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The functionalization of inorganic surfaces by organic functional molecules is a viable and promising method towards the realization of novel classes of biosensing devices. The proper comprehension of the chemical properties of the interface, as well as of the number of active binding sites for bioreceptor molecules are characteristics that will determine the interaction of the sensor with the analyte, and thus its final efficiency. We present a new and reliable surface functionalization route based on supersonic molecular beam deposition (SuMBD) using 2,6-naphthalene dicarboxylic acid as a bi-functional molecular linker on the chemically inert silicon nitride surface to further allow for stable and homogeneous attachment of biomolecules. The kinetically activated binding of the molecular layer to silicon nitride and the growth as a function of deposition time was studied by X-ray photoelectron spectroscopy, and the properties of films with different thicknesses were investigated by optical and vibrational spectroscopies. After subsequent attachment of a biological probe, fluorescence analysis was used to estimate the molecular layer's surface density. The successful functionalization of silicon nitride surface via SuMBD and the detailed growth and interface analysis paves the way for reliably attaching bioreceptor molecules onto the silicon nitride surface.

X-ray-activated near-infrared luminescent nanoparticles are considered as new alternative optical probes due to being free of autofluorescence, while both their excitation and emission possess a high penetration efficacy in vivo . Herein, we report silicon carbide quantum dot sensitization of trivalent chromium-doped zinc gallate nanoparticles with enhanced near-infrared emission upon X-ray and UV-vis light excitation. We have found that a ZnGa 2 O 4 shell is formed around the SiC nanoparticles during seeded hydrothermal growth, and SiC increases the emission efficiency up to 1 order of magnitude due to band alignment that channels the excited electrons to the chromium ion., Competing Interests: The authors declare no competing financial interest., (© 2021 The Authors. Published by American Chemical Society.)

Two-dimensional transition metal dichalcogenides (TMDs) represent an ideal testbench for the search of materials by design, because their optoelectronic properties can be manipulated through surface engineering and molecular functionalization. However, the impact of molecules on intrinsic physical properties of TMDs, such as superconductivity, remains largely unexplored. In this work, the critical temperature ( T C ) of large-area NbSe 2 monolayers is manipulated, employing ultrathin molecular adlayers. Spectroscopic evidence indicates that aligned molecular dipoles within the self-assembled layers act as a fixed gate terminal, collectively generating a macroscopic electrostatic field on NbSe 2 . This results in an ∼55% increase and a 70% decrease in T C depending on the electric field polarity, which is controlled via molecular selection. The reported functionalization, which improves the air stability of NbSe 2 , is efficient, practical, up-scalable, and suited to functionalize large-area TMDs. Our results indicate the potential of hybrid 2D materials as a novel platform for tunable superconductivity.

WSe 2 is a layered ambipolar semiconductor enabling hole and electron transport, which renders it a suitable active component for logic circuitry. However, solid-state devices based on single- and bilayer WSe 2 typically exhibit unipolar transport and poor electrical performance when conventional SiO 2 dielectric and Au electrodes are used. Here, we show that silane-containing functional molecules form ordered monolayers on the top of the WSe 2 surface, thereby boosting its electrical performance in single- and bilayer field-effect transistors. In particular, by employing SiO 2 dielectric substrates and top Au electrodes, we measure unipolar mobility as high as μ h = 150 cm 2 V -1 s -1 and μ e = 17.9 cm 2 V -1 s -1 in WSe 2 single-layer devices when ad hoc molecular monolayers are chosen. Additionally, by asymmetric double-side functionalization with two different molecules, we provide opposite polarity to the top and bottom layer of bilayer WSe 2 , demonstrating nearly balanced ambipolarity at the bilayer limit. Our results indicate that the controlled functionalization of the two sides of the WSe 2 mono- and bilayer flakes with highly ordered molecular monolayers offers the possibility to simultaneously achieve energy level engineering and defect functionalization, representing a path toward deterministic control over charge transport in 2D materials.

