bluuebunny/crossref_metadata_2025 huggingface dataset:
(Invited) Optoelectronic Properties and Electromechanical Resonance Behavior in Individual Suspended Carbon Nanotube Pn-Junctions and Devices
Authors: Cronin Stephen B.
Published: February 2020

In carbon nanotubes pn-junctions, we observe Zener tunneling behavior and photocurrent generation in quasi-metallic nanotubes1, which have smaller band gaps than most known bulk semiconductors. These carbon nanotube-based devices deviate from conventional bulk semiconductor device behavior due to their low dimensional nature. We observe rectifying behavior based on Zener tunneling of ballistic carriers instead of ideal diode behavior, as limited by the diffusive transport of carriers. We observe substantial photocurrents at room temperature, suggesting that these quasi-metallic pn-devices may have a broader impact in optoelectronic devices. We also explore the role of weak clamping forces, typically assumed to be inﬁnite, in the electromechanical resonance behavior of these suspended carbon nanotubes.2 Due to these forces, we observe a hysteretic clamping and unclamping of the nanotube device that results in a discrete drop in the mechanical resonance frequency on the order of 5−20 MHz, when the temperature is cycled between 340 and 375 K. This instability in the resonant frequency results from the nanotube unpinning from the electrode/trench sidewall where it is bound weakly by van der Waals forces. Interestingly, this unpinning does not aﬀect the Q-factor of the resonance, since the clamping is still governed by van der Waals forces above and below the unpinning. For a 1 μm device, the drop observed in resonance frequency corresponds to a change in nanotube length of approximately 50−65 nm. On the basis of these ﬁndings, we introduce a new model, which includes a ﬁnite tension around zero gate voltage due to van der Waals forces and shows better agreement with the experimental data than the perfect clamping model. From the gate dependence of the mechanical resonance frequency, we extract the van der Waals clamping force to be 1.8 pN. The mechanical resonance frequency exhibits a striking temperature dependence below 200 K attributed to a temperature-dependent slack arising from the competition between the van der Waals force and the thermal ﬂuctuations in the suspended nanotube.

1.    Amer, M.R., S.-W. Chang, R. Dhall, J. Qiu and S. Cronin, “Zener Tunneling and Photocurrent Generation in Quasi-Metallic Carbon Nanotube pn-Devices” Nano Letters, 13, 5129 (2013).

2.   Mehmet Aykol, Bingya Hou, Rohan Dhall, Shun-Wen Chang, William Branham, Jing Qiu, and Stephen Cronin, "Clamping Instability and van der Waals Forces in Carbon Nanotube Mechanical Resonators" Nano Letters, 14, 2426 (2014).

3.   Shun-Wen Chang, Kevin Bergemann, Rohan Dhall, Jeramy Zimmerman, Stephen Forrest, Stephen Cronin, "Non-ideal Diode Behavior and Band Gap Renormalization in Carbon Nanotube P-N Junctions" IEEE Transactions on Nanotechnology, 13, 41 (2014).
(Invited) Scalable Assembly and Alignment of Highly Electronic-Type Purified Semiconducting Carbon Nanotubes for High Performance Field Effect Transistors
Authors: Arnold Michael S. , Brady Gerald J , Joo Yongho , Wu Meng-Yin , Shea Matthew J , Gopalan Padma
Published: February 2020

We have pioneered a scalable approach for depositing aligned arrays of ultrahigh purity semiconducting SWCNTs (prepared using polyfluorene-derivatives) called floating evaporative self-assembly (FESA). In this talk, we will first present on the scaling and physics of FESA. We will then present on high performance field effect transistors (FETs) fabricated from the arrays. FESA is exploited to create FETs with exceptionally high combined on-conductance and on-off ratio of 261 μS/μm and 2x105, respectively, for a channel length of 240 nm. This is 1400x greater on-off ratio than SWCNT FETs fabricated by other methods, at comparable on-conductance per width of ~250 µS/µm, and 30-100x greater on-conductance per width, at comparable on-off ratio of 105-107.
Covalent Chemistry on Carbon Nanotubes: From Electronic Fundamentals to Sensor Applications
Authors: Bouilly Delphine , Martel Richard , Nuckolls Colin
Published: February 2020

Carbon nanotube devices are particularly well-suited to build chemical or biological electronic nanosensors due to their inherent nanoscale channel, exceptional electrical conductance and high sensitivity to charge transfer. This charge sensitivity is mostly unselective though, which means that functionality must be added to the nanotube sidewall in order to tailor its affinity to specific chemical species.  Single-point functionalization is particularly desirable to allow probing molecules at the individual level. Among the various functionalization types available for carbon nanotubes, covalent chemistry provides the most robustness and reproducibility. However, its invasive nature is known to alter the electronic performance of the nanotubes, and achieving single-point covalent binding on pristine nanotubes is challenging.

