Vacuum ultraviolet field emission lamp consisting of neodymium ion doped lutetium fluoride thin film as phosphor.

A vacuum ultraviolet (VUV) field emission lamp was developed by using a neodymium ion doped lutetium fluoride (Nd(3+) : LuF3) thin film as solid-state phosphor and carbon nanofiber field electron emitters. The thin film was synthesized by pulsed laser deposition and incorporated into the lamp. The cathodoluminescence spectra of the lamp showed multiple emission peaks at 180, 225, and 255 nm. These emission spectra were in good agreement with the spectra reported for the Nd(3+) : LuF3 crystal. Moreover, application of an acceleration voltage effectively increased the emission intensity. These results contribute to the performance enhancement of the lamp operating in the VUV region.

Efficiency of magnetic zeolitic imidazolate framework-8 (ZIF-8) modified graphene oxide for lead adsorption.

Simple and efficient removal of Pb(II) ion from aqueous solution through adsorption has accelerated the development of many new composites to improve this popular method. In this study, the composites of graphene oxide (GO), zeolitic imidazolate framework-8 (ZIF-8), and magnetic materials were synthesized via coprecipitation method utilizing a different molar ratio between FeCl2 and FeCl3 of 1:0.5, 2:1, 3:1.5, and 4:2. The ZIF-8/GO was prepared via room temperature synthesis method prior to its further modification with magnetic materials for ease of separation. It was observed that the MZIF-8/GO2 of molar ratio 2:1 showed the best performance in adsorbing Pb(II) ion. As confirmed by FESEM image, it appeared to be ZIF-8 particles that have grown all over the GO platform and overlayed with Fe3O4 granular-shaped particles. The MZIF-8/GO2 successfully achieved 99% removal of Pb(II) within 10 min. The optimum values obtained for the initial concentration of Pb (II) were 100 mg/L, pH of 4 to 6, and adsorbent dosage used was 10 mg. The Langmuir isotherm and the pseudo-second-order kinetic model were deemed suitable to evaluate the adsorption of Pb(II) using MZIF-8/GO2. Results showed that MZIF-8GO2 achieved a maximum adsorption capacity of 625 mg/g of Pb(II) adsorption. All parent materials demonstrated a good synergistic effects, while exhibiting a significant contribution in providing active sites for Pb(II) adsorption. Therefore, this ternary composite of MZIF-8/GO2 is expected to be a promising adsorbent for Pb(II) adsorption from aqueous solution with an added value of ease of post phase separation using external magnetic field.

Control of morphology and crystallinity of CNTs in flame synthesis with one-dimensional reaction zone.

The growth of carbon nanotubes (CNTs) in a flame requires conditions that are difficult to achieve in a highly heterogeneous environment. Therefore, the analysis of the properties of the reaction zone within the flame is critical for the optimal growth of CNTs. In the present study, a comprehensive comparison between the CNT synthesis using a methane diffusion flame and a premixed flame is conducted regarding the morphology and crystallinity of the as-grown nanotubes. The premixed burner configuration created a flame that is stabilized through axisymmetric stagnation flow through sintered metal with one-dimensional geometry, different from a conventional co-flow flame. The significant difference in temperature distribution between the two flames causes a difference in the characteristics of the growth products. In the diffusion flame, the growth is limited to specific regions at certain height-above-burner (HAB) values with a temperature range of 750 to 950 °C at varying radial locations. The identified growth regions at different HAB values showed similar temperature distributions that yield CNTs of similar characteristics. Interestingly, the growth of CNTs in the premixed flame is dictated by only the HAB because the temperature distribution is relatively uniform along the radial directions but significantly different in the vertical direction. 17.3% variation in temperature in the axial direction successfully led to 44% and 66% variation in CNT diameter and crystallinity, respectively. The morphology control capability demonstrated in the present study is important for CNT functionalization for energy storage, nanosensor, and nanocomposite applications, where diameter and crystallinity are influential properties that govern the overall performance of the components.

Fabrication of ion-induced carbon-cobalt nanocomposite fibers: effect of cobalt supply rate.

