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Teleseismic full-waveform inversion has recently been applied to image subwavelength-scale lithospheric structures (typically a few tens of kilometers) by utilizing hybrid methods in which an efficient solver for the 1D background model is coupled with a full numerical solver for a small 3D target region. Among these hybrid methods, the coupling of the fre-quency–wavenumber technique with the spectral element method is one of the most com-putationally efficient ones. However, it is normally based on a single plane-wave incidence, and thus cannot synthesize secondary global phases generated at interfaces outside the target area. To remedy the situation, we propose to use a multiple plane-wave injection method to include secondary global phases in the hybrid modeling. We investigate the performance of the teleseismic full-waveform inversion based on single and multiple plane-wave incidence through an application in the western Pyrenees and compare it with previously published images and the inversion based on a global hybrid method. In addi-tion, we also test the influence of Earth’s spherical curvature on the tomographic results. Our results demonstrate that the teleseismic full-waveform inversion based on a single plane-wave incidence can reveal complex lithospheric structures similar to those imaged using a global hybrid method and is reliable for practical tomography for small regions with an aperture of a few hundred kilometers. However, neglecting the Earth’s spherical curvature and secondary phases leads to errors on the recovered amplitudes of velocity anomalies (e.g., about 2.8% difference for density and VS, and 4.2% for VP on average). These errors can be reduced by adopting a spherical mesh and injecting multiple plane waves in the frequency–wavenumber-based hybrid method. The proposed plane-wave teleseismic full-waveform inversion is promising for mapping subwavelength-scale seismic structures using high-frequency teleseismic body waves ( > 1 Hz) including coda waves recorded at large N seismic arrays. Ministry of Education (MOE) SciNet is funded by the Canada Foundation for Innovation; the Government of Ontario; Ontario Research Fund— Research Excellence; and the University of Toronto. K. W. (after January 2020) and Y. Y. are supported by the Australian Research Council Discovery Grants DP190102940. K. W. (before January 2020), X. S. (before July 2019), and Q. L. are supported by the Natural Sciences and Engineering Research Council (NSERC) Discovery Grant 487237. P. T. is supported by Singapore Ministry of Education (MOE) AcRF Tier-1 Grant 04MNP000559C230.

CsPbX3nanocrystals have been employed in various optoelectronic applications, such as light-emitting diodes and solar cells. Nevertheless, widespread application of CsPbX3nanocrystals has been largely restricted by their poor aqueous stability. Despite the tremendous efforts focused on encapsulating the CsPbX3nanocrystals, it is still very challenging to achieve CsPbX3nanocrystals with good aqueous stability. This work describes the preparation and encapsulation methods for CsPbBr3/SiO2/mPEG-DSPE nanocrystals that can be readily dispersed in water and biological buffers. To the best of our knowledge, this is the first work that reports multiphoton emissions from CsPbBr3/SiO2/mPEG-DSPE nanocrystals in water. The protection afforded by the silica shell and phospholipid micelles enables the CsPbBr3/SiO2/mPEG-DSPE nanocrystals in aqueous solution to exhibit enhanced long-term stability and better shielding against ultrasonication treatment and continuous light irradiation than bare CsPbBr3nanocrystals. The toxicity of the CsPbBr3/SiO2/mPEG-DSPE nanocrystals has been evaluated in various cell lines. Subsequently, the encapsulated nanocrystals were used for targeted single and multiphoton imaging of cancer cells. This work not only describes the preparation of water-stable CsPbBr3nanocrystals but also paves the way for their applications in multiphoton bioimaging applications. Ministry of Education (MOE) Nanyang Technological University National Research Foundation (NRF) Submitted/Accepted version This research was supported by Nanyang Technological University under its start-up grant (M4080514); the Ministry of Education under its AcRF Tier 2 grants (MOE2017-T2-2-002 and MOE2019-T2-1-006); and the National Research Foundation (NRF) Singapore under its NRF Investigatorship (NRF-NRFI-2018-04).

The tetraruthenium tetrahydrido carbonyl cluster Ru4(µ-H)4(CO)12 (1) reacts with diphenylvinylphosphine under thermal activation to give the substitution products Ru4(µ-H)4(CO)12−n(κ1-Ph2PCH=CH2)n, (2) (n = 3 (a); 4 (b)). Both 2a and 2b have been completely characterized, including by single-crystal X-ray diffraction analysis. Each of the diphenylvinylphosphine ligands in 2a and 2b is terminally bound, via the phosphorus atom, to a different ruthenium metal center, while the hydride positions in the Ru4(µ-H)4 cores retain the D2d symmetry of the parent cluster 1. Clusters 2a and 2b were able to retain their structural integrity at elevated temperatures. Graphic Abstract: Thermolysis of Ru4(μ-H)4(CO)12 (1) in cyclohexane with diphenylvinylphosphine afforded the tri- and tetra-substituted derivatives Ru4(μ-H)4(CO)9(κ1-Ph2PCH=CH2)3 (2a) and Ru4(μ-H)4(CO)8(κ1-Ph2PCH=CH2)4 (2b). For both substituted clusters, the diphenylvinylphosphine ligands are bound terminally to the tetraruthenium core via the phosphorus atoms while the hydride positions retain the D2d symmetry of the parent cluster 1.[Figure not available: see fulltext.] Ministry of Education (MOE) Nanyang Technological University This work was supported by Hwa Chong Institution as well as Nanyang Technological University and the Ministry of Education with a research Grant (No. M4011158).

Strong light-matter interactions involved with photons and quasiparticles are fundamentally interesting to access the wealthy many-body physics in quantum mechanics. The emerging two-dimensional (2D) semiconductors with large exciton binding energies and strong quantum confinement allow to investigate exciton-photon coupling at elevated temperatures. Here we report room-temperature formation of Bragg polaritons in monolayer semiconductor on a dielectric mirror through the exciton-Bragg photon coupling. With the negative detuning energy of ∼ 30 meV, angle-resolved reflection signals reveal anti-crossing behaviors of lower and upper polariton branches at ±18° together with the Rabi splitting of 10 meV. Meanwhile, the strengthened photoluminescence appears in the lower polariton branch right below the anti-crossing angles, indicating the presence of the characteristic bottleneck effect caused by the slowing exciton-polariton energy relaxation towards the band minimum. The extracted coupling strength is between the ones of weak and distinct strong coupling regimes, where the eigenenergy splitting induced by the moderate coupling is resolvable but not large enough to fully separate two polaritonic components. Our work develops a simplified strategy to generate exciton-polaritons in 2D semiconductors and can be further extended to probe the intriguing bosonic characteristics of these quasiparticles, such as Bose-Einstein condensation, polariton lasing and superfluidity, directly at the material surfaces.[Figure not available: see fulltext.] Ministry of Education (MOE) National Research Foundation (NRF) Submitted/Accepted version We thank the support of the Ministry of Education of Singapore (MOE 2019-T2-1-044), Singapore National Research Foundation under the Competitive Research Programs (No. NRF-CRP-21- 2018-0007), the Fundamental Research Funds for the Central Universities of China, National Natural Science Foundation of China (Nos. 61904151 and 51173081), Natural Science Foundation of Shaanxi (No. 2020JM-108), Joint Research Funds of Department of Science & Technology of Shaanxi Province and Northwestern Polytechnical University (No. 2020GXLHZ-020), Ministry of Education of China (IRT1148), and Zhejiang Provincial Natural Science Foundation of China (No. LGG19F040003).

