bluuebunny/crossref_metadata_2025 huggingface dataset:
Impact of Carbon Coating on the Electrochemical Property of Li2MnSiO4/C Cathode Material By Sol-Gel Method
Authors: Wang Pin-Han , Chang Chien-Min , Lee Ching-Feng , Chen Hwang-Sheng , Chen-Yang Yui Whei
Published: February 2020

Lithium ion batteries have been widely used on the portable electronic devices due to its high energy density and long cycle life. In order to meets the market requests, various cathode materials such as lithium transition metal oxide (LiMO2, M=Mn、Co) and polyanion cathodes ( LiMPO4,Li2MSiO4, M=Mn、Co、Fe ) have been investigated. The lithium transition metal oxide is easily to be collapsed during the charge-discharge process because of the layer structure. The advantages of polyanion cathodes are the better stability than lithium transition metal oxides due to strong covalent bonds ( ex：P─O、Si─O) and environment more friendly, lower safety risk as well as lower cost. On the other hand, the lithium transition metal orthosilicates, Li2MSiO4 ( M=Fe, Co or Mn), which offers the possibility of two insertion/extraction lithium ions during charge-discharge, have higher theoretical capacity than the phosphate cathode materials and had been considering as promising cathode materials. Moreover, both Li2FeSiO4 and Li2MnSiO4 are more attractive cathode materials among the orthosilicates but Li2MnSiO4 can offer higher power density than Li2FeSiO4 because the Mn2+/Mn3+, Mn3+/Mn4+ redox potential is higher than Fe2+/Fe3+, Fe3+/Fe4+ redox potential.Nevertheless, Li2MnSiO4 also has some drawbacks that include poor electronic conductivity and Jahn-Teller distortion, resulting in collapse of the structure and formation of the amorphous Li2MnSiO4. To solve this problem, following methods have been suggested: 1) decreasing the particle size 2) coating a conductive carbon layer 3) doping transition metal. However, it is found that the characteristics, particle size, morphology etc., of the products are highly dependent on the synthesis method applied.

In this study, the sol-gel method is used with polyvinylpyrrolidone (PVP) as the in-situ carbon coating material to obtain the nanoscale primary particles with lower calcination temperature and without pressure that can lower the cost. Various amounts of PVP are used in Li2MnSiO4 solution for the sol-gel process to adjust the carbon content of the Li2MnSiO4/C cathode materials in the range of 3~6 wt%. The XRD spectra show that all the Li2MnSiO4/C materials synthesized are in Pmn21 structure. The TEM images indicate that a conducting amorphous carbon layer is deposited on the particle surface that improves the electronic conductivity of the Li2MnSiO4 cathode materials. In addition, it is found that the as –prepared LMS/C exhibits high capacity at 0.05C in the voltage of 1.5–4.8V and strong redox peaks in the cyclic-voltammetry curves. This is ascribed to the homogeneous carbon coating and nano-size primary particle that enhances the electronic conductivity and shortens the Li+ ion diffusion path, respectively.

Acknowledgements : The authors gratefully acknowledge the Ministry of Science and Technology, Taiwan, R. O. C. and Chung Yuan Christian University for supporting this research work.
Biomass-Derived Activated Graphene for Electrochemical Capacitors
Authors: Jung SungHoon , Kim TaeYoung
Published: February 2020

We present a scalable method to produce highly porous graphene-based carbons derived from biomass precursors. The process started with polymerization of glucose with salt, during which the polymers are blown by chemically released gas to produce a number of macropores. Subsequently, the polymers were converted into three dimensional macroporous carbons consisting of mono- or few-layered graphene by heating a high temperature. Following this, we further attempted to activate biomass-derived carbons to introduce a number of nanoscale pores on the graphene, thereby achieving a large surface area with hierarchical pore structures. The resulting highly porous biomass-derived carbons were then tested as electrode materials for electrochemical capacitors. The electrochemical performances of the electrode materials will be presented in terms of specific capacitance, energy density and power density.
An Overview of Carbon Nanomaterials in Solid Acid Fuel Cell Electrodes
Authors: Varga Aron , Abel Bernd , Naumov Olga , Xubin Lu , Lohmann Felix , Schulze Patricia , Wagner Maximilian
Published: February 2020

Micro- and nanometer sized carbon materials play an important role as components in low and intermediate temperature fuel cell electrodes. Vulcan carbon, active carbon, etc. have been used as catalyst substrates and electronic interconnect materials. As such, they reduce agglomeration of nanoparticulate catalyst and thus increase long-term stability. The catalyst utilization can be also increased significantly by improving the geometrical distribution of the catalyst. Recently, the drive towards ever smaller electrode structures has shifted attention towards carbon nanotubes (CNTs) and graphene. Their excellent electronic conductivity, extremely high specific surface area, and relatively good stability makes them suitable candidates as fuel cell electrode components. Both the catalyst distribution and utilization have been successfully improved, lowering costs and bringing the technology closer to market application. Importantly, numerous studies have recently shown functionalized CNTs and graphene, without precious metals, to be an effective catalyst for the oxygen reduction reaction. Especially nitrogen doped CNTs and graphene flakes show tremendous potential.1

Solid acid fuel cells based on CsH2PO4 as the solid state electrolyte operate at ca. 240°C and are currently performance limited at the cathode. Here, vulcan carbon has been mainly used as an electronic interconnect and catalyst support.2 Recently, carbon nanotubes have been employed, increasing the mass normalized activity of the Pt catalyst up to 61 S/mgPt.3,4

Here we combine the benefits of recent findings and present new fabrication routes based on spraydrying, metal-organic chemical vapor deposition to create highly active, nanostructured composite electrode materials, based on Pt decorated CNTs and graphene. In addition, we evaluate the suitability of surface functionalized carbon nanomaterials as precious metal free catalyst in solid acid fuel cell cathodes. Functionalization includes plasma treatment and electron beam irradiation under controlled atmospheres. Raman and XPS analysis is used before and after electrochemical measurements to evaluate structural and chemical changes. Data from impedance spectroscopy of symmetric electrochemical cells suggest effective electrochemical activity of CNTs and graphene in solid acid fuel cell cathodes.     

