Playing with carbon and silicon at the nanoscale

Targeted Delivery of 2D Composite Minerals for Biofilm Removal

Microbiologically influenced corrosion (MIC) poses considerable challenges in various industries, prompting the exploration of advanced materials to mitigate microbial threats. This study successfully synthesized nanoscale vermiculite (VMT) from natural seawater and utilized it as a foundation to integrate magnetic nanoparticles (Fe3O4) and chlorhexidine acetate (CA) for inhibiting MIC. A comprehensive investigation encompassing the synthesis, characterization, and application of these VMT/Fe3O4/CA composites was conducted to evaluate their antimicrobial effectiveness against Escherichia coli, Staphylococcus aureus, and sulfate-reducing bacteria (SRB), demonstrating an efficacy exceeding 99.5%. Moreover, the composite material demonstrated the capability to align with a magnetic field, enabling precise drug targeting and release, thereby facilitating biofilm removal. This research makes a significant contribution to the advancement of intelligent, efficient, and eco-friendly corrosion protection solutions.

The role of HMGB1 on SiC NPs-induced inflammation response in lung epithelial-macrophage co-culture system

In recent years, carbonized silicon nanoparticles (SiC NPs) have found widespread scientific and engineering applications, raising concerns about potential human health risks. SiC NPs may induce pulmonary damage through sustained inflammatory responses and oxidative stress, with unclear toxicity mechanisms. This study uses an in vitro co-culture model of alveolar macrophages (NR8383) and alveolar epithelial cells (RLE-6TN) to simulate the interaction between airway epithelial cells and immune cells, providing initial insights into SiC NP-triggered inflammatory responses. The research reveals that increasing SiC NP exposure prompts NR8383 cells to release high mobility group box 1 protein (HMGB1), which migrates into RLE-6TN cells and activates the receptor for advanced glycation end-products (RAGE) and Toll-like receptor 4 (TLR4). RAGE and TLR4 synergistically activate the MyD88/NF-κB inflammatory pathway, ultimately inducing inflammatory responses and oxidative stress in RLE-6TN cells, characterized by excessive ROS generation and altered cytokine levels. Pretreatment with RAGE and TLR4 inhibitors attenuates SiC-induced HMGB1 expression and downstream pathway proteins, reducing inflammatory responses and oxidative damage. This highlights the pivotal role of RAGE-TLR4 crosstalk in SiC NP-induced pulmonary inflammation, providing insights into SiC NP cytotoxicity and nanomaterial safety guidelines.

Anharmonic Vibrational Spectroscopy of Germanium-Containing Clusters, GexC4-x and GexSi4-x (x = 0-4), for Interstellar Detection

An extensive, high-level theoretical study on tetra-atomic germanium carbide/silicide clusters is presented. Accurate harmonic and anharmonic vibrational frequencies and rotational constants are calculated at the CCSD(T)-F12a(b)/cc-pVT(Q)Z-F12 levels of theory. With growing capabilities to discern more of the chemical composition of the interstellar medium (ISM), an accurate database of reference material is required. The presence of carbon is ubiquitous in the ISM, and silicon is known to be present in interstellar dust grains; however, germanium-containing molecules remain elusive. To begin understanding the presence and role of germanium in the ISM, we present this study of the vibrational and rotational spectroscopic properties of various germanium-containing molecules to aid in their potential identification in the ISM with modern observational tools such as the James Webb Space Telescope. Structures studied herein include rhomboidal (r-), diamond (d-), and trapezoidal (t-) tetra-atomic molecules of the form GexC4-x and GexSi4-x, where x = 0-4. The most promising structure for detection is r-Ge2C2 via the ν4 mode with a frequency of 802.7 cm-1 (12.5 μm) and an intensity of 307.2 km mol-1. Other molecules that are potentially detectable, i.e., through vibrational modes or rotational transitions, include r-Ge3C, r-GeSi3, d-GeC3, r-GeC3, and t-Ge2C2.

Strain-Dependent Effects on Confinement of Folded Acoustic and Optical Phonons in Short-Period (XC)m/(YC)n with X,Y (≡Si, Ge, Sn) Superlattices

Carbon-based novel low-dimensional XC/YC (with X, Y ≡ Si, Ge, and Sn) heterostructures have recently gained considerable scientific and technological interest in the design of electronic devices for energy transport use in extreme environments. Despite many efforts made to understand the structural, electronic, and vibrational properties of XC and XxY1-xC alloys, no measurements exist for identifying the phonon characteristics of superlattices (SLs) by employing either an infrared and/or Raman scattering spectroscopy. In this work, we report the results of a systematic study to investigate the lattice dynamics of the ideal (XC)m/(YC)n as well as graded (XC)10-∆/(X0.5Y0.5C)∆/(YC)10-∆/(X0.5Y0.5C)∆ SLs by meticulously including the interfacial layer thickness ∆ (≡1-3 monolayers). While the folded acoustic phonons (FAPs) are calculated using a Rytov model, the confined optical modes (COMs) and FAPs are described by adopting a modified linear-chain model. Although the simulations of low-energy dispersions for the FAPs indicated no significant changes by increasing ∆, the results revealed, however, considerable "downward" shifts of high frequency COMs and "upward" shifts for the low energy optical modes. In the framework of a bond polarizability model, the calculated results of Raman scattering spectra for graded SLs are presented as a function of ∆. Special attention is paid to those modes in the middle of the frequency region, which offer strong contributions for enhancing the Raman intensity profiles. These simulated changes are linked to the localization of atomic displacements constrained either by the XC/YC or YC/XC unabrupt interfaces. We strongly feel that this study will encourage spectroscopists to perform Raman scattering measurements to check our theoretical conjectures.