Molecular activatable probes with near-infrared (NIR) fluorescence play a critical role in in vivo imaging of biomarkers for drug screening and disease diagnosis. With structural diversity and high fluorescence quantum yields, hemicyanine dyes have emerged as a versatile scaffold for the construction of activatable optical probes. This Review presents a survey of hemicyanine-based NIR activatable probes (HNAPs) for in vivo imaging and early diagnosis of diseases. The molecular design principles of HNAPs towards activatable optical signaling against various biomarkers are discussed with a focus on their broad applications in the detection of diseases including inflammation, acute organ failure, skin diseases, intestinal diseases, and cancer. This progress not only proves the unique value of HNAPs in preclinical research but also highlights their high translational potential in clinical diagnosis. Ministry of Education (MOE) K.P. thanks Singapore Ministry of Education, Academic Research Fund Tier 1 (2019-T1-002-045, RG125/19, RT05/20), Academic Research Fund Tier 2 (MOE2018-T2-2-042), and A*STAR SERC AME Programmatic Fund (SERCA18A8b0059) for the financial support.

Quasi-complementary sequence sets (QCSSs) play an important role in multi-carrier code-division multiple-access (MC-CDMA) systems. They can support more users than perfect complementary sequence sets in MC-CDMA systems. It is desirable to design QCSSs with good parameters that are a trade-off of large set size, small periodic maximum magnitude correlation and small alphabet size. The main results are to construct new infinite families of QCSSs that all have small alphabet size and asymptotically optimal periodic maximum magnitude correlation. In this paper, we propose three new constructions of QCSSs using additive characters over finite fields. Notably, these QCSSs have new parameters and small alphabet sizes. Using the properties of characters and character sums, we determine their maximum periodic correlation magnitudes and prove that these QCSSs are asymptotically optimal with respect to the lower bound. Nanyang Technological University Accepted version The work of Gaojun Luo was supported by NTU Research under Grant 04INS000047C230GRT01. The work of Xiwang Cao was supported by the National Natural Science Foundation of China under Grant 11771007 and Grant 61572027. The work of Minjia Shi was supported in part by the National Natural Science Foundation of China under Grant 12071001and Grant 61672036, in part by the Excellent Youth Foundation of Natural Science Foundation of Anhui Province under Grant 1808085J20, and in part by the Academic Fund for Outstanding Talents in Universities under Grant gxbjZD03. The work of Tor Helleseth was supported by the Research Council of Norway under Grant 247742//O70 and Grant 311646/O70.

The authors acknowledge the financial support from TUBITAK (115F297, 117E713, and 119N343). H. V.D. gratefully acknowledges support from TUBA. In this work, we systematically studied the shape- and size-controlled monodisperse synthesis of iron oxide nanocrystals (IONCs) for their use as building blocks in the formation of mesocrystals. For this aim, on understanding the influence of the oleic acid concentration, iron-oleate concentration, and heating rate on the synthesis of robust and reproducible IONCs with desired sizes and shapes, we synthesized highly monodisperse similar to 11 nm sized nanocubes and nanospheres. Magnetic measurements of both cubic and spherical IONCs revealed the presence of mixed paramagnetic and superparamagnetic phases in these nanocrystals. Moreover, we observed that the magnetic moments of the nanocubes are more substantial compared to their spherical counterparts. We then demonstrated a simple magnetic-field-assisted assembly of nanocubes into three-dimensional (3D) cuboid mesocrystals while nanospheres did not form any mesocrystals. These findings indicate that small cubic nanocrystals hold great promise as potential building blocks of 3D magnetic hierarchical structures with their superior magnetic properties and mesocrystal assembly capability, which may have high relevance in various fields ranging from high-density data storage to biomedical applications. Turkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) 115F297 117E713 119N343

A new type of chiral oxidants are developed and successfully applied in the asymmetric beta-hydroxylation of enals under the catalysis of an inexpensive achiral NHC catalyst. This type of chiral oxidants can be easily prepared from the low-cost starting materials of substituted benzoic acids and chiral prolinols through simple dehydrative amidation reactions Agency for Science, Technology and Research (A*STAR) Ministry of Education (MOE) National Research Foundation (NRF) Published version We acknowledge financial support from the National Natural Science Foundation of China (Nos. 21772029, 21801051, 21961006), The 10 Talent Plan (Shicengci) of Guizhou Province (No. [2016]5649), the Guizhou Province Returned Oversea Student Science and Technology Activity Program [No. (2014)-2], the Science and Technology Department of Guizhou Province (Nos. [2018]2802, [2019]1020, Qiankehejichu-ZK[2021]Key033), the Program of Introducing Talents of Discipline to Universities of China (111 Program, No. D20023) at Guizhou University, Frontiers Science Center for Asymmetric Synthesis and Medicinal Molecules, Department of Education, Guizhou Province [Qianjiaohe KY No. (2020)004], the Guizhou Province First-Class Disciplines Project [(Yiliu Xueke Jianshe Xiangmu)-GNYL(2017)008], Guizhou University of Traditional Chinese Medicine, and Guizhou University (China). Singapore National Research Foundation under its NRF Investigatorship (No. NRF-NRFI2016-06), the Ministry of Education, Singapore, under its MOE AcRF Tier 1 Award (Nos. RG108/16, RG5/19, RG1/18), MOE AcRF Tier 3 Award (No. MOE2018-T3-1-003), the Agency for Science, Technology and Research (A*STAR) under its A*STAR AME IRG Award (Nos. A1783c0008, A1783c0010), GSK-EDB Trust Fund, Nanyang Research Award Grant, Nanyang Technological University.

This work proposes an effective electrode length model and reveals for the first time the relationship between this model and the mesa shape effect. On the basis of this model, we demonstrate high-performance triangular miniaturized-LEDs (mini-LEDs) and benchmark to the conventional square, and circular shapes of the same mesa area. Here, we systematically study the impact of shaping in mini-LEDs both theoretically and experimentally, which is fundamentally different than that of the conventional regular-sized LEDs. We find that, at the current level of 200 mA, the triangular mini-LEDs deliver an enhancement of 36.4% in the optical output power and a decrease of 9.6% for the forward voltage compared to the commonly used square ones, and also an enhancement of 24.6% in the optical output power and a decrease of 14.3% for the forward voltage compared to the circular ones. The superior optical performance is proved to result from longer effective n-electrode length in the case of the triangular mini-LEDs, which suppresses the self-heating effect and thus well preserves the internal quantum efficiency, whereas the light extraction efficiency and the heat dissipation for the triangular shape are not significantly increased for such small mesa sizes, unlike conventional broad-area LEDs. Meanwhile, the reduced voltage is revealed to stem from the decreased n-GaN resistance. Different than conventional LEDs, these findings therefore indicate that the effective n-electrode length matters substantially for the miniaturized-LEDs. Agency for Science, Technology and Research (A*STAR) National Research Foundation (NRF) This work is supported by the Singapore National Research Foundation under Grant No. NRF-CRP-6-2010-2 and the Singapore Agency for Science, Technology and Research (A*STAR) SERC Pharos Program under Grant No. 1527300025. H.V.D also gratefully acknowledges TUBA.

In the heterobiaryl cross-coupling reaction between aryl halides (Ar-X) and N-methylpyrrole (N-MP) catalyzed by rhodamine 6G (Rh6G+) under irradiation with visible light, a highly active and long-lived (millisecond time range) rhodamine 6G radical (Rh6G•) is formed upon electron transfer from N,N-diisopropylethylamine (DIPEA) to Rh6G+. In this study, we utilized steady-state and time-resolved spectroscopy techniques to demonstrate the existence of another electron-transfer process occurring from the relatively electron-rich N-MP to photoexcited Rh6G+ that was neglected in the previous reports. In this case, the radical Rh6G• formed is short-lived and undergoes rapid recombination (nanosecond time-range), rendering it ineffective in reducing Ar-X to aryl radicals Ar• that can subsequently be trapped by N-MP. This is further demonstrated via two model reactions involving 4'-bromoacetophenone and 1,3,5-tribromobenzene with insignificant product yields after visible-light irradiation in the absence of DIPEA. The unproductive quenching of photoexcited Rh6G+ by N-MP leads to a lower concentration of photocatalyst available for competitive charge transfer with DIPEA and hence decreases the efficiency of the cross-coupling reaction. Agency for Science, Technology and Research (A*STAR) We acknowledge financial support from the Pharma Innovation Programme Singapore PIPS (A*STAR, SERC A19B3a0014).

