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With the increasing importance of power storage devices, demand for the development of supercapacitors possessing both rapid reversible chargeability and high energy density is accelerating. Here we propose a simple process for the room temperature fabrication of pseudocapacitor electrodes consisting of a faradaic redox reaction layer on a metallic electrode with an enhanced surface area. As a model metallic electrode, an Au foil was irradiated with Ar

Novel glass-ceramic composites with optical bandgap tunability were synthesised. Zinc silicate powder (ZS) was mixed with multi-walled carbon nanotubes (MWCNTs) at various mass fractions (0, 1, 2, and 3 wt %), followed by argon sintering. X-ray diffraction (XRD) analysis revealed the structural change from an amorphous ZS phase to a crystalline willemite phase (Zn2SiO4) by adding MWCNTs, and the largest crystallite size was obtained for ZS with 2.0 wt% MWCNTs. Although the agglomeration of ZS and MWCNTs was observed by field emission scanning electron microscopy (FESEM), there was no chemical interaction between ZS and MWCNTs as confirmed by Fourier transform infrared spectroscopy (FTIR). MWCNTs enhanced the crystallisation, which led to the green emission of Zn2SiO4 blue-shifting from 572 nm to 557 nm. The narrowed optical bandgap of Zn2SiO4 was attributed to the MWCNT-induced exciton localised between the valence band and conduction band of Zn2SiO4. The bandgap tuning effect of MWCNTs potentially paved new ways to mass fabricate zinc silicate-based semiconductors with desirable optical bandgap energy Eg, which significantly benefits the sensor and laser-related industry.

Makale, WOS:000922183800001, In the early detection of sepsis, procalcitonin (PCT) appears to be a highly sensitive biomarker for severe inflammation and infection. A significant interaction between the electrode material to be used in the design of the biosensor and the material to be attached to the surface is of great importance. Here, we demonstrated a silver nanoparticle (AgNp) doped graphene-based sensitive PCT biosensor with low-cost, environmentally friendly materials. Cyclic voltammetry curves showing the reusability of the electrodes obtained were obtained and showed antibody-protein adhesion on the AgNp/SLG@ITO surface. The anodic and cathodic peak currents values after 20 cycles show that these values are suitable even after 20 measurements. Electrochemical impedance spectroscopy (EIS) studies confirmed the effects of PCT on binding events due to increasing con-centration at a constant PCT-antibody concentration. The limit of detection (LOD) value of the fabricated PCT/ Ab/AgNp/SLG@ITO impedimetric biosensor was determined as 0.55 ngmL-1. The low LOD value can be attributed to the uniform and large surface area of single-layer graphene (SLG) and noble AgNp. The LOD value based on the EIS studies has revealed that the PCT/Ab/AgNp/SLG@ITO impedimetric biosensor can be employed in real samples., Scientific Research Projects (BAP) Coordination Unit at Necmettin Erbakan University; Turkish Academy of Sciences (TUBA)

In this work, the potential of utilizing a waste latex-based precursor (i.e., natural rubber glove (NRG)) as a carbon source for carbon nanotube (CNT) fabrication via chemical vapor deposition has been demonstrated. Gas chromatography-mass spectroscopy (GC-MS) analysis reveals that the separation of the lightweight hydrocarbon chain from the heavier long chain differs in hydrocarbon contents in the NRG fraction (NRG-L). Both solid NRG (NRG-S) and NRG-L samples contain &gt, 63% carbon, &lt, 0.6% sulfur and &lt, 0.08% nitrogen content, respectively, as per carbon-nitrogen-sulfur (CNS) analysis. Growth of CNTs on the samples was confirmed by Raman spectra, SEM and TEM images, whereby it was shown that NRG-S is better than NRG-L in terms of synthesized CNTs yield percentage with similar quality. The optimum vaporization and reaction temperatures were 350 and 800 °C, respectively, considering the balance of good yield percentage (26.7%) and quality of CNTs (ID/IG = 0.84 ± 0.08, diameter ≈ 122 nm) produced. Thus, utilization of waste NRG as a candidate for carbon feedstock to produce value-added CNTs products could be a significant approach for eco-technology.

