered urgently but has so far remained elusive. In this work, we carefully analyse the practical application conditions of tin-based halide perovskites e.g., solar cells and conduct a comprehensive toxicity evaluation under these realistic situations. Our results including the organ weight index, blood analysis, immunohistochemistry (IHC) tests and next generation sequencing (RNA sequencing) demonstrated that even in the worst condition of large-scale applications of Sn based halide perovskites, neither obvious acute toxicity nor risk at a gene level can be observed. Thus, we conclude that Sn based halide perovskites are bio safe and substituting lead with tin in halide perovskites is applicable. Agency for Science, Technology and Research (A*STAR) Submitted/Accepted version This work was supported by A*STAR under project AME-IRGA20E5c0083, The Science and Technology Development Fund (FDCT) grants (0065/2022/A2, 0097/2021/A2, 0045/2021/AFJ, and 0092/2020/AMJ) of Macau SAR, China, and the Natural Science Foundation of China (NSFC): 82030094.

In this communication, we report a new class of oscillation mode, dome-shaped mode (DSM), in liquid crystal (LC) microlasers. A record high Q-factor over 24 000 is achieved in LC soft-matter microlasers. We successfully presented a proof-of-concept demonstration of red, green, blue (RGB) LC-DSM microlaser pixels with a 74% broader achievable color gamut than the standard RGB color space. Besides, the detection limit for acetone vapor molecules is as low as 0.5 ppm, confirming the excellent potential of the proposed LC-DSM microlaser in ultra-high sensitivity detection. Agency for Science, Technology and Research (A*STAR) Published version This work is supported by A*Star-AME-IRG-A20E5c0083, NRF-CRP23-2019-0007. V. D. T. acknowledges the support from the Vietnam National Foundation for Science and Technology Development (NAFOSTED) under grant number 103.03- 2021.62. J. Y. also acknowledges the support from the National Science Fund for Distinguished Young Scholars of China (61925501), the Guangdong Introducing Innovative and Entrepreneurial Teams (2019ZT08X340) and Introducing Leading Talents (2019CX01X010) of ‘‘The Pearl River Talent Recruitment Program’’ of Guangdong Province.

The accumulation of positive charges at the anodic interface considerably limits the efficiency of photovoltaic solar cells based on polymer/fullerene bulk heterojunctions (BHJs). Interfacial layers (IFLs) such as PEDOT:PSS improve charge injection but have no effect on the unbalanced electron/hole transport across the BHJ. We report here the use of 2,2′,6,6′-tetraphenyl-dipyranylidene (DIPO-Ph4), a planar quinoïd compound, as an efficient anodic IFL in organic solar cells based on BHJs made of poly(3-hexylthiophene)/[6,6]-phenyl-C61-butyric-acid-methyl-ester (P3HT:PCBM). When deposited under vacuum onto a glass substrate, DIPO-Ph4 thin films are constituted of densely packed and vertically aligned crystalline needles. Current-sensing atomic force microscopy (CS-AFM) reveals a considerable increase of the hole-carrying pathways in DIPO-Ph4 thin films as compare to PEDOT:PSS, thus revealing their hole transporting/electron blocking properties. Inserting a 10 nm thick IFL of DIPO-Ph4 in combination with a 5 nm thick PEDOT:PSS between the ITO electrode and the P3HT:PCBM film leads to photocurrent densities up to 11.5 mA/cm2 under AM 1.5G and conversion efficiencies up to 4.6%, that is substantially higher than PEDOT:PSS-only devices. MOE (Min. of Education, S’pore)

Denitrogenative 6-endo-dig azide-yne cyclization of α-propargyloxy-β-haloalkylazides was enabled by gold catalysis, thus providing 2H-1,3-oxazines. This rare cyclization mode in gold-catalyzed reactions of azide-yne substrates was demonstrated to be facilitated and controlled by electronic and resonance effects of the alkyne substituents. Molecular transformations of the as-prepared 2H-1,3-oxazines were also investigated. Ministry of Education (MOE) Nanyang Technological University Accepted version This work was supported by funding from Ecole Polytechnique (for F. G.), Nanyang Technological University (for S. C.) and the Singapore Ministry of Education (Academic Research Fund Tier 2: MOE2013-T2-1-060 for S. C.). F. G. and S. C. are grateful to PHC Merlion grant (Project 5.02.15) for the support of this collaboration project.