Theoretical Insight into the Band Alignment at High-κ Oxide XO2/Diamond (X = Hf and Zr) Interfaces with a SiO2 Interlayer for MOS Devices

Diamond has become a promising candidate for high-power devices based on its ultrawide bandgap and excellent thermoelectric properties, where an appropriate gate dielectric has been a bottleneck hindering the development of diamond devices. Herein, we have systematically investigated the structural arrangement and electronic properties of diamond/high-κ oxide (HfO2, ZrO2) heterojunctions by first-principles calculations with a SiO2 interlayer. Charge analysis reveals that the C-Si bonding interface attracts a large amount of charge concentrated at the diamond interface, indicating the potential for the formation of a 2D hole gas (2DHG). The diamond/HfO2 and diamond/ZrO2 heterostructures exhibit similar "Type II" band alignments with VBOs of 2.47 and 2.21 eV, respectively, which is consistent with experimental predictions. The introduction of a SiO2 dielectric layer into the diamond/SiO2/high-κ stacks exhibits the typical "Type I″ straddling band offsets (BOs). In addition, the wide bandgap SiO2 interlayer keeps the valence band maximum (VBM) and conduction band minimum (CBM) in the stacks away from those of diamond, effectively confining the electrons and holes in MOS devices. This work exhibits the potential of SiO2/high-κ oxide gate dielectrics for diamond devices and provides theoretical insights into the rational design of high-quality gate dielectrics for diamond-based MOS device applications.

Examining O[Formula: see text] adsorption on pristine and defective popgraphene sheets: A DFT study

CONTEXT

Popgraphene (PopG) is a two-dimensional carbon-based material with fused pentagonal and octagonal rings. Like graphene, it exhibits a metallic band gap and exceptional thermal, dynamic, and mechanical stability. Here, we theoretically study the electronic and structural properties of PopG monolayers, including their doped and vacancy-endowed versions, as O[Formula: see text] adsorbers. Our findings show that pristine and vacancy-endowed PopG sheets have a comparable ability to adsorb O[Formula: see text] molecules, with adsorption energies ranging from [Formula: see text]0.57 to [Formula: see text]0.59 eV (physisorption). In these cases, octagonal rings play a dominant role in the adsorption mechanism. Platinum and Silicon doping enhance the O[Formula: see text] adsorption in areas close to the octagonal rings, resulting in adsorption energies ranging from [Formula: see text]1.13 to [Formula: see text]2.56 eV (chemisorption). Furthermore, we computed the recovery time for the adsorbed O[Formula: see text] molecules. The results suggest that PopG/O[Formula: see text] interaction in pristine and vacancy-endowed cases can change the PopG electronic properties before O[Formula: see text] diffusion.

METHODS

Density Functional Theory (DFT) simulations, with Van der Waals corrections (DFT-D, within the Grimme scheme), were performed to study the structural and electronic properties of PopG/O[Formula: see text] systems using the DMol3 code within the Biovia Materials Studio software. The exchange and correlation functions are treated within the generalized gradient approximation (GGA) as parameterized by Perdew-Burke-Ernzerhof (PBE) functional. We used the double-zeta plus polarization (DZP) for the basis set in these cases. We also considered the BSSE correction through the counterpoise method and the nuclei-valence electron interactions by including semi-core DFT pseudopotentials.

A review on composite strategy of MOF derivatives for improving electromagnetic wave absorption

To address the electromagnetic wave (EMW) pollution issues caused by the development of electronics and wireless communication technology, it is urgent to develop efficient EMW-absorbing materials. With controllable composition, diverse structure, high porosity, and large specific surface area, metal-organic framework (MOF) derivatives have sparked the infinite passion and creativity of researchers in the electromagnetic field. Against the challenges of poor inherent impedance matching and insufficient attenuation capability of pure MOF derivative, designing and developing MOF derivative-based composites by compounding MOF with other materials, such as graphene, CNTs, MXene, and so on, has been an effective strategy for constructing high-efficiency EMW absorbing materials. This review systematically expounds the research progress of MOF derivative-based composite strategies, and discusses the challenges and opportunities faced by MOF derivatives in the field of EMW absorption. This work can provide some good ideas for researchers to design and prepare high-efficiency MOF-based EMW absorbing materials in applications of next-generation electronics and aerospace.

Bottom-Up Growth of Monolayer Honeycomb SiC

The long theorized two-dimensional allotrope of SiC has remained elusive amid the exploration of graphenelike honeycomb structured monolayers. It is anticipated to possess a large direct band gap (2.5 eV), ambient stability, and chemical versatility. While sp^{2} bonding between silicon and carbon is energetically favorable, only disordered nanoflakes have been reported to date. Here we demonstrate large-area, bottom-up synthesis of monocrystalline, epitaxial monolayer honeycomb SiC atop ultrathin transition metal carbide films on SiC substrates. We find the 2D phase of SiC to be almost planar and stable at high temperatures, up to 1200 °C in vacuum. Interactions between the 2D-SiC and the transition metal carbide surface result in a Dirac-like feature in the electronic band structure, which in the case of a TaC substrate is strongly spin-split. Our findings represent the first step towards routine and tailored synthesis of 2D-SiC monolayers, and this novel heteroepitaxial system may find diverse applications ranging from photovoltaics to topological superconductivity.