The feasibility of van der Waals (VdW) heteroepitaxy of molybdenum disulphide (MoS2) layers on gallium nitride (GaN) semiconductor has attracted significant interest in heterojunction optoelectronic device applications. Here, we report on the growth of uniform MoS2 layers on free-standing GaN semiconductor for vertical heterojunction device application. A uniform MoS2 layer was directly grown on the n-type GaN wafer by sulphurization process of molybdenum oxide thin layer. Raman and scanning electron microscopy (SEM) analyses showed homogenous growth of the few-layers MoS2 forming a continuous film, considering the suitability of GaN semiconductor substrate. The fabricated MoS2/GaN vertical heterojunction showed excellent rectifying diode characteristics with a photovoltaic photoresponsivity under monochromatic light illumination. The X-ray photoelectron spectroscopy (XPS) studies showed the conduction and valence band offset values are around 0.44 and 2.3 eV with type II band alignment in the fabricated heterojunction device. This will facilitate effective movement of photoexcited electrons across the MoS2–GaN junction, while a large valence band offset will prevent movement of holes towards the GaN, resulting in low recombination loss to obtain a photovoltage in the heterojunction device. Our study revealed the formation of large-area homogenous MoS2 layers on GaN wafer for vertical heterojunction device application.

Graphene synthesis at lower temperatures is quite important for a wider range of practical applications. Sn, which is recently found as a promising catalyst for the low-temperature graphene growth, is taken as the study material in this work. Based on the detailed transmission electron microscopy (TEM) observation, we found that catalytic activity of Sn nano-particles is highly temperature dependent which was observed during graphitization of amorphous carbon. For this study, C–Sn composite nanofibers were prepared on an edge of a carbon foil by the Ar+ ion irradiation with simultaneous supply of Sn. As-fabricated C–Sn composite nanofibers were observed to be the amorphous C nanofibers (CNFs) in which the Sn nanoparticles dispersed. The as-prepared samples were annealed at 180–250 °C in a vacuum and were characterized using Raman spectra and high-resolution TEM to study the graphitization process. The graphitization started to occur at an annealing temperature of 180 °C, which is much lower than the graphitization temperature for bulky Sn. Based on the detailed TEM observation of annealed samples, a model to explain the graphitization mechanism at such a low temperature was proposed.

Charge transfer interaction at the interface of semiconducting layered materials is of great interest to develop effective heterojunction optoelectronic devices. Here, we demonstrate the charge transfer interaction and formation of an active heterojunction between the molybdenum disulfide (MoS2) layer and p-type copper iodide (CuI) exhibiting excellent photoresponsive properties. The CuI film was fabricated by solid phase iodization of a copper film and direct thermal evaporation processes, which led to the formation of a transparent conducting layer. The thermally evaporated CuI film showed the main diffraction peak for the (111) plane, confirming the formation of the γ-CuI cubic crystal structure along the (111) plane on the MoS2 layers. The photoluminescence (PL) quenching effect was observed for the γ-CuI/MoS2 heterostructure, which can be attributed to the spontaneous separation of charge carriers at the interface. A photoresponsivity of 0.27 A/W was obtained at a bias voltage of 5 V for the γ-CuI/Mo...

For the fabrication of graphene-based nano-scale interconnects, precise control over their position and proper nanoscale soldering are essential. In this work, we report the Joule heat-induced conversion of amorphous carbon to graphene in an in situ TEM setup, using Mo as a catalyst. The catalytic role of Mo during graphene formation has been less explored compared to other metals like Cu or Ni. Compared to metals like Cu, Mo is less subject to electromigration and brittleness, making it suitable for high-temperature electronics. We found that during the electromigration of Mo, amorphous carbon nanofibers (CNFs) can be converted to highly crystalline few-layered graphene. It was also found that during the graphene formation process, agglomerated Mo particles can be effectively channeled to the end of graphene by voltage-driven electromigration. An agglomerated Mo particle between the probe and graphene acted as a soldering agent, providing the prospect of the further exploration of Mo as a nanoscale soldering material. This work explores the double role of Mo: as a catalyst for graphene synthesis and as a soldering material.