Graphite surfaces were irradiated by argon (Ar+) ions at 1 keV with a simultaneous cobalt (Co) supply at room temperature. Various kinds of carbon nanocomposites, such as nanocones with and without single nanofibers on their tops, nanorods and fish-scale-like nanoprotrusions, were formed depending on Co supply rates. It has been observed that with increasing the Co supply rate the formation of nanoprotrusions without nanofibers became prominent. Both nanofibers and nanoprotrusions were surely composed of carbon and Co, as confirmed by energy-dispersive X-ray analysis. The cobalt carbon nanocomposite fibers (CCNFs), -1.5 microm in average length, were grown on the top of the nanocones at the Co supply rate of 1.0 nm/min. The field electron emission characteristics of CCNFs thus grown indicated that there is an optimum parameter for the CCNF growth to achieve the better emission performance than that of pristine Ar(+)-induced carbon nanofibers.

Graphene-based nanomaterials as antimicrobial surface coatings: A parallel approach to restrain the expansion of COVID-19.

The recently emerged severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has become a significant and topmost global health challenge of today. SARS-CoV-2 can propagate through several direct or indirect means resulting in its exponential spread in short times. Consequently, finding new research based real-world and feasible solutions to interrupt the spread of pathogenic microorganisms is indispensable. It has been established that this virus can survive on a variety of available surfaces ranging from a few hours to a few days, which has increased the risk of COVID-19 spread to large populations. Currently, available surface disinfectant chemicals provide only a temporary solution and are not recommended to be used in the long run due to their toxicity and irritation. Apart from the urgent development of vaccine and antiviral drugs, there is also a need to design and develop surface disinfectant antiviral coatings for long-term applications even for new variants. The unique physicochemical properties of graphene-based nanomaterials (GBNs) have been widely investigated for antimicrobial applications. However, the research work for their use in antimicrobial surface coatings is minimal. This perspective enlightens the scope of using GBNs as antimicrobial/antiviral surface coatings to reduce the spread of transmittable microorganisms, precisely, SARS-CoV-2. This study attempts to demonstrate the synergistic effect of GBNs and metallic nanoparticles (MNPs), for their potential antiviral applications in the development of surface disinfectant coatings. Some proposed mechanisms for the antiviral activity of the graphene family against SARS-CoV-2 has also been explained. It is anticipated that this study will potentially lead to new insights and future trends to develop a framework for further investigation on this research area of pivotal importance to minimize the transmission of current and any future viral outbreaks.

Research and Development Journey and Future Trends of Hollow Fiber Membranes for Purification Applications (1970-2020): A Bibliometric Analysis.

Hollow fiber membrane (HFM) technology has received significant attention due to its broad range separation and purification applications in the industry. In the current study, we applied bibliometric analysis to evaluate the global research trends on key applications of HFMs by evaluating the global publication outputs. Results obtained from 5626 published articles (1970-2020) from the Scopus database were further manipulated using VOSviewer software through cartography analysis. The study emphasizes the performance of most influential annual publications covering mainstream journals, leading countries, institutions, leading authors and author's keywords, as well as future research trends. The study found that 62% of the global HFM publications were contributed by China, USA, Singapore, Japan and Malaysia, followed by 77 other countries. This study will stimulate the researchers by showing the future-minded research directions when they select new research areas, particularly in those related to water treatment, biomedical and gas separation applications of HFM.

Synthesis and Characterization of Titanium Dioxide Hollow Nanofiber for Photocatalytic Degradation of Methylene Blue Dye.

Environmental crisis and water contamination have led to worldwide exploration for advanced technologies for wastewater treatment, and one of them is photocatalytic degradation. A one-dimensional hollow nanofiber with enhanced photocatalytic properties is considered a promising material to be applied in the field. Therefore, we synthesized titanium dioxide hollow nanofibers (THNF) with extended surface area, light-harvesting properties and an anatase-rutile heterojunction via a template synthesis method and followed by a calcination process. The effect of calcination temperature on the formation and properties of THNF were determined and the possible mechanism of THNF formation was proposed. THNF nanofibers produced at 600 °C consisted of a mixture of 24.2% anatase and 75.8% rutile, with a specific surface area of 81.2776 m2/g. The hollow nanofibers also outperformed the other catalysts in terms of photocatalytic degradation of MB dye, at 85.5%. The optimum catalyst loading, dye concentration, pH, and H2O2 concentration were determined at 0.75 g/L, 10 ppm, pH 11, and 10 mM, respectively. The highest degradation of methylene blue dye achieved was 95.2% after 4 h of UV irradiation.

Room-temperature graphitization in a solid-phase reaction.