We report on a new phenoxazine derivative, 10-butyl-phenoxazine-3-carboxylic acid (BPCA), that we designed to operate as a molecular relay in semiconductor-sensitized solar cells (SSCs). After BPCA surface modification and in the presence of a cobalt-bipyridyl complex acting as a redox mediator, both TiO2/CdS/BPCA and TiO2/CdSe/BPCA SSCs exhibit enhanced photovoltaic performance and stability. In particular, the power conversion efficiencies of CdS and CdSe-based solar cells are improved by 90 % and 57 %, respectively. Furthermore, after 300 s the JSC of TiO2/CdS/BPCA SSCs is stabilized at 30 % of its initial value, while in the same time CdS-based devices retain only 1 % of their initial JSC. The origin of the improvement arises from the excellent electron-donating property of BPCA and its role as a powerful molecular relay in non-polysulfide based SSCs. MOE (Min. of Education, S’pore) NRF (Natl Research Foundation, S’pore)

A Pd/Ca catalytic system to promote the unsymmetrical bis-allylation of malononitrile was developed by selecting conjugated dienes and allylic alcohols as allylic reagents. This catalytic system suppressed the competitive symmetrical bis-allylation process and guaranteed the desired unsymmetrical bis-allylation with high chemoselectivity. A wide range of conjugated dienes and allylic alcohols were tolerated well in this transformation, and diverse 1,6-dienes were obtained with high efficiency. We gratefully acknowledge financial support from the National Natural Science Foundation of China (21702108); the Natural Science Foundation of Jiangsu Province, China (BK20211257 and BK20160977); and the Six Talent Peaks Project in Jiangsu Province (YY-033).

Cryptanalysts have been looking for differential characteristics in ciphers for decades and it remains unclear how the subkey values and more generally the Markov assumption impacts exactly their probability estimation. There were theoretical efforts considering some simple linear relationships between differential characteristics and subkey values, but the community has not yet explored many possible nonlinear dependencies one can find in differential characteristics. Meanwhile, the overwhelming majority of cryptanalysis works still assume complete independence between the cipher rounds. We give here a practical framework and a corresponding tool to investigate all such linear or nonlinear effects and we show that they can have an important impact on the security analysis of many ciphers. Surprisingly, this invalidates many differential characteristics that appeared in the literature in the past years: we have checked differential characteristics from 8 articles (4 each for both SKINNY and GIFT) and most of these published paths are impossible or working only for a very small proportion of the key space. We applied our method to SKINNY and GIFT, but we expect more impossibilities for other ciphers. To showcase our advances in the dependencies analysis, in the case of SKINNY we are able to obtain a more accurate probability distribution of a differential characteristic with respect to the keys (with practical verification when it is computationally feasible). Our work indicates that newly proposed differential characteristics should now come with an analysis of how the key values and the Markov assumption might or might not affect/invalidate them. In this direction, more constructively, we include a proof of concept of how one can incorporate additional constraints into Constraint Programming so that the search for differential characteristics can avoid (to a large extent) differential characteristics that are actually impossible due to dependency issues our tool detected. Published version

Implementation-based attacks are major concerns for modern cryptography. For symmetric-key cryptography, a significant amount of exploration has taken place in this regard for primitives such as block ciphers. Concerning symmetric-key operating modes, such as Authenticated Encryption with Associated Data (AEAD), the state-of-the-art mainly addresses the passive Side-Channel Attacks (SCA) in the form of leakage resilient cryptography. So far, only a handful of work address Fault Attacks (FA) in the context of AEADs concerning the fundamental properties – integrity and confidentiality. In this paper, we address this gap by exploring mode-level issues arising due to FAs. We emphasize that FAs can be fatal even in cases where the adversary does not aim to extract the long-term secret, but rather tries to violate the basic security requirements (integrity and confidentiality). Notably, we show novel integrity attack examples on state-of-the-art AEAD constructions and even on a prior fault-resilient AEAD construction called SIV$. On the constructive side, we first present new security notions of fault-resilience, for PRF (frPRF), MAC (frMAC) and AEAD (frAE), the latter can be seen as an improved version of the notion introduced by Fischlin and Gunther at CT-RSA’20. Then, we propose new constructions to turn a frPRF into a fault-resilient MAC frMAC (hash-then-frPRF) and into a fault-resilient AEAD frAE (MAC-then-Encrypt-then-MAC or MEM). Nanyang Technological University Published version This work was supported by a joint Wallenberg AI, Autonomous Systems and SoftwareProgram-Nanyang Technological Universy (WASP-NTU) grant.

The optical responses of metals are often dominated by plasmonic resonances, that is, the collective oscillations of interacting electron liquids. Here we unveil a new class of plasmons─quantum metric plasmons (QMPs)─that arise in a wide range of parity-violating magnetic metals. In these materials, a dipolar distribution of the quantum metric (a fundamental characteristic of Bloch wave functions) produces intrinsic nonreciprocal bulk plasmons. Strikingly, QMP nonreciprocity manifests even when the single-particle dispersion is symmetric: QMPs are sensitive to time-reversal and parity violations hidden in the Bloch wave function. In materials with asymmetric single-particle dispersions, quantum metric dipole induced nonreciprocity can continue to dominate at large frequencies. We anticipate that QMPs can be realized in a wide range of parity-violating magnets, including twisted bilayer graphene heterostructures, where quantum geometric quantities can achieve large values. Ministry of Education (MOE) Nanyang Technological University This work was supported by Singapore MOE Academic Research Fund Tier 3 Grant MOE2018-T3-1-002 and a Nanyang Technological University start-up grant (NTUSUG).