In this paper, a family of new entanglement-assisted quantum error-correcting codes (EAQECCs) is constructed from constacyclic codes with length $$n=\frac{q^2+1}{a}$$ by giving a new method to select defining sets, where $$a=m^2+1$$ , $$m>2$$ is even and q is an odd prime power with $$a\mid (q\pm m)$$ . It is worth pointing out that those EAQECCs are entanglement-assisted quantum maximum distance separable (EAQMDS) codes when $$d\le \frac{n+2}{2}$$ . All of them are new in the sense that their parameters are not covered by the previously known ones. Moreover, they have minimum distance larger than $$q+1$$ . Compared with the codes with the same length listed in Table 1, our codes have larger minimum distance.

The accurate detection of related biomarkers at early stage is crucial in diagnosis and therapy of cancer. Small molecule fluorescence probes stand out acting as efficient tools to detect biomolecules, especially biomacromolecules. Herein, a new probe that features excimer formation has been designed to detect cancer-related biomarker alkaline phosphatase(ALP). The probe shows high sensitivity to ALP with a low limit detection of 0.13 U/L and high selectivity with resistance to the interference in the complex physiological system. Furthermore, this probe presents good biocompatibility with negligible cytotoxicity and displays remarkable cell imaging functions, which allows for its application in biosystems. Theoretical simulation validates the high affinity of the probe with ALP and depicts the details of the interaction modes, which provides the possible mechanisms underlying the efficient detection of the probe in atomic level. The study of synthesis, properties and applications of the activatable emissive excimers not only enriches the tools to detect ALP, but also provides a new strategy to comprehend the pathogenic mechanism of enzyme-related diseases. Ministry of Education (MOE) Nanyang Technological University This work was supported by the National Natural Science Foundation of China(Nos.21904105, 22074120), the Fund of Nanyang Technological University, Singapore(No.NTU-SUG: M4081627.120) and the Singapore Ministry of Education, Academic Research Fund Tier 1(Nos.2019-T1-002-045, 2018-T1-001-173) and Academic Research Fund Tier 2(No.MOE2018-T2-2-042).

The implementation of high fidelity two-qubit gates is a bottleneck in the progress towards universal quantum computation in semiconductor quantum dot qubits. We study capacitive coupling between two triple quantum dot spin qubits encoded in the $S = 1/2$, $S_z = -1/2$ decoherence-free subspace -- the exchange-only (EO) spin qubits. We report exact gate sequences for CPHASE and CNOT gates, and demonstrate theoretically, the existence of multiple two-qubit sweet spots (2QSS) in the parameter space of capacitively coupled EO qubits. Gate operations have the advantage of being all-electrical, but charge noise that couple to electrical parameters of the qubits cause decoherence. Assuming noise with a 1/f spectrum, two-qubit gate fidelities and times are calculated, which provide useful information on the noise threshold necessary for fault-tolerance. We study two-qubit gates at single and multiple parameter 2QSS. In particular, for two existing EO implementations -- the resonant exchange (RX) and the always-on exchange-only (AEON) qubits -- we compare two-qubit gate fidelities and times at positions in parameter space where the 2QSS are simultaneously single-qubit sweet spots (1QSS) for the RX and AEON. These results provide a potential route to the realization of high fidelity quantum computation., Main text (16 pages, 6 figures). Supplementary material (24 pages, 6 figures)

Because of the importance of large-scale metal-organic framework (MOF) production and processing, the development of practical solutions to obtain commercially relevant MOF-based products is essential. Herein, we demonstrate a feasible pathway to construct functional zeolitic imidazolate framework-8 (ZIF-8)-coated fabric composite from commercially available precursors, through a scalable synthetic protocol to produce a large quantity of nanoscale ZIF-8, followed by a facile mean to drop-cast the powdered nanoparticles onto the fabric substrate. The ZIF-8/fabric composite shows enhanced organic dye adsorption capability and superior antibacterial property. This simple yet effective preparation process might be readily adopted for the large-scale production of useful MOF-based composite materials. Ministry of Education (MOE) Nanyang Technological University National Research Foundation (NRF) This research is supported by the Singapore National Research Foundation Investigatorship (Grant NRF-NRFI2018-03) and the Ministry of Education Singapore under the Academic Research Funds (Grants RT12/19 and MOE-MOET2EP10120-0003). W.L.T. is thankful for a Nanyang President’s Graduate Scholarship supporting his doctoral study.

The ability to rationally design and predictably construct crystalline solids has been the hallmark of crystal engineering research. To date, numerous examples of multicomponent crystals comprising organic molecules have been reported. However, the crystal engineering of cocrystals comprising both organic and inorganic chemical units is still poorly understood and mostly unexplored. Here, we report a new diverse set of higher‐order cocrystals (HOCs) based on the structurally versatile—yet largely unexplored—phosph(V/V)azane heterosynthon building block. The novel ternary and quaternary cocrystals reported are held together by synergistic and orthogonal intermolecular interactions. Notably, the HOCs can be readily obtained either via sequential or one‐pot mechanochemical methods. Computational modelling methods reveal that the HOCs are thermodynamically driven to form and that their mechanical properties strongly depend on the composition and intermolecular forces in the crystal, offering untapped potential for optimizing material properties., Mechanosynthesis gives ternary and quaternary hybrid organic‐inorganic cocrystals held together via synergistic intermolecular interactions. Notably, higher‐order ternary and quaternary cocrystals can be readily obtained either via serial synthetic routes from the individual components or via one‐pot approaches.

Enantioenriched phosphine azoles were synthesized in high yields via palladium-catalyzed asymmetric hydrophosphination with excellent yields and enantioselectivities under mild reaction conditions. One of the phosphine azoles was methylated and complexed to palladium(II) cleanly to give a chiral phosphine-NHC palladium(II) complex with excellent overall conversion. Ministry of Education (MOE) Submitted/Accepted version This research is supported by the Ministry of Education, Singapore, under its Academic Research Fund Tier 1 (2019- T1-001-094).

An organic photoredox-catalyzed dehydroxylative trifluoromethylation of allylic alcohols was developed in an environmentally benign manner. In this reaction, the readily available CF3SO2Na was selected as the trifluoromethylation reagent. The in situ generated byproduct SO2 was reutilized to activate C-OH bond, which enabled this dehydroxylative trifluoromethylation to be performed conveniently. A variety of multifunctionalized CF3-allylic compounds were obtained in high yields and excellent stereoselectivity. We gratefully acknowledge financial support from the National Natural Science Foundation of China (21702108), the Natural Science Foundation of Jiangsu Province, China (BK20160977), and the Six Talent Peaks Project in Jiangsu Province (YY-033).

The increasing occurrence of steroidal hormone micropollutant in the aquatic environment and their associated consequences have caused serious environmental concerns globally. Adsorptive removal of hormonal pollutants using polymeric membranes has been suggested but information on their performance in various environmental conditions is lacking. In this study, we examined the effect of salinity on the performance of polyethersulfone (PES) membrane to remove synthetic hormone 17α-ethinyl estradiol (EE2) from water. Our results show that an increase of salinity from 0 to 3% results in higher retention of EE2 onto PES membrane from 79.3 to 98.7%. The experimental results fit the Freundlich isotherm model better as compared to the Langmuir model. The Freundlich parameters n and Kf yielded the highest values at 3% salinity. The molecular simulation results suggest that a high salinity increases the binding energy between EE2 and PES membranes, promoting the PES-EE2 interaction through π–π interaction, hydrogen bonding and hydrophobic interaction. This study provides valuable information for improving design of specialised treatment facilities (in farming, pharmaceutical industries, etc.) to allow better removal of EE2 and other low-polar organic contaminants from water via a membrane-based sorption-elution method, and we recommend the inclusion of salinity as a factor in modelling the adsorption capacity of membranes to prevent the oversaturation of membrane and minimise the release of contaminants into the environment.