(1)      Gong, K.; Du, F.; Xia, Z.; Durstock, M.; Dai, L. Science
2009, 323, 760.

(2)      Chisholm, C. R. I.; Boysen, D. A.; Papandrew, A. B.; Zecevic, S. K.; Cha, S.; Sasaki, K. A.; Varga, Á.; Giapis, K. P.; Haile, S. M. Interface Magazine
2009, 18, 53.

(3)      Varga, Á.; Pfohl, M.; Brunelli, N. A.; Schreier, M.; Giapis, K. P.; Haile, S. M. Physical chemistry chemical physics : PCCP
2013, 15, 15470.

(4)      Thoi, V. S.; Usiskin, R. E.; Haile, S. M. Chem. Sci.
2015, 6, 1570.
Evaluation of Pt-Au/MWCNT Electrocatalyst Performance As Cathode of a Proton Exchange Membrane Fuel Cell
Authors: Beltrán-Gastélum Mara , Salazar-Gastelum Moises Israel , Félix-Navarro Rosa María , Pérez-Sicairos Sergio , Reynoso-Soto Edgar Alonso , Lin-Ho Shui Wai , Flores-Hernández Roberto , Romero-Castañón Tatiana , Albarrán-Sánchez Irma Lorena , Paraguay-Delgado Francisco
Published: February 2020

The synthesis and characterization of bimetallic electrocatalyst was synthesized and evaluated as cathode in fuel cells to ascertain their performance. The main reactions that take place during the operation of fuel cell are the fuel oxidation reaction at the anodic compartment and the oxygen reduction reaction (ORR) at the cathodic compartment. Although, Pt-based materials have been widely reported as catalysts in both processes, their high cost and low availability has been a strain on the commercialization of fuel cells.

The strategy employed in this work is to synthesize and compare the performance of nanoparticles based on Pt-Au (reduced platinum loading) supported on multiwall carbon nanotubes (MWCNT) materials using reverse microemulsion method (Pt-Au/MWCNT). To effectively compare the performance of the synthesized catalyst material, the catalytic activity of the electrocatalyst was compared to commercial electrocatalyst based on platinum on carbon vulcan (Pt/C).

MWCNT used as support material for the catalysts used in this study were synthesized using spray-pyrolysis. Different characterization techniques were used to determine physicochemical and electrochemical properties of the materials, such as particles size, thermal stability, morphology, composition, active area, catalytic activity, and thermodynamic parameters.

Assemblies were prepared using both the Diffuser Electrode Assembly (DEA), where the catalyst is dispersed onto the diffuser. In spite of the lower Pt loading in the Pt-Au/MWCNT catalyst, the fuel cell assembly results clearly shows that the Pt-Au/MWCNT assembly has approximately twice the power density of the Pt/C assembly, showing the remarkable catalytic ability of the Pt-Au/MWCNT catalyst (Figure 1), in addition to the lower catalyst cost enabled by reduced Pt loading.

Figure 1
(Invited) Application of Carbon Nanotubes in CdTe Photovoltaics
Authors: Khanal Rajendra R. , Phillips Adam B. , Liyanage Geethika K. , Wathage Suneth C. , Song Zhaoning , Stone Jonathan M. , Heben Michael J.
Published: February 2020

Single-wall carbon nanotube (SWCNT) films formed by spray deposition and membrane transfer processes are finding application in a wide variety of different solar cell device architectures.  With a 1.45 eV band gap, a high absorption coefficient, high solar to electric conversion efficiency, and proven low-cost, high-volume manufacturing, CdTe-based photovoltaics are a fast growing technology.  For CdTe photovoltaics, single-wall carbon nanotubes have been shown to provide a low-barrier back contact without the addition of Cu,1 protection against shunts and weak diodes,2 as well as the ability to grow devices in the substrate configuration.3  From a technology point of view, processes to form SWCNTs layers can be readily integrated with conventional CdTe manufacturing processes to provide both cost and performance advantages. Scientifically, the electronic properties of the interface between CdTe and SWCNTs are unusual and allow tunneling contacts to be formed.  This allows flexibility in device design and offers the potential for monolithically integrated thin-film tandems.  We will discuss the use of SWCNT layers in CdTe and other PV devices from both scientific and technology perspectives.

(1) “Wiring-up Carbon Single Wall Nanotubes to Polycrystalline Inorganic Semiconductor Thin Films: Low-Barrier, Copper-Free Back Contact to CdTe Solar Cells”, Phillips, et al., Nano Lett., 2013, 13, pp 5224–5232.

(2) “Simultaneous Shunt Protection and Back Contact Formation for CdTe Solar Cells with Single Wall Carbon Nanotube Layers”, Phillips, et al. Applied Physics Letters, in press. 

