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Abstract Amorphous carbon is a promising candidate as an energy storage material. In this paper, we performed an X-ray total scattering measurement, RMC modeling, and persistent homology analysis for amorphous carbon samples fabricated at two different heat treatment temperatures. According to the analysis of the nearest-neighbor carbon atoms and their angular histogram, the sample treated at higher temperature shows higher connectivity between carbon atoms than that treated at lower temperature. Furthermore, topological data analysis (persistent homology, PH) reveals quantitative results that relate ring structure and the connectivity between carbon atoms.

Abstract The study analyzes the black color factors of black-burnished pottery excavated from the Pungnap Fortress and the Seokchon Tomb during the Hanseong period of the Baekje Kingdom. The current hypothesis surrounding the pottery’s black color factors suggests the use of magnetite, manganese oxide, and carbon. To compare the results of the black pottery, red pottery was used as the control group. To identify these black color factors, each hypothesis was investigated using several spectroscopic techniques. However, it was difficult to detect sufficient magnetite and manganese oxide on the surface of the black pottery to account for its black color. In contrast, a larger amount of carbon was located on the surface and core of the black pottery compared to the red pottery. These results indicate that the black factors can be credibly attributed to carbon rather than to magnetite or manganese oxide. The firing temperature of the black-burnished pottery was estimated from the mineral composition based on X-ray diffraction, and the firing atmosphere was deduced from the redox conditions based on the reduction index from Mössbauer spectroscopy. In addition, seven pieces of pottery excavated from Gunsu-ri Temple Site and Buyeo Ancient Tomb from the Sabi period of Baekje were investigated and compared the five pieces of pottery from the Hanseong period. Although the results were based on a limited number of potteries, various firing temperatures and redox atmosphere for pottery from the Hanseong and Sabi periods were carefully proposed.

Abstract Copper (Cu) is widely used as an industrial electrode due to its high electrical conductivity, mechanical properties, and cost‐effectiveness. However, Cu is susceptible to corrosion, which degrades device performance over time. Although various methods (alloying, physical passivation, surface treatment, etc.) are introduced to address the corrosion issue, they can cause decreased conductivity or vertical insulation. Here, using the nitrogen‐doped amorphous carbon (a‐C:N) thin film is proposed as a substrate on which Cu is directly deposited. This simple method significantly inhibits corrosion of ultrathin Cu (

The poor dispersion stability and susceptibility to oxidation significantly restrict the practical application of MoS2 as a lubricant additive. Here, MoS2 nanocomposite powders with magnesium silicate hydroxide (MSH) reinforcement and amorphous carbon protection were prepared via a straightforward two-step procedure. Detailed studies of the structure, phase composition, tribological properties, and lubrication mechanism of the composite powder have been conducted. The results demonstrated that the morphology of the composite powders was rod-shaped MSH coated with amorphous carbon and layered MoS2. The introduction of amorphous carbon into the MSH/MoS2 composite powders results in enhanced dispersion and a reduction in corrosion to copper sheets. Furthermore, the addition of 1.0 wt% MSH/MoS2/C nanoparticles to PAO-6 led to a decrease in the COF of the lubricating oil from 0.104 to 0.063. Meanwhile, the wear rate of the friction pair decreased from 5.91 × 10−7 mm3 N−1 m−1 to 2.22 × 10−7 mm3 N−1 m−1. The excellent performance could be attributed to the introduction of amorphous carbon effectively prevents the oxidation of MoS2 within the additive, leading to improved friction and wear resistance. The tribo-film, composed of MSH, Fe2O3, FeS, MoS2, graphite, and amorphous carbon, demonstrates remarkable capabilities in reducing friction and wear.

In-situ transmission electron microscopy has evolved to be a unique technique to study process dynamics down to the atomic scale. Here, we show that in-situ Joule heating of carbon nanofilms facilitates the investigation of the nucleation, annealing, diffusion and evaporation of PtSi nanoparticles in a controlled way. The nanoparticles form from Pt-based hydrocarbon molecules and silicon oxide present on the amorphous carbon nanofilm. The in-situ transmission electron microscopy approach permits shedding light on the interaction between the nanoparticles and the carbon support, crucial information when aiming for stable catalytic applications. The method is versatile, allows reaching very high temperatures and could be applied to study many different combinations of bimetallic and even multimetallic high-entropy alloy nanoparticles.

Carbon-based materials strongly pertain to citizens’ daily life due to their versatile derivatives such as diamond, graphite, fullerenes, carbon nanotube, single-layer graphene, and amorphous carbon (a-C). Compared to other families, a-C exhibits reconfigurable electrical properties by triggering its sp2–sp3 transition and vice versa, which can be readily fabricated by conventional film deposition technologies. For above reasons, a-C has been adopted as a promising memristive material and has given birth to several physical and theoretical prototypes. To further help researchers comprehend the physics behind a-C-based memristors and push forward their development, here we first reviewed the classification of a-C-based materials associated with their respective electrical and thermal properties. Subsequently, several a-C -based memristors with different architectures were presented, followed by their respective memristive principles. We also elucidated the state-of-the-art modeling strategies of a-C memristors, and their practical applications on neuromorphic fields were also described. The possible scenarios to further mitigate the physical performances of a-C memristors were eventually discussed, and their future prospect to rival with other memristors was also envisioned.

Micro/nanoprocessing of materials using lasers is currently an active research topic. In that research, the choice of the laser to be used is critical, but the F2 laser, which has the shortest wavelength (157 nm) among commercially available lasers, has few research compared to its potential. In this paper, we discovered a new photochemical processing by using an F2 laser to irradiate an amorphous carbon thin film. The short wavelength and high photon energy of the F2 laser can photoexcite the surface of the thin film at high density and generate active oxygen atoms O(1D) by photodecomposition of atmospheric oxygen molecules. As a result, the optical change of the amorphous carbon thin film was induced without thickness reduction, and a micron-sized network-like, reticulated structural change was formed in the thin film surface after one month at the latest. The formed micron-sized reticulated structure was relatively swollen, and a graphitization occurred in the structure, observed by Raman spectroscopy. However, the structure was not observed when the laser irradiated area became smaller. This work has made it possible to form a micron-sized reticulated structure including carbon nanocrystals in an amorphous carbon, which is expected to further expand the applications of carbon materials.