Here we present experimental work providing fundamental insight of the impact of covalent reactions on carbon nanotubes electronic properties, as well as recent advances on the use of covalently chemistry for assembling single-molecule nanosensors. First, electrical transport experiments are used to probe the electronic states of carbon nanotubes fully covered with covalent adducts. Results on numerous individual nanotube devices show that addition of monovalent groups such as aryl derivatives severely disrupt the nanotube electronic bands and also generate graft-induced localized states in the nanotube band gap [1]. Oppositely, divalent grafting using carbene-based addition reactions is found to leave the nanotube electronic properties unaltered [2]. We discuss the mechanisms behind these results based on symmetry and conjugation considerations. Second, high-resolution lithography patterning and aryldiazonium chemistry are used to add covalent adducts on various portions of carbon nanotubes devices, from several microns down to 20-nm segments. The intensity of conductance alteration is found to scale exponentially with the length of the exposed segment, with large variations in decay constants between devices. All devices nevertheless present a robust 20% current drop for the shortest exposed segments, which points to a consistent small number of binding sites. Finally, we demonstrate the ability of this approach to bind few molecules onto carbon nanotubes with controlled position and high yield over arrays of hundreds of devices, which opens a very promising route for assembling a variety of carbon-nanotube-based single-molecule electronic nanosensors.

[1] D. Bouilly, J. Laflamme-Janssen, J. Cabana, M. Côté, R. Martel, under revision (2014)

[2] D. Bouilly, J. Cabana, R. Martel. Appl. Phys. Lett. 101, 053116 (2012)
(Invited) Post-Growth Manipulation of Horizontally Aligned Single-Walled Carbon Nanotubes
Authors: Maruyama Shigeo , Inoue Taiki , Otsuka Keigo , Chiashi Shohei
Published: February 2020

Horizontally aligned single-walled carbon nanotubes (SWNTs) are promising for electronic applications such as field-effect transistors (FETs). In addition to the density-controlled CVD growth [1,2] and chirality characterization of aligned SWNTs on quartz substrates, we will discuss two manipulation techniques of SWNT arrays. First is the full-length removal of metallic SWNTs by using organic film-assisted electrical breakdown, which gives semiconducting SWNT arrays suitable for scalable device fabrication [3]. We applied the electrical breakdown technique to SWNT array covered with organic films such as poly(methyl methacrylate) (PMMA) and realized that metallic nanotubes continues to burn as fuses for fireworks. This method yielded not only a high on/off ratio (~10,000) and fine spatial resolution (~55 nm) in the same way as in-air breakdown, but also long removal length (>10 µm) which is unattainable by conventional breakdown. Thermal calculations revealed that burned edges of a SWNT keep high temperature with oxidation heat generation of surrounding organic materials even after Joule heat stops. The second manipulation technique is the bundling of selected parts of SWNT arrays. Horizontally aligned SWNTs were peeled off from original substrates by using polymer films with lithographically-defined resist structures. Then, the resist was dissolved to give partially suspended SWNTs over trenched polymer films, and neighboring suspended SWNTs formed bundles by capillary process. Finally the structures were placed on target substrates to give partially bundled SWNTs. This technique would be available for controlling percolative transport of SWNT networks.

Reference:

[1] S. Chiashi, H. Okabe, T. Inoue, J. Shiomi, T. Sato, S. Kono, M. Terasawa, S. Maruyama, J. Phys. Chem. C, 116 (2012) 6805.

[2] T. Inoue, D. Hasegawa, S. Badar, S. Aikawa, S. Chiashi, S. Maruyama, J. Phys. Chem. C, 117 (2013) 11804.

[3] K. Otsuka, T. Inoue, S. Chiashi and S. Maruyama, Nanoscale, 6 (2014) 8831.
(Invited) Flexible and Conductive Mxene/Carbon Nanotube Composite Paper for Energy Storage
Authors: Zhao Mengqiang , Ren Chang E. , Ling Zheng , Lukatskaya Maria R. , Mashtalir Olha , Barsoum Michel W. , Gogotsi Yury
Published: February 2020

Carbon nanomaterials, such as carbon nanotubes (CNTs), are attracting much attention as candidates for electrodes of energy storage devices due to their large open surfaces and high conductivity. Recently, MXenes, a new family of 2D carbides, have shown their great promise for electrodes in supercapacitors and Li-ion batteries. [1, 2] Herein, our new results show that the incorporation of CNTs into MXene films results in composite papers with much improved performance. [3]

Free-standing sandwich-like MXene/CNT composite papers composed of alternating layers of MXene and CNTs were fabricated by vacuum filtration method. The resulting “papers” have good flexibility, high electrical conductivity and a structure accessible to electrolyte ions. They exhibit much better performance than pure MXene films and the randomly mixed MXene/CNT composite papers. When employed as electrodes for supercapacitors in aqueous electrolyte, capacitances of ~390 F/cm3 were achieved. Besides, the composites showed ~75% increase in rate performance compared to pure MXene films and exhibited no capacity degradation after 10,000 cycles. The MXene/CNT composite papers can also serve as stable anodes for high-rate Li-ion batteries. Highly reversible and stable capacity of ~250 mAh/g was yielded by the titanium-based MXene/CNT composites at 0.5 C (2 hrs charge/discharge), about 10 times of that for pure MXene films. The niobium-based MXene/CNT composites achieved a high reversible capacity of ~650 mAh/g at 0.1 C (10 hrs charge/discharge). At 10 C (6 min charge/discharge), a reversible capacity of ~300 mAh/g was retained for >300 cycles, indicating excellent rate performance and cycling stability. These conductive, flexible and mechnaically strong papers are promising materials that can be used in wearable or structural electrochemical energy storage and conversion systems.