Transition metal dichalcogenides, such as molybdenum disulfide (MoS 2 ), show peculiar chemical/physical properties that enable their use in applications ranging from micro- and nano-optoelectronics to surface catalysis, gas and light detection, and energy harvesting/production. One main limitation to fully harness the potential of MoS 2 is given by the lack of scalable and low environmental impact synthesis of MoS 2 films with high uniformity, hence setting a significant challenge for industrial applications. In this work, we develop a versatile and scalable sol-gel-derived MoS 2 film fabrication by spin coating deposition of an aqueous sol on different technologically relevant, flexible substrates with annealing at low temperatures (300 °C) and without the need of sulfurization and/or supply of hydrogen as compared to cutting-edge techniques. The electronic and physical properties of the MoS 2 thin films were extensively investigated by means of surface spectroscopy and structural characterization techniques. Spatially homogenous nanocrystalline 2H-MoS 2 thin films were obtained exhibiting high chemical purity and excellent electronic properties such as an energy band gap of 1.35 eV in agreement with the 2H phase of the MoS 2 , and a density of states that corresponds to the n-type character expected for high-quality 2H-MoS 2 . The potential use of sol-gel-grown MoS 2 as the candidate material for electronic applications was tested via electrical characterization and demonstrated via the reversible switching in resistivity typical for memristors with a measured ON-OFF ratio ≥10 2 . The obtained results highlight that the novel low-cost fabrication method has a great potential to promote the use of high-quality MoS 2 in technological and industrial-relevant scalable applications.

The original version of this article incorrectly listed an affiliation of Sara Bonacchi as 'Present address: Institut National de la Recherche Scientifique (INRS), EMT Center, Boulevard Lionel-Boulet, Varennes, QC, J3X 1S2, 1650, Canada', instead of the correct 'Present address: Department of Chemical Sciences - University of Padua - Via Francesco Marzolo 1 - 35131 Padova - Italy'. And an affiliation of Emanuele Orgiu was incorrectly listed as 'Present address: Department of Chemical Sciences, University of Padua, Via Francesco Marzolo 1, Padova, 35131, Italy', instead of the correct 'Present address: Institut National de la Recherche Scientifique (INRS), EMT Center, Boulevard Lionel-Boulet, Varennes, QC, J3X 1S2, 1650, Canada'. This has been corrected in both the PDF and HTML versions of the article.

In this work we propose a realistic model of nanometer-thick SiC/SiOx core/shell nanowires (NWs) using a combined first-principles and experimental approach. SiC/SiOx core/shell NWs were first synthesised by a low-cost carbothermal method and their chemical-physical experimental analysis was accomplished by recording X-ray absorption near-edge spectra. In particular, the K-edge absorption lineshapes of C, O, and Si are used to validate our computational model of the SiC/SiOx core/shell NW architectures, obtained by a multiscale approach, including molecular dynamics, tight-binding and density functional simulations. Moreover, we present ab initio calculations of the electronic structure of hydrogenated SiC and SiC/SiOx core/shell NWs, studying the modification induced by several different substitutional defects and impurities into both the surface and the interfacial region between the SiC core and the SiOx shell. We find that on the one hand the electron quantum confinement results in a broadening of the band gap, while hydroxyl surface terminations decrease it. This computational investigation shows that our model of SiC/SiOx core/shell NWs is capable to deliver an accurate interpretation of the recorded X-ray absorption near-edge spectra and proves to be a valuable tool towards the optimal design and application of these nanosystems in actual devices.

The unoccupied electronic structure of thick films of tetraphenylporphyrin and tetrakis(pentafluorophenyl)porphyrin Cu(ii) complexes (hereafter, CuTPP and CuTPP(F)) deposited on Au(111) has been studied by combining the outcomes of near-edge X-ray absorption fine structure (NEXAFS) spectroscopy with those of spin-unrestricted time-dependent density functional (TD-DFT) calculations carried out either within the scalar relativistic zeroth order regular approximation (ZORA) framework (C, N and F K-edges) or by using the Tamm-Dancoff approximation coupled to ZORA and including spin-orbit effects (Cu L2,3-edges). Similarly to the modelling of NEXAFS outcomes pertaining to other Cu(ii) complexes, the agreement between theory and experiment is more than satisfactory, thus confirming the open-shell TD-DFT to be a useful tool to look into NEXAFS results pertinent to Cu(ii) compounds. The combined effect of metalation and phenyl (Ph) fluorine decoration is found to favour an extensive mixing between (Ph)σ* and pristine porphyrin macrocyle (pmc) (pmc)π* virtual levels. The lowest lying excitation in the C and N K-edge spectra of both CuTPP and CuTPP(F) is associated with a ligand-to-metal-charge-transfer transition, unambiguously revealed in the (CuTPP)N K-edge spectral pattern. Moreover, the comparison with literature data pertaining to the modelling of the (Cu(II))L2,3 features in the phthalocyanine-Cu(ii) (CuPc) complex provided further insights into how metal-to-ligand-charge-transfer transitions associated with excitations from 2p(Cu(II)) AOs to low-lying, ligand-based π* MOs may contribute to the Cu(ii) L2,3-edge intensity and thus weaken its believed relationship with the Cu(ii)-ligand symmetry-restricted covalency. Despite the coordinative pocket of CuTPP/CuTPP(F) mirroring CuPc, the ligand-field strength exerted by the phthalocyanine ligand on the Cu(ii) centre is experimentally found and theoretically confirmed to be slightly stronger than that experienced by Cu in CuTPP and CuTPP(F). On the whole, the obtained results complement those published in the near past by the same group on the occupied and empty states of the H2TPP and H2TPP(F) free ligands as well as on the occupied states of both CuTPP and CuTPP(F), thus providing the final piece to get a thorough description of electronic perturbations associated with the metalation and the Ph halogen decoration of H2TPP.