With the widespread use of electronic devices, electromagnetic interference (EMI) has become an increasingly severe issue, adversely affecting device performance and human health. Carbon nanotubes (CNTs) are recognized for their electrical conductivity, flexibility, and stability, making them promising candidates for EMI shielding applications. This research developed hierarchical porous-structured CNT/carbon composites for enhancing electromagnetic interference (EMI) shielding properties. Featuring a CNT film with nano-scale pores and an amorphous carbon layer with micro-scale pores, the CNT/carbon composites are strategically arranged to promote the penetration of EM waves into the composite’s interior and facilitate multiple reflections, thereby improving the EMI shielding performance. An impressive EMI shielding effectiveness of 61.4 dB was achieved by the CNT/carbon composites, marking a significant improvement over the 36.5 dB measured for the pristine CNT film. Owing to the micro pores in the amorphous carbon layer, a notable reduction in the reflection shielding efficiency (SER) but, concurrently, a substantial increase in the absorption shielding efficiency (SEA) compared with the pristine CNT film was realized in the composites. This study successfully validated the effectiveness of the hierarchical porous structure in enhancing the EMI shielding performance, providing a promising new strategy for the development of lightweight, flexible, and efficient EMI shielding materials.

Abstract The work is dedicated to revealing the structural features of coals with different ranks, such as anthracites, metaanthracite and graphite, that determine their ability to crush and form fine dust. For this purpose, a combination of various nanoindentation techniques and Raman spectroscopy was used. The mechanical behavior of the selected coals was investigated by cyclic nanoindentation with increasing peak load and quasi-static loading. The alteration of the mechanical properties was studied by analysis of elastic moduli and damage indices R w. Three groups of coals were identified based on their propensity to crushing during cyclic nanoindentation. Coals assigned to the first and second groups are characterized by local destruction in the contact zone with the indenter and the formation of a core of crushed material. Coals assigned to the third group are characterized by bulk destruction (outside the zone of contact with the indenter). In general, the ability of coals to fracture under mechanical loading decreases in the series of metamorphism due to microscale compaction of vitrinite matter. In the series of anthracite, metaanthracite and graphite, it is established that the coal matter compaction takes place for the anthracite and metaanthracite, whereas graphite reveals rather different behavior due to abrupt change of its structure. The ratios between the amorphous and crystalline phases of carbon (S) were determined by deconvolution of coals Raman spectra. The propensity of coals to crushing (a damage index R w) increases with growth of the proportion of amorphous carbon in the coal matter. For the considered coals and metaanthracite, it is established that the proneness to destruction outside the contact zone with the indenter is determined by the ratio of amorphous and crystalline carbon of 1 and higher. When S parameter is lower than 1, the coals are being crushed only in the zone of contact with the indenter.

Compared with hydrogen evolution reaction (HER) under acidic conditions, the kinetic steps of alkaline HER are more complex, which involves the adsorption and cleavage of water molecules. Defect and interface engineering are two important means to enhance basic HER. In order to prepare catalysts with high activity and stability under both acidic and basic conditions, a defective amorphous carbon loaded with Ru nanoparticles coaxially wrapped around a carbon nanotube (CNT) sponge network is presented. The presence of amorphous carbon can promote the uniform loading of Ru nanoparticles and limit the growth of Ru nanoparticles, and also the introduction of oxygen defects can regulate the electronic structure of the metal and improve its charge transport capacity, thus enhancing the catalytic performance. The catalyst CNT/C/Ru0.37 wt%‐700 prepared under optimized conditions exhibits excellent stability and activity. At a current density of 10 mA cm−2, the overpotential of HER is as low as 38.3 and 36.2 mV under alkaline and acidic conditions, respectively, which is better than most reported Ru‐based catalysts. This study details innovative and feasible ideas for the design and preparation of loaded catalysts, which can contribute to the development of high‐performance electrochemical catalysts.

Efficient solar thermal conversion is crucial for renewable clean energy technologies such as solar thermal power generation, solar thermophotovoltaic and seawater desalination. To maximize solar energy conversion efficiency, a solar selective absorber with tailored absorption properties designed for solar applications is indispensable. In this study, we propose a broadband selective absorber based on amorphous carbon (a-C) metamaterials that achieves high absorption in the ultraviolet (UV), visible (Vis) and near-infrared (NIR) spectral ranges. Additionally, through metal doping, the optical properties of carbon matrix materials can be modulated. We introduce Ti@a-C thin film into the nanostructure to enhance light absorption across most of the solar spectrum, particularly in the NIR wavelength band, which is essential for improving energy utilization. The impressive solar absorptivity and photothermal conversion efficiency reach 97.8% and 95.6%, respectively. Notably, these superior performances are well-maintained even at large incident angles with different polarized states. These findings open new avenues for the application of a-C matrix materials, especially in fields related to solar energy harvesting.

All-carbon photovoltaic devices have attracted attention in terms of resources and environment. However, the device application is very limited because of poor performance. In this work, we studied the solar cell characteristics of amorphous carbon (a–C)/fullerene (C60) junction when the thickness of the a–C layer was varied. When the thickness of the a–C layer was varied, the short-circuit current density and open-circuit voltage increased with increasing film thickness and then decreased after a certain value. Also, the spectral response measurement results suggest that most of the power generation is due to the light absorbed by the C60 layer, and that the light absorbed by the a–C layer may contribute little to power generation. This study suggests that the improvement in the electronic properties of a–C is necessary to make a photovoltaic device with high performance.

In this paper, the feasibility of employing amorphous carbon powder as a viable degradation inhibitor for cement mortars made with siliceous aggregates was investigated. Amorphous carbon powder is a by-product of the paraffin industry and was replaced by 0, 4, 6 and 8% of aggregate. Mechanical strength, rheology and water absorption were analyzed considering three common physical factors of concrete namely strength, workability and durability. Mechanical properties of mixtures were obtained using flexural and compressive strengths and rheological attributes were collected through flow table test. Results revealed that adding amorphous carbon powder to the bulk cement mortar could enhance the strength and durability of cement mortar. Replacing 8 wt.% of siliceous aggregate dust filler by amorphous carbon powder caused an increment about twofold in the 28-day compressive strength and reduction of the flow table results by about 20% compared to those of the control mixture. Moreover, hydrophobicity and impermeability properties of amorphous carbon -modified cement mortars, resulted in reduced moisture susceptibility.

Abstract In this paper, X-ray diffraction spectroscopy (XRD), Raman spectroscopy (RS), firing temperature analysis, pore size distribution analysis, Fourier infrared spectroscopy (FTIR), scanning electron microscopy-energy dispersive spectroscopy (SEM–EDS), and transmission electron microscopy (TEM) were utilized to analyze the unearthed vulnerable terracotta figures of Emperor Qin Shihuang's Terracotta Army, as well as the unknown precipitated white crystals and black substances. The results show that the firing temperature of the vulnerable terracotta figure is much lower than those of similar terracotta figures and red terracotta figures with good texture. The pore size of this kind of vulnerable pottery is smaller and the specific surface area is larger. In the pores, there is an alkaline solution containing Ca2+ that accounted for approximately 4.3% of the total mass of the sample. Along with the fracture of the delicate pottery matrix, the solution in the pores migrated to the fracture surface and chemically reacted with CO2 in the air, generating a layer of white calcium carbonate crust. The black matter on the fracture surface of the vulnerable terracotta figure is mainly composed of amorphous carbon and graphitized carbon, which shows high activity under the catalysis of Fe and Ti elements and alkaline soil. The discovery and analysis of amorphous carbon, graphitized carbon, and white calcium carbonate crystals on the fracture surface of the Qin Shihuang’s Terracotta Army provide a theoretical foundation for in-depth analysis of the terracotta warriors and horses' composition and structure, as well as scientific protection and restoration, and the stability of the original site display.