[1] M. Naguib, et al., MXenes: A New Family of Two-Dimensional Materials, Advanced Materials, 26, 992-1005 (2014)

[2] M. R. Lukatskaya, et al., Cation Intercalation and High Volumetric Capacitance of Two-dimensional Titanium Carbide, Science, 341, 1502-1505 (2013)

[3] M. Q. Zhao, et al. Flexible MXene/Carbon Nanotube Composite Paper with High Volumetric Capacitance, Advanced Materials, in press (2014)
Tayloring of Reduction Potential of Carbon Nanotubes Hybrid Compound By Substrate Interaction Probed By Metal Deposition
Authors: Macedo Nadia Guerra , Matsubara Elaine Yoshiko , Rosolen Jose Mauricio
Published: February 2020

The  determination  or  alteration of oxi-reduction  potentials and Fermi level (EF) of single-walled carbon nanotubes is a relevant issue in the science of carbon nanotubes (CNTs) because many of the envisaged applications may involve charge transfer. So far, it is well known that redox  potential  and  EF of single-walled carbon nanotubes are correlated to inverse of diameter and chiral angle. The reduction potential or the conduction band bottom energy of SWCNTs is in the range of 3.7 to 4.7 V vs. vacuum1,2. Nevertheless, in many electrochemical devices the CNTs is found on surface of other materials as oxides, carbons, metals, for instance. CNTs can also be directly grown on surface of several micrometric granules, fiber, thin films resulting, indeed, in hybrid compounds whose physical-chemical properties appears often correlated with amount and/or eventual electronic interaction of constituents. Herein, we investigate the eventual influence of a micrometric substrate on reduction potential of CNTs grown on its surface. Particularly, several carbonaceous materials and TiO2 were studied and the CNTs were vertically grown on surface of these micrometric substrates by chemical vapor deposition using the same CNTs growth protocol. In order to access the reduction potential of CNTs, the CNT/micrometric compounds were dipped into solutions of Ag, Cu, Al, Pd salts. The CNTs extracted from substrate by mechanical treatment were also dipped in same solutions. Afterwards, the obtained samples were analyzed in scanning electron microscopy, EDS and XPS after washed in deionized water. Interestingly the presence of metal nanoparticles was detected only in some types of CNT/micrometric substrate compounds. The mechanism of reduction of metals on surface of CNTs seems to be correlated with the participation of counter ions or presence of acids which can functionalize the surface of CNTs with COOH, COH, C=O groups. However, the main finding was the detection of an electronic coupling between CNT network-substrate which can modify the reduction potential of CNTs bear on its surface. Therefore, the CNTs growth on a micrometric substrate can lead to production of hierarchical hybrid compounds with unique redox potential.

[1] Hirana, Y. et al. Empirical Prediction of Electronic Potentials of Single-Walled Carbon Nanotubes With a Specific Chirality (n,m). Sci. Rep. 3, 2959; (2013).

[2] Kim, K. Ki et al.Doping strategy of carbon nanotubes with redox chemistry. New J.Chem.34, 2183; (2010).
Ultracompressible, High Rate Supercapacitors from Graphene-Coated Carbon Nanotube Aerogels
Authors: Wilson Evan , Islam Mohammad F.
Published: February 2020

The advent of flexible and wearable electronics has led to significant investigation into electrochemical energy sources, in particular electrochemical capacitors (ECs), which can be reversibly deformed without significant loss of performance. There exists a wide array of electrode materials and designs for ECs that are capable of withstanding bending or stretching loads, however very few structures are capable of withstanding significant compressions without loss of properties or plastic deformation. Most successful designs incorporate pseudocapacitive materials like conducting polymers or metal oxides for structural stability, increasing energy but potentially hurting lifetime and capacitance stability of the cells. This work seeks to solve this problem by utilizing an ultracompressible graphene-coated carbon nanotube aerogel as an electrode that possesses a high capacitance and mechanically robust structure without the need for pseudocapacitive materials.

We have previously demonstrated the synthesis of an ultracompressible, superelastic aerogel by coating the struts and nodes of a single-walled carbon nanotube network1 with one- to few-layer graphene.2 These aerogels are capable of withstanding significant (>90%) compressive strain without plastic deformation over many cycles. In addition, they have a highly porous and conductive structure with very large specific surface area, properties which are ideal for supercapacitor applications.

In this talk, I will present fabrication and structural characterization of graphene-coated carbon nanotube aerogels, in addition to their electrochemical performance. The electrodes displayed near-ideal capacitive performance under high-rate operation with no loss of capacitance at 90% compression in both aqueous and room-temperature ionic liquid (RTIL) electrolytes. The transport properties of ions through the electrodes were unaffected by large compressive strains, allowing high-rate operation of cells with both uncompressed and compressed electrodes. Electrochemical impedance spectroscopy investigations confirm that the performance of the supercapacitor electrodes was largely strain-invariant. This performance, in cells with both uncompressed and compressed electrodes, was stable over hundreds of cycles. Moreover, the compression was exploited to construct cells with high volumetric capacitance of ~5 to 18 F/cm3 in aqueous and RTIL electrolytes respectively, nearly 50 times greater than comparable supercapacitor electrodes, while still allowing for rapid charging and discharging of the cells. This work was funded by the National Science Foundation through grants CBET-1335417 and DGE-0966227

References

1. K. H. Kim, Y. Oh and M. F. Islam, Advanced Functional Materials, 23, 377–383 (2012).

2. K. H. Kim, Y. Oh and M. F. Islam, Nature Nanotechnology, 7, 562–566 (2012).
(Invited) Electronic Scattering in One-Dimensional Carbon Nanotubes
Authors: Collins Philip G.
Published: February 2020