The reaction of the bis(thiophosphinoyl) geminal dianion [C(PPh2S)2]2- with B2Br4(SMe2)2 in toluene afforded the diboron-carbene complex [(SPh2P)2CB]2 (2). The lability of the boron-carbene bond was found in the reaction of the sterically hindered thiophosphinoyl iminophosphoranyl geminal dianion [C(PPh2NAr)(PPh2S)]2- (Ar = 2,6-iPr2C6H3) with B2Br4(SMe2)2 in toluene to form the diboron-carbene complex 4, where one boron center bonds with two methanediides, leading to an allyl anionic-like C═B←C2- electronic structure, while another boron center is stabilized by two imino substituents. Complex 4 underwent rearrangement via a 1,2-methanediide shift in toluene at 60 °C to give the diboron-carbene complex [(SPh2P)(ArNPh2P)CB]2 (5). Ministry of Education (MOE) This work was supported by the Ministry of Education Singapore, AcRF Tier 1 (RG121/17) (C.-W.S.). M.-C.Y. and M.-D.S. are grateful to the Ministry of Science and Technology of Taiwan for financial support.

Pyridinium (the protonated form of pyridine) and related compounds have been proposed to be promising homogenous electrocatalysts in the electrochemical reduction of CO2 to methanol due to the low overpotential required to achieve faradaic yields of about 20 %, although the percentage yields vary dramatically between different research groups. In this study, experimental conditions were varied during the electrolysis of CO2 at a platinum electrode in the presence of pyridinium to determine the reasons for the discrepancies in the yields of methanol reported between different research groups. Two other vitamin-based and environmentally friendly nitrogen-containing heterocyclic compounds (nicotinamide and nicotinic acid) which have structural similarities to the promising but toxic pyridine homogeneous electrocatalyst, were also investigated as alternative electrocatalysts for the reduction of CO2 in aqueous acidic media. Cyclic voltammetry studies suggest that nicotinamide and nicotinic acid (forms of vitamin B3) follow a similar reaction mechanism as pyridine in the reduction of CO2. Relatively low faradaic yields of methanol were obtained during controlled potential electrolysis experiments for all the electrocatalysts (0.4–1.9 %) which can be attributed to the low solubility of CO2 along with the competing hydrogen evolution reaction. It was found that adventitious sources of methanol were responsible for greatly inflating the apparent yields of methanol unless scrupulous care was taken in controlling the experimental conditions. The problem with background methanol is particularly difficult to control due to the electrochemical reactions typically generating products in the parts per million range, considerably lower than normal synthetic reactions. Ministry of Education (MOE) National Research Foundation (NRF) The authors are grateful to the National Research Foundation (NRF) Singapore under its Campus for Research Excellence and Technological Enterprise (CREATE) program and the Singapore Government MOE Academic Research Fund Tier 1 Grant (RG3/19) for funding.

The hypothetical Weyl particles in high-energy physics have been discovered in three-dimensional crystals as collective quasiparticle excitations near two-fold degenerate Weyl points. Such momentum-space Weyl particles carry quantized chiral charges, which can be measured by counting the number of Fermi arcs emanating from the corresponding Weyl points. It is known that merging unit-charged Weyl particles can create new ones with more charges. However, only very recently has it been realised that there is an upper limit - the maximal charge number that a two-fold Weyl point can host is four - achievable only in crystals without spin-orbit coupling. Here, we report the experimental realisation of such a maximally charged Weyl point in a three-dimensional photonic crystal. The four charges support quadruple-helicoid Fermi arcs, forming an unprecedented topology of two non-contractible loops in the surface Brillouin zone. The helicoid Fermi arcs also exhibit the long-pursued type-II van Hove singularities that can reside at arbitrary momenta. This discovery reveals a type of maximally charged Weyl particles beyond conventional topological particles in crystals., Comment: 17 pages, 4 figures

The minimum time required for a quantum system to evolve to a distinguishable state is set by the quantum speed limit, and consequently influences the change of quantum correlations and other physical properties. Here we study the time required to maximally entangle two principal systems interacting either directly or via a mediating ancillary system, under the same energy constraints. The direct interactions are proved to provide the fastest way to entangle the principal systems, but it turns out that there exist mediated dynamics that are just as fast. We show that this can only happen if the mediator is initially correlated with the principal systems. These correlations can be fully classical and can remain classical during the entangling process. The final message is that correlations save energy: one has to supply extra energy if maximal entanglement across the principal systems is to be obtained as fast as with an initially correlated mediator., 8 pages, 3 figures

The poor stability of the zinc-metal anode is a main bottleneck for practical application of aqueous zinc-ion batteries. Herein, a series of molecular sieves with various channel sizes are investigated as an electrolyte host to regulate the ionic environment of Zn2+ on the surface of the zinc anode and to realize separator-free batteries. Based on the ZSM-5 molecular sieve, a solid-liquid mixed electrolyte membrane is constructed to uniformize the transport of zinc ions and foster dendrite-free Zn deposition. Side reactions can also be suppressed through tailoring the solvation sheath and restraining the activity of water molecules in electrolyte. A V2 O5 ||ZSM-5||Zn full cell shows significantly enhanced performance compared to cells using glass fiber separator. Specifically, it exhibits a high specific capacity of 300 mAh g-1 , and a capacity retention of 98.67% after 1000 cycles and 82.67% after 3000 cycles at 1 A g-1 . It is attested that zeolites (ZSM-5, H-β, and Bate) with channel sizes of 5-7 Å result in best cycle stability. Given the low cost and recyclability of the ZSM and its potent function, this work may further lower the cost and boost the industrial application of AZIBs. Ministry of Education (MOE) Submitted/Accepted version This work was supported by the National Natural Science Foundation of China (No. 22172103, 21773009). H.J.F. acknowledges financial support from the Singapore Ministry of Education by Academic Research Fund Tier 2 (MOE-T2EP50121-0006).

Flexural oscillations of free-standing films, nano-membranes and nano-wires are attracting growing attention for their importance to the thermal, electrical and mechanical properties of 2D materials. Here we report on the observation of short-timescale ballistic motion in the flexural mode of a nano-membrane cantilever, driven by thermal fluctuation of flexural phonons, including measurements of ballistic velocities and displacements performed with sub-atomic resolution, using a new free electron edge-scattering technique. Within intervals, Comment: 7 pages, 4 figures