(3) “CdTe/CdS Thin Film Solar Cells in the Substrate Configuration on a Single-wall Carbon Nanotube Back Contact”, Khanal, et al., Proceedings of the 39th IEEE Photovoltaics Specialist Conference, pgs. 2013, pp. 1126–1130.
Hybrid Nanomaterials Composed of N-Doped Fullerene/Transition Metal Complex Polymer and P-Doped Conjugated Organic Polymers
Authors: Winkler Krzysztof , Brancewicz Ewa , Wysocka-Zolopa Monika
Published: February 2020

The electron donor/acceptor approach is an effective way to convert solar energy into electrical energy in organic photovoltaic solar cells. The organic conjugated polymers have been widely used as donor constituents. The polymers of C60 and transition metals are good candidates for the electron-accepting components. In the coordination fullerene polymers, C60 moieties are bounded with transition metal atoms or complexes into three-dimensional polymeric network. The most intensively investigated polymer of C60 and palladium atoms, poly-Pd3C60, exhibits an ordered body centered cubic (bcc) structure of fullerene units with a slight rombohedral distortion. The fullerene cage is octohedrally coordinated by six palladium atoms. Each palladium atom is bounded to two C60units.

Hybrid materials composed of n-doped fullerene/transition metal complex polymers and polypyrrole were formed under electrochemical or chemical conditions. The electrochemically synthesis, bilayers of both materials exhibit rectifying characteristics and can serve as a charge trapping system.

The core shell nanoparticles, i.e., poly-Pd3C60@polypyrrole (Figure 1), were prepared by sequential chemical polymerization of both components. These systems can be used for the modeling of the charge transfer processes in bulk-heterojunction solar devices. The outer polypyrrole layer is easily oxidized at potentials corresponding to the potentials of pure polypyrrole oxidation. The poly-Pd3C60 core reduction is shifted toward more negative potentials in comparison to the potential of reduction of pure poly-Pd3C60. The electrochemical measurements reveal that poly-Pd3C60@polypyrrole with outer polypyrrole layer doped with light harvesting molecules and thinner than about 20 nm can be potentially used in solar energy conversion electrochemical devices. The small thickness of the outer layer prevents free charge carriers recombination. The large area of p-n nanojunction in nanostructured material should increase efficiency of solar energy conversion. The electric charge formed at the p-n nanojunction can be also transferred from poly-Pd3C60inner sphere to the metallic collector.

Figure 1
(Invited) Insight into Carbon Nanotube Surface Structures for PV Applications
Authors: Doorn Stephen K. , Hartmann Nicolai F. , Subbaiyan Navaneetha K , Pramanik Rajib , Mallajosyula Arun Tej , Mohite Aditya , Dowgiallo Anne-Marie , Blackburn Jeffrey L.
Published: February 2020

Carbon nanotube (CNT) surface chemistry and surface structures impact their potential roles in photovoltaics in a number of ways.  These include defining chirality-specific segregation behaviors that enable isolation of the required pure chiralities.  Surface structures also define film morphologies and ordering that ultimately determine how intertube interactions facilitate or inhibit charge and energy flow.  We present photoluminescence imaging results as a direct probe of these relevant surface structures. A demonstration of phase-dependent segregation in surfactant compositions at the nanotube surface will be shown as a determining factor in the mechanism of new aqueous two-phase separations approaches.  We will also show how variations in polyfluorene polymer structures impact their surface morphologies, ultimately determining the ability to transport excitation energy and charge within thin-film nanotube-based PV devices.
N-Doping of Single-Walled Carbon Nanotubes and Their Thermoelectric Property
Authors: Fujigaya Tsuyohiko , Huang Wenxin , Nakashima Yuki , Nakashima Naotoshi
Published: February 2020

Thermoelectric conversion is one of the key technology to develop a battery for wearable device. Recently, single-walled carbon nanotubes (SWNTs) have attracted much attention as substitutes due to their lower cost, ease of fabrication, flexibility, light weight and large Seebeck coefficient. While SWNTs are promising p-type organic thermoelectric materials, the development of the flexible n-type thermoelectric materials is still challenging even at present, because n-type semiconducting organic materials are inherently unstable in air due to oxidation. In this study, we developed n-type SWNT sheet by doping of small molecules.
(Invited) Electrochemical Capacitors Based on Graphene
Authors: Kaner Richard B. , El-Kady Maher , Shao Yuanlong , Hwang Jee Youn , Wang Lisa , Li Mengping , Wang Haosen , Kowal Matthew , Sun Wanmei , Cho Sunghun , Rizvi Reza
Published: February 2020

Electrochemical capacitors, also known as supercapacitors, are energy storage devices like batteries, yet they can be recharged a hundred to a thousand times faster. Because of their enabling features, supercapacitors are replacing batteries and capacitors in an increasing number of applications. Their high power density and excellent low temperature performance have made them the technology of choice for back-up power, cold starting, flash cameras and regenerative braking. They also play an important role in the progress of hybrid and electric vehicles. However, the low energy density of current supercapacitors is the main impediment to realizing the full commercial potential of this technology. This has triggered tremendous research efforts in order to develop new electrode materials that are capable of providing a huge amount of energy in a short period of time. In this talk, we will discuss the current status of graphene-based supercapacitors, highlight ongoing research activities and present challenges that must be addressed in the future. Several examples will be given on the rational design and fabrication of electrodes with the goal of making compact, reliable and energy dense supercapacitors that are mechanically flexible and possess both long cycle life and calendar life.
Supercapacitors
Authors: Chowdhury Tazima , Grebel Haim
Published: February 2020