Highlights Extremely sensitive and prompt COVID-19 SERS biosensor to detect SARS-CoV-2 virus in the contaminated water at single-virus level.SERS sensor features a low detection limit of 80 copies mL−1 for the simulated contaminated water by SARS-CoV-2 virus as short as 5 min.ACE2-modified SERS sensor with machine-learning and identification standard enable rapid detection of novel yet-unknown coronaviruses. Supplementary Information The online version contains supplementary material available at 10.1007/s40820-021-00620-8., The current COVID-19 pandemic urges the extremely sensitive and prompt detection of SARS-CoV-2 virus. Here, we present a Human Angiotensin-converting-enzyme 2 (ACE2)-functionalized gold “virus traps” nanostructure as an extremely sensitive SERS biosensor, to selectively capture and rapidly detect S-protein expressed coronavirus, such as the current SARS-CoV-2 in the contaminated water, down to the single-virus level. Such a SERS sensor features extraordinary 106-fold virus enrichment originating from high-affinity of ACE2 with S protein as well as “virus-traps” composed of oblique gold nanoneedles, and 109-fold enhancement of Raman signals originating from multi-component SERS effects. Furthermore, the identification standard of virus signals is established by machine-learning and identification techniques, resulting in an especially low detection limit of 80 copies mL−1 for the simulated contaminated water by SARS-CoV-2 virus with complex circumstance as short as 5 min, which is of great significance for achieving real-time monitoring and early warning of coronavirus. Moreover, here-developed method can be used to establish the identification standard for future unknown coronavirus, and immediately enable extremely sensitive and rapid detection of novel virus. Supplementary Information The online version contains supplementary material available at 10.1007/s40820-021-00620-8.

Amorphous carbon (a-C) films containing metallic Cobalt nanoparticles (Co NPs) were deposited onto microgrids and SiO2/Si substrates by a magnetron sputter-deposition technique at room temperature (RT) using aC target with an attachment of a small Co platelet. Transmission electron microscopy (TEM) with a fast Fourier-transform (FFT) revealed the short-range ordering of the lattice corresponding to graphite (002) between Co NPs in the amorphous C matrix. The 2D peak and graphite (002) peak were clearly observed in Raman spectra and x-ray diffraction (XRD), respectively, for the Co–C films. X-ray photoelectron spectroscopy analyses were used to determine the metallic state of Co NPs and sp2 graphitization in the film. Thus, the Co NPs exhibited higher catalytic activity in spontaneous graphitization at low-temperature than Ni-NPs prepared under the same conditions. So, the metallic NPs were concluded to be promising as the catalyst for the ultra-low temperature graphitization in the solid-phase reaction.

Natural zeolite is widely used in removing ammonia via adsorption process because of its superior ion-exchange properties. Ceramic particle size affects the adsorptivity of particles toward ammonia. In this study, hollow fiber ceramic membrane (HFCM) was fabricated from natural zeolite via phase inversion. The effect of natural zeolite particle size toward the properties and performance of HFCM was evaluated. The results show that the HFCM with smaller particle sizes exhibited a more compact morphological structure with better mechanical strength. The adsorption performance of HFCM was significantly improved with smaller particle sizes because of longer residence time, as proven by the lower water permeability. A high adsorption performance of 96.67% was achieved for HFCM with the smallest particle size (36 &mu, m). These findings provide a new perspective on the promising properties of the natural zeolite-derived HFCM for ammonia removal.

The heterostructures fabricated with a combination of 2-D materials and conventional semiconductors are of great interest owing to their unique optoelectronic properties. Here, we demonstrate the fabrication of a germanium (Ge)/MoS2 heterostructure and observation of a photovoltaic action with broadband photoresponsivity. A thin interface was formed in-between the thermally evaporated Ge and chemical vapor deposited MoS2 layers, considering the atomically smooth surface of MoS2. The current density-voltage ( ${J}$ – ${V}$ ) measurement showed a diode like characteristic and photoresponsivity under light illumination. The Ge/MoS2 heterojunction showed an open circuit voltage ( ${V}_{\text {oc}}$ ) of 0.185 V and short circuit current density ( ${J}_{\text {sc}}$ ) of 0.028 mA/cm2 under illumination of light (wavelength 350–1100 nm). The transient photoresponse characteristics of the Ge-MoS2 heterojunction device showed significant photoresponsivity for ultraviolet, visible, and near-infrared light at different bias voltages. The interfacial charge transfer at the Ge-MoS2 heterojunction is the critical aspect to create an effective build in field for the broadband photoresponsive device. The demonstrated ultrathin heterojunction of Ge and MoS2 layers can be significant for developing self-powered broadband photodetectors.