Conformational isomerization can be guided by weak interactions such as chalcogen bonding (ChB) interactions. Here we report a catalytic strategy for asymmetric access to chiral sulfoxides by employing conformational isomerization and chalcogen bonding interactions. The reaction involves a sulfoxide bearing two aldehyde moieties as the substrate that, according to structural analysis and DFT calculations, exists as a racemic mixture due to the presence of an intramolecular chalcogen bond. This chalcogen bond formed between aldehyde (oxygen atom) and sulfoxide (sulfur atom), induces a conformational locking effect, thus making the symmetric sulfoxide as a racemate. In the presence of N-heterocyclic carbene (NHC) as catalyst, the aldehyde moiety activated by the chalcogen bond selectively reacts with an alcohol to afford the corresponding chiral sulfoxide products with excellent optical purities. This reaction involves a dynamic kinetic resolution (DKR) process enabled by conformational locking and facile isomerization by chalcogen bonding interactions. Ministry of Education (MOE) National Research Foundation (NRF) Published version We acknowledge funding supports from National Natural Science Foundation of China (21732002, 22061007, P. C. Z; 22071036, Y. R. C); Frontiers Science Center for Asymmetric Synthesis and Medicinal Molecules, Department of Education, Guizhou Province [Qianjiaohe KY number (2020)004, Y. R. C]; The 10 Talent Plan (Shicengci) of Guizhou Province ([2016]5649, Y. R. C); Qiankehejichu-ZK[2022]zhongdian024, P. C. Z); Science and Technology Department of Guizhou Province ([2018]2802, [2019]1020, Y. R. C); Program of Introducing Talents of Discipline to Universities of China (111 Program, D20023, Y. R. C) at Guizhou University. Singapore National Research Foundation under its NRF Investigatorship (NRF–NRFI2016–06, Y. R. C) and Competitive Research Program (NRF–CRP22–2019–0002, Y. R. C); Ministry of Education, Singapore, under its MOE AcRF Tier 1 Award (RG7/20, RG5/19, Y. R. C), MOE AcRF Tier 2 (MOE2019–T2–2–117, Y. R. C), and MOE AcRF Tier 3 Award (MOE2018–T3–1–003, Y. R. C), Nanyang Technological University.

Thermo-gelling polymers have been envisioned as promising smart biomaterials but limited to their weak mechanical and thermodynamic stabilities. Here we propose a new thermo-gelling vitrimer, which remains at a liquid state because of the addition of protector molecules preventing the crosslinking, and with increasing temperature, an entropy driven crosslinking occurs to induce the sol-gel transition. Moreover, we find that the activation barrier in the metathesis reaction of vitrimers plays an important role, and experimentally one can use catalysts to tune the activation barrier to drive the vitrimer to form an equilibrium gel at high temperature, which is not subject to any thermodynamic instability. We formulate a mean field theory to describe the entropy driven crosslinking of the vitrimer, which agrees quantitatively with computer simulations, and paves the way for design and fabrication of novel vitrimers for biomedical applications., Accepted in JACS Au

Organic semiconductors have shown great potential as efficient bioelectronic materials. Specifically, photovoltaic polymers such as the workhorse poly(thiophene) derivatives, when stimulated with visible light, can depolarize neurons and generate action potentials, an effect that has been also employed for rescuing vision in blind rats. In this context, however, the coupling of such materials with optically resonant structures to enhance those photodriven biological effects is still in its infancy. Here, we employ the optical coupling between a nanostructured metasurface and poly(3-hexylthiophene) (P3HT) to improve the bioelectronic effects occurring upon photostimulation at the abiotic-biotic interface. In particular, we designed a spectrally tuned aluminum metasurface that can resonate with P3HT, hence augmenting the effective field experienced by the polymer. In turn, this leads to an 8-fold increase in invoked inward current in cells. This enhanced activation strategy could be useful to increase the effectiveness of P3HT-based prosthetic implants for degenerative retinal disorders. Ministry of Education (MOE) Published version This work was supported by the Singapore Ministry of Education Academic Research Fund Tier 1 (2018-T1-002- 040).

Quantum tomography is one of the major challenges of large-scale quantum information research due to the exponential time complexity. In this work, we develop and apply a Bayesian state estimation method to experimentally demonstrate quantum overlapping tomography [Phys. Rev. Lett. \textbf{124}, 100401 (2020)], a scheme intent on characterizing critical information of a many-body quantum system in logarithmic time complexity. By comparing the measurement results of full state tomography and overlapping tomography, we show that overlapping tomography gives accurate information of the system with much fewer state measurements than full state tomography., Accepted in Phys. Rev. Lett., main-text 6 pages, 4 figures, and Supplements 20 pages, 37 figures

For the classification of topological phases of matter, an important consideration is whether a system is spinless or spinful, as these two classes have distinct symmetry algebra that gives rise to fundamentally different topological phases. However, only recently has it been realized theoretically that in the presence of gauge symmetry, the algebraic structure of symmetries can be projectively represented, which possibly enables the switch between spinless and spinful topological phases. Here, we report the first experimental demonstration of this idea by realizing spinful topological phases in "spinless" acoustic crystals with projective space-time inversion symmetry. In particular, we realize a DIII-class one-dimensional topologically gapped phase characterized by a 2Z winding number, which features Kramers degenerate bands and Kramers pair of topological boundary modes. Our work thus overcomes a fundamental constraint on topological phases by spin classes., 6 pages, 4 figures

As one of leading technologies in detecting relativistic particles, Cherenkov radiation plays an essential role in modern high-energy and particle physics. However, the limited photon yield in transparent dielectrics makes efficient Cherenkov radiation only possible with high-energy particles (at least several MeV). This restriction hinders applications of Cherenkov radiation in free-electron light source, bio-imaging, medical therapy, etc. Broadband enhancement of Cherenkov radiation is highly desired for all these applications, but still widely acknowledged as a scientific challenge. To this end, we report a general approach to enhance the photon yield of Cherenkov radiation using dispersionless plasmons. Broadband dispersionless plasmons can be realized by exploiting either the acoustic nature of terahertz plasmons in a graphene-based heterostructure or the nonlocal property of optical plasmons in a metallodielectric structure. When coupled to moving electrons, such dispersionless plasmons give rise to a radiation enhancement rate more than two orders of magnitude (as compared with conventional Cherenkov radiation) over an ultrabroad frequency band. Moreover, since the phase velocity of dispersionless plasmons can be made as small as the Fermi velocity, giant radiation enhancements can be readily induced by ultralow-energy free electrons (e.g. with a kinetic energy down to 3 electronvolts), without resorting to relativistic particles. Ministry of Education (MOE) National Research Foundation (NRF) Published version The work at Zhejiang University was sponsored in part by the National Natural Science Foundation of China (NNSFC) (Nos. 61625502, 11961141010, 61975176, and 62175212), the Top-Notch Young Talents Program of China, the National Natural Science Fund for Excellent Young Scientists Fund Program (Overseas) of China, Zhejiang University Global Partnership Fund, and the Fundamental Research Funds for the Central Universities (No. 2021FZZX001- 19). The work at Nanyang Technological University was sponsored in part by Singapore Ministry of Education (Nos. MOE2018-T2-2-189 (S), MOE2018-T2-1-022 (S), and MOE2016-T3-1-006), A*Star Advanced Manufacturing and Engineering Individual Research Grant (No. A20E5c0095) and Programmatic Funds (No. A18A7b0058), National Research Foundation Singapore Competitive Research Program (Nos. NRF-CRP22-2019- 0006 and NRF-CRP23-2019-0007).