Spectroscopy techniques such as x-ray absorption near edge structure (XANES) provide valuable insights into the atomic structures of materials, yet the inverse prediction of precise structures from spectroscopic data remains a formidable challenge. In this study, we introduce a framework that combines generative artificial intelligence models with XANES spectroscopy to predict three-dimensional atomic structures of disordered systems, using amorphous carbon ( a -C) as a model system. In this work, we introduce a new framework based on the diffusion model, a recent generative machine learning method, to predict 3D structures of disordered materials from a target property. For demonstration, we apply the model to identify the atomic structures of a -C as a representative material system from the target XANES spectra. We show that conditional generation guided by XANES spectra reproduces key features of the target structures. Furthermore, we show that our model can steer the generative process to tailor atomic arrangements for a specific XANES spectrum. Finally, our generative model exhibits a remarkable scale-agnostic property, thereby enabling generation of realistic, large-scale structures through learning from a small-scale dataset (i.e. with small unit cells). Our work represents a significant stride in bridging the gap between materials characterization and atomic structure determination; in addition, it can be leveraged for materials discovery in exploring various material properties as targeted.

Abstract Graphite has been used in a wide range of applications since the discovery due to its great chemical stability, excellent electrical conductivity, availability, and ease of processing. However, the synthesis of graphite materials still remains energy‐intensive as they are usually produced through a high‐temperature treatment (>3000°C). Herein, we introduce a molten salt electrochemical approach utilizing carbon dioxide (CO2) or amorphous carbons as raw precursors for graphite synthesis. With the assistance of molten salts, the processes can be conducted at moderate temperatures (700–850°C). The mechanisms of the electrochemical conversion of CO2 and amorphous carbons into graphitic materials are presented. Furthermore, the factors that affect the graphitization degree of the prepared graphitic products, such as molten salt composition, working temperature, cell voltage, additives, and electrodes, are discussed. The energy storage applications of these graphitic carbons in batteries and supercapacitors are also summarized. Moreover, the energy consumption and cost estimation of the processes are reviewed, which provides perspectives on the large‐scale synthesis of graphitic carbons using this molten salt electrochemical strategy.

In this study, the amorphous carbon thin films were deposited by ion beam sputtering deposition method on the glass and Ni–Cu alloy substrates. The structural evolution of amorphous carbon and its correlation with the kinetic energy of carbon atoms during the growth of thin film was investigated. The effect of substrate material, deposition temperature, and ion beam energy on the structural changes were examined. Raman spectroscopy indicated a structural transition from amorphous carbon to diamond-like amorphous carbon (DLC) due to an increase in deposition temperature up to 100°C and ion beam energy from 2 keV to 5 keV. The size of graphite crystallites with sp2 bonds (La) were smaller than 1 nm in the amorphous carbon layers deposited on Ni-Cu alloy. The results of residual stress calculation using X-ray diffractometer (XRD) analysis revealed a decreasing trend in the tensile residual stress values of the amorphous carbon thin films with increasing the ion beam energy.

Abstract The formation of a fissured copper surface by picosecond pulsed laser irradiation is combined with functional coatings consisting of Ti and amorphous carbon layers or a Ti–Zr–V compound film to fabricate surfaces with the maximum of the secondary electron yield being as low as 0.4. By structural and spectroscopic analysis of the formed surfaces it is demonstrated that both coatings enclose the nanostructures generated by redeposition of metal structures from the laser‐induced plasma plume, keeping the initial topography intact. This allows an efficient elimination of secondary electron emission by combining the benefits from structural surface modification and adaption of electronic surface properties to efficiently dissipate the energy of impinging electrons. Thermal activation tests of the Ti–Zr–V nonevaporable getter films revealed that for films on nanostructured substrates, which have a much higher effective surface, a slight diminution of surface activation occurs at 160 and 200 °C, while this effect is completely compensated when heating up to 250 °C indicating promising pumping capabilities. Both examples highlight the benefits from combining 3D substrate patterning with classical 2D deposition technologies.

The improved mechanical properties of carbon-doped TiZrN coatings were investigated in terms of the microstructure and bonding state. The carbon incorporation and structural change were confirmed as a shift to lower degree of the diffraction pattern and the decreased grain size from 24.64 to 22.19 nm. The clear grain boundaries (GBs) were observed in the carbon-doped coating, and its fast Fourier transform (FFT) exhibited a diffused ring pattern. Edge dislocations were also observed in the inverse FFT image, indicating the formation of an amorphous phase due to laser carburization. From the X-ray photoelectron spectroscopy depth profile analysis, the carbon concentration decreased to 37.26 at.% after carburization, which is non-stoichiometric behavior that suggests the formation of the amorphous carbon (a-C) rather than carbides. Both sp2- and sp3-hybridized bonds were detected in the C 1s spectrum of the carbon-doped coating, indicating that the diffused carbon atoms were trapped in the GBs as a-C. The change in the GB structure increased the compressive residual stress from 3.97 to 4.63 GPa. In addition, the hardness, elastic strain to failure (H/E), and plastic deformation resistance (H3/E2) of the carbon-doped TiZrN increased by 19.22%, 12.64%, and 49.59%, respectively, demonstrating the effect of GB strengthening.

While graphene has held the center stage in nanocarbon material research since its isolation in 2004, less attention has been paid to nanometer-thick carbon films in which at least part of the carbon atoms are sp3-hybridized, whatever the crystallographic structure. However, because of their composition, structure, physical and chemical properties, those nanomaterials exhibit competitive features that should be considered for the development of future sustainable technologies based on 2D materials. The purpose of this review is to provide a snapshot of the main advances in the synthesis of sub-10 nm thick sp3-C-rich films, which include amorphous carbon hydrogenated or not, nanocrystalline diamond films, graphane, diamanes and diamanoids. Physical properties and applications (i.e. existing or potential) are also highlighted.

