Conversion Of Electronic Energy Research Articles

Development of MnWO4:Ag nanodilute magnetic semiconductors with tunable magnetic and optoelectronic properties

The bandgap engineered MnWO4 nanoparticles doped with Ag were developed using a facile one-pot synthesis method. The impurity doping concentration of Ag was varied from 1 to 5 wt percentages to tune the interactions between manganese tungstate and silver ions to obtain desirable magnetic and optoelectronic properties. The structural properties of the MnWO4 particles with various concentrations of Ag were investigated using X-ray diffraction. The optical properties of the pristine and Ag-doped MnWO4 particles were determined using UV‒Vis and photoluminescence spectroscopy. The impurity concentration-dependent structural transformations and changes in the vibrational modes, lattice dynamics, electronic transitions and optoelectronic properties of the prepared materials were analyzed using Raman spectroscopy. The topology, morphology and elemental analysis of the synthesized nanoparticles were elucidated using HRTEM, SAED, SEM and EDX techniques. The magnetic properties of the MnWO4:Ag nanoparticles were measured using a vibrating sample magnetometer (VSM). The obtained results suggested that Ag-doped MnWO4 nanosystems show enhanced and tunable magnetic properties suitable for nanodilute magnetic semiconductor (nDMS) applications. The presented work opens a range of possibilities for the development of advanced materials with applications in optoelctronics, nanomedicine, energy-efficient electronic devices and energy conversion.

Pristine MOF Materials for Separator Application in Lithium-Sulfur Battery.

Lithium-sulfur (Li-S) batteries have attracted significant attention in the realm of electronic energy storage and conversion owing to their remarkable theoretical energy density and cost-effectiveness. However, Li-S batteries continue to face significant challenges, primarily the severe polysulfides shuttle effect and sluggish sulfur redox kinetics, which are inherent obstacles to their practical application. Metal-organic frameworks (MOFs), known for their porous structure, high adsorption capacity, structural flexibility, and easy synthesis, have emerged as ideal materials for separator modification. Efficient polysulfides interception/conversion ability and rapid lithium-ion conduction enabled by MOFs modified layers are demonstrated in Li-S batteries. In this perspective, the objective is to present an overview of recent advancements in utilizing pristine MOF materials as modification layers for separators in Li-S batteries. The mechanisms behind the enhanced electrochemical performance resulting from each design strategy are explained. The viewpoints and crucial challenges requiring resolution are also concluded for pristine MOFs separator in Li-S batteries. Moreover, some promising materials and concepts based on MOFs are proposed to enhance electrochemical performance and investigate polysulfides adsorption/conversion mechanisms. These efforts are expected to contribute to the future advancement of MOFs in advanced Li-S batteries.

Electromagnetic Field Drives the Bioelectrocatalysis of γ-Fe2O3-Coated Shewanella putrefaciens CN32 to Boost Extracellular Electron Transfer.

The microbial hybrid system modified by magnetic nanomaterials can enhance the interfacial electron transfer and energy conversion under the stimulation of a magnetic field. However, the bioelectrocatalytic performance of a hybrid system still needs to be improved, and the mechanism of magnetic field-induced bioelectrocatalytic enhancements is still unclear. In this work, γ-Fe2O3 magnetic nanoparticles were coated on a Shewanella putrefaciens CN32 cell surface and followed by placing in an electromagnetic field. The results showed that the electromagnetic field can greatly boost the extracellular electron transfer, and the oxidation peak current of CN32@γ-Fe2O3 increased to 2.24 times under an electromagnetic field. The enhancement mechanism is mainly due to the fact that the surface modified microorganism provides an elevated contact area for the high microbial catalytic activity of the outer cell membrane's cytochrome, while the magnetic nanoparticles provide a networked interface between the cytoplasm and the outer membrane for boosting the fast multidimensional electron transport path in the magnetic field. This work sheds fresh scientific light on the rational design of magnetic-field-coupled electroactive microorganisms and the fundamentals of an optimal interfacial structure for a fast electron transfer process toward an efficient bioenergy conversion.

Functionalization of Carbon Nanotubes in Polystyrene and Properties of Their Composites: A Review.