A combination of ultraviolet and X-ray photoelectron spectroscopy, X-ray absorption spectroscopy, and first principle calculations was used to study the electronic structure at the interface between the strong molecular acceptor 1,3,4,5,7,8-hexafluorotetracyano-naphthoquinodimethane (F6TCNNQ) and a graphene layer supported on either a quartz or a copper substrate. We find evidence for fundamentally different charge redistribution mechanisms in the two ternary systems, as a consequence of the insulating versus metallic character of the substrates. While electron transfer occurs exclusively from graphene to F6TCNNQ on the quartz support (p-doping of graphene), the Cu substrate electron reservoir induces an additional electron density flow to graphene decorated with the acceptor monolayer. Remarkably, graphene on Cu is n-doped and remains n-doped upon F6TCNNQ deposition. On both substrates, the work function of graphene increases substantially with a F6TCNNQ monolayer atop, the effect being more pronounced (∼1.3 eV) on Cu compared to quartz (∼1.0 eV) because of the larger electrostatic potential drop associated with the long-distance graphene-mediated Cu-F6TCNNQ electron transfer. We thus provide a means to realize high work function surfaces for both p- and n-type doped graphene.

We used aromatic phosphonates with substituted phenyl rings with different molecular dipole moments to form self-assembled monolayers (SAMs) on the Zn-terminated ZnO(0001) surface in order to engineer the energy-level alignment at hybrid inorganic/organic semiconductor interfaces, with an oligophenylene as organic component. The work function of ZnO was tuned over a wide range of more than 1.7 eV by different SAMs. The difference in the morphology and polarity of the SAM-modified ZnO surfaces led to different oligophenylene orientation, which resulted in an orientation-dependent ionization energy that varied by 0.7 eV. The interplay of SAM-induced work function modification and oligophenylene orientation changes allowed tuning of the offsets between the molecular frontier energy levels and the semiconductor band edges over a wide range. Our results demonstrate the versatile use of appropriate SAMs to tune the energy levels of ZnO-based hybrid semiconductor heterojunctions, which is important to optimize its function, e.g., targeting either interfacial energy- or charge-transfer.

This article presents studies on the effect of Sr and TiB on the crystallization process, mechanical properties, hardness, and density index of the Al-Si alloy from the EN AC-46000 group, with a narrowed chemical composition, produced by die-casting and HPDC (high-pressure die casting) technology. The research used the Box–Wilson method to design the experiment and stepwise multiple regression. To identify the optimal amount of Sr and Ti in the analyzed alloy that would simultaneously guarantee the maximization of UTS, YS, Agt, and HBW and the minimization of the DI (density index), multi-criteria optimization was performed. The modifiers were added to the liquid alloy as AlSr10 and AlTi5B1 master alloys. It was found that for 0.02–0.04 wt.% Sr and 0.05–0.08 wt.% Ti in the die castings, the highest mechanical properties, such as UTS, YS, Agt, and HBW (treated as stimulants in the experiment), can be obtained simultaneously with the lowest alloy gasification identified by DI (treated as a destimulant in the experiment). It was also confirmed that the same amount of the above-mentioned elements in HPDC castings caused an increase in UTS by approx. 14%, YS by approx. 6%, A by approx. 47%, and HBW by approx. 13%, with a relatively small increase in DI by approx. 5% compared to the unmodified alloy. [ABSTRACT FROM AUTHOR]