Carbon nanotube (CNT)-reinforced composites are promising materials for high-performance, lightweight structures; however, homogeneous infiltration of CNTs by a matrix material is necessary to achieve desired mechanical properties. Critical to overcoming this challenge at scale is purification of CNT materials produced by floating-catalyst chemical vapor deposition. Here, we present a hydrothermal processing technique for purification of CNT yarns, wherein as-received material is exposed to superheated, subcritical water in a hydrothermal reactor. This process selectively removes amorphous carbon and acid impurities while preserving the yarn structure. We find this technique to be consistent and tunable, with processing time directly correlating to linear density reduction up to a saturation limit. Using commercially-available yarns, we find that after 4 h of treatment at 200 °C, the weight loss of the yarn under inert atmosphere is reduced from 12% to 5%, the atomic percentage of oxygen at the surface by 42%, and the ID/IG by 30%. In addition, the yarn specific strength (1.3 N/tex) is preserved, while the specific Young's modulus is significantly increased by 20% (79 to 95 N/tex). At longer treatment times, we obtain greater purity and higher specific Young's modulus, but at a substantial reduction in tensile strength, which we hypothesize results from eliminating amorphous carbon toughening CNT bundles. The reported method could be scaled to continuous processing in tandem with post-purification treatments, and appears broadly applicable to different continuous CNT networks.

In low-temperature carbonization stage, stabilized polyacrylonitrile (PAN) fibers are pyrolyzed and recombined to transform into low-temperature carbonized fiber with rudiment of turbostratic graphite structure. The temperature regulation of low-temperature carbonization has an important influence on the structure and performance of the final carbon fibers. The reaction process of stabilized fiber during low-temperature carbonization stage, the effect of the regulation of low-temperature carbonization temperature gradient on the structural evolution of stabilized fiber and the structure and performance of carbon fiber were studied through 13C-NMR, Raman, XRD and mechanical property analysis. The results indicate that: in the process of low-temperature carbonization heat treatment of stabilized fiber, the carbon structure shows the degree of branched chain reaches a maximum of 0.99, after heat treatment at 450 ℃. When the heat treatment temperature reaches 550 ℃, the main reaction is the recombination crosslinking reaction of stabilized fiber’s aromatic chain segments. The low-temperature carbonization temperature gradients affect the structural evolution of stabilized fibers. When the temperature gradient is 350-450-650 ℃, the 13C-NMR shift of the —C C group in the low carbon fiber treated at 450 ℃ is the largest, the branching crosslinking reactions in fiber are the most, causing the d002 of the low carbon fiber treated at 650 ℃ and the IA/IG of the corresponding high-temperature carbon fiber are the largest, the relative content of amorphous carbon is the largest and the mechanical properties of the final carbon fiber are the worst. However, when the temperature gradient is 350-550-650 ℃, the cracking and recombination crosslinking reaction in fiber are carried out in an orderly manner, resulting in the structure of low-temperature carbonized fiber and carbon fiber more perfect, and the density and mechanical properties of carbon fiber are improved.

In order to explore the lubrication performance of alcohols under high loads and high speeds conditions, especially the relationship between carbon-chain length and hydroxyl number and lubrication performance, the effects of carbon-chain length and hydroxyl number on the lubrication performance were well studied. The tribological properties of a series of alcohols were investigated by a four-ball tribological machine, and the effects of the carbon-chain length and the hydroxyl number on their lubricating properties were investigated by means of viscometer, transmission electron microscopy (TEM) and Raman. Experiments show that with the increasing of the carbon-chain length, the run-in period and the time for achieving stable friction coefficient were shorted, and the wear was reduced; with the increasing of the hydroxyl number, the wear decreased with no obvious run-in period and consistent fluctuation of friction coefficient for ethylene glycol and continuous decrease of friction coefficient for glycerol. It is found that friction-induced graphene is superior to amorphous carbon in effectively promoting the tribosystem to achieve the stable friction coefficient and shorten run-in period, which provides reference for the application of alcohols in the field of mechanical equipment.

Knudsen flow experiments and its interpretation in terms of adsorption/desorption kinetics as well as quantitative uptake on substrates of interest is presented together with the description of critical design parameters of the Knudsen Flow Reactor (KFR). Hitherto focused almost exclusively on the uptake phase exposing a virgin substrate to interacting gases, we now extend the experiment and its interpretation to the desorption phase at ambient temperature. We present analytical expressions for different experimental situations in terms of adsorption (ka), desorption (kd) and effusion (ke) rate constants. The measurement of kd leads to surface residence times (1/kd) obtained under the same experimental conditions as the uptake (ka) that results in the determination of the Langmuir equilibrium constant KL = ka/kd. We emphasize the interaction of semivolatile organic probe gases and small polar molecules with amorphous carbon and mineral dust materials at ambient temperatures. The latter leads to a molecular characterization scheme based on the use of up to ten different reactive probe gases. After saturation of the uptake of each probe gas this results in a reactivity map of the interface. Several examples are used to underline the broad applicability of the technique such as the silver/air (Ag) interface and the reactivity of TiO2 materials towards uptake of CO2 and CH3OH. Following characterization of several types of amorphous carbon a model incorporating several structural elements in agreement with the reactive gas titration is proposed. For instance, an interface that is at the same time weakly basic and strongly reducing is composed of pyrones and hydroquinones whose simultaneous occurrence leads to stable free radicals that may play a role in atmospheric chemistry (EPFR). The question is raised what makes an interface hydrophobic in terms of surface functional groups when interacting with small polar molecules such as H2O(D2O), HCl, NO2 and NH2OH. Multidiagnostic studies of heterogeneous reactions are enabled using stirred-flow reactors (SRF) that are a logical extension of the KFR approach thus relaxing the Knudsen flow requirements. Previous work using SRF on low-temperature substrates such as H2O ices is highlighted that may be of interest to the exoplanetary and space sciences community.

Abstract Crystalline Fe/MnO@C core–shell nanocapsules inlaid in porous amorphous carbon matrix (FMCA) was synthesized successfully with a novel confinement strategy. The heterogeneous Fe/MnO nanocrystals are with approximate single-domain size which gives rise to natural resonance in 2–18 GHz. The addition of MnO2 confines degree of graphitization catalyzed by iron and contributes to the formation of amorphous carbon. The heterogeneous materials composed of crystalline–amorphous structures disperse evenly and its density is significantly reduced on account of porous properties. Meanwhile, adjustable dielectric loss is achieved by interrupting Fe core aggregation and stacking graphene conductive network. The dielectric loss synergistically with magnetic loss endows the FMCA enhanced absorption. The optimal reflection loss (RL) is up to − 45 dB, and the effective bandwidth (RL

Nanoporous materials show a promising combination of mechanical properties in terms of their relative density; while there are numerous studies based on metallic nanoporous materials, here we focus on amorphous carbon with a bicontinuous nanoporous structure as an alternative to control the mechanical properties for the function of filament composition.Using atomistic simulations, we study the mechanical response of nanoporous amorphous carbon with 50% porosity, with sp3 content ranging from 10% to 50%. Our results show an unusually high strength between 10 and 20 GPa as a function of the %sp3 content. We present an analytical analysis derived from the Gibson–Ashby model for porous solids, and from the He and Thorpe theory for covalent solids to describe Young’s modulus and yield strength scaling laws extremely well, revealing also that the high strength is mainly due to the presence of sp3 bonding. Alternatively, we also find two distinct fracture modes: for low %sp3 samples, we observe a ductile-type behavior, while high %sp3 leads to brittle-type behavior due to high high shear strain clusters driving the carbon bond breaking that finally promotes the filament fracture. All in all, nanoporous amorphous carbon with bicontinuous structure is presented as a lightweight material with a tunable elasto-plastic response in terms of porosity and sp3 bonding, resulting in a material with a broad range of possible combinations of mechanical properties.