A quasi-ballistic, semi-metallic carbon nanotube is a nearly ideal conductor for investigating scattering in the one-dimensional (1D) limit and for comparing experiment with theoretical predictions.  Recently, we have developed high resolution Kelvin Probe force microscopy (KPFM) methods of characterizing transport in single nanotubes.  KPFM images of potential gradients uniquely reveal the bias- and temperature-dependent mechanisms of scattering in nanotube devices, and clearly discriminate between contact effects and homogenous, diffusive scattering.  Using this data, a comprehensive, quantitative model has been developed that includes intrinsic energy-relaxation processes, extrinsic interactions with the surrounding environment, and the effects of point defects.  The new results show that the literature grossly underestimates the mean free path for optical phonon emission.  Defect scattering follows a mechanism similar to Poole-Frenkel conduction but with modifications accounting for the 1D geometry.  The Poole-Frenkel mechanism, which normally applies to 2D interfaces, has never been observed in the limit of a single defect limit, and its application to point defect scattering in 1D is wholly unanticipated in the theoretical literature.  This presentation will summarize these findings and their implications for nanotube devices as sensors or digital electronics.
Dynamic and Steady State Optical Studies of Individual Covalent Dopant Sites in Single-Wall Carbon Nanotubes
Authors: Hartmann Nicolai F. , Yalcin Sibel E. , Haroz Erik H. , Ma Xuedan , Htoon Han , Doorn Stephen K.
Published: February 2020

Controlled low-level covalent functionalization of single-wall carbon nanotubes (SWCNTs) has refocused the attention of the nanophotonics community on the use of SWCNTs as stable photon sources in imaging applications. Recently, a significant increase in photoluminescence (PL) quantum yield from the appearance of new emitting states was reported in the literature upon introduction of chemically stable oxygen [1,2] and aryl diazonium dopants [3]. Further insight into the chemical and electronic structure of oxygen trap sites was gained through low-temperature studies [4],however additional fundamental knowledge about the optical and chemical properties of these dopant sites is necessary in order to develop more efficient emitter and light harvesting systems based on SWCNTs.

We doped single-chirality-enriched (6,5) and (5,4) SWCNTs with a broad range of available covalent dopants and studied their steady-state and dynamic optical properties on the ensemble and single-tube level. Our refinement of the reported doping procedure described in the literature [1-3] enables the control of the doping level and type of dopant down to the introduction of individual dopant sites in a short timescale. Dual color imaging of 2 – 6 μm long SWCNTs reveals the red-shifted individual dopant emission E11* alongside the pristine E11 emission. Average ON times of single sites decrease with increasing electron withdrawing nature of the specific dopant groups as well as with an increase in pH of the surrounding medium which can be understood in terms of additional non radiative decay channels introduced through surface charging. In addition, we will present single tube lifetime measurements on covalently doped (5,4) SWCNTs for a variety of diazonium dopants. The brightening in dopant emission intensity is correlated with longer PL lifetimes and increases with the electron withdrawing strength of the associated functional groups.

[1]  S. Ghosh, et al., Science, 2010,
330, 1656.

[2]  Y. Miyauchi, et al., Nature Photon., 2013, 7, 715.

[3]  Y. Piao, et al., Nature Chem., 2013, 5, 840.

[4]  X. Ma, et al., ACS Nano, 2014, 8, 10782.
A Study on Correlation Between Elastic Deformation and Thermal Performance of Flexible Carbon Heater
Authors: Hong Young Kyu , Kim Byung-Ryang , Hong Chan Ho , Park Hyeon Ki , Shin Jin-Koog
Published: February 2020

Printed carbon heater is one of most attractive alternatives to copper wire seat heater because of its uniform heat generation and trouble-free operation regardless of partial damage. Its superior characteristics such as low power consumption and rapid response induced a lot of research on carbon materials and its thermal performance. However, in contrast to the commercialization potential, application field related researches are not active yet. To apply a printed heater in a car seat, suitable elasticity is required without loss of thermal performance. Therefore, it needs to study on the correlation between deformation and electrical and structural characteristics.

In this study, we investigated relationship between elastic deformation and characteristics of carbon heater. Carbon heaters used in this study were screen printed on flexible polymer substrates of different elastic modulus. The carbon paste used to print the heater was made of graphite and amide functionalized MwCNT blended with polyester resin. The change of microstructure, electrical characteristics, and adhesion stability were analyzed in connection with the heater performance while increasing the deformation up to the elastic limit. Based on the analysis, we will discuss on critical factors determining the performance of flexible carbon heater under elastic deformation.

This research was financially supported by the Ministry of Trade, Industry and Energy (MOTIE) and Korea Institute for Advancement of Technology (KIAT) through the Promoting Regional Specialized Industry
(Invited) Promise of 2D Materials Beyond Graphene
Authors: Saptarshi Das
Published: February 2020

Two dimensional systems, by the virtue of their unique material properties and excellent electrostatic integrity, provide immense opportunities not only to explore fundamental physics but also to solve critical technological problems. Graphene, Phosphorene, h-BN, MoS2, WSe2 and many others belong to this class of material which we are exploring. The fact that this class of materials contains metals, semiconductors, insulators and even superconductors at cryogenic temperature makes them extremely appealing across all scientific and engineering disciplines. In my talk I will demonstrate how “Contact Engineering” can be implemented to enhance the electrical performance of the 2D materials. Then I will talk about “Doping Constraints” and various “Scaling Aspects” of 2D materials. Finally I will discuss “Integration and Application” of 2D materials for flexible and transparent electronics as well as low power device design.