This study investigates the impact of strontium (Sr) additions on the corrosion resistance of an LM6 (A413) aluminium alloy. By incorporating varying concentrations of Sr (0.01 wt.% and 0.05 wt.%), the morphological and corrosion behaviours of the alloy were analysed under different corrosive environments, including sulphuric acid, sodium hydroxide, and sodium chloride solutions. The results demonstrate that Sr modifications significantly enhance the alloy's corrosion resistance, with the most substantial improvement observed at 0.05 wt.% Sr. The analysis revealed that the weight loss of the alloy in sulphuric acid decreased by 2.5% with 0.05 wt.% Sr after 10 days of immersion, due to the formation of a stable passive oxide layer. In sodium hydroxide, however, the weight loss was reduced by 5% with 0.05 wt.% Sr after 10 days, indicating aggressive uniform corrosion. In the 3.5% sodium chloride solution, the corrosion rates remain relatively low, and the 0.05 wt.% Sr alloy showed a decrease in corrosion product formation over time, suggesting enhanced resistance. Detailed surface analyses, including 3D profiling and morphology assessments, revealed that Sr additions refine the eutectic silicon phase, transforming it from a coarse to a more desirable fibrous or lamellar structure, thus improving the alloy's overall performance. The innovative findings underscore the potential of Sr as an effective microstructural modifier for enhancing the durability and longevity of Al-Si alloys in corrosive environments. [ABSTRACT FROM AUTHOR]

The back contact of p-type semiconductors and metal electrodes have always been a difficulty in fabricating photovoltaics with high performance. The incompatibility of high HOMO with a metal work function may lead to Schottky contact at a back semiconductor–metal interface and lead to device inversion. Thus, the performance of the photovoltaic is restricted, especially for solution-processed CdTe NC solar cells. In our research, we proposed using Cu salts as a Cu source to dope CdTe NCs and improve the back contact interface. Enhanced performance in solution-processed NC solar cells is achieved by introducing an engineered Cu salt layer (CuCl2 and CuBr2). Exceptional performance is attained with the optimized CdTe NC doped with CuCl2, exhibiting a high short-circuit current of 20.20 mA cm−2, an open-circuit voltage of 0.58 V, and a fill factor of 53.74%, resulting in a power conversion efficiency of 6.3%. These results represent a significant improvement over the control group. Through detailed first principles studies and experimental verification, we demonstrate that the copper halide-doped CdTe NC thin film is promising to promote the carrier concentration of the CdTe NC and suppress carrier recombination by improving band alignment at the back contact interface. [ABSTRACT FROM AUTHOR]

Field-effect transistors (FETs) based on two-dimensional molybdenum disulfide (2D-MoS2) have great potential in electronic and optoelectronic applications, but the performances of these devices still face challenges such as scattering at the contact interface, which results in reduced mobility. In this work, we fabricated high-performance MoS2-FETs by inserting self-assembling monolayers (SAMs) between MoS2 and a SiO2 dielectric layer. The interface properties of MoS2/SiO2 were studied after the inductions of three different SAM structures including (perfluorophenyl)methyl phosphonic acid (PFPA), (4-aminobutyl) phosphonic acid (ABPA), and octadecylphosphonic acid (ODPA). The SiO2/ABPA/MoS2-FET exhibited significantly improved performances with the highest mobility of 528.7 cm2 V−1 s−1, which is 7.5 times that of SiO2/MoS2-FET, and an on/off ratio of ~106. Additionally, we investigated the effects of SAM molecular dipole vectors on device performances using density functional theory (DFT). Moreover, the first-principle calculations showed that ABPA SAMs reduced the frequencies of acoustic and optical phonons in the SiO2 dielectric layer, thereby suppressing the phonon scattering to the MoS2 channel and further improving the device's performance. This work provided a strategy for high-performance MoS2-FET fabrication by improving interface properties. [ABSTRACT FROM AUTHOR]