Topological phases of matter have remained an active area of research in the last few decades. Periodic driving is known to be a powerful tool for enriching such exotic phases, which leads to various phenomena with no static analogs. One such phenomenon is the emergence of the elusive $pi/2$ modes, i.e., a type of topological boundary state pinned at a quarter of the driving frequency. The latter may lead to the formation of Floquet parafermions in the presence of interaction, which is known to support more computational power than Majorana particles. In this work, we experimentally verify the signature of $\pi/2$ modes in an acoustic waveguide array, which is designed to simulate a square-root periodically driven Su-Schrieffer-Heeger model. This is accomplished by confirming the $4T$-periodicity ($T$ being the driving period) profile of an initial-boundary excitation, which we also show theoretically to be the smoking gun evidence of $\pi/2$ modes. Our findings are expected to motivate further studies of $\pi/2$ modes in quantum systems for potential technological applications., Comment: 6 pages, 3 figure. Comments are welcome

The strong nonlinearities of exciton-polariton condensates in lattices make them suitable candidates for neuromorphic computing and physical simula- tions of complex problems. So far, all room temperature polariton condensate lattices have been achieved by nanoimprinting microcavities, which by nature lacks the crucial tunability required for realistic reconfigurable simulators. Here, we report the observation of a quantised oscillating nonlinear quantum fluid in 1D and 2D potentials in an organic microcavity at room temperature, achieved by an on-the-fly fully tuneable optical approach. Remarkably, the condensate is delocalised from the excitation region by macroscopic dis- tances, leading both to longer coherence and a threshold one order of mag- nitude lower than that with a conventional Gaussian excitation profile. We observe different mode selection behaviour compared to inorganic materials, which highlights the anomalous scaling of blueshift with pump intensity and the presence of sizeable energy-relaxation mechanisms. Our work is a major step towards a fully tuneable polariton simulator at room temperature. Ministry of Education (MOE) Published version M.W., G.A.T., and I.D.W.S. acknowledge financial support from the Engineering and Physical Sciences Research Council (EPSRC) programme grant Hybrid Polaritonics (EP/M025330/1), and from the Scottish Funding Council. W.V. and T.L. were supported by the Ministry of Education (Singapore) Tier 2 grant MOE2019-T2-004. H.O. acknowledges EPSRC through a grant (EP/S014403/1). K.O. acknowledges EPSRC for PhD studentship support through a grant (EP/L015110/1).

Stack engineering, an atomic-scale metamaterial strategy, enables the design of optical and electronic properties in van der Waals heterostructure devices. Here we reveal the optoelectronic effects of stacking-induced strong coupling between atomic motion and interlayer excitons in WSe2/MoSe2 heterojunction photodiodes. To do so, we introduce the photocurrent spectroscopy of a stack-engineered photodiode as a sensitive technique for probing interlayer excitons, enabling access to vibronic states typically found only in molecule-like systems. The vibronic states in our stack are manifest as a palisade of pronounced periodic sidebands in the photocurrent spectrum in frequency windows close to the interlayer exciton resonances and can be shifted "on demand" through the application of a perpendicular electric field via a source-drain bias voltage. The observation of multiple well-resolved sidebands as well as their ability to be shifted by applied voltages vividly demonstrates the emergence of interlayer exciton vibronic structure in a stack-engineered optoelectronic device. Ministry of Education (MOE) Published version This work was supported by the Army Research Office Electronics Division Award no. W911NF2110260 (N.M.G., V.A., and T.B.A.), the Presidential Early Career Award for Scientists and Engineers (PECASE) through the Air Force Office of Scientific Research (award no. FA9550-20-1- 0097; N.M.G. and T.B.A.), through support from the National Science Foundation Division of Materials Research CAREER Award (no. 1651247; N.M.G. and F.B.), and through the United States Department of the Navy Historically Black Colleges, Universities and Minority Serving Institutions (HBCU/MI) award no. N00014-19-1-2574 (N.M.G. and F.B.). T.B.A. acknowledges support from the Fellowships and Internships in Extremely Large Data Sets (FIELDS) program, a NASA MUREP Institutional Research Opportunity (MIRO) program (grant no. NNX15AP99A). R.v.G. acknowledges institutional support from the Royal Netherlands Academy of Arts and Sciences (KNAW) and the Canadian Institute of Solar Energy Research (CEA). J.C.W.S. acknowledges support from the Singapore Ministry of Education under its MOE AcRF Tier 3 Award (MOE2018-T3-1-002). M.S.R is grateful for the support of the European Research Council (ERC) under the European Union Horizon 2020 Research and Innovation Programme (grant agreement no. 678862) and the Villum Foundation. R.K.L. and S.S. acknowledge support from the NSF (EFRI-1433395). This work used the Extreme Science and Engineering Discovery Environment (XSEDE), which is supported by National Science Foundation grant no. ACI-1053575 and allocation ID TG-DMR130081.

In living and engineered systems of active particles, self-propulsion induces an unjamming transition from a solid to a fluid phase and phase separation between a gas and a liquidlike phase. We demonstrate an interplay between these two nonequilibrium transitions in systems of persistent active particles. The coexistence and jamming lines in the activity-density plane meet at the jamming transition point in the limit of hard particles or zero activity. This interplay induces an anomalous dynamic in the liquid phase and hysteresis at the active jamming transition. Ministry of Education (MOE) Published version We acknowledge support from the Singapore Ministry of Education through the Singapore Academic Research Fund, Grants No. RG86/19 and No. RG56/21.

The non-Hermitian skin effect (NHSE) is a phenomenon whereby certain non-Hermitian lattice Hamiltonians host an extensive number of eigenmodes condensed to the boundary, called skin modes. Although the NHSE has mostly been studied in the classical or single-particle regime, it can also manifest in interacting quantum systems with boson number nonconserving processes. We show that lattices of coupled nonlinear resonators can function as reciprocal quantum amplifiers. A one-dimensional chain exhibiting the NHSE can perform strong photon amplification aided by the skin modes, which scales exponentially with the chain length and outperforms alternative lattice configurations lacking the NHSE. Moreover, two-dimensional lattices can perform directional photon amplification between different lattice corners, due to the two-dimensional NHSE. These quantum amplifiers are based on experimentally feasible lattice configurations with uniform parametric driving schemes. Ministry of Education (MOE) National Research Foundation (NRF) Published version This work was supported by the Singapore MOE Academic Research Fund Tier 3 Grant No. MOE2016-T3-1-006 and Tier 1 Grant No. RG148/20, and by the National Research Foundation Competitive Research Programs No. NRF-CRP23-2019-0005 and No. NRF-CRP23-2019-0007.

Topological data analysis has recently found applications in various areas of science, such as computer vision and understanding of protein folding. However, applications of topological data analysis to natural language processing remain under-researched. This study applies topological data analysis to a particular natural language processing task: fake news detection. We have found that deep learning models are more accurate in this task than topological data analysis. However, assembling a deep learning model with topological data analysis significantly improves the model’s accuracy if the available training set is very small. Published version

The enhancement of the photoluminescence of quantum dots induced by an optical nanoantenna has been studied considerably, but there is still significant interest in optimizing and miniaturizing such structures, especially when accompanied by an experimental demonstration. Most of the realizations use plasmonic platforms, and some also use all-dielectric nanoantennas, but hybrid dielectric-plasmonic (subwavelength) nanostructures have been very little explored. In this paper, we propose and demonstrate single subwavelength hybrid dielectric-plasmonic optical nanoantennas coupled to localized quantum dot emitters that constitute efficient and bright unidirectional photon sources under optical pumping. To achieve this, we devised a silicon nanoring sitting on a gold mirror with a 10 nm gap in-between, where an assembly of colloidal quantum dots is embedded. Such a structure supports both (radiative) antenna mode and (nonradiative) gap mode resonances, which we exploit for the dual purpose of out-coupling the light emitted by the quantum dots into the far-field with out-of-plane directivity, and for enhancing the excitation of the dots by the optical pump. Moreover, almost independent control of the resonance spectral positions can be achieved by simple tuning of geometrical parameters such as the ring inner and outer diameters, allowing us to conveniently adjust these resonances with respect to the quantum dots emission and absorption wavelengths. Using the proposed architecture, we obtain experimentally average fluorescence enhancement factors up to $654\times$ folds mainly due to high radiative efficiencies, and associated with a directional emission of the photoluminescence into a cone of $\pm 17\degree$ in the direction normal to the sample plane. We believe the solution presented here to be viable and relevant for the next generation of light-emitting devices., 39 pages, 4 figures