In our studies, gate electrodes were placed in mid-position between the anode and the cathode of electrolytic capacitors.  Ionic currents were made to flow through these gate electrodes.  The gate was an electronic p-n junction and consisted of p-type and n-type functionalized carbon nanotubes (CNT).  Chrono-potentiometry and electrochemical impedance spectroscopy revealed the effect of the gate electrode on the overall cell's capacitance.  Current-Voltage measurements (I-V curves) were made on dry samples, which were consisted of p-type and n-type CNT layers.  These data clearly exhibited an electronic diode-like gate characteristics.  Cyclic voltammetry (CV) with two-electrode system configuration was carried out at room temperature and using 1 M NaCl as an electrolyte. 

The electrolytic cell capacitance was assessed while biasing the gate voltage in the range of -15 mV to +15 mV.  This small bias was enough to substantially increase the cell capacitance. 

[1]   Y. Zhang, H. Grebel, “Controlling Ionic Currents with Transistor-like Structure”, ECS Transactions 2 (18). 2007

[2]   S. Sreevatsa, H. Grebel, “Carbon Nanotube Structures as Ionic Barriers: A New Corrosion Prevention Concept”, ECS Transactions 19 (29) 91-100. 2009

[3]   T. Chowdhury and H. Grebel, "Effect of Gate Electrode in Electrochemical Cells", Session B01: Energy Storage: Batteries and Supercapacitors, Abstract MA2015-01 721, 227 ECS Annual Meeting, Chicago, IL, (May 2015).
One-Pot Electrochemical Exfoliation and Functionalization of Graphene Sheets
Authors: Ossonon Diby Benjamin , Bélanger Daniel
Published: February 2020

Graphene is currently attracting a lot of interest because of their potential applications in several different fields. Various approaches are being developed to prepare it at large-scale, by green method and cost-effectively. To this end, graphene sheets can be prepared by electrochemical exfoliation of graphite in aqueous electrolyte. In this work, graphene was produced by electrochemical exfoliation of graphite in acidic and neutral electrolytes. With this procedure, graphene sheets with low oxygen content are produced. Graphene sheets were also functionalized during the electrochemical exfoliation process by using appropriate reagents and experimental conditions. The resulting materials were characterized by several techniques such as Fourier transform infrared, X-ray photoelectron and Raman spectroscopy, thermogravimetric analysis, elemental analysis, electronic conductivity measurements and electrochemical techniques.
Influence of Steam Pretreatment on Surface and Electrochemical Properties of Activated Carbon Electrode: High Performance Supercapacitors
Authors: Li Zhen-Yu , Bui Phuong T. M. , Akhtar M. Shaheer , Yang O-Bong
Published: February 2020

Carbon materials especially, activated carbons emerge as an important industrial materials for various applications like energy storage, electronics, photovoltaic etc. owing to their high specific surface area, good porosity and electrocatalytic nature. Activated carbon (AC) materials are commonly used as the electro-active materials in electrochemical double layer capacitor (EDLC) because it is less expensive and excellent chemical/mechanical stability. In this paper, highly controlled steam pretreatment was employed to improve the surface properties of activated carbon (AC) and extensively applied as electrode materials for supercapacitor. The steam pretreatment at 700oC followed by H2 gasification was found to be optimal temperature for achieving the high surface area, pore size and pore volume of AC. FTIR and XPS analysis revealed the significant reduction in hydroxyl groups after H2 gasification during the steam pretreatment on AC. The electrochemical characterizations aroused the considerable improvement in the electrocatalytic and capacitive properties of AC electrode after the steam pretreatment at 700oC. The supercapacitor based on bare AC electrode exhibited low capacitance of 155.2 F/g whereas supercapacitor based steam-AC/700oC electrode showed the appreciably increment in the capacitance of 187.2 F/g which might be due to improve surface area, and pore volume. The steam-AC/700oC electrode presented the excellent stability by recording 92% of initial capacity after 1000 cycles.
Surface Electrochemical Degradation Characterization of Carbon Fibers in Aqueous Electrolytes
Authors: Heydarzadeh Sheykhangafsheh Zahra , Wang Yun
Published: February 2020

Electrolysis of water is the decomposition of water (H2O) into oxygen (O2) and hydrogen gas (H2) due to an electric current being passed through the water. In pure water at the negatively charged cathode, a reduction reaction takes place, with electrons (e−) from the cathode being given to hydrogen cations to form hydrogen gas (the half reaction balanced with acid):

     Reduction at cathode: 4H+(aq) + 4e-→ H2(g)

At the positively charged anode, an oxidation reaction occurs, generating oxygen gas and giving electrons to the anode to complete the circuit:

     Oxidation at anode: 2H2O(l) → O2(g) + 4 H+(aq) + 4e-

Carbon is a widely used electrode material for electrolysis of water due to its excellent electric conductivity and electrochemical stability. Carbon material may also subject to degradation under severe electrochemical environments due to radical attack and electrolysis of carbon. The present work is to study the carbon electrode degradation during electrolysis of water with a focus on the surface characterization. The net reaction of electrochemical gasification of carbons during water electrolysis is:

     Net Reaction: C(s) + 2H2O(l) → CO2 (g) +2H2 (g)

Experimental results show that the surface area of carbon cloth electrodes after water electrolysis changes by up to 50 times depends on the working condition.The experimental setup employed in this study is shown in Fig. 1. The effect of various parameters, including operating temperature, voltages and also time durations of water electrolysis, on the carbon surface cloth is investigated to determine the optimum working condition. The analysis was done using H2SO4 solution as an electrolyte with 25% concentration and a three-electrode cell was used to measure the capacitance of a single electrode by cyclic charge/discharge (CCD) technique.