This study is aimed to investigate the effects of introducing dysprosium (Dy) into Zn-based hydroxyapatite (HAp) at various concentrations (0.45, 0.90, 1.35 and 1.80%). The structural and optical properties of pure and doped HAp were thoroughly examined through theoretical and empirical analyses, including X-ray diffraction, Raman spectroscopy and Fourier transform infrared (FTIR) studies. The results confirmed the successful incorporation of Dy into the HAp lattice without significantly affecting its thermal stability or stoichiometry. The introduction of Dy into Zn-based HAp led to notable alterations in several material parameters. The lattice parameters, crystallinity, lattice stress, strain and anisotropic energy density varied with different Dy concentrations. In comparison with undoped HAp, all Dy-doped Zn-based HAps exhibited reduced crystallite size values, indicating a change in the microstructure. Furthermore, the material density increased from 3.159 to 3.228 g cm−3 with Dy doping. The band gap (BG), an important parameter for optical applications, is consistently decreased from 4.6 to 3.9 eV as the Dy concentration increased. This decrease in BG suggests the potential for improved photocatalytic or optoelectronic properties in Dy-doped Zn-based HAp. Additionally, the linear absorption coefficient (LAC) increased, indicating enhanced light absorption. Overall, this study provides a comprehensive understanding of structural and optical modifications induced by Dy doping in Zn-based HAp. These findings contribute to the potential application of Dy-doped Zn-based HAp in various fields, including biomedicine, photocatalysis and optoelectronics. [ABSTRACT FROM AUTHOR]

Nb–Si-based alloys show great potential to surpass the widely used Ni-based superalloys. The element Sr is widely applied in aluminum and magnesium alloys, but reports about the effects of Sr on Nb–Si-based alloys are quite rare. So, Nb–Si-based alloys with nominal compositions of Nb–15Si–24Ti–4Cr–2Al–2Hf–0/0.05/0.15Sr (at%) were prepared by directional solidification and heat treatment. The microstructural characterization and room temperature fracture toughness of Nb–Si-based alloy were systematically investigated. Results show that all these alloys consist of Nb5Si3 phase embedded within Nb solid solution (Nbss) matrix. The Nb5Si3 phase becomes refined and more discontinuous after adding minor Sr. As for the fracture toughness, 0.05 at% and 0.15 at% Sr additions do not cause significant change. The discontinuous and refining mechanism of Sr element was studied, and the analysis of toughness decreasing with Sr addition reveals that the size of Nbss phase plays a crucial role in determining the fracture toughness. [ABSTRACT FROM AUTHOR]

The effects of chromium (Cr) addition ranging 0.1–0.3 wt.% on the microstructure and mechanical properties of Al–7Si–4Cu–0.25Mg (wt.%) alloy have been investigated. The cast Cr-free alloy consisted of α-Al, eutectic Si, Q-Al5Mg8Cu2Si6 and θ-Al2Cu phases. Doping of Cr resulted in the appearance of a polyhedron-shaped α-Al13Cr4Si4 phase with a cubic structure. The Al13Cr4Si4 particles were found to embed with Al2Cu blocks and bring about size reduction for the Al2Cu blocks. The area fraction of Al13Cr4Si4 monotonously increased with Cr content. After T6 treatment, the Al2Cu blocks almost fully dissolved and transformed to θ'-Al2Cu precipitates in the Cr-containing alloys. TEM observation revealed relatively large-sized θ' precipitates attached to Al13Cr4Si4 dispersoids. The Cr-containing alloys showed impressive mechanical properties, with the peak strength up to 452 MPa at room temperature. The ductility exhibited an increasing trend with Cr content, but the strength dropped dramatically when the Cr content reached 0.3 wt.%. It is suggested that the strength contribution from the Al13Cr4Si4 phase is limited, especially at an elevated temperature. [ABSTRACT FROM AUTHOR]