We introduce a new method which, for a single noisy time series, provides unsupervised filtering, state space reconstruction, efficient learning of the unknown governing multivariate dynamical system, and deterministic forecasting. We construct both the underlying trajectories and a latent dynamical system using deep neural networks. Under the assumption that the trajectories follow the latent dynamical system, we determine the unknowns of the dynamical system, and filter out stochastic outliers in the measurements. In this sense the method is self-consistent. The embedding dimension is determined iteratively during the training by using the false-nearest-neighbors Algorithm and it is implemented as an attention map to the state vector. This allows for a state space reconstruction without a priori information on the signal. By exploiting the differentiability of the neural solution trajectory, we can define the neural dynamical system locally at each time, mitigating the need for forward and backwards passing through numerical solvers of the canonical adjoint method. On a chaotic time series masked by additive Gaussian noise, we demonstrate that the denoising ability and the predictive power of the proposed method are mainly due to the self-consistency, insensitive to methods used for the state space reconstruction. Nanyang Technological University National Research Foundation (NRF) The work of Zhe Wang was supported by Energy Research Institute@NTU, Nanyang Technological University, where most of this work was performed. This work was supported by the National Research Foundation, Prime Minister’s Office, Singapore under its Campus for Research Excellence and Technological Enterprise (CREATE) programme.

A new acceptor moiety, γ-lactone-Pechmann dye is synthesized and used in the construction of two new conjugated D-A polymers. The optical and electrochemical characterization shows a broad absorption band extended to 1000 nm and narrow band gaps with deep LUMO energy levels. The chemical structures of the side chains appended from the donor units affect the intermolecular aggregation and the charge transport in thin-film field-effect transistors. The high degree of planarity, low bandgap, and strong electron accepting properties could make γ-lactone-Pechmann dye as a good candidate for the construction of conjugated D-A polymers.

The paradigmatic example of a topological phase of matter, the two-dimensional Chern insulator1-5, is characterized by a topological invariant consisting of a single integer, the scalar Chern number. Extending the Chern insulator phase from two to three dimensions requires generalization of the Chern number to a three-vector6,7, similar to the three-dimensional (3D) quantum Hall effect8-13. Such Chern vectors for 3D Chern insulators have never been explored experimentally. Here we use magnetically tunable 3D photonic crystals to achieve the experimental demonstration of Chern vectors and their topological surface states. We demonstrate Chern vector magnitudes of up to six, higher than all scalar Chern numbers previously realized in topological materials. The isofrequency contours formed by the topological surface states in the surface Brillouin zone form torus knots or links, whose characteristic integers are determined by the Chern vectors. We demonstrate a sample with surface states forming a (2, 2) torus link or Hopf link in the surface Brillouin zone, which is topologically distinct from the surface states of other 3D topological phases. These results establish the Chern vector as an intrinsic bulk topological invariant in 3D topological materials, with surface states possessing unique topological characteristics. Ministry of Education (MOE) National Research Foundation (NRF) Submitted/Accepted version We acknowledge funding from the Singapore National Research Foundation Competitive Research Program (grant no. NRF-CRP23-2019-0007) and Singapore Ministry of Education Academic Research Fund Tier 3 (grant no. MOE2016-T3-1-006). P.Z., Z.G. and Y.Y. acknowledge funding from the National Natural Science Foundation of China (grant nos. 52022018, 52021001, 12104211, 6101020101 and 62175215) and Chinese Academy of Engineering (grant no. 2022-XY-127).

We report amphiphilicity-driven self-assembly of polymer-coated magnetoplasmonic Janus nanoparticles (JNP) that result in well-defined colloidal ensembles with controllable size, morphology, and dimension. The amphiphilic JNP building blocks were prepared by coating fluorescent dye-conjugated pH-responsive block copolymer (BCP) and hydrophilic polymers on plasmonic and magnetic side of the JNPs, respectively. Our results have demonstrated a direct correlation between the amphiphilicity of the JNP building block and the structural parameters of corresponding ensembles. It was found that the increase in the relative ratio of pH-responsive hydrophobic BCP and hydrophilic polymer grafts on two different parts of the JNP led to a morphological transition of assemblies from micellar cluster to lamellae to vesicle. It provides insight into the colloidal self-assembly of functional nanocrystal. Furthermore, the coating of well-defined BCP grafts on the gold nanoparticle (AuNP) of the JNPs offers the possibilities to finely tune the interparticle distance and precisely position dye molecules at the gap between neighboring JNPs in the ensembles, and the pH-sensitivity of the BCP allows to control the interparticle distance as a function of pH. Such dye-encoded magnetoplasmonic ensembles can serve as a well-defined platform to study the metal-fluorophore interaction, leading to an improved fundamental understanding of metal-enhanced fluorescence (MEF) process. The fluorescent magnetoplasmonic ensembles with defined morphologies (i.e., multimers and vesicles) are of broad interest for biomedical applications that require synergistic multifunctionalies such as theranostics and biosensors. Ministry of Education (MOE) Submitted/Accepted version H.D. is grateful to the Ministry of Education Singapore for financial support (MOE2015-T2-1-112 and MOE2018-T2-2- 128).