Modulating the Schottky barrier of MXenes/2D SiC contacts via functional groups and biaxial strain: a first-principles study

Two-dimensional (2D) graphene-like SiC has attracted intense interest recently due to its unique electrical and physical properties. In implementing 2D semiconductors in device applications, one of the main challenges so far has been the formation of a high-quality Schottky barrier owing to the strong Fermi level pinning (FLP) at the interface of traditional metal-2D semiconductor contacts. In this paper, the 2D MXenes Ti₃C₂T₂ (T = F, O, OH) are proposed to serve as electrodes for 2D SiC. The structural and barrier properties of the Ti₃C₂T₂/SiC contacts were systematically investigated based on first-principles calculations combined with the GGA-PBE and HSE06 functionals. It is found that Ti₃C₂T₂ can be bonded with 2D SiC by van der Waals (vdW) interactions. Weak FLP is exhibited at Ti₃C₂T₂/SiC vdW contacts. The type of contact can be tuned by changing the functional T group of Ti₃C₂T₂. Ti₃C₂F₂/SiC and Ti₃C₂O₂/SiC contacts exhibit a p-type Schottky contact and p-type Ohmic contact, respectively, whereas an n-type Ohmic contact occurs in the Ti₃C₂(OH)₂/SiC contact. In addition, the calculated tunneling possibility (T_B) is ∼20% between Ti₃C₂T₂ and SiC, indicating weak bonding at the Ti₃C₂T₂/SiC vdW junctions. Furthermore, the Schottky barrier height and T_B of the Ti₃C₂(OH)₂/SiC contacts can be modulated via the biaxial strain. The controllable contact type and barrier in Ti₃C₂T₂/SiC contacts provide guidelines for developing high-performance 2D SiC optoelectronic and electronic devices.

Strain Effects on the Electronic and Optical Properties of Blue Phosphorene

Monolayer blue phosphorene (BlueP) systems were investigated under biaxial strain range from −10% to +10%. All these systems exhibit excellent stability, accompanying changes in the electronic and optical properties. BlueP becomes metallic at −10% strain and transforms into a direct semiconductor at 10% strain while maintaining indirect semiconductor behaviors at −8% to +8% strain. The bandgap of BlueP decreases linearly with strain, and tensile strain exhibits a more moderate bandgap modulation than compressive strain. The real part of the dielectric function of BlueP is enhanced under compressive strain, while the optical absorption in the visible and the infrared light regions increases significantly under tensile strain. The maximum absorption coefficient of 0.52 ×105/cm occurs at 530 nm with the 10% strain. Our analysis indicates that the semiconductor–metal transition and the indirect–direct bandgap transition are the competition results of the energy states near the Fermi level under a massive strain. The potent compressive strain leads the py orbitals of the conduction band to move downward and pass through the Fermi level at the K point. The robust tensile strain guides the energy states at the Γ point to approach the Fermi level and become the band edges. Our results suggest that the energy storage capacity of BlueP can be significantly improved by compressive strain, while the visible light photocatalytic performance is enhanced by tensile strains of less than 8%. Our works provide a reference for the practical applications of BlueP in photocatalyst, photovoltaic cells, and electronic devices.

Theoretical Study on Electronic, Magnetic and Optical Properties of Non-Metal Atoms Adsorbed onto Germanium Carbide

Nine kinds of non-metal atoms adsorbed into germanium carbide (NM-GeC) systems wereare investigated by first-principles calculations. The results show that the most stable adsorption positions vary with the NM atoms, and C-GeC exhibits the strongest adsorption. The adsorption of NM atoms causes changes in the electronic, optical and magnetic properties of the GeC system. F- and Cl-GeC turn into magnetic metals, P-GeC becomes a half-metal and H- and B-GeC appear as non-magnetic metals. Although C- and O-GeC remain non-magnetic semiconductors, N-GeC presents the behaviors of a magnetic semiconductor. Work function decreases in H-, B- and N-SiC, reaching a minimum of 3.37 eV in H-GeC, which is 78.9% of the pristine GeC. In the visible light region, redshifts occur in the absorption spectrum of C-GeC , with strong absorption in the wavelength range from 400 to 600 nm. Our analysis shows that the magnetism in semiconducting NM-GeC is attributed to the spinning state of the unbonded electrons of the NM atoms. Our study demonstrates the applications of NM-GeC in spintronics, optoelectronics and photovoltaic cells, and it provides a reference for analyzing magnetism in semiconducting NM materials.