The objective of this investigation was to determine the efficiency of carbonaceous material, consisting of MWCNTs and amorphous carbon obtained by waste polyethylene pyrolysis, as an adsorbent for reactive textile dyes. In this work, the preliminary results of adsorption process of Bezaktiv Blau V-3R reactive dye from a solution with an initial 30 mg/l concentration using low dosage of adsorbent are presented. The results show that this material has promising potential as a sorbent, and its adsorption capacity (140 mg/g) for a reactive (anionic) dye is similar to some commercial MWCNT and functionalized MWCNT-based adsorbents.

Generation of hydrogen fuel at cathode during the electrolysis of seawater can be economically beneficial considering the vast availability of the electrolyte although it faces sluggishness caused by the anode reactions. In this regard a carbon nanosphere-protected CuO/Co3O4 (CCuU) composite was synthesized through heat treatment and was used as the cathode material for electrocatalytic seawater splitting. CCuU showed a significantly low overpotential of 73 mV@10 mA cm−2, Tafel slope of 58 mV dec−1 and relatively constant activity and morphology over a long time electrocatalytic study. A synergy within metal oxide centers was observed that boosted the proton-electron transfer at the active site. Moreover, the presence of carbon support increased the electroactive surface area and stability of the composite. The activity of the CCuU was studied for HER in KOH and alkaline NaCl solution to understand the activity. This work will pave the way for designing mesoporous non-precious electrocatalysts towards seawater electrocatalysis.

Nanostructured coatings based on amorphous carbon and carbon-doped with gold, silver, and nitrogen were obtained by the pulsed vacuum-arc method. Carbon coatings have been annealed in a vacuum as well as treated with argon ions. The alloying of carbon coatings with elements that do not form chemical bonds with the carbon matrix (Ag, Au) leads to the formation of gold or silver nanocrystallites with sizes of 2 ‑ 20 nm in the matrix of amorphous carbon, whose density depends on the concentration of the doping element. Annealing of silver-doped carbon coatings leads to the formation of islands on the surface with the size of the order of micrometers. This is due to the silver diffusion and coalescence of small islands into larger ones. The HRTEM method discovered the effect of twinning in carbon nanocrystallites after vacuum annealing as well as silver and gold in the initial state (the formation of single-crystal regions with an altered orientation of the crystal structure) in the amorphous carbon matrix. Analysis of Raman spectra of pure carbon coating and silver-doped showed that the addition of silver leads to a decrease in sp3-phase in the carbon matrix. This effect is particularly evident in the nature of changes in the spectra after vacuum annealing at 600 ºC. The addition of nitrogen in the carbon coating leads to an increase in the sp2 ‑ phase fraction, and additional annealing leads to a significant increase in the D - peak intensity and formation of clusters of the order of 5 ‑ 15 nm, which are not localized but fill the entire space. Analysis of the coating a-C: Au irradiation with argon ions shows that the number of nanopitches decreased after ion irradiation, simultaneously decreased surface roughness degree, besides, decreased electrical conductivity of the coating as a result of decreased gold content. It was found that the conditions of nanostructured coatings and their subsequent processing allow controlling the properties of nanocoatings (structure, size of nanoparticles, surface topography, and electrical conductivity).

Summary: New carbon forms that exhibit extraordinary physicochemical properties can be generated from nanostructured precursors under extreme pressure. Nevertheless, synthesis of such fascinating materials is often not well understood. That is the case of the C60 precursor, with irreproducible results that impede further progress in the materials design. Here, the semiconducting amorphous carbon, having band gaps of 0.1–0.3 eV and the advantages of isotropic superhardness and superior toughness over single-crystal diamond and inorganic glasses, is produced from fullerene at high pressure and moderate temperatures. A systematic investigation of the structure and bonding evolution is carried out with complementary characterization methods, which helps to build a model of the transformation that can be used in further high-pressure/high-temperature (high p,T) synthesis of novel nano-carbon systems for advanced applications. The amorphous carbon materials produced have the potential of accomplishing the demanding optoelectronic applications that diamond and graphene cannot achieve.

Designing the film architecture of amorphous carbon based systems is effective in tailoring the tribo-mechanical properties. For this purpose, alternating a-C and a-C:X layers, with X = Si or W, were grown with a layer ratio of 1, a bilayer period of ~200 nm, and a bilayers number of 5 in a magnetron sputtering process. By comparing with a-C(:X) monolayers, the structure and tribo-mechanical properties of alternating a-C/a-C:X films were evaluated.Although the bonding state of the a-C network of a-C:X in a-C/a-C:X is comparable to monolayered a-C:X, the multilayer design significantly affects the tribo-mechanical properties. The a-C/a-C:X multilayers exhibit a higher hardness compared to a-C:X. With a coefficient of friction of 0.12 ± 0.01, a-C/a-C:Si shows a low friction as a-C:Si with 0.09 ± 0.01, but the wear rate is significantly lower for a-C/a-C:Si with (3.4 ± 0.7) × 10-7 mm³/Nm than a-C:Si with (8.3 ± 1.0) × 10-7 mm³/Nm. Contrarily, a-C/a-C:W and a-C:W provide similar wear rates of 1.2 to 1.4 × 10-7 mm³/Nm, but the coefficient of friction is lower for a-C/a-C:W with 0.29 ± 0.02 than a-C:W with 0.36 ± 0.01. Hence, the multilayer design is efficient in improving the tribo-mechanical properties of a-C:X based films.

The amorphous carbon-based resistive memory has recently attained vast attention due to its non-volatility, fast switching speed, long data retention, and multilevel recording. However, the memory switching mechanism of amorphous carbon media remains mysterious and thus severely restricted its application prospect. To resolve this issue, a comprehensive three-dimensional model by simultaneously solving the current continuity equation, heat transfer equation, and mass concentration equation, is developed to model the physical conversions between sp2 and sp3 clusters. According to simulations, electric field was considered as the sole critical factor that determines the formation of conductive sp2 filament during the `SET' process, whereas the `RESET' process is mainly attributed to the induced high temperature that accelerates the growth of sp3 cluster and causes the rupture of the sp2 filament. It was additionally found that the sp2 filament was preferably formed inside the region having larger sp2 concentrations, and its rupture usually initiates from the filament center. The threshold voltages of carbon resistive memory for different thickness and different sp2 fractions were also calculated and exhibited good agreement with experimental measurements.