Figure 1
Tuning Single-Walled Carbon Nanotube (SWCNT) Membrane Interactions
Authors: Antonucci Alessandra , Schuergers Nils , Boghossian Ardemis Anoush
Published: February 2020

The remarkable physicochemical properties of carbon nanomaterials make them promising candidates for biomedical and biotechnological applications. In particular, the distinctive optical and structural characteristics of single-walled carbon nanotubes (SWCNTs) have inspired the development of biologically applicable optical sensors and molecular delivery scaffolds1,2. Several studies have largely focused on enabling cell uptake of SWCNTs by engineering the SWCNT surface through non-covalent side-wall functionalizations. Non-covalent functionalization with a rich variety of biomolecules and polymers has been shown to potentially increase SWCNTs solubility and membrane translocation while endowing these nanostructures with enhanced biocompatibility3. These functionalizations have been engineered to permit SWCNT uptake by a variety of mammalian cells through both passive and energy-dependent pathways. Most recently, this platform was applied to intact chloroplasts to augment their photosynthetic capability in novel nanobionic devices4. Although factors such as cell type, functionalization zeta-potential, particle size, and membrane composition have been shown to affect uptake, these findings have largely relied on empirical approaches towards engineering uptake mechanisms5,6.

Our work builds on these empirical findings to establish engineering design rules for enabling SWCNT-membrane interactions. We performed a systematic investigation of the effect of SWCNT functionalization on membrane penetration properties using a novel biological host. The results of this study were used to not only elucidate the underlying interaction on a molecular level, but also develop the first of a new generation of light-harvesting nanobionic devices.

References:

1. Boghossian, A. a. et al. Near-infrared fluorescent sensors based on single-walled carbon nanotubes for life sciences applications. ChemSusChem
4, 848–863 (2011).

2. Oliveira, S. F. et al. Protein Functionalized Carbon Nanomaterials for Biomedical Applications. Carbon N. Y. (2015).

3. Vardharajula, S. et al. Functionalized carbon nanotubes: biomedical applications. Int. J. Nanomedicine
7, 5361–74 (2012).

4. Giraldo, J. P. et al. Plant nanobionics approach to augment photosynthesis and biochemical sensing. Nat. Mater.
13, 400–8 (2014).

5. Kostarelos, K. et al. Cellular uptake of functionalized carbon nanotubes is independent of functional group and cell type. Nat. Nanotechnol.
2, 108–113 (2007).

6. Holt, B. D., Dahl, K. N., Islam, M. F. & Al, H. E. T. Cells Take up and Recover from Nanotubes with Two Distinct Rates. 3481–3490 (2012)
Producing Supercapacitor Wire Electrode Via a Simple Self-Assembly Technology
Authors: Huang Wilson Hou-Sheng
Published: February 2020

Recently, a wearable application is the most popular technology for daily life and health care. However, an excellent wearable electrical device should be matched with an effective, convenient, and flexible energy source. Therefore, we developed a kind of energy device technology with wire supercapacitor. Graphene oxide (GO) was the main material, which has high specific surface characteristics and excellent electrical conductivity behavior. The hydrophilic functional group on GO surface enhanced the transfer of electrolyte. We added the modified single-walled carbon nanotubes (SWCNT), as the sheet of graphene oxide concatenates the bridge, which supplied the stronger physical behavior. We synthesize supercapacitor wire electrode via a high-pressure and high-temperature technology. This study had been produced with a diameter of 25 – 50 μm supercapacitor wire electrodes and the capacity is around 2.72 mF/cm2 by a three-electrode electrochemical experiment in 0.5 M sulfuric acid aqueous.

Figure 1
Highly Efficient Graphene Supports for Fuel Cell Electrocatalysts
Authors: Sadhu Veera , Jamil Esaam , Alkan Gursel Selmiye
Published: February 2020

Graphene nanomaterials are increasingly important with their distinct properties such as high electrical conductivity, high contact surface area and enormous stability. Therefore, graphene has been used as promising catalyst support in energy conversion and storage systems. In order to achieve high catalytic activity a specifically guided growth of catalyst on graphene support surface with delicate controllability is highly preferred. Therefore, we modify graphene surface in two different ways such as graphene functionalization with various active functional groups and fabrication of nanocomposites with intrinsically conducting polymers e.g. polypyrrole (PPy). We have successfully modified graphene oxide by the functionalization with free amine groups (GO-NH2), RGD peptide (GO-RGD) and Nitrogen doping (N-GO). Platinum (Pt) catalyst nanoparticles have been deposited on these functionalized GO (f-GO) using ethylene glycol modified method. The dispersion of Pt deposited F-GO has been enhanced and stable optimized dispersions in organic solvents were obtained. The cyclic voltametry (CV) results showed a high electrochemical surface area (ECSA) of 147 m2/g for GO-RGD compared to Pt/carbon black (Pt/C, 80 m2/gPt) and Pt/GO (99 m2/gPt). On the other hand, we also fabricated GO/PPy/CB (carbon black) hybrid nanocomposites as catalyst support and deposited Pt catalyst nanoparticles. The CV results showed a high ECSA of 153 m2/gPt. These modified graphene nanomaterials including Pt/f-GO and hybrid composites have been successfully used in proton exchange membrane fuel cell (PEMFC) electrodes. The Pt nanoparticles distribution on various modified graphene surfaces, which may significantly influence their properties such as electrical conductivity, electrocatalytic activity when they used as catalyst support and fuel cell performance will be discussed more in details.
Precious-Metal-Free Carbon Nano Fiber with N-Doped Graphene Nanoplatelets As Electrocatalyst for Oxygen Reduction Reaction
Authors: Yoo Seonyoung , Shin Jeeyoung , Kim Guntae
Published: February 2020