The inherent π-π interfacial interaction between carbon nanotubes (CNTs) and polystyrene (PS) makes the CNT/PS composite a representative thermoplastic nanocomposite. However, the strong van der Waals force among CNTs poses challenges to achieving effective dispersion. This review provides an overview of various CNT functionalization methods for CNT/PS composites, encompassing covalent grafting with PS-related polymers and non-covalent modification. A focus in this section involves the pre-introduction surface modification of CNTs with PS or PS-related polymers, substantially enhancing both CNT dispersibility and interfacial compatibility within the PS matrix. Furthermore, a comprehensive summary of the mechanical, electrical, thermal, and electromagnetic shielding properties of CNT/PS nanocomposites is provided, offering an overall understanding of this material. The surface modification methods of CNTs reviewed in this paper can be extended to carbon material/aromatic polymer composites, assisting researchers in customizing the optimal surface modification methods for CNTs, maximizing their dispersibility, and fully unleashing the various properties of CNTs/polymer composites. Additionally, high-performance CNTs/PS composites prepared using appropriate CNT modification methods have potential applications in areas such as electronic devices, sensors, and energy storage and conversion.

Whistler‐Mode Waves Inside Short Large‐Amplitude Magnetic Field Structures: Characteristics and Generation Mechanisms

AbstractShort large‐amplitude magnetic structures (SLAMS) frequently appear near the bow shock. Inside steepening SLAMS, whistler‐mode waves are coherently generated at their leading edges. These waves are crucial for electron dynamics, energy conversion and magnetic reconnection near the shock. Nevertheless, the characteristics and generation of the whistler‐mode waves inside SLAMS are still unclear. In this study, we conducted a statistical analysis of whistler‐mode waves within SLAMS near the Earth's bow shock to investigate their properties and generation mechanisms. We found that these waves are mainly excited by electron temperature anisotropy with 99% of them falling below the nonlinear resonant threshold. The combination of a low background magnetic field and intense steepening at SLAMS' leading edge makes it the main source region of whistler‐mode waves and may induce the nonlinear resonance of whistler‐mode waves.

Stacking Order Engineering of Two-Dimensional Materials and Device Applications.

Stacking orders in 2D van der Waals (vdW) materials dictate the relative sliding (lateral displacement) and twisting (rotation) between atomically thin layers. By altering the stacking order, many new ferroic, strongly correlated and topological orderings emerge with exotic electrical, optical and magnetic properties. Thanks to the weak vdW interlayer bonding, such highly flexible and energy-efficient stacking order engineering has transformed the design of quantum properties in 2D vdW materials, unleashing the potential for miniaturized high-performance device applications in electronics, spintronics, photonics, and surface chemistry. This Review provides a comprehensive overview of stacking order engineering in 2D vdW materials and their device applications, ranging from the typical fabrication and characterization methods to the novel physical properties and the emergent slidetronics and twistronics device prototyping. The main emphasis is on the critical role of stacking orders affecting the interlayer charge transfer, orbital coupling and flat band formation for the design of innovative materials with on-demand quantum properties and surface potentials. By demonstrating a correlation between the stacking configurations and device functionality, we highlight their implications for next-generation electronic, photonic and chemical energy conversion devices. We conclude with our perspective of this exciting field including challenges and opportunities for future stacking order engineering research.

Enhanced CO2 Reduction by Electron Shuttle Molecules via Coupling Different Electron Transport Processes in Microbial Electrosynthesis

Electron shuttling molecules (ESMs) have been proven to accelerate the electron transfer from the electrode to the electroactive microorganism in microbial electrosynthesis (MES) for higher CO2 reduction or chemical production rate. However, the microbial electron acceptors of electroactive microorganisms and their responses to different electron shuttling molecules in MES were still unknown. In this study, three kinds of ESMs, e.g., riboflavin (B2), methyl viologen (MV) and neutral red (NR) were applied in the MES for acetate production to explore the mechanism of different ESMs on microbial interactions. The acetate concentrations were 41% and 51% higher than that of the control in B2 and NR addition. The acetogens relative abundances of control, B2, MV and NR were 0.29%, 5.68%, 22.78% and 42.89%, respectively. The microbial function profile of the microbial community on the biocathodes indicated that the performance of acetate production was more closely related to the expression of electron transport. The B2 was coupled with the NADH complex and hydrogenase, while MV and NR were coupled with the Rnf complex to support electron transfer and energy conversion via various electron transfer pathways. The study revealed that the ESMs coupled with different electron transport complexes of microorganisms to achieve electron transfer, resulting in product changes.

