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Highlights Two-dimensional mono- and few-layered Ti 3 CNT x MXene nanosheets with extremely high nitrogen content were synthesized. Better performance for hydrogen evolution reaction (HER) than Pt/C catalyst in acidic, neutral and alkaline solutions. Exceptional performance of HER in both acidic and alkaline solutions. A large current density (> 500 mA cm −2 ) has been achieved for HER. Transition metal carbides, known as MXenes, particularly Ti 3 C 2 T x , have been extensively explored as promising materials for electrochemical reactions. However, transition metal carbonitride MXenes with high nitrogen content for electrochemical reactions are rarely reported. In this work, transition metal carbonitride MXenes incorporated with Pt-based electrocatalysts, ranging from single atoms to sub-nanometer dimensions, are explored for hydrogen evolution reaction (HER). The fabricated Pt clusters/MXene catalyst exhibits superior HER performance compared to the single-atom-incorporated MXene and commercial Pt/C catalyst in both acidic and alkaline electrolytes. The optimized sample shows low overpotentials of 28, 65, and 154 mV at a current densities of 10, 100, and 500 mA cm −2 , a small Tafel slope of 29 mV dec −1 , a high mass activity of 1203 mA mg Pt −1 and an excellent turnover frequency of 6.1 s −1 in the acidic electrolyte. Density functional theory calculations indicate that this high performance can be attributed to the enhanced active sites, increased surface functional groups, faster charge transfer dynamics, and stronger electronic interaction between Pt and MXene, resulting in optimized hydrogen absorption/desorption toward better HER. This work demonstrates that MXenes with a high content of nitrogen may be promising candidates for various catalytic reactions by incorporating single atoms or clusters.

Electronic correlations play important roles in driving exotic phenomena in condensed matter physics. They determine low-energy properties through high-energy bands well-beyond optics. Great effort has been made to understand low-energy excitations such as low-energy excitons in transition metal dichalcogenides (TMDCs), however their high-energy bands and interlayer correlation remain mysteries. Herewith, by measuring temperature- and polarization-dependent complex dielectric and loss functions of bulk molybdenum disulphide from near-infrared to soft X-ray, supported with theoretical calculations, we discover unconventional soft X-ray correlated-plasmons with low-loss, and electronic transitions that reduce dimensionality and increase correlations, accompanied with significantly modified low-energy excitons. At room temperature, interlayer electronic correlations, together with the intralayer correlations in the c -axis, are surprisingly strong, yielding a three-dimensional-like system. Upon cooling, wide-range spectral-weight transfer occurs across a few tens of eV and in-plane p–d hybridizations become enhanced, revealing strong Coulomb correlations and electronic anisotropy, yielding a two-dimensional- like system. Our result shows the importance of strong electronic, interlayer and intralayer correlations in determining electronic structure and opens up applications of utilizing TMDCs on plasmonic nanolithrography. Electronic and interlayer correlations are expected to affect the electronic and optical properties of transition metal dichalcogenides. Here, by using spectroscopic ellipsometry in the broad energy range, the authors uncover new electronic transitions and correlated plasmons in bulk MoS 2 .