The development of highly active and stable catalysts for the oxygen reduction reaction (ORR) is an important task in the practical application of metal-air batteries and fuel cells. Carbon nanomaterials doped with heteroatoms, such as N and S, are attractive materials for use as electrocatalysts toward the ORR due to their low cost, high efficiency and high durability. Herein we report carbon nanofiber (CNF) incorporated Fe-N-doped graphene nano platelets (Fe@NGnP) prepared as a catalyst via a novel and simple synthesis approach. The activated CNF-Fe@NGnP catalysts exhibit substantially improved activity for oxygen reduction compared to that of currently used carbon blacks and Pt/carbon catalysts.
(Invited) Spectral Triangulation: A Novel 3D Method for Locating Single-Walled Carbon Nanotubes In Vivo
Authors: Lin Ching-Wei , Weisman R. Bruce , Bachilo Sergei M. , Vu Michael , Beckingham Kathleen M.
Published: February 2020

Nanomaterials with luminescence in the short-wave infrared (SWIR) region are of special interest for biological research and medical diagnostics because of relatively favorable tissue transparency in that region. Single-walled carbon nanotubes (SWCNTs) show sharp SWIR spectral signatures and therefore have the potential for noninvasive detection and imaging of cancerous tumors when linked to selective targeting agents such as antibodies. However, such applications face the challenge of detecting and localizing the source of light emission from inside tissues. We present here a new method, called spectral triangulation, for sensitively locating SWCNT emission sources in three dimensions using only optical measurements at the specimen surface. SWCNTs inside tissue phantoms are excited by an LED array, and resulting SWIR emission is captured by a scanning fiber optic probe coupled to an InGaAs spectrometer or avalanche photodiode detector. Because of water absorption, attenuation of the SWCNT fluorescence in tissues is strongly wavelength-dependent. We can therefore gauge the distance between SWCNTs and probe by analyzing differential changes in the measured SWCNT emission spectra. SWCNT fluorescence is clearly detected though as much as 22.5 mm of tissue phantom, and the three-dimensional locations of SWCNT samples are deduced with sub-millimeter accuracy at depths up to 10 mm. Our method can also distinguish and locate dual SWCNT sources within tissues.
Carbon Nanotube Photoluminescence Modulation for Bioanalytical Measurements
Authors: Heller Daniel A , Jena Prakrit Vaibhav , Roxbury Daniel , Budhathoki-Uprety Januka , Williams Ryan M. , Shamay Yosef , Shah Janki , Harvey Jackson Dean , Horoszko Christopher , Langenbacher Rachel E , Galassi Thomas Vito
Published: February 2020

The real-time and spatially-resolved detection and identification of analytes in biological media present important goals for next-generation nanoscale probes and sensors. To this end, we employ the intrinsic near-infrared fluorescence of single-walled carbon nanotubes which is photostable yet sensitive to the immediate environment. Analyte identification is achieved by modulation of the nanotube’s spectral response, resulting in distinct optical fingerprints. We transiently map the nanotube emission responses spatially in live cells and tissues, facilitating unprecedented bioanalytical measurements.
(The Roger Taylor Award Address) Wrapped up in Nanotubes: Probing Photoluminescence Dynamics of Wrapped Single-Walled Carbon Nanotubes (SWCNTs)
Authors: Boghossian Ardemis Anoush
Published: February 2020

The last decade has realized an onset of novel optical, SWCNT-based sensors that have been crucial in shaping a distinct generation of unconventional analytical tools. These optical nanosensors exploit the advantageous fluorescence properties of semiconducting SWCNTs, which benefit from stable and sensitive near-infrared emissions capable of deep-tissue sensing and imaging applications. SWCNTs are non-covalently wrapped in a variety of chemical moeities, including DNA, polymers, and proteins, that impart the SWCNT with selectivity towards specific analytes of interest. Recent research endeavors have largely focused on designing wrappings that control the sensor's selectivity by modulating the surface coverage of the nanotube in the presence of an analyte. In addition to selectivity, these wrappings also modulate fluorescence properties such as emission intensity; properties that play an integral role in determining the sensitivity limits of these sensors. We have developed a model that explores the perturbations of SWCNT fluorescence emissions in the presence of a wrapping. By de-coupling the structural and chemical contributions of the polymer wrapping and challenging underlying assumptions of uni-dimensional contributions, this model enables a comparative approach towards achieving design rules for the rational engineering of sensor wrappings.
(Invited) In Vivo Carbon Nanotube Sensors
Authors: Iverson Nicole M , Bisker Gili , Farias Edgardo , Ivanov Vsevolod , Ahn Jiyoung , Barone Paul W , Shandell Mia , Trudel Laura J , Sen Selda , Sen Fatih , Atolia Esha , Wogan Gerald N , Strano Michael S
Published: February 2020