Investigation of photocatalytic performance of GQD/Ir(III) complex nanocomposite: Effect of π-conjugation

This study explores the photophysics of graphene quantum dots (GQDs) and iridium complexes, and their nanocomposites using density functional theory calculations. We evaluate the electronic structures and energy conversion efficiencies of the nanocomposites as a function of the π-conjugation of the 2-aryl substituents. Our results indicate that the GQD primarily influences the occupied frontier molecular orbitals of the nanocomposite, while the unoccupied frontier molecular orbitals are mainly determined by the Ir(III) complex. The dipolar interaction between GQD and the Ir(III) complex causes a redistribution of charge between the two molecules, resulting in enhanced delocalization of electrons in the nanocomposite. The nanocomposite's unique electronic configuration results in enhanced charge separation, leading to improved electron injection into the semiconductor. Moreover, the high-energy absorption is determined by GQD, while the Ir(III) complex primarily contributes to low-energy absorption. Furthermore, increasing the π-conjugation of the 2-aryl substituent increases the nanocomposite's LUMO levels and open-circuit voltage, but decreases its light harvesting ability. However, the electron-hole recombination time increases, leading to improved short-circuit current and energy conversion efficiency. Our computational results provide valuable insight into the photophysical properties of GQD/Ir(III) complex nanocomposites, specifically the important elements affecting their photocatalytic performance.

Vertical strain engineering of Van der Waals heterostructures

Van der Waals materials and their interfaces play critical roles in defining electrical contacts for nanoelectronics and developing vehicles for mechanoelectrical energy conversion. In this work, we propose a vertical strain engineering approach by enforcing pressure across the heterostructures. First-principles calculations show that the in-plane band structures of 2D materials such as graphene, h-BN, and MoS2 as well as the electronic coupling at their contacts can be significantly modified. For the graphene/h-BN contact, a band gap in graphene is opened, while at the graphene/MoS2 interface, the band gap of MoS2 and the Schottky barrier height at contact diminish. Changes and transitions in the nature of contacts are attributed to localized orbital coupling and analyzed through the redistribution of charge densities, the crystal orbital Hamilton population, and electron localization, which yield consistent measures. These findings offer key insights into the understanding of interfacial interaction between 2D materials as well as the efficiency of electronic transport and energy conversion processes.

Efficient Electron Acceleration Driven by Flux Rope Evolution during Turbulent Reconnection

Magnetic flux ropes or magnetic islands are important structures responsible for electron acceleration and energy conversion during turbulent reconnection. However, the evolution of flux ropes and the corresponding electron acceleration process still remain open questions. In this paper, we present a comparative study of flux ropes observed by the Magnetospheric Multiscale mission in the outflow region during an example of turbulent reconnection in Earth's magnetotail. Interestingly, we find the farther the flux rope is away from the X-line, the bigger the size of the flux rope and the slower it moves. We estimate the power density converted at the observed flux ropes via the three fundamental electron acceleration mechanisms: Fermi, betatron, and parallel electric field. The dominant acceleration mechanism at all three flux ropes is the betatron mechanism. The flux rope that is closest to the X-line, having the smallest size and the fastest moving velocity, is the most efficient in accelerating electrons. Significant energy also returns from particles to fields around the flux ropes, which may facilitate the turbulence in the reconnection outflow region.

Ion-Scale Magnetic Flux Rope Generated From Electron-Scale Magnetopause Current Sheet: Magnetospheric Multiscale Observations.

We present in-depth analysis of three southward-moving meso-scale (ion-to magnetohydrodynamic-scale) flux transfer events (FTEs) and subsequent crossing of a reconnecting magnetopause current sheet (MPCS), which were observed on 8 December 2015 by the Magnetospheric Multiscale spacecraft in the subsolar region under southward and duskward magnetosheath magnetic field conditions. We aim to understand the generation mechanism of ion-scale magnetic flux ropes (ISFRs) and to reveal causal relationship among magnetic field structures, electromagnetic energy conversion, and kinetic processes in magnetic reconnection layers. Results from magnetic field reconstruction methods are consistent with a flux rope with a length of about one ion inertial length growing from an electron-scale current sheet (ECS) in the MPCS, supporting the idea that ISFRs can be generated through secondary reconnection in an ECS. Grad-Shafranov reconstruction applied to the three FTEs shows that the FTEs had axial orientations similar to that of the ISFR. This suggests that these FTEs also formed through the same secondary reconnection process, rather than multiple X-line reconnection at spatially separated locations. Four-spacecraft observations of electron pitch-angle distributions and energy conversion rate suggest that the ISFR had three-dimensional magnetic topology and secondary reconnection was patchy or bursty. Previously reported positive and negative values of , with magnitudes much larger than expected for typical MP reconnection, were seen in both magnetosheath and magnetospheric separatrix regions of the ISFR. Many of them coexisted with bi-directional electron beams and intense electric field fluctuations around the electron gyrofrequency, consistent with their origin in separatrix activities.