Graphitized carbon including graphene has recently become one of the most investigated advanced materials for future device applications, but a prerequisite for broadening its range of applications is to lower its growth temperature. Here we report a great decrease in graphitization temperature using the well-known catalyst Ni. Amorphous carbon films with Ni nanoparticles (NPs) were deposited, using a simple one-step magnetron sputtering method, onto microgrids and a SiO2/Si substrate for transmission electron microscopy (TEM) and Raman spectroscopy analyses, respectively. The amorphous carbon surroundings and locations between the Ni NPs started to become graphitized during the film deposition even at room temperature (RT) and 50 °C. The graphitization was confirmed by both high-resolution TEM (HR-TEM) and Raman 2D peak analyses. The increase in the relative amount of Ni in the amorphous carbon film led to the partial oxidation of the larger Ni NPs, resulting in less graphitization even at an elevated deposition temperature. Based on the detailed HR-TEM analyses, a decreased oxidation of NPs and enhanced solubility of carbon into Ni NPs were believed to be key for achieving low-temperature graphitization.

Adsorptive removal of heavy metal ions using graphene-based nanomaterials: Toxicity, roles of functional groups and mechanisms.

The endless introduction of toxic heavy metals through industrialization has worsened the heavy metal pollution in the environment. Thus, the need for its effective removal has become more crucial than before. Studies on graphene-based nanomaterials and their use in removing heavy metals are gaining tremendous traction over the past decade. The properties of graphene oxide (GO), such as large surface areas, desired functional groups and excellent mechanical properties are advantageous. Nevertheless, due to its tendency to agglomerate and difficulty in phase separation after treatment, the functionalization of GO using various materials of different surface functional groups is an ongoing study. The surface modification of GO is done by using various materials to introduce heteroatoms, which have high affinity for heavy metals. This review summarizes the utilization of different surface functional groups, such as oxygen-containing, nitrogen-containing, and sulphur-containing functionalized graphene oxide composites in the adsorption of cationic and oxyanionic heavy metals. The toxicity of these heavy metals is also addressed. Furthermore, the interactions between adsorbents and heavy metals which are influenced by pH and surface functional groups, are also discussed in detail. This is followed by the review in adsorption isotherms and kinetics. Future research needs are also offered.

Visualizing copper assisted graphene growth in nanoscale.

Control synthesis of high quality large-area graphene on transition metals (TMs) by chemical vapor deposition (CVD) is the most fascinating approach for practical device applications. Interaction of carbon atoms and TMs is quite critical to obtain graphene with precise layer number, crystal size and structure. Here, we reveal a solid phase reaction process to achieve Cu assisted graphene growth in nanoscale by in-situ transmission electron microscope (TEM). Significant structural transformation of amorphous carbon nanofiber (CNF) coated with Cu is observed with an applied potential in a two probe system. The coated Cu particle recrystallize and agglomerate toward the cathode with applied potential due to joule heating and large thermal gradient. Consequently, the amorphous carbon start crystallizing and forming sp(2) hybridized carbon to form graphene sheet from the tip of Cu surface. We observed structural deformation and breaking of the graphene nanoribbon with a higher applied potential, attributing to saturated current flow and induced Joule heating. The observed graphene formation in nanoscale by the in-situ TEM process can be significant to understand carbon atoms and Cu interaction.

In situ TEM observation of Fe-included carbon nanofiber: evolution of structural and electrical properties in field emission process.

In situ transmission electron microscopy (TEM) of single Fe-included carbon nanofibers (CNFs) revealed that the fine polycrystalline structure in the shank region of CNFs transformed to graphitic, hollow structures during a field emission (FE) process. The iron metal platelets agglomerated during the FE process and perceptibly were emitted from the shank, which featured bamboo-like carbon nanotube (CNT) structures. The structural evolution also improved the electrical properties, and the FE current was remarkably increased, that is, 1000 times higher than the initial value (from 10(-9) to 10(-6) A). The structural transformations were effectuated by Joule heating that generated simultaneously during the FE process. The in situ TEM study of room-temperature-synthesized CNFs could provide essential information regarding CNFs' structural transformation for their possible application in future electron emitter sources.

Highly transparent and flexible field emission devices based on single-walled carbon nanotube films.

Single-walled carbon nanotubes (SWNTs) have been used successfully to fabricate highly transparent and flexible field emission displays (FEDs). Field emission measurements indicated that SWNTs films have great potential to work as building blocks for next generation transparent and flexible FEDs.