We demonstrate, via numerical simulations, that the relaxation dynamics of supercooled liquids correlates well with a plastic length scale measuring a particle's response to impulsive localized perturbations and weakly to measures of local elasticity. We find that the particle averaged plastic length scale vanishes linearly in temperature and controls the super-Arrhenius temperature dependence of the relaxation time. Furthermore, we show that the plastic length scale of individual particles correlates with their typical displacement at the relaxation time. In contrast, the local elastic response only correlates with the dynamics on the vibrational time scale., Supplementary Material included

This paper studies stochastic linear-quadratic control with a time-inconsistent objective and worst-case drift disturbance. We allow the agent to introduce disturbances to reflect her uncertainty about the drift coefficient of the controlled state process. We adopt a two-step equilibrium control approach to characterize the robust time-consistent controls, which can preserve the order of preference. Under a general framework allowing random parameters, we derive a sufficient condition for equilibrium controls using the forward-backward stochastic differential equation approach. We also provide analytical solutions to mean-variance portfolio problems for various settings. Our empirical studies confirm the improvement in portfolio’s performance in terms of out-of-sample Sharpe ratio by incorporating with robustness. Ministry of Education (MOE) Bingyan Han is supported by UIC Start-up Research Fund (Reference No: R72021109). Chi Seng Pun gratefully acknowledges the Ministry of Education (MOE), AcRF Tier 2 Grant (Reference No: MOE2017-T2-1-044) for the funding of this research. Hoi Ying Wong acknowledges the support from the Research Grants Council of Hong Kong via GRF 14303915.

Nanosystem-mediated tumor radiosensitization strategy combining the features of X-ray with infinite penetration depth and high atomic number elements shows considerable application potential in clinical cancer therapy. However, it is difficult to achieve satisfactory anticancer efficacy using clinical radiotherapy for the majority of solid tumors due to the restrictions brought about by the tumor hypoxia, insufficient DNA damage, and rapid DNA repair during and after treatment. Inspired by the complementary advantages of nitric oxide (NO) and X-ray-induced photodynamic therapy, we herein report a two-dimensional nanoplatform by the integration of the NO donor-modified LiYF4:Ce scintillator and graphitic carbon nitride nanosheets for on-demand generation of highly cytotoxic peroxynitrite (ONOO–). By simply adjusting the Ce3+ doping content, the obtained nanoscintillator can realize high radioluminescence, activating photosensitive materials to simultaneously generate NO and superoxide radical for the formation of ONOO– in the tumor. Obtained ONOO– effectively amplifies therapeutic efficacy of radiotherapy by directly inducing mitochondrial and DNA damage, overcoming hypoxia-associated radiation resistance. The level of glutamine synthetase (GS) is downregulated by ONOO–, and the inhibition of GS delays DNA damage repair, further enhancing radiosensitivity. This work establishes a combinatorial strategy of ONOO– to overcome the major limitations of radiotherapy and provides insightful guidance to clinical radiotherapy. Agency for Science, Technology and Research (A*STAR) Submitted/Accepted version Financial support from the National Natural Science Foundation of China (51972075, 51972076, and 51772059), the Natural Science Foundation of Shandong Province (ZR2019ZD29), the Natural Science Foundation of Heilongjiang Province (YQ2019E014), the Postdoctoral Scientific Research Developmental Fund (LBH-Q18034), and the Ph.D. Student Research and Innovation Fund of the Fundamental Research Funds for the Central Universities (3072020GIP1016) are greatly acknowledged. This research is also supported by the Singapore Agency for Science, Technology and Research (A*STAR) AME IRG grant (A20E5c0081).

We consider a photonic lattice of nonlinear lossy resonators subjected to a coherent drive, where the system remembers its topological phase. Initially, the system is topologically trivial. After the application of an additional coherent pulse, the intensity is increased, which modifies the couplings in the system and then induce a topological phase transition. However, when the effect of the pulse dies out, the system does not go back to the trivial phase. Instead, it remembers the topological phase and maintains its topology acquired during the pulse application. The pulse can be used as a switch to trigger amplification of the topological modes. We further show that the amplification takes place at a different frequency as well as at a different position from those of the pulse, indicating frequency conversion and intensity transfer. Our work can be useful in triggering the different functionalities of active topological photonic devices., Close to the published version

Photocorrosion of cuprous oxide (Cu2O) has notably limited its application as an efficient photocatalyst. We report a facile approach to visualize in situ formation of copper and oxygen vacancies on the Cu2O surface under ambient condition. By imaging photoexcited single Cu2O particles, the resultant photoluminescence generated at Cu2O surface enable effective localization of copper and oxygen vacancies. Single particle photoluminescence imaging showed substantial heterogeneity in the rate of defect formation at different facets with the truncated corners achieving the fastest initial rate of photooxidation before subsequently changing to the face and edge sites as the photocorrosion proceeds. The generation of copper or oxygen vacancy is proportional to the photoexcitation power, while pH-dependent studies rationalized alkaline conditions for the formation of copper vacancy. Reaction in an electron-hole scavenger system showed that photooxidation and photoreduction will simultaneously occur, yet heterogeneously on the surface of Cu2O, with rate of copper vacancy formation being fastest. Agency for Science, Technology and Research (A*STAR) Ministry of Education (MOE) Submitted/Accepted version This work was supported by the School of Physical and Mathematical Sciences at Nanyang Technological University, Singapore Ministry of Education, Academic Research Fund (No. RG4/19(S) and RG10/20), and the Singapore Agency for Science, Technology and Research (A*STAR) AME YIRG grant (No. A2084c0065).

Real-time optical imaging of immune cells can contribute to understanding their pathophysiological roles, which still remains challenging. Current sensitive chemiluminophores have issues of short half-lives and low brightness, limiting their ability for in vivo longitudinal monitoring of immunological processes. To tackle these issues, we report benzoazole-phenoxyl-dioxetane (BAPD)-based chemiluminophores with intramolecular hydrogen bonding for in vivo imaging of neutrophils. Compared with the classical counterpart, chemiluminescence half-lives and brightness of BAPDs in the aqueous solution are increased by ∼ 33- and 8.2-fold, respectively. Based on the BAPD scaffold, a neutrophil elastase-responsive chemiluminescent probe is developed for real-time imaging of neutrophils in peritonitis and psoriasis mouse models. Our study provides an intramolecular hydrogen bonding molecular design for improving the performance of chemiluminophores in advanced imaging applications. Agency for Science, Technology and Research (A*STAR) Ministry of Education (MOE) K.P. thanks Singapore Ministry of Education, Academic Research Fund Tier 1 (2019-T1-002-045, RG125/19; RT05/20), Academic Research Fund Tier 2 (MOE2018-T2-2-042; MOE-T2EP30220-0010), and A*STAR SERC AME Programmatic Fund (SERC A18A8b0059) for the financial support.

Let $\R$ be a real closed field, $ {\mathcal Q} \subset \R[Y_1,...,Y_\ell,X_1,...,X_k], $ with $ \deg_{Y}(Q) \leq 2, \deg_{X}(Q) \leq d, Q \in {\mathcal Q}, #({\mathcal Q})=m,$ and $ {\mathcal P} \subset \R[X_1,...,X_k] $ with $\deg_{X}(P) \leq d, P \in {\mathcal P}, #({\mathcal P})=s$, and $S \subset \R^{\ell+k}$ a semi-algebraic set defined by a Boolean formula without negations, with atoms $P=0, P \geq 0, P \leq 0, P \in {\mathcal P} \cup {\mathcal Q}$. We prove that the sum of the Betti numbers of $S$ is bounded by \[ \ell^2 (O(s+\ell+m)\ell d)^{k+2m}. \] This is a common generalization of previous results on bounding the Betti numbers of closed semi-algebraic sets defined by polynomials of degree $d$ and 2, respectively. We also describe an algorithm for computing the Euler-Poincar\'e characteristic of such sets, generalizing similar algorithms known before. The complexity of the algorithm is bounded by $(\ell s m d)^{O(m(m+k))}$., Comment: 23 pages, 1 figure. Shortened revised version to appear in the J. Eur. Math. Soc