Single-walled carbon nanotubes (SWNT) are particularly attractive for biomedical applications because they exhibit unique optical properties, fluorescing in the near infrared tissue transparency window, and allow for information transfer without the need for an internal power source. Although SWNT have been used as highly-sensitive detectors for various compounds, their use as in vivo biomarkers requires the simultaneous optimization of multiple parameters, including molecular recognition, biocompatibility, high fluorescence quantum efficiency and signal transduction. This work demonstrates two SWNT delivery mechanisms for in vivo detection of an inflammatory factor, nitric oxide (NO), that is associated with numerous diseases, including cancer, but is poorly understood due to its fast degradation rate and the lack of detection devices.  First, a polyethylene glycol ligated copolymer is shown to stabilize SWNT sensors in physiological solutions, enabling an intravenous injection into mice.  Second, a subcutaneous implant is investigated, with multiple SWNT concentrations, hydrogel shapes and sizes, and the gel’s physical properties examined to determine the preferred material for implantation.  We found that both the injected and implanted SWNT are able to detect inflammation within an animal, thus providing the first demonstration of in vivo SWNT sensors as well as the first long term in vivo NO detection modality.  This work demonstrates the ability of SWNT sensors to be utilized for in vivo data collection and possibly a wide range of biomedical applications.
Sub-Cellular Localization of Photoluminescent Single-Walled Carbon Nanotubes in Human Cancer Cells
Authors: Budhathoki-Uprety Januka , Langenbacher Rachel E , Jena Prakrit Vaibhav , Roxbury Daniel , Heller Daniel A
Published: February 2020

Since the onset and progression of cancer and many other diseases involve dysregulation of certain sub-cellular compartments, accurate visualization of events using probes localized in sub-cellular organelles would facilitate the understanding of disease processes. Molecular probes based on single-walled carbon nanotubes (SWCNTs) are ideal for imaging and molecular sensing with spatio-temporal resolution due to their non-bleaching photoluminescence in the near infrared region—the optical regime where interference is minimal from absorption and scattering of light in biological specimens. Achieving specificity in sub-cellular localization of nanoscale optical probes is often challenging but can be mediated by surface chemistry. We cloaked SWCNTs in polycarbodiimide polymers to suspend them in aqueous environments and to integrate biocompatible functionalities. The polymers preserved nanotube photoluminescence while promoting their localization in sub-cellular spaces of cultured human cancer cells without cytotoxicity.
Antibacterial Mechanisms of Nano-Graphene Oxide By Measuring Membrane Interactions
Authors: Robb Sarah M. , Li Maxwell , Dahl Kris Noel , Islam Mohammad F.
Published: February 2020

Bacterial resistance to traditional small molecule antibiotics has led to the need for antimicrobial agents that use an alternative mechanism to kill or inhibit bacterial growth. A promising material for this application is graphene oxide (GO), but the reports of the antibacterial activity have varied.  Also, the mechanisms of antibacterial activity are uncertain, but there are three proposed theories: (i) the edges of the 2D sheets lyse and disrupt the bacterial membrane, (ii) the sheets cover the cell and limit access to vital nutrients, and (iii) GO causes metabolic oxidative stress to the cells. In this study, we investigated the effect of GO’s size on its antimicrobial effects by measuring growth of planktonic Escherichia coli (E. coli) with exposure to GO. We have found nanometer-sized GO (nGO) significantly inhibit the growth of E. coli, but micrometer-sized GO (µGO) did not significantly inhibit E. coli growth, showing GO antibacterial efficacy to be dependent on physicochemical properties. In treating human cells in culture with similar concentrations of GO we find that neither µGO nor nGO had toxic or deleterious impacts on cell function. One major difference between bacteria and human cells is membrane composition and mechanics. To investigate the interaction on a molecular level, we exposed lipid membrane vesicles to µGO and nGO. Altered lipid composition and tension allow us to investigate the membrane impacts in a controlled way. Overall, this knowledge will be informative for the design of future biomaterials to prevent bacterial growth and infections with little impact on human cells.
Pyrolized 3D Carbon Scaffolds and Electrical Stimulation Enhance Differentiation of Neurons
Authors: Perebikovsky Alexandra , Madou Marc J
Published: February 2020

In recent years, carbon materials have been increasingly utilized in biomedical applications. The use of carbon has several advantages: carbon microstructures are inexpensive and easy to fabricate, they have tunable surface properties, and 3-D carbon microstructures can be fabricated to mimic the in vivo biological environment. In this work, pyrolyzed three-dimensional carbon micropillar electrodes are used as a substrate to electrically stimulate and grow mouse neuronal stem cells (NSC’s). The micropillar electrodes are fabricated by controlled pyrolysis of SU-8, a polymeric photoresist. NSC’s are seeded on the micropillar array and daily DC electrical stimulation is applied. Application of 10 mV of DC electrical stimulation for 15 minutes a day is shown to increase differentiation of NSCs toward dopaminergic lineages and to increase neurite outgrowth when compared to NSC’s grown on conventional tissue culture plates. Furthermore, a microfluidic disc is used to create a controlled flow of byproducts from differentiated NSCs toward a detection chamber. A separate, three dimensional carbon interdigitated electrode array, also fabricated using SU-8 and conventional photolithography techniques, is placed into the detection chamber and uses redox amplification to selectively detect dopamine. The success of the 3D carbon micropillar electrodes in inducing spontaneous differentiation of NSC's toward dopaminergic lineages, along with the implementation of electrochemical detection of dopamine on a microfluidic disc, demonstrates the efficiency of the platform as a stem cell culture and detection device.
Selective Desorption of Multiple High-Purity SWCNT Fractions from Hydrogels through Co-Surfactant Modulation
Authors: Zhao Yang , Clar Justin , Li Luping , Xu Jia , Yuan Tianyu , Bonzongo Jean-Claude J , Ziegler Kirk J
Published: February 2020