Amorphous and graphitized nitrogen-doped (N-doped) carbon spheres are investigated as structurally well-defined model systems to gain a deeper understanding of the relationship between synthesis, structure, and their activity in the oxygen reduction reaction (ORR). N-doped carbon spheres were synthesized by hydrothermal treatment of a glucose solution yielding carbon spheres with sizes of 330 ± 50 nm, followed by nitrogen doping via heat treatment in ammonia atmosphere. The influence of a) varying the nitrogen doping temperature (550–1000 °C) and b) of a catalytic graphitization prior to nitrogen doping on the carbon sphere morphology, structure, elemental composition, N bonding configuration as well as porosity is investigated in detail. For the N-doped carbon spheres, the maximum nitrogen content was found at a doping temperature of 700 °C, with a decrease of the N content for higher temperatures. The overall nitrogen content of the graphitized N-doped carbon spheres is lower than that of the amorphous carbon spheres, however, also the microporosity decreases strongly with graphitization. Comparison with the electrocatalytic behavior in the ORR shows that in addition to the N-doping, the microporosity of the materials is critical for an efficient ORR.

Background: Electron-beam shaping opens up the possibility for novel imaging techniques in scanning (transmission) electron microscopy (S(T)EM). Phase-modulating thin-film devices (phase masks) made of amorphous silicon nitride are commonly used to generate a wide range of different beam shapes. An additional conductive layer on such a device is required to avoid charging under electron-beam irradiation, which induces unwanted scattering events.Results: Phase masks of conductive amorphous carbon (aC) were successfully fabricated with optical lithography and focused ion beam milling. Analysis by TEM shows the successful generation of Bessel and vortex beams. No charging or degradation of the aC phase masks was observed.Conclusion: Amorphous carbon can be used as an alternative to silicon nitride for phase masks at the expense of a more complex fabrication process. The quality of arbitrary beam shapes could benefit from the application of phase masks made of amorphous C.

The thermal conductivity of nanostructures can be obtained using atomistic classical Molecular Dynamics (MD) simulations, particularly for semiconductors where there is no significant contribution from electrons to thermal conduction. In this work, we obtain and analyze the thermal conductivity of amorphous carbon (aC) nanowires (NW) with a 2 nm radius and aC nanotubes (NT) with 0.5, 1 and 1.3 nm internal radii and a 2 nm external radius. The behavior of thermal conductivity with internal radii, temperature and density (related to different levels of sp3 hybridization), is compared with experimental results from the literature. Reasonable agreement is found between our modeling results and the experiments for aC films. In addition, in our simulations, the bulk conductivity is lower than the NW conductivity, which in turn is lower than the NT conductivity. NTs thermal conductivity can be tailored as a function of the wall thickness, which surprisingly increases when the wall thickness decreases. While the vibrational density of states (VDOS) is similar for bulk, NW and NT, the elastic modulus is sensitive to the geometrical parameters, which can explain the enhanced thermal conductivity observed for the simulated nanostructures.

Background Multi-walled carbon nanotubes (MWCNTs) are nanoparticles with countless applications. MWCNTs are typically of synthetic origin. However, recently, the formation of MWCNTs in nature after forest fires has been documented. Previous reports have demonstrated the positive effects of synthetic MWCNTs on the germination and development of species of agronomic interest; nevertheless, there is practically no information on how synthetic or natural MWCNTs affect forest plant development. In this report, based on insights from dose-response assays, we elucidate the comparative effects of synthetic MWCNTs, amorphous carbon, and natural MWCNTs obtained after a forest fire on Eysenhardtia polystachya plant. Methods E. polystachya seeds were sown in peat moss-agrolite substrate and conserved in a shade house. Germination was recorded daily up to 17 days after sowing, and plant development (manifested in shoot and root length, stem diameter, foliar area, and root architecture parameters) was recorded 60 days after sowing. Results The treatments with natural MWCNTs accelerated the emergence and improved the germination of this plant, thus while untreated seeds achieve 100% of germination within 16th day, seeds supplemented with natural MWCNTs at doses of 20 µg/mL achieve the above percentage within the 4th day. Natural MWCNTs also promoted fresh and dry biomass in all applied treatments, specially at doses of 40 µg/mL where natural MWCNTs significantly promoted leaf number, root growth, and the dry and fresh weights of shoots and roots of seedlings. Seeds supplemented with doses between 20 and 40 µg/mL of amorphous carbon achieving 100% of germination within the 6th day; however, seeds supplemented either with doses of 60 µg/mL of the above carbon or with synthetic MWCNTs at all the tested concentrations could achieve at most 80 % and 70% of germination respectively within the 17 days. Finally, neither treatments added with amorphous carbon nor those added with synthetic MWCNTs, showed significant increases in the fresh and dry biomass of the tested plant. Likewise, the survival of seedlings was reduced between 10 and 20 % with 40 and 60 µg/mL of amorphous carbon, and with synthetic MWCNTs in all the doses applied was reduced at 30% of survival plants. Conclusions These findings indicate that MWCNTs produced by wildfire act as plant growth promoters, contributing to the germination and development of adapted to fire-prone conditions species such as E. polystachya.

We demonstrated an effective approach to suppress conductive filament (CF) overgrowth through the introduction of a AgInSbTe (AIST) buffer layer into amorphous carbon-based electrochemical metallization memory devices. The overshoot current (IOS) was monitored in real-time for the devices with and without the AIST layer. Our results indicates that the IOS was eliminated after insertion of the buffer layer. The effect of the AIST layer on CF overgrowth suppression could be attributed to the lower VSET and capacity to hold excess Ag-ions. The optimized Pt/a-C/AIST/Ag devices exhibited highly uniform switching parameters, fast switching speed (6 cycles).