References:

Das, S. et al.

ACS Nano, 8 (11), 2014.

Das, S. et al.

Nano Letters, 14 (10), 2014.

Das, S. et al.

Applied Physics Letters, 105, 2014. 

Das, S. et al.

Nano Letters, 14 (5), 2014.

Das, S. et al.

ACS Nano, 8 (2), 2014.

Das, S. et al.

Applied Physics Letters
, 103, 2013.

Das, S. et al.

Nano Letters, 13(7), 2013. 

Das, S. et al.

Physica Status Solidi RRL,
7(4), 2013. 

Das, S. et al.

Nano Letters
, 13(1), 2013
.
Facile and Controllable Synthesis of Heteroatom-Doped Carbon Nanotubes Under Atmospheric Pressure
Authors: Chang Yu-Chen , Chen Guan-Lin , Chiang Wei-Hung
Published: February 2020

Recent theoretical and experimental studies have suggested that heteroatom-doped carbon nanomaterials such as carbon nanotubes (CNTs) and graphenes as novel materials with exceptional properties for applications including nanoelectronics, energy storage [1], fuel cells [2], and electrochemical sensing [3]. However, current synthesis methods of heteroatom-doped carbon nanomaterials usually involve complicated vacuum systems, making it difficult to enable industrial-scale production. Consequently, the development of a controllable synthesis of heteroatom-doped carbon nanomaterials at atmospheric pressure will lead to important advances on both scientific studies and innovation applications.

Here we demonstrate an atmospheric-pressure, solution-assisted substitution method to produce heteroatom-doped CNTs with varying heteroatoms including boron (B), sulfur (S), and phosphorus (P).  Pristine multi-walled CNTs (MWCNTs) synthesized using a water-assisted chemical vapor deposition (CVD) were used as starting materials. The heteroatom-doped CNTs were then produced by heating the mixture of heteroatom precursor and MWCNTs under argon (Ar) atmosphere from 400 to 1200◦C for 1to 4 h at atmospheric pressure. We found that the heteroatom concentrations in the nanotubes could be tuned by controlling the reaction temperature and time, confirming by the X-ray photoelectron spectroscopy (XPS) and Raman characterizations. Detailed XPS characterization indicated that the S atoms were successfully doped into the sp2 graphene lattice of CNTs [Fig. 1(a)]. The high-resolution XPS (XPS) result reveals several C-S-O doping configurations existed in our as-produced samples [Fig. 1(b)]. The systematic Raman characterization was performed and shown the ratio of the D- and the G- bands (ID/IG) was increased for the as-produced samples, indicating the defect densities due to the doping process can be controlled in our method [Fig. 1(c)]. Thin-film electrical conductance characterization using four-point probe method suggested the electrical conductances of the as-prepared heteroatom-doped CNTs were significantly improved by heteroatom doping [Fig. 1(d)], making them useful materials for electrochemical-base applications. It is also noteworthy from a practical point of view that the developed atmospheric-pressure synthesis method is amenable to industrial-scale production since it avoids the need for a vacuum system.

Reference

[1] J. Han, L.L. Zhang, S. Lee, J. Oh, K.-S. Lee, J.R. Potts, J. Ji, X. Zhao, R.S. Ruoff, S. Park, ACS nano, 7 (2012) 19-26.

[2] L. Qu, Y. Liu, J.-B. Baek, L. Dai, ACS Nano, 4 (2010) 1321-1326.

[3] Y. Wang, Y. Shao, D.W. Matson, J. Li, Y. Lin, ACS nano, 4 (2010) 1790-1798.

[4] H. Liu, Y. Liu, D. Zhu, Journal of Materials Chemistry, 21 (2011) 3335-3345.

Figure 1
Photo-Induced Effects in Graphene Channels When Interfaced with Quantum Dot Array
Authors: Miao Xin , Samarth Trivedi , Grebel Haim
Published: February 2020

Field effect transistors with graphene channels were interfaced with semiconductor quantum dot (QD) array.  Electrical characteristics and opto-electronic behaviour of the elements were assessed.  Relative photo-resistance (the difference in channel resistances under dark and under light conditions and normalized by the channel’s resistance) was observed as a function of drain-source potential.

Graphene – a mono layer thick crystalline form of carbon - portrays high conductivity, chemical inertness, mechanical robustness and unusual dispersion relations [1].  Characteristics of free-standing, mono and bi-layer graphene have been studied when deposited over nano-pore array of anodized aluminum oxide (AAO) substrate.  One may postulate that QDs, filling the pores, will have a profound effect on the graphene channel.  Such arrangement led to the realization of the first visible surface plasmon laser [2]. 

The field effect transistors (FET) were fabricated on oxidized silicon wafers.  They were composed of graphene channels and two metal electrodes, used as drain and source electrodes.  The silicon wafer served as a back gate electrode.  Contacts to the graphene were found Ohmic.  Aluminum, was deposited on the oxidized silicon wafer and was anodized according to our previous recipe.  Core-shell semiconductor CdSe/ZnS QDs were imbedded in the anodized aluminum pores and the semi-transparent graphene was deposited on top of the anodized layer.