Manufacturing of Complex Silicon-Carbon Structures: Exploring SixCy Materials

This paper reports on the manufacturing of complex three-dimensional Si/C structures via a chemical vapor deposition method. The structure and properties of the grown materials were characterized using various techniques including scanning electron microscopy, aberration-corrected transmission electron microscopy, confocal Raman spectroscopy, and X-ray photoelectron spectroscopy. The spectroscopy results revealed that the grown materials were composed of micro/nanostructures with various compositions and dimensions. These included two-dimensional silicon carbide (SiC), cubic silicon, and various SiC polytypes. The coexistence of these phases at the nano-level and their interfaces can benefit several Si/C-based applications ranging from ceramics and structural applications to power electronics, aerospace, and high-temperature applications. With an average density of 7 mg/cm³, the grown materials can be considered ultralightweight, as they are three orders of magnitude lighter than bulk Si/C materials. This study aims to impact how ceramic materials are manufactured, which may lead to the design of new carbide materials or Si/C-based lightweight structures with additional functionalities and desired properties.

Electronic, Magnetic, and Optical Performances of Non-Metals Doped Silicon Carbide

The configurations of nine different non-metals doped silicon carbide (NM-SiC) were structured by using the density functional theory (DFT). The magnetic, electronic, and optical properties of each NM-SiC are investigated at the most stable structure with the maximum binding energy. Although the O-, Si-, and S-SiC systems are still non-magnetic semiconductors, the N- and P-SiC systems have the properties of the magnetic semiconductors. The H-, F-, and Cl-SiC systems exhibit the half-metal behaviors, while the B-SiC system converts to magnetic metal. The redistribution of charges occurs between non-metals atoms and adjacent C atoms. For the same doping position, the more charges are transferred, the greater the binding energy of the NM-SiC system. The work function of the NM-SiC systems is also adjusted by the doping of NM atoms, and achieves the minimum 3.70 eV in the P-SiC, just 77.1% of the original SiC. The absorption spectrum of the NM-SiC systems occurs red-shift in the ultraviolet light region, accompanying the decrease of absorption coefficient. These adjustable magnetic, electronic, and optical performances of NM-SiC expand the application fields of two-dimensional (2D) SiC, especially in designing field emission and spintronics devices.

Experimental Analysis of Ductile Cutting Regime in Face Milling of Sintered Silicon Carbide

In this study, sintered silicon carbide is machined on a high-precision milling machine with a high-speed spindle, closed-loop linear drives and friction-free micro gap hydrostatics. A series of experiments was undertaken varying the relevant process parameters such as feedrate, cutting speed and chip thickness. For this, the milled surfaces are characterized in a process via an acoustic emission sensor. The milled surfaces were analyzed via confocal laser scanning microscopy and the ISO 25178 areal surface quality parameters such as Sa, Sq and Smr are determined. Moreover, scanning electron microscopy was used to qualitatively characterize the surfaces, but also to identify sub-surface damages such as grooves, breakouts and pitting. Raman laser spectroscopy is used to identify possible amorphization and changes to crystal structure. We used grazing incidence XRD to analyze the crystallographic structure and scanning acoustic microscopy to analyze sub-surface damages. A polycrystalline diamond tool was able to produce superior surfaces compared to diamond grinding with an areal surface roughness Sa of below 100 nm in a very competitive time frame. The finished surface exhibits a high gloss and reflectance. It can be seen that chip thickness and cutting speed have a major influence on the resulting surface quality. The undamaged surface in combination with a small median chip thickness is indicative of a ductile cutting regime.

First-principles study of the optical and thermoelectric properties of tetragonal-silicene

We report the optical and thermoelectric properties of the two-dimensional Dirac material T-silicene (TS) sheet and nanoribbons (NRs) by first-principles calculations. Both the optical and thermoelectric properties of TS can be modified by tailoring the sheet into nanoribbons of different widths and edge geometries. The optical response of the structures is highly anisotropic. A π interband transition occurs in the visible range of incident light with parallel polarization. The optical response for asymmetric arm-chair TS nanoribbons (ATSNRs) is larger than for symmetric ATSNRs. The absorptions of asymmetric ATSNR are redshifted due to a decrease in the bandgap with the width of the NRs. Plasma frequencies of the sheet and the NRs are identified from the imaginary part of the dielectric function and electron energy loss spectra curves. Thermoelectric properties like electrical conductivity, Seebeck coefficient, power factor, and electronic figure of merit are also studied. Compared with graphene, the TS sheet possesses a higher electrical conductivity and a better figure of merit. Among the NRs, asymmetric ATSNRs exhibit a better thermoelectric performance. All these intriguing features of TS may shed light on fabricating smart opto-electronic and thermoelectric devices.

Structural and electronic properties of C60 fullerene network self-assembled on metal-covered semiconductor surfaces

Using first-principles density functional theory calculations, we made an accurate structural characterization of the C₆₀ superstructures self-assembled on the Tl-adsorbed Si(111) and Ge(111) surfaces, which finds a good agreement with the recent scanning tunneling microscopy observations. Our band structure calculations revealed the semi-metallic character of the C₆₀/Tl/Si(111) system, while the C₆₀/Tl/Ge(111) system was found to show up the pronounced metallic character due to the cascade of the flat bands lying in the vicinity of the Fermi level. The latter is a fingerprint for strong correlation effects in the C₆₀/Tl/Ge(111) system, which makes it a promising object for studying electrical transport phenomena and opens the prospects for its application in the molecular-based electronic devices. We elucidated the details of the molecule-substrate and intermolecular interactions and discussed the character of a charge transfer in both systems.