This paper establishes a general analytical framework for classical and impulse stochastic control problems in the presence of model uncertainty. We consider a set of dominated models, which are induced by the measures equivalent to that of a reference model. The state process under the reference model is a multidimensional Markov process with multidimensional Brownian motion, controlled by continuous and impulse control variates. We propose quasi-variational inequalities (QVI) associated with the value function of the control problem and prove a verification theorem for the solution to the QVI. With the relative entropy constraints and piecewise linear intervention penalty, we show that the QVI can be degenerated to the non-robust case and it can be solved via the solution to a free boundary problem. To illustrate the tractability of the proposed framework, we apply it to a linear-quadratic setting, which covers a broad class of problems including robust mean-reverting inventory controls. Ministry of Education (MOE) Chi Seng Pun gratefully acknowledges Ministry of Education (MOE), AcRF Tier 2 grant (Reference No: MOE2017-T2-1-044) for the funding of this research.

Carrier diffusion and surface recombination are key processes influencing the performance of conventional semiconductor devices. However, the interplay of photon recycling together with these processes in halide perovskites obfuscates our understanding. Herein, we discern these inherent processes in a thin FAPbBr3 perovskite single crystal (PSC) utilizing a unique transient reflectance technique that allows accurate diffusion modeling with clear boundary conditions. Temperature-dependent measurements reveal the coexistence of shallow and deep traps at the surface. The inverse quadratic dependence of temperature on carrier mobility μ suggests an underlying scattering mechanism arising from the anharmonic deformation of the PbBr6 cage. Our findings ascertain the fundamental limits of the intrinsic surface recombination velocity (S) and carrier diffusion coefficient (D) in PSC samples. Importantly, these insights will help resolve the ongoing debate and clarify the ambiguity surrounding the contributions of photon recycling and carrier diffusion in perovskite optoelectronics. Ministry of Education (MOE) National Research Foundation (NRF) Submitted/Accepted version This research/project is supported by the Ministry of Education under its AcRF Tier 2 grants (MOE2019-T2-1-006, MOE2019-T2-1-097 and MOE-T2EP50120-0004); and the National Research Foundation (NRF) Singapore under its NRF Investigatorship (NRF-NRFI-2018-04).

Recently, the Ramprasad group reported a quantitative structure–property relationship (QSPR) model for predicting the Egap values of 4209 polymers, which yielded a test set R2 score of 0.90 and a test set root-mean-square error (RMSE) score of 0.44 at a train/test split ratio of 80/20. In this paper, we present a new QSPR model named LGB-Stack, which performs a two-level stacked generalization using the light gradient boosting machine. At level 1, multiple weak models are trained, and at level 2, they are combined into a strong final model. Four molecular fingerprints were generated from the simplified molecular input line entry system notations of the polymers. They were trimmed using recursive feature elimination and used as the initial input features for training the weak models. The output predictions of the weak models were used as the new input features for training the final model, which completes the LGB-Stack model training process. Our results show that the best test set R2 and the RMSE scores of LGB-Stack at the train/test split ratio of 80/20 were 0.92 and 0.41, respectively. The accuracy scores further improved to 0.94 and 0.34, respectively, when the train/test split ratio of 95/5 was used. Ministry of Education (MOE) Published version This research was supported by the Ministry of Education, Singapore, under its Academic Research Fund Tier 1 RG83/20.

For more than a century, abnormal nuclei in tumor cells, presenting subnuclear invaginations and folds on the nuclear envelope, have been known to be associated with high malignancy and poor prognosis. However, current nuclear morphology analysis focuses on the features of the entire nucleus, overlooking the malignancy-related subnuclear features in nanometer scale. The main technical challenge is to probe such tiny and randomly distributed features inside cells. We here employ nanopillar arrays to guide subnuclear features into ordered patterns, enabling their quantification as a strong indicator of cell malignancy. Both breast and liver cancer cells were validated as well as the quantification of nuclear abnormality heterogeneity. The alterations of subnuclear patterns were also explored as effective readouts for drug treatment. We envision that this nanopillar-enabled quantification of subnuclear abnormal features in tumor cells opens a new angle in characterizing malignant cells and studying the unique nuclear biology in cancer. Ministry of Education (MOE) Nanyang Technological University National Research Foundation (NRF) This work is supported by the Singapore Ministry of Education (MOE) (W.Z., RG145/18 and RG112/20), the Singapore National Research Foundation (W.Z., NRF2019-NRF-ISF003- 3292), the Institute for Digital Molecular Analytics and Science (IDMxS) supported by MOE funding under the Research Centres of Excellence scheme (W.Z.), the NTU Start-up Grant (W.Z.), the NTU-NNI Neurotechnology Fellowship (W.Z.), and AIRC IG-24614 and Sapienza AR1181642EE61111 (I.S.).