Energy Conversion and Transfer in the Luminescence of CeSc3(BO3)4:Cr3+ Phosphor.

Novel near-infrared (NIR) phosphors are in demand for light-emitting diode (LED) devices to extend their suitability for new applications and, in turn, support the sustainable and healthy development of the LED industry. The Cr3+ has been used as an activator in the development of new NIR phosphors. However, one main obstacle for the Cr3+-activated phosphors is the low luminescence efficiency due to the spin-forbidden d-d transition of Cr3+. The rare-earth (RE) huntite minerals that crystallize in the form of REM3(BO3)4 (M = Al, Sc, Cr, Fe, Ga) have a large family of members, including the rare-earth scandium borates of RESc3(BO3)4. Interestingly, in our research, we found that the luminescence efficiency of Cr3+ in the CeSc3(BO3)4 host, whose quantum yield was measured at 56%, is several times higher than that in GdSc3(BO3)4, TbSc3(BO3)4, and LuSc3(BO3)4 hosts. Hereby, the energy conversion and transfer in the luminescence of CeSc3(BO3)4:Cr3+ phosphor were examined. The Stokes shift of electron energy conversion within the Cr3+ 4T2g level for the emission at 818 nm and excitation at 625 nm in CeSc3(BO3)4 host was evaluated to be 3775.1 cm-1, and the super-large splitting energy of the 2F5/2 and 2F72 sub-states of the Ce3+ 4f1 state, about 3000 cm-1, was found in CeSc3(BO3)4 host. The typical electronic thermal vibration peaks were observed in the excitation spectra of CeSc3(BO3)4:Cr3+. On this basis, the smallest phonon energy, around 347.7 cm-1, of the CeSc3(BO3)4 host was estimated. Finally, the energy transfer that is responsible for the far higher photoluminescence of Cr3+ in CeSc3(BO3)4 than in other hosts was proven through the way of Ce3+ emission and Cr3+ reabsorption.

Rapid dissolution of chitin and chitosan with degree of deacetylation less than 80% in KOH/urea aqueous solution

The rapid dissolution of chitin and chitosan with degree of deacetylation less than 80% in the universal solvent KOH/urea aqueous solution were comprehensively investigated. A desolvation–intercalation dissolution mechanism was proposed.

Simultaneous capturing phonon and electron dynamics in MXenes

Plasmonic MXenes are of particular interest, because of their unique electron and phonon structures and multiple surface plasmon effects, which are different from traditional plasmonic materials. However, to date, how electronic energy damp to lattice vibrations (phonons) in MXenes has not been unraveled. Here, we employed ultrafast broadband impulsive vibrational spectroscopy to identify the energy damping channels in MXenes (Ti3C2Tx and Mo2CTx). Distinctive from the well-known damping pathways, our results demonstrate a different energy damping channel, in which the Ti3C2Tx plasmonic electron energy transfers to coherent phonons by nonthermal electron mediation after Landau damping, without involving electron-electron scattering. Moreover, electrons are observed to strongly couple with A1g mode (~60 fs, 85–100%) and weakly couple with Eg mode (1–2 ps, 0–15%). Our results provide new insight into the electron-phonon interaction in MXenes, which allows the design of materials enabling efficient manipulation of electron transport and energy conversion.

Utilization of light energy and photodynamic therapy based on thylakoid membranes