Adjusting the hole transport layer (HTL) to optimize its interface with perovskite is crucial for minimizing interface recombination, enhancing carrier extraction, and achieving efficient and stable inverted perovskite solar cells (PSCs). However, as a commonly used HTL, the self-assemble layer (SAM) of [2-(3,6-dimethoxy-9H-carbazol-9-yl)ethyl] phosphonic acid (MeO-2PACz) tends to form clusters and micelles during the deposition process, leading to inadequate coverage of the ITO substrate. Here, a Co-SAM strategy is employed by incorporating 4-mercaptobenzoic acid (SBA) and 4-trifluoromethyl benzoic acid (TBA) as additives into MeO-2PACz to fabricate a Co-SAM-based HTL. The introduced additive can interact with MeO-2PACz, facilitating cluster dispersion and thereby enabling better deposition on ITO for improved HTL coverage. Moreover, Co-SAM exhibits superior energy level alignment with perovskite to enhance interfacial contact and improve carrier extraction efficiency as well as promote growth of bottom perovskite grains. As a result, an impressive increase of the power conversion efficiency (PCE) from 21.34% to 23.31% is achieved in the inverted device based on the Co-SAM HTL of MeO-2PACz+TBA while maintaining ≈90% of its initial efficiency under continuous operation at 1-sun., (© 2024 Wiley‐VCH GmbH.)

This paper investigates the microstructure and mechanical behavior of modified strain-induced melt activation (M-SIMA) processed Al-7Si-0.05Sr alloy. The M-SIMA process involves multiple warm rolling at 150 °C (below recrystallization temperature) to reduce its thickness by 60% to its original dimension, followed by semi-solid isothermal treatment at 585 °C for 30 min. The microstructure was characterized by optical microscopy, scanning electron microscopy, energy dispersive spectroscopy, atomic force microscopy, and transmission electron microscopy. During the early stage of the experiment, Sr-containing as-cast alloy showed a better hardness value than that of Sr-free alloy; the former was attributed to the formation of the SrSi2Al2 phase and uniform distribution of fine fibrous Si particles, which was triggered by the Sr addition. The mechanical properties of SIMA-treated samples in a semi-solid state were studied by tensile test. The higher ultimate tensile strength (UTS) of the Sr-containing M-SIMA processed alloy (267 MPa) than that of the Sr-free M-SIMA processed alloy (204 MPa) was associated with the highly dense and uniformly distributed Si particles (with Feret diameter of ~ 300 nm) in the former one. However, both specimens had the nearly equal size of primary α-Al grains. The UTS was ~ 31% higher while the elongation (%) was ~ 53% higher than that of the Sr-free alloy, manifesting the benefits of thermally stable SrSi2Al2 phase at the grain boundaries, and the interdendritic regions and reduction in porosities, blow holes and shrinkage cracks. [ABSTRACT FROM AUTHOR]

High-pressure die casting (HPDC) has been extensively used to manufacture aluminum alloy heat dissipation components in the fields of vehicles, electronics, and communication. With the increasing demand for HPDC heat dissipation components, the thermal conductivity of die-cast aluminum alloys is paid more attention. In this paper, a comprehensive review of the research progress on the thermal conductivity of HPDC aluminum alloys is provided. First of all, we introduce the general heat transport mechanism in aluminum alloys, including electrical transport and phonon transport. Secondly, we summarize several common die-cast aluminum alloy systems utilized for heat dissipation components, such as an Al–Si alloy system and silicon-free aluminum alloy systems, along with the corresponding composition optimizations for these alloy systems. Thirdly, the effect of processing parameters, which are significant for the HPDC process, on the thermal conductivity of HPDC aluminum alloys is discussed. Moreover, some heat treatment strategies for enhancing the thermal conductivity of die-cast aluminum alloys are briefly discussed. Apart from experimental findings, a range of theoretical models used to calculate the thermal conductivity of die-cast aluminum alloys are also summarized. This review aims to guide the development of new high-thermal-conductivity die-cast aluminum alloys. [ABSTRACT FROM AUTHOR]

The ability to modulate optical and electrical properties of two-dimensional (2D) semiconductors has sparked considerable interest in transition metal dichalcogenides (TMDs). Herein, we introduce a facile strategy for modulating optoelectronic properties of monolayer MoSe2 with external light. Photochromic diarylethene (DAE) molecules formed a 2-nm-thick uniform layer on MoSe2, switching between its closed- and open-form isomers under UV and visible irradiation, respectively. We have discovered that the closed DAE conformation under UV has its lowest unoccupied molecular orbital energy level lower than the conduction band minimum of MoSe2, which facilitates photoinduced charge separation at the hybrid interface and quenches photoluminescence (PL) from monolayer flakes. In contrast, open isomers under visible light prevent photoexcited electron transfer from MoSe2 to DAE, thus retaining PL emission properties. Alternating UV and visible light repeatedly show a dynamic modulation of optoelectronic signatures of MoSe2. Conductive atomic force microscopy and Kelvin probe force microscopy also reveal an increase in conductivity and work function of MoSe2/DAE with photoswitched closed-form DAE. These results may open new opportunities for designing new phototransistors and other 2D optoelectronic devices. [ABSTRACT FROM AUTHOR]