On-chip optical communications are in increasingly demand for low-loss, small-footprint and power-efficient waveguiding solutions in the telecom band. However, most integrated optical circuits suffer from high propagation loss and low integration degree. Through manipulating the valley-dependent topological phase of light, we have experimentally demonstrated both robust optical transport and electrical modulation of lightwaves at telecom wavelengths in the valley photonic crystals. With the adoption of valley kink states, the 25 Gbit/s optical signal at 1550 nm is successfully transmitted through a highly twisted interface. Furthermore, an extreme high data rate of 100 Gbit/s is demonstrated with such topological waveguide by wavelength division multiplexing. The electrical tunability of the topological modulators based on thermo-optic effect is also verified, opening a novel route towards active valley kink photonic devices. Our study shows a great possibility of making use of the topological protection in building up high-speed datalinks on a chip. Published version This work was supported by the Innovation and Entrepreneurship Program of Jiangsu Province (JSSCBS20210467), the Natural Science Foundation of the Jiangsu Higher Institution of China (21KJB140012), the Natural Science Foundation of Jiangsu Province (SBK2021041180), the National Natural Science Foundation of China (62105158, 62075038).

Organic electrochemical transistors (OECTs) have recently attracted attention due to their high transconductance and low operating voltage, which makes them ideal for a wide range of biosensing applications. Poly-3,4-ethylenedioxythiophene:poly-4-styrenesulfonate (PEDOT:PSS) is a typical material used as the active channel layer in OECTs. Pristine PEDOT:PSS has poor electrical conductivity and additives are typically introduced to improve its conductivity and OECT performance. However, these additives are mostly either toxic or not proved to be biocompatible. Herein, a biocompatible ionic liquid [MTEOA][MeOSO3] is demonstrated to be an effective additive to enhance the performance of PEDOT:PSS based OECTs. The influence of [MTEOA][MeOSO3] on the conductivity, morphology and the redox process of PEDOT:PSS are investigated. The PEDOT:PSS/[MTEOA][MeOSO3] based OECT exhibits high transconductance (22.3 ± 4.5 mS μm-1), high μC* (the product of mobility μ and volumetric capacitance C*) (283.80 ± 29.66 F cm-1 V-1 s-1), fast response time (~40.57 μs) and excellent switching cyclical stability. Next, the integration of sodium (Na+) and potassium (K+) ion-selective membranes with the OECTs is demonstrated, enabling selective ions detection in the physiological range. In addition, flexible OECTs are designed for electrophysiological (ECG) signals acquisition. These OECTs have shown robust performance against physical deformation and successfully recorded high quality ECG signals. Agency for Science, Technology and Research (A*STAR) Ministry of Education (MOE) Submitted/Accepted version W.L.L. would like to acknowledge funding support from Ministry of Education (MOE) under AcRF Tier 2 Grant (MOE2019-T2-2-106) and National Robotics Programme (W1925d0106). We would like to acknowledge the Facility for Analysis, Characterization, Testing and Simulation (FACTS) and the School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, for use of their GIWAXS, XPS and AFM facilities.

Constructing hierarchical structure is an effective strategy to boost the electrochemical performance of layered double hydroxide (LDH) materials, but the rational design of such delicate architectures is still challenging. Herein, a unique hierarchical core/shell homostructure with NiCo-LDH nanorods (NCNRs) as core and NiCo-LDH nanosheets (NCNSs) as shell is constructed via in-situ ZIF shell growth and subsequent ion exchange-coprecipitation process. Such novel hierarchical structure provides a large accessible surface area and more exposed electrochemical active sites. The in-situ growth and conversion process contribute to the formation of robust adhesion between the core and the shell, which could facilitate the effective charge and ion diffusion, as well as improve the mechanical stability. Benefiting from the unique structure, the NCNRs@NCNSs electrode exhibits a high capacitance of 2640.2 F g-1, along with the good rate performance and cyclic stability. Furthermore, the as-assembled asymmetric supercapacitor of NCNRs@NCNSs//AC device displays a high energy density of 22.81 Wh kg-1 at the power density of 374.95 W kg-1. This work demonstrates a new strategy for designing hierarchical LDH with core/shell structure as electrode materials for superior electrochemical energy storage. The authors are thankful to funds from the National Natural Science Foundation of China (52002194 and 51802168), Natural Science Foundation of Shandong Province (ZR2020QE065), the China Postdoctoral Science Foundation (2019M652317), the Shandong Postdoctoral Innovation Project, the Qingdao Postdoctoral Application Research Project and Shandong Double Hundred Foreign Experts program.