<p indent="0mm">The thylakoid membrane, which contains photosynthetic pigments, lipids and proteins, is the main site where the photosynthetic light reaction of green plants, eukaryotic algae and cyanobacteria occurs. Water photolysis and photosynthetic electron transport are two core processes of the light reaction. The former is responsible for converting photons into electrons, and the latter then condenses the energy from the high-potential electrons into energy carriers such as adenosine triphosphate (ATP) and reduced nicotinamide adenine dinucleotide phosphate (NADPH). Due to the electron transport and energy conversion properties of the light reaction, thylakoid membrane can be used in biophotoelectrochemical and biophotoelectrocatalytic systems. Biophotoelectrochemical systems refer to direct or indirect extraction of electrons from the photosynthetic electron transfer chain (PETC) of the thylakoid membrane and transfer the electrons into an external electrode, eventually converting light energy into electric current. Biophotoelectrocatalytic systems refer to the use of ATP and NADPH generated in the light reaction of the thylakoid membrane to drive a series of ATP- or NADPH-dependent biocatalytic reactions. These thylakoid membrane-based light energy utilization systems are featured with material renewability and environmental compatibility. In addition, they show higher energy efficiency than that of the whole photosynthetic-cell systems. Furthermore, thylakoid membranes also hold clear advantages over sub-cellular photosystems, including retention of photosynthetic complexes in their natural environment and relatively simple and fast procedures for their extraction and purification. For biophotoelectrochemical systems, scientists have optimized the electron transfer between the thylakoid membrane and electrode, for example by developing different immobilization methods, or modifying electrode surface with redox polymers and nanomaterials. As an effective platform for cofactor regeneration, the thylakoid membrane-based biophotoelectrocatalytic systems have been used to drive the enzymatic synthesis of poly(3-hydroxybutyrate) (PHB) from acetate, as well as CO₂ fixation through a synthetic crotonyl-coenzyme A (CoA)/ethylmalonyl-CoA/hydroxybutyryl-CoA (CETCH) cycle. In addition to light energy utilization, thylakoid membranes can also be used in photodynamic therapy (PDT) of tumors. Firstly, the photosensitizer porphyrin in the chlorophyll molecules can produce singlet oxygen (¹O₂) from O₂ under visible light irradiation, which in turn kills the tumor cells. Secondly, the photosynthetic oxygen evolution of thylakoid membrane can rapidly supply O₂ <italic>in situ</italic>. Moreover, thylakoid membranes contain abundant catalase, which catalyzes the decomposition of H₂O₂ into O₂, thus further increasing the supply of O₂. This paper summarizes recent progress in the research of thylakoid membranes in these three fields, focusing on the application forms and underlying mechanisms. Moreover, the difficulties and challenges in the application of thylakoid membrane are discussed, and future research directions are prospected. Specifically, developing protective structures such as hydrogels or artificial vesicles to address the issue of short half-life of isolated thylakoid membranes will be crucial. In light of their ingenious energy conversion characteristics and amenability for potential commercialization, thylakoid membrane-based biotechnological systems will have a bright future in the fields of bioenergy, biocatalysis and biomedicine.

Vibrational Spectro-Electrochemistry of Heme Proteins

Heme proteins perform a plethora of distinct cellular functions, including e.g. electron transport (ET), energy conversion, detoxification, catalysis, signaling, and gene regulation, and as such inspire a myriad of biotechnological applications. We use resonance Raman (RR) and Surface enhanced RR (SERR) spectroscopies to probe the architecture of the heme pocket in diverse heme proteins and enzymes, which is essential for the understanding of their physiological properties as well as for the evaluation of their potential for development of the 3rd generation bioelectronic devices (1,2). Moreover, plasmonic metal that gives origin to the surface enhancement of the Raman signal of the molecules found in its close proximity can serve as an electrode, thus driving electrochemical processes. In the case of heme proteins attached to plasmonic Ag electrodes, SERR spectra selectively show vibrational bands originating from the heme moiety only, which are sensitive to spin, coordination and redox state and of the heme iron. These properties that govern the catalytic performance of heme enzymes can be monitored in potential dependent manner by SERR spectro-electrochemistry.We have demonstrated that SERR spectro-electrochemistry possesses unique capacity of to i) disentangle ET processes in multi hemic proteins, such as 28 heme containing nitrite reductase, which represent a challenge for all other experimental approaches and ii) detect subtle immobilization induced structural changes in enzymes of biotechnological interest, which e.g. in the case of cytochrome P450 may prevent their successful applications (1-4). Here we show that SERRS monitoring of electrocatalytic processes by immobilized heme peroxidases, can provide information on catalytically relevant species in situ. Several members of a recently discovered family of heme dye-decolorizing peroxidases (DyPs) that possess remarkable catalytic properties in solution and high biotechnological potential, have been immobilized on biocompatible Ag electrodes. Their structural and electrocatalytic properties studied by RR, SERR spectro-electrochemistry and electrochemistry (2). The immobilized DyP from Pseudomonas putida (PpDyP), in particular, shows native structure and outstanding analytical and catalytic parameters, and hence an exceptional potential for development of 3rd generation biosensors for H2O2 detection. In terms of sensitivity, the bioelectrodes carrying immobilized PpDyP outperform HRP based counterparts reported in the literature (2,4). The biosensor based on a PpDyP variant that harbors mutations at the second shell of the heme cavity reveals further improved storage. Our work highlights the importance of integrated, multidisciplinary approach to simultaneously evaluate the structure and catalytic properties of the enzymes, which ensures faster identification and optimization of the promising candidates for biotechnological applications.