Two-Dimensional Silicon Carbide: Emerging Direct Band Gap Semiconductor

As a direct wide bandgap semiconducting material, two-dimensional, 2D, silicon carbide has the potential to bring revolutionary advances into optoelectronic and electronic devices. It can overcome current limitations with silicon, bulk SiC, and gapless graphene. In addition to SiC, which is the most stable form of monolayer silicon carbide, other compositions, i.e., SixCy, are also predicted to be energetically favorable. Depending on the stoichiometry and bonding, monolayer SixCy may behave as a semiconductor, semimetal or topological insulator. With different Si/C ratios, the emerging 2D silicon carbide materials could attain novel electronic, optical, magnetic, mechanical, and chemical properties that go beyond those of graphene, silicene, and already discovered 2D semiconducting materials. This paper summarizes key findings in 2D SiC and provides insight into how changing the arrangement of silicon and carbon atoms in SiC will unlock incredible electronic, magnetic, and optical properties. It also highlights the significance of these properties for electronics, optoelectronics, magnetic, and energy devices. Finally, it will discuss potential synthesis approaches that can be used to grow 2D silicon carbide.

Enhanced Piezoresistive Behavior of SiC Nanowire by Coupling with Piezoelectric Effect

Improving the sensitivity of the piezoresistive behavior of semiconductor nanostructures is critically important because it is one of the keys to explore advanced pressure sensors with desired sensitivity. Herein, we reported a strategy for improving the piezoresistive behavior of SiC nanowire by coupling with the piezoelectric effect of ZnO nanolayers, which were grown by an atomic layer deposition approach. As a result, the detected current of the as-constructed ZnO/SiC heterojunction nanowires is 6 times more than SiC nanowires, suggesting its substantially improved sensitivity. Moreover, the measured ΔR/R₀ value and gauge factor (GF) of the ZnO/SiC heterojunction nanowires could be up to 0.82 and 50.93, respectively, which was profoundly higher than those of the SiC counterpart and most of reported positive piezoresistive SiC sensors.

Generation and structural characterization of Ge carbides GeCn (n = 4, 5, 6) by laser ablation, broadband rotational spectroscopy, and quantum chemistry

Following the recent discovery of T-shaped GeC₂, rotational spectra of three larger Ge carbides, linear GeC₄, GeC₅, and GeC₆ have been observed using chirped pulse and cavity Fourier transform microwave spectroscopy and a laser ablation molecule source, guided by new high-level quantum chemical calculations of their molecular structure. Like their isovalent Si-bearing counterparts, Ge carbides with an even number of carbon atoms beyond GeC₂ are predicted to possess ¹Σ ground electronic states, while odd-numbered carbon chains are generally ³Σ; all are predicted to be highly polar. For the three new molecules detected in this work, rotational lines of four of the five naturally occurring Ge isotopic variants have been observed between 6 and 22 GHz. Combining these measurements with ab initio force fields, the Ge-C bond lengths have been determined to high precision: the derived values of 1.776 Å for GeC₄, 1.818 Å for GeC₅, and 1.782 Å for GeC₆ indicate a double bond between these two atoms. Somewhat surprisingly, the spectrum of GeC₅ very closely resembles that of a ¹Σ molecule, implying a spin-spin coupling constant λ in excess of 770 GHz for this radical, a likely consequence of the large spin-orbit constant of atomic Ge (∼1000 cm^-1). A systematic comparison between the production of SiC_n and GeC_n chains by laser ablation has also been undertaken. The present work suggests that other large metal-bearing molecules may be amenable to detection by similar means.

Unprecedented Piezoresistance Coefficient in Strained Silicon Carbide

Reports reveal that the piezoresistance coefficients of silicon carbide (SiC) nanowires (NWs) are 2 to 4 times smaller than those of their corresponding bulk counterparts. It is a challenge to eliminate contamination in adhering NWs onto substrates. In this study, a new setup was developed, in which NWs were manipulated and fixed by a goat hair and conductive silver epoxy in air, respectively, in the absence of any depositions. The goat hair was not consumed during manipulation of the NWs. The process took advantage of the stiffness and tapered tip of the goat hair, which is unlike the loss issue of beam sources in depositions. With the new fixing method, in situ transmission electron microscopy (TEM) electromechanical coupling measurements were performed on pristine SiC NWs. The piezoresistance coefficient and carrier mobility of SiC NW are -94.78 × 10^-11 Pa^-1 and 30.05 cm² V^-1 s^-1, respectively, which are 82 and 527 times respectively greater than those of SiC NWs reported previously. We, for the first time, report that the piezoresistance coefficient of SiC NW is 17 times those of its bulk counterparts. These findings provide new insights to develop high performance SiC devices and to help avoid catastrophic failure when working in harsh environments.