Photon-mediated interactions within an excited ensemble of emitters can result in Dicke superradiance, where the emission rate is greatly enhanced, manifesting as a high-intensity burst at short times. The superradiant burst is most commonly observed in systems with long-range interactions between the emitters, although the minimal interaction range remains unknown. Here, we put forward a new theoretical method to bound the maximum emission rate by upper bounding the spectral radius of an auxiliary Hamiltonian. We harness this tool to prove that for an arbitrary ordered array with only nearest-neighbor interactions in all dimensions, a superradiant burst is not physically observable. We show that Dicke superradiance requires minimally the inclusion of next-nearest-neighbor interactions. For exponentially decaying interactions, the critical coupling is found to be asymptotically independent of the number of emitters in all dimensions, thereby defining the threshold interaction range where the collective enhancement balances out the decoherence effects. Our findings provide key physical insights to the understanding of collective decay in many-body quantum systems, and the designing of superradiant emission in physical systems for applications such as energy harvesting and quantum sensing., 5 pages, 4 figures

Predicting the origin-destination (OD) probability distribution of agent transfer is an important problem for managing complex systems. However, prediction accuracy of associated statistical estimators suffer from underdetermination. While specific techniques have been proposed to overcome this deficiency, there still lacks a general approach. Here, we propose a deep neural network framework with gated recurrent units (DNNGRU) to address this gap. Our DNNGRU is \emph{network-free}, as it is trained by supervised learning with time-series data on the volume of agents passing through edges. We use it to investigate how network topologies affect OD prediction accuracy, where performance enhancement is observed to depend on the degree of overlap between paths taken by different ODs. By comparing against methods that give exact results, we demonstrate the near-optimal performance of our DNNGRU, which we found to consistently outperform existing methods and alternative neural network architectures, under diverse data generation scenarios., Main text, with supplemental material

Introduction: In recent years, we witnessed increasing numbers of migrants worldwide owing to famine, poverty, regional conflicts, etc. Efforts by the United Nations and various organizations to help these migrants are hampered by rising anti-migrant sentiments and xenophobic rhetoric in many parts of the world. To arrive at win-win solutions that benefit both natives and migrants, we must discuss the migration problem objectively and scientifically. To do this, we must first resolve the paradox in our understanding of human migration (widely touted as good) vis-a-vis biological invasion (generally regarded as bad).Method: Suspecting that the two similar phenomena are more complex than we think, we reviewed and synthesized the disjoint literatures on human migration and biological invasion in recent times, and that on the human diaspora and human-aided dispersal of plants and animals in our pre-historic past. We then developed models of niche-niche interactions to simulate isolated ecosystems and communities, as well as those experiencing invasions from non-native populations.Results: In this paper, we simulated four invasion mechanisms on a star network: the direct introduction of a non-native population into existing periphery or core niches, or the non-native population first creating its own niche, which is thereafter attached to the periphery or core of the community. We found that periphery invasions can fail, i.e., the non-native population eventually disappears. When periphery invasion is successful, we found that there is little or no harm to the ecosystem or community. On the other hand, core invasion is always catastrophic, where the non-native population establishes itself at the expense of most or all of the native populations. For niche attachments, whether to the periphery or to the core, we found native and non-native populations coexisting in the end, sometimes with increased diversities.Discussion: Our results provide promising new insights and theoretical grounds for policymakers to discuss the ethics of immigration issues scientifically, and to ultimately discover win-win solutions for natives and migrants. The theoretical framework outlined in this paper can also be applied to the problem of introducing non-native biological species for economic gains, at acceptable ecological costs.

Neutral excitations in fractional quantum Hall (FQH) fluids define the incompressibility of topological phases, a species of which can show graviton-like behaviors and are thus called the graviton modes (GMs). Here, we develop the microscopic theory for multiple GMs in FQH fluids and show explicitly that they are associated with the geometric fluctuation of well-defined conformal Hilbert spaces (CHSs), which are hierarchical subspaces within a single Landau level, each with emergent conformal symmetry and continuously parameterized by a unimodular metric. This leads to several statements about the number and the merging/splitting of GMs, which are verified numerically with both model and realistic interactions. We also discuss how the microscopic theory can serve as the basis for the additional Haldane modes in the effective field theory description and their experimental relevance to realistic electron-electron interactions., 10 pages, 7 figures, comments very welcome