The EDR inflow region of a reconnecting current sheet in the geomagnetic tail

On 6 July 2017, the four Magnetospheric Multiscale spacecrafts were positioned within an electron diffusion region (EDR) just northward of a reconnection X line. The EDR was identified by electron crescent distributions, out-of-plane current, and energy conversion. From this position, the three spacecrafts closest to the X line (within about three electron inertial lengths) were able to accurately measure the reconnection electric field and the electron inflow velocity. The reconnection rates derived from the electric field and inflow velocity measurements agree with theoretical estimates (0.11–0.17) and a previous measurement of EM in a tail reconnection event on 11 July 2017.

Recent Trends in Power Electronics for Renewable energy Systems

The complete world is focused on renewable power to reduce the global energy issue. Power electronic based energy conversion is being used extensively to improve the efficiency of the renewable energy conversion. It has a significant impact on the control and interface of renewable energy systems with both the network and stand-alone applications. As a result, increasing attention is being placed on the design and implementation of power converters. This study discusses the renewable energy systems (wind and solar) and the features of their energy conversion. The fundamental principles underlying their operations are discussed, as well as their recent technological advancements. It is a fact that power electronics is critical for interfacing and thus improving the system capacity.

Research on the photoelectric modulation and resistive switching characteristic of ReSe&lt;sub&gt;2&lt;/sub&gt;/WSe&lt;sub&gt;2&lt;/sub&gt; memtransistor

Memtransistor is a multiterminal device combining the concepts of memristor and field-effect transistor. Two-dimensional Transition Metal Sulfides(TDMS）have unique electronic structure and properties, and they are widely used in electronic devices, energy conversion, memory and other fields. In this paper, a two-dimensional ReSe&lt;sub&gt;2&lt;/sub&gt;/WSe&lt;sub&gt;2&lt;/sub&gt; heterostructure memtransistor was prepared, then the resistive switching characteristics under the electrical modulation, optical modulation, and electric-optical dual gate control are discussed. The results show that the gate control is an effective modulation method, which can change the on/off ratio of the device from 10&lt;sup&gt;1&lt;/sup&gt; ~ 10&lt;sup&gt;5&lt;/sup&gt;. Then, the multi-level resistance and on/off ratio of the memtransistor can be controlled by the change of light wavelength and the illumination power. Moreover, the switching ratio of the device can also be changed in the range of 10&lt;sup&gt;2&lt;/sup&gt; ~ 10&lt;sup&gt;5&lt;/sup&gt; by electric and light dual-gate control, and the reasons for the change of resistance states of the device under different modulation conditions are analyzed. Furthermore, after 225 cycles and 1.9×10&lt;sup&gt;4&lt;/sup&gt; s, the ReSe&lt;sub&gt;2&lt;/sub&gt;/WSe&lt;sub&gt;2&lt;/sub&gt; heterostructure memtransistor still maintains a switch ratio close to 10&lt;sup&gt;4&lt;/sup&gt;, indicating the good stability and durability of the device. It demonstrates that the ReSe&lt;sub&gt;2&lt;/sub&gt;/WSe&lt;sub&gt;2&lt;/sub&gt; memtransistor will be one of potential candidates for the next generation nonvolatile memory applications.

Role of Hydrogen in Catalyst Activation for Plasma-Based Synthesis of Carbon Nanotubes.

The importance of hydrogen in carbon nanotube (CNT) synthesis has been known as it supports the critical processes necessary for CNT growth, such as catalyst reduction. However, within the scope of our mini microplasma CNT synthesis reactor, we found that hydrogen was critical for unexpected reasons. Without hydrogen, CNT growth was inhibited and characterized by amorphous carbon particles. Optical emission spectroscopy of the microplasma revealed that without hydrogen, the high-energy electrons induced the immediate decomposition of carbon feedstock simultaneously with the catalyst feedstock, thus suppressing the formation of catalyst nanoparticles and inducing catalyst deactivation. In contrast, the inclusion of hydrogen induced less-immediate decomposition of reactant gases, through the conversion of electron energy of the plasma to thermal energy, which provided the appropriate conditions for catalyst nanoparticle formation and subsequent CNT nucleation. A simple reaction pathway model was proposed to explain these observed results and underlying mechanisms.