Unlike ordinary graphene channels, the current between the drain and source, Ids, decreased as a function of gate bias, Vgs.  When illuminated by a 50 mW/cm2 white light source, the channel exhibited a clear relative differential resistance at Vds=0.3 V.  This behavior was attributed to a negative differential resistance effect. 

[1] A. C. Ferrari, J. C. Meyer, V. Scardaci, M. Lazzeri, F. Mauri, S. Piscance, D. Jiang, K. S. Novoselov, S. Roth and A. K. Geim, “Raman Spectrum of Graphene and Graphene Layers”, Phys. Rev. Lett., 97, 187401 (2006).

[2] R. Li, A. Banerjee and H. Grebel, “The possibility for surface plasmon lasers”, Optics Express, 17, 1622-1627 (2009).

[3] S. W. Lee, A. Kornblit, D. Lopez, S. V. Rotkin. A. Sirenko, H. Grebel, “Negative Differential Resistance: Gate Controlled and Photoconductance Enhancement in Carbon Nanotube Intra-connects”, Nano Letters, DOI: 10.1021/nl803036a (2009).
Controllable Synthesis of Metal Nanoparticle/Graphene Nanoribbon Composites
Authors: Wang Shan-Yu , Chiang Wei-Hung
Published: February 2020

Graphene nanoribbons (GNRs) represent a new structure of carbon nanomaterials which have exceptional physical and chemical properties, making them can be potentially used in the applications of energy, composites, biomedical and electronics [1-3]. Recently composites of metal nanoparticles (NPs) decorated on GNR surfaces has been reported as novel materials with exceptional properties and can be used for industrial applications [4, 5]. For example, Pt/GNRs and Pd/GNRs using as catalysts for fuel cells, and Ag/GNRs can be used for conductive ink or biomedical applications. Consequently, the development of synthetic method to produce metal NPs/GNR composites will lead to important advances on both fundamental study and innovative applications.

Here we report a controllable synthesis of Ag/GNR composites using a two-step reaction route. First, we synthesized and functionalized GNRs by a facile carbon nanotube chemical unzipping. The functionalization of GNRs could be tuned by controlling reaction conditions (temperature, time, and oxidant concentration), confirming by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XP)S characterizations (Fig. 1 and 2). Ag NPs can be decorated onto the GNR surface through a wet- chemical-based redox reaction. In our present experiment, we found that the particle size, morphology and distribution of Ag NPs can be further controlled by controlling the reaction conditions. Detailed materials characterizations including SEM and UV-Vis spectroscopy (Fig. 3) show that Ag/GNR composites were successfully synthesized in our experiment.

Reference

[1] L. Ma, J. Wang, and F. Ding, "Recent progress and challenges in graphene nanoribbon synthesis," Chemphyschem, vol. 14, pp. 47-54, Jan 14 2013.

[2] D. V. Kosynkin, A. L. Higginbotham, A. Sinitskii, J. R. Lomeda, A. Dimiev, B. K. Price, et al., "Longitudinal unzipping of carbon nanotubes to form graphene nanoribbons," Nature, vol. 458, pp. 872-6, Apr 16 2009.

[3] A. L. Higginbotham, D. V. Kosynkin, A. Sinitskii, Z. Sun, and J. M. Tour, "Lower-defect graphene oxide nanoribbons from multiwalled carbon nanotubes," ACS nano, vol. 4, pp. 2059-2069, 2010.

[4] P. T. Yin, T.-H. Kim, J.-W. Choi, and K.-B. Lee, "Prospects for graphene–nanoparticle-based hybrid sensors," Physical Chemistry Chemical Physics, vol. 15, pp. 12785-12799, 2013.

[5] L. Xu, G. Yang, H. Jing, J. Wei, and Y. Han, "Ag–graphene hybrid conductive ink for writing electronics," Nanotechnology, vol. 25, p. 055201, 2014.

Figure 1
Electrical Properties of Controlled, Longitudinal Wrinkles on Graphene Produced Via Bacterial-Scaffold Shrinkage
Authors: Deng Shikai , Sreeprasad Theruvakkattil Sreenivasan , Berry Vikas
Published: February 2020

Wrinkles directly influence the electronic structure of graphene and thus its optical and chemical properties due to local p-orbital stretching, dipolar doping, and/or carrier puddling. Here, we show that bacteria’s ambiphilic cellwall chemistry (and texture), high surface energy, and transportable aqueous content with shrinkable microstructure makes them great scaffolds to induce controlled and confined wrinkles on interfaced graphene sheets. The relaxation of pre-stretched bacterial cell results in graphene wrinkles to orient in the longitudinal direction to the strepto-bacillus cereus cells with a texture aspect-ratio of 0.125. The wrinkle-wavelength is independent of the size of bacteria and the calculated wrinkle-wavelength of 32.5 nm is consistent with the observed wavelength of 32.4 nm – 34.3 nm. Under vacuum, bacterium covered with graphene dehydrates and shrinks; however, does not rehydrate at atmospheric pressure (like uncovered bacteria). This talk will (a) demonstrate directed electrophoresis of bacterial cells between electrodes for position-controlled 2D-wrinkle placement, and (b) discuss the electron density distribution and transport properties through wrinkled graphene. These graphenic bio-interfaced wrinkles can lead to novel nano/bio microelectromechanical systems with applications in electrical cell actuation, dehydration, sensing, restraining, retention, electro-microfluidics, and controlled delivery.
Aerogels: Graphene and Beyond
Authors: Worsley Marcus A.
Published: February 2020