We present a novel x-ray lithography based micromanufacturing methodology that offers scalable manufacturing of high precision optical components. It is accomplished through simultaneous usage of multiple stencil masks made moveable with respect to one another through custom made micromotion stages. The range of spectral flux reaching the sample surface at the LiMiNT micro/nanomanufacturing facility of Singapore Synchrotron Light Source (SSLS) is about 2 keV to 10 keV, offering substantial photon energy to carry out deep x-ray lithography. In this energy range, x-rays penetrate through resist materials with only little scattering. The highly collimated rectangular beam architecture of the x-ray source enables a full 4″ wafer scale fabrication. Precise control of dose deposited offers determined chain scission in the polymer to required depth enabling 1800 discrete gray levels in a chip of area 20 mm 2 and with more than 2000 within our reach. Due to its parallel processing capability, our methodology serves as a promising candidate to fabricate micro/nano components of optical quality on a large scale to cater for industrial requirements. Usage of these fine components in analytical devices such as spectrometers and multispectral imagers transforms their architecture and shrinks their size to pocket dimension. It also reduces their complexity and increases affordability while also expanding their application areas. Consequently, equipment based on these devices is made available and affordable for consumers and businesses expanding the horizon of analytical applications. Mass manufacturing is especially vital when these devices are to be sold in large quantities especially as components for original equipment manufacturers (OEM), which has also been demonstrated through our work. Furthermore, we also substantially improve the quality of the micro-components fabricated, 3D architecture generated, throughput, capability and availability for industrial application. Manufacturing 1800 Gray levels or more through other competing techniques is either limited due to multiple process steps involved or due to unacceptably long time required owing to their pencil beam architecture. Our manufacturing technique presented here overcomes both these shortcomings in terms of the maximum number of gray levels that can be generated, and the time required to generate the same.

Inorganic perovskites have recently attracted much attention as promising new nanocrystalline materials that have interesting fundamental phenomena and great potential in several applications. Herein, we reveal unusual structural and electronic changes in nanocrystalline cesium lead bromide (CsPbBr 3 ) as a function of temperature using high-resolution spectroscopic ellipsometry, high-resolution transmission electron microscopy and terahertz spectroscopy measurements supported by first-principles calculations. New dual phases of crystalline and electronic structures are observed due to the nanocrystalline nature of the material. Interestingly, a change in the electronic structure occurs below 150 K, and the rate at which the nanocrystal transitions from the tetragonal to orthorhombic phase is found to be nonlinear with temperature. Our results show the importance of the charge and lattice interplay in determining the dual phases and fundamental properties of nanocrystalline materials. Nanocrystals: Split personalities bring solar benefits Findings that show nanoscale crystals can adopt multiple properties at low temperatures may aid production of inexpensive solar cells. Crystals such as cesium lead bromide (CsPbBr 3 ) are attractive for next-generation photovoltaics because they can be coated onto numerous types of surfaces. Thomas Whitcher and Andrivo Rusydi from the National University of Singapore and colleagues now report that CsPbBr 3 nanocrystals undergo unusual changes when taken to sub-zero conditions. Through spectroscopic ellipsometry supported with high-resolution electron microscopy and Terahertz spectroscopic measurements, the team identified two different structural arrangements of CsPbBr 3 coexisting at temperatures below −120 °C. By combining the microscopy data of the crystal’s complex refractive index, the researchers found evidence that the two structures also had distinct electrical properties. The new methodology could provide insights into problems that currently affect CsPbBr 3 solar cells, including poor resistance to environmental changes. We reveal unusual electronic and structural changes of nano-crystalline CsPbBr 3 at different temperatures. Using high-resolution spectroscopic ellipsometry, high-resolution transmission electron microscopy, terahertz spectroscopy and supported by first-principles calculations, we find that a new dual structural phase is observed due to an effect of the material’s nano-crystalline nature. We also develop a method of determining the phase transitions within the material through the identification of optical transitions within the electronic structure and the comparison of experimental data and theoretical models. Our result shows the importance of the interplay between charge and lattice in determining structural and electronic properties of nano-crystalline materials.

We report strong ferromagnetism of quasiparticle doped holes both within the ab- plane and along the c- axis of Cu-O planes in low-dimensional Au/ d- La 1.8 Ba 0.2 CuO 4 /LaAlO 3 (001) heterostructures ( d  = 4, 8 and 12 unit-cells) using resonant soft X-ray and magnetic scattering together with X-ray magnetic circular dichroism. Interestingly, ferromagnetism is stronger at a hole doped peak and at an upper Hubbard band of O with spin-polarization degree as high as 40%, revealing strong ferromagnetism of Mottness. For in- ab -plane spin-polarizations, the spin of doped holes in O2 p –Cu3 d –O2 p is a triplet state yielding strong ferromagnetism. For out-of- ab -plane spin-polarization, while the spins of doped holes in both O2 p –O2 p and Cu3 d –Cu3 d are triplet states, the spin of doped holes in Cu3 d –O2 p is a singlet state yielding ferrimagnetism. A ferromagnetic-(002) Bragg-peak of the doped holes is observed and enhanced as a function of d revealing strong ferromagnetism coupling between Cu-O layers along the c -axis. Long-range magnetic order of quasiparticle doped holes is important for understanding the physics of cuprate superconductors, albeit difficult to probe in experiments. Ong et al. observe ferromagnetism of quasiparticle doped holes in a cuprate heterostructure and discuss implications for cuprates in the ground state.