In situ tensile testing in a scanning electron microscope was used to study the effects of fiber orientation and colony boundaries in laser-refined fully eutectic Al–Si and Al–Si–Sr alloys. In Al–Si alloy, the measured tensile stress–strain response in samples from single colonies is highly dependent on the orientation of Si nanofiber relative to the loading direction. Tensile samples with multiple colonies exhibit improved strain hardening but the measured ductility was limited by cracking along inter-eutectic colony boundaries. The Al–Si eutectic alloys, doped with Sr and processed with finer spot size laser beam, exhibit higher yield strength in samples from single colony due to refined fiber diameter and inter-fiber spacing of nanoscale Si fibers. As a consequence, samples with multiple colonies exhibit sliding or cracking at eutectic colony boundaries before significant uniform elongation developed within the colonies. The low ductility of Al–Si–Sr sample could be ascribed to the reduced shear strength of colony boundary induced by Sr element addition. [ABSTRACT FROM AUTHOR]

In the present research, the Al-Si-Fe hypereutectic alloys with different Ti addition were prepared and the electric field treatment was performed on the alloys to regulate the phase morphology. The microstructure and mechanical properties of the alloys were characterized by OM, SEM, TEM, EPMA and tensile test. The results reveal that the Al-Si-Fe hypereutectic alloy prepared by conventional casting is mainly composed cubic β-Si phase, long rod-like and needle-like β-Al5FeSi phases. In addition, there are stacking faults in the β-Al5FeSi phase. Minor Ti addition in Al-Si-Fe hypereutectic alloy could change the needle-like phase into eutectic structure, decrease the size of β-Al5FeSi phase and homogenize the β-Si phase size. The more Ti addition tends to coarsen the β-Al5FeSi and β-Si phases, and moreover the needle-like phase precipitate again. The electric field treatment promotes the coarsening of β-Al5FeSi and β-Si phases in the Al-Si-Fe hypereutectic alloy with 0-1.0 wt.% Ti addition, but results in the refinement of β-Al5FeSi and β-Si phases in 1.5 wt.% Ti doped Al-Si-Fe hypereutectic alloy. Furthermore, the needle-like phase has been transformed into small-size eutectic structure in the 1.0 and 1.5 wt.% Ti doped Al-Si-Fe hypereutectic alloys. With the synergistical effect of Ti addition and electric field treatment, the 1.5 wt.% Ti doped Al-Si-Fe hypereutectic alloy obtains yield strength of 100 MPa and ultimate tensile strength of 113 MPa, which is about 26% and 37% higher than the conventional-cast Al-Si-Fe hypereutectic alloy. [ABSTRACT FROM AUTHOR]

Near-eutectic Al–11 wt pct Si alloys containing 0.005–0.02 wt pct Sr were solidified in conjunction with electromagnetic stirring, and the effect of this melt stirring on eutectic evolution was elucidated. Specimens solidified in the absence of electromagnetic stirring exhibited both lamellar and fibrous modified eutectic phases whereas those solidified while stirred showed spherical eutectic grains containing acicular unmodified Si phases. The spherical eutectic grains were found to evolve far from the eutectic front at the periphery of each such sample. Two different eutectic morphologies were identified in these grains: acicular in the outer parts and fibrous in the central regions. The eutectic Al in the center was determined to have essentially a single orientation whereas that at the periphery showed multiple crystallographic orientations. These results suggest that the two eutectic phases were evolved by different growth mechanisms. Thermal analysis of the cooling curves established that electromagnetic stirring decreased the eutectic depression temperature, indicating that eutectic modification resulting from the addition of Sr was inhibited by stirring. Melt stirring evidently fragmented the eutectic front after which the fragmented eutectic front served to nucleate spherical eutectic grains. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) molybdenum disulphide (MoS2) stands out with its unique tunable bandgap and optoelectronic properties, making it a prime focus in transition metal dichalcogenides (TMDs) research. It has wide-ranging applications in energy storage, electronics, optoelectronics and high-performance sensing materials. Synthesis methods fall into top-down (chemical, mechanical and liquid-phase exfoliation) and bottom-up (physical vapour deposition, chemical layer deposition, atomic layer deposition and solvothermal/hydrothermal) categories. Choosing the right synthesis method is pivotal as it significantly impacts the material's properties and application potential. 2D MoS2, owing to its natural abundance, adaptability, adjustable bandgap and high surface-to-volume ratio, finds utility in various domains like energy storage, catalysis, composite and sensors. This review delves into recent progress, challenges and future prospects in 2D MoS2 synthesis and applications. [ABSTRACT FROM AUTHOR]