Aerogels are porous solids used in a wide range of applications including sorbents, filtration, insulation, hydrogen storage, catalysis, batteries, and supercapacitors. Their unique properties are related to their high internal surface, low-density, and small pore/particle size.  Two-dimensional (2D) nanomaterials, such as boron nitride and graphene, also exhibit a range of distinct optical, electronic, and mechanical properties, but are typically limited to thin films and coatings.  Assembling 2D nanomaterials into monolithic aerogels expands their application space to include technologies and manufacturing processes that require a macroscopic 3D form factor.  Furthermore, placing the novel intrinsic properties of 2D materials in a low-density, high surface area architecture has the potential to unlock exciting new properties and features only displayed in the aerogel system.  Here, we present synthesis schemes for aerogels made from several different 2D materials, (e.g. boron nitride, graphene, dichalcogenides, etc.). Hybrid aerogel synthesis, combining two or more layered materials, will also be presented.  Characterization of aerogels will include textural, transport, mechanical properties, and more.  Results will be discussed in light of theory and existing literature.

This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
Biomimetic Selective Ion Transport through Graphene Oxide Membranes Functionalized with Ion Recognizable Peptides
Authors: Nham Jeasun , Kim Sunho , Jeong Yo Sub , Ha Sung Hoon , Lee Chang Sun , Lee Yun Jung
Published: February 2020

Membranes that differentiate ions are being actively developed to meet the needs in separation, sensing, biomedical and water treatment technologies. Biomimetic approaches that combine bio-inspired functional molecules with solid state supports offer a great potential of imitating the functions and principles of biological ion channels. Here we report the design and fabrication of biomimetic graphene oxide (GO) based membranes functionalized by a peptide motif with ion recognizable capability for selective ion transport. The peptide with selective ion binding affinity is adopted as an ion selective filter and anchored on GO surface. The resulting GO based membranes show remarkable ion selectivity toward the specific ion of interest for the transport across the membranes as in the biological ion channels. Ion recognition capability of a peptide motif successfully translates into ion specificity for selective transport. This study provides a new avenue for developing artificial ion channels by synergistic combination of biomimetic recognition chemistry with a novel nanoplatform such as GO.

Figure 1
The Effect of Surface Energy on Atomic Layer Deposited Al2O3 Dielectric on MoS2 crystals
Authors: Park Seonyoung , Lee Hyuna , Choi Yura , Choi Woong
Published: February 2020

Molybdenum disulfide (MoS2) is a promising two-dimensional semiconductor for thin-film transistors (TFTs) because of the high field-effect mobility, low subthreshold swing, and high on/off ratio. For the fabrication of high-performance MoS2 TFTs, it is essential to integrate a high dielectric constant (high-k) gate insulator such as HfO2 or Al2O3 on MoS2. However, the absence of dangling bonds or functional groups on MoS2 basal plane often requires the pretreatment of MoS2 surface by O2 plasma or ultraviolet (UV)-O3, which will inevitably influence the surface energy. In this presentation, we report a systematic investigation on the effect of MoS2 surface energy on the atomic layer deposited (ALD) Al2O3. We correlate the surface coverage and morphology of ALD Al2O3 dielectric with the MoS2 surface energy based on the measurement with scanning electron microscopy (SEM), atomic force microscopy (AFM), x-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. We also provide electrical properties of functionalized Al2O3/MoS2 interface with current-voltage (I-V) and capacitance-voltage (C-V) characteristics.
An Electrochemical Analogy to the Fuel Injector: The Electrochemical Direct Injection Reactor
Authors: Davies Greg , Hsieh Andrew , Steingart Daniel A
Published: February 2020

ElectroChemical Direct Injection (ECDI) is a newly proposed battery architecture. ECDI involves the direct injection of small quantities of cathode and anode materials into a reactor, where they are rapidly discharged, then flushed out. The process repeats, and much like a standard combustion engine, the quantity of fuel injected, in addition to the rate of discharge, can be tailored to meet the power demand in an efficient way. We investigate some of the most interesting electrochemical and mechanical features of the system, and present some key results illustrating the promise of such an approach. Results from the discharge rate performance and energy efficiency of the system are presented, to highlight the benefits of this architecture.

From an electrochemical perspective, using a high-surface area, nano-structured zinc [1], we demonstrate that high discharge utilization efficiencies (% of theoretical capacity) are possible in this free standing system. At 3C rates of discharge, efficiencies of up to 80% are achievable with this zinc morphology. Even at rates up to 30C, efficiencies are up to 50% are still achievable. The system can be improved through optimization of the electrolyte, and with various additives. The benefits of electrolyte optimization and additives will be discussed, including a mechanistic study of the additives.
High Surface Area Multi-Wall Carbon Nanotube Electrodes for H2-Br2 fuel Cells
Authors: Yarlagadda Venkata , Nguyen Trung Van
Published: February 2020

The regenerative H2-Br2 fuel cell has been a subject of great interest and is considered as one of the great candidates for large scale electrical energy storage [1, 2]. Since the bromine reactions in this fuel cell system do not need any precious metal catalysts, plain porous carbon paper can be used as an electrode material. However, these porous carbon electrodes have low surface area and hence multiple electrode layers are employed to improve the active surface area [2]. In our previous study, we used a two-step synthesis process that involves electrodeposition of catalyst nanoparticles followed by chemical vapor deposition (CVD) of carbon nanotubes [3]. Scanning electron micrographs of the materials obtained by this process are shown in Figure 1. As a way to simplify the process and reduce the cost of the produced material, a single step process is explored. In this process the catalyst nanoparticles are deposited on the carbon electrode via thermal reduction in a hydrogen environment and subsequently carbon nanotubes are grown. The whole process is accomplished in a single step. This new process, its effectiveness, and the performance of the materials created by this new process will be discussed in this presentation.