Ultrahigh Recovery of Fracture Strength on Mismatched Fractured Amorphous Surfaces of Silicon Carbide

Nanowires (NWs) have been envisioned as building blocks of nanotechnology and nanodevices. In this study, NWs were manipulated using a weasel hair and fixed by conductive silver epoxy, eliminating the contaminations and damages induced by conventional beam depositions. The fracture strength of the amorphous silicon carbide was found to be 8.8 GPa, which was measured by in situ transmission electron microscopy nanomechanical testing, approaching the theoretical fracture limit. Here, we report that self-healing of mismatched fractured amorphous surfaces of brittle NWs was discovered. The fracture strength was found to be 5.6 GPa on the mismatched fractured surfaces, recovering 63.6% of that of pristine NWs. This is an ultrahigh recovery, due to the limits of reconstruction of dangling bonds on the fractured amorphous surfaces and the mismatched areas. Simulation by molecular dynamics showed fracture strength recovery of 65.9% on the mismatched fractured amorphous surfaces, which is in good agreement with the experimental results. Healing on the mismatched fractured amorphous surfaces is by reorganization of Si-C bonds forming Si-C and Si-Si bonds. The potential energy increases 2.6 eV in the reorganized Si-C bonds and decreases by 3.2 and 1.9 eV, respectively, in the formed Si-C and Si-Si bonds. These findings provide insights for the reliability, design, and fabrication of high performance NW-based devices, to avoid catastrophic failure working in harsh and extreme environments.

High-fidelity spin and optical control of single silicon-vacancy centres in silicon carbide

Scalable quantum networking requires quantum systems with quantum processing capabilities. Solid state spin systems with reliable spin–optical interfaces are a leading hardware in this regard. However, available systems suffer from large electron–phonon interaction or fast spin dephasing. Here, we demonstrate that the negatively charged silicon-vacancy centre in silicon carbide is immune to both drawbacks. Thanks to its ⁴A₂ symmetry in ground and excited states, optical resonances are stable with near-Fourier-transform-limited linewidths, allowing exploitation of the spin selectivity of the optical transitions. In combination with millisecond-long spin coherence times originating from the high-purity crystal, we demonstrate high-fidelity optical initialization and coherent spin control, which we exploit to show coherent coupling to single nuclear spins with ∼1 kHz resolution. The summary of our findings makes this defect a prime candidate for realising memory-assisted quantum network applications using semiconductor-based spin-to-photon interfaces and coherently coupled nuclear spins.

Point defects in solids have potential applications in quantum technologies, but the mechanisms underlying different defects’ performance are not fully established. Nagy et al. show how the wavefunction symmetry of silicon vacancies in SiC leads to promising optical and spin coherence properties.

Synthesis and Application of CCQDs as a Novel Type of Environmentally Friendly Scale Inhibitor

Carbon quantum dots (CQDs) are promising nanomaterials since they have smaller particle size, excellent biocompatibility, and low toxicity. However, no  one has found their high-scale inhibition performance so far. In this article, a new kind of green scale inhibitor, carboxyl carbon quantum dots (CCQDs), was synthesized through a simple method of thermal decomposition of citric acid. The as-prepared CCQDs have excellent scale inhibition performance for CaSO₄ and BaSO₄. With a static test of scale inhibition at a temperature of 0-80 °C, the antiscaling efficiency can reach 100% with low additions of CCQDs.

Thermally Carbonized Porous Silicon and Its Recent Applications

Recent progress in research on thermally carbonized porous silicon (TCPSi) and its applications is reported. Despite a slow start, thermal carbonization has now started to gain interest mainly due to new emerging areas for applications. These new areas, such as optical sensing, drug delivery, and energy storage, require stable surface chemistry and physical properties. TCPSi is known to have all of these desired properties. Herein, the above-listed properties of TCPSi are summarized, and the carbonization processes, functionalization, and characterization of TCPSi are reviewed. Moreover, some of the emerging fields of TCPSi applications are discussed and recent advances in the fields are introduced.

Chemical, structural and photovoltaic properties of graded CdSxSe1−x thin films grown by chemical bath deposition on GaAs(100)

Chemically graded Cd(S,Se) thin film and photovoltaic cell illustration.

Controllable Fabricating Dielectric-Dielectric SiC@C Core-Shell Nanowires for High-Performance Electromagnetic Wave Attenuation

Heterostructured dielectric-dielectric nanowires of SiC core and carbon shell (SiC@C) with high-performance electromagnetic wave absorption were synthesized by combining an interfacial in situ polymer encapsulation and carbonization process. This approach overcomes the shortcomings of previous reported methods to prepare carbon shell that both carbon shell and free carbon particles are formed simultaneously. In our developed approach, the core of SiC nanowires are first positively charged. Then the negative resorcinol-formaldehyde polymers as the carbon source are anchored on SiC nanowires under the attraction of electrostatic force, which well suppresses the nucleation of free carbon particles. The thickness of the carbon shell could be modulated from 4 to 20 nm by simply adjusting the moral ratio of resorcinol to SiC nanowires. The resulting SiC@C core-shell nanostructures without free carbon particles offer synergism among the SiC nanowires and the carbon shells, generating multiple dipolar polarization, surfaced polarization, and associated relaxations, which endow SiC@C hybrid nanowires with a minimum reflection loss (R_L) value of -50 dB at the frequency of 12 GHz and an effective absorption bandwidth of 8 GHz with R_L value under -10 dB at the optimized state. Our results demonstrate that SiC@C hybrid nanowires are promising candidates for electromagnetic wave absorption applications.