In this work, we utilize Joule heating to convert Pt-embedded amorphous carbon nanofiber (CNF) to multiwall carbon nanotube (CNT) in a transmission electron microscope (TEM). The transformation process of Pt-embedded amorphous CNF to multiwall CNT and nano-soldering process using Pt encapsulated CNT was investigated in TEM in detail. Molten Pt-encapsulated inside CNF and CNT always flowed towards the anode, proving electromigration to be the dominant force over thermal migration. Controllable electromigration of Pt was utilized to connect the Pt-included CNT to another CNT, thus forming a seamlessly welded CNT structure. Further, two separate CNF were brought together to form Y-contact which was transformed into Y-junction CNT structure by controlled electromigration of Pt. Changes in morphology and electrical property during CNT formation and nano-soldering were probed in real time with high resolution TEM. Our method provides a procedure for the position control synthesis of CNT and its nano-soldering which can be an important step for future development of a CNT based nanoelectrical circuit.

Chemical state analysis is quite important in X-ray photoelectron spectroscopy. Auger parameter analysis is one of the useful methods to analyze the chemical state in X-ray photoelectron spectroscopy, because it is not necessary to take the charging effect into account for the analysis of nonconductive materials, especially for the simple material systems of a single chemical state. For the analysis of complicated complex systems, here, we developed the Auger parameter analysis combined with the curve fitting calculation using standard Auger spectra. Copper oxide complexes consisting of a mixture of CuO and Cu2O oxide states were formed on copper platelets by annealing in atmospheric ambient. For those samples, by combining the curve fitting using standard Cu, CuO, and Cu2O Auger spectra, two oxide states were clearly distinguished in the Auger parameter analysis. Thus, this advanced Auger parameter analysis is believed to be promising for the chemical state analysis of complicated complex systems.

Controlling the isotropic and anisotropic graphene growth in a chemical vapor deposition (CVD) process is a critical aspect to understand the growth dynamics for synthesizing large-area single crystals. Here, we reveal the effect of gas flow and controllability on isotropic and anisotropic graphene growth using a solid carbon source-based atmospheric pressure CVD method. It was found that the growth rate of round-shaped crystals (isotropic growth) was much higher than that of hexagonal crystals (anisotropic growth). The average growth speed increased from 0.276 μm min−1 to 1.89 μm min−1 by switching from hexagonal to circular domain growth in the CVD process. It was also found that there was no significant difference in the quality of graphene crystals when switching the growth from anisotropic to isotropic. Understanding the growth rate of round and hexagonal-shaped crystals can be critical to achieve faster growth of large single crystals. Again, the mixed edge structures (armchair and zigzag) in round-shaped graphene crystals without a fixed orientation unlike hexagonal crystals provide a better chance of seamless merging. Our findings can be significant in understanding the formation of isotropic and anisotropic graphene domains, their growth rate and quality for synthesizing large-area single crystals.

Most of the chemical vapor deposition (CVD) systems used for hexagonal boron nitride (h-BN) growth employ pyrolytic decomposition of a precursor molecule, such as ammonia borane (AB), at a temperature close to its melting point. So the control of its partial pressure is essential for high quality crystal growth. Here, we report on the edge controlled growth of a h-BN single crystal larger than 25 μm in edge length on purchased Cu foils. The key was the controlled supply of borazine gas generated by the decomposition of AB, and the stepwise decomposition of AB was found to be essential for the growth of regular h-BN crystals. The h-BN growth was mostly governed by the position of the nucleation point rather than Cu orientation as confirmed by electron back-scattered diffraction (EBSD) analysis. It was also demonstrated that the variation in temperature during the growth and cooling processes induced wrinkles larger than 20 nm due to the thermal straining of the Cu surface and a negative expansion coefficient of h-BN. These results provide a detailed understanding of h-BN growth, which will be applicable to other 2D materials.