Raman spectroscopy has been widely used in micropaleontology and organic geochemistry to identify carbonaceous materials and evaluate their thermal maturity in fossils or metasedimentary rocks. Meanwhile, fossil egg researches have mostly focused on biomineralized calcite, but preserved carbonaceous (or possibly organic) materials inside the eggshells have been usually neglected until recently. Here we report an enigmatic egg from the Wido Volcanics (Upper Cretaceous) of South Korea that was analyzed using diverse methods including polarized light microscope, scanning electron microscope, electron probe microanalyzer, electron backscatter diffraction, and Raman spectroscopy. The eggshell not only shows the crystallography of archosaurian eggshells but also contains peculiar dark bands, which were previously known as the trait of fossil and modern Crocodyliformes eggshells. Raman spectroscopic analysis showed that the dark bands are mainly due to amorphous carbon, as evidenced by the clear graphite (G) and disordered (D) bands. The deconvolution of amorphous carbon peaks and resultant parameters made it possible to infer the paleotemperature inscribed in the eggshell. The result suggests that preserved amorphous carbon in the fossil eggshells can be identified using Raman spectroscopy and Raman parameters may make it possible to compare the thermal maturity of spatiotemporally diverse fossil eggshells. The biogenicity of the dark band is not clear because Raman spectroscopic analysis is not sufficient to confirm biogenicity. However, overall distribution of the dark band may imply the biogenic origin. It is apparent that the material of this study is not a dinosaur egg but might belong to a crocodyliform or choristoderan egg, and even other non-dinosaur archosaur can be a candidate as well.

The facile preparation of polymer waste-derived microporous carbon microspheres (SBET ~800 m2/g) 100–300 μm in size, is reported at first. We have taken advantage of both, the crosslinked nature and the porous texture of the poly(4-ethylstyrene-co-divinylbenzene) microspheres, which allow the incoming anions and cations present in liquid media to enter and to remain segregated into the pores of the polymer microspheres as soon as the solvent is removed. Interestingly, the ZnCl2 phase, when incorporated in the microporous molecular architecture of the polymer, prevents the collapsing of the pore structure of thermosetting polymer spheres during the pyrolysis occurring at 800°C and acts as an activating agent of the carbon phase under formation, being responsible for the formation of an extended meso- and macroporosity (30–200 and 300–1,000 Å ranges). More interestingly, porous carbon microspheres with magnetic properties have been prepared from the ZnCl2-activated porous carbon spheres after impregnation with Fe nitrate solution and thermal treatment at 800°C. A multi-technique methodology to characterize more extensively carbons at the micro/nanoscale is reported in the paper. More in detail, the morphology, structure, porous texture, and the surface properties of the carbon and of the magnetic carbon microspheres have been investigated by scanning and transmission electron microscopy, atomic force microscopy, X-ray diffraction, N2 physisorption, diffuse reflectance UV-Vis, Raman and infrared spectroscopies. Furthermore, magnetic properties have been revealed at the nano- and at the macroscale by magnetic force microscopy and simple magnetically guided experiments by permanent magnets. The multi-technique methodology presented in the paper allows in elucidating more extensively about the different characteristics of activated carbons. Notwithstanding the huge amount of literature on activated carbons, the precise control of both the structure and the surface has, for the most part, hidden the relevance of other properties at the molecular scale of the assembled architectures. On the other hand, recent studies indicate that by molecular design, nanostructured, and porous carbonaceous materials could also be rationally proposed.

Carbon-doped TiZrN nanocomposite coatings were investigated for phase formation and wear behavior. They were prepared by laser carburization using carbon paste, and the thermal energy of the pulsed laser was limited to the range of 20 to 50%. X-ray photoelectron spectroscopy analysis revealed that the ratio of carbide (TiC, ZrC) increased as the thermal energy of the laser increased. The sp2/sp3 ratio increased by approximately 16% when the laser thermal energy was raised from 30 to 40%, and the formation of amorphous carbon was confirmed in the carbon-doped TiZrN coatings. As a result of microstructural analysis, the carbon-doped TiZrN nanocomposite was formed by an increase of hybrid bonds in expanded localized carbon clusters. Wear resistance was evaluated using a ball-on-disc tester, which showed that the friction coefficient decreased from 0.74 to 0.11 and the wear rate decreased from 7.63 × 10−6 mm3 (Nm)−1 to 1.26 × 10−6 mm3 (Nm)−1. In particular, the friction coefficient and wear rate improved by 71 and 66%, respectively, owing to the formation of carbon-doped TiZrN nanocomposite with amorphous carbon while the thermal energy was increased from 30 to 40%.

Quick characterization methods to determine the structure of carbon materials are sought after for a wide array of technical applications. In this study we present the combined analysis of the structure of carbide-derived carbons (CDCs) with Raman spectroscopy and wide-angle X-ray scattering (WAXS) methods. We present the optimal deconvolution method to be used for the detailed analysis of Raman spectroscopy data of CDCs and comparison to corresponding WAXS results is made. For a broad set of CDCs both WAXS and Raman spectroscopy data showed that the average graphene layer extent increases with synthesis temperature of CDC, while the coherent domain lengths obtained from Raman spectroscopy higher by an average of 4.4 nm. In addition, the presence of correlations between the parameters (D-band width and the parameter A∑D/A∑G) from Raman spectroscopy and the synthesis temperature are established. Based on the WAXS and Raman spectra data analysis the strong influence of the precursor carbide structure on the graphitization pathway is shown.

Rechargeable lithium–sulfur batteries (LSBs) are emerging as some of the most promising next-generation battery alternatives to state-of-the-art lithium-ion batteries (LIBs) due to their high gravimetric energy density, being inexpensive, and having an abundance of elemental sulfur (S8). However, one main, well-known drawback of LSBs is the so-called polysulfide shuttling, where the polysulfide dissolves into organic electrolytes from sulfur host materials. Numerous studies have shown the ability of porous carbon as a sulfur host material. Porous carbon can significantly impede polysulfide shuttling and mitigate the insulating passivation layers, such as Li2S, owing to its intrinsic high electrical conductivity. This work suggests a scalable and straightforward one-step synthesis method to prepare a unique interconnected microporous and mesoporous carbon framework via salt templating with a eutectic mixture of LiI and KI at 800 °C in an inert atmosphere. The synthesis step used environmentally friendly water as a washing solvent to remove salt from the carbon–salt mixture. When employed as a sulfur host material, the electrode exhibited an excellent capacity of 780 mAh g−1 at 500 mA g−1 and a sulfur loading mass of 2 mg cm−2 with a minor capacity loss of 0.36% per cycle for 100 cycles. This synthesis method of a unique porous carbon structure could provide a new avenue for the development of an electrode with a high retention capacity and high accommodated sulfur for electrochemical energy storage applications.

This paper presents a new type of black organic material-porous silica composite providing an extremely highly selective adsorption surface. This black composite was prepared by lamination on nano-sized pores with a carbon-like, π-extended structure, which can be converted via the on-site polymerization of 1,5-dihydroxynaphthalene with a triazinane derivative and a thermally induced condensation reaction with denitrification. This bottom-up fabrication method on porous materials had the great advantage of maintaining the pore characteristics of a raw porous material, but also the resultant black surface exhibited an extremely high molecular-shape selectivity; for example, that for trans- and cis-stilbenes reached 14.0 with the black layer-laminated porous silica, whereas it was below 1.2 with simple hydrophobized silica.