Light and Strong Hierarchical Porous SiC Foam for Efficient Electromagnetic Interference Shielding and Thermal Insulation at Elevated Temperatures

A novel light but strong SiC foam with hierarchical porous architecture was fabricated by using dough as raw material via carbonization followed by carbothermal reduction with silicon source. A significant synergistic effect is achieved by embedding meso- and nanopores in a microsized porous skeleton, which endows the SiC foam with high-performance electromagnetic interference (EMI) shielding, thermal insulation, and mechanical properties. The microsized skeleton withstands high stress. The meso- and nanosized pores enhance multiple reflection of the incident electromagnetic waves and elongate the path of heat transfer. For the hierarchical porous SiC foam with 72.8% porosity, EMI shielding can be higher than 20 dB, and specific EMI effectiveness exceeds 24.8 dB·cm³·g^-1 at a frequency of 11 GHz at 25-600 °C, which is 3 times higher than that of dense SiC ceramic. The thermal conductivity reaches as low as 0.02 W·m^-1·K^-1, which is comparable to that of aerogel. The compressive strength is as high as 9.8 MPa. Given the chemical and high-temperature stability of SiC, the fabricated SiC foam is a promising candidate for modern aircraft and automobile applications.

Facile electrosynthesis of silicon carbide nanowires from silica/carbon precursors in molten salt

Silicon carbide nanowires (SiC NWs) have attracted intensive attention in recent years due to their outstanding performances in many applications. A large-scale and facile production of SiC NWs is critical to its successful application. Here, we report a simple method for the production of SiC NWs from inexpensive and abundantly available silica/carbon (SiO₂/C) precursors in molten calcium chloride. The solid-to-solid electroreduction and dissolution-electrodeposition mechanisms can easily lead to the formation of homogenous SiC NWs. This template/catalyst-free approach greatly simplifies the synthesis procedure compared to conventional methods. This general strategy opens a direct electrochemical route for the conversion of SiO₂/C into SiC NWs, and may also have implications for the electrosynthesis of other micro/nanostructured metal carbides/composites from metal oxides/carbon precursors.

Velcro-Inspired SiC Fuzzy Fibers for Aerospace Applications

The most recent and innovative silicon carbide (SiC) fiber ceramic matrix composites, used for lightweight high-heat engine parts in aerospace applications, are woven, layered, and then surrounded by a SiC ceramic matrix composite (CMC). To further improve both the mechanical properties and thermal and oxidative resistance abilities of this material, SiC nanotubes and nanowires (SiCNT/NWs) are grown on the surface of the SiC fiber via carbon nanotube conversion. This conversion utilizes the shape memory synthesis (SMS) method, starting with carbon nanotube (CNT) growth on the SiC fiber surface, to capitalize on the ease of dense surface morphology optimization and the ability to effectively engineer the CNT-SiC fiber interface to create a secure nanotube-fiber attachment. Then, by converting the CNTs to SiCNT/NWs, the relative morphology, advantageous mechanical properties, and secure connection of the initial CNT-SiC fiber architecture are retained, with the addition of high temperature and oxidation resistance. The resultant SiCNT/NW-SiC fiber can be used inside the SiC ceramic matrix composite for a high-heat turbo engine part with longer fatigue life and higher temperature resistance. The differing sides of the woven SiCNT/NWs act as the "hook and loop" mechanism of Velcro but in much smaller scale.

Fluorescent color centers in laser ablated 4H-SiC nanoparticles

Nanostructured and bulk silicon carbide (SiC) has recently emerged as a novel platform for quantum nanophotonics due to its harboring of paramagnetic color centers, having immediate applications as a single photon source and spin optical probes. Here, using ultra-short pulsed laser ablation, we fabricated from electron irradiated bulk 4H-SiC, 40-50 nm diameter SiC nanoparticles, fluorescent at 850-950 nm. This photoluminescence is attributed to the silicon vacancy color centers. We demonstrate that the original silicon vacancy color centers from the target sample were retained in the final nanoparticles solution, exhibiting excellent colloidal stability in water over several months. Our work is relevant for quantum nanophotonics, magnetic sensing, and biomedical imaging applications.

Ultra-small photoluminescent silicon-carbide nanocrystals by atmospheric-pressure plasmas

Highly size-controllable synthesis of free-standing perfectly crystalline silicon carbide nanocrystals has been achieved for the first time through a plasma-based bottom-up process. This low-cost, scalable, ligand-free atmospheric pressure technique allows fabrication of ultra-small (down to 1.5 nm) nanocrystals with very low level of surface contamination, leading to fundamental insights into optical properties of the nanocrystals. This is also confirmed by their exceptional photoluminescence emission yield enhanced by more than 5 times by reducing the nanocrystals sizes in the range of 1-5 nm, which is attributed to quantum confinement in ultra-small nanocrystals. This method is potentially scalable and readily extendable to a wide range of other classes of materials. Moreover, this ligand-free process can produce colloidal nanocrystals by direct deposition into liquid, onto biological materials or onto the substrate of choice to form nanocrystal films. Our simple but efficient approach based on non-equilibrium plasma environment is a response to the need of most efficient bottom-up processes in nanosynthesis and nanotechnology.

From graphene to silicon carbide: ultrathin silicon carbide flakes

This study presents a new ultrathin SiC structure prepared by a catalyst free carbothermal method and post-sonication process. We have found that merging ultra-light 3D graphene foam and SiO together at high temperature leads to the formation of a complex SiC structure consisting of 3D SiC foam covered with traditional 1D nanowires. Upon breaking off, the 3D SiC was confirmed to be made from 2D nanosheets. The resulting novel 2D SiC nanosheets/nanoflakes were thoroughly investigated by using optical microscope, SEM, EDS, TEM, STEM, AFM, and Raman, which verified the highly crystallised structure feature. AFM results revealed an average thickness of 2-3 nm and average size of 2 μm for the flakes. This new SiC structure could not only actualise SiC usage for nano-electronic devices but is also expected to open new applications as well.