This research was supported in part by the National Research Foundation, Prime Minister's Office, Singapore, under its Investigatorship Program (NRF-NRFI2016-08) and the Singapore Agency for Science, Technology and Research (A*STAR) SERC Pharos Program under Grant 152 73 00025. The authors also acknowledge financial support from TUBITAK through 115E679, 115F297, and 117E713 programs. The authors thank Mr. Mustafa Guler and Mr. Ovunc Karakurt for their assistance in TEM imaging, Dr. Gokce Celik for her help on the ellipsometric measurements, Mr. Semih Bozkurt for his support on the AFM characterization, and Mr. Bilge Yagci for his assistance in optical characterization. O.E. acknowledges TUBITAK for financial support through the BIDEB-2211 program. H.V.D. gratefully acknowledges TUBA. Here, the first account of self-resonant fully colloidal mu-lasers made from colloidal quantum well (CQW) solution is reported. A deep patterning technique is developed to fabricate well-defined high aspect-ratio on-chip CQW resonators made of grating waveguides and in-plane reflectors. The fabricated waveguide-coupled laser, enabling tight optical confinement, assures in-plane lasing. CQWs of the patterned layers are closed-packed with sharp edges and residual-free lifted-off surfaces. Additionally, the method is successfully applied to various nanoparticles including colloidal quantum dots and metal nanoparticles. It is observed that the patterning process does not affect the nanocrystals (NCs) immobilized in the attained patterns and the different physical and chemical properties of the NCs remain pristine. Thanks to the deep patterning capability of the proposed method, patterns of NCs with subwavelength lateral feature sizes and micron-scale heights can possibly be fabricated in high aspect ratios. Agency for Science Technology & Research (ASTAR) 152 73 00025 Turkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) 115E679 115F297 117E713

Azolium cumulenolates are a special type of intermediates in N-heterocyclic carbene catalysis. They contain elongated linear structures with three contiguous C=C bonds and sterically unhindered α-carbon. These structure features make it difficult to develop enantioselective reactions for these intermediates. Here we disclose the first carbene-catalyzed highly enantioselective addition reactions of azolium cumulenolates. The reaction starts with alkynals as the precursors for azolium cumulenolate intermediates that undergo enantioselective addition to activated ketones. From the same set of substrates, both allene and spirooxindole products can be obtained with high yields and excellent enantioselectivities. The allene moieties in our optically enriched products carry rich reactivities and can be transformed to diverse molecules. The spirooxindole scaffolds in our products are important structural motifs in natural products and medicines. Ministry of Education (MOE) National Research Foundation (NRF) Accepted version

Current-induced magnetization switching by spin-orbit torque generated in heavy metals offers an enticing realm for energy-efficient memory and logic devices. The spin Hall efficiency is a key parameter in describing the generation of spin current. Recent findings have reported enhancement of spin Hall efficiency by mechanical strain, but its origin remains elusive. Here, we demonstrate a 45% increase in spin Hall efficiency in the platinum/cobalt (Pt/Co) bilayer, of which 78% of the enhancement was preserved even after the strain was removed. Spin transparency and X-ray magnetic circular dichroism revealed that the enhancement was attributed to a bulk effect in the Pt layer. This was further confirmed by the linear relationship between the spin Hall efficiency and resistivity, which indicates an increase in skew-scattering. These findings shed light on the origin of enhancement and are promising in shaping future utilization of mechanical strain for energy-efficient devices. Agency for Science, Technology and Research (A*STAR) Economic Development Board (EDB) National Research Foundation (NRF) Submitted/Accepted version This work is supported by an Industry-IHL Partnership Program (NRF2015-IIP001-001) and an EDB-IPP (RCA − 17/284) grant. This work is also supported by the RIE2020 ASTAR AME IAF-ICP grant (No. I1801E0030). W.Z. and P.K.J.W. acknowledge financial support by the Fundamental Research Funds for the Central Universities.

The reaction of amidinatosilylene LSi(:)Cl [L = PhC(NtBu)2] with N-heterocyclic carbene IAr [:C{N(Ar)CH}2, where Ar = 2,6-iPr2C6H3] and NaOTf in tetrahydrofuran (THF) facilely afforded a silicon(II) cation [LSi(:)-aIAr]+OTf- (1+OTf-), where IAr isomerizes to abnormal N-heterocyclic carbene aIAr, coordinating to the silicon(II) center. Its Ge homologue, [LGe(:)-aIAr]+OTf- (2+OTf-), was also accessed via the same protocol. For the formation of 1+, we propose that an in situ-generated Si(II) cation [LSi(:)]+ under the treatment of LSi(:)Cl with NaOTf may isomerize IAr in THF. In contrast, the replacement of IAr with cyclic alkyl(amino) carbene (cAAC) furnished a cAAC-silanyl radical ion [LSi(H)-cAAC]•+(LiOTf2)- [3•+(LiOTf2)-], which may undergo an abstraction of the H radical from THF. All of the products were characterized by nuclear magnetic resonance spectroscopy, electron paramagnetic resonance, and X-ray crystallography, and their bonding scenarios were investigated by density functional theory calculations. These studies provide new perspective on carbene-silicon chemistry. This work was supported by the National Natural Science Foundation of China (Grant 21801055) and the Zhejiang Provincial Natural Science Foundation (Grant LY20B020009). D.K. acknowledges funding from the SERB-CRG (CRG/2019/001572) scheme.

The realization of electrically tunable plasmonic resonances in the ultraviolet (UV) to visible spectral band is particularly important for active nanophotonic device applications. However, the plasmonic resonances in the UV to visible wavelength range cannot be tuned due to the lack of tunable plasmonic materials. Here, we experimentally demonstrate tunable plasmonic resonances at visible wavelengths using a chalcogenide semiconductor alloy such as antimony telluride (Sb2Te3), by switching the structural phase of Sb2Te3 from amorphous to crystalline. We demonstrate the excitation of a propagating surface plasmon with a high plasmonic figure of merit in both amorphous and crystalline phases of Sb2Te3 thin films. We show polarization-dependent and -independent plasmonic resonances by fabricating one and two-dimensional periodic nanostructures in Sb2Te3 thin films, respectively. Moreover, we demonstrate electrically tunable plasmonic resonances using a microheater integrated with the Sb2Te3/Si device. The developed electrically tunable Sb2Te3-based plasmonic devices could find applications in the development of active color filters. Agency for Science, Technology and Research (A*STAR) Accepted version The authors (K.V.S. and R.S.) acknowledge the funding support from Advanced Manufacturing and Engineering (AME) Programmatic (Grant No. A18A5b0056) by Agency for Science, Technology and Research.

Molecular weight distribution of polymer, termed dispersity (Đ), is a fundamental parameter that determines polymer properties. Sodium azide (NaN3) functions as a catalyst in organocatalyzed living radical polymerization when the reaction medium is non-polar. In contrast, NaN3 can act as a nucleophile when the reaction medium is polar. In this paper, we report an efficient approach to dispersity control by exploiting the dual functions of NaN3 under the varied solvent polarity. Simultaneous polymerization and chain-end substitution allowed us to tune the Đ values of various polymethacrylates and poly(butyl acrylate). Notably, the Đ value could be tuned to a wide range approximately from 1.2 to 2.0 for polymethacrylates and to 3.8 for poly(butyl acrylate). This approach afforded polymer brushes on surfaces with tailored Đ values. An interesting finding was that the polymer brushes exhibited a unique interaction with external molecules, depending on the Đ value. National Research Foundation (NRF) Accepted version This work was supported by National Research Foundation (NRF) Investigatorship in Singapore (NRF-NRFI05-2019-0001).