Monochromators for synchrotron radiation beamlines typically use perfect crystals for the hard X‐ray regime and gratings for soft X‐rays. There is an intermediate range, typically 1–3 keV (tender X‐rays), which common perfect crystals have difficulties covering and gratings have low efficiency, although some less common crystals with high d‐spacing could be suitable. To evaluate the suitability of these crystals for a particular beamline, it is useful to evaluate the crystals' performance using tools such as ray‐tracing. However, simulations for double‐crystal monochromators are only available for the most used crystals such as Si, Ge or diamond. Here, an upgrade of the SHADOW ray‐tracing code and complementary tools in the OASYS suite are presented to simulate high d‐spacing crystals with arbitrary, and sometimes complex, structures such as beryl, YB66, muscovite, etc. Isotropic and anisotropic temperature factors are also considered. The YB66 crystal with 1936 atomic sites in the unit cell is simulated, and its applicability for tender X‐ray monochromators is discussed in the context of new low‐emittance storage rings. A method is introduced for representation of arbitrary crystals, numerical calculation treatment and ray‐tracing simulation, and upgrading the tools in the OASYS suit; the upgraded tools are particularly helpful for very complicated crystals constituting charged atoms arranged in any crystalline structure and including isotropic or anisotropic temperature factors. The new open source software tools developed here are available for supporting accurate calculations in the design and optimization of new X‐ray monochromators.

Hybrid inorganic-organic perovskites have recently attracted much interest because of both rich fundamental sciences and potential applications such as the primary energy-harvesting material in solar cells. However, an understanding of electronic and optical properties, particularly the complex dielectric function, of these materials is still lacking. Here, we report on the electronic and optical properties of selective perovskites using temperature-dependent spectroscopic ellipsometry, x-ray absorption spectroscopy supported by first-principles calculations. Surprisingly, the perovskiteFA0.85Cs0.15PbI2.9Br0.1has a very high density of low-energy excitons that increases with increasing temperature even at room temperature, which is not seen in any other material. This is found to be due to the strong, unscreened electron-electron and partially screened electron-hole interactions, which then tightly connect low- and high-energy bands caused by doping.

Fingerprint evidence offers great value to criminal investigations since it is an internationally recognized and established means of human identification. With recent advances in modern technology, scientists have started analyzing not only the ridge patterns of fingerprints but also substances which can be found within them. The aim of this work was to determine whether Fourier transform infrared (FTIR) spectromicroscopy could be used to detect contamination in a fingerprint which was dusted with powder (a technique already recognized as an effective and reliable method for developing latent fingerprints) and subsequently lifted off with adhesive tape. Explosive materials (pentaerythritol tetranitrate, C-4, TNT) and noncontrolled substances (sugar, aspirin) were used to prepare contaminated fingerprints on various substrates. Freshly deposited fingermarks with powders which were lifted off with adhesive tapes (provided by Singapore Police Force) were analyzed using a Bruker Hyperion 2000 microscope at the ISMI beamline (Singapore Synchrotron Light Source) with an attenuated total reflection objective. FTIR spectroscopy is a nondestructive technique which requires almost no sample preparation. Further, the fingerprint under analysis remains in pristine condition, allowing subsequent analysis if necessary. All analyzed substances were successfully distinguished using their FTIR spectra in powdered and lifted fingerprints. This method has the potential to significantly impact forensic science by greatly enhancing the information that can be obtained from the study of fingerprints.