In this study, the effect of successive hot and cold multi-directional forging (MDF) on the mechanical properties of the Al-9Si-0.6Mg-0.1Sr alloy was explored. The alloy was first homogenized and then forged at 200°C from 3 to 15 passes. After each three passes of hot forging, the samples were then cold forged up to three passes at room temperature. The microstructural examinations were carried out with X-ray diffraction technique and scanning electron microscopy equipped with energy-dispersive spectroscopy while mechanical properties were determined by tensile, compression and hardness tests. The hard particles were fragmented and began to distribute homogeneously into the matrix with increasing pass number of hot MDF. The yield, tensile and compressive strengths of the alloy reached to their maximum values at three passes of hot MDF along with hardness, above which they decreased, while its ductility exhibited a reverse trend. The cold MDF significantly increased the mechanical properties of initially hot MDFed samples. The nine passes in hot MDF were determined as the optimum pass number for obtaining the highest yield and tensile strength after cold MDF. These findings were evaluated according to dislocation strengthening, recrystallization and morphology of hard particles. [ABSTRACT FROM AUTHOR]

The presence and morphology of Fe-containing intermetallic phases affect the mechanical properties of aluminum alloys, especially in secondary Al–Si-based cast alloys. Although strontium (Sr) addition of 50 to 500 ppm is known to refine the needle-type eutectic silicon structure, the influence of Sr on the formation of Fe-intermetallic phases remains unclear. The present work investigates the combined additions of Sr and Mn to Al–9Si–0.6Fe–0.35Mg (All compositions are in wt pct except otherwise stated.) alloys on the formation of Fe-intermetallic phases at different solidification rates from ~ 1.5 to ~ 60 °C/s. Long and branched-type AlFeSi phase with size ranging from 50 to 120 µm are more common when solidified at the rate of 1.5 °C/s regardless of Sr and Mn additions. However, at the fast solidification rate of 60 °C/s, a 60 ppm Sr addition significantly reduced the average length of needle-shaped AlFeSi phase to less than 3 to 5 µm. Thermodynamic simulations have been performed using CALculation of PHAse Diagrams (CALPHAD) models to predict the formation of various phases and their possible interactions during solidification. The results indicated that the combination of a high solidification rate and about 60 ppm of Sr is beneficial to refining the δ-Al3FeSi2 phase in Al–Si–Mg alloys containing 0.6 pctFe. This unexpected finding of Fe-intermetallic refinement by low Sr addition (~60 ppm) provides an important guide in designing secondary alloys for sustainable casting applications. [ABSTRACT FROM AUTHOR]

We present LayerPCM, an extension of the polarizable-continuum model coupled to real-time time-dependent density-functional theory, for an efficient and accurate description of the electrostatic interactions between molecules and multilayered dielectric substrates on which they are physisorbed. The former are modeled quantum-mechanically, while the latter are treated as polarizable continua characterized by their dielectric constants. The proposed approach is purposely designed to simulate complex hybrid heterostructures with nano-engineered substrates including a stack of anisotropic layers. LayerPCM is suitable for describing the polarization-induced renormalization of frontier energy levels of the adsorbates in the static regime. Moreover, it can be reliably applied to simulating laser-induced ultrafast dynamics of molecules through the inclusion of electric fields generated by Fresnel-reflection at the substrate. Depending on the complexity of the underlying layer structure, such reflected fields can assume non-trivial shapes and profoundly affect the dynamics of the photo-excited charge carriers in the molecule. In particular, the interaction with the substrate can give rise to strong delayed fields, which lead to interference effects resembling those of multi-pulse-based spectroscopy. The robustness of the implementation and the above-mentioned features are demonstrated with a number of examples, ranging from intuitive models to realistic systems. [ABSTRACT FROM AUTHOR]