Gas-Phase Spectroscopic Detection and Structural Elucidation of Carbon-Rich Group 14 Binary Clusters: Linear GeC3Ge

Guided by high-level quantum-chemical calculations at the CCSD(T) level of theory, the first polyatomic germanium-carbon cluster, linear Ge2C3, has been observed at high spectral resolution in the gas phase through its remarkably complex fundamental antisymmetric C-C stretching mode ν3 located at 1932 cm(-1). The observation of a total of six isotopic species permits the derivation of a highly accurate value for the equilibrium Ge-C bond length. The present study suggests that many more Ge-C species might be detectable in the future using a combination of laser-ablation techniques for production and high-resolution infrared and/or microwave techniques for spectroscopic detection.

Atomic-scale characterization of occurring phenomena during hot nanometric cutting of single crystal 3C–SiC

Nanometric cutting of single crystal 3C–SiC on the three principal crystal orientations at various cutting temperatures spanning from 300 K to 3000 K was investigated by the use of molecular dynamics (MD) simulation.

Catalysis of solar hydrogen production by iron atoms on the surface of Fe-doped silicon carbide

Fe atoms located on the hydrated surface of SiC provide a 100-fold enhancement in the rate of photodriven H₂ evolution.

Carbon/Silicon Heterojunction Solar Cells: State of the Art and Prospects

In the last few decades, advances and breakthroughs of carbon materials have been witnessed in both scientific fundamentals and potential applications. The combination of carbon materials with traditional silicon semiconductors to fabricate solar cells has been a promising field of carbon science. The power conversion efficiency has reached 15-17% with an astonishing speed, and the diversity of systems stimulates interest in further research. Here, the historical development and state-of-the-art carbon/silicon heterojunction solar cells are covered. Firstly, the basic concept and mechanism of carbon/silicon solar cells are introduced with a specific focus on solar cells assembled with carbon nanotubes and graphene due to their unique structures and properties. Then, several key technologies with special electrical and optical designs are introduced to improve the cell performance, such as chemical doping, interface passivation, anti-reflection coatings, and textured surfaces. Finally, potential pathways and opportunities based on the carbon/silicon heterojunction are envisaged. The aspects discussed here may enable researchers to better understand the photovoltaic effect of carbon/silicon heterojunctions and to optimize the design of graphene-based photodevices for a wide range of applications.

Investigation of adsorption properties of CS2 on interior and exterior surfaces of single-walled silicon-carbide nanotubes and effect of applied electric field: electronic structure, charge density and NMR studies

The adsorption behavior of CS₂ on silicon-carbide nanotube has been investigated using B3LYP/6-31G*. 3D NBO contour plots illustrating the interaction between lone pair orbitals of S atom of CS₂ with σ*Si12–C13 of the nanotube in configuration 2.

Vibrational spectra and structures of SinC clusters (n = 3–8)

The geometries of C-doped silicon clusters determined from infrared spectroscopy and computational chemistry reveal the stable Si₃C unit as a common structural motif.

Stabilization of graphene nanopore

Graphene is an ultrathin, impervious membrane. The controlled introduction of nanoscale pores in graphene would lead to applications that involve water purification, chemical separation, and DNA sequencing. However, graphene nanopores are unstable against filling by carbon adatoms. Here, using aberration-corrected scanning transmission electron microscopy and density-functional calculations, we report that Si atoms stabilize graphene nanopores by bridging the dangling bonds around the perimeter of the hole. Si-passivated pores remain intact even under intense electron beam irradiation, and they were observed several months after the sample fabrication, demonstrating that these structures are intrinsically robust and stable against carbon filling. Theoretical calculations reveal the underlying mechanism for this stabilization effect: Si atoms bond strongly to the graphene edge, and their preference for tetrahedral coordination forces C adatoms to form dendrites sticking out of the graphene plane, instead of filling the nanopore. Our results provide a novel way to develop stable nanopores, which is a major step toward reliable graphene-based molecular translocation devices.

Rational design of carbon network cross-linked Si-SiC hollow nanosphere as anode of lithium-ion batteries

This study aims to realize controllable synthesis of Si-based nanostructures from common and easily accessible silica nanoparticles and to study their component/structure-dependent electrochemical performance as an anode of lithium-ion batteries (LIBs). To this end, a controllable route based on deliberate design has been developed to prepare hollow Si-based nanospheres with tunable composition and crystal structure at the nanoscale. The synthesis process started with coating silica nanoparticles with a carbonaceous polymer with a controllable thickness followed by magnesiothermic reduction. An Si-SiC-C composite was finally produced with a unique hollow sphere structure featuring Si-SiC nanoparticles encapsulated by a cross-linked carbon film network. In addition to the scalability of the synthetic route, the resulting composite exhibits a number of advantageous properties, including excellent electrical conductivity, highly accessible surfaces, structural coherence, and a favorable structure for the formation of a stable solid-electrolyte interphase, which makes it attractive and promising for advanced anode materials of LIBs.