Terahertz (THz) radiation has broad applications ranging from medical imaging to spectroscopy due to its useful properties, such as strong absorption by organic materials. One viable source of high-intensity THz radiation is the Smith-Purcell (SP) effect, which 1 involves charge carriers moving over a periodic surface. Conventional SP emitters use electron beams to generate charge carriers, necessitating bulky electron acceleration stages. Here, we propose a compact design for generating THz SP radiation using mobile charge carriers within 2D materials. This circumvents the beam alignment and beam divergence challenge, allowing for a reduction in the electron-grating separation from tens of nm to 5 nm or less, leading to more efficient near-field excitation and a potentially chip-level THz source. In such a configuration, we show that the optimal electron velocity and the corresponding maximum radiation intensity can be predicted from the electron-grating separation. For graphene on a silicon grating, we numerically demonstrate how SP radiation is excited by hot electrons, including how the radiation intensity can be enhanced by graphene surface plasmons and modified by tuning the Fermi level in the graphene sheet. Due to the high carrier concentration in graphene, the radiation intensity may be further enhanced through coherent interference. This study can be extended to a broad variety of charge carriers in 2D materials, including electrons, holes, and trions, mobilized through various means such as photoexcitation and external electric fields. Utilizing intrinsic mobile carriers in 2D materials may thus allow for compact, tunable, and low-cost THz sources. Agency for Science, Technology and Research (A*STAR) National Research Foundation (NRF) Submitted/Accepted version This work was supported by the National Research Foundation Singapore via Grant No. NRF-CRP26-2021-0004. L.W. gratefully acknowledges the Singapore University of Technology and Design for the Start-Up Research Grant SRG SMT 2021169 and Kickstarter Initiative (SKI) SKI 2021-02-14, and the National Re-search Foundation Singapore via Grant No. NRF2021-QEP2-02-P03 and NRF2021-QEP2-03-P09. S.L. acknowledges the A∗STAR National Science Scholarship. W.J.D acknowledges the support of the National Research Foundation Singapore via Grant No. NRF-CRP17-2017-08. L.J.W. acknowledges the support of the National Research Foundation Singapore Grant No. NRF2020-NRF-ISF004-3525. J.H.T. acknowledges the support of the Agency for Science, Technology and Research (A*STAR) AME IRG GrantA20E5c0084.

Infrared machine vision system for object perception and recognition is becoming increasingly important in the Internet of Things era. However, the current system suffers from bulkiness and inefficiency as compared to the human retina with the intelligent and compact neural architecture. Here, we present a retina-inspired mid-infrared (MIR) optoelectronic device based on a two-dimensional (2D) heterostructure for simultaneous data perception and encoding. A single device can perceive the illumination intensity of a MIR stimulus signal, while encoding the intensity into a spike train based on a rate encoding algorithm for subsequent neuromorphic computing with the assistanceofanall-opticalexcitationmechanism, a stochastic near-infrared (NIR) sampling terminal. The device features wide dynamic working range, high encoding precision, and flexible adaption ability to the MIR intensity. Moreover, an inference accuracy more than 96% toMIR MNIST data set encoded by the device is achieved using a trained spiking neural network (SNN). Agency for Science, Technology and Research (A*STAR) Ministry of Education (MOE) National Medical Research Council (NMRC) National Research Foundation (NRF) Published version This work was supported by the Singapore Ministry of Education (MOE-T2EP50120-0009 (Q.J.W.)), Agency for Science, Technology and Research (A*STAR) (A18A7b0058 (Q.J.W.) and A2090b0144 (Q.J.W.)), National Medical Research Council (NMRC) (021528- 00001 (Q.J.W.)), and National Research Foundation Singapore (NRF-CRP22-2019-0007 (Q.J.W.)), National Key Research and Development Program of China (2022YFB2802803 (N.C.)), the Natural Science Foundation of China Project (61925104 (N.C.), 62031011 (N.C.)) and Major Key Project of PCL (N.C.), and F.H. acknowledges the support from the China Scholarship Council.

Quantum-dot-sensitized solar cells (QDSCs) are promising solar-energy-conversion devices, as low-cost alternatives to the prevailing photovoltaic technologies. Compared with molecular dyes, nanocrystalline quantum dot (QD) light absorbers exhibit higher molar extinction coefficients and a tunable photoresponse. However, the power-conversion efficiencies (PCEs) of QDSCs are generally below 9.5 %, far behind their molecular sensitizer counterparts (up to 13 %). These low PCEs have been attributed to a large free-energy loss during sensitizer regeneration, energy loss during the charge-carrier transport and transfer processes, and inefficient charge separation at the QD/electrolyte interfaces, and various interfacial engineering strategies for enhancing the PCE and cell stability have been reported. Herein, we review recent progress in the interfacial engineering of QDSCs and discuss future prospects for the development of highly efficient and stable QDSCs. NRF (Natl Research Foundation, S’pore) MOE (Min. of Education, S’pore)