We fabricate, measure and compare the effects of the bonding states of dopant nitrogen atoms in graphene devices, specifically on the liquid-flow-induced electricity by these devices. We find that nitrogen doping enhances the voltage induced by liquid flow regardless of the nitrogen bonding state. However, different nitrogen bonding states affect graphene’s conductivity differently: while graphitic nitrogen is suitable for electricity-generation applications, pyridinic nitrogen is hopeless for this purpose, due to the formation of symmetry-breaking defects of the latter. Keywords: Nitrogen doped graphene, Flow-induced electricity generation, Water-graphene interface

We performed single-walled carbon nanotube (SWCNT) growth on flexible stainless-steel foils by applying alcohol catalytic chemical vapor deposition (CVD) using an Ir catalyst with an alumina buffer layer. When the alumina thickness was 90 nm, vertically aligned SWCNTs with a thickness of 4.6 μm were grown. In addition, Raman and transmission electron microscope results showed that the diameters of most SWCNTs were distributed below 1.1 nm. Compared with conventional CVD growth where Si wafers are used as substrates, this method is more cost effective and easier to extend for mass production of small-diameter SWCNTs.

Here, we demonstrate the synthesis of monolayer molybdenum disulfide (MoS 2 ) ribbons and their branched structures by chemical vapor deposition (CVD) in sulfur-enriched environment. The growth of the MoS 2 ribbons, triangular and other crystals significantly depends on the exposure of sulfur and concentration of molybdenum oxide (MoO 3 ) vapor on the substrate surface. The width and length of the synthesized ribbons is around 5–10 and 50–100 μm, respectively, where the width reduces from the nucleation point toward the end of the ribbon. Unidirectional, bi and tri-directional growth of ribbons from the nucleation point with an angle of 60° and 120° were obtained attributing to crystallographic growth orientation of MoS 2 crystals. The directional growth of dichalcogenides ribbons is a significant challenge, our process shows that such unidirectional and other branched structures can be achieved by controlling the stoichiometric composition of MoO 3 and sulfur exposure on the substrate surface. Interestingly, all the individual and branched ribbons possess uneven abundant edge structures, where the edges are formed with angles of 60° and 120°, indicating variation in molybdenum and sulfur edge terminations. The directional growth of MoS 2 ribbons with defined edge structures in particular CVD condition can open up new possibilities for electronic and electrochemical applications.

Anode-supported micro-tubular solid oxide fuel cell (MT-SOFC) made from lithium (Li) doped cerium gadolinium oxide (CGO) electrolyte was prepared via phase inversion based co-extrusion/co-sintering technique. In this study, the co-sintering temperature of CGO electrolyte with anode layer was reduced by adding Li that acts as sintering additive. The prepared Li doped CGO (Li-CGO) were characterized by shrinkage analysis, atomic resolution analytical microscope (ARM) observation and X-ray photoelectron spectroscopy (XPS) spectra. Meanwhile, the developed half-cell of MT-SOFC which was co-sintered at 1350–1500 °C with interval of 50 °C were characterized by its mechanical strength, gas tightness and microstructural analysis. The electrochemical performances of the cells were tested in anode-supported MT-SOFCs with configuration of Ni-CGO anode, Li-CGO electrolyte and LSCF-CGO cathode using humidified hydrogen as fuel and oxygen air as oxidant. MT-SOFCs fabricated with Li-CGO electrolyte were found to exhibit maximum power density of 60 Wm − 2 at 500 °C compared to 200 Wm − 2 for cells with unmodified CGO electrolyte. The poor performance of cell with Li-CGO electrolyte is probably due to the combined effects of (i) moderately dense electrolyte layer and (ii) appearance of electronic conductivity in Li-CGO electrolyte. Nevertheless, lowering the sintering temperature has shown good properties of the electrolyte materials, which allows the electrolyte materials and anode can be co-sintered together at lower temperature.