The post-synthetic separation of single walled carbon nanotubes (SWCNTs) has been studied with great interest in the past decade. While high-fidelity separations of SWCNTs by their (n,m) type have been demonstrated, a simple, high-throughput method is still desired. Our previous work has highlighted the importance of surfactant structure along SWCNT sidewalls in the separation mechanism. Here we report the selective desorption of a wide range of single-chirality (n,m) fractions in a single hydrogel-packed column. High-purity fractions of (n,m) nanotubes are obtained with high yield once a specific ratio of sodium dodecyl sulfate (SDS)/sodium deoxycholate (DOC) co-surfactant solution is used. The differences between the co-surfactant ratios needed to separate two (n,m) species can sometime be very small. The separation can be obtained under a wide variety of co-surfactant background concentrations. However, better separations are achieved at higher background concentrations.
Design and Synthesis of Mwcnts Discrete 3D Microparticles for the Organized Assembly of High Performance Materials
Authors: Maggini Laura , De Volder Michael F. L.
Published: February 2020

The remarkable mechanical, electrical, thermal and optical properties of carbon nanotubes (CNTs) are only valid for individual particles, and are generally lost when bulk CNT materials are integrated in devices.[1-3] The controlled manufacturing of macroscopic functional and high-performance CNT-materials, retaining the compelling properties of individual tubes, has hence become of paramount importance to allow their full exploitation within commercial products.

Herein we report an unprecedented sequential engineering of the architecture of CNT materials, from the nano-, to the micro- and macroscale level. Specifically, we report on a a microfluidic assisted methodology to generate discrete 3D CNT microparticles, to be employed in large area self-assembly processes, enabling a high degree of hierarchization and tailoring of the CNT material.

Such controlled multiscale engineering, paves the way for the implementation of a property-conservative manufacturing of CNT-based materials, boosting their performance–to–cost ratio, and integration in a vast set of applications with high societal and industrial impact, such as high performance filters, catalysts, and energy storage devices.

Figure 1
Rotaxanes Meet Carbon Nanotubes. Synthesis and Physical Properties of Mechanically Interlocked Derivatives of Carbon Nanotubes
Authors: Perez Emilio M
Published: February 2020

Extensive research has been devoted to the chemical manipulation of carbon nanotubes. The attachment of molecular fragments through covalent-bond formation produces kinetically stable products, but implies the saturation of some of the C-C double bonds of the nanotubes.[1] Supramolecular modification maintains the structure of the SWNTs but yields labile species.[2] Here, we present a strategy for the synthesis of mechanically interlocked derivatives of SWNTs (MINTs).[3] In the key rotaxane-forming step, we employed macrocycle precursors equipped with two recognition units and terminated with bisalkenes that were closed around the nanotubes through ring-closing metathesis. The mechanically interlocked nature of the derivatives is probed by analytical, spectroscopic, and microscopic techniques, as well as by appropriate control experiments.[4,5] Remarkably, bulk reaction data confirm the interlocked nature of MINTs.[6] Comprehensive photophysical, electrochemical and theoretical characterization experiments indicate that the formation of MINTs goes hand in hand with distinct effects on the physical properties of both the carbon nanotubes and the macrocycles, clearly different from what is found in non-interlocked supramolecular references. The changes affect fundamental properties, such as solubility, diffusion coefficient, and electronic interaction between macrocycles and nanotubes.[7]

[1] Singh, P.; Campidelli, S.; Giordani, S.; Bonifazi, D.; Bianco, A.; Prato, M. Chem. Soc. Rev.
2009, 38, 2214.

[2] Zhao, Y.-L.; Stoddart, J. F. Acc. Chem. Res.
2009, 42, 1161.

[3] de Juan, A.; Pérez, E. M. Nanoscale
2013, 5, 141.

[4] de Juan, A.; Pouillon, Y.; Ruiz-González, L.; Torres-Pardo, A.; Casado, S.; Martín, N.; Rubio, A.; Pérez, E. M. Angew. Chem., Int. Ed.
2014, 53, 5394. (Highlighted in Chem&Eng News, 2014, 92, 31.)

[5] López-Moreno, A.; Pérez, E. M. Chem. Commun., 2015, 51, 5421

[6] de Juan, A.; Bernal, M. M.; Pérez, E. M. ChemPlusChem, 
2015, 80, 1153.

[7]  Martínez-Periñán, E.; de Juan, A.; Pouillon, Y.; Martín, N.; Schierl, C.; Strauss, V.; Rubio, A.; Guldi, D.; Lorenzo, E.; and Pérez, E. M. submitted

Figure 1