International audience; The charge transport properties of 2,2 0 ,6,6 0-tetraphenyldipyranylidene (DIPO-Ph4 ), a large planar quinö ıd p-conjugated heterocycle, are investigated in field-effect transistor (FET) configuration and by conductive atomic force microscopy (c-AFM). The FET properties show a clear p-type behavior with a hole mobility up to 2 X 10 2 cm 2 V 11 and on/off ratio of 10 4. The transfer characteristics I d /V g present a clear hysteresis typical of a resistive memory effect. This memory effect is again observed by means of c-AFM in lateral mode using a nearby gold top-contact as the counter-electrode. The c-AFM current response recorded for variable distances d ¼ 0.5–9.0 mm between the AFM tip and the top electrode shows a resistive switching behavior in the low-voltage 0.0–3.0 V region. Repeated " write-read-erase-read " cycles performed at low frequency reveal a non-volatile memory effect in the form of high-resistance and low-resistance states with a stable on/off ratio of 102 during cycling operation.

Self-ordering degree of anodic alumina nanopores is related to the volume expansion of the aluminum oxide. However, little is known about how the ionic species derived from electrolyte affect parameters inducing self-ordering of the nanopores. The influence of sulfur incorporation into nanoporous anodic aluminum oxide (AAO) films on volume expansion and self-ordering degree has been investigated under potentiostatic conditions (14-25 V) in different sulfuric acid electrolytes (3-20 wt %), the average current densities of each anodization being in the range of 0.1-10 mA cm. Rutherford backscattering spectroscopy (RBS) reveals that the incorporation of sulfur species into AAO, as well as the volume expansion factor (VEF), follows a logarithmic dependence on the average current density regardless of the applied voltage and sulfuric acid concentration. The relationship between volume expansion and the S/Al ratio is linear for each concentration of acid in the electrolyte. Furthermore, self-ordering regimes are also revealed for each acid concentration at VEF in the range of 1.50-1.66. We suggest that plasticity, enhanced by sulfur incorporation, counterbalances the high mechanical stress generated by volume expansion, thus inducing new self-ordering regimes. These new regimes are dependent not only on VEF but also on a subtle equilibrium between stress and plasticity of the nanoporous AAO films., Work supported by the Spanish Ministry of Science and Innovation under project MAT2010-20798-05-01 and 05-05. The authors wish to thank the support from the Ministry of Education in Singapore under the AcRF Tier 2 (MOE2014-T2-1-132). I.M.B. thanks the Spanish National Research Council (CSIC) for a JAE-preDoc fellowship cofinanced by the European Social Fund. M.H.-V. thanks financial support under project CCG08-UAM/MAT-4024.

We investigate an online edge-weighted bipartite matching problem with general capacity constraints. In this problem, the resources are offline and nonreplenishable with different capacities. Demands arrive online and each requests a certain amount of resources. The goal is to maximize the reward generated by successful matches. We model the offline optimization problem as a deterministic linear program (LP) and present multiple randomized online algorithms based on the solution to the offline LP. We analyze the performance guarantee of each algorithm in terms of its competitive ratio (CR). Importantly, we introduce a re-solving heuristic that periodically recomputes the offline LP and uses the updated offline solution to guide the online algorithm decisions. We find that the algorithm's CR can be significantly improved when re-solving at carefully selected time steps. Finally, we investigate the value of the demand distribution in further improving the algorithm efficiency. We conduct extensive numerical studies to demonstrate the efficiency of the proposed algorithms. The effect of market conditions on the algorithm performance is also investigated. Ministry of Education (MOE) Submitted/Accepted version The research was partially supported by MOE Academic Research Fund Tier 1 (Grant RG17/21) and Tier 2 (Grant MOE2019-T2-1-045(S)).

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).

The immune system constitutes the fortifications that safeguard the body against bacterial infections. Artificial nanosystems possess many attractive properties including the ability to modulate the immune responses against bacterial infections. On the one hand, antigen-loaded nanosystems have emerged as a promising alternative to convensional vaccines, protecting the host from infection. On the other hand, immunity can be regulated by nanosystems to treat infections caused by bacteria and related diseases. Herein, we initially introduce the recent advances of artificial nanosystems in the development of different vaccines including subunit and toxoid vaccines. Then, we focus on discussing the employment of nanosystems for the activation of immunity, including innate and adaptive immunity, to treat bacteria-induced infectious diseases. In addition, nanosystems with immunosuppressive capabilities are also highlighted, which can restrain the overactivation of immune responses, thereby relieving inflammation in the face of infections. Finally, we discuss current challenges and provide perspectives for future development in this rapidly growing field. Thus, this review is expected to inspire more advanced research of using nanosystems to achieve immune regulation toward practical applications. Agency for Science, Technology and Research (A*STAR) National Research Foundation (NRF) This research is supported by the Singapore Agency for Science, Technology and Research (A*STAR) AME IRG (Grant A20E5c0081) and the Singapore National Research Foundation Investigatorship (Grant NRF-NRFI2018-03).