An insulating polymer, radiation vulcanization natural of rubber latex (RVNRL), was successfully converted into electrically conductive nanocomposite by the addition of reduced graphene oxide (rGO) assisted by sodium 1,4-bis(neopentyloxy)-3-(neopentyloxycarbonyl)-1,4-dioxobutane-2-sulfonate (TC14) surfactant. The starting material, graphene oxide (GO), was initially synthesized by electrochemical exfoliation assisted by TC14 surfactant. Then, GO/RVNRL nanocomposite was fabricated by latex technology. For rGO/RVNRL nanocomposite, the synthesized GO was further reduced to rGO using hydrazine hydrate and showed electrical enhancement up to 1.32 × 10−3 S cm−1 compared with GO when composited with RVNRL (8.64 × 10−4 S cm−1). For comparison, rGO/RVNRL nanocomposite assisted by the commercially available surfactant sodium dodecyl sulfate was prepared, and its electrical conductivity was found to be 1.79 × 10−5 S cm−1, which was several orders of magnitude lower than those of GO/RVNRL and rGO/RVNRL nanocomposites prepared with TC14 surfactant. C–V measurements taken for TC14-rGO/RVNRL and TC14-GO/RVNRL nanocomposites showed specific capacitances of 95 and 63 F g−1, respectively. The structural properties of nanocomposites were characterized using FESEM, HRTEM, UV–Vis, micro-Raman, XRD, FT-IR spectroscopy, and TGA studies. This study was the first to report on the success of converting the insulator polymer RVNRL into a conductive nanocomposite assisted by TC14 surfactant. The nanocomposite can be a new electrode material for supercapacitor application.

Graphene is generally synthesized at high temperatures. Here we demonstrate a simple method to synthesize graphene at 150 °C. Carbon foils were irradiated with Ar+ ions at 1 keV with a simultaneous supply of catalyst metal without any intentional heating to survey the novel catalyst for graphene growth at low temperature. The ion irradiated surfaces were covered with densely distributed conical structures sometimes with a nanofiber on their respective tips. As revealed by high resolution (HR) transmission electron microscopy (TEM), the conical tips featured few layer graphene only for the newly selected catalyst metal, In, which is rarely used for the chemical vapor deposition (CVD) synthesis of graphene. This observation gives a new insight into the catalytic activity during graphene synthesis. Encouraged by this ion-induced graphene formation, samples of a thin, amorphous carbon film on SiO2 substrates overlaid with this novel catalyst film were prepared, and finally, graphene growth was achieved by simple vacuum heating at 150 °C.

Anisotropic etching of graphene and other two dimensional materials is an important tool to understand the growth process as well as enabling fabrication of various well-defined structures. Here, we reveal the influence of copper foil polycrystalline structure on anisotropic etching process of as-synthesized graphene. Graphene crystals were synthesized on the polycrystalline Cu foil by a low-pressure chemical vapor deposition (LPCVD) system. Microscopic analysis shows difference in shape, size and stripes alignment of graphene crystals with dissimilar nucleation within closure vicinity of neighboring Cu grains. Post-growth etching of such graphene crystals also significantly affected by the crystallographic nature of Cu grains as observed by the field emission scanning electron microscope (FE-SEM) and electron back scattered diffraction (EBSD) analysis. Hexagonal hole formation with anisotropic etching is observed to be independent of the stripes and wrinkles in the synthesized graphene. We also observed variation in etched pattern of the graphene depending on the base Cu grain orientations, attributing to difference in nucleation and growth process. The findings can facilitate to understand the nature of microscopic etched pattern depending on metal catalyst crystallographic structure.

Regenerated cellulose membrane was used as bio-template nanoreactor for the formation of rutile TiO2 mesoporous, as well as in-situ carbon dopant in acidified sol-gel system. The effects of calcination temperature on the physicochemical characteristic of core-shell nanostructured of bio-templated C-doped mesoporous TiO2 are highlighted in this study. By varying the calcination temperature, the thickness of the carbon shell coating on TiO2, crystallinity, surface area, and optical properties could be tuned as confirmed by HRTEM, nitrogen adsorption/desorption measurement, XRD and UV–vis-NIR spectroscopy. The results suggested that increment in the calcination temperature would lead to the band gap narrowing from 2.95 to 2.80 eV and the thickness of carbon shell increased from 0.40 to 1.20 nm. The x-ray photoelectron spectroscopy showed that the visible light absorption capability was mainly due to the incorporation of carbon dopant at interstitial position in the TiO2 to form OTiC or TiOC bond. In addition, the formation of the carbon core-shell nanostructured was due to carbonaceous layer grafted onto the surface of TiO2 via TiOC and TiOCO bonds. The result indicated that bio-templated C-doped core-shell mesoporous TiO2 prepared at 300 °C exhibited the highest photocatalytic activity. It is worthy to note that, the calcination temperature provided a huge impact towards improving the physicochemical and photocatalytic properties of the prepared bio-templated C-doped core-shell mesoporous TiO2.