References

Haley Kreutzer, Venkata Yarlagadda, and Trung Van Nguyen, J. Electrochem Soc., 159(7), F331 (2012).

Kyu Taek Cho, Paul Ridgeway, Adam Z. Weber, Sophia Haussener, Vincent Battagalia, and Venkat Srinivasan, J. Electrochem. Soc., 159(11), A1806 (2012).

Venkata Yarlagadda and Trung Nguyen, ECS Transactions, 58(36), 25 (2014).

Acknowledgements

This work was funded by NSF through grant number EFRI-1038234 and DOE/ARPA-E under award number DE-AR000026.

Figure 1
Cost-Effective All-Copper Flow Battery Using Flowable Slurry Electrode for Large-Scale Energy Storage
Authors: Agar Ertan , Nagelli Enoch A. , Sinclair Nicholas S. , Hoyt Nathaniel C. , Stricker Elizabeth A. , Savinell Robert F , Wainright Jesse S.
Published: February 2020

One major issue limiting the implementation of renewable energy sources is the lack of efficient, cost-effective, and reliable energy storage technologies. Recently, vanadium redox flow batteries (VRFBs) have gained a significant interest as a promising electrochemical technology for large-scale energy storage due to their ability to decouple energy and power ratings and to store energy efficiently [1]. However, the high capital cost of vanadium-based electrolyte represents a major bottleneck for the commercialization of these systems [2]. By this motivation, in this study, a novel all-copper flow battery (CFB) using flowable slurry electrode is introduced. 

CFBs have a great potential for commercialization, as copper is a less toxic, widely abundant, and less expensive element than vanadium [3]. Moreover, its relatively smaller cell potential eliminates hydrogen evolution as a side reaction. However, electrochemical-plating of copper within the negative electrode during charging recouples energy and power ratings, which limits the widespread implementation of these systems. In order to mitigate this issue, a flowable slurry electrode strategy is implemented for the negative half-cell instead of using a conventional, stationary electrode [4-5]. A schematic of an all-copper flow battery using a flowable slurry electrode for the negative half-cell is shown in Fig. 1. The slurry electrode carries the deposited metal out of the stack to the reservoir, allowing the energy and power capabilities of the battery to be scaled independently.

This study is investigating the performance of a CFB using a flowable slurry electrode with a novel copper-bromide chemistry by conducting polarization curve (Fig. 2), battery cycling and efficiency analyses. As seen in Fig. 2, with the copper-bromide electrolyte and flowable slurry electrode strategy, much higher operating current densities (maximum power density of ~85 mW/cm2 obtained at 200 mA/cm2) have been reached compared to literature values for an all-copper flow battery. This indicates that the slurry electrode cannot only de-couple the energy and power ratings, but can also provide an acceptable level of polarization losses.

References:

[1] A. Z. Weber, M. M. Mench, J. P. Meyers, P. N. Ross, J. T. Gostick, Q. Liu, J. Appl. Electrochem., 41, 1137-1164 (2011).

[2] R. M. Darling, K. G. Galagher, J. A. Kowalsky, S. Ha, F. R. Brushett, Energy Environ. Sci., 7, 3459-3477 (2014).

[3] L. Sanz, D. Lloyd, E. Magdalena, J. Palma, K. Kontturi, J. Power Sources, 268, 121-128 (2014).

[4] T. Petek, N. C. Hoyt, J. S Wainright, R. F. Savinell, Submitted to J. Power Sources, March (2015).

[5] T. Petek, N. C. Hoyt, J. S Wainright, R. F. Savinell, Submitted to J. Electrochem. Soc., March (2015).

[5] T. Petek, N. C. Hoyt, J. S Wainright, R. F. Savinell, Submitted to J. Electrochem. Soc., March (2015).

Figure 1
Cost Effective Electrochemical Energy Storage Today and Tomorrow: Promising Pathways to $100 per k Wh
Authors: Gallagher Kevin G. , Crabtree George
Published: February 2020

Cost effective electrochemical energy storage is the key to unlocking the future potential of zero emission automobiles and a stable electricity grid that utilizes large fractions of inherently variable renewable sources of power.  Lithium-ion battery costs are continuing on a downward trajectory that has enabled automakers around the world to produce battery electric vehicles and sell them at moderate to high prices. The steeply declining cost curve has also enabled this technology to spill-over into early, high-value segments of energy storage on the electricity grid. As the push-pull between technology and marketplace continues, lithium-ion and other established battery chemistries will fight for dominance with gasoline fueled vehicles in transportation and with inexpensive and efficient combined cycle gas turbines in large scale grid storage applications. Concurrently, scientists and engineers around the world are racing to build cheaper, longer-lived, more energy dense batteries based on new chemistries. These promising new beyond lithium ion storage technologies with higher performance and lower costs are seen as necessary to enable a true renaissance in the way society utilizes electricity. Cost structures for historical and projected battery technologies will be presented. Pathways to achieve a battery level price of $100/kWh will be shown in terms of materials level performance and cost targets to guide researchers and policy makers.