Amorphous carbons are disordered carbons with densities of circa 1.9–3.1 g/cc and a mixture of sp2 and sp3 hybridization. Using molecular dynamics simulations, we simulate diffusion in amorphous carbons at different densities and temperatures to investigate the transition between amorphous carbon and the liquid state. Arrhenius plots of the self-diffusion coefficient clearly demonstrate that there is a glass transition rather than a melting point. We consider five common carbon potentials (Tersoff, REBO-II, AIREBO, ReaxFF and EDIP) and all exhibit a glass transition. Although the glass-transition temperature (Tg) is not significantly affected by density, the choice of potential can vary Tg by up to 40%. Our results suggest that amorphous carbon should be interpreted as a glass rather than a solid.

Reduced graphene oxide (rGO) sheet decorated Na3V2(PO4)3 (NVP) microspheres were successfully synthesized by spray-drying method. The NVP microspheres were embedded by rGO sheets, and the surface of the particles were coated by rGO sheets and amorphous carbon. Thus, the carbon conductive network consisted of rGO sheets and amorphous carbon generated in the cathode material. NVP microspheres decorated with different content of rGO (about 0, 4, 8, and 12 wt%) were investigated in this study. The electrochemical performance of NVP exhibited a significant enhancement after rGO introduction. The electrode containing about 8 wt% rGO (NVP/G8) showed the best rate and cycle performance. NVP/G8 electrode exhibited the discharge capacity of 64.0 mAh g−1 at 70°C, and achieved high capacity retention of 95.5% after cycling at 10°C for 100 cycles. The polarization of the electrode was inhibited by the introduction of rGO sheets. Meanwhile, compared with the pristine NVP electrode, NVP/G8 electrode exhibited small resistance and high diffusion coefficient of sodium ions.

Separating functionalized single-wall carbon nanotubes (SWCNTs) from functionalized amorphous carbon is challenging, due to their polydispersity and similar physicochemical properties. We describe a single-step, dialytic separation method that takes advantage of the ability of heavily functionalized SWCNTs to bundle in a polar environment while maintaining their solubility. Experiments on functionalized SWCNTs were compared with functionalized, C60 fullerenes (buckyballs) to probe the general applicability of the method and further characterize the bundling process. This approach may simultaneously be used to purify a functionalization reaction mixture of unreacted small molecules and of residual solvents, such as dimethylformamide.

Innovative composites based on an amorphous-carbon matrix containing a second phase ZnO oxide and/or highly dispersed Zn metallic were synthesized via a modified Pechini route, in which a partial pyrolysis method was reached. Studies of adsorption in the dark and the photocatalytic activity for the cationic azo-dye, basic blue 41, and degradation were carried out. X-ray diffraction patterns for the carbon matrix and its composite with Zn show characteristics of the amorphous carbon. The infrared in the mid region of the composite prepared with ZnO and Zn exhibit vibrational bands related to bonds zinc oxide. The surface pH of the material is the main factor responsible for the adsorption of the azo-dye, but the contribution of mesopores favored the diffusion of molecules from the bulk of solution to the pore framework. Esters-like functional groups on the surface of carbons hinder the adsorption of the azo-dye. When Zn is embedded within amorphous carbon the photocatalytic activity of the composites showed up to 2.4 higher than neat ZnO. The enhancement in the photocatalytic activity and stability of C/ZnO/Zn and C/Zn composites is discussed in terms of a protector effect by the carbon layers inserted in composites. Carbon layers are responsible to inhibit the lixiviation of ZnO particles along irradiation.

Silver nanoparticles (NPs) are known to exhibit strong interaction with light photons because their surface conduction electrons undergo collective oscillations once photo-excited at specific wavelengths; the so-called surface plasmon resonance (SPR). Their incorporation into carbon-based material is shown to greatly influence the overall optical response of the matrix due to aggregation. In this paper, we studied the optical response of silver-irradiated amorphous carbon films due to varying fluence of 25 keV Ag ions in the range 2.5−3.4 × 1016 ions/cm2. Raman spectroscopy provided an insight into the microstructural details of the Ag:a-C nanocomposites such that access to bond characteristics of the films is enabled by directly linking the Raman information with sp2/sp3 configurations. Atomic force microscopy (AFM) analysis show significant increase in particle grain size and surface roughness of the films with increasing fluence while transmission electron microscopy (TEM) confirmed fluence-induced particle aggregation due to irradiation. Optical absorption studies revealed that the SPR of Ag NPs occurs in the wavelength range 418−395 nm in the irradiated films. The blue shift in plasmonic wavelength response is explained with respect to the fluence-induced increase in the particulate grain size and particle density as confirmed by AFM and TEM. The optical band gap energy ( E g ) of the pristine carbon film decreased from 1.79 eV to 1.41 eV while Urbach parameter ( E u ) increased from 0.01 eV to 12.0 eV, respectively with increasing fluence. These tunable optical parameters can be tailored into applications in surface coatings and as functional materials for solar cell efficiency enhancement.

Background signals from in situ-formed amorphous carbon, despite not being fully understood, are known to be a common issue in few-molecule surface-enhanced Raman scattering (SERS). Here, discrete gold and silver nanoparticle aggregates assembled by DNA origami were used to study the conditions for the formation of amorphous carbon during SERS measurements. Gold and silver dimers were exposed to laser light of varied power densities and wavelengths. Amorphous carbon prevalently formed on silver aggregates and at high power densities. Time-resolved measurements enabled us to follow the formation of amorphous carbon. Silver nanolenses consisting of three differently-sized silver nanoparticles were used to follow the generation of amorphous carbon at the single-nanostructure level. This allowed observation of the many sharp peaks that constitute the broad amorphous carbon signal found in ensemble measurements. In conclusion, we highlight strategies to prevent amorphous carbon formation, especially for DNA-assembled SERS substrates.

Hydrogenated graphite-like carbon composite films containing silicon (Si) and silver (Ag) (g-C:H:Si:Ag) were prepared by middle frequency magnetron sputtering deposition in argon (Ar) and acetylene (C2H2) mixture gases. The effects of precursor C2H2 fraction on the microstructure and properties were studied. The results of Raman and X-ray photoelectron spectroscope (XPS) revealed that the films were dominated by sp2 carbon sites. It was observed from transmission electron microscope (TEM) that the films contained nanoparticles mainly consisting of Ag, and their size increased with the decrease in the C2H2 fraction. Si was also found to aggregate in the areas where Ag nanoparticles formed in films with high Si content. The comparative studies on the frictional behaviors of films sliding against aluminum oxide were carried out in ambient air and saline solution. The g-C:H:Si:Ag films still exhibited outstanding frictional properties even when the test environment shifts from